From c441a4781ff1c5b78db1410f708aa96dceec5fa2 Mon Sep 17 00:00:00 2001 From: Stephan Mueller Date: Fri, 21 Oct 2016 04:57:00 +0200 Subject: [PATCH] crypto: doc - remove crypto API DocBook With the conversion of the documentation to Sphinx, the old DocBook is now stale. Signed-off-by: Stephan Mueller Signed-off-by: Jonathan Corbet --- Documentation/DocBook/Makefile | 2 +- Documentation/DocBook/crypto-API.tmpl | 2092 --------------------------------- 2 files changed, 1 insertion(+), 2093 deletions(-) delete mode 100644 Documentation/DocBook/crypto-API.tmpl diff --git a/Documentation/DocBook/Makefile b/Documentation/DocBook/Makefile index caab903..c75e5d6 100644 --- a/Documentation/DocBook/Makefile +++ b/Documentation/DocBook/Makefile @@ -13,7 +13,7 @@ DOCBOOKS := z8530book.xml \ gadget.xml libata.xml mtdnand.xml librs.xml rapidio.xml \ genericirq.xml s390-drivers.xml uio-howto.xml scsi.xml \ 80211.xml sh.xml regulator.xml w1.xml \ - writing_musb_glue_layer.xml crypto-API.xml iio.xml + writing_musb_glue_layer.xml iio.xml ifeq ($(DOCBOOKS),) diff --git a/Documentation/DocBook/crypto-API.tmpl b/Documentation/DocBook/crypto-API.tmpl deleted file mode 100644 index 088b79c..0000000 --- a/Documentation/DocBook/crypto-API.tmpl +++ /dev/null @@ -1,2092 +0,0 @@ - - - - - - Linux Kernel Crypto API - - - - Stephan - Mueller - -
- smueller@chronox.de -
- - - - Marek - Vasut - -
- marek@denx.de -
- - - - - - 2014 - Stephan Mueller - - - - - - 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. - - - - 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. - - - - 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 - - - - For more details see the file COPYING in the source - distribution of Linux. - - - - - - - - Kernel Crypto API Interface Specification - - Introduction - - - 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. - - - - 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. - - - - 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. - - - - The kernel crypto API serves the following entity types: - - - - consumers requesting cryptographic services - - - data transformation implementations (typically ciphers) - that can be called by consumers using the kernel crypto - API - - - - - - This specification is intended for consumers of the kernel crypto - API as well as for developers implementing ciphers. This API - specification, however, does not discuss 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). - - - - Note: The terms "transformation" and cipher algorithm are used - interchangeably. - - - - Terminology - - The transformation implementation is an actual code or interface - to hardware which implements a certain transformation with precisely - defined behavior. - - - - 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). - - - - 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: - - - - - Initialization of a cipher handle. - - - Execution of all intended cipher operations applicable - for the handle where the cipher handle must be furnished to - every API call. - - - Destruction of a cipher handle. - - - - - 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_*. - - - - The transformation context is private data associated with - the transformation object. - - - - - Kernel Crypto API Architecture - Cipher algorithm types - - The kernel crypto API provides different API calls for the - following cipher types: - - - Symmetric ciphers - AEAD ciphers - Message digest, including keyed message digest - Random number generation - User space interface - - - - - Ciphers And Templates - - 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. - - - - 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. - - - - A single block cipher may even be called with multiple templates. - However, templates cannot be used without a single cipher. - - - - See /proc/crypto and search for "name". For example: - - - aes - ecb(aes) - cmac(aes) - ccm(aes) - rfc4106(gcm(aes)) - sha1 - hmac(sha1) - authenc(hmac(sha1),cbc(aes)) - - - - - In these examples, "aes" and "sha1" are the ciphers and all - others are the templates. - - - - Synchronous And Asynchronous Operation - - The kernel crypto API provides synchronous and asynchronous - API operations. - - - - 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. - - - - 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. - - - - Crypto API Cipher References And Priority - - A cipher is referenced by the caller with a string. That string - has the following semantics: - - - template(single block cipher) - - - 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 - - - template1(template2(single block cipher))) - - - - - 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. - - - - 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. - - - - 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: - - - - - 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) - - - driver: the unique name of the cipher -- this name can - be used by the cipher allocation API calls - - - module: the kernel module providing the cipher - implementation (or "kernel" for statically linked ciphers) - - - priority: the priority value of the cipher implementation - - - refcnt: the reference count of the respective cipher - (i.e. the number of current consumers of this cipher) - - - selftest: specification whether the self test for the - cipher passed - - - type: - - - skcipher for symmetric key ciphers - - - cipher for single block ciphers that may be used with - an additional template - - - shash for synchronous message digest - - - ahash for asynchronous message digest - - - aead for AEAD cipher type - - - compression for compression type transformations - - - rng for random number generator - - - 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) - - - - - - blocksize: blocksize of cipher in bytes - - - keysize: key size in bytes - - - ivsize: IV size in bytes - - - seedsize: required size of seed data for random number - generator - - - digestsize: output size of the message digest - - - geniv: IV generation type: - - - eseqiv for encrypted sequence number based IV - generation - - - seqiv for sequence number based IV generation - - - chainiv for chain iv generation - - - <builtin> is a marker that the cipher implements - IV generation and handling as it is specific to the given - cipher - - - - - - - - Key Sizes - - 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. - - - - Cipher Allocation Type And Masks - - 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). - - - - 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 aforementioned cipher - types: - - - - - CRYPTO_ALG_TYPE_CIPHER Single block cipher - - - CRYPTO_ALG_TYPE_COMPRESS Compression - - - CRYPTO_ALG_TYPE_AEAD Authenticated Encryption with - Associated Data (MAC) - - - CRYPTO_ALG_TYPE_BLKCIPHER Synchronous multi-block cipher - - - CRYPTO_ALG_TYPE_ABLKCIPHER Asynchronous multi-block cipher - - - 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) - - - CRYPTO_ALG_TYPE_DIGEST Raw message digest - - - CRYPTO_ALG_TYPE_HASH Alias for CRYPTO_ALG_TYPE_DIGEST - - - CRYPTO_ALG_TYPE_SHASH Synchronous multi-block hash - - - CRYPTO_ALG_TYPE_AHASH Asynchronous multi-block hash - - - CRYPTO_ALG_TYPE_RNG Random Number Generation - - - CRYPTO_ALG_TYPE_AKCIPHER Asymmetric cipher - - - 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. - - - - - 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. - - - - 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. - - - - Internal Structure of Kernel Crypto API - - - The kernel crypto API has an internal structure where a cipher - implementation may use many layers and indirections. This section - shall help to clarify how the kernel crypto API uses - various components to implement the complete cipher. - - - - The following subsections explain the internal structure based - on existing cipher implementations. The first section addresses - the most complex scenario where all other scenarios form a logical - subset. - - - Generic AEAD Cipher Structure - - - The following ASCII art decomposes the kernel crypto API layers - when using the AEAD cipher with the automated IV generation. The - shown example is used by the IPSEC layer. - - - - For other use cases of AEAD ciphers, the ASCII art applies as - well, but the caller may not use the AEAD cipher with a separate - IV generator. In this case, the caller must generate the IV. - - - - The depicted example decomposes the AEAD cipher of GCM(AES) based - on the generic C implementations (gcm.c, aes-generic.c, ctr.c, - ghash-generic.c, seqiv.c). The generic implementation serves as an - example showing the complete logic of the kernel crypto API. - - - - It is possible that some streamlined cipher implementations (like - AES-NI) provide implementations merging aspects which in the view - of the kernel crypto API cannot be decomposed into layers any more. - In case of the AES-NI implementation, the CTR mode, the GHASH - implementation and the AES cipher are all merged into one cipher - implementation registered with the kernel crypto API. In this case, - the concept described by the following ASCII art applies too. However, - the decomposition of GCM into the individual sub-components - by the kernel crypto API is not done any more. - - - - Each block in the following ASCII art is an independent cipher - instance obtained from the kernel crypto API. Each block - is accessed by the caller or by other blocks using the API functions - defined by the kernel crypto API for the cipher implementation type. - - - - The blocks below indicate the cipher type as well as the specific - logic implemented in the cipher. - - - - The ASCII art picture also indicates the call structure, i.e. who - calls which component. The arrows point to the invoked block - where the caller uses the API applicable to the cipher type - specified for the block. - - - - - - - - The following call sequence is applicable when the IPSEC layer - triggers an encryption operation with the esp_output function. During - configuration, the administrator set up the use of rfc4106(gcm(aes)) as - the cipher for ESP. The following call sequence is now depicted in the - ASCII art above: - - - - - - esp_output() invokes crypto_aead_encrypt() to trigger an encryption - operation of the AEAD cipher with IV generator. - - - - In case of GCM, the SEQIV implementation is registered as GIVCIPHER - in crypto_rfc4106_alloc(). - - - - The SEQIV performs its operation to generate an IV where the core - function is seqiv_geniv(). - - - - - - Now, SEQIV uses the AEAD API function calls to invoke the associated - AEAD cipher. In our case, during the instantiation of SEQIV, the - cipher handle for GCM is provided to SEQIV. This means that SEQIV - invokes AEAD cipher operations with the GCM cipher handle. - - - - During instantiation of the GCM handle, the CTR(AES) and GHASH - ciphers are instantiated. The cipher handles for CTR(AES) and GHASH - are retained for later use. - - - - The GCM implementation is responsible to invoke the CTR mode AES and - the GHASH cipher in the right manner to implement the GCM - specification. - - - - - - The GCM AEAD cipher type implementation now invokes the SKCIPHER API - with the instantiated CTR(AES) cipher handle. - - - - During instantiation of the CTR(AES) cipher, the CIPHER type - implementation of AES is instantiated. The cipher handle for AES is - retained. - - - - That means that the SKCIPHER implementation of CTR(AES) only - implements the CTR block chaining mode. After performing the block - chaining operation, the CIPHER implementation of AES is invoked. - - - - - - The SKCIPHER of CTR(AES) now invokes the CIPHER API with the AES - cipher handle to encrypt one block. - - - - - - The GCM AEAD implementation also invokes the GHASH cipher - implementation via the AHASH API. - - - - - - When the IPSEC layer triggers the esp_input() function, the same call - sequence is followed with the only difference that the operation starts - with step (2). - - - - Generic Block Cipher Structure - - Generic block ciphers follow the same concept as depicted with the ASCII - art picture above. - - - - For example, CBC(AES) is implemented with cbc.c, and aes-generic.c. The - ASCII art picture above applies as well with the difference that only - step (4) is used and the SKCIPHER block chaining mode is CBC. - - - - Generic Keyed Message Digest Structure - - Keyed message digest implementations again follow the same concept as - depicted in the ASCII art picture above. - - - - For example, HMAC(SHA256) is implemented with hmac.c and - sha256_generic.c. The following ASCII art illustrates the - implementation: - - - - - - - - The following call sequence is applicable when a caller triggers - an HMAC operation: - - - - - - The AHASH API functions are invoked by the caller. The HMAC - implementation performs its operation as needed. - - - - During initialization of the HMAC cipher, the SHASH cipher type of - SHA256 is instantiated. The cipher handle for the SHA256 instance is - retained. - - - - At one time, the HMAC implementation requires a SHA256 operation - where the SHA256 cipher handle is used. - - - - - - The HMAC instance now invokes the SHASH API with the SHA256 - cipher handle to calculate the message digest. - - - - - - - - Developing Cipher Algorithms - Registering And Unregistering Transformation - - 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. - - - - 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. - - - - 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, - for example when a driver implements multiple transformations. - - - - int crypto_register_alg(struct crypto_alg *alg); - int crypto_register_algs(struct crypto_alg *algs, int count); - - - - The counterparts to those functions are listed below. - - - - int crypto_unregister_alg(struct crypto_alg *alg); - int crypto_unregister_algs(struct crypto_alg *algs, int count); - - - - 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. - - - - The bulk registration/unregistration functions - register/unregister each transformation in the given array of - length count. They handle errors as follows: - - - - - crypto_register_algs() succeeds if and only if it - successfully registers all the given transformations. If an - error occurs partway through, then it rolls back successful - registrations before returning the error code. Note that if - a driver needs to handle registration errors for individual - transformations, then it will need to use the non-bulk - function crypto_register_alg() instead. - - - - - crypto_unregister_algs() tries to unregister all the given - transformations, continuing on error. It logs errors and - always returns zero. - - - - - - - Single-Block Symmetric Ciphers [CIPHER] - - Example of transformations: aes, arc4, ... - - - - 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. - - - Registration specifics - - 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. - - - - See struct cipher_alg below. - - - - Cipher Definition With struct cipher_alg - - Struct cipher_alg defines a single block cipher. - - - - 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. - - - - - KEY ---. PLAINTEXT ---. - v v - .cia_setkey() -> .cia_encrypt() - | - '-----> CIPHERTEXT - - - - - Please note that a pattern where .cia_setkey() is called - multiple times is also valid: - - - - - - KEY1 --. PLAINTEXT1 --. KEY2 --. PLAINTEXT2 --. - v v v v - .cia_setkey() -> .cia_encrypt() -> .cia_setkey() -> .cia_encrypt() - | | - '---> CIPHERTEXT1 '---> CIPHERTEXT2 - - - - - - - Multi-Block Ciphers - - Example of transformations: cbc(aes), ecb(arc4), ... - - - - This section describes the multi-block cipher transformation - implementations. 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. - - - Registration Specifics - - - The registration of multi-block cipher algorithms - is one of the most standard procedures throughout the crypto API. - - - - Note, if a cipher implementation requires a proper alignment - of data, the caller should use the functions of - crypto_skcipher_alignmask() 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. - - - - Cipher Definition With struct blkcipher_alg and ablkcipher_alg - - Struct blkcipher_alg defines a synchronous block cipher whereas - struct ablkcipher_alg defines an asynchronous block cipher. - - - - Please refer to the single block cipher description for schematics - of the block cipher usage. - - - - Specifics Of Asynchronous Multi-Block Cipher - - There are a couple of specifics to the asynchronous interface. - - - - 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. - - - - - Hashing [HASH] - - - Example of transformations: crc32, md5, sha1, sha256,... - - - Registering And Unregistering The Transformation - - - 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: - - - - 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); - - - - The respective counterparts for unregistering the HASH - transformation are as follows: - - - - 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); - - - - Cipher Definition With struct shash_alg and ahash_alg - - 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. - - - - 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 - - - - Here is a schematic of how the .export()/.import() functions are - called when used from another part of the kernel. - - - - 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 - - - - Specifics Of Asynchronous HASH Transformation - - 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. - - - - - - User Space Interface - Introduction - - The concepts of the kernel crypto API visible to kernel space is fully - applicable to the user space interface as well. Therefore, the kernel - crypto API high level discussion for the in-kernel use cases applies - here as well. - - - - The major difference, however, is that user space can only act as a - consumer and never as a provider of a transformation or cipher algorithm. - - - - The following covers the user space interface exported by the kernel - crypto API. A working example of this description is libkcapi that - can be obtained from [1]. That library can be used by user space - applications that require cryptographic services from the kernel. - - - - Some details of the in-kernel kernel crypto API aspects do not - apply to user space, however. This includes the difference between - synchronous and asynchronous invocations. The user space API call - is fully synchronous. - - - - [1] http://www.chronox.de/libkcapi.html - - - - - User Space API General Remarks - - The kernel crypto API is accessible from user space. Currently, - the following ciphers are accessible: - - - - - Message digest including keyed message digest (HMAC, CMAC) - - - - Symmetric ciphers - - - - AEAD ciphers - - - - Random Number Generators - - - - - The interface is provided via socket type using the type AF_ALG. - In addition, the setsockopt option type is SOL_ALG. In case the - user space header files do not export these flags yet, use the - following macros: - - - -#ifndef AF_ALG -#define AF_ALG 38 -#endif -#ifndef SOL_ALG -#define SOL_ALG 279 -#endif - - - - A cipher is accessed with the same name as done for the in-kernel - API calls. This includes the generic vs. unique naming schema for - ciphers as well as the enforcement of priorities for generic names. - - - - To interact with the kernel crypto API, a socket must be - created by the user space application. User space invokes the cipher - operation with the send()/write() system call family. The result of the - cipher operation is obtained with the read()/recv() system call family. - - - - The following API calls assume that the socket descriptor - is already opened by the user space application and discusses only - the kernel crypto API specific invocations. - - - - To initialize the socket interface, the following sequence has to - be performed by the consumer: - - - - - - Create a socket of type AF_ALG with the struct sockaddr_alg - parameter specified below for the different cipher types. - - - - - - Invoke bind with the socket descriptor - - - - - - Invoke accept with the socket descriptor. The accept system call - returns a new file descriptor that is to be used to interact with - the particular cipher instance. When invoking send/write or recv/read - system calls to send data to the kernel or obtain data from the - kernel, the file descriptor returned by accept must be used. - - - - - - In-place Cipher operation - - Just like the in-kernel operation of the kernel crypto API, the user - space interface allows the cipher operation in-place. That means that - the input buffer used for the send/write system call and the output - buffer used by the read/recv system call may be one and the same. - This is of particular interest for symmetric cipher operations where a - copying of the output data to its final destination can be avoided. - - - - If a consumer on the other hand wants to maintain the plaintext and - the ciphertext in different memory locations, all a consumer needs - to do is to provide different memory pointers for the encryption and - decryption operation. - - - - Message Digest API - - The message digest type to be used for the cipher operation is - selected when invoking the bind syscall. bind requires the caller - to provide a filled struct sockaddr data structure. This data - structure must be filled as follows: - - - -struct sockaddr_alg sa = { - .salg_family = AF_ALG, - .salg_type = "hash", /* this selects the hash logic in the kernel */ - .salg_name = "sha1" /* this is the cipher name */ -}; - - - - The salg_type value "hash" applies to message digests and keyed - message digests. Though, a keyed message digest is referenced by - the appropriate salg_name. Please see below for the setsockopt - interface that explains how the key can be set for a keyed message - digest. - - - - Using the send() system call, the application provides the data that - should be processed with the message digest. The send system call - allows the following flags to be specified: - - - - - - MSG_MORE: If this flag is set, the send system call acts like a - message digest update function where the final hash is not - yet calculated. If the flag is not set, the send system call - calculates the final message digest immediately. - - - - - - With the recv() system call, the application can read the message - digest from the kernel crypto API. If the buffer is too small for the - message digest, the flag MSG_TRUNC is set by the kernel. - - - - In order to set a message digest key, the calling application must use - the setsockopt() option of ALG_SET_KEY. If the key is not set the HMAC - operation is performed without the initial HMAC state change caused by - the key. - - - - Symmetric Cipher API - - The operation is very similar to the message digest discussion. - During initialization, the struct sockaddr data structure must be - filled as follows: - - - -struct sockaddr_alg sa = { - .salg_family = AF_ALG, - .salg_type = "skcipher", /* this selects the symmetric cipher */ - .salg_name = "cbc(aes)" /* this is the cipher name */ -}; - - - - Before data can be sent to the kernel using the write/send system - call family, the consumer must set the key. The key setting is - described with the setsockopt invocation below. - - - - Using the sendmsg() system call, the application provides the data that should be processed for encryption or decryption. In addition, the IV is - specified with the data structure provided by the sendmsg() system call. - - - - The sendmsg system call parameter of struct msghdr is embedded into the - struct cmsghdr data structure. See recv(2) and cmsg(3) for more - information on how the cmsghdr data structure is used together with the - send/recv system call family. That cmsghdr data structure holds the - following information specified with a separate header instances: - - - - - - specification of the cipher operation type with one of these flags: - - - - ALG_OP_ENCRYPT - encryption of data - - - ALG_OP_DECRYPT - decryption of data - - - - - - - specification of the IV information marked with the flag ALG_SET_IV - - - - - - The send system call family allows the following flag to be specified: - - - - - - MSG_MORE: If this flag is set, the send system call acts like a - cipher update function where more input data is expected - with a subsequent invocation of the send system call. - - - - - - Note: The kernel reports -EINVAL for any unexpected data. The caller - must make sure that all data matches the constraints given in - /proc/crypto for the selected cipher. - - - - With the recv() system call, the application can read the result of - the cipher operation from the kernel crypto API. The output buffer - must be at least as large as to hold all blocks of the encrypted or - decrypted data. If the output data size is smaller, only as many - blocks are returned that fit into that output buffer size. - - - - AEAD Cipher API - - The operation is very similar to the symmetric cipher discussion. - During initialization, the struct sockaddr data structure must be - filled as follows: - - - -struct sockaddr_alg sa = { - .salg_family = AF_ALG, - .salg_type = "aead", /* this selects the symmetric cipher */ - .salg_name = "gcm(aes)" /* this is the cipher name */ -}; - - - - Before data can be sent to the kernel using the write/send system - call family, the consumer must set the key. The key setting is - described with the setsockopt invocation below. - - - - In addition, before data can be sent to the kernel using the - write/send system call family, the consumer must set the authentication - tag size. To set the authentication tag size, the caller must use the - setsockopt invocation described below. - - - - Using the sendmsg() system call, the application provides the data that should be processed for encryption or decryption. In addition, the IV is - specified with the data structure provided by the sendmsg() system call. - - - - The sendmsg system call parameter of struct msghdr is embedded into the - struct cmsghdr data structure. See recv(2) and cmsg(3) for more - information on how the cmsghdr data structure is used together with the - send/recv system call family. That cmsghdr data structure holds the - following information specified with a separate header instances: - - - - - - specification of the cipher operation type with one of these flags: - - - - ALG_OP_ENCRYPT - encryption of data - - - ALG_OP_DECRYPT - decryption of data - - - - - - - specification of the IV information marked with the flag ALG_SET_IV - - - - - - specification of the associated authentication data (AAD) with the - flag ALG_SET_AEAD_ASSOCLEN. The AAD is sent to the kernel together - with the plaintext / ciphertext. See below for the memory structure. - - - - - - The send system call family allows the following flag to be specified: - - - - - - MSG_MORE: If this flag is set, the send system call acts like a - cipher update function where more input data is expected - with a subsequent invocation of the send system call. - - - - - - Note: The kernel reports -EINVAL for any unexpected data. The caller - must make sure that all data matches the constraints given in - /proc/crypto for the selected cipher. - - - - With the recv() system call, the application can read the result of - the cipher operation from the kernel crypto API. The output buffer - must be at least as large as defined with the memory structure below. - If the output data size is smaller, the cipher operation is not performed. - - - - The authenticated decryption operation may indicate an integrity error. - Such breach in integrity is marked with the -EBADMSG error code. - - - AEAD Memory Structure - - The AEAD cipher operates with the following information that - is communicated between user and kernel space as one data stream: - - - - - plaintext or ciphertext - - - - associated authentication data (AAD) - - - - authentication tag - - - - - The sizes of the AAD and the authentication tag are provided with - the sendmsg and setsockopt calls (see there). As the kernel knows - the size of the entire data stream, the kernel is now able to - calculate the right offsets of the data components in the data - stream. - - - - The user space caller must arrange the aforementioned information - in the following order: - - - - - - AEAD encryption input: AAD || plaintext - - - - - - AEAD decryption input: AAD || ciphertext || authentication tag - - - - - - The output buffer the user space caller provides must be at least as - large to hold the following data: - - - - - - AEAD encryption output: ciphertext || authentication tag - - - - - - AEAD decryption output: plaintext - - - - - - - Random Number Generator API - - Again, the operation is very similar to the other APIs. - During initialization, the struct sockaddr data structure must be - filled as follows: - - - -struct sockaddr_alg sa = { - .salg_family = AF_ALG, - .salg_type = "rng", /* this selects the symmetric cipher */ - .salg_name = "drbg_nopr_sha256" /* this is the cipher name */ -}; - - - - Depending on the RNG type, the RNG must be seeded. The seed is provided - using the setsockopt interface to set the key. For example, the - ansi_cprng requires a seed. The DRBGs do not require a seed, but - may be seeded. - - - - Using the read()/recvmsg() system calls, random numbers can be obtained. - The kernel generates at most 128 bytes in one call. If user space - requires more data, multiple calls to read()/recvmsg() must be made. - - - - WARNING: The user space caller may invoke the initially mentioned - accept system call multiple times. In this case, the returned file - descriptors have the same state. - - - - - Zero-Copy Interface - - In addition to the send/write/read/recv system call family, the AF_ALG - interface can be accessed with the zero-copy interface of splice/vmsplice. - As the name indicates, the kernel tries to avoid a copy operation into - kernel space. - - - - The zero-copy operation requires data to be aligned at the page boundary. - Non-aligned data can be used as well, but may require more operations of - the kernel which would defeat the speed gains obtained from the zero-copy - interface. - - - - The system-interent limit for the size of one zero-copy operation is - 16 pages. If more data is to be sent to AF_ALG, user space must slice - the input into segments with a maximum size of 16 pages. - - - - Zero-copy can be used with the following code example (a complete working - example is provided with libkcapi): - - - -int pipes[2]; - -pipe(pipes); -/* input data in iov */ -vmsplice(pipes[1], iov, iovlen, SPLICE_F_GIFT); -/* opfd is the file descriptor returned from accept() system call */ -splice(pipes[0], NULL, opfd, NULL, ret, 0); -read(opfd, out, outlen); - - - - - Setsockopt Interface - - In addition to the read/recv and send/write system call handling - to send and retrieve data subject to the cipher operation, a consumer - also needs to set the additional information for the cipher operation. - This additional information is set using the setsockopt system call - that must be invoked with the file descriptor of the open cipher - (i.e. the file descriptor returned by the accept system call). - - - - Each setsockopt invocation must use the level SOL_ALG. - - - - The setsockopt interface allows setting the following data using - the mentioned optname: - - - - - - ALG_SET_KEY -- Setting the key. Key setting is applicable to: - - - - the skcipher cipher type (symmetric ciphers) - - - the hash cipher type (keyed message digests) - - - the AEAD cipher type - - - the RNG cipher type to provide the seed - - - - - - - ALG_SET_AEAD_AUTHSIZE -- Setting the authentication tag size - for AEAD ciphers. For a encryption operation, the authentication - tag of the given size will be generated. For a decryption operation, - the provided ciphertext is assumed to contain an authentication tag - of the given size (see section about AEAD memory layout below). - - - - - - - User space API example - - Please see [1] for libkcapi which provides an easy-to-use wrapper - around the aforementioned Netlink kernel interface. [1] also contains - a test application that invokes all libkcapi API calls. - - - - [1] http://www.chronox.de/libkcapi.html - - - - - - - Programming Interface - - Please note that the kernel crypto API contains the AEAD givcrypt - API (crypto_aead_giv* and aead_givcrypt_* function calls in - include/crypto/aead.h). This API is obsolete and will be removed - in the future. To obtain the functionality of an AEAD cipher with - internal IV generation, use the IV generator as a regular cipher. - For example, rfc4106(gcm(aes)) is the AEAD cipher with external - IV generation and seqniv(rfc4106(gcm(aes))) implies that the kernel - crypto API generates the IV. Different IV generators are available. - - Block Cipher Context Data Structures -!Pinclude/linux/crypto.h Block Cipher Context Data Structures -!Finclude/crypto/aead.h aead_request - - Block Cipher Algorithm Definitions -!Pinclude/linux/crypto.h Block Cipher Algorithm Definitions -!Finclude/linux/crypto.h crypto_alg -!Finclude/linux/crypto.h ablkcipher_alg -!Finclude/crypto/aead.h aead_alg -!Finclude/linux/crypto.h blkcipher_alg -!Finclude/linux/crypto.h cipher_alg -!Finclude/crypto/rng.h rng_alg - - Symmetric Key Cipher API -!Pinclude/crypto/skcipher.h Symmetric Key Cipher API -!Finclude/crypto/skcipher.h crypto_alloc_skcipher -!Finclude/crypto/skcipher.h crypto_free_skcipher -!Finclude/crypto/skcipher.h crypto_has_skcipher -!Finclude/crypto/skcipher.h crypto_skcipher_ivsize -!Finclude/crypto/skcipher.h crypto_skcipher_blocksize -!Finclude/crypto/skcipher.h crypto_skcipher_setkey -!Finclude/crypto/skcipher.h crypto_skcipher_reqtfm -!Finclude/crypto/skcipher.h crypto_skcipher_encrypt -!Finclude/crypto/skcipher.h crypto_skcipher_decrypt - - Symmetric Key Cipher Request Handle -!Pinclude/crypto/skcipher.h Symmetric Key Cipher Request Handle -!Finclude/crypto/skcipher.h crypto_skcipher_reqsize -!Finclude/crypto/skcipher.h skcipher_request_set_tfm -!Finclude/crypto/skcipher.h skcipher_request_alloc -!Finclude/crypto/skcipher.h skcipher_request_free -!Finclude/crypto/skcipher.h skcipher_request_set_callback -!Finclude/crypto/skcipher.h skcipher_request_set_crypt - - Asynchronous Block Cipher API - Deprecated -!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 - - Asynchronous Cipher Request Handle - Deprecated -!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 - - Authenticated Encryption With Associated Data (AEAD) Cipher API -!Pinclude/crypto/aead.h Authenticated Encryption With Associated Data (AEAD) Cipher API -!Finclude/crypto/aead.h crypto_alloc_aead -!Finclude/crypto/aead.h crypto_free_aead -!Finclude/crypto/aead.h crypto_aead_ivsize -!Finclude/crypto/aead.h crypto_aead_authsize -!Finclude/crypto/aead.h crypto_aead_blocksize -!Finclude/crypto/aead.h crypto_aead_setkey -!Finclude/crypto/aead.h crypto_aead_setauthsize -!Finclude/crypto/aead.h crypto_aead_encrypt -!Finclude/crypto/aead.h crypto_aead_decrypt - - Asynchronous AEAD Request Handle -!Pinclude/crypto/aead.h Asynchronous AEAD Request Handle -!Finclude/crypto/aead.h crypto_aead_reqsize -!Finclude/crypto/aead.h aead_request_set_tfm -!Finclude/crypto/aead.h aead_request_alloc -!Finclude/crypto/aead.h aead_request_free -!Finclude/crypto/aead.h aead_request_set_callback -!Finclude/crypto/aead.h aead_request_set_crypt -!Finclude/crypto/aead.h aead_request_set_ad - - Synchronous Block Cipher API - Deprecated -!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 - - Single Block Cipher API -!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 - - Message Digest Algorithm Definitions -!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 - - Asynchronous Message Digest API -!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 - - Asynchronous Hash Request Handle -!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 - - Synchronous Message Digest API -!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 - - Crypto API Random Number API -!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_generate -!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 - - Asymmetric Cipher API -!Pinclude/crypto/akcipher.h Generic Public Key API -!Finclude/crypto/akcipher.h akcipher_alg -!Finclude/crypto/akcipher.h akcipher_request -!Finclude/crypto/akcipher.h crypto_alloc_akcipher -!Finclude/crypto/akcipher.h crypto_free_akcipher -!Finclude/crypto/akcipher.h crypto_akcipher_set_pub_key -!Finclude/crypto/akcipher.h crypto_akcipher_set_priv_key - - Asymmetric Cipher Request Handle -!Finclude/crypto/akcipher.h akcipher_request_alloc -!Finclude/crypto/akcipher.h akcipher_request_free -!Finclude/crypto/akcipher.h akcipher_request_set_callback -!Finclude/crypto/akcipher.h akcipher_request_set_crypt -!Finclude/crypto/akcipher.h crypto_akcipher_maxsize -!Finclude/crypto/akcipher.h crypto_akcipher_encrypt -!Finclude/crypto/akcipher.h crypto_akcipher_decrypt -!Finclude/crypto/akcipher.h crypto_akcipher_sign -!Finclude/crypto/akcipher.h crypto_akcipher_verify - - - - Code Examples - Code Example For Symmetric Key Cipher Operation - - -struct tcrypt_result { - struct completion completion; - int err; -}; - -/* tie all data structures together */ -struct skcipher_def { - struct scatterlist sg; - struct crypto_skcipher *tfm; - struct skcipher_request *req; - struct tcrypt_result result; -}; - -/* Callback function */ -static void test_skcipher_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_skcipher_encdec(struct skcipher_def *sk, - int enc) -{ - int rc = 0; - - if (enc) - rc = crypto_skcipher_encrypt(sk->req); - else - rc = crypto_skcipher_decrypt(sk->req); - - switch (rc) { - case 0: - break; - case -EINPROGRESS: - case -EBUSY: - rc = wait_for_completion_interruptible( - &sk->result.completion); - if (!rc && !sk->result.err) { - reinit_completion(&sk->result.completion); - break; - } - default: - pr_info("skcipher encrypt returned with %d result %d\n", - rc, sk->result.err); - break; - } - init_completion(&sk->result.completion); - - return rc; -} - -/* Initialize and trigger cipher operation */ -static int test_skcipher(void) -{ - struct skcipher_def sk; - struct crypto_skcipher *skcipher = NULL; - struct skcipher_request *req = NULL; - char *scratchpad = NULL; - char *ivdata = NULL; - unsigned char key[32]; - int ret = -EFAULT; - - skcipher = crypto_alloc_skcipher("cbc-aes-aesni", 0, 0); - if (IS_ERR(skcipher)) { - pr_info("could not allocate skcipher handle\n"); - return PTR_ERR(skcipher); - } - - req = skcipher_request_alloc(skcipher, GFP_KERNEL); - if (!req) { - pr_info("could not allocate skcipher request\n"); - ret = -ENOMEM; - goto out; - } - - skcipher_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG, - test_skcipher_cb, - &sk.result); - - /* AES 256 with random key */ - get_random_bytes(&key, 32); - if (crypto_skcipher_setkey(skcipher, 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); - - sk.tfm = skcipher; - sk.req = req; - - /* We encrypt one block */ - sg_init_one(&sk.sg, scratchpad, 16); - skcipher_request_set_crypt(req, &sk.sg, &sk.sg, 16, ivdata); - init_completion(&sk.result.completion); - - /* encrypt data */ - ret = test_skcipher_encdec(&sk, 1); - if (ret) - goto out; - - pr_info("Encryption triggered successfully\n"); - -out: - if (skcipher) - crypto_free_skcipher(skcipher); - if (req) - skcipher_request_free(req); - if (ivdata) - kfree(ivdata); - if (scratchpad) - kfree(scratchpad); - return ret; -} - - - - Code Example For Use of Operational State Memory With SHASH - - -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; -} - - - - Code Example For Random Number Generator Usage - - -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; -} - - - - -- 2.7.4