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Message-Id: <1446906642-19372-4-git-send-email-sandyinchina@gmail.com>
Date: Sat, 7 Nov 2015 09:30:39 -0500
From: Sandy Harris <sandyinchina@...il.com>
To: "Theodore Ts\\'o" <tytso@....edu>,
Jason Cooper <jason@...edaemon.net>,
"H. Peter Anvin" <hpa@...or.com>, John Denker <jsd@...n.com>
Cc: linux-kernel@...r.kernel.org, linux-crypto@...r.kernel.org
Subject: [PATCH 4/7] Different version of driver using hash from AES-GCM Compiled if CONFIG_RANDOM_GCM=y
Signed-off-by: Sandy Harris <sandyinchina@...il.com>
---
drivers/char/random_gcm.c | 3716 +++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 3716 insertions(+)
create mode 100644 drivers/char/random_gcm.c
diff --git a/drivers/char/random_gcm.c b/drivers/char/random_gcm.c
new file mode 100644
index 0000000..360fbe3
--- /dev/null
+++ b/drivers/char/random_gcm.c
@@ -0,0 +1,3716 @@
+/*
+ * random.c -- A strong random number generator
+ *
+ * Copyright Matt Mackall <mpm@...enic.com>, 2003, 2004, 2005
+ *
+ * Copyright Theodore Ts'o, 1994, 1995, 1996, 1997, 1998, 1999. All
+ * rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ * notice, and the entire permission notice in its entirety,
+ * including the disclaimer of warranties.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution.
+ * 3. The name of the author may not be used to endorse or promote
+ * products derived from this software without specific prior
+ * written permission.
+ *
+ * ALTERNATIVELY, this product may be distributed under the terms of
+ * the GNU General Public License, in which case the provisions of the GPL are
+ * required INSTEAD OF the above restrictions. (This clause is
+ * necessary due to a potential bad interaction between the GPL and
+ * the restrictions contained in a BSD-style copyright.)
+ *
+ * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
+ * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, ALL OF
+ * WHICH ARE HEREBY DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
+ * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
+ * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+ * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
+ * USE OF THIS SOFTWARE, EVEN IF NOT ADVISED OF THE POSSIBILITY OF SUCH
+ * DAMAGE.
+ */
+
+/*
+ * (now, with legal B.S. out of the way.....)
+ *
+ * This routine gathers environmental noise from device drivers, etc.,
+ * and returns good random numbers, suitable for cryptographic use.
+ * Besides the obvious cryptographic uses, these numbers are also good
+ * for seeding TCP sequence numbers, and other places where it is
+ * desirable to have numbers which are not only random, but hard to
+ * predict by an attacker.
+ *
+ * Theory of operation
+ * ===================
+ *
+ * Computers are very predictable devices. Hence it is extremely hard
+ * to produce truly random numbers on a computer --- as opposed to
+ * pseudo-random numbers, which can easily generated by using a
+ * algorithm. Unfortunately, it is very easy for attackers to guess
+ * the sequence of pseudo-random number generators, and for some
+ * applications this is not acceptable. So instead, we must try to
+ * gather "environmental noise" from the computer's environment, which
+ * must be hard for outside attackers to observe, and use that to
+ * generate random numbers. In a Unix environment, this is best done
+ * from inside the kernel.
+ *
+ * Sources of randomness from the environment include inter-keyboard
+ * timings, inter-interrupt timings from some interrupts, and other
+ * events which are both (a) non-deterministic and (b) hard for an
+ * outside observer to measure. Randomness from these sources are
+ * added to an "entropy pool", which is mixed using a CRC-like function.
+ * This is not cryptographically strong, but it is adequate assuming
+ * the randomness is not chosen maliciously, and it is fast enough that
+ * the overhead of doing it on every interrupt is very reasonable.
+ * As random bytes are mixed into the entropy pool, the routines keep
+ * an *estimate* of how many bits of randomness have been stored into
+ * the random number generator's internal state.
+ *
+ * When random bytes are desired, they are obtained by taking the SHA
+ * hash of the contents of the "entropy pool". The SHA hash avoids
+ * exposing the internal state of the entropy pool. It is believed to
+ * be computationally infeasible to derive any useful information
+ * about the input of SHA from its output. Even if it is possible to
+ * analyze SHA in some clever way, as long as the amount of data
+ * returned from the generator is less than the inherent entropy in
+ * the pool, the output data is totally unpredictable. For this
+ * reason, the routine decreases its internal estimate of how many
+ * bits of "true randomness" are contained in the entropy pool as it
+ * outputs random numbers.
+ *
+ * If this estimate goes to zero, the routine can still generate
+ * random numbers; however, an attacker may (at least in theory) be
+ * able to infer the future output of the generator from prior
+ * outputs. This requires successful cryptanalysis of SHA, which is
+ * not believed to be feasible, but there is a remote possibility.
+ * Nonetheless, these numbers should be useful for the vast majority
+ * of purposes.
+ *
+ * Exported interfaces ---- output
+ * ===============================
+ *
+ * There are three exported interfaces; the first is one designed to
+ * be used from within the kernel:
+ *
+ * void get_random_bytes(void *buf, int nbytes);
+ *
+ * This interface will return the requested number of random bytes,
+ * and place it in the requested buffer.
+ *
+ * The two other interfaces are two character devices /dev/random and
+ * /dev/urandom. /dev/random is suitable for use when very high
+ * quality randomness is desired (for example, for key generation or
+ * one-time pads), as it will only return a maximum of the number of
+ * bits of randomness (as estimated by the random number generator)
+ * contained in the entropy pool.
+ *
+ * The /dev/urandom device does not have this limit, and will return
+ * as many bytes as are requested. As more and more random bytes are
+ * requested without giving time for the entropy pool to recharge,
+ * this will result in random numbers that are merely cryptographically
+ * strong. For many applications, however, this is acceptable.
+ *
+ * Exported interfaces ---- input
+ * ==============================
+ *
+ * The current exported interfaces for gathering environmental noise
+ * from the devices are:
+ *
+ * void add_device_randomness(const void *buf, unsigned int size);
+ * void add_input_randomness(unsigned int type, unsigned int code,
+ * unsigned int value);
+ * void add_interrupt_randomness(int irq, int irq_flags);
+ * void add_disk_randomness(struct gendisk *disk);
+ *
+ * add_device_randomness() is for adding data to the random pool that
+ * is likely to differ between two devices (or possibly even per boot).
+ * This would be things like MAC addresses or serial numbers, or the
+ * read-out of the RTC. This does *not* add any actual entropy to the
+ * pool, but it initializes the pool to different values for devices
+ * that might otherwise be identical and have very little entropy
+ * available to them (particularly common in the embedded world).
+ *
+ * add_input_randomness() uses the input layer interrupt timing, as well as
+ * the event type information from the hardware.
+ *
+ * add_interrupt_randomness() uses the interrupt timing as random
+ * inputs to the entropy pool. Using the cycle counters and the irq source
+ * as inputs, it feeds the randomness roughly once a second.
+ *
+ * add_disk_randomness() uses what amounts to the seek time of block
+ * layer request events, on a per-disk_devt basis, as input to the
+ * entropy pool. Note that high-speed solid state drives with very low
+ * seek times do not make for good sources of entropy, as their seek
+ * times are usually fairly consistent.
+ *
+ * All of these routines try to estimate how many bits of randomness a
+ * particular randomness source. They do this by keeping track of the
+ * first and second order deltas of the event timings.
+ *
+ * Ensuring unpredictability at system startup
+ * ============================================
+ *
+ * When any operating system starts up, it will go through a sequence
+ * of actions that are fairly predictable by an adversary, especially
+ * if the start-up does not involve interaction with a human operator.
+ * This reduces the actual number of bits of unpredictability in the
+ * entropy pool below the value in entropy_count. In order to
+ * counteract this effect, it helps to carry information in the
+ * entropy pool across shut-downs and start-ups. To do this, put the
+ * following lines an appropriate script which is run during the boot
+ * sequence:
+ *
+ * echo "Initializing random number generator..."
+ * random_seed=/var/run/random-seed
+ * # Carry a random seed from start-up to start-up
+ * # Load and then save the whole entropy pool
+ * if [ -f $random_seed ]; then
+ * cat $random_seed >/dev/urandom
+ * else
+ * touch $random_seed
+ * fi
+ * chmod 600 $random_seed
+ * dd if=/dev/urandom of=$random_seed count=1 bs=512
+ *
+ * and the following lines in an appropriate script which is run as
+ * the system is shutdown:
+ *
+ * # Carry a random seed from shut-down to start-up
+ * # Save the whole entropy pool
+ * echo "Saving random seed..."
+ * random_seed=/var/run/random-seed
+ * touch $random_seed
+ * chmod 600 $random_seed
+ * dd if=/dev/urandom of=$random_seed count=1 bs=512
+ *
+ * For example, on most modern systems using the System V init
+ * scripts, such code fragments would be found in
+ * /etc/rc.d/init.d/random. On older Linux systems, the correct script
+ * location might be in /etc/rcb.d/rc.local or /etc/rc.d/rc.0.
+ *
+ * Effectively, these commands cause the contents of the entropy pool
+ * to be saved at shut-down time and reloaded into the entropy pool at
+ * start-up. (The 'dd' in the addition to the bootup script is to
+ * make sure that /etc/random-seed is different for every start-up,
+ * even if the system crashes without executing rc.0.) Even with
+ * complete knowledge of the start-up activities, predicting the state
+ * of the entropy pool requires knowledge of the previous history of
+ * the system.
+ *
+ * Configuring the /dev/random driver under Linux
+ * ==============================================
+ *
+ * The /dev/random driver under Linux uses minor numbers 8 and 9 of
+ * the /dev/mem major number (#1). So if your system does not have
+ * /dev/random and /dev/urandom created already, they can be created
+ * by using the commands:
+ *
+ * mknod /dev/random c 1 8
+ * mknod /dev/urandom c 1 9
+ *
+ * Acknowledgements:
+ * =================
+ *
+ * Ideas for constructing this random number generator were derived
+ * from Pretty Good Privacy's random number generator, and from private
+ * discussions with Phil Karn. Colin Plumb provided a faster random
+ * number generator, which speed up the mixing function of the entropy
+ * pool, taken from PGPfone. Dale Worley has also contributed many
+ * useful ideas and suggestions to improve this driver.
+ *
+ * Any flaws in the design are solely my responsibility, and should
+ * not be attributed to the Phil, Colin, or any of authors of PGP.
+ *
+ * Further background information on this topic may be obtained from
+ * RFC 4086, "Randomness Requirements for Security", by Donald
+ * Eastlake, Steve Crocker, and Jeff Schiller.
+ */
+
+#include <linux/utsname.h>
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/major.h>
+#include <linux/string.h>
+#include <linux/fcntl.h>
+#include <linux/slab.h>
+#include <linux/random.h>
+#include <linux/poll.h>
+#include <linux/init.h>
+#include <linux/fs.h>
+#include <linux/genhd.h>
+#include <linux/interrupt.h>
+#include <linux/mm.h>
+#include <linux/spinlock.h>
+#include <linux/kthread.h>
+#include <linux/percpu.h>
+#include <linux/cryptohash.h>
+#include <linux/fips.h>
+#include <linux/ptrace.h>
+#include <linux/kmemcheck.h>
+#include <linux/workqueue.h>
+#include <linux/irq.h>
+#include <linux/syscalls.h>
+#include <linux/completion.h>
+
+#include <asm/processor.h>
+#include <asm/uaccess.h>
+#include <asm/irq.h>
+#include <asm/irq_regs.h>
+#include <asm/io.h>
+
+#define CREATE_TRACE_POINTS
+#include <trace/events/random.h>
+
+/* #define ADD_INTERRUPT_BENCH */
+
+#ifndef CONFIG_RANDOM_INIT
+#error This version needs CONFIG_RANDOM_INIT
+#endif
+#ifndef CONFIG_RANDOM_GCM
+#error This version should not be compiled if CONFIG_RANDOM_GCM is not set
+#endif
+
+/*
+ * Configuration information
+ */
+
+#include <generated/random_init.h>
+
+#define EXTRACT_SIZE 16 /* 128-bit GCM hash */
+#define SEC_XFER_SIZE 512
+#define DEBUG_RANDOM_BOOT 0
+
+#define LONGS(x) (((x) + sizeof(unsigned long) - 1)/sizeof(unsigned long))
+
+/*
+ * To allow fractional bits to be tracked, the entropy_count field is
+ * denominated in units of 1/8th bits.
+ *
+ * 2*(ENTROPY_SHIFT + log2(poolbits)) must <= 31, or the multiply in
+ * credit_entropy_bits() needs to be 64 bits wide.
+ */
+#define ENTROPY_SHIFT 3
+#define ENTROPY_BITS(r) ((r)->entropy_count >> ENTROPY_SHIFT)
+
+/* sanity checks */
+
+#if( (ENTROPY_SHIFT+INPUT_POOL_SHIFT) >= 16)
+#error *_SHIFT values problematic for credit_entropy_bits()ki
+#endif
+
+#if( (INPUT_POOL_WORDS%16) || (OUTPUT_POOL_WORDS%16) )
+#error Pool size not divisible by 16, which code assumes
+#endif
+
+#if( INPUT_POOL_WORDS < 32 )
+#error Input pool less than a quarter of default size
+#endif
+
+#if( INPUT_POOL_WORDS < OUTPUT_POOL_WORDS )
+#error Strange configuration, input pool smalller than output
+#endif
+
+/*
+ * The minimum number of bits of entropy before we wake up a read on
+ * /dev/random. Should be enough to do a significant reseed.
+ */
+static int random_read_wakeup_bits = 64;
+
+/*
+ * If the entropy count falls under this number of bits, then we
+ * should wake up processes which are selecting or polling on write
+ * access to /dev/random.
+ */
+static int random_write_wakeup_bits = 28 * OUTPUT_POOL_WORDS;
+
+/*
+ * The minimum number of seconds between urandom pool reseeding. We
+ * do this to limit the amount of entropy that can be drained from the
+ * input pool even if there are heavy demands on /dev/urandom.
+ */
+static int random_min_urandom_seed = 60;
+
+/*
+ * Originally, we used a primitive polynomial of degree .poolwords
+ * over GF(2). The taps for various sizes are defined below. They
+ * were chosen to be evenly spaced except for the last tap, which is 1
+ * to get the twisting happening as fast as possible.
+ *
+ * For the purposes of better mixing, we use the CRC-32 polynomial as
+ * well to make a (modified) twisted Generalized Feedback Shift
+ * Register. (See M. Matsumoto & Y. Kurita, 1992. Twisted GFSR
+ * generators. ACM Transactions on Modeling and Computer Simulation
+ * 2(3):179-194. Also see M. Matsumoto & Y. Kurita, 1994. Twisted
+ * GFSR generators II. ACM Transactions on Modeling and Computer
+ * Simulation 4:254-266)
+ *
+ * Thanks to Colin Plumb for suggesting this.
+ *
+ * The mixing operation is much less sensitive than the output hash,
+ * where we use SHA-1. All that we want of mixing operation is that
+ * it be a good non-cryptographic hash; i.e. it not produce collisions
+ * when fed "random" data of the sort we expect to see. As long as
+ * the pool state differs for different inputs, we have preserved the
+ * input entropy and done a good job. The fact that an intelligent
+ * attacker can construct inputs that will produce controlled
+ * alterations to the pool's state is not important because we don't
+ * consider such inputs to contribute any randomness. The only
+ * property we need with respect to them is that the attacker can't
+ * increase his/her knowledge of the pool's state. Since all
+ * additions are reversible (knowing the final state and the input,
+ * you can reconstruct the initial state), if an attacker has any
+ * uncertainty about the initial state, he/she can only shuffle that
+ * uncertainty about, but never cause any collisions (which would
+ * decrease the uncertainty).
+ *
+ * Our mixing functions were analyzed by Lacharme, Roeck, Strubel, and
+ * Videau in their paper, "The Linux Pseudorandom Number Generator
+ * Revisited" (see: http://eprint.iacr.org/2012/251.pdf). In their
+ * paper, they point out that we are not using a true Twisted GFSR,
+ * since Matsumoto & Kurita used a trinomial feedback polynomial (that
+ * is, with only three taps, instead of the six that we are using).
+ * As a result, the resulting polynomial is neither primitive nor
+ * irreducible, and hence does not have a maximal period over
+ * GF(2**32). They suggest a slight change to the generator
+ * polynomial which improves the resulting TGFSR polynomial to be
+ * irreducible, which we have made here.
+ */
+static struct poolinfo {
+ int poolbitshift, poolwords, poolbytes, poolbits, poolfracbits;
+#define S(x) ilog2(x)+5, (x), (x)*4, (x)*32, (x) << (ENTROPY_SHIFT+5)
+ int tap1, tap2, tap3, tap4, tap5;
+} poolinfo_table[] = {
+ /* was: x^128 + x^103 + x^76 + x^51 +x^25 + x + 1 */
+ /* x^128 + x^104 + x^76 + x^51 +x^25 + x + 1 */
+ { S(128), 104, 76, 51, 25, 1 },
+ /* was: x^32 + x^26 + x^20 + x^14 + x^7 + x + 1 */
+ /* x^32 + x^26 + x^19 + x^14 + x^7 + x + 1 */
+ { S(32), 26, 19, 14, 7, 1 },
+#if 0
+ /* x^2048 + x^1638 + x^1231 + x^819 + x^411 + x + 1 -- 115 */
+ { S(2048), 1638, 1231, 819, 411, 1 },
+
+ /* x^1024 + x^817 + x^615 + x^412 + x^204 + x + 1 -- 290 */
+ { S(1024), 817, 615, 412, 204, 1 },
+
+ /* x^1024 + x^819 + x^616 + x^410 + x^207 + x^2 + 1 -- 115 */
+ { S(1024), 819, 616, 410, 207, 2 },
+
+ /* x^512 + x^411 + x^308 + x^208 + x^104 + x + 1 -- 225 */
+ { S(512), 411, 308, 208, 104, 1 },
+
+ /* x^512 + x^409 + x^307 + x^206 + x^102 + x^2 + 1 -- 95 */
+ { S(512), 409, 307, 206, 102, 2 },
+ /* x^512 + x^409 + x^309 + x^205 + x^103 + x^2 + 1 -- 95 */
+ { S(512), 409, 309, 205, 103, 2 },
+
+ /* x^256 + x^205 + x^155 + x^101 + x^52 + x + 1 -- 125 */
+ { S(256), 205, 155, 101, 52, 1 },
+
+ /* x^128 + x^103 + x^78 + x^51 + x^27 + x^2 + 1 -- 70 */
+ { S(128), 103, 78, 51, 27, 2 },
+
+ /* x^64 + x^52 + x^39 + x^26 + x^14 + x + 1 -- 15 */
+ { S(64), 52, 39, 26, 14, 1 },
+#endif
+};
+
+/*
+ * Static global variables
+ */
+static DECLARE_WAIT_QUEUE_HEAD(random_read_wait);
+static DECLARE_WAIT_QUEUE_HEAD(random_write_wait);
+static DECLARE_WAIT_QUEUE_HEAD(urandom_init_wait);
+static struct fasync_struct *fasync;
+
+static DEFINE_SPINLOCK(random_ready_list_lock);
+static LIST_HEAD(random_ready_list);
+
+/**********************************************************************
+ *
+ * OS independent entropy store. Here are the functions which handle
+ * storing entropy in an entropy pool.
+ *
+ **********************************************************************/
+
+struct entropy_store;
+struct entropy_store {
+ /* read-only data: */
+ const struct poolinfo *poolinfo;
+ __u32 *pool;
+ const char *name;
+ struct entropy_store *pull;
+ struct work_struct push_work;
+
+ /* read-write data: */
+ unsigned long last_pulled;
+ spinlock_t lock;
+ unsigned short add_ptr;
+ unsigned short input_rotate;
+ int entropy_count;
+ int entropy_total;
+ unsigned int initialized:1;
+ unsigned int limit:1;
+ unsigned int last_data_init:1;
+ __u8 last_data[EXTRACT_SIZE];
+ u32 *A, *B, which, count ;
+ u32 *p, *q, *end, size ;
+};
+
+static void push_to_pool(struct work_struct *work);
+
+static struct entropy_store input_pool = {
+ .poolinfo = &poolinfo_table[0],
+ .name = "input",
+ .limit = 1,
+ .lock = __SPIN_LOCK_UNLOCKED(input_pool.lock),
+ .pool = pools,
+ .A = constants,
+ .B = constants+4,
+ .which = 0,
+ .count = 0,
+ .size = INPUT_POOL_WORDS,
+ .p = pools,
+ .q = pools + (INPUT_POOL_WORDS/2),
+ .end = pools + INPUT_POOL_WORDS
+};
+
+static struct entropy_store blocking_pool = {
+ .poolinfo = &poolinfo_table[1],
+ .name = "blocking",
+ .limit = 1,
+ .pull = &input_pool,
+ .lock = __SPIN_LOCK_UNLOCKED(blocking_pool.lock),
+ .push_work = __WORK_INITIALIZER(blocking_pool.push_work,
+ push_to_pool),
+ .pool = pools + INPUT_POOL_WORDS,
+ .A = constants+8,
+ .B = constants+12,
+ .which = 0,
+ .count = 0,
+ .size = OUTPUT_POOL_WORDS,
+ .p = pools + INPUT_POOL_WORDS,
+ .q = pools + INPUT_POOL_WORDS + (OUTPUT_POOL_WORDS/2),
+ .end = pools + INPUT_POOL_WORDS + OUTPUT_POOL_WORDS
+};
+
+static struct entropy_store nonblocking_pool = {
+ .poolinfo = &poolinfo_table[1],
+ .name = "nonblocking",
+ .pull = &input_pool,
+ .lock = __SPIN_LOCK_UNLOCKED(nonblocking_pool.lock),
+ .push_work = __WORK_INITIALIZER(nonblocking_pool.push_work,
+ push_to_pool),
+ .pool = pools + INPUT_POOL_WORDS + OUTPUT_POOL_WORDS,
+ .A = constants+16,
+ .B = constants+20,
+ .which = 0,
+ .count = 0,
+ .size = OUTPUT_POOL_WORDS,
+ .p = pools + INPUT_POOL_WORDS + OUTPUT_POOL_WORDS,
+ .q = pools + INPUT_POOL_WORDS + OUTPUT_POOL_WORDS + (OUTPUT_POOL_WORDS/2),
+ .end = pools + INPUT_POOL_WORDS + (OUTPUT_POOL_WORDS*2)
+};
+
+/* no actual pool; just hash the counter */
+static struct entropy_store dummy_pool = {
+ .poolinfo = &poolinfo_table[1],
+ .name = "dummy",
+ .lock = __SPIN_LOCK_UNLOCKED(dummy_pool.lock),
+ .pool = NULL,
+ .A = constants+24,
+ .B = constants+28,
+ .which = 0,
+ .count = 0,
+ /* should never be used */
+ .size = 0,
+ .p = NULL,
+ .q = NULL,
+ .end = NULL
+};
+
+static int got_hw_rng ;
+
+/*****************************************************************
+ * forward declarations and a few macros
+ *****************************************************************/
+
+static void init_random(void) ;
+
+/* fill an output buffer from a pool */
+static void loop_output( struct entropy_store *, u32 *, u32 ) ;
+
+static void count(void) ;
+static void counter_any(void) ;
+
+/* get 128 bits */
+static int get_or_fail( struct entropy_store *, u32 * ) ;
+static void get128( struct entropy_store *, u32 * ) ;
+static int get_any( u32 * ) ;
+
+/* These functions each do a unidirectional mix
+ * into some data structure. They mix in 128 bits
+ * at a time to give "catastrophic reseeding", and
+ * all zero out the input buffer after use.
+ */
+static void buffer2array( struct entropy_store *, u32 * ) ;
+static void buffer2pool( struct entropy_store *, u32 * ) ;
+static void buffer2counter( u32 * ) ;
+
+/* hw rng functions */
+static int get_hw_random( u32 * ) ;
+static int load_constants(void) ;
+static int load_input(void) ;
+
+/* mix chunks of data structures in place */
+static void mix_const_p( struct entropy_store * ) ;
+static void mix_const_all(void);
+static void top_mix(void);
+static void big_mix(void);
+
+static void clear_addmul(void);
+
+/* rotate a 32-bit word left n bits */
+#define ROTL(v, n) ( ((v) << (n)) | ((v) >> (32 - (n))) )
+
+/* common case with 128-bit buffer */
+#define zero128( target ) memzero_explicit( (u8 *) target, 16 )
+
+static __u32 const twist_table[8] = {
+ 0x00000000, 0x3b6e20c8, 0x76dc4190, 0x4db26158,
+ 0xedb88320, 0xd6d6a3e8, 0x9b64c2b0, 0xa00ae278 };
+
+/*
+ * This function adds bytes into the entropy "pool". It does not
+ * update the entropy estimate. The caller should call
+ * credit_entropy_bits if this is appropriate.
+ *
+ * The pool is stirred with a primitive polynomial of the appropriate
+ * degree, and then twisted. We twist by three bits at a time because
+ * it's cheap to do so and helps slightly in the expected case where
+ * the entropy is concentrated in the low-order bits.
+ */
+static void _mix_pool_bytes(struct entropy_store *r, const void *in,
+ int nbytes)
+{
+ unsigned long i, tap1, tap2, tap3, tap4, tap5;
+ int input_rotate;
+ int wordmask = r->poolinfo->poolwords - 1;
+ const char *bytes = in;
+ __u32 w;
+
+ tap1 = r->poolinfo->tap1;
+ tap2 = r->poolinfo->tap2;
+ tap3 = r->poolinfo->tap3;
+ tap4 = r->poolinfo->tap4;
+ tap5 = r->poolinfo->tap5;
+
+ input_rotate = r->input_rotate;
+ i = r->add_ptr;
+
+ /* mix one byte at a time to simplify size handling and churn faster */
+ while (nbytes--) {
+ w = rol32(*bytes++, input_rotate);
+ i = (i - 1) & wordmask;
+
+ /* XOR in the various taps */
+ w ^= r->pool[i];
+ w ^= r->pool[(i + tap1) & wordmask];
+ w ^= r->pool[(i + tap2) & wordmask];
+ w ^= r->pool[(i + tap3) & wordmask];
+ w ^= r->pool[(i + tap4) & wordmask];
+ w ^= r->pool[(i + tap5) & wordmask];
+
+ /* Mix the result back in with a twist */
+ r->pool[i] = (w >> 3) ^ twist_table[w & 7];
+
+ /*
+ * Normally, we add 7 bits of rotation to the pool.
+ * At the beginning of the pool, add an extra 7 bits
+ * rotation, so that successive passes spread the
+ * input bits across the pool evenly.
+ */
+ input_rotate = (input_rotate + (i ? 7 : 14)) & 31;
+ }
+
+ r->input_rotate = input_rotate;
+ r->add_ptr = i;
+}
+
+static void __mix_pool_bytes(struct entropy_store *r, const void *in,
+ int nbytes)
+{
+ trace_mix_pool_bytes_nolock(r->name, nbytes, _RET_IP_);
+ _mix_pool_bytes(r, in, nbytes);
+}
+
+static void mix_pool_bytes(struct entropy_store *r, const void *in,
+ int nbytes)
+{
+ unsigned long flags;
+
+ trace_mix_pool_bytes(r->name, nbytes, _RET_IP_);
+ spin_lock_irqsave(&r->lock, flags);
+ _mix_pool_bytes(r, in, nbytes);
+ spin_unlock_irqrestore(&r->lock, flags);
+}
+
+struct fast_pool {
+ __u32 pool[4];
+ unsigned long last;
+ unsigned short reg_idx;
+ unsigned char count;
+};
+
+/*
+ * This is a fast mixing routine used by the interrupt randomness
+ * collector. It's hardcoded for an 128 bit pool and assumes that any
+ * locks that might be needed are taken by the caller.
+ */
+static void fast_mix(struct fast_pool *f)
+{
+ __u32 a = f->pool[0], b = f->pool[1];
+ __u32 c = f->pool[2], d = f->pool[3];
+
+ a += b; c += d;
+ b = rol32(b, 6); d = rol32(d, 27);
+ d ^= a; b ^= c;
+
+ a += b; c += d;
+ b = rol32(b, 16); d = rol32(d, 14);
+ d ^= a; b ^= c;
+
+ a += b; c += d;
+ b = rol32(b, 6); d = rol32(d, 27);
+ d ^= a; b ^= c;
+
+ a += b; c += d;
+ b = rol32(b, 16); d = rol32(d, 14);
+ d ^= a; b ^= c;
+
+ f->pool[0] = a; f->pool[1] = b;
+ f->pool[2] = c; f->pool[3] = d;
+ f->count++;
+}
+
+static void process_random_ready_list(void)
+{
+ unsigned long flags;
+ struct random_ready_callback *rdy, *tmp;
+
+ spin_lock_irqsave(&random_ready_list_lock, flags);
+ list_for_each_entry_safe(rdy, tmp, &random_ready_list, list) {
+ struct module *owner = rdy->owner;
+
+ list_del_init(&rdy->list);
+ rdy->func(rdy);
+ module_put(owner);
+ }
+ spin_unlock_irqrestore(&random_ready_list_lock, flags);
+}
+
+/*
+ * Credit (or debit) the entropy store with n bits of entropy.
+ * Use credit_entropy_bits_safe() if the value comes from userspace
+ * or otherwise should be checked for extreme values.
+ */
+static void credit_entropy_bits(struct entropy_store *r, int nbits)
+{
+ int entropy_count, orig;
+ const int pool_size = r->poolinfo->poolfracbits;
+ int nfrac = nbits << ENTROPY_SHIFT;
+
+ if (!nbits)
+ return;
+
+retry:
+ entropy_count = orig = ACCESS_ONCE(r->entropy_count);
+ if (nfrac < 0) {
+ /* Debit */
+ entropy_count += nfrac;
+ } else {
+ /*
+ * Credit: we have to account for the possibility of
+ * overwriting already present entropy. Even in the
+ * ideal case of pure Shannon entropy, new contributions
+ * approach the full value asymptotically:
+ *
+ * entropy <- entropy + (pool_size - entropy) *
+ * (1 - exp(-add_entropy/pool_size))
+ *
+ * For add_entropy <= pool_size/2 then
+ * (1 - exp(-add_entropy/pool_size)) >=
+ * (add_entropy/pool_size)*0.7869...
+ * so we can approximate the exponential with
+ * 3/4*add_entropy/pool_size and still be on the
+ * safe side by adding at most pool_size/2 at a time.
+ *
+ * The use of pool_size-2 in the while statement is to
+ * prevent rounding artifacts from making the loop
+ * arbitrarily long; this limits the loop to log2(pool_size)*2
+ * turns no matter how large nbits is.
+ */
+ int pnfrac = nfrac;
+ const int s = r->poolinfo->poolbitshift + ENTROPY_SHIFT + 2;
+ /* The +2 corresponds to the /4 in the denominator */
+
+ do {
+ unsigned int anfrac = min(pnfrac, pool_size/2);
+ unsigned int add =
+ ((pool_size - entropy_count)*anfrac*3) >> s;
+
+ entropy_count += add;
+ pnfrac -= anfrac;
+ } while (unlikely(entropy_count < pool_size-2 && pnfrac));
+ }
+
+ if (unlikely(entropy_count < 0)) {
+ pr_warn("random: negative entropy/overflow: pool %s count %d\n",
+ r->name, entropy_count);
+ WARN_ON(1);
+ entropy_count = 0;
+ } else if (entropy_count > pool_size)
+ entropy_count = pool_size;
+ if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig)
+ goto retry;
+
+ r->entropy_total += nbits;
+ if (!r->initialized && r->entropy_total > 128) {
+ r->initialized = 1;
+ r->entropy_total = 0;
+ if (r == &nonblocking_pool) {
+ prandom_reseed_late();
+ process_random_ready_list();
+ wake_up_all(&urandom_init_wait);
+ pr_notice("random: %s pool is initialized\n", r->name);
+ }
+ }
+
+ trace_credit_entropy_bits(r->name, nbits,
+ entropy_count >> ENTROPY_SHIFT,
+ r->entropy_total, _RET_IP_);
+
+ if (r == &input_pool) {
+ int entropy_bits = entropy_count >> ENTROPY_SHIFT;
+
+ /* should we wake readers? */
+ if (entropy_bits >= random_read_wakeup_bits) {
+ wake_up_interruptible(&random_read_wait);
+ kill_fasync(&fasync, SIGIO, POLL_IN);
+ }
+ /* If the input pool is getting full, send some
+ * entropy to the two output pools, flipping back and
+ * forth between them, until the output pools are 75%
+ * full.
+ */
+ if (entropy_bits > random_write_wakeup_bits &&
+ r->initialized &&
+ r->entropy_total >= 2*random_read_wakeup_bits) {
+ static struct entropy_store *last = &blocking_pool;
+ struct entropy_store *other = &blocking_pool;
+
+ if (last == &blocking_pool)
+ other = &nonblocking_pool;
+ if (other->entropy_count <=
+ 3 * other->poolinfo->poolfracbits / 4)
+ last = other;
+ if (last->entropy_count <=
+ 3 * last->poolinfo->poolfracbits / 4) {
+ schedule_work(&last->push_work);
+ r->entropy_total = 0;
+ }
+ }
+ }
+}
+
+static void credit_entropy_bits_safe(struct entropy_store *r, int nbits)
+{
+ const int nbits_max = (int)(~0U >> (ENTROPY_SHIFT + 1));
+
+ /* Cap the value to avoid overflows */
+ nbits = min(nbits, nbits_max);
+ nbits = max(nbits, -nbits_max);
+
+ credit_entropy_bits(r, nbits);
+}
+
+/*********************************************************************
+ *
+ * Entropy input management
+ *
+ *********************************************************************/
+
+/* There is one of these per entropy source */
+struct timer_rand_state {
+ cycles_t last_time;
+ long last_delta, last_delta2;
+ unsigned dont_count_entropy:1;
+};
+
+#define INIT_TIMER_RAND_STATE { INITIAL_JIFFIES, };
+
+/*
+ * Add device- or boot-specific data to the input and nonblocking
+ * pools to help initialize them to unique values.
+ *
+ * None of this adds any entropy, it is meant to avoid the
+ * problem of the nonblocking pool having similar initial state
+ * across largely identical devices.
+ */
+void add_device_randomness(const void *buf, unsigned int size)
+{
+ unsigned long time = random_get_entropy() ^ jiffies;
+ unsigned long flags;
+
+ trace_add_device_randomness(size, _RET_IP_);
+ spin_lock_irqsave(&input_pool.lock, flags);
+ _mix_pool_bytes(&input_pool, buf, size);
+ _mix_pool_bytes(&input_pool, &time, sizeof(time));
+ spin_unlock_irqrestore(&input_pool.lock, flags);
+
+ spin_lock_irqsave(&nonblocking_pool.lock, flags);
+ _mix_pool_bytes(&nonblocking_pool, buf, size);
+ _mix_pool_bytes(&nonblocking_pool, &time, sizeof(time));
+ spin_unlock_irqrestore(&nonblocking_pool.lock, flags);
+}
+EXPORT_SYMBOL(add_device_randomness);
+
+static struct timer_rand_state input_timer_state = INIT_TIMER_RAND_STATE;
+
+/*
+ * This function adds entropy to the entropy "pool" by using timing
+ * delays. It uses the timer_rand_state structure to make an estimate
+ * of how many bits of entropy this call has added to the pool.
+ *
+ * The number "num" is also added to the pool - it should somehow describe
+ * the type of event which just happened. This is currently 0-255 for
+ * keyboard scan codes, and 256 upwards for interrupts.
+ *
+ */
+static void add_timer_randomness(struct timer_rand_state *state, unsigned num)
+{
+ struct entropy_store *r;
+ struct {
+ long jiffies;
+ unsigned cycles;
+ unsigned num;
+ } sample;
+ long delta, delta2, delta3;
+
+ preempt_disable();
+
+ sample.jiffies = jiffies;
+ sample.cycles = random_get_entropy();
+ sample.num = num;
+ r = nonblocking_pool.initialized ? &input_pool : &nonblocking_pool;
+ mix_pool_bytes(r, &sample, sizeof(sample));
+
+ /*
+ * Calculate number of bits of randomness we probably added.
+ * We take into account the first, second and third-order deltas
+ * in order to make our estimate.
+ */
+
+ if (!state->dont_count_entropy) {
+ delta = sample.jiffies - state->last_time;
+ state->last_time = sample.jiffies;
+
+ delta2 = delta - state->last_delta;
+ state->last_delta = delta;
+
+ delta3 = delta2 - state->last_delta2;
+ state->last_delta2 = delta2;
+
+ if (delta < 0)
+ delta = -delta;
+ if (delta2 < 0)
+ delta2 = -delta2;
+ if (delta3 < 0)
+ delta3 = -delta3;
+ if (delta > delta2)
+ delta = delta2;
+ if (delta > delta3)
+ delta = delta3;
+
+ /*
+ * delta is now minimum absolute delta.
+ * Round down by 1 bit on general principles,
+ * and limit entropy entimate to 12 bits.
+ */
+ credit_entropy_bits(r, min_t(int, fls(delta>>1), 11));
+ }
+ preempt_enable();
+}
+
+void add_input_randomness(unsigned int type, unsigned int code,
+ unsigned int value)
+{
+ static unsigned char last_value;
+
+ /* ignore autorepeat and the like */
+ if (value == last_value)
+ return;
+
+ last_value = value;
+ add_timer_randomness(&input_timer_state,
+ (type << 4) ^ code ^ (code >> 4) ^ value);
+ trace_add_input_randomness(ENTROPY_BITS(&input_pool));
+}
+EXPORT_SYMBOL_GPL(add_input_randomness);
+
+static DEFINE_PER_CPU(struct fast_pool, irq_randomness);
+
+#ifdef ADD_INTERRUPT_BENCH
+static unsigned long avg_cycles, avg_deviation;
+
+#define AVG_SHIFT 8 /* Exponential average factor k=1/256 */
+#define FIXED_1_2 (1 << (AVG_SHIFT-1))
+
+static void add_interrupt_bench(cycles_t start)
+{
+ long delta = random_get_entropy() - start;
+
+ /* Use a weighted moving average */
+ delta = delta - ((avg_cycles + FIXED_1_2) >> AVG_SHIFT);
+ avg_cycles += delta;
+ /* And average deviation */
+ delta = abs(delta) - ((avg_deviation + FIXED_1_2) >> AVG_SHIFT);
+ avg_deviation += delta;
+}
+#else
+#define add_interrupt_bench(x)
+#endif
+
+static __u32 get_reg(struct fast_pool *f, struct pt_regs *regs)
+{
+ __u32 *ptr = (__u32 *) regs;
+
+ if (regs == NULL)
+ return 0;
+ if (f->reg_idx >= sizeof(struct pt_regs) / sizeof(__u32))
+ f->reg_idx = 0;
+ return *(ptr + f->reg_idx++);
+}
+
+void add_interrupt_randomness(int irq, int irq_flags)
+{
+ struct entropy_store *r;
+ struct fast_pool *fast_pool = this_cpu_ptr(&irq_randomness);
+ struct pt_regs *regs = get_irq_regs();
+ unsigned long now = jiffies;
+ cycles_t cycles = random_get_entropy();
+ __u32 c_high, j_high;
+ __u64 ip;
+ unsigned long seed;
+ int credit = 0;
+
+ if (cycles == 0)
+ cycles = get_reg(fast_pool, regs);
+ c_high = (sizeof(cycles) > 4) ? cycles >> 32 : 0;
+ j_high = (sizeof(now) > 4) ? now >> 32 : 0;
+ fast_pool->pool[0] ^= cycles ^ j_high ^ irq;
+ fast_pool->pool[1] ^= now ^ c_high;
+ ip = regs ? instruction_pointer(regs) : _RET_IP_;
+ fast_pool->pool[2] ^= ip;
+ fast_pool->pool[3] ^= (sizeof(ip) > 4) ? ip >> 32 :
+ get_reg(fast_pool, regs);
+
+ fast_mix(fast_pool);
+ add_interrupt_bench(cycles);
+
+ if ((fast_pool->count < 64) &&
+ !time_after(now, fast_pool->last + HZ))
+ return;
+
+ r = nonblocking_pool.initialized ? &input_pool : &nonblocking_pool;
+ if (!spin_trylock(&r->lock))
+ return;
+
+ fast_pool->last = now;
+ __mix_pool_bytes(r, &fast_pool->pool, sizeof(fast_pool->pool));
+
+ /*
+ * If we have architectural seed generator, produce a seed and
+ * add it to the pool. For the sake of paranoia don't let the
+ * architectural seed generator dominate the input from the
+ * interrupt noise.
+ */
+ if (arch_get_random_seed_long(&seed)) {
+ __mix_pool_bytes(r, &seed, sizeof(seed));
+ credit = 1;
+ }
+ spin_unlock(&r->lock);
+
+ fast_pool->count = 0;
+
+ /* award one bit for the contents of the fast pool */
+ credit_entropy_bits(r, credit + 1);
+}
+
+#ifdef CONFIG_BLOCK
+void add_disk_randomness(struct gendisk *disk)
+{
+ if (!disk || !disk->random)
+ return;
+ /* first major is 1, so we get >= 0x200 here */
+ add_timer_randomness(disk->random, 0x100 + disk_devt(disk));
+ trace_add_disk_randomness(disk_devt(disk), ENTROPY_BITS(&input_pool));
+}
+EXPORT_SYMBOL_GPL(add_disk_randomness);
+#endif
+
+/*********************************************************************
+ *
+ * Entropy extraction routines
+ *
+ *********************************************************************/
+
+static ssize_t extract_entropy(struct entropy_store *r, void *buf,
+ size_t nbytes, int min, int rsvd);
+
+/*
+ * This utility inline function is responsible for transferring entropy
+ * from the primary pool to the secondary extraction pool. We make
+ * sure we pull enough for a 'catastrophic reseed'.
+ */
+static void _xfer_secondary_pool(struct entropy_store *r, size_t nbytes);
+static void xfer_secondary_pool(struct entropy_store *r, size_t nbytes)
+{
+ if (!r->pull ||
+ r->entropy_count >= (nbytes << (ENTROPY_SHIFT + 3)) ||
+ r->entropy_count > r->poolinfo->poolfracbits)
+ return;
+
+ if (r->limit == 0 && random_min_urandom_seed) {
+ unsigned long now = jiffies;
+
+ if (time_before(now,
+ r->last_pulled + random_min_urandom_seed * HZ))
+ return;
+ r->last_pulled = now;
+ }
+
+ _xfer_secondary_pool(r, nbytes);
+}
+
+static void _xfer_secondary_pool(struct entropy_store *r, size_t nbytes)
+{
+ u32 temp[4] ;
+ int bytes = nbytes;
+
+ /* pull at least as much as a wakeup */
+ bytes = max_t(int, bytes, random_read_wakeup_bits / 8);
+ /* but never more than the pool size */
+ bytes = min_t(int, bytes, OUTPUT_POOL_WORDS);
+
+ trace_xfer_secondary_pool(r->name, bytes * 8, nbytes * 8,
+ ENTROPY_BITS(r), ENTROPY_BITS(r->pull));
+ for( ; bytes > 3 ; bytes -= 4 ) {
+ get128(r->pull, temp ) ;
+ buffer2pool( r, temp ) ;
+ }
+}
+
+/*
+ * Used as a workqueue function so that when the input pool is getting
+ * full, we can "spill over" some entropy to the output pools. That
+ * way the output pools can store some of the excess entropy instead
+ * of letting it go to waste.
+ */
+static void push_to_pool(struct work_struct *work)
+{
+ struct entropy_store *r = container_of(work, struct entropy_store,
+ push_work);
+ BUG_ON(!r);
+ _xfer_secondary_pool(r, random_read_wakeup_bits/8);
+ trace_push_to_pool(r->name, r->entropy_count >> ENTROPY_SHIFT,
+ r->pull->entropy_count >> ENTROPY_SHIFT);
+}
+
+/*
+ * This function decides how many bytes to actually take from the
+ * given pool, and also debits the entropy count accordingly.
+ */
+static size_t account(struct entropy_store *r, size_t nbytes, int min,
+ int reserved)
+{
+ int entropy_count, orig;
+ size_t ibytes, nfrac;
+
+ BUG_ON(r->entropy_count > r->poolinfo->poolfracbits);
+
+ /* Can we pull enough? */
+retry:
+ entropy_count = orig = ACCESS_ONCE(r->entropy_count);
+ ibytes = nbytes;
+ /* If limited, never pull more than available */
+ if (r->limit) {
+ int have_bytes = entropy_count >> (ENTROPY_SHIFT + 3);
+
+ if ((have_bytes -= reserved) < 0)
+ have_bytes = 0;
+ ibytes = min_t(size_t, ibytes, have_bytes);
+ }
+ if (ibytes < min)
+ ibytes = 0;
+
+ if (unlikely(entropy_count < 0)) {
+ pr_warn("random: negative entropy count: pool %s count %d\n",
+ r->name, entropy_count);
+ WARN_ON(1);
+ entropy_count = 0;
+ }
+ nfrac = ibytes << (ENTROPY_SHIFT + 3);
+ if ((size_t) entropy_count > nfrac)
+ entropy_count -= nfrac;
+ else
+ entropy_count = 0;
+
+ if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig)
+ goto retry;
+
+ trace_debit_entropy(r->name, 8 * ibytes);
+ if (ibytes &&
+ (r->entropy_count >> ENTROPY_SHIFT) < random_write_wakeup_bits) {
+ wake_up_interruptible(&random_write_wait);
+ kill_fasync(&fasync, SIGIO, POLL_OUT);
+ }
+
+ return ibytes;
+}
+
+/*
+ * This function does the actual extraction for extract_entropy and
+ * extract_entropy_user.
+ *
+ * Note: we assume that .poolwords is a multiple of 16 words.
+ */
+static void extract_buf(struct entropy_store *r, __u8 *out)
+{
+ get128( r, (u32 *) out ) ;
+}
+
+/*
+ * This function extracts randomness from the "entropy pool", and
+ * returns it in a buffer.
+ *
+ * The min parameter specifies the minimum amount we can pull before
+ * failing to avoid races that defeat catastrophic reseeding while the
+ * reserved parameter indicates how much entropy we must leave in the
+ * pool after each pull to avoid starving other readers.
+ */
+static ssize_t extract_entropy(struct entropy_store *r, void *buf,
+ size_t nbytes, int min, int reserved)
+{
+ ssize_t ret = 0, i;
+ __u8 tmp[EXTRACT_SIZE];
+ unsigned long flags;
+
+ /* if last_data isn't primed, we need EXTRACT_SIZE extra bytes */
+ if (fips_enabled) {
+ spin_lock_irqsave(&r->lock, flags);
+ if (!r->last_data_init) {
+ r->last_data_init = 1;
+ spin_unlock_irqrestore(&r->lock, flags);
+ trace_extract_entropy(r->name, EXTRACT_SIZE,
+ ENTROPY_BITS(r), _RET_IP_);
+ xfer_secondary_pool(r, EXTRACT_SIZE);
+ extract_buf(r, tmp);
+ spin_lock_irqsave(&r->lock, flags);
+ memcpy(r->last_data, tmp, EXTRACT_SIZE);
+ }
+ spin_unlock_irqrestore(&r->lock, flags);
+ }
+
+ trace_extract_entropy(r->name, nbytes, ENTROPY_BITS(r), _RET_IP_);
+ xfer_secondary_pool(r, nbytes);
+ nbytes = account(r, nbytes, min, reserved);
+
+ while (nbytes) {
+ extract_buf(r, tmp);
+
+ if (fips_enabled) {
+ spin_lock_irqsave(&r->lock, flags);
+ if (!memcmp(tmp, r->last_data, EXTRACT_SIZE))
+ panic("Hardware RNG duplicated output!\n");
+ memcpy(r->last_data, tmp, EXTRACT_SIZE);
+ spin_unlock_irqrestore(&r->lock, flags);
+ }
+ i = min_t(int, nbytes, EXTRACT_SIZE);
+ memcpy(buf, tmp, i);
+ nbytes -= i;
+ buf += i;
+ ret += i;
+ }
+
+ /* Wipe data just returned from memory */
+ memzero_explicit(tmp, sizeof(tmp));
+
+ return ret;
+}
+
+/*
+ * This function extracts randomness from the "entropy pool", and
+ * returns it in a userspace buffer.
+ */
+static ssize_t extract_entropy_user(struct entropy_store *r, void __user *buf,
+ size_t nbytes)
+{
+ ssize_t ret = 0, i;
+ __u8 tmp[EXTRACT_SIZE];
+ int large_request = (nbytes > 256);
+
+ trace_extract_entropy_user(r->name, nbytes, ENTROPY_BITS(r), _RET_IP_);
+ xfer_secondary_pool(r, nbytes);
+ nbytes = account(r, nbytes, 0, 0);
+
+ while (nbytes) {
+ if (large_request && need_resched()) {
+ if (signal_pending(current)) {
+ if (ret == 0)
+ ret = -ERESTARTSYS;
+ break;
+ }
+ schedule();
+ }
+
+ extract_buf(r, tmp);
+ i = min_t(int, nbytes, EXTRACT_SIZE);
+ if (copy_to_user(buf, tmp, i)) {
+ ret = -EFAULT;
+ break;
+ }
+
+ nbytes -= i;
+ buf += i;
+ ret += i;
+ }
+
+ /* Wipe data just returned from memory */
+ memzero_explicit(tmp, sizeof(tmp));
+
+ return ret;
+}
+
+/*
+ * This function is the exported kernel interface. It returns some
+ * number of good random numbers, suitable for key generation, seeding
+ * TCP sequence numbers, etc. It does not rely on the hardware random
+ * number generator. For random bytes direct from the hardware RNG
+ * (when available), use get_random_bytes_arch().
+ */
+void get_random_bytes(void *buf, int nbytes)
+{
+#if DEBUG_RANDOM_BOOT > 0
+ if (unlikely(nonblocking_pool.initialized == 0))
+ printk(KERN_NOTICE "random: %pF get_random_bytes called "
+ "with %d bits of entropy available\n",
+ (void *) _RET_IP_,
+ nonblocking_pool.entropy_total);
+#endif
+ trace_get_random_bytes(nbytes, _RET_IP_);
+ loop_output(&nonblocking_pool, buf, nbytes);
+}
+EXPORT_SYMBOL(get_random_bytes);
+
+/*
+ * Add a callback function that will be invoked when the nonblocking
+ * pool is initialised.
+ *
+ * returns: 0 if callback is successfully added
+ * -EALREADY if pool is already initialised (callback not called)
+ * -ENOENT if module for callback is not alive
+ */
+int add_random_ready_callback(struct random_ready_callback *rdy)
+{
+ struct module *owner;
+ unsigned long flags;
+ int err = -EALREADY;
+
+ if (likely(nonblocking_pool.initialized))
+ return err;
+
+ owner = rdy->owner;
+ if (!try_module_get(owner))
+ return -ENOENT;
+
+ spin_lock_irqsave(&random_ready_list_lock, flags);
+ if (nonblocking_pool.initialized)
+ goto out;
+
+ owner = NULL;
+
+ list_add(&rdy->list, &random_ready_list);
+ err = 0;
+
+out:
+ spin_unlock_irqrestore(&random_ready_list_lock, flags);
+
+ module_put(owner);
+
+ return err;
+}
+EXPORT_SYMBOL(add_random_ready_callback);
+
+/*
+ * Delete a previously registered readiness callback function.
+ */
+void del_random_ready_callback(struct random_ready_callback *rdy)
+{
+ unsigned long flags;
+ struct module *owner = NULL;
+
+ spin_lock_irqsave(&random_ready_list_lock, flags);
+ if (!list_empty(&rdy->list)) {
+ list_del_init(&rdy->list);
+ owner = rdy->owner;
+ }
+ spin_unlock_irqrestore(&random_ready_list_lock, flags);
+
+ module_put(owner);
+}
+EXPORT_SYMBOL(del_random_ready_callback);
+
+/*
+ * This function will use the architecture-specific hardware random
+ * number generator if it is available. The arch-specific hw RNG will
+ * almost certainly be faster than what we can do in software, but it
+ * is impossible to verify that it is implemented securely (as
+ * opposed, to, say, the AES encryption of a sequence number using a
+ * key known by the NSA). So it's useful if we need the speed, but
+ * only if we're willing to trust the hardware manufacturer not to
+ * have put in a back door.
+ */
+void get_random_bytes_arch(void *buf, int nbytes)
+{
+ char *p = buf;
+
+ trace_get_random_bytes_arch(nbytes, _RET_IP_);
+ while (nbytes) {
+ unsigned long v;
+ int chunk = min(nbytes, (int)sizeof(unsigned long));
+
+ if (!arch_get_random_long(&v))
+ break;
+
+ memcpy(p, &v, chunk);
+ p += chunk;
+ nbytes -= chunk;
+ }
+
+ if (nbytes)
+ extract_entropy(&nonblocking_pool, p, nbytes, 0, 0);
+}
+EXPORT_SYMBOL(get_random_bytes_arch);
+
+/*
+ * Note that setup_arch() may call add_device_randomness()
+ * long before we get here. This allows seeding of the pools
+ * with some platform dependent data very early in the boot
+ * process. But it limits our options here. We must use
+ * statically allocated structures that already have all
+ * initializations complete at compile time. We should also
+ * take care not to overwrite the precious per platform data
+ * we were given.
+ */
+static int rand_initialize(void)
+{
+ init_random() ;
+ return 0;
+}
+early_initcall(rand_initialize);
+
+#ifdef CONFIG_BLOCK
+void rand_initialize_disk(struct gendisk *disk)
+{
+ struct timer_rand_state *state;
+
+ /*
+ * If kzalloc returns null, we just won't use that entropy
+ * source.
+ */
+ state = kzalloc(sizeof(struct timer_rand_state), GFP_KERNEL);
+ if (state) {
+ state->last_time = INITIAL_JIFFIES;
+ disk->random = state;
+ }
+}
+#endif
+
+static ssize_t
+_random_read(int nonblock, char __user *buf, size_t nbytes)
+{
+ ssize_t n;
+
+ if (nbytes == 0)
+ return 0;
+
+ nbytes = min_t(size_t, nbytes, SEC_XFER_SIZE);
+ while (1) {
+ n = extract_entropy_user(&blocking_pool, buf, nbytes);
+ if (n < 0)
+ return n;
+ trace_random_read(n*8, (nbytes-n)*8,
+ ENTROPY_BITS(&blocking_pool),
+ ENTROPY_BITS(&input_pool));
+ if (n > 0)
+ return n;
+
+ /* Pool is (near) empty. Maybe wait and retry. */
+ if (nonblock)
+ return -EAGAIN;
+
+ wait_event_interruptible(random_read_wait,
+ ENTROPY_BITS(&input_pool) >=
+ random_read_wakeup_bits);
+ if (signal_pending(current))
+ return -ERESTARTSYS;
+ }
+}
+
+static ssize_t
+random_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
+{
+ return _random_read(file->f_flags & O_NONBLOCK, buf, nbytes);
+}
+
+static ssize_t
+urandom_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
+{
+ int ret;
+
+ if (unlikely(nonblocking_pool.initialized == 0))
+ printk_once(KERN_NOTICE "random: %s urandom read "
+ "with %d bits of entropy available\n",
+ current->comm, nonblocking_pool.entropy_total);
+
+ nbytes = min_t(size_t, nbytes, INT_MAX >> (ENTROPY_SHIFT + 3));
+ ret = extract_entropy_user(&nonblocking_pool, buf, nbytes);
+
+ trace_urandom_read(8 * nbytes, ENTROPY_BITS(&nonblocking_pool),
+ ENTROPY_BITS(&input_pool));
+ return ret;
+}
+
+static unsigned int
+random_poll(struct file *file, poll_table * wait)
+{
+ unsigned int mask;
+
+ poll_wait(file, &random_read_wait, wait);
+ poll_wait(file, &random_write_wait, wait);
+ mask = 0;
+ if (ENTROPY_BITS(&input_pool) >= random_read_wakeup_bits)
+ mask |= POLLIN | POLLRDNORM;
+ if (ENTROPY_BITS(&input_pool) < random_write_wakeup_bits)
+ mask |= POLLOUT | POLLWRNORM;
+ return mask;
+}
+
+static int
+write_pool(struct entropy_store *r, const char __user *buffer, size_t count)
+{
+ size_t bytes;
+ __u32 buf[16];
+ const char __user *p = buffer;
+
+ while (count > 0) {
+ bytes = min(count, sizeof(buf));
+ if (copy_from_user(&buf, p, bytes))
+ return -EFAULT;
+
+ count -= bytes;
+ p += bytes;
+
+ mix_pool_bytes(r, buf, bytes);
+ cond_resched();
+ }
+
+ return 0;
+}
+
+static ssize_t random_write(struct file *file, const char __user *buffer,
+ size_t count, loff_t *ppos)
+{
+ size_t ret;
+
+ ret = write_pool(&blocking_pool, buffer, count);
+ if (ret)
+ return ret;
+ ret = write_pool(&nonblocking_pool, buffer, count);
+ if (ret)
+ return ret;
+
+ return (ssize_t)count;
+}
+
+static long random_ioctl(struct file *f, unsigned int cmd, unsigned long arg)
+{
+ int size, ent_count;
+ int __user *p = (int __user *)arg;
+ int retval;
+
+ switch (cmd) {
+ case RNDGETENTCNT:
+ /* inherently racy, no point locking */
+ ent_count = ENTROPY_BITS(&input_pool);
+ if (put_user(ent_count, p))
+ return -EFAULT;
+ return 0;
+ case RNDADDTOENTCNT:
+ if (!capable(CAP_SYS_ADMIN))
+ return -EPERM;
+ if (get_user(ent_count, p))
+ return -EFAULT;
+ credit_entropy_bits_safe(&input_pool, ent_count);
+ return 0;
+ case RNDADDENTROPY:
+ if (!capable(CAP_SYS_ADMIN))
+ return -EPERM;
+ if (get_user(ent_count, p++))
+ return -EFAULT;
+ if (ent_count < 0)
+ return -EINVAL;
+ if (get_user(size, p++))
+ return -EFAULT;
+ retval = write_pool(&input_pool, (const char __user *)p,
+ size);
+ if (retval < 0)
+ return retval;
+ credit_entropy_bits_safe(&input_pool, ent_count);
+ return 0;
+ case RNDZAPENTCNT:
+ case RNDCLEARPOOL:
+ /*
+ * Clear the entropy pool counters. We no longer clear
+ * the entropy pool, as that's silly.
+ */
+ if (!capable(CAP_SYS_ADMIN))
+ return -EPERM;
+ input_pool.entropy_count = 0;
+ nonblocking_pool.entropy_count = 0;
+ blocking_pool.entropy_count = 0;
+ return 0;
+ default:
+ return -EINVAL;
+ }
+}
+
+static int random_fasync(int fd, struct file *filp, int on)
+{
+ return fasync_helper(fd, filp, on, &fasync);
+}
+
+const struct file_operations random_fops = {
+ .read = random_read,
+ .write = random_write,
+ .poll = random_poll,
+ .unlocked_ioctl = random_ioctl,
+ .fasync = random_fasync,
+ .llseek = noop_llseek,
+};
+
+const struct file_operations urandom_fops = {
+ .read = urandom_read,
+ .write = random_write,
+ .unlocked_ioctl = random_ioctl,
+ .fasync = random_fasync,
+ .llseek = noop_llseek,
+};
+
+SYSCALL_DEFINE3(getrandom, char __user *, buf, size_t, count,
+ unsigned int, flags)
+{
+ if (flags & ~(GRND_NONBLOCK|GRND_RANDOM))
+ return -EINVAL;
+
+ if (count > INT_MAX)
+ count = INT_MAX;
+
+ if (flags & GRND_RANDOM)
+ return _random_read(flags & GRND_NONBLOCK, buf, count);
+
+ if (unlikely(nonblocking_pool.initialized == 0)) {
+ if (flags & GRND_NONBLOCK)
+ return -EAGAIN;
+ wait_event_interruptible(urandom_init_wait,
+ nonblocking_pool.initialized);
+ if (signal_pending(current))
+ return -ERESTARTSYS;
+ }
+ return urandom_read(NULL, buf, count, NULL);
+}
+
+/***************************************************************
+ * Random UUID interface
+ *
+ * Used here for a Boot ID, but can be useful for other kernel
+ * drivers.
+ ***************************************************************/
+
+/*
+ * Generate random UUID
+ */
+void generate_random_uuid(unsigned char uuid_out[16])
+{
+ get_random_bytes(uuid_out, 16);
+ /* Set UUID version to 4 --- truly random generation */
+ uuid_out[6] = (uuid_out[6] & 0x0F) | 0x40;
+ /* Set the UUID variant to DCE */
+ uuid_out[8] = (uuid_out[8] & 0x3F) | 0x80;
+}
+EXPORT_SYMBOL(generate_random_uuid);
+
+/********************************************************************
+ *
+ * Sysctl interface
+ *
+ ********************************************************************/
+
+#ifdef CONFIG_SYSCTL
+
+#include <linux/sysctl.h>
+
+static int min_read_thresh = 8, min_write_thresh;
+static int max_read_thresh = OUTPUT_POOL_WORDS * 32;
+static int max_write_thresh = INPUT_POOL_WORDS * 32;
+static char sysctl_bootid[16];
+
+/*
+ * This function is used to return both the bootid UUID, and random
+ * UUID. The difference is in whether table->data is NULL; if it is,
+ * then a new UUID is generated and returned to the user.
+ *
+ * If the user accesses this via the proc interface, the UUID will be
+ * returned as an ASCII string in the standard UUID format; if via the
+ * sysctl system call, as 16 bytes of binary data.
+ */
+static int proc_do_uuid(struct ctl_table *table, int write,
+ void __user *buffer, size_t *lenp, loff_t *ppos)
+{
+ struct ctl_table fake_table;
+ unsigned char buf[64], tmp_uuid[16], *uuid;
+
+ uuid = table->data;
+ if (!uuid) {
+ uuid = tmp_uuid;
+ generate_random_uuid(uuid);
+ } else {
+ static DEFINE_SPINLOCK(bootid_spinlock);
+
+ spin_lock(&bootid_spinlock);
+ if (!uuid[8])
+ generate_random_uuid(uuid);
+ spin_unlock(&bootid_spinlock);
+ }
+
+ sprintf(buf, "%pU", uuid);
+
+ fake_table.data = buf;
+ fake_table.maxlen = sizeof(buf);
+
+ return proc_dostring(&fake_table, write, buffer, lenp, ppos);
+}
+
+/*
+ * Return entropy available scaled to integral bits
+ */
+static int proc_do_entropy(struct ctl_table *table, int write,
+ void __user *buffer, size_t *lenp, loff_t *ppos)
+{
+ struct ctl_table fake_table;
+ int entropy_count;
+
+ entropy_count = *(int *)table->data >> ENTROPY_SHIFT;
+
+ fake_table.data = &entropy_count;
+ fake_table.maxlen = sizeof(entropy_count);
+
+ return proc_dointvec(&fake_table, write, buffer, lenp, ppos);
+}
+
+static int sysctl_poolsize = INPUT_POOL_WORDS * 32;
+extern struct ctl_table random_table[];
+struct ctl_table random_table[] = {
+ {
+ .procname = "poolsize",
+ .data = &sysctl_poolsize,
+ .maxlen = sizeof(int),
+ .mode = 0444,
+ .proc_handler = proc_dointvec,
+ },
+ {
+ .procname = "entropy_avail",
+ .maxlen = sizeof(int),
+ .mode = 0444,
+ .proc_handler = proc_do_entropy,
+ .data = &input_pool.entropy_count,
+ },
+ {
+ .procname = "read_wakeup_threshold",
+ .data = &random_read_wakeup_bits,
+ .maxlen = sizeof(int),
+ .mode = 0644,
+ .proc_handler = proc_dointvec_minmax,
+ .extra1 = &min_read_thresh,
+ .extra2 = &max_read_thresh,
+ },
+ {
+ .procname = "write_wakeup_threshold",
+ .data = &random_write_wakeup_bits,
+ .maxlen = sizeof(int),
+ .mode = 0644,
+ .proc_handler = proc_dointvec_minmax,
+ .extra1 = &min_write_thresh,
+ .extra2 = &max_write_thresh,
+ },
+ {
+ .procname = "urandom_min_reseed_secs",
+ .data = &random_min_urandom_seed,
+ .maxlen = sizeof(int),
+ .mode = 0644,
+ .proc_handler = proc_dointvec,
+ },
+ {
+ .procname = "boot_id",
+ .data = &sysctl_bootid,
+ .maxlen = 16,
+ .mode = 0444,
+ .proc_handler = proc_do_uuid,
+ },
+ {
+ .procname = "uuid",
+ .maxlen = 16,
+ .mode = 0444,
+ .proc_handler = proc_do_uuid,
+ },
+#ifdef ADD_INTERRUPT_BENCH
+ {
+ .procname = "add_interrupt_avg_cycles",
+ .data = &avg_cycles,
+ .maxlen = sizeof(avg_cycles),
+ .mode = 0444,
+ .proc_handler = proc_doulongvec_minmax,
+ },
+ {
+ .procname = "add_interrupt_avg_deviation",
+ .data = &avg_deviation,
+ .maxlen = sizeof(avg_deviation),
+ .mode = 0444,
+ .proc_handler = proc_doulongvec_minmax,
+ },
+#endif
+ { }
+};
+#endif /* CONFIG_SYSCTL */
+
+static u32 random_int_secret[MD5_MESSAGE_BYTES / 4] ____cacheline_aligned;
+
+int random_int_secret_init(void)
+{
+ get_random_bytes(random_int_secret, sizeof(random_int_secret));
+ return 0;
+}
+
+/*
+ * Get a random word for internal kernel use only. Similar to urandom but
+ * with the goal of minimal entropy pool depletion. As a result, the random
+ * value is not cryptographically secure but for several uses the cost of
+ * depleting entropy is too high
+ */
+static DEFINE_PER_CPU(__u32 [MD5_DIGEST_WORDS], get_random_int_hash);
+unsigned int get_random_int(void)
+{
+ __u32 *hash;
+ unsigned int ret;
+
+ if (arch_get_random_int(&ret))
+ return ret;
+
+ hash = get_cpu_var(get_random_int_hash);
+
+ hash[0] += current->pid + jiffies + random_get_entropy();
+ md5_transform(hash, random_int_secret);
+ ret = hash[0];
+ put_cpu_var(get_random_int_hash);
+
+ return ret;
+}
+EXPORT_SYMBOL(get_random_int);
+
+/*
+ * randomize_range() returns a start address such that
+ *
+ * [...... <range> .....]
+ * start end
+ *
+ * a <range> with size "len" starting at the return value is inside in the
+ * area defined by [start, end], but is otherwise randomized.
+ */
+unsigned long
+randomize_range(unsigned long start, unsigned long end, unsigned long len)
+{
+ unsigned long range = end - len - start;
+
+ if (end <= start + len)
+ return 0;
+ return PAGE_ALIGN(get_random_int() % range + start);
+}
+
+/* Interface for in-kernel drivers of true hardware RNGs.
+ * Those devices may produce endless random bits and will be throttled
+ * when our pool is full.
+ */
+void add_hwgenerator_randomness(const char *buffer, size_t count,
+ size_t entropy)
+{
+ struct entropy_store *poolp = &input_pool;
+
+ /* Suspend writing if we're above the trickle threshold.
+ * We'll be woken up again once below random_write_wakeup_thresh,
+ * or when the calling thread is about to terminate.
+ */
+ wait_event_interruptible(random_write_wait, kthread_should_stop() ||
+ ENTROPY_BITS(&input_pool) <= random_write_wakeup_bits);
+ mix_pool_bytes(poolp, buffer, count);
+ credit_entropy_bits(poolp, entropy);
+}
+EXPORT_SYMBOL_GPL(add_hwgenerator_randomness);
+
+/*
+ * Experimental code to replace parts of random.c
+ * Everything from here down is new code.
+ * Sandy Harris, sandyinchina@...il.com
+ *
+ * Uses 128-bit hash from AES-GCM instead of 160-bit
+ * SHA-1. Changing the hash also allows other changes.
+ *
+ * Goals:
+ *
+ * The main design goal was improved decoupling so that
+ * heavy use of /dev/urandom does not deplete the entropy
+ * pool for /dev/random. As I see it, this is the only
+ * place where the current random(4) design is visibly
+ * flawed.
+ *
+ * Another goal was simpler mixing in of additional data
+ * in various places. This may help with the difficult
+ * problem of timely initialisation; there have been
+ * some security failures due to mis-handling of this
+ * issue. These cannot be completely dealt with in the
+ * driver, but we can do some things.
+ *
+ * I believe this code achieves both goals.
+ *
+ * The GCM hash:
+ *
+ * This sort of hash-like primitive has largely replaced
+ * more complex hashes in IPsec and TLS authentication;
+ * the new methods are often considerably faster and the
+ * code is simpler. It therefore seemed worth trying such
+ * a hash here.
+ *
+ * I chose the Galois field multiplication from AES-GCM
+ * because it is widely used, well-analysed, and
+ * considered secure. References are RFCs 4106 and 5288
+ * and NIST standard SP-800-38D.
+ *
+ * Intel and AMD both have instructions designed to
+ * make the GCM calculation faster
+ * https://en.wikipedia.org/wiki/CLMUL_instruction_set
+ * Those are not used in this proof-of-concept code
+ *
+ * https://eprint.iacr.org/2013/157.pdf discusses bugs
+ * in the Open SSL version of this hash.
+ *
+ * Whether GCM is secure for this application needs
+ * analysis. IPsec generates a 128-bit hash but uses
+ * only 96 bits, which makes some attacks much harder;
+ * this application uses all 128 bits. Also, the input
+ * for IPsec authentication is ciphertext, which is
+ * highly random with any decent cipher; input here is
+ * mainly pool data which may be much less random.
+ *
+ * Existing random(4) code folds the 160-bit SHA-1
+ * output to get an 80-bit final output; I do not
+ * consider such a transform necessary here, but that
+ * needs analysis too.
+ *
+ * I add complications beyond the basic hash; those need
+ * analysis as well.
+ *
+ * Differences from current driver:
+ *
+ * I change nothing on the input side; the whole entropy
+ * collection and estimation part of existing code, as
+ * applied to the input pool, are untouched.
+ *
+ * The hashing and output routines, though, are completely
+ * replaced. The management of output pools is also changed;
+ * they just count how many outputs since the last reseed,
+ * as a counter-mode block cipher does, rather than trying
+ * to track entropy.
+ *
+ * Mixing:
+ *
+ * Much of the mixing uses invertible functions such
+ * as the pseudo-Hadamard transform or aria_mix().
+ * These provably cannot reduce entropy; if they
+ * did, it would not be possible to invert them.
+ *
+ * As in existing code, all operations putting data
+ * into any pool are unidirectional; they use += or
+ * ^= to mix in new data so they cannot reduce the
+ * randomness of the pool, even with bad input data.
+ *
+ * I add an array of constants[], two for each pool,
+ * for use in the hashing, and a counter[] used
+ * in every output operation. All operations that
+ * put new data into those are also unidirectional.
+ *
+ * Output dependencies
+ *
+ * Every output from a normal pool (input, blocking
+ * or non-blocking) involves a GCM hash of pool
+ * contents.
+ *
+ * As well as pool data, every output depends on:
+ *
+ * two-128-bit entries from constants[] used
+ * in the hashing
+ * a global counter[] which is also hashed
+ *
+ * There is a 4th dummy pool (pool == NULL)
+ * which only hashes the counter, intended to
+ * replace the MD5 code in the current driver.
+ *
+ * There are three functions to get 128 bits,
+ * two from a specified pool p
+ *
+ * get128( p, out ) may block
+ * get_or_fail( p, out ) non-blocking
+ *
+ * get_any( out ) tries a series of sources,
+ * never blocks but does not always give a
+ * high-grade result
+ *
+ * Tests:
+ *
+ * Various tests here are deliberately more general
+ * than necessary; this protects against coding
+ * blunders, against flukes like a cosmic ray changing
+ * memory, and against misbehaviour from stressed devices
+ * like an overheated router, whether the stress is just
+ * natural or is part of an attack.
+ *
+ * For example, when a value is confidently expected
+ * to be either 0 or 1, if(x==0) ... if(x==1) ...
+ * is the obvious way to test it, but it is slightly
+ * safer to use if(x==0) ... else ... so unexpected
+ * cases can be handled. Similarly, end-of-loop tests
+ * could use x == N but x >= N is slightly safer.
+ *
+ * The value of this is arguably negligible and certainly
+ * minor, but the cost is near-zero and the behaviour
+ * is identical in all expected cases. I have therefore
+ * done this everywhere that I noticed it was possible.
+ * It would also be possible, of course, to detect and
+ * log unexpected cases, but it is not clear that this
+ * would be of much value.
+ */
+
+static spinlock_t counter_lock ;
+static spinlock_t constants_lock ;
+
+/*********************************************************
+ * unidirectional mixing operations
+ *
+ * both mix 128 bits from source into target
+ * two ways: xor or additions
+ ********************************************************/
+
+static void xor128(u32 *target, u32 *source)
+{
+#ifdef CONFIG_64BIT
+ u64 *s, *t ;
+ s = (u64 *) source ;
+ t = (u64 *) target ;
+ t[0] ^= s[0] ;
+ t[1] ^= s[1] ;
+#else
+ target[0] ^= source[0] ;
+ target[1] ^= source[1] ;
+ target[2] ^= source[2] ;
+ target[3] ^= source[3] ;
+#endif
+}
+
+/*
+ * not a 128-bit addition,
+ * just four 32-bit or two 64-bit
+ */
+static void add128(u32 *target, u32 *source)
+{
+#ifdef CONFIG_64BIT
+ u64 *s, *t ;
+ s = (u64 *) source ;
+ t = (u64 *) target ;
+ t[0] += s[0] ;
+ t[1] += s[1] ;
+#else
+ target[0] += source[0] ;
+ target[1] += source[1] ;
+ target[2] += source[2] ;
+ target[3] += source[3] ;
+#endif
+}
+
+static void add256(u32 *target, u32 *source)
+{
+#ifdef CONFIG_64BIT
+ u64 *s, *t ;
+ s = (u64 *) source ;
+ t = (u64 *) target ;
+ t[0] += s[0] ;
+ t[1] += s[1] ;
+ t[2] += s[2] ;
+ t[3] += s[3] ;
+#else
+ target[0] += source[0] ;
+ target[1] += source[1] ;
+ target[2] += source[2] ;
+ target[3] += source[3] ;
+ target[4] += source[4] ;
+ target[5] += source[5] ;
+ target[6] += source[6] ;
+ target[7] += source[7] ;
+#endif
+}
+
+/*********************************************************************
+ * Two ways to mix a 128-bit buffer, one each for 256, 512 and 1024
+ * These are generic functions that can mix anything the right size
+ * None know anything about pools or take any locks
+ *
+ * All mix in place, using no external data except buffer contents
+ * Any temporary storage used is cleared before returning
+ *********************************************************************/
+
+/*
+ * The Aria block cipher is a Korean standard
+ * Cipher home page: http://210.104.33.10/ARIA/index-e.html
+ * See also RFC 5794
+ *
+ * This application uses only the linear transform from
+ * Aria, not the whole cipher
+ *
+ * Mixes a 128-bit object treated as 16 bytes
+ * Each output byte is the XOR of 7 input bytes
+ *
+ * Some caution is needed in applying this since the
+ * function is its own inverse; using it twice on the
+ * same data gets you right back where you started
+ *
+ * Version here is based on GPL source at:
+ * http://www.oryx-embedded.com/doc/aria_8c_source.html
+ */
+static void aria_mix( u8 *x )
+{
+ u8 y[16] ;
+
+ y[0] = x[3] ^ x[4] ^ x[6] ^ x[8] ^ x[9] ^ x[13] ^ x[14];
+ y[1] = x[2] ^ x[5] ^ x[7] ^ x[8] ^ x[9] ^ x[12] ^ x[15];
+ y[2] = x[1] ^ x[4] ^ x[6] ^ x[10] ^ x[11] ^ x[12] ^ x[15];
+ y[3] = x[0] ^ x[5] ^ x[7] ^ x[10] ^ x[11] ^ x[13] ^ x[14];
+ y[4] = x[0] ^ x[2] ^ x[5] ^ x[8] ^ x[11] ^ x[14] ^ x[15];
+ y[5] = x[1] ^ x[3] ^ x[4] ^ x[9] ^ x[10] ^ x[14] ^ x[15];
+ y[6] = x[0] ^ x[2] ^ x[7] ^ x[9] ^ x[10] ^ x[12] ^ x[13];
+ y[7] = x[1] ^ x[3] ^ x[6] ^ x[8] ^ x[11] ^ x[12] ^ x[13];
+ y[8] = x[0] ^ x[1] ^ x[4] ^ x[7] ^ x[10] ^ x[13] ^ x[15];
+ y[9] = x[0] ^ x[1] ^ x[5] ^ x[6] ^ x[11] ^ x[12] ^ x[14];
+ y[10] = x[2] ^ x[3] ^ x[5] ^ x[6] ^ x[8] ^ x[13] ^ x[15];
+ y[11] = x[2] ^ x[3] ^ x[4] ^ x[7] ^ x[9] ^ x[12] ^ x[14];
+ y[12] = x[1] ^ x[2] ^ x[6] ^ x[7] ^ x[9] ^ x[11] ^ x[12];
+ y[13] = x[0] ^ x[3] ^ x[6] ^ x[7] ^ x[8] ^ x[10] ^ x[13];
+ y[14] = x[0] ^ x[3] ^ x[4] ^ x[5] ^ x[9] ^ x[11] ^ x[14];
+ y[15] = x[1] ^ x[2] ^ x[4] ^ x[5] ^ x[8] ^ x[10] ^ x[15];
+ memcpy( x, y, 16 ) ;
+ zero128( y ) ;
+}
+
+/*
+ * The pseudo-Hadamard transform (PHT) can be
+ * applied to any word size and any number of words
+ * that is a power of two. Here for 4, 8 or 16
+ * 32-bit words.
+ *
+ * In all cases it is invertible so it provably loses
+ * no entropy, and it makes every output word depend
+ * on every input word.
+ *
+ * conceptually, a 2-way PHT on a, b is
+ * x = a + b
+ * y = a + 2b
+ * a = x
+ * b = y
+ * a better implementation is just
+ * a += b
+ * b += a
+ *
+ * Larger PHTs use multiple applications of that.
+ *
+ * If you have 64-bit operations and aligned
+ * data structures, then these can be made
+ * faster. Only pht128() and add128() need to
+ * change; others just call them.
+ *
+ * If 32-bit arithmetic is used, then pht128()
+ * pht256() and pht512() are exactly the PHT
+ * on the appropriate number of 32-bit words.
+ *
+ * The 64-bit versions are not quite PHTs, but
+ * the important properties remain. They are still
+ * invertible & still make all 32-bit output words
+ * depend on all input words.
+ */
+
+static void pht128( u32 *x )
+{
+#ifndef CONFIG_64BIT
+ /*
+ * a 4-way PHT is built from 4 2-way PHTs
+ * here it is unrolled into 8 += operations
+ * each line is a two-way PHT
+ */
+ x[0] += x[1] ; x[1] += x[0] ;
+ x[2] += x[3] ; x[3] += x[2] ;
+ x[0] += x[2] ; x[2] += x[0] ;
+ x[1] += x[3] ; x[3] += x[1] ;
+#else
+ /*
+ * two 2-way 64-bit PHTs (4 += operations)
+ * and a swap of two 32-bit words
+ */
+ u32 temp ;
+ u64 *y ;
+ y = (u64 *) x ;
+ y[0] += y[1] ; y[1] += y[0] ;
+ temp = x[1]; x[1] = x[2] ; x[2] = temp ;
+ y[0] += y[1] ; y[1] += y[0] ;
+#endif
+}
+
+static void pht256( u32 *x )
+{
+ u32 *y ;
+ y = x + 4 ;
+
+ pht128(x) ;
+ pht128(y) ;
+ add128( x, y ) ;
+ add128( y, x ) ;
+}
+
+static void pht512( u32 *x )
+{
+ u32 *y ;
+ y = x + 8 ;
+
+ pht256(x) ;
+ pht256(y) ;
+ add256( x, y ) ;
+ add256( y, x ) ;
+}
+
+/*
+ * cube_mix() is from Daniel Bernstein's Cubehash
+ * It mixes 1024 bits, treated as an array of 32-bit words.
+ *
+ * based on Bernstein's code as distributed at
+ * http://bench.cr.yp.to/supercop.html
+ * He labels his code as public domain
+ *
+ * He has multiple versions. This is from the file
+ * cubehash1632/simple where 1632 indicates his main
+ * proposal (16 rounds and a 32-word state) and simple
+ * indicates the simplest code. The 1632 directory also
+ * has four different unrolled versions and over 20
+ * versions for specific hardware. There are also
+ * many other directories, so lots of options for
+ * eventual optimisations. Here I just use a simple
+ * one for proof-of-concept testing.
+ *
+ * The Cubehash algorithm has three stages:
+ *
+ * 1 put some constants into the array
+ * mix with this transform to get initial state
+ * 2 for each input block
+ * mix input into state
+ * mix with this transform
+ * 3 mix with a different transform to
+ * get an output smaller than state
+ *
+ * Here there is no stage 1 or 3 since the state we
+ * mix is already initialised and we want output of
+ * the same size. Nor is there any input data; we are
+ * not hashing here.
+ *
+ * We just use the central transform to mix a buffer.
+ */
+
+/*
+ * This is what Bernstein uses in his main proposal
+ * Arguably we need more because we lack stages 1 and 3
+ * Arguably less since this not a hash; any mixing is OK
+ */
+#define CUBEHASH_ROUNDS 16
+
+static void cube_mix( u32 *x )
+{
+ int i;
+ int r;
+ u32 y[16];
+
+ for (r = 0;r < CUBEHASH_ROUNDS;++r) {
+ for (i = 0;i < 16;++i) x[i + 16] += x[i];
+ for (i = 0;i < 16;++i) y[i ^ 8] = x[i];
+ for (i = 0;i < 16;++i) x[i] = ROTL(y[i],7);
+ for (i = 0;i < 16;++i) x[i] ^= x[i + 16];
+ for (i = 0;i < 16;++i) y[i ^ 2] = x[i + 16];
+ for (i = 0;i < 16;++i) x[i + 16] = y[i];
+ for (i = 0;i < 16;++i) x[i + 16] += x[i];
+ for (i = 0;i < 16;++i) y[i ^ 4] = x[i];
+ for (i = 0;i < 16;++i) x[i] = ROTL(y[i],11);
+ for (i = 0;i < 16;++i) x[i] ^= x[i + 16];
+ for (i = 0;i < 16;++i) y[i ^ 1] = x[i + 16];
+ for (i = 0;i < 16;++i) x[i + 16] = y[i];
+ }
+ memzero_explicit(y, 64) ;
+}
+
+/********************************************************************
+ * Code to manage the array of two 128-bit "constants" per pool
+ * These are not really constants; this code changes them
+ * They are treated as constants in the extract-from-pool code
+ *********************************************************************/
+
+/*
+ * mix one pool's constants array, two 128-bit rows
+ * in place mixing, uses no external data
+ * PHT + a rotation to make it nonlinear
+ */
+static void mix_const_p( struct entropy_store *r )
+{
+ u32 *x ;
+ unsigned long flags ;
+
+ x = r->A ;
+
+ spin_lock_irqsave( &constants_lock, flags ) ;
+ *x = ROTL( *x, 5 ) ;
+ pht256( x ) ;
+ spin_unlock_irqrestore( &constants_lock, flags ) ;
+}
+
+/*
+ * Update both constants for a pool.
+ * Needs no rotations because mix_const_p() has one
+ *
+ * Every call to this affects every hash for that pool,
+ * all future outputs from it, and all future feedback
+ * into it.
+ *
+ * This is the preferred way to rekey a pool, rather than
+ * buffer2pool() which mixes into the pool contents.
+ *
+ * This mixes in 128 bits of new data, so it is what the
+ * Yarrow paper calls "catastrophic reseeding". It resets
+ * r->count to indicate the rekeying but does not change
+ * r->entropy_count.
+ *
+ * All buffer2*() routines zero the input data after using it
+ */
+static void buffer2array( struct entropy_store *r, u32 *data )
+{
+ u32 *x;
+ unsigned long flags1, flags2 ;
+
+ x = r->A ;
+
+ spin_lock_irqsave( &r->lock, flags1 ) ;
+ spin_lock_irqsave( &constants_lock, flags2 ) ;
+ xor128( x, data ) ;
+ pht256( x ) ;
+ spin_unlock_irqrestore( &constants_lock, flags2 ) ;
+ r->count = 0 ;
+ spin_unlock_irqrestore( &r->lock, flags1 ) ;
+ zero128( data ) ;
+}
+
+/*
+ * mix the eight 128-bit constants[] for all pools
+ * in place mixing, uses no external data
+ *
+ * This uses the 1024-bit transform from Bernstein's Cubehash
+ * that has XOR, + and rotations so mixing is quite nonlinear
+ */
+static void mix_const_all( )
+{
+ unsigned long flags ;
+
+ spin_lock_irqsave( &constants_lock, flags ) ;
+ cube_mix( constants ) ;
+ spin_unlock_irqrestore( &constants_lock, flags ) ;
+}
+
+/*
+ * mix the constants[] array and both output pools
+ * all in-place mixing, no external data
+ */
+static void big_mix()
+{
+ struct entropy_store *n, *b ;
+ unsigned long flags, flags2 ;
+
+ n = &nonblocking_pool ;
+ b = &blocking_pool ;
+
+ (void) mix_const_all() ;
+
+ /*
+ * mix the output pools if possible
+ * with the default value for OUTPUT_POOL_WORDS
+ * the if here always succeeds
+ *
+ * for the >32 case, only part of pool is mixed
+ * but probably enough
+ */
+ if( OUTPUT_POOL_WORDS >= 32 ) {
+ spin_lock_irqsave( &n->lock, flags ) ;
+ cube_mix( n->pool ) ;
+ spin_unlock_irqrestore( &n->lock, flags ) ;
+
+ spin_lock_irqsave( &b->lock, flags ) ;
+ cube_mix( b->pool ) ;
+ spin_unlock_irqrestore( &b->lock, flags ) ;
+ }
+ /*
+ * the two pools combined are big enough
+ * do one mix for both
+ */
+ else if( (OUTPUT_POOL_WORDS >= 16) && (n->pool == b->pool+OUTPUT_POOL_WORDS) ) {
+ spin_lock_irqsave( &n->lock, flags ) ;
+ spin_lock_irqsave( &b->lock, flags2 ) ;
+ cube_mix( b->pool ) ;
+ spin_unlock_irqrestore( &b->lock, flags2 ) ;
+ spin_unlock_irqrestore( &n->lock, flags ) ;
+ }
+ /*
+ * this should never be reached
+ * but put in some code for safety
+ */
+ else if( OUTPUT_POOL_WORDS >= 8 ) {
+ spin_lock_irqsave( &n->lock, flags ) ;
+ pht256( n->pool ) ;
+ spin_unlock_irqrestore( &n->lock, flags ) ;
+ spin_lock_irqsave( &b->lock, flags ) ;
+ pht256( b->pool ) ;
+ spin_unlock_irqrestore( &b->lock, flags ) ;
+ }
+ /* This should definitely never be reached */
+ else pr_warn("random: strange output pool size %d\n", OUTPUT_POOL_WORDS ) ;
+}
+
+/*
+ * constants[] array has 10 128-bit rows
+ * 8 are pool constants, last 2 counter[]
+ *
+ * mix the last 4 rows
+ * 8 words in counter[]
+ * 8 words of constants[] for dummy_pool
+ *
+ * no rotations needed here; count() has enough
+ */
+static void top_mix()
+{
+ u32 *x ;
+ struct entropy_store *d ;
+ unsigned long flags1, flags2 ;
+
+ d = &dummy_pool ;
+ x = d->A ;
+
+ spin_lock_irqsave( &d->lock, flags1 ) ;
+ spin_lock_irqsave( &constants_lock, flags2 ) ;
+ pht512( x ) ;
+ spin_unlock_irqrestore( &constants_lock, flags2 ) ;
+ spin_unlock_irqrestore( &d->lock, flags1 ) ;
+}
+
+/**********************************************************************
+ * The main hashing routines, based on authenticator code from AES-GCM
+ *
+ * GCM is Galois Counter Mode
+ * All operations are in a Galois field with 128-bit elements
+ * see http://csrc.nist.gov/publications/nistpubs/800-38D/SP-800-38D.pdf
+ **********************************************************************/
+
+static u8 abits[128], ybits[128], prodbits[256] ;
+
+/*
+ * based on Dan Bernstein's AES-GCM implementation,
+ * part of CAESAR test code http://competitions.cr.yp.to/caesar.html
+ *
+ * Bernstein's description:
+ *
+ * a = (a + x) * y in the finite field
+ * 16 bytes in a
+ * xlen bytes in x; xlen <= 16; x is implicitly 0-padded
+ * 16 bytes in y
+ */
+
+static void addmul(u8 *a, const u8 *x, u32 xlen, const u8 *y)
+{
+ int i, j;
+
+ for (i = 0;i < xlen;++i)
+ a[i] ^= x[i];
+ for (i = 0;i < 128;++i)
+ abits[i] = (a[i / 8] >> (7 - (i % 8))) & 1;
+ for (i = 0;i < 128;++i)
+ ybits[i] = (y[i / 8] >> (7 - (i % 8))) & 1;
+
+ memzero_explicit( prodbits, 256 ) ;
+ for (i = 0;i < 128;++i)
+ for (j = 0;j < 128;++j)
+ prodbits[i + j] ^= abits[i] & ybits[j];
+ for (i = 127;i >= 0;--i) {
+ prodbits[i] ^= prodbits[i + 128];
+ prodbits[i + 1] ^= prodbits[i + 128];
+ prodbits[i + 2] ^= prodbits[i + 128];
+ prodbits[i + 7] ^= prodbits[i + 128];
+ prodbits[i + 128] ^= prodbits[i + 128];
+ }
+
+ zero128( a ) ;
+ for (i = 0;i < 128;++i)
+ a[i / 8] |= (prodbits[i] << (7 - (i % 8)));
+}
+
+/*
+ * Bernstein's code has prodbits[], abits[] and ybits[] as locals
+ * We make them global so this function can clear them
+ *
+ * With them as locals we could
+ * either clear them for every addmul() call (expensive)
+ * or not clear them at all (possible, though minor, security risk)
+ * better to use globals, clear them at end of sequence
+ */
+static void clear_addmul()
+{
+ memzero_explicit( prodbits, 256 ) ;
+ memzero_explicit( abits, 128 ) ;
+ memzero_explicit( ybits, 128 ) ;
+}
+
+/*
+ * Mix n bytes into an accumulator using addmul()
+ *
+ * This is a keyed hash that takes nbytes of input, a 128-bit initial value
+ * and 128-bit key (the multiplier for addmul()), and gives a 128-bit output.
+ *
+ * This routine does not either initialise the accumulator or finalise output.
+ * The expected calling sequence looks like this:
+ *
+ * intialise accumulator (from some constant)
+ * call this to mix in data (another constant is multiplier)
+ * optionally, repeat call one or more times for other data
+ * finalise output
+ *
+ * The main use here is against the various pools, replacing the hash
+ * previously used there. This should be faster and as secure, though
+ * speed needs testing & the security claim needs analysis.
+ *
+ * Note that it can be used with any data, and with a sequence of data
+ * chunks. In AES-GCM it is run over unencrypted headers so those can
+ * be authenticated along with the encrypted payload.
+ *
+ * Here it is run over counter[] as well as pool data so that outputs
+ * depend on a global piece of state, not just on one pool.
+ *
+ * It might also be run over any kernel data structure that is expected
+ * to be unpredictable to an enemy, giving extra entropy.
+ *
+ * It can also be run over anything that is expected to be different
+ *
+ * on each machine (e.g. Ethernet MACs)
+ * on each boot (clock data)
+ * or on each read of /dev/urandom (process info for reader).
+ *
+ * Such data cannot be trusted for entropy; it may be unknown to some
+ * attackers, but we cannot rely on it being unknown to all. However it
+ * can still be useful in a role like that of salt in a hash; it makes
+ * brute force or table-driven attacks much harder.
+ */
+static void mix_in( u8 *data, u32 nbytes, u8 *mul, u32 *accum)
+{
+ u32 len, left ;
+ u8 *p ;
+ for( p = data, left = nbytes ; left != 0 ; p += len, left -= len) {
+ len = (left >= 16) ? 16 : left ;
+ addmul( (u8 *) accum, p, len, mul ) ;
+ }
+}
+
+/*
+ * Start of every output routine.
+ *
+ * The Schneier et al Yarrow rng design rekeys a counter mode
+ * block cipher from its own output every 10 blocks, to avoid
+ * giving an enemy a sequence of related values to work on.
+ *
+ * Here we have feedback into any non-dummy pool on every iteration,
+ * changing 8 pool words every time. If the pool is 4K bits, 128 words,
+ * then every word is changed after 16 iterations; in a smaller pool
+ * this happens sooner. That may be all the rekeying we need, but there
+ * is some mixing of the constants here to supplement it.
+ *
+ * The dummy pool (r->pool == NULL) gets no feedback into the pool, so
+ * we mix its constants more often.
+ *
+ * This routine never requests output from any pool to drive rekeying.
+ * That overhead would be excessive in a routine that is called for
+ * every output operation from any pool.
+ *
+ * AES-GCM authentication is
+ *
+ * initialise accumulator all-zero
+ * mix in data with multiplier H
+ * xor in H before output
+ *
+ * Algorithm here is
+ *
+ * maybe mix constants r->A and r-o>B
+ * initialise accumulator from r->A
+ * mix in data with multiplier r->B
+ * counter[] for any pool
+ * pool data for non-dummy pools
+ * xor in r->B
+ *
+ * That finishes the first hash. For the dummy pool, we stop
+ * there and use that output.
+ *
+ * Some constants, both primes from list at:
+ * https://primes.utm.edu/lists/small/10000.txt
+ *
+ * ADJUST THESE FOR TUNING
+ * To test, I just use the first primes > 10, 100
+ *
+ * FREQUENCY how often to mix constants for most pools
+ * FREQDUMMY for dummy pool
+ */
+
+#define FREQUENCY 101
+#define FREQDUMMY 11
+
+static void mix_first( struct entropy_store *r, u32 *accum )
+{
+ u32 x ;
+ unsigned long flags ;
+
+ spin_lock_irqsave( &r->lock, flags ) ;
+ x = r->count++ ;
+ spin_unlock_irqrestore( &r->lock, flags ) ;
+
+ /*
+ * sometimes mix constants before using them
+ * do not zero the count
+ * only buffer2array() does that
+ */
+ if( r->pool != NULL) {
+ if( (x%FREQUENCY) == 0 )
+ mix_const_p( r ) ;
+ }
+ else {
+ if( (x%FREQDUMMY) == 0 )
+ mix_const_p( r ) ;
+ }
+
+ /* initialise the accumulator */
+ memcpy( (u8 *) accum, (u8 *) r->A, 16 ) ;
+
+ /* mix in the counter and update it */
+ addmul( (u8 *) accum, (u8 *) counter, 16, (u8 *) r->B) ;
+ count() ;
+
+ /* for non-dummy pools, mix in pool data */
+ if( r->pool != NULL )
+ mix_in( (u8 *) r->pool, r->size, (u8 *) r->B, accum ) ;
+
+ /*
+ * finalise result
+ * it depends on at least r->A, r->B and counter[]
+ * for non-dummy pools, on pool contents as well
+ */
+ xor128( accum, r->B ) ;
+
+ clear_addmul() ;
+}
+
+/*
+ * Last function in mixing sequence for any of 3 real pools
+ * Not used for dummy pool
+ *
+ * No locking needed in this function
+ * Caller need not hold locks either, & should not
+ *
+ * First, put feedback into the pool
+ *
+ * save a copy of the 1st hash's result
+ * feed the result back into pool
+ *
+ * Then do 2nd hash to get output different from the feedback
+ *
+ * re-initialise accumulator from r->B
+ * mix in saved data with multiplier r->A
+ * xor in data to get output
+ *
+ * The constants are used differently in the two hashes. In
+ * mix_first(), A is the initialiser and B the multiplier.
+ * In the second hash here, they swap roles.
+ *
+ * In the first hash, the same constant is used twice, first
+ * as the muiltipler in finite field multiplication then in
+ * an XOR. This is exactly the way that AES-GCM uses its
+ * constant H.
+ *
+ * AES-GCM has: hash( data, all-0, H ) xor H
+ * our 1st hash: hash( data, A, B ) xor B
+ * our 2nd hash: hash( data, B, A ) xor data
+ *
+ * A well-known paper on building hashes from block ciphers,
+ * pretty much the standard reference on the topic, is:
+ * Preneel, Govaerts & Vandewalle
+ * https://www.cosic.esat.kuleuven.be/publications/article-48.ps
+ *
+ * It shows that some structures resist backtracking.
+ * They consider 64 possibilities and show that exactly
+ * 12 of them are secure. Both hashes here use structures
+ * from among that 12.
+ */
+
+static void mix_last( struct entropy_store *r, u32 *accum )
+{
+ u32 temp[4] ;
+
+ /*
+ * for the dummy pool, this should not be called
+ * if it is, there is nothing to do here
+ */
+ if( r->pool == NULL ) {
+ pr_warn("random: mix_last() called for dummy pool\n" ) ;
+ return ;
+ }
+
+ /*
+ * for any other pool, continue
+ * save result for use in generating output
+ */
+ memcpy( temp, accum, 16 ) ;
+
+ /* feed intermediate result back into pool */
+ buffer2pool( r, accum ) ;
+
+ /*
+ * Apply another hash step to the saved value in temp[]
+ * to create an output different from feedback
+ */
+ memcpy( accum, r->B, 16 ) ;
+ addmul( (u8 *) accum, (u8 *) temp, 16, (u8 *) r->A) ;
+ xor128( accum, temp ) ;
+
+ clear_addmul() ;
+ zero128( temp ) ;
+}
+
+/*
+ * Input pool rekeys from external data and maybe hardware rng
+ * Blocking pool rekeys from the input pool before every output
+ * Dummy pool gets its constants changed when top_mix() is used.
+ *
+ * In mix_first() all pools sometimes mix their own constants
+ * and in mix_last() all non-dummy pools get feedback applied
+ * to their pool data. All pools are affected by the counter[]
+ * and by mix_const_all().
+ *
+ * The only place where rekeying needs more complex management
+ * is for the nonblocking pool
+ *
+ * The blocking pool generates only one /dev/random output
+ * each time it is reseeded. It appears safe to generate
+ * additional outputs to reseed the nonblocking pool; there is
+ * good mixing there so blocking pool output is not exposed to
+ * attack by this, except in a remarkably indirect way.
+ *
+ * The blocking pool is reseeded whenever /dev/random is
+ * used, so if it is used often, then the nonblocking pool
+ * will almost always be able to safely reseed from there.
+ *
+ * How many outputs can we safely take from a seeded pool?
+ * ======================================================
+ *
+ * Too large a value will be insecure, but it is not clear what
+ * "too large" means here. The question has been well studied
+ * for counter mode block ciphers, but the analysis does not
+ * apply directly here; at best it allows sensible guesses.
+ *
+ * For n-bit block size the Yarrow paper shows a generic attack
+ * for any counter mode block cipher after 2^(n/3) output blocks,
+ * about 2^42 for 128-bit block size, and one NIST document
+ * suggests an absolute upper limit of 2^48 for AES-CTR.
+ *
+ * Real applications generally use a much lower limit. Here I
+ * think a value for SAFE_OUT around 2^16 is the largest that
+ * could reasonably be considered, perhaps the prime (2^16)+1.
+ *
+ * However, using that seems unnecessary; a much lower value
+ * is enough to effectively decouple /dev/urandom and /devrandom.
+ * We want a low enough value that going over it sometimes when
+ * entropy is low will not be fatal.
+ *
+ * Even if /dev/random is not used, the nonblocking pool can reseed
+ * from the blocking pool SAFE_OUT times before it needs to reseed
+ * from a hardware rng or the input pool. Since it does SAFE_OUT
+ * output blocks per reseed, it can produce SAFE_OUT*SAFE_OUT blocks
+ * before it needs to reseed other than from the blocking pool.
+ *
+ * Using primes (just because), some possibilities are:
+ *
+ * with SAFE_OUT = 31, almost 1,000 blocks
+ * with SAFE_OUT = 101, over 10,000 blocks
+ * with SAFE_OUT = 331, over 100,000 blocks
+ * with SAFE_OUT = 503, over 250,000 blocks
+ * with SAFE_OUT = 1009, over 1,000,000 blocks
+ * with SAFE_OUT = (2^16)+1, over 2^32 blocks
+ *
+ * Any sensible value for SAFE_OUT will greatly reduce load on the
+ * input pool when the nonblocking pool is heavily used.
+ */
+
+#define SAFE_OUT 503
+
+/* constants to test input pool entropy level */
+#define E_MINIMUM 1024
+#define E_PLENTY (INPUT_POOL_WORDS*24)
+
+/*
+ * try to get 128 bits from a pool
+ * return 1 for success, 0 for failure
+ */
+static int get_or_fail( struct entropy_store *r, u32 *out )
+{
+ int got ;
+ u32 temp[4] ;
+ unsigned long flags ;
+
+ if( r == &input_pool ) {
+ spin_lock_irqsave( &r->lock, flags ) ;
+ if( (got = (ENTROPY_BITS(r) > E_MINIMUM)) )
+ credit_entropy_bits( r, -128 ) ;
+ spin_unlock_irqrestore( &r->lock, flags ) ;
+ if( got ) {
+ mix_first( r, out ) ;
+ mix_last( r, out ) ;
+ return 1 ;
+ }
+ else return 0 ;
+ }
+ else if( (r == &blocking_pool) || (r == &nonblocking_pool) ) {
+ /*
+ * need not lock here
+ * going slightly over SAFE_OUT is not dangerous
+ */
+ if( r->count < SAFE_OUT ) {
+ mix_first( r, out ) ;
+ mix_last( r, out ) ;
+ return 1 ;
+ }
+ else return 0 ;
+ }
+ /*
+ * dummy pool always succeeds
+ * but may need rekeying first
+ */
+ else if( r == &dummy_pool) {
+ if( r->count >= SAFE_OUT ) {
+ get_any( temp ) ;
+ buffer2array( r, temp ) ;
+ }
+ mix_first( r, out ) ;
+ return 1 ;
+ }
+ else {
+ pr_warn("random: get_or_fail() gets bad pool argument\n" ) ;
+ return 0 ;
+ }
+}
+
+/*
+ * get 128 bits from somewhere
+ * always succeeds, but may not always give good data
+ *
+ * return value indicates data source
+ * 1 = input, 2 = blocking, 3 = nonblocking
+ * 4 = dummy, 5 = hw rng
+ */
+static int get_any( u32 *out )
+{
+ int got ;
+ struct entropy_store *r ;
+ unsigned long flags ;
+
+ /*
+ * use the input pool if it has plenty
+ * of entropy
+ *
+ * unlike get_or_fail(), this function
+ * does not test for > E_MINIMUM
+ * so it avoids depleting input entropy
+ * except when there is plenty
+ */
+ r = &input_pool ;
+ spin_lock_irqsave( &r->lock, flags ) ;
+ if( (got = (ENTROPY_BITS(r) > E_PLENTY)) )
+ credit_entropy_bits( r, -128 ) ;
+ spin_unlock_irqrestore( &r->lock, flags ) ;
+ if( got ) {
+ mix_first( r, out ) ;
+ mix_last( r, out ) ;
+ return 1 ;
+ }
+
+ /*
+ * this is likely to be the most common case
+ * & should usually succeed
+ */
+ if( get_or_fail( &blocking_pool, out ) )
+ return 2 ;
+
+ /*
+ * hw rng may not be fully trusted,
+ * but it is fine as a fallback here
+ */
+ if( get_hw_random( out ) ) {
+ /*
+ * if we reach here, hw rng works
+ * but input pool is not close to full
+ * so try to refill it
+ */
+ load_input() ;
+ return 5 ;
+ }
+
+ /* reaching here should be rare; do what we can */
+ if( get_or_fail( &nonblocking_pool, out ) )
+ return 3 ;
+
+ /* dummy pool always succeeds */
+ get128( &dummy_pool, out ) ;
+ return 4 ;
+}
+
+/*
+ * get 128 bits from a pool
+ * for input or blocking pool, this may block
+ * for dummy or nonblocking, it will not
+ */
+
+static u32 rekey_flip_flop = 0 ;
+
+static void get128( struct entropy_store *r, u32 *out )
+{
+ u32 temp[4] ;
+ unsigned long flags ;
+
+ /*
+ * get_or_fail( r, out ) cannot be used here
+ * pool must be rekeyed before output
+ */
+ if( r == &blocking_pool ) {
+ /*
+ * try non-blocking function first
+ * if it fails, use blocking function
+ */
+ if( !get_or_fail( &input_pool, temp ) )
+ get128( &input_pool, temp ) ;
+ /*
+ * one way or the other, we have data, so reseed
+ * r->count is reset in buffer2array()
+ */
+ buffer2array( r, temp ) ;
+
+ /* produce output */
+ mix_first( r, out ) ;
+ mix_last( r, out ) ;
+ return ;
+ }
+
+ /*
+ * for any pool except blocking
+ * see if pool is ready for output
+ * dummy pool is always ready
+ */
+ if( get_or_fail( r, out) ) {
+ return ;
+ }
+
+ /*
+ * nonblocking pool not ready
+ * rekey it, without blocking
+ */
+ if( r == &nonblocking_pool ) {
+ /*
+ * First choice is to rekey from blocking pool
+ * This should very often succeed
+ * else non-blocking function that always succeeds
+ */
+ if( !get_or_fail(&blocking_pool, temp) )
+ (void) get_any( temp ) ;
+ /*
+ * one way or the other, we have data, so reseed
+ * r->count is reset in buffer2array()
+ */
+ buffer2array( r, temp ) ;
+ /*
+ * Do some extra mixing
+ *
+ * Rekeying is infrequent enough (once
+ * every SAFE_OUT blocks) that we can
+ * afford a somewhat expensive mix here
+ *
+ * constants[] has 10 128-bits rows
+ * 8 for pool constants, 2 for counter[]
+ *
+ * mix_const_all() mixes first 8 rows
+ * top_mix() mixes last 4
+ * they overlap so all 10 get mixed
+ * if both are used
+ */
+ if( rekey_flip_flop ) {
+ /*
+ * Mix all the pool constants
+ * so the rekey affects all pools
+ * This is the only full mix except
+ * during initialisation
+ */
+ mix_const_all() ;
+ rekey_flip_flop = 0 ;
+ }
+ else {
+ /*
+ * mix counter[]
+ * and constants for dummy pool
+ */
+ top_mix() ;
+ rekey_flip_flop = 1 ;
+ }
+
+ /* produce output */
+ mix_first( r, out ) ;
+ mix_last( r, out ) ;
+ return ;
+ }
+
+ if( r == &input_pool ) {
+ /* pool entropy is low, so try hw rng */
+ if( !load_input() ) {
+ /* no hw rng, toss in something */
+ (void) get_any( temp ) ;
+ buffer2pool( r, temp ) ;
+ }
+
+ /*
+ * ADD CODE HERE
+ * adapt code from current driver
+ * needs to block sometimes
+ * and deal with entropy_count
+ */
+ spin_lock_irqsave( &r->lock, flags ) ;
+ credit_entropy_bits( r, -128 ) ;
+ spin_unlock_irqrestore( &r->lock, flags ) ;
+
+ /* produce output */
+ mix_first( r, out ) ;
+ mix_last( r, out ) ;
+ return ;
+ }
+}
+
+/*****************************************************************
+ * loop to fill an output buffer with data
+ * for input or blocking pool, this may block
+ *****************************************************************/
+
+static void loop_output( struct entropy_store *r, u32 *out, u32 nbytes )
+{
+ u32 temp[4] ;
+ int n, m ;
+ u8 *p ;
+
+ /*
+ * for pools that may block, try to avoid it
+ * fill input pool from hw rng if available
+ */
+ if( got_hw_rng && ((r == &input_pool) || (r==&blocking_pool)) )
+ load_input() ;
+
+ /*
+ * Ensure that each call to this function will start
+ * a new output stream which is almost independent
+ * of previous streams. For a rationale, see the
+ * Fortuna paper by Schneier et al.
+ */
+ counter_any() ;
+
+ /*
+ * ADD CODE HERE?
+ *
+ * For /dev/urandom accesses, we could mix in process
+ * info for the reading process, just apply addmul()
+ * to task_info struct to mix it into counter[] or
+ * into the constants
+ *
+ * This depends on a different aspect of the system than
+ * anything else in the driver, namely the order in which
+ * user processes ask for data and the current state of
+ * those processes.
+ *
+ * Except perhaps on simple embedded systems, this should
+ * be hard to guess. It should be impossible to monitor
+ * unless the attacker is logged into the system or has
+ * left a background process running on it. Even then,
+ * monitoring it would not be easy.
+ */
+
+ for( n = nbytes, p = (u8 *) out ; n > 0 ; n -= m, p += m ) {
+ m = (n >= 16) ? 16 : n ;
+ get128( r, temp ) ;
+ memcpy( p, (u8 *) temp, m) ;
+ }
+ zero128( temp ) ;
+}
+
+/******************************************************************
+ * Mixing into pool data
+ *
+ * This routine is used only to mix data into the pool itself,
+ * for feedback in mix_last()
+ *
+ * Output operations from any pool use the hashing parts of
+ * mix_last(), not this code.
+ *
+ * For rekeying, buffer2array() is preferred over this; change a
+ * constant rather than pool data. The effects are more easily
+ * analysed, and more general since changing a constant always
+ * affects the pool but not vice versa.
+ *
+ * Use this only for data known to be (or at least appear)
+ * highly random
+ *
+ * hardware RNG data
+ * hash output
+ * cipher output (not used here)
+ *
+ * Input mixing should NOT use this; existing driver code is far
+ * better for low-to-medium entropy inputs. Existing code is OK
+ * for high-entropy inputs as well, though it appears to have been
+ * designed for the low entropy case.
+ *
+ * I added this in hopes it would be faster, and easier to analyze
+ * in the high-entropy case. Also, using two different mixers gives
+ * insurance if either has some unknown weakness.
+ *******************************************************************/
+
+/*
+ * Mix a 128-bit buffer into a pool, changing 8 32-bit pool words
+ * All buffer2*() routines zero the input data after using it
+ *
+ * This does not reset r->count; only buffer2array() does that
+ * Nor does it change r->entropy_count
+ *
+ * Eventually this stirs the entire pool, making every pool word
+ * depend both on every other pool word and on many external inputs.
+ * This is the only stirring the output pools get, except during
+ * initialisation.
+ */
+static void buffer2pool( struct entropy_store *r, u32 *buff)
+{
+ u32 *a, *b ;
+ unsigned long flags ;
+
+ /* normal case, real pool */
+ if( r->pool != NULL ) {
+ spin_lock_irqsave( &r->lock, flags ) ;
+ a = r->p ;
+ b = r->q ;
+ /* mix a[] and add new data */
+ a[0] = ROTL( a[0], 5 ) ;
+ xor128( a, buff ) ;
+ pht128( a ) ;
+ /* mix b[] */
+ aria_mix( (u8 *) b ) ;
+ /* PHTs between rows */
+ add128( a, b ) ;
+ add128( b, a ) ;
+ /* update pointers */
+ r->p += 4 ;
+ if( r->p >= r->end )
+ r->p = r->pool ;
+ r->q += 4 ;
+ if( r->q >= r->end )
+ r->q = r->pool ;
+ spin_unlock_irqrestore( &r->lock, flags ) ;
+ zero128( buff ) ;
+ }
+ /*
+ * if called for dummy pool, which should not happen
+ * there is no pool to mix to
+ * so mix to constants instead
+ */
+ else {
+ buffer2array( r, buff ) ;
+ pr_warn("random: buffer2pool() called for dummy pool\n" ) ;
+ }
+}
+
+/*********************************************************
+ * initialise counter & output pools
+ *
+ * This should not be done until there is enough (256 bits?)
+ * entropy in the input pool.
+ *
+ * This code does not deal with that problem!
+ * FIX BEFORE USING
+ ********************************************************/
+
+/* how many 128-bit chunks to mix into a pool */
+#define HOW_MANY 4
+
+static void init_random()
+{
+ u32 temp[4], *x, *y ;
+ int j ;
+ struct entropy_store *i, *b, *n, *d ;
+ ktime_t now ;
+
+ i = &input_pool ;
+ b = &blocking_pool ;
+ n = &nonblocking_pool ;
+ d = &dummy_pool ;
+
+ spin_unlock( &counter_lock ) ;
+ spin_unlock( &constants_lock ) ;
+
+ /*
+ * fill input pool from hardware rng if possible
+ * if that works, mix hw data into constants as well
+ */
+ if( load_input() )
+ (void) load_constants() ;
+
+ /*
+ * ADD CODE HERE?
+ *
+ * If data from kernel command line is available,
+ * mix it into counter[] or input pool before doing
+ * anything else. Either way, it will then affect
+ * all future operations
+ *
+ * Simplest: XOR 256 bits into 8 words of counter[]
+ * or with exactly 128, call buffer2counter()
+ */
+
+ mix_first( i, temp ) ;
+
+ /*
+ * Existing code to get data for the input pool uses timer
+ * information. So do programs like my maxwell(8), Stephan
+ * Mueller's jitter driver or Havege. Most of my code here
+ * therefore does not use timings since that entropy is
+ * already accounted for. There are two exceptions:
+ *
+ * buffer2counter() mixes in jiffies
+ *
+ * Here timer info is added so initialisation is a bit
+ * different each time. Nowhere near enough entropy
+ * to make things secure by itself, but better than
+ * nothing.
+ */
+ now = ktime_get_real() ;
+ mix_in( (u8 *) &now, sizeof(now), (u8 *) i->B, temp) ;
+
+ mix_in( (u8 *) utsname(), sizeof(*(utsname())), (u8 *) i->B, temp) ;
+
+ /*
+ * ADD CODE HERE
+ *
+ * Mix static info into temp[]
+ * things that can act as salt
+ *
+ * These need not be unpredictable
+ * just different on different systems
+ * e.g. ethernet MAC, other hardware info.
+ *
+ * Existing code uses utsname(). That and if
+ * possible more should be added here.
+ */
+
+ mix_last( i, temp ) ;
+
+ /*
+ * Use that first result to re-initialise the counter
+ * This will affect all future outputs from any pool
+ *
+ * Provided enough entropy is present before this,
+ * from any of:
+ * data in random_init.h
+ * kernel command line
+ * input to pool before this runs
+ * this makes the counter unknowable to an enemy
+ *
+ * All future outputs, including the ones that
+ * rekey pools below, depend on the counter
+ */
+ buffer2counter( temp ) ;
+
+ /*
+ * mix data into the output pools
+ * try to get from input pool first
+ * else from dummy pool which never blocks
+ *
+ * don't use get_any() yet; its only advantage
+ * over just using dummy pool is that it might
+ * get from output pools, but that is much more
+ * expensive and output pools are not fully
+ * initialised yet
+ */
+ for( j = 0, x=n->pool, y=b->pool ; j < HOW_MANY ; j++, x+=4, y+=4 ) {
+ if( !get_or_fail(i, temp) )
+ get128( d, temp) ;
+ spin_lock( &n->lock) ;
+ xor128( x, temp ) ;
+ spin_unlock( &n->lock) ;
+ spin_lock( &b->lock) ;
+ add128( y, temp ) ;
+ spin_unlock( &b->lock) ;
+ }
+ /* now get_any() and constants_any() can safely be used */
+
+ /*
+ * refill input pool from hardware rng if possible
+ * if that works, mix hw data into constants as well
+ */
+ if( load_input() ) {
+ (void) load_constants() ;
+ }
+ else {
+ /*
+ * update counter[] and constants for dummy pool
+ * before using them
+ */
+ top_mix() ;
+ /*
+ * mix pseudorandom bits into input pool
+ * use cheap non-blocking source, dummy pool
+ */
+ for( j = 0, x=i->pool ; j < HOW_MANY ; j++, x+=4 ) {
+ get128( d, temp ) ;
+ add128( x, temp ) ;
+ }
+ /*
+ * mix random data into constants[]
+ * use best available data
+ */
+ (void) get_any( temp ) ;
+ buffer2array( i, temp );
+ (void) get_any( temp ) ;
+ buffer2array( n, temp );
+ (void) get_any( temp ) ;
+ buffer2array( b, temp );
+ (void) get_any( temp ) ;
+ buffer2array( d, temp );
+ }
+ /* Mix constants[] and both output pools */
+ big_mix() ;
+
+ /* output should use a different counter[] value */
+ counter_any() ;
+}
+
+/*****************************************************************
+ * 128-bit counter to mix in when hashing
+ *
+ * There is only one counter[] and three functions to update it,
+ * count() to iterate it, buffer2counter() or counter_any()
+ * to re-initialise it with a new starting value
+ *
+ * mix_first() uses counter[] and calls count(), so the count both
+ * affects and is affected by all output operations on any pool.
+ *
+ * Operations on this counter do not affect the per-pool counts
+ * for any pool, neither the entropy count nor the r->count
+ * iteration counter.
+ *
+ * One reason for including the counter is that it allows fast
+ * initialisation. The very first output from the input pool is
+ * used to update the counter. Once that is done, even if the
+ * pools were all worthless, every output operation would still
+ * have at least the strength of hash(constants, counter) which
+ * is very roughly equivalent to a counter mode block cipher
+ * encrypt(key,counter).
+ *
+ * mix_first() mixes in the counter so it affects all output from
+ * any pool and all feedback into any pool. Every operation on any
+ * pool changes the counter, so it automatically influences all the
+ * other pools, albeit in an indirect and quite limited way.
+ *
+ * This can contribute to recovery after an rng state compromise.
+ * Even knowing the counter value at one time an enemy cannot infer
+ * the future effects unless he can predict the order of future
+ * output operations, which depends on data requests from all sources.
+ * Nor can he work backwards to get previous outputs unless he knows
+ * the order of previous operations.
+ *
+ * This may provide almost no protection on a simple embedded system
+ * or over a very short time span, since in those cases an enemy
+ * might guess the sequence of operations or search through some
+ * moderate number of possibilties. However it should be quite
+ * effective for more complex systems and longer time spans.
+ ****************************************************************/
+
+static u32 iter_count = 0 ;
+static u32 loop_count = 0 ;
+
+/*
+ * 41 times 251 iterations per loop
+ * gives about 10,000 outputs before auto-rekey
+ */
+#define MAX_LOOPS 41
+
+/* constant from SHA-1 */
+#define COUNTER_DELTA 0x67452301
+
+/*
+ * Code is based on my own work in the Enchilada cipher:
+ * https://aezoo.compute.dtu.dk/doku.php?id=enchilada
+ * That implements a 128-bit counter in 4 32-bit words
+ *
+ * Here counter[] is declared as 8 words; the others
+ * are used only during updates, in buffer2counter()
+ *
+ * Add a constant instead of just incrementing, and include some
+ * other operations, so Hamming weight changes more than for a
+ * simple counter. Mix +, XOR and rotation so it is nonlinear.
+ *
+ * This may not be strictly necessary, but a simple counter can
+ * be considered safe only if you trust the crypto completely.
+ * Low Hamming weight differences in inputs do allow some attacks
+ * on block ciphers or hashes and the high bits of a large counter
+ * that is only incremented do not change for aeons.
+ *
+ * The extra code here is cheap insurance.
+ *
+ * For discussion, see mailing list thread starting at:
+ * http://www.metzdowd.com/pipermail/cryptography/2014-May/021345.html
+ */
+
+static void count(void)
+{
+ int reseed ;
+ unsigned long flags ;
+
+ /*
+ * There should be enough other rekeying that
+ * this is quite rare. This is just here for
+ * safety, much as IPsec rekeys after 2^32
+ * blocks if no other rekeying is done.
+ */
+ spin_lock_irqsave( &counter_lock, flags ) ;
+ reseed = (loop_count >= MAX_LOOPS) ;
+ spin_unlock_irqrestore( &counter_lock, flags ) ;
+ if( reseed )
+ counter_any() ;
+
+ spin_lock_irqsave( &counter_lock, flags ) ;
+
+ /*
+ * Limit the switch to < 256 cases
+ * should work with any CPU & compiler
+ *
+ * Five constants used, all primes
+ * roughly evenly spaced, around 50, 100, 150, 200, 250
+ */
+ switch( iter_count ) {
+ /*
+ * mix three array elements
+ * each element is used twice
+ * once on left, once on right
+ * pattern is circular
+ * order chosen for fast mixing
+ */
+ case 47:
+ counter[1] += counter[3] ;
+ break ;
+ case 101:
+ counter[2] += counter[1] ;
+ break ;
+ case 197:
+ counter[3] += counter[2] ;
+ break ;
+ /*
+ * inject counter[0] into that loop
+ * the loop and counter[0] use +=
+ * so use ^= here
+ *
+ * inject into counter[2]
+ * so case 197 starts spreading the effect
+ */
+ case 149:
+ counter[2] ^= counter[0] ;
+ break ;
+ /*
+ * restart loop
+ * throw in rotations for nonlinearity
+ */
+ case 251:
+ counter[1] = ROTL( counter[1], 3) ;
+ counter[2] = ROTL( counter[2], 7) ;
+ counter[3] = ROTL( counter[3], 13) ;
+ iter_count = 0 ;
+ loop_count++ ;
+ break ;
+ /*
+ * for 247 out of every 252 iterations
+ * the switch does nothing
+ */
+ default:
+ break ;
+ }
+ /*
+ * counter[0] is purely a counter
+ * nothing above affects it
+ * uses += instead of ++ to change Hamming weight more
+ *
+ * would repeat after 2^32 iterations
+ * not a problem since the rest of counter[] changes too
+ * and 2^32 will not be reached
+ */
+ counter[0] += COUNTER_DELTA ;
+ iter_count++ ;
+
+ spin_unlock_irqrestore( &counter_lock, flags ) ;
+}
+
+/*
+ * code to set a new counter value
+ *
+ * All buffer2*() routines
+ * expect 128 bits of input
+ * zero the input data after using it
+ */
+static void buffer2counter( u32 *data )
+{
+ unsigned long flags ;
+
+ spin_lock_irqsave( &counter_lock, flags ) ;
+ /*
+ * timing data is used elsewhere in driver
+ * and we do not want an expensive operation
+ * here, so use simplest thing that makes
+ * every call different
+ */
+ counter[0] ^= jiffies ;
+ /*
+ * mix all 8 words in counter[] array
+ * this and top_mix() are the only things
+ * that change the high 4 words
+ */
+ pht256( counter ) ;
+ /*
+ * input data mixed into low 4 words of counter[]
+ * which are the actual 128-bit counter
+ *
+ * high 4 words are multiplier in GCM mixing
+ * this is the only place they are used
+ */
+ addmul( (u8 *) counter, (u8 *) data, 16, (u8 *) (counter+4) ) ;
+ /*
+ * make the mixing non-invertible
+ * see reference to Preneel et al. in comment for mix_last()
+ */
+ xor128( counter, data ) ;
+
+ loop_count = 0 ;
+ iter_count = 0 ;
+
+ spin_unlock_irqrestore( &counter_lock, flags ) ;
+
+ zero128( data ) ;
+ clear_addmul() ;
+}
+
+static void counter_any( )
+{
+ u32 temp[4] ;
+ (void) get_any( temp ) ;
+ buffer2counter( temp ) ;
+}
+
+/****************************************************************
+ * Code to deal with hardware RNG, if any
+ *
+ * get_hw_random() just puts 128 bits from hw rng in a buffer
+ *
+ * load_input() makes sure that, if we have a hardware rng, then the
+ * input pool is well supplied with data
+ *
+ * Absent an rng instruction, these functions would be the logical
+ * place to add data from something else, such as a hardware rng
+ * accessed via a driver rather than an instruction (Turbid, or an
+ * on-board or plug-in device) or something using timing data such
+ * as Havege or Stephan Mueller's jitter. There is no code for that
+ * here yet.
+ *
+ * Both get_hw_random() and load_input() set got_hw_rng and return
+ * a value for success/failure. If all arch_get_random_long() calls
+ * succeed, both got_hw_rng and the return are 1; if any call fails
+ * both are 0
+ *
+ * Code calling those functions can either check got_hw_rng and
+ * avoid the call if it is 0 or just make the call unconditionally
+ * and let the function set got_hw_rng.
+ ***********************************************************************/
+
+/*
+ * How much do we trust the hardware?
+ * 0-32 for entropy credit per 32-bit word
+ *
+ * arbitrary number here for testing
+ * NEEDS TO BE SET MORE CAREFULLY
+ * may need #ifdef for architecture-specific value
+ */
+#define TRUST32 25
+
+/*
+ * check for out-of-bounds values, allowing only values 1-31
+ * a value of 0 would be senseless
+ * 32 is too trusting for any real device
+ */
+#if (TRUST32 < 1) || (TRUST32 > 31)
+#error Out-of-bounds setting for TRUST32
+#endif
+
+/*
+ * fill a 128-bit buffer with hw rand data
+ * only used by routines in this section
+ * other code calls those, not this, since
+ * the higher-level routines do more
+ */
+static inline int hw2buff( u32 *out )
+{
+ int i ;
+ unsigned long *p ;
+
+ for( i = 0, p = (unsigned long *) out ; i < 4 ; i++, p++ )
+ if( !arch_get_random_long( p ) )
+ return 0 ;
+ return 1 ;
+}
+
+/* put 128 bits into a buffer, set got_hw_rng */
+static int get_hw_random( u32 *out )
+{
+ int ret ;
+ ret = hw2buff( out ) ;
+ got_hw_rng = ret ;
+ return ret ;
+}
+
+/* (approximately) fill the input pool with hw rng data */
+
+static u32 *next_word = pools ;
+
+static int load_input()
+{
+ struct entropy_store *r ;
+ u32 temp[4], *end_buffer ;
+ int i, n, ret, limit, e_count ;
+ unsigned long x, flags ;
+
+ r = &input_pool ;
+
+ /*
+ * deliberately somewhat imprecise calculation
+ * we need not exactly fill the pool
+ *
+ * no lock here; we are just reading values
+ * and an error will not do real harm
+ */
+ n = (r->poolinfo->poolbits - ENTROPY_BITS(r)) / 128 ;
+
+ /*
+ * if pool is not full
+ * loop to put data into the pool itself
+ * this does need the lock
+ */
+ if( n > 0 ) {
+ limit = n*4 ;
+ end_buffer = r->pool + INPUT_POOL_WORDS ;
+ spin_lock_irqsave( &r->lock, flags ) ;
+ for( i = e_count = 0, ret = 1 ; ret && (i<limit) ; i++, next_word++ ) {
+ if( next_word >= end_buffer )
+ next_word = r->pool ;
+ if( (ret = arch_get_random_long( &x )) ) {
+ *next_word ^= x ;
+ e_count += TRUST32 ;
+ }
+ }
+ credit_entropy_bits( r, e_count ) ;
+ spin_unlock_irqrestore( &r->lock, flags ) ;
+ }
+ /*
+ * if pool is near full, change its constants
+ * no loop, just do 128 bits
+ */
+ else if( (ret = hw2buff(temp)) ) {
+ buffer2array( r, temp ) ;
+ }
+ got_hw_rng = ret ;
+ return ret ;
+}
+
+/* update all constants with data from hw rng if possible */
+static int load_constants()
+{
+ int i, ret ;
+ u32 *p ;
+ unsigned long x, flags ;
+
+ spin_lock_irqsave( &constants_lock, flags ) ;
+ for( i = 0, p = constants, ret = 1 ; ret && (i < ARRAY_WORDS) ; i++, p++ ) {
+ if( (ret = arch_get_random_long( &x )) )
+ *p ^= x ;
+ }
+ spin_unlock_irqrestore( &constants_lock, flags ) ;
+ got_hw_rng = ret ;
+ return ret ;
+}
--
2.5.0
--
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