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Message-ID: <6266306.8u6rsYMSBi@positron.chronox.de>
Date: Tue, 03 May 2016 10:50:25 +0200
From: Stephan Mueller <smueller@...onox.de>
To: Theodore Ts'o <tytso@....edu>
Cc: linux-kernel@...r.kernel.org, herbert@...dor.apana.org.au,
andi@...stfloor.org, sandyinchina@...il.com,
cryptography@...edaemon.net, jsd@...n.com, hpa@...or.com,
linux-crypto@...r.kernel.org
Subject: Re: [PATCH 1/3] random: replace non-blocking pool with a Chacha20-based CRNG
Am Montag, 2. Mai 2016, 02:26:51 schrieb Theodore Ts'o:
Hi Theodore,
> The CRNG is faster, and we don't pretend to track entropy usage in the
> CRNG any more.
In general, I have no concerns with this approach either. And thank you that
some of my concerns are addressed.
There are few more concerns left open. I would suggest I would write them up
with a proposal on how to address them.
Some comments inlne:
>
> Signed-off-by: Theodore Ts'o <tytso@....edu>
> ---
> crypto/chacha20_generic.c | 61 ----------
> drivers/char/random.c | 282
> ++++++++++++++++++++++++++++++++++------------ include/crypto/chacha20.h |
> 1 +
> lib/Makefile | 2 +-
> lib/chacha20.c | 79 +++++++++++++
> 5 files changed, 294 insertions(+), 131 deletions(-)
> create mode 100644 lib/chacha20.c
>
> diff --git a/crypto/chacha20_generic.c b/crypto/chacha20_generic.c
> index da9c899..1cab831 100644
> --- a/crypto/chacha20_generic.c
> +++ b/crypto/chacha20_generic.c
> @@ -15,72 +15,11 @@
> #include <linux/module.h>
> #include <crypto/chacha20.h>
>
> -static inline u32 rotl32(u32 v, u8 n)
> -{
> - return (v << n) | (v >> (sizeof(v) * 8 - n));
> -}
> -
> static inline u32 le32_to_cpuvp(const void *p)
> {
> return le32_to_cpup(p);
> }
>
> -static void chacha20_block(u32 *state, void *stream)
> -{
> - u32 x[16], *out = stream;
> - int i;
> -
> - for (i = 0; i < ARRAY_SIZE(x); i++)
> - x[i] = state[i];
> -
> - for (i = 0; i < 20; i += 2) {
> - x[0] += x[4]; x[12] = rotl32(x[12] ^ x[0], 16);
> - x[1] += x[5]; x[13] = rotl32(x[13] ^ x[1], 16);
> - x[2] += x[6]; x[14] = rotl32(x[14] ^ x[2], 16);
> - x[3] += x[7]; x[15] = rotl32(x[15] ^ x[3], 16);
> -
> - x[8] += x[12]; x[4] = rotl32(x[4] ^ x[8], 12);
> - x[9] += x[13]; x[5] = rotl32(x[5] ^ x[9], 12);
> - x[10] += x[14]; x[6] = rotl32(x[6] ^ x[10], 12);
> - x[11] += x[15]; x[7] = rotl32(x[7] ^ x[11], 12);
> -
> - x[0] += x[4]; x[12] = rotl32(x[12] ^ x[0], 8);
> - x[1] += x[5]; x[13] = rotl32(x[13] ^ x[1], 8);
> - x[2] += x[6]; x[14] = rotl32(x[14] ^ x[2], 8);
> - x[3] += x[7]; x[15] = rotl32(x[15] ^ x[3], 8);
> -
> - x[8] += x[12]; x[4] = rotl32(x[4] ^ x[8], 7);
> - x[9] += x[13]; x[5] = rotl32(x[5] ^ x[9], 7);
> - x[10] += x[14]; x[6] = rotl32(x[6] ^ x[10], 7);
> - x[11] += x[15]; x[7] = rotl32(x[7] ^ x[11], 7);
> -
> - x[0] += x[5]; x[15] = rotl32(x[15] ^ x[0], 16);
> - x[1] += x[6]; x[12] = rotl32(x[12] ^ x[1], 16);
> - x[2] += x[7]; x[13] = rotl32(x[13] ^ x[2], 16);
> - x[3] += x[4]; x[14] = rotl32(x[14] ^ x[3], 16);
> -
> - x[10] += x[15]; x[5] = rotl32(x[5] ^ x[10], 12);
> - x[11] += x[12]; x[6] = rotl32(x[6] ^ x[11], 12);
> - x[8] += x[13]; x[7] = rotl32(x[7] ^ x[8], 12);
> - x[9] += x[14]; x[4] = rotl32(x[4] ^ x[9], 12);
> -
> - x[0] += x[5]; x[15] = rotl32(x[15] ^ x[0], 8);
> - x[1] += x[6]; x[12] = rotl32(x[12] ^ x[1], 8);
> - x[2] += x[7]; x[13] = rotl32(x[13] ^ x[2], 8);
> - x[3] += x[4]; x[14] = rotl32(x[14] ^ x[3], 8);
> -
> - x[10] += x[15]; x[5] = rotl32(x[5] ^ x[10], 7);
> - x[11] += x[12]; x[6] = rotl32(x[6] ^ x[11], 7);
> - x[8] += x[13]; x[7] = rotl32(x[7] ^ x[8], 7);
> - x[9] += x[14]; x[4] = rotl32(x[4] ^ x[9], 7);
> - }
> -
> - for (i = 0; i < ARRAY_SIZE(x); i++)
> - out[i] = cpu_to_le32(x[i] + state[i]);
> -
> - state[12]++;
> -}
> -
> static void chacha20_docrypt(u32 *state, u8 *dst, const u8 *src,
> unsigned int bytes)
> {
> diff --git a/drivers/char/random.c b/drivers/char/random.c
> index b583e53..95f4451 100644
> --- a/drivers/char/random.c
> +++ b/drivers/char/random.c
> @@ -260,6 +260,7 @@
> #include <linux/irq.h>
> #include <linux/syscalls.h>
> #include <linux/completion.h>
> +#include <crypto/chacha20.h>
>
> #include <asm/processor.h>
> #include <asm/uaccess.h>
> @@ -412,6 +413,15 @@ static struct fasync_struct *fasync;
> static DEFINE_SPINLOCK(random_ready_list_lock);
> static LIST_HEAD(random_ready_list);
>
> +/*
> + * crng_init = 0 --> Uninitialized
> + * 2 --> Initialized
> + * 3 --> Initialized from input_pool
> + */
> +static int crng_init = 0;
shouldn't that be an atomic_t ?
> +#define crng_ready() (likely(crng_init >= 2))
> +static void process_random_ready_list(void);
> +
> /**********************************************************************
> *
> * OS independent entropy store. Here are the functions which handle
> @@ -441,10 +451,13 @@ struct entropy_store {
> __u8 last_data[EXTRACT_SIZE];
> };
>
> +static ssize_t extract_entropy(struct entropy_store *r, void *buf,
> + size_t nbytes, int min, int rsvd);
> +
> +static int crng_reseed(struct entropy_store *r);
> static void push_to_pool(struct work_struct *work);
> static __u32 input_pool_data[INPUT_POOL_WORDS];
> static __u32 blocking_pool_data[OUTPUT_POOL_WORDS];
> -static __u32 nonblocking_pool_data[OUTPUT_POOL_WORDS];
>
> static struct entropy_store input_pool = {
> .poolinfo = &poolinfo_table[0],
> @@ -465,16 +478,6 @@ static struct entropy_store blocking_pool = {
> push_to_pool),
> };
>
> -static struct entropy_store nonblocking_pool = {
> - .poolinfo = &poolinfo_table[1],
> - .name = "nonblocking",
> - .pull = &input_pool,
> - .lock = __SPIN_LOCK_UNLOCKED(nonblocking_pool.lock),
> - .pool = nonblocking_pool_data,
> - .push_work = __WORK_INITIALIZER(nonblocking_pool.push_work,
> - push_to_pool),
> -};
> -
> static __u32 const twist_table[8] = {
> 0x00000000, 0x3b6e20c8, 0x76dc4190, 0x4db26158,
> 0xedb88320, 0xd6d6a3e8, 0x9b64c2b0, 0xa00ae278 };
> @@ -677,12 +680,6 @@ retry:
> 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,
> @@ -692,30 +689,27 @@ retry:
> if (r == &input_pool) {
> int entropy_bits = entropy_count >> ENTROPY_SHIFT;
>
> + if (crng_init < 3 && entropy_bits >= 128) {
> + (void) crng_reseed(r);
> + entropy_bits = r->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.
> + * entropy to the blocking pool until it is 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);
> + 3 * other->poolinfo->poolfracbits / 4) {
> + schedule_work(&other->push_work);
> r->entropy_total = 0;
> }
> }
> @@ -735,6 +729,158 @@ static void credit_entropy_bits_safe(struct
> entropy_store *r, int nbits)
>
> /*********************************************************************
> *
> + * CRNG using CHACHA20
> + *
> + *********************************************************************/
> +
> +#define CRNG_RESEED_INTERVAL (300*HZ)
> +
> +struct crng_state {
> + __u32 state[16];
> + unsigned long init_time;
> + spinlock_t lock;
> +};
> +
> +struct crng_state primary_crng = {
> + .lock = __SPIN_LOCK_UNLOCKED(primary_crng.lock),
> +};
> +static DECLARE_WAIT_QUEUE_HEAD(crng_init_wait);
> +
> +static void _initialize_crng(struct crng_state *crng)
> +{
> + int i;
> + unsigned long rv;
Why do you use unsigned long here? I thought the state[i] is unsigned int.
> +
> + memcpy(&crng->state[0], "expand 32-byte k", 16);
> + for (i = 4; i < 16; i++) {
> + if (!arch_get_random_seed_long(&rv) &&
> + !arch_get_random_long(&rv))
> + rv = random_get_entropy();
> + crng->state[i] ^= rv;
> + }
> + crng->init_time = jiffies - CRNG_RESEED_INTERVAL;
Would it make sense to add the ChaCha20 self test vectors from RFC7539 here to
test that the ChaCha20 works?
> +}
> +
> +static void initialize_crng(struct crng_state *crng)
> +{
> + _initialize_crng(crng);
> + spin_lock_init(&crng->lock);
> +}
> +
> +static int crng_fast_load(__u32 pool[4])
> +{
> + int i;
> + __u32 *p;
> +
> + if (!spin_trylock(&primary_crng.lock))
> + return 0;
> + if (crng_ready()) {
> + spin_unlock(&primary_crng.lock);
> + return 0;
> + }
> + p = &primary_crng.state[4];
> + if (crng_init == 1)
> + p += 4;
> + for (i=0; i < 4; i++)
> + *p ^= pool[i];
> + if (crng_init++ >= 2)
> + wake_up_interruptible(&crng_init_wait);
Don't we have a race here with the crng_init < 3 check in crng_reseed
considering multi-core systems?
> + pr_notice("random: crng_init %d\n", crng_init);
> + spin_unlock(&primary_crng.lock);
> + return 1;
> +}
> +
> +/* Returns 1 on success */
> +static int crng_reseed(struct entropy_store *r)
> +{
> + unsigned long flags;
> + int ret = 0;
> + int i, num, num_words;
> + __u32 tmp[16];
> +
> + spin_lock_irqsave(&primary_crng.lock, flags);
> + num = extract_entropy(r, tmp, 32, 16, 0);
> + if (num == 0)
> + goto out;
> + if (num < 16 || num > 32) {
> + WARN_ON(1);
> + pr_err("crng_reseed: num is %d?!?\n", num);
> + }
> + num_words = (num + 3) / 4;
> + for (i = 0; i < num_words; i++)
> + primary_crng.state[i+4] ^= tmp[i];
> + primary_crng.init_time = jiffies;
> + if (crng_init < 3) {
Shouldn't that one be if (crng_init < 3 && num >= 16) ?
> + crng_init = 3;
> + process_random_ready_list();
> + wake_up_interruptible(&crng_init_wait);
> + pr_notice("random: crng_init 3\n");
Would it make sense to be more descriptive here to allow readers of dmesg to
understand the output?
> + }
> + ret = 1;
> +out:
> + spin_unlock_irqrestore(&primary_crng.lock, flags);
memzero_explicit of tmp?
> + return ret;
> +}
> +
> +static inline void crng_wait_ready(void)
> +{
> + wait_event_interruptible(crng_init_wait, crng_ready());
> +}
> +
> +static void extract_crng(__u8 out[CHACHA20_BLOCK_SIZE])
> +{
> + unsigned long v, flags;
> + struct crng_state *crng = &primary_crng;
> +
> + if (crng_init > 2 &&
> + time_after(jiffies, crng->init_time + CRNG_RESEED_INTERVAL))
> + crng_reseed(&input_pool);
> + spin_lock_irqsave(&crng->lock, flags);
> + if (arch_get_random_long(&v))
> + crng->state[14] ^= v;
Again, unsigned int?
What is the purpose to only cover the 2nd 32 bit value of the nonce with
arch_get_random?
> + chacha20_block(&crng->state[0], out);
> + if (crng->state[12] == 0)
> + crng->state[13]++;
state[12]++? Or why do you increment the nonce?
> + spin_unlock_irqrestore(&crng->lock, flags);
> +}
> +
> +static ssize_t extract_crng_user(void __user *buf, size_t nbytes)
> +{
> + ssize_t ret = 0, i;
> + __u8 tmp[CHACHA20_BLOCK_SIZE];
> + int large_request = (nbytes > 256);
> +
> + while (nbytes) {
> + if (large_request && need_resched()) {
> + if (signal_pending(current)) {
> + if (ret == 0)
> + ret = -ERESTARTSYS;
> + break;
> + }
> + schedule();
> + }
> +
> + extract_crng(tmp);
Now I have to wear my (ugly) FIPS heat: we need that code from the current
implementation here:
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, CHACHA20_BLOCK_SIZE);
> + if (copy_to_user(buf, tmp, i)) {
> + ret = -EFAULT;
> + break;
> + }
> +
> + nbytes -= i;
> + buf += i;
> + ret += i;
> + }
> +
> + /* Wipe data just written to memory */
> + memzero_explicit(tmp, sizeof(tmp));
> +
> + return ret;
> +}
> +
> +
> +/*********************************************************************
> + *
> * Entropy input management
> *
> *********************************************************************/
> @@ -749,12 +895,12 @@ struct timer_rand_state {
> #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.
> + * Add device- or boot-specific data to the input pool to help
> + * initialize it.
> *
> - * 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.
> + * None of this adds any entropy; it is meant to avoid the problem of
> + * the entropy pool having similar initial state across largely
> + * identical devices.
> */
> void add_device_randomness(const void *buf, unsigned int size)
> {
> @@ -766,11 +912,6 @@ void add_device_randomness(const void *buf, unsigned
> int size) _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);
>
> @@ -801,7 +942,7 @@ static void add_timer_randomness(struct timer_rand_state
> *state, unsigned num) sample.jiffies = jiffies;
> sample.cycles = random_get_entropy();
> sample.num = num;
> - r = nonblocking_pool.initialized ? &input_pool : &nonblocking_pool;
> + r = &input_pool;
> mix_pool_bytes(r, &sample, sizeof(sample));
>
> /*
> @@ -921,7 +1062,13 @@ void add_interrupt_randomness(int irq, int irq_flags)
> !time_after(now, fast_pool->last + HZ))
> return;
>
> - r = nonblocking_pool.initialized ? &input_pool : &nonblocking_pool;
> + if (!crng_ready() && crng_fast_load(fast_pool->pool)) {
> + fast_pool->count = 0;
> + fast_pool->last = now;
> + return;
> + }
> +
> + r = &input_pool;
> if (!spin_trylock(&r->lock))
> return;
>
> @@ -964,9 +1111,6 @@ EXPORT_SYMBOL_GPL(add_disk_randomness);
> *
> *********************************************************************/
>
> -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
> @@ -1252,15 +1396,26 @@ static ssize_t extract_entropy_user(struct
> entropy_store *r, void __user *buf, */
> void get_random_bytes(void *buf, int nbytes)
> {
> + __u8 tmp[CHACHA20_BLOCK_SIZE];
> +
> #if DEBUG_RANDOM_BOOT > 0
> - if (unlikely(nonblocking_pool.initialized == 0))
> + if (!crng_ready())
> printk(KERN_NOTICE "random: %pF get_random_bytes called "
> - "with %d bits of entropy available\n",
> - (void *) _RET_IP_,
> - nonblocking_pool.entropy_total);
> + "with crng_init = %d\n", (void *) _RET_IP_, crng_init);
> #endif
> trace_get_random_bytes(nbytes, _RET_IP_);
> - extract_entropy(&nonblocking_pool, buf, nbytes, 0, 0);
> +
> + while (nbytes >= CHACHA20_BLOCK_SIZE) {
> + extract_crng(buf);
> + buf += CHACHA20_BLOCK_SIZE;
> + nbytes -= CHACHA20_BLOCK_SIZE;
> + }
> +
> + if (nbytes > 0) {
> + extract_crng(tmp);
> + memcpy(buf, tmp, nbytes);
> + memzero_explicit(tmp, nbytes);
> + }
> }
> EXPORT_SYMBOL(get_random_bytes);
>
> @@ -1278,7 +1433,7 @@ int add_random_ready_callback(struct
> random_ready_callback *rdy) unsigned long flags;
> int err = -EALREADY;
>
> - if (likely(nonblocking_pool.initialized))
> + if (crng_ready())
> return err;
>
> owner = rdy->owner;
> @@ -1286,7 +1441,7 @@ int add_random_ready_callback(struct
> random_ready_callback *rdy) return -ENOENT;
>
> spin_lock_irqsave(&random_ready_list_lock, flags);
> - if (nonblocking_pool.initialized)
> + if (crng_ready())
> goto out;
>
> owner = NULL;
> @@ -1350,7 +1505,7 @@ void get_random_bytes_arch(void *buf, int nbytes)
> }
>
> if (nbytes)
> - extract_entropy(&nonblocking_pool, p, nbytes, 0, 0);
> + get_random_bytes(p, nbytes);
> }
> EXPORT_SYMBOL(get_random_bytes_arch);
>
> @@ -1395,7 +1550,7 @@ static int rand_initialize(void)
> {
> init_std_data(&input_pool);
> init_std_data(&blocking_pool);
> - init_std_data(&nonblocking_pool);
> + _initialize_crng(&primary_crng);
> return 0;
> }
> early_initcall(rand_initialize);
> @@ -1459,16 +1614,10 @@ 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);
> -
> + crng_wait_ready();
Just for clarification: are you now blocking /dev/urandom until the CRNG is
filled? That would be a big win.
> 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));
> + ret = extract_crng_user(buf, nbytes);
> + trace_urandom_read(8 * nbytes, 0, ENTROPY_BITS(&input_pool));
> return ret;
> }
>
> @@ -1514,10 +1663,7 @@ static ssize_t random_write(struct file *file, const
> char __user *buffer, {
> size_t ret;
>
> - ret = write_pool(&blocking_pool, buffer, count);
> - if (ret)
> - return ret;
> - ret = write_pool(&nonblocking_pool, buffer, count);
> + ret = write_pool(&input_pool, buffer, count);
> if (ret)
> return ret;
>
> @@ -1568,7 +1714,6 @@ static long random_ioctl(struct file *f, unsigned int
> cmd, unsigned long arg) 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:
> @@ -1610,11 +1755,10 @@ SYSCALL_DEFINE3(getrandom, char __user *, buf,
> size_t, count, if (flags & GRND_RANDOM)
> return _random_read(flags & GRND_NONBLOCK, buf, count);
>
> - if (unlikely(nonblocking_pool.initialized == 0)) {
> + if (!crng_ready()) {
> if (flags & GRND_NONBLOCK)
> return -EAGAIN;
> - wait_event_interruptible(urandom_init_wait,
> - nonblocking_pool.initialized);
> + crng_wait_ready();
> if (signal_pending(current))
> return -ERESTARTSYS;
> }
> diff --git a/include/crypto/chacha20.h b/include/crypto/chacha20.h
> index 274bbae..20d20f68 100644
> --- a/include/crypto/chacha20.h
> +++ b/include/crypto/chacha20.h
> @@ -16,6 +16,7 @@ struct chacha20_ctx {
> u32 key[8];
> };
>
> +void chacha20_block(u32 *state, void *stream);
> void crypto_chacha20_init(u32 *state, struct chacha20_ctx *ctx, u8 *iv);
> int crypto_chacha20_setkey(struct crypto_tfm *tfm, const u8 *key,
> unsigned int keysize);
> diff --git a/lib/Makefile b/lib/Makefile
> index 7bd6fd4..9ba27cd 100644
> --- a/lib/Makefile
> +++ b/lib/Makefile
> @@ -22,7 +22,7 @@ KCOV_INSTRUMENT_hweight.o := n
> lib-y := ctype.o string.o vsprintf.o cmdline.o \
> rbtree.o radix-tree.o dump_stack.o timerqueue.o\
> idr.o int_sqrt.o extable.o \
> - sha1.o md5.o irq_regs.o argv_split.o \
> + sha1.o chacha20.o md5.o irq_regs.o argv_split.o \
> proportions.o flex_proportions.o ratelimit.o show_mem.o \
> is_single_threaded.o plist.o decompress.o kobject_uevent.o \
> earlycpio.o seq_buf.o nmi_backtrace.o
> diff --git a/lib/chacha20.c b/lib/chacha20.c
> new file mode 100644
> index 0000000..250ceed
> --- /dev/null
> +++ b/lib/chacha20.c
> @@ -0,0 +1,79 @@
> +/*
> + * ChaCha20 256-bit cipher algorithm, RFC7539
> + *
> + * Copyright (C) 2015 Martin Willi
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; either version 2 of the License, or
> + * (at your option) any later version.
> + */
> +
> +#include <linux/kernel.h>
> +#include <linux/export.h>
> +#include <linux/bitops.h>
> +#include <linux/cryptohash.h>
> +#include <asm/unaligned.h>
> +#include <crypto/chacha20.h>
> +
> +static inline u32 rotl32(u32 v, u8 n)
> +{
> + return (v << n) | (v >> (sizeof(v) * 8 - n));
> +}
> +
> +extern void chacha20_block(u32 *state, void *stream)
> +{
> + u32 x[16], *out = stream;
> + int i;
> +
> + for (i = 0; i < ARRAY_SIZE(x); i++)
> + x[i] = state[i];
> +
> + for (i = 0; i < 20; i += 2) {
> + x[0] += x[4]; x[12] = rotl32(x[12] ^ x[0], 16);
> + x[1] += x[5]; x[13] = rotl32(x[13] ^ x[1], 16);
> + x[2] += x[6]; x[14] = rotl32(x[14] ^ x[2], 16);
> + x[3] += x[7]; x[15] = rotl32(x[15] ^ x[3], 16);
> +
> + x[8] += x[12]; x[4] = rotl32(x[4] ^ x[8], 12);
> + x[9] += x[13]; x[5] = rotl32(x[5] ^ x[9], 12);
> + x[10] += x[14]; x[6] = rotl32(x[6] ^ x[10], 12);
> + x[11] += x[15]; x[7] = rotl32(x[7] ^ x[11], 12);
> +
> + x[0] += x[4]; x[12] = rotl32(x[12] ^ x[0], 8);
> + x[1] += x[5]; x[13] = rotl32(x[13] ^ x[1], 8);
> + x[2] += x[6]; x[14] = rotl32(x[14] ^ x[2], 8);
> + x[3] += x[7]; x[15] = rotl32(x[15] ^ x[3], 8);
> +
> + x[8] += x[12]; x[4] = rotl32(x[4] ^ x[8], 7);
> + x[9] += x[13]; x[5] = rotl32(x[5] ^ x[9], 7);
> + x[10] += x[14]; x[6] = rotl32(x[6] ^ x[10], 7);
> + x[11] += x[15]; x[7] = rotl32(x[7] ^ x[11], 7);
> +
> + x[0] += x[5]; x[15] = rotl32(x[15] ^ x[0], 16);
> + x[1] += x[6]; x[12] = rotl32(x[12] ^ x[1], 16);
> + x[2] += x[7]; x[13] = rotl32(x[13] ^ x[2], 16);
> + x[3] += x[4]; x[14] = rotl32(x[14] ^ x[3], 16);
> +
> + x[10] += x[15]; x[5] = rotl32(x[5] ^ x[10], 12);
> + x[11] += x[12]; x[6] = rotl32(x[6] ^ x[11], 12);
> + x[8] += x[13]; x[7] = rotl32(x[7] ^ x[8], 12);
> + x[9] += x[14]; x[4] = rotl32(x[4] ^ x[9], 12);
> +
> + x[0] += x[5]; x[15] = rotl32(x[15] ^ x[0], 8);
> + x[1] += x[6]; x[12] = rotl32(x[12] ^ x[1], 8);
> + x[2] += x[7]; x[13] = rotl32(x[13] ^ x[2], 8);
> + x[3] += x[4]; x[14] = rotl32(x[14] ^ x[3], 8);
> +
> + x[10] += x[15]; x[5] = rotl32(x[5] ^ x[10], 7);
> + x[11] += x[12]; x[6] = rotl32(x[6] ^ x[11], 7);
> + x[8] += x[13]; x[7] = rotl32(x[7] ^ x[8], 7);
> + x[9] += x[14]; x[4] = rotl32(x[4] ^ x[9], 7);
> + }
> +
> + for (i = 0; i < ARRAY_SIZE(x); i++)
> + out[i] = cpu_to_le32(x[i] + state[i]);
> +
> + state[12]++;
> +}
> +EXPORT_SYMBOL(chacha20_block);
Ciao
Stephan
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