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crypto: doc - cipher data structures
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The data structure of struct crypto_alg together with various other
data structures needed by cipher developers is documented wit all
parameters that can be set by a developer of a transformation. All
parameters that are internal to the crypto API are marked as such.

Signed-off-by: Stephan Mueller <smueller@chronox.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
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Stephan Mueller authored and Herbert Xu committed Nov 13, 2014
1 parent 968ab29 commit 0d7f488
Showing 1 changed file with 243 additions and 3 deletions.
246 changes: 243 additions & 3 deletions include/linux/crypto.h
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Original file line number Diff line number Diff line change
Expand Up @@ -127,6 +127,13 @@ struct skcipher_givcrypt_request;

typedef void (*crypto_completion_t)(struct crypto_async_request *req, int err);

/**
* DOC: Block Cipher Context Data Structures
*
* These data structures define the operating context for each block cipher
* type.
*/

struct crypto_async_request {
struct list_head list;
crypto_completion_t complete;
Expand Down Expand Up @@ -194,9 +201,63 @@ struct hash_desc {
u32 flags;
};

/*
* Algorithms: modular crypto algorithm implementations, managed
* via crypto_register_alg() and crypto_unregister_alg().
/**
* DOC: Block Cipher Algorithm Definitions
*
* These data structures define modular crypto algorithm implementations,
* managed via crypto_register_alg() and crypto_unregister_alg().
*/

/**
* struct ablkcipher_alg - asynchronous block cipher definition
* @min_keysize: Minimum key size supported by the transformation. This is the
* smallest key length supported by this transformation algorithm.
* This must be set to one of the pre-defined values as this is
* not hardware specific. Possible values for this field can be
* found via git grep "_MIN_KEY_SIZE" include/crypto/
* @max_keysize: Maximum key size supported by the transformation. This is the
* largest key length supported by this transformation algorithm.
* This must be set to one of the pre-defined values as this is
* not hardware specific. Possible values for this field can be
* found via git grep "_MAX_KEY_SIZE" include/crypto/
* @setkey: Set key for the transformation. This function is used to either
* program a supplied key into the hardware or store the key in the
* transformation context for programming it later. Note that this
* function does modify the transformation context. This function can
* be called multiple times during the existence of the transformation
* object, so one must make sure the key is properly reprogrammed into
* the hardware. This function is also responsible for checking the key
* length for validity. In case a software fallback was put in place in
* the @cra_init call, this function might need to use the fallback if
* the algorithm doesn't support all of the key sizes.
* @encrypt: Encrypt a scatterlist of blocks. This function is used to encrypt
* the supplied scatterlist containing the blocks of data. The crypto
* API consumer is responsible for aligning the entries of the
* scatterlist properly and making sure the chunks are correctly
* sized. In case a software fallback was put in place in the
* @cra_init call, this function might need to use the fallback if
* the algorithm doesn't support all of the key sizes. In case the
* key was stored in transformation context, the key might need to be
* re-programmed into the hardware in this function. This function
* shall not modify the transformation context, as this function may
* be called in parallel with the same transformation object.
* @decrypt: Decrypt a single block. This is a reverse counterpart to @encrypt
* and the conditions are exactly the same.
* @givencrypt: Update the IV for encryption. With this function, a cipher
* implementation may provide the function on how to update the IV
* for encryption.
* @givdecrypt: Update the IV for decryption. This is the reverse of
* @givencrypt .
* @geniv: The transformation implementation may use an "IV generator" provided
* by the kernel crypto API. Several use cases have a predefined
* approach how IVs are to be updated. For such use cases, the kernel
* crypto API provides ready-to-use implementations that can be
* referenced with this variable.
* @ivsize: IV size applicable for transformation. The consumer must provide an
* IV of exactly that size to perform the encrypt or decrypt operation.
*
* All fields except @givencrypt , @givdecrypt , @geniv and @ivsize are
* mandatory and must be filled.
*/
struct ablkcipher_alg {
int (*setkey)(struct crypto_ablkcipher *tfm, const u8 *key,
Expand All @@ -213,6 +274,32 @@ struct ablkcipher_alg {
unsigned int ivsize;
};

/**
* struct aead_alg - AEAD cipher definition
* @maxauthsize: Set the maximum authentication tag size supported by the
* transformation. A transformation may support smaller tag sizes.
* As the authentication tag is a message digest to ensure the
* integrity of the encrypted data, a consumer typically wants the
* largest authentication tag possible as defined by this
* variable.
* @setauthsize: Set authentication size for the AEAD transformation. This
* function is used to specify the consumer requested size of the
* authentication tag to be either generated by the transformation
* during encryption or the size of the authentication tag to be
* supplied during the decryption operation. This function is also
* responsible for checking the authentication tag size for
* validity.
* @setkey: see struct ablkcipher_alg
* @encrypt: see struct ablkcipher_alg
* @decrypt: see struct ablkcipher_alg
* @givencrypt: see struct ablkcipher_alg
* @givdecrypt: see struct ablkcipher_alg
* @geniv: see struct ablkcipher_alg
* @ivsize: see struct ablkcipher_alg
*
* All fields except @givencrypt , @givdecrypt , @geniv and @ivsize are
* mandatory and must be filled.
*/
struct aead_alg {
int (*setkey)(struct crypto_aead *tfm, const u8 *key,
unsigned int keylen);
Expand All @@ -228,6 +315,18 @@ struct aead_alg {
unsigned int maxauthsize;
};

/**
* struct blkcipher_alg - synchronous block cipher definition
* @min_keysize: see struct ablkcipher_alg
* @max_keysize: see struct ablkcipher_alg
* @setkey: see struct ablkcipher_alg
* @encrypt: see struct ablkcipher_alg
* @decrypt: see struct ablkcipher_alg
* @geniv: see struct ablkcipher_alg
* @ivsize: see struct ablkcipher_alg
*
* All fields except @geniv and @ivsize are mandatory and must be filled.
*/
struct blkcipher_alg {
int (*setkey)(struct crypto_tfm *tfm, const u8 *key,
unsigned int keylen);
Expand All @@ -245,6 +344,53 @@ struct blkcipher_alg {
unsigned int ivsize;
};

/**
* struct cipher_alg - single-block symmetric ciphers definition
* @cia_min_keysize: Minimum key size supported by the transformation. This is
* the smallest key length supported by this transformation
* algorithm. This must be set to one of the pre-defined
* values as this is not hardware specific. Possible values
* for this field can be found via git grep "_MIN_KEY_SIZE"
* include/crypto/
* @cia_max_keysize: Maximum key size supported by the transformation. This is
* the largest key length supported by this transformation
* algorithm. This must be set to one of the pre-defined values
* as this is not hardware specific. Possible values for this
* field can be found via git grep "_MAX_KEY_SIZE"
* include/crypto/
* @cia_setkey: Set key for the transformation. This function is used to either
* program a supplied key into the hardware or store the key in the
* transformation context for programming it later. Note that this
* function does modify the transformation context. This function
* can be called multiple times during the existence of the
* transformation object, so one must make sure the key is properly
* reprogrammed into the hardware. This function is also
* responsible for checking the key length for validity.
* @cia_encrypt: Encrypt a single block. This function is used to encrypt a
* single block of data, which must be @cra_blocksize big. This
* always operates on a full @cra_blocksize and it is not possible
* to encrypt a block of smaller size. The supplied buffers must
* therefore also be at least of @cra_blocksize size. Both the
* input and output buffers are always aligned to @cra_alignmask.
* In case either of the input or output buffer supplied by user
* of the crypto API is not aligned to @cra_alignmask, the crypto
* API will re-align the buffers. The re-alignment means that a
* new buffer will be allocated, the data will be copied into the
* new buffer, then the processing will happen on the new buffer,
* then the data will be copied back into the original buffer and
* finally the new buffer will be freed. In case a software
* fallback was put in place in the @cra_init call, this function
* might need to use the fallback if the algorithm doesn't support
* all of the key sizes. In case the key was stored in
* transformation context, the key might need to be re-programmed
* into the hardware in this function. This function shall not
* modify the transformation context, as this function may be
* called in parallel with the same transformation object.
* @cia_decrypt: Decrypt a single block. This is a reverse counterpart to
* @cia_encrypt, and the conditions are exactly the same.
*
* All fields are mandatory and must be filled.
*/
struct cipher_alg {
unsigned int cia_min_keysize;
unsigned int cia_max_keysize;
Expand All @@ -261,6 +407,25 @@ struct compress_alg {
unsigned int slen, u8 *dst, unsigned int *dlen);
};

/**
* struct rng_alg - random number generator definition
* @rng_make_random: The function defined by this variable obtains a random
* number. The random number generator transform must generate
* the random number out of the context provided with this
* call.
* @rng_reset: Reset of the random number generator by clearing the entire state.
* With the invocation of this function call, the random number
* generator shall completely reinitialize its state. If the random
* number generator requires a seed for setting up a new state,
* the seed must be provided by the consumer while invoking this
* function. The required size of the seed is defined with
* @seedsize .
* @seedsize: The seed size required for a random number generator
* initialization defined with this variable. Some random number
* generators like the SP800-90A DRBG does not require a seed as the
* seeding is implemented internally without the need of support by
* the consumer. In this case, the seed size is set to zero.
*/
struct rng_alg {
int (*rng_make_random)(struct crypto_rng *tfm, u8 *rdata,
unsigned int dlen);
Expand All @@ -277,6 +442,81 @@ struct rng_alg {
#define cra_compress cra_u.compress
#define cra_rng cra_u.rng

/**
* struct crypto_alg - definition of a cryptograpic cipher algorithm
* @cra_flags: Flags describing this transformation. See include/linux/crypto.h
* CRYPTO_ALG_* flags for the flags which go in here. Those are
* used for fine-tuning the description of the transformation
* algorithm.
* @cra_blocksize: Minimum block size of this transformation. The size in bytes
* of the smallest possible unit which can be transformed with
* this algorithm. The users must respect this value.
* In case of HASH transformation, it is possible for a smaller
* block than @cra_blocksize to be passed to the crypto API for
* transformation, in case of any other transformation type, an
* error will be returned upon any attempt to transform smaller
* than @cra_blocksize chunks.
* @cra_ctxsize: Size of the operational context of the transformation. This
* value informs the kernel crypto API about the memory size
* needed to be allocated for the transformation context.
* @cra_alignmask: Alignment mask for the input and output data buffer. The data
* buffer containing the input data for the algorithm must be
* aligned to this alignment mask. The data buffer for the
* output data must be aligned to this alignment mask. Note that
* the Crypto API will do the re-alignment in software, but
* only under special conditions and there is a performance hit.
* The re-alignment happens at these occasions for different
* @cra_u types: cipher -- For both input data and output data
* buffer; ahash -- For output hash destination buf; shash --
* For output hash destination buf.
* This is needed on hardware which is flawed by design and
* cannot pick data from arbitrary addresses.
* @cra_priority: Priority of this transformation implementation. In case
* multiple transformations with same @cra_name are available to
* the Crypto API, the kernel will use the one with highest
* @cra_priority.
* @cra_name: Generic name (usable by multiple implementations) of the
* transformation algorithm. This is the name of the transformation
* itself. This field is used by the kernel when looking up the
* providers of particular transformation.
* @cra_driver_name: Unique name of the transformation provider. This is the
* name of the provider of the transformation. This can be any
* arbitrary value, but in the usual case, this contains the
* name of the chip or provider and the name of the
* transformation algorithm.
* @cra_type: Type of the cryptographic transformation. This is a pointer to
* struct crypto_type, which implements callbacks common for all
* trasnformation types. There are multiple options:
* &crypto_blkcipher_type, &crypto_ablkcipher_type,
* &crypto_ahash_type, &crypto_aead_type, &crypto_rng_type.
* This field might be empty. In that case, there are no common
* callbacks. This is the case for: cipher, compress, shash.
* @cra_u: Callbacks implementing the transformation. This is a union of
* multiple structures. Depending on the type of transformation selected
* by @cra_type and @cra_flags above, the associated structure must be
* filled with callbacks. This field might be empty. This is the case
* for ahash, shash.
* @cra_init: Initialize the cryptographic transformation object. This function
* is used to initialize the cryptographic transformation object.
* This function is called only once at the instantiation time, right
* after the transformation context was allocated. In case the
* cryptographic hardware has some special requirements which need to
* be handled by software, this function shall check for the precise
* requirement of the transformation and put any software fallbacks
* in place.
* @cra_exit: Deinitialize the cryptographic transformation object. This is a
* counterpart to @cra_init, used to remove various changes set in
* @cra_init.
* @cra_module: Owner of this transformation implementation. Set to THIS_MODULE
* @cra_list: internally used
* @cra_users: internally used
* @cra_refcnt: internally used
* @cra_destroy: internally used
*
* The struct crypto_alg describes a generic Crypto API algorithm and is common
* for all of the transformations. Any variable not documented here shall not
* be used by a cipher implementation as it is internal to the Crypto API.
*/
struct crypto_alg {
struct list_head cra_list;
struct list_head cra_users;
Expand Down

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