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Date: Wed, 12 Nov 2014 05:24:04 +0100
From: Stephan Mueller <smueller@...onox.de>
To: Herbert Xu <herbert@...dor.apana.org.au>
Cc: Marek Vasut <marex@...x.de>,
"David S. Miller" <davem@...emloft.net>,
Jason Cooper <cryptography@...edaemon.net>,
Grant Likely <grant.likely@...retlab.ca>,
'Geert Uytterhoeven' <geert@...ux-m68k.org>,
"Joy M. Latten" <jmlatten@...ux.vnet.ibm.com>,
Jonathan Corbet <corbet@....net>,
LKML <linux-kernel@...r.kernel.org>, linux-crypto@...r.kernel.org
Subject: [PATCH v3 01/13] crypto: Documentation - crypto API high level spec
The design of the kernel crypto API as well as hints to program with
the kernel crypto API are given.
The documentation contains:
* design aspects of crypto API
* develper specific hints
* references to the API function description
* source code examples
CC: Marek Vasut <marex@...x.de>
Signed-off-by: Stephan Mueller <smueller@...onox.de>
---
Documentation/DocBook/crypto-API.tmpl | 1253 +++++++++++++++++++++++++++++++++
1 file changed, 1253 insertions(+)
create mode 100644 Documentation/DocBook/crypto-API.tmpl
diff --git a/Documentation/DocBook/crypto-API.tmpl b/Documentation/DocBook/crypto-API.tmpl
new file mode 100644
index 0000000..c763d30
--- /dev/null
+++ b/Documentation/DocBook/crypto-API.tmpl
@@ -0,0 +1,1253 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.1.2//EN"
+ "http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd" []>
+
+<book id="KernelCryptoAPI">
+ <bookinfo>
+ <title>Linux Kernel Crypto API</title>
+
+ <authorgroup>
+ <author>
+ <firstname>Stephan</firstname>
+ <surname>Mueller</surname>
+ <affiliation>
+ <address>
+ <email>smueller@...onox.de</email>
+ </address>
+ </affiliation>
+ </author>
+ <author>
+ <firstname>Marek</firstname>
+ <surname>Vasut</surname>
+ <affiliation>
+ <address>
+ <email>marek@...x.de</email>
+ </address>
+ </affiliation>
+ </author>
+ </authorgroup>
+
+ <copyright>
+ <year>2014</year>
+ <holder>Stephan Mueller</holder>
+ </copyright>
+
+
+ <legalnotice>
+ <para>
+ This documentation 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.
+ </para>
+
+ <para>
+ This program is distributed in the hope that it will be
+ useful, but WITHOUT ANY WARRANTY; without even the implied
+ warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ See the GNU General Public License for more details.
+ </para>
+
+ <para>
+ You should have received a copy of the GNU General Public
+ License along with this program; if not, write to the Free
+ Software Foundation, Inc., 59 Temple Place, Suite 330, Boston,
+ MA 02111-1307 USA
+ </para>
+
+ <para>
+ For more details see the file COPYING in the source
+ distribution of Linux.
+ </para>
+ </legalnotice>
+ </bookinfo>
+
+ <toc></toc>
+
+ <chapter id="Intro">
+ <title>Kernel Crypto API Interface Specification</title>
+
+ <sect1><title>Introduction</title>
+
+ <para>
+ The kernel crypto API offers a rich set of cryptographic ciphers as
+ well as other data transformation mechanisms and methods to invoke
+ these. This document contains a description of the API and provides
+ example code.
+ </para>
+
+ <para>
+ To understand and properly use the kernel crypto API a brief
+ explanation of its structure is given. Based on the architecture,
+ the API can be separated into different components. Following the
+ architecture specification, hints to developers of ciphers are
+ provided. Pointers to the API function call documentation are
+ given at the end.
+ </para>
+
+ <para>
+ The kernel crypto API refers to all algorithms as "transformations".
+ Therefore, a cipher handle variable usually has the name "tfm".
+ Besides cryptographic operations, the kernel crypto API also knows
+ compression transformations and handles them the same way as ciphers.
+ </para>
+
+ <para>
+ The kernel crypto API serves the following entity types:
+
+ <itemizedlist>
+ <listitem>
+ <para>consumers requesting cryptographic services</para>
+ </listitem>
+ <listitem>
+ <para>data transformation implementations (typically ciphers)
+ that can be called by consumers using the kernel crypto
+ API</para>
+ </listitem>
+ </itemizedlist>
+ </para>
+
+ <para>
+ This specification is intended for consumers of the kernel crypto
+ API as well as for developers implementing ciphers. This API
+ specification, however, does not discusses all API calls available
+ to data transformation implementations (i.e. implementations of
+ ciphers and other transformations (such as CRC or even compression
+ algorithms) that can register with the kernel crypto API).
+ </para>
+
+ <para>
+ Note: The terms "transformation" and cipher algorithm are used
+ interchangably.
+ </para>
+ </sect1>
+
+ <sect1><title>Terminology</title>
+ <para>
+ The transformation implementation is an actual code or interface
+ to hardware which implements a certain transformation with precisely
+ defined behavior.
+ </para>
+
+ <para>
+ The transformation object (TFM) is an instance of a transformation
+ implementation. There can be multiple transformation objects
+ associated with a single transformation implementation. Each of
+ those transformation objects is held by a crypto API consumer or
+ another transformation. Transformation object is allocated when a
+ crypto API consumer requests a transformation implementation.
+ The consumer is then provided with a structure, which contains
+ a transformation object (TFM).
+ </para>
+
+ <para>
+ The structure that contains transformation objects may also be
+ referred to as a "cipher handle". Such a cipher handle is always
+ subject to the following phases that are reflected in the API calls
+ applicable to such a cipher handle:
+ </para>
+
+ <orderedlist>
+ <listitem>
+ <para>Initialization of a cipher handle.</para>
+ </listitem>
+ <listitem>
+ <para>Execution of all intended cipher operations applicable
+ for the handle where the cipher handle must be furnished to
+ every API call.</para>
+ </listitem>
+ <listitem>
+ <para>Destruction of a cipher handle.</para>
+ </listitem>
+ </orderedlist>
+
+ <para>
+ When using the initialization API calls, a cipher handle is
+ created and returned to the consumer. Therefore, please refer
+ to all initialization API calls that refer to the data
+ structure type a consumer is expected to receive and subsequently
+ to use. The initialization API calls have all the same naming
+ conventions of crypto_alloc_*.
+ </para>
+
+ <para>
+ The transformation context is private data associated with
+ the transformation object.
+ </para>
+ </sect1>
+ </chapter>
+
+ <chapter id="Architecture"><title>Kernel Crypto API Architecture</title>
+ <sect1><title>Cipher algorithm types</title>
+ <para>
+ The kernel crypto API provides different API calls for the
+ following cipher types:
+
+ <itemizedlist>
+ <listitem><para>Symmetric ciphers</para></listitem>
+ <listitem><para>AEAD ciphers</para></listitem>
+ <listitem><para>Message digest, including keyed message digest</para></listitem>
+ <listitem><para>Random number generation</para></listitem>
+ <listitem><para>User space interface</para></listitem>
+ </itemizedlist>
+ </para>
+ </sect1>
+
+ <sect1><title>Ciphers And Templates</title>
+ <para>
+ The kernel crypto API provides implementations of single block
+ ciphers and message digests. In addition, the kernel crypto API
+ provides numerous "templates" that can be used in conjunction
+ with the single block ciphers and message digests. Templates
+ include all types of block chaining mode, the HMAC mechanism, etc.
+ </para>
+
+ <para>
+ Single block ciphers and message digests can either be directly
+ used by a caller or invoked together with a template to form
+ multi-block ciphers or keyed message digests.
+ </para>
+
+ <para>
+ A single block cipher may even be called with multiple templates.
+ However, templates cannot be used without a single cipher.
+ </para>
+
+ <para>
+ See /proc/crypto and search for "name". For example:
+
+ <itemizedlist>
+ <listitem><para>aes</para></listitem>
+ <listitem><para>ecb(aes)</para></listitem>
+ <listitem><para>cmac(aes)</para></listitem>
+ <listitem><para>ccm(aes)</para></listitem>
+ <listitem><para>rfc4106(gcm(aes))</para></listitem>
+ <listitem><para>sha1</para></listitem>
+ <listitem><para>hmac(sha1)</para></listitem>
+ <listitem><para>authenc(hmac(sha1),cbc(aes))</para></listitem>
+ </itemizedlist>
+ </para>
+
+ <para>
+ In these examples, "aes" and "sha1" are the ciphers and all
+ others are the templates.
+ </para>
+ </sect1>
+
+ <sect1><title>Synchronous And Asynchronous Operation</title>
+ <para>
+ The kernel crypto API provides synchronous and asynchronous
+ API operations.
+ </para>
+
+ <para>
+ When using the synchronous API operation, the caller invokes
+ a cipher operation which is performed synchronously by the
+ kernel crypto API. That means, the caller waits until the
+ cipher operation completes. Therefore, the kernel crypto API
+ calls work like regular function calls. For synchronous
+ operation, the set of API calls is small and conceptually
+ similar to any other crypto library.
+ </para>
+
+ <para>
+ Asynchronous operation is provided by the kernel crypto API
+ which implies that the invocation of a cipher operation will
+ complete almost instantly. That invocation triggers the
+ cipher operation but it does not signal its completion. Before
+ invoking a cipher operation, the caller must provide a callback
+ function the kernel crypto API can invoke to signal the
+ completion of the cipher operation. Furthermore, the caller
+ must ensure it can handle such asynchronous events by applying
+ appropriate locking around its data. The kernel crypto API
+ does not perform any special serialization operation to protect
+ the caller's data integrity.
+ </para>
+ </sect1>
+
+ <sect1><title>Crypto API Cipher References And Priority</title>
+ <para>
+ A cipher is referenced by the caller with a string. That string
+ has the following semantics:
+
+ <programlisting>
+ template(single block cipher)
+ </programlisting>
+
+ where "template" and "single block cipher" is the aforementioned
+ template and single block cipher, respectively. If applicable,
+ additional templates may enclose other templates, such as
+
+ <programlisting>
+ template1(template2(single block cipher)))
+ </programlisting>
+ </para>
+
+ <para>
+ The kernel crypto API may provide multiple implementations of a
+ template or a single block cipher. For example, AES on newer
+ Intel hardware has the following implementations: AES-NI,
+ assembler implementation, or straight C. Now, when using the
+ string "aes" with the kernel crypto API, which cipher
+ implementation is used? The answer to that question is the
+ priority number assigned to each cipher implementation by the
+ kernel crypto API. When a caller uses the string to refer to a
+ cipher during initialization of a cipher handle, the kernel
+ crypto API looks up all implementations providing an
+ implementation with that name and selects the implementation
+ with the highest priority.
+ </para>
+
+ <para>
+ Now, a caller may have the need to refer to a specific cipher
+ implementation and thus does not want to rely on the
+ priority-based selection. To accommodate this scenario, the
+ kernel crypto API allows the cipher implementation to register
+ a unique name in addition to common names. When using that
+ unique name, a caller is therefore always sure to refer to
+ the intended cipher implementation.
+ </para>
+
+ <para>
+ The list of available ciphers is given in /proc/crypto. However,
+ that list does not specify all possible permutations of
+ templates and ciphers. Each block listed in /proc/crypto may
+ contain the following information -- if one of the components
+ listed as follows are not applicable to a cipher, it is not
+ displayed:
+ </para>
+
+ <itemizedlist>
+ <listitem>
+ <para>name: the generic name of the cipher that is subject
+ to the priority-based selection -- this name can be used by
+ the cipher allocation API calls (all names listed above are
+ examples for such generic names)</para>
+ </listitem>
+ <listitem>
+ <para>driver: the unique name of the cipher -- this name can
+ be used by the cipher allocation API calls</para>
+ </listitem>
+ <listitem>
+ <para>module: the kernel module providing the cipher
+ implementation (or "kernel" for statically linked ciphers)</para>
+ </listitem>
+ <listitem>
+ <para>priority: the priority value of the cipher implementation</para>
+ </listitem>
+ <listitem>
+ <para>refcnt: the reference count of the respective cipher
+ (i.e. the number of current consumers of this cipher)</para>
+ </listitem>
+ <listitem>
+ <para>selftest: specification whether the self test for the
+ cipher passed</para>
+ </listitem>
+ <listitem>
+ <para>type:
+ <itemizedlist>
+ <listitem>
+ <para>blkcipher for synchronous block ciphers</para>
+ </listitem>
+ <listitem>
+ <para>ablkcipher for asynchronous block ciphers</para>
+ </listitem>
+ <listitem>
+ <para>cipher for single block ciphers that may be used with
+ an additional template</para>
+ </listitem>
+ <listitem>
+ <para>shash for synchronous message digest</para>
+ </listitem>
+ <listitem>
+ <para>ahash for asynchronous message digest</para>
+ </listitem>
+ <listitem>
+ <para>aead for AEAD cipher type</para>
+ </listitem>
+ <listitem>
+ <para>compression for compression type transformations</para>
+ </listitem>
+ <listitem>
+ <para>rng for random number generator</para>
+ </listitem>
+ <listitem>
+ <para>givcipher for cipher with associated IV generator
+ (see the geniv entry below for the specification of the
+ IV generator type used by the cipher implementation)</para>
+ </listitem>
+ </itemizedlist>
+ </para>
+ </listitem>
+ <listitem>
+ <para>blocksize: blocksize of cipher in bytes</para>
+ </listitem>
+ <listitem>
+ <para>keysize: key size in bytes</para>
+ </listitem>
+ <listitem>
+ <para>ivsize: IV size in bytes</para>
+ </listitem>
+ <listitem>
+ <para>seedsize: required size of seed data for random number
+ generator</para>
+ </listitem>
+ <listitem>
+ <para>digestsize: output size of the message digest</para>
+ </listitem>
+ <listitem>
+ <para>geniv: IV generation type:
+ <itemizedlist>
+ <listitem>
+ <para>eseqiv for encrypted sequence number based IV
+ generation</para>
+ </listitem>
+ <listitem>
+ <para>seqiv for sequence number based IV generation</para>
+ </listitem>
+ <listitem>
+ <para>chainiv for chain iv generation</para>
+ </listitem>
+ <listitem>
+ <para><builtin> is a marker that the cipher implements
+ IV generation and handling as it is specific to the given
+ cipher</para>
+ </listitem>
+ </itemizedlist>
+ </para>
+ </listitem>
+ </itemizedlist>
+ </sect1>
+
+ <sect1><title>Key Sizes</title>
+ <para>
+ When allocating a cipher handle, the caller only specifies the
+ cipher type. Symmetric ciphers, however, typically support
+ multiple key sizes (e.g. AES-128 vs. AES-192 vs. AES-256).
+ These key sizes are determined with the length of the provided
+ key. Thus, the kernel crypto API does not provide a separate
+ way to select the particular symmetric cipher key size.
+ </para>
+ </sect1>
+
+ <sect1><title>Cipher Allocation Type And Masks</title>
+ <para>
+ The different cipher handle allocation functions allow the
+ specification of a type and mask flag. Both parameters have
+ the following meaning (and are therefore not covered in the
+ subsequent sections).
+ </para>
+
+ <para>
+ The type flag specifies the type of the cipher algorithm.
+ The caller usually provides a 0 when the caller wants the
+ default handling. Otherwise, the caller may provide the
+ following selections which match the the aforementioned
+ cipher types:
+ </para>
+
+ <itemizedlist>
+ <listitem>
+ <para>CRYPTO_ALG_TYPE_CIPHER Single block cipher</para>
+ </listitem>
+ <listitem>
+ <para>CRYPTO_ALG_TYPE_COMPRESS Compression</para>
+ </listitem>
+ <listitem>
+ <para>CRYPTO_ALG_TYPE_AEAD Authenticated Encryption with
+ Associated Data (MAC)</para>
+ </listitem>
+ <listitem>
+ <para>CRYPTO_ALG_TYPE_BLKCIPHER Synchronous multi-block cipher</para>
+ </listitem>
+ <listitem>
+ <para>CRYPTO_ALG_TYPE_ABLKCIPHER Asynchronous multi-block cipher</para>
+ </listitem>
+ <listitem>
+ <para>CRYPTO_ALG_TYPE_GIVCIPHER Asynchronous multi-block
+ cipher packed together with an IV generator (see geniv field
+ in the /proc/crypto listing for the known IV generators)</para>
+ </listitem>
+ <listitem>
+ <para>CRYPTO_ALG_TYPE_DIGEST Raw message digest</para>
+ </listitem>
+ <listitem>
+ <para>CRYPTO_ALG_TYPE_HASH Alias for CRYPTO_ALG_TYPE_DIGEST</para>
+ </listitem>
+ <listitem>
+ <para>CRYPTO_ALG_TYPE_SHASH Synchronous multi-block hash</para>
+ </listitem>
+ <listitem>
+ <para>CRYPTO_ALG_TYPE_AHASH Asynchronous multi-block hash</para>
+ </listitem>
+ <listitem>
+ <para>CRYPTO_ALG_TYPE_RNG Random Number Generation</para>
+ </listitem>
+ <listitem>
+ <para>CRYPTO_ALG_TYPE_PCOMPRESS Enhanced version of
+ CRYPTO_ALG_TYPE_COMPRESS allowing for segmented compression /
+ decompression instead of performing the operation on one
+ segment only. CRYPTO_ALG_TYPE_PCOMPRESS is intended to replace
+ CRYPTO_ALG_TYPE_COMPRESS once existing consumers are converted.</para>
+ </listitem>
+ </itemizedlist>
+
+ <para>
+ The mask flag restricts the type of cipher. The only allowed
+ flag is CRYPTO_ALG_ASYNC to restrict the cipher lookup function
+ to asynchronous ciphers. Usually, a caller provides a 0 for the
+ mask flag.
+ </para>
+
+ <para>
+ When the caller provides a mask and type specification, the
+ caller limits the search the kernel crypto API can perform for
+ a suitable cipher implementation for the given cipher name.
+ That means, even when a caller uses a cipher name that exists
+ during its initialization call, the kernel crypto API may not
+ select it due to the used type and mask field.
+ </para>
+ </sect1>
+ </chapter>
+
+ <chapter id="Development"><title>Developing Cipher Algorithms</title>
+ <sect1><title>Registering And Unregistering Transformation</title>
+ <para>
+ There are three distinct types of registration functions in
+ the Crypto API. One is used to register a generic cryptographic
+ transformation, while the other two are specific to HASH
+ transformations and COMPRESSion. We will discuss the latter
+ two in a separate chapter, here we will only look at the
+ generic ones.
+ </para>
+
+ <para>
+ Before discussing the register functions, the data structure
+ to be filled with each, struct crypto_alg, must be considered
+ -- see below for a description of this data structure.
+ </para>
+
+ <para>
+ The generic registration functions can be found in
+ include/linux/crypto.h and their definition can be seen below.
+ The former function registers a single transformation, while
+ the latter works on an array of transformation descriptions.
+ The latter is useful when registering transformations in bulk.
+ </para>
+
+ <programlisting>
+ int crypto_register_alg(struct crypto_alg *alg);
+ int crypto_register_algs(struct crypto_alg *algs, int count);
+ </programlisting>
+
+ <para>
+ The counterparts to those functions are listed below.
+ </para>
+
+ <programlisting>
+ int crypto_unregister_alg(struct crypto_alg *alg);
+ int crypto_unregister_algs(struct crypto_alg *algs, int count);
+ </programlisting>
+
+ <para>
+ Notice that both registration and unregistration functions
+ do return a value, so make sure to handle errors. A return
+ code of zero implies success. Any return code < 0 implies
+ an error.
+ </para>
+
+ <para>
+ The bulk registration / unregistration functions require
+ that struct crypto_alg is an array of count size. These
+ functions simply loop over that array and register /
+ unregister each individual algorithm. If an error occurs,
+ the loop is terminated at the offending algorithm definition.
+ That means, the algorithms prior to the offending algorithm
+ are successfully registered. Note, the caller has no way of
+ knowing which cipher implementations have successfully
+ registered. If this is important to know, the caller should
+ loop through the different implementations using the single
+ instance *_alg functions for each individual implementation.
+ </para>
+ </sect1>
+
+ <sect1><title>Single-Block Symmetric Ciphers [CIPHER]</title>
+ <para>
+ Example of transformations: aes, arc4, ...
+ </para>
+
+ <para>
+ This section describes the simplest of all transformation
+ implementations, that being the CIPHER type used for symmetric
+ ciphers. The CIPHER type is used for transformations which
+ operate on exactly one block at a time and there are no
+ dependencies between blocks at all.
+ </para>
+
+ <sect2><title>Registration specifics</title>
+ <para>
+ The registration of [CIPHER] algorithm is specific in that
+ struct crypto_alg field .cra_type is empty. The .cra_u.cipher
+ has to be filled in with proper callbacks to implement this
+ transformation.
+ </para>
+
+ <para>
+ See struct cipher_alg below.
+ </para>
+ </sect2>
+
+ <sect2><title>Cipher Definition With struct cipher_alg</title>
+ <para>
+ Struct cipher_alg defines a single block cipher.
+ </para>
+
+ <para>
+ Here are schematics of how these functions are called when
+ operated from other part of the kernel. Note that the
+ .cia_setkey() call might happen before or after any of these
+ schematics happen, but must not happen during any of these
+ are in-flight.
+ </para>
+
+ <para>
+ <programlisting>
+ KEY ---. PLAINTEXT ---.
+ v v
+ .cia_setkey() -> .cia_encrypt()
+ |
+ '-----> CIPHERTEXT
+ </programlisting>
+ </para>
+
+ <para>
+ Please note that a pattern where .cia_setkey() is called
+ multiple times is also valid:
+ </para>
+
+ <para>
+ <programlisting>
+
+ KEY1 --. PLAINTEXT1 --. KEY2 --. PLAINTEXT2 --.
+ v v v v
+ .cia_setkey() -> .cia_encrypt() -> .cia_setkey() -> .cia_encrypt()
+ | |
+ '---> CIPHERTEXT1 '---> CIPHERTEXT2
+ </programlisting>
+ </para>
+
+ </sect2>
+ </sect1>
+
+ <sect1><title>Multi-Block Ciphers [BLKCIPHER] [ABLKCIPHER]</title>
+ <para>
+ Example of transformations: cbc(aes), ecb(arc4), ...
+ </para>
+
+ <para>
+ This section describes the multi-block cipher transformation
+ implementations for both synchronous [BLKCIPHER] and
+ asynchronous [ABLKCIPHER] case. The multi-block ciphers are
+ used for transformations which operate on scatterlists of
+ data supplied to the transformation functions. They output
+ the result into a scatterlist of data as well.
+ </para>
+
+ <sect2><title>Registration Specifics</title>
+
+ <para>
+ The registration of [BLKCIPHER] or [ABLKCIPHER] algorithms
+ is one of the most standard procedures throughout the crypto API.
+ </para>
+
+ <para>
+ Note, if a cipher implementation requires a proper alignment
+ of data, the caller should use the functions of
+ crypto_blkcipher_alignmask() or crypto_ablkcipher_alignmask()
+ respectively to identify a memory alignment mask. The kernel
+ crypto API is able to process requests that are unaligned.
+ This implies, however, additional overhead as the kernel
+ crypto API needs to perform the realignment of the data which
+ may imply moving of data.
+ </para>
+ </sect2>
+
+ <sect2><title>Cipher Definition With struct blkcipher_alg and ablkcipher_alg</title>
+ <para>
+ Struct blkcipher_alg defines a synchronous block cipher whereas
+ struct ablkcipher_alg defines an asynchronous block cipher.
+ </para>
+
+ <para>
+ Please refer to the single block cipher description for schematics
+ of the block cipher usage. The usage patterns are exactly the same
+ for [ABLKCIPHER] and [BLKCIPHER] as they are for plain [CIPHER].
+ </para>
+ </sect2>
+
+ <sect2><title>Specifics Of Asynchronous Multi-Block Cipher</title>
+ <para>
+ There are a couple of specifics to the [ABLKCIPHER] interface.
+ </para>
+
+ <para>
+ First of all, some of the drivers will want to use the
+ Generic ScatterWalk in case the hardware needs to be fed
+ separate chunks of the scatterlist which contains the
+ plaintext and will contain the ciphertext. Please refer
+ to the ScatterWalk interface offered by the Linux kernel
+ scatter / gather list implementation.
+ </para>
+ </sect2>
+ </sect1>
+
+ <sect1><title>Hashing [HASH]</title>
+
+ <para>
+ Example of transformations: crc32, md5, sha1, sha256,...
+ </para>
+
+ <sect2><title>Registering And Unregistering The Transformation</title>
+
+ <para>
+ There are multiple ways to register a HASH transformation,
+ depending on whether the transformation is synchronous [SHASH]
+ or asynchronous [AHASH] and the amount of HASH transformations
+ we are registering. You can find the prototypes defined in
+ include/crypto/internal/hash.h:
+ </para>
+
+ <programlisting>
+ int crypto_register_ahash(struct ahash_alg *alg);
+
+ int crypto_register_shash(struct shash_alg *alg);
+ int crypto_register_shashes(struct shash_alg *algs, int count);
+ </programlisting>
+
+ <para>
+ The respective counterparts for unregistering the HASH
+ transformation are as follows:
+ </para>
+
+ <programlisting>
+ int crypto_unregister_ahash(struct ahash_alg *alg);
+
+ int crypto_unregister_shash(struct shash_alg *alg);
+ int crypto_unregister_shashes(struct shash_alg *algs, int count);
+ </programlisting>
+ </sect2>
+
+ <sect2><title>Cipher Definition With struct shash_alg and ahash_alg</title>
+ <para>
+ Here are schematics of how these functions are called when
+ operated from other part of the kernel. Note that the .setkey()
+ call might happen before or after any of these schematics happen,
+ but must not happen during any of these are in-flight. Please note
+ that calling .init() followed immediately by .finish() is also a
+ perfectly valid transformation.
+ </para>
+
+ <programlisting>
+ I) DATA -----------.
+ v
+ .init() -> .update() -> .final() ! .update() might not be called
+ ^ | | at all in this scenario.
+ '----' '---> HASH
+
+ II) DATA -----------.-----------.
+ v v
+ .init() -> .update() -> .finup() ! .update() may not be called
+ ^ | | at all in this scenario.
+ '----' '---> HASH
+
+ III) DATA -----------.
+ v
+ .digest() ! The entire process is handled
+ | by the .digest() call.
+ '---------------> HASH
+ </programlisting>
+
+ <para>
+ Here is a schematic of how the .export()/.import() functions are
+ called when used from another part of the kernel.
+ </para>
+
+ <programlisting>
+ KEY--. DATA--.
+ v v ! .update() may not be called
+ .setkey() -> .init() -> .update() -> .export() at all in this scenario.
+ ^ | |
+ '-----' '--> PARTIAL_HASH
+
+ ----------- other transformations happen here -----------
+
+ PARTIAL_HASH--. DATA1--.
+ v v
+ .import -> .update() -> .final() ! .update() may not be called
+ ^ | | at all in this scenario.
+ '----' '--> HASH1
+
+ PARTIAL_HASH--. DATA2-.
+ v v
+ .import -> .finup()
+ |
+ '---------------> HASH2
+ </programlisting>
+ </sect2>
+
+ <sect2><title>Specifics Of Asynchronous HASH Transformation</title>
+ <para>
+ Some of the drivers will want to use the Generic ScatterWalk
+ in case the implementation needs to be fed separate chunks of the
+ scatterlist which contains the input data. The buffer containing
+ the resulting hash will always be properly aligned to
+ .cra_alignmask so there is no need to worry about this.
+ </para>
+ </sect2>
+ </sect1>
+ </chapter>
+
+ <chapter id="API"><title>Programming Interface</title>
+ <sect1><title>Block Cipher Context Data Structures</title>
+!Pinclude/linux/crypto.h Block Cipher Context Data Structures
+!Finclude/linux/crypto.h aead_request
+ </sect1>
+ <sect1><title>Block Cipher Algorithm Definitions</title>
+!Pinclude/linux/crypto.h Block Cipher Algorithm Definitions
+!Finclude/linux/crypto.h crypto_alg
+!Finclude/linux/crypto.h ablkcipher_alg
+!Finclude/linux/crypto.h aead_alg
+!Finclude/linux/crypto.h blkcipher_alg
+!Finclude/linux/crypto.h cipher_alg
+!Finclude/linux/crypto.h rng_alg
+ </sect1>
+ <sect1><title>Asynchronous Block Cipher API</title>
+!Pinclude/linux/crypto.h Asynchronous Block Cipher API
+!Finclude/linux/crypto.h crypto_alloc_ablkcipher
+!Finclude/linux/crypto.h crypto_free_ablkcipher
+!Finclude/linux/crypto.h crypto_has_ablkcipher
+!Finclude/linux/crypto.h crypto_ablkcipher_ivsize
+!Finclude/linux/crypto.h crypto_ablkcipher_blocksize
+!Finclude/linux/crypto.h crypto_ablkcipher_setkey
+!Finclude/linux/crypto.h crypto_ablkcipher_reqtfm
+!Finclude/linux/crypto.h crypto_ablkcipher_encrypt
+!Finclude/linux/crypto.h crypto_ablkcipher_decrypt
+ </sect1>
+ <sect1><title>Asynchronous Cipher Request Handle</title>
+!Pinclude/linux/crypto.h Asynchronous Cipher Request Handle
+!Finclude/linux/crypto.h crypto_ablkcipher_reqsize
+!Finclude/linux/crypto.h ablkcipher_request_set_tfm
+!Finclude/linux/crypto.h ablkcipher_request_alloc
+!Finclude/linux/crypto.h ablkcipher_request_free
+!Finclude/linux/crypto.h ablkcipher_request_set_callback
+!Finclude/linux/crypto.h ablkcipher_request_set_crypt
+ </sect1>
+ <sect1><title>Authenticated Encryption With Associated Data (AEAD) Cipher API</title>
+!Pinclude/linux/crypto.h Authenticated Encryption With Associated Data (AEAD) Cipher API
+!Finclude/linux/crypto.h crypto_alloc_aead
+!Finclude/linux/crypto.h crypto_free_aead
+!Finclude/linux/crypto.h crypto_aead_ivsize
+!Finclude/linux/crypto.h crypto_aead_authsize
+!Finclude/linux/crypto.h crypto_aead_blocksize
+!Finclude/linux/crypto.h crypto_aead_setkey
+!Finclude/linux/crypto.h crypto_aead_setauthsize
+!Finclude/linux/crypto.h crypto_aead_encrypt
+!Finclude/linux/crypto.h crypto_aead_decrypt
+ </sect1>
+ <sect1><title>Asynchronous AEAD Request Handle</title>
+!Pinclude/linux/crypto.h Asynchronous AEAD Request Handle
+!Finclude/linux/crypto.h crypto_aead_reqsize
+!Finclude/linux/crypto.h aead_request_set_tfm
+!Finclude/linux/crypto.h aead_request_alloc
+!Finclude/linux/crypto.h aead_request_free
+!Finclude/linux/crypto.h aead_request_set_callback
+!Finclude/linux/crypto.h aead_request_set_crypt
+!Finclude/linux/crypto.h aead_request_set_assoc
+ </sect1>
+ <sect1><title>Synchronous Block Cipher API</title>
+!Pinclude/linux/crypto.h Synchronous Block Cipher API
+!Finclude/linux/crypto.h crypto_alloc_blkcipher
+!Finclude/linux/crypto.h crypto_free_blkcipher
+!Finclude/linux/crypto.h crypto_has_blkcipher
+!Finclude/linux/crypto.h crypto_blkcipher_name
+!Finclude/linux/crypto.h crypto_blkcipher_ivsize
+!Finclude/linux/crypto.h crypto_blkcipher_blocksize
+!Finclude/linux/crypto.h crypto_blkcipher_setkey
+!Finclude/linux/crypto.h crypto_blkcipher_encrypt
+!Finclude/linux/crypto.h crypto_blkcipher_encrypt_iv
+!Finclude/linux/crypto.h crypto_blkcipher_decrypt
+!Finclude/linux/crypto.h crypto_blkcipher_decrypt_iv
+!Finclude/linux/crypto.h crypto_blkcipher_set_iv
+!Finclude/linux/crypto.h crypto_blkcipher_get_iv
+ </sect1>
+ <sect1><title>Single Block Cipher API</title>
+!Pinclude/linux/crypto.h Single Block Cipher API
+!Finclude/linux/crypto.h crypto_alloc_cipher
+!Finclude/linux/crypto.h crypto_free_cipher
+!Finclude/linux/crypto.h crypto_has_cipher
+!Finclude/linux/crypto.h crypto_cipher_blocksize
+!Finclude/linux/crypto.h crypto_cipher_setkey
+!Finclude/linux/crypto.h crypto_cipher_encrypt_one
+!Finclude/linux/crypto.h crypto_cipher_decrypt_one
+ </sect1>
+ <sect1><title>Synchronous Message Digest API</title>
+!Pinclude/linux/crypto.h Synchronous Message Digest API
+!Finclude/linux/crypto.h crypto_alloc_hash
+!Finclude/linux/crypto.h crypto_free_hash
+!Finclude/linux/crypto.h crypto_has_hash
+!Finclude/linux/crypto.h crypto_hash_blocksize
+!Finclude/linux/crypto.h crypto_hash_digestsize
+!Finclude/linux/crypto.h crypto_hash_init
+!Finclude/linux/crypto.h crypto_hash_update
+!Finclude/linux/crypto.h crypto_hash_final
+!Finclude/linux/crypto.h crypto_hash_digest
+!Finclude/linux/crypto.h crypto_hash_setkey
+ </sect1>
+ <sect1><title>Message Digest Algorithm Definitions</title>
+!Pinclude/crypto/hash.h Message Digest Algorithm Definitions
+!Finclude/crypto/hash.h hash_alg_common
+!Finclude/crypto/hash.h ahash_alg
+!Finclude/crypto/hash.h shash_alg
+ </sect1>
+ <sect1><title>Asynchronous Message Digest API</title>
+!Pinclude/crypto/hash.h Asynchronous Message Digest API
+!Finclude/crypto/hash.h crypto_alloc_ahash
+!Finclude/crypto/hash.h crypto_free_ahash
+!Finclude/crypto/hash.h crypto_ahash_init
+!Finclude/crypto/hash.h crypto_ahash_digestsize
+!Finclude/crypto/hash.h crypto_ahash_reqtfm
+!Finclude/crypto/hash.h crypto_ahash_reqsize
+!Finclude/crypto/hash.h crypto_ahash_setkey
+!Finclude/crypto/hash.h crypto_ahash_finup
+!Finclude/crypto/hash.h crypto_ahash_final
+!Finclude/crypto/hash.h crypto_ahash_digest
+!Finclude/crypto/hash.h crypto_ahash_export
+!Finclude/crypto/hash.h crypto_ahash_import
+ </sect1>
+ <sect1><title>Asynchronous Hash Request Handle</title>
+!Pinclude/crypto/hash.h Asynchronous Hash Request Handle
+!Finclude/crypto/hash.h ahash_request_set_tfm
+!Finclude/crypto/hash.h ahash_request_alloc
+!Finclude/crypto/hash.h ahash_request_free
+!Finclude/crypto/hash.h ahash_request_set_callback
+!Finclude/crypto/hash.h ahash_request_set_crypt
+ </sect1>
+ <sect1><title>Synchronous Message Digest API</title>
+!Pinclude/crypto/hash.h Synchronous Message Digest API
+!Finclude/crypto/hash.h crypto_alloc_shash
+!Finclude/crypto/hash.h crypto_free_shash
+!Finclude/crypto/hash.h crypto_shash_blocksize
+!Finclude/crypto/hash.h crypto_shash_digestsize
+!Finclude/crypto/hash.h crypto_shash_descsize
+!Finclude/crypto/hash.h crypto_shash_setkey
+!Finclude/crypto/hash.h crypto_shash_digest
+!Finclude/crypto/hash.h crypto_shash_export
+!Finclude/crypto/hash.h crypto_shash_import
+!Finclude/crypto/hash.h crypto_shash_init
+!Finclude/crypto/hash.h crypto_shash_update
+!Finclude/crypto/hash.h crypto_shash_final
+!Finclude/crypto/hash.h crypto_shash_finup
+ </sect1>
+ <sect1><title>Crypto API Random Number API</title>
+!Pinclude/crypto/rng.h Random number generator API
+!Finclude/crypto/rng.h crypto_alloc_rng
+!Finclude/crypto/rng.h crypto_rng_alg
+!Finclude/crypto/rng.h crypto_free_rng
+!Finclude/crypto/rng.h crypto_rng_get_bytes
+!Finclude/crypto/rng.h crypto_rng_reset
+!Finclude/crypto/rng.h crypto_rng_seedsize
+!Cinclude/crypto/rng.h
+ </sect1>
+ </chapter>
+
+ <chapter id="Code"><title>Code Examples</title>
+ <sect1><title>Code Example For Asynchronous Block Cipher Operation</title>
+ <programlisting>
+
+struct tcrypt_result {
+ struct completion completion;
+ int err;
+};
+
+/* tie all data structures together */
+struct ablkcipher_def {
+ struct scatterlist sg;
+ struct crypto_ablkcipher *tfm;
+ struct ablkcipher_request *req;
+ struct tcrypt_result result;
+};
+
+/* Callback function */
+static void test_ablkcipher_cb(struct crypto_async_request *req, int error)
+{
+ struct tcrypt_result *result = req->data;
+
+ if (error == -EINPROGRESS)
+ return;
+ result->err = error;
+ complete(&result->completion);
+ pr_info("Encryption finished successfully\n");
+}
+
+/* Perform cipher operation */
+static unsigned int test_ablkcipher_encdec(struct ablkcipher_def *ablk,
+ int enc)
+{
+ int rc = 0;
+
+ if (enc)
+ rc = crypto_ablkcipher_encrypt(ablk->req);
+ else
+ rc = crypto_ablkcipher_decrypt(ablk->req);
+
+ switch (rc) {
+ case 0:
+ break;
+ case -EINPROGRESS:
+ case -EBUSY:
+ rc = wait_for_completion_interruptible(
+ &ablk->result.completion);
+ if (!rc && !ablk->result.err) {
+ reinit_completion(&ablk->result.completion);
+ break;
+ }
+ default:
+ pr_info("ablkcipher encrypt returned with %d result %d\n",
+ rc, ablk->result.err);
+ break;
+ }
+ init_completion(&ablk->result.completion);
+
+ return rc;
+}
+
+/* Initialize and trigger cipher operation */
+static int test_ablkcipher(void)
+{
+ struct ablkcipher_def ablk;
+ struct crypto_ablkcipher *ablkcipher = NULL;
+ struct ablkcipher_request *req = NULL;
+ char *scratchpad = NULL;
+ char *ivdata = NULL;
+ unsigned char key[32];
+ int ret = -EFAULT;
+
+ ablkcipher = crypto_alloc_ablkcipher("cbc-aes-aesni", 0, 0);
+ if (IS_ERR(ablkcipher)) {
+ pr_info("could not allocate ablkcipher handle\n");
+ return PTR_ERR(ablkcipher);
+ }
+
+ req = ablkcipher_request_alloc(ablkcipher, GFP_KERNEL);
+ if (IS_ERR(req)) {
+ pr_info("could not allocate request queue\n");
+ ret = PTR_ERR(req);
+ goto out;
+ }
+
+ ablkcipher_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG,
+ test_ablkcipher_cb,
+ &ablk.result);
+
+ /* AES 256 with random key */
+ get_random_bytes(&key, 32);
+ if (crypto_ablkcipher_setkey(ablkcipher, key, 32)) {
+ pr_info("key could not be set\n");
+ ret = -EAGAIN;
+ goto out;
+ }
+
+ /* IV will be random */
+ ivdata = kmalloc(16, GFP_KERNEL);
+ if (!ivdata) {
+ pr_info("could not allocate ivdata\n");
+ goto out;
+ }
+ get_random_bytes(ivdata, 16);
+
+ /* Input data will be random */
+ scratchpad = kmalloc(16, GFP_KERNEL);
+ if (!scratchpad) {
+ pr_info("could not allocate scratchpad\n");
+ goto out;
+ }
+ get_random_bytes(scratchpad, 16);
+
+ ablk.tfm = ablkcipher;
+ ablk.req = req;
+
+ /* We encrypt one block */
+ sg_init_one(&ablk.sg, scratchpad, 16);
+ ablkcipher_request_set_crypt(req, &ablk.sg, &ablk.sg, 16, ivdata);
+ init_completion(&ablk.result.completion);
+
+ /* encrypt data */
+ ret = test_ablkcipher_encdec(&ablk, 1);
+ if (ret)
+ goto out;
+
+ pr_info("Encryption triggered successfully\n");
+
+out:
+ if (ablkcipher)
+ crypto_free_ablkcipher(ablkcipher);
+ if (req)
+ ablkcipher_request_free(req);
+ if (ivdata)
+ kfree(ivdata);
+ if (scratchpad)
+ kfree(scratchpad);
+ return ret;
+}
+ </programlisting>
+ </sect1>
+
+ <sect1><title>Code Example For Synchronous Block Cipher Operation</title>
+ <programlisting>
+
+static int test_blkcipher(void)
+{
+ struct crypto_blkcipher *blkcipher = NULL;
+ char *cipher = "cbc(aes)";
+ // AES 128
+ charkey =
+"\x12\x34\x56\x78\x90\xab\xcd\xef\x12\x34\x56\x78\x90\xab\xcd\xef";
+ chariv =
+"\x12\x34\x56\x78\x90\xab\xcd\xef\x12\x34\x56\x78\x90\xab\xcd\xef";
+ unsigned int ivsize = 0;
+ char *scratchpad = NULL; // holds plaintext and ciphertext
+ struct scatterlist sg;
+ struct blkcipher_desc desc;
+ int ret = -EFAULT;
+
+ blkcipher = crypto_alloc_blkcipher(cipher, 0, 0);
+ if (IS_ERR(blkcipher)) {
+ printk("could not allocate blkcipher handle for %s\n", cipher);
+ return -PTR_ERR(blkcipher);
+ }
+
+ if (crypto_blkcipher_setkey(blkcipher, key, strlen(key))) {
+ printk("key could not be set\n");
+ ret = -EAGAIN;
+ goto out;
+ }
+
+ ivsize = crypto_blkcipher_ivsize(blkcipher);
+ if (ivsize) {
+ if (ivsize != strlen(iv))
+ printk("IV length differs from expected length\n");
+ crypto_blkcipher_set_iv(blkcipher, iv, ivsize);
+ }
+
+ scratchpad = kmalloc(crypto_blkcipher_blocksize(blkcipher), GFP_KERNEL);
+ if (!scratchpad) {
+ printk("could not allocate scratchpad for %s\n", cipher);
+ goto out;
+ }
+ /* get some random data that we want to encrypt */
+ get_random_bytes(scratchpad, crypto_blkcipher_blocksize(blkcipher));
+
+ desc.flags = 0;
+ desc.tfm = blkcipher;
+ sg_init_one(&sg, scratchpad, crypto_blkcipher_blocksize(blkcipher));
+
+ /* encrypt data in place */
+ crypto_blkcipher_encrypt(&desc, &sg, &sg,
+ crypto_blkcipher_blocksize(blkcipher));
+
+ /* decrypt data in place
+ * crypto_blkcipher_decrypt(&desc, &sg, &sg,
+ */ crypto_blkcipher_blocksize(blkcipher));
+
+
+ printk("Cipher operation completed\n");
+ return 0;
+
+out:
+ if (blkcipher)
+ crypto_free_blkcipher(blkcipher);
+ if (scratchpad)
+ kzfree(scratchpad);
+ return ret;
+}
+ </programlisting>
+ </sect1>
+
+ <sect1><title>Code Example For Use of Operational State Memory With SHASH</title>
+ <programlisting>
+
+struct sdesc {
+ struct shash_desc shash;
+ char ctx[];
+};
+
+static struct sdescinit_sdesc(struct crypto_shash *alg)
+{
+ struct sdescsdesc;
+ int size;
+
+ size = sizeof(struct shash_desc) + crypto_shash_descsize(alg);
+ sdesc = kmalloc(size, GFP_KERNEL);
+ if (!sdesc)
+ return ERR_PTR(-ENOMEM);
+ sdesc->shash.tfm = alg;
+ sdesc->shash.flags = 0x0;
+ return sdesc;
+}
+
+static int calc_hash(struct crypto_shashalg,
+ const unsigned chardata, unsigned int datalen,
+ unsigned chardigest) {
+ struct sdescsdesc;
+ int ret;
+
+ sdesc = init_sdesc(alg);
+ if (IS_ERR(sdesc)) {
+ pr_info("trusted_key: can't alloc %s\n", hash_alg);
+ return PTR_ERR(sdesc);
+ }
+
+ ret = crypto_shash_digest(&sdesc->shash, data, datalen, digest);
+ kfree(sdesc);
+ return ret;
+}
+ </programlisting>
+ </sect1>
+
+ <sect1><title>Code Example For Random Number Generator Usage</title>
+ <programlisting>
+
+static int get_random_numbers(u8 *buf, unsigned int len)
+{
+ struct crypto_rngrng = NULL;
+ chardrbg = "drbg_nopr_sha256"; /* Hash DRBG with SHA-256, no PR */
+ int ret;
+
+ if (!buf || !len) {
+ pr_debug("No output buffer provided\n");
+ return -EINVAL;
+ }
+
+ rng = crypto_alloc_rng(drbg, 0, 0);
+ if (IS_ERR(rng)) {
+ pr_debug("could not allocate RNG handle for %s\n", drbg);
+ return -PTR_ERR(rng);
+ }
+
+ ret = crypto_rng_get_bytes(rng, buf, len);
+ if (ret < 0)
+ pr_debug("generation of random numbers failed\n");
+ else if (ret == 0)
+ pr_debug("RNG returned no data");
+ else
+ pr_debug("RNG returned %d bytes of data\n", ret);
+
+out:
+ crypto_free_rng(rng);
+ return ret;
+}
+ </programlisting>
+ </sect1>
+ </chapter>
+ </book>
--
2.1.0
--
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