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crypto: doc - AEAD API documentation 

The API function calls exported by the kernel crypto API for AEAD
ciphers to be used by consumers are documented.

Signed-off-by: Stephan Mueller <smueller@chronox.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
This commit is contained in:
Stephan Mueller 2014-11-12 05:29:00 +01:00 committed by Herbert Xu
parent f13ec330a7
commit fced7b0262
1 changed files with 251 additions and 0 deletions
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251
include/linux/crypto.h
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@ -1174,11 +1174,55 @@ static inline void ablkcipher_request_set_crypt(
req->info = iv;
}
/**
* DOC: Authenticated Encryption With Associated Data (AEAD) Cipher API
*
* The AEAD cipher API is used with the ciphers of type CRYPTO_ALG_TYPE_AEAD
* (listed as type "aead" in /proc/crypto)
*
* The most prominent examples for this type of encryption is GCM and CCM.
* However, the kernel supports other types of AEAD ciphers which are defined
* with the following cipher string:
*
* authenc(keyed message digest, block cipher)
*
* For example: authenc(hmac(sha256), cbc(aes))
*
* The example code provided for the asynchronous block cipher operation
* applies here as well. Naturally all *ablkcipher* symbols must be exchanged
* the *aead* pendants discussed in the following. In addtion, for the AEAD
* operation, the aead_request_set_assoc function must be used to set the
* pointer to the associated data memory location before performing the
* encryption or decryption operation. In case of an encryption, the associated
* data memory is filled during the encryption operation. For decryption, the
* associated data memory must contain data that is used to verify the integrity
* of the decrypted data. Another deviation from the asynchronous block cipher
* operation is that the caller should explicitly check for -EBADMSG of the
* crypto_aead_decrypt. That error indicates an authentication error, i.e.
* a breach in the integrity of the message. In essence, that -EBADMSG error
* code is the key bonus an AEAD cipher has over "standard" block chaining
* modes.
*/
static inline struct crypto_aead *__crypto_aead_cast(struct crypto_tfm *tfm)
{
return (struct crypto_aead *)tfm;
}
/**
* crypto_alloc_aead() - allocate AEAD cipher handle
* @alg_name: is the cra_name / name or cra_driver_name / driver name of the
* AEAD cipher
* @type: specifies the type of the cipher
* @mask: specifies the mask for the cipher
*
* Allocate a cipher handle for an AEAD. The returned struct
* crypto_aead is the cipher handle that is required for any subsequent
* API invocation for that AEAD.
*
* Return: allocated cipher handle in case of success; IS_ERR() is true in case
* of an error, PTR_ERR() returns the error code.
*/
struct crypto_aead *crypto_alloc_aead(const char *alg_name, u32 type, u32 mask);
static inline struct crypto_tfm *crypto_aead_tfm(struct crypto_aead *tfm)
@ -1186,6 +1230,10 @@ static inline struct crypto_tfm *crypto_aead_tfm(struct crypto_aead *tfm)
return &tfm->base;
}
/**
* crypto_free_aead() - zeroize and free aead handle
* @tfm: cipher handle to be freed
*/
static inline void crypto_free_aead(struct crypto_aead *tfm)
{
crypto_free_tfm(crypto_aead_tfm(tfm));
@ -1196,16 +1244,47 @@ static inline struct aead_tfm *crypto_aead_crt(struct crypto_aead *tfm)
return &crypto_aead_tfm(tfm)->crt_aead;
}
/**
* crypto_aead_ivsize() - obtain IV size
* @tfm: cipher handle
*
* The size of the IV for the aead referenced by the cipher handle is
* returned. This IV size may be zero if the cipher does not need an IV.
*
* Return: IV size in bytes
*/
static inline unsigned int crypto_aead_ivsize(struct crypto_aead *tfm)
{
return crypto_aead_crt(tfm)->ivsize;
}
/**
* crypto_aead_authsize() - obtain maximum authentication data size
* @tfm: cipher handle
*
* The maximum size of the authentication data for the AEAD cipher referenced
* by the AEAD cipher handle is returned. The authentication data size may be
* zero if the cipher implements a hard-coded maximum.
*
* The authentication data may also be known as "tag value".
*
* Return: authentication data size / tag size in bytes
*/
static inline unsigned int crypto_aead_authsize(struct crypto_aead *tfm)
{
return crypto_aead_crt(tfm)->authsize;
}
/**
* crypto_aead_blocksize() - obtain block size of cipher
* @tfm: cipher handle
*
* The block size for the AEAD referenced with the cipher handle is returned.
* The caller may use that information to allocate appropriate memory for the
* data returned by the encryption or decryption operation
*
* Return: block size of cipher
*/
static inline unsigned int crypto_aead_blocksize(struct crypto_aead *tfm)
{
return crypto_tfm_alg_blocksize(crypto_aead_tfm(tfm));
@ -1231,6 +1310,22 @@ static inline void crypto_aead_clear_flags(struct crypto_aead *tfm, u32 flags)
crypto_tfm_clear_flags(crypto_aead_tfm(tfm), flags);
}
/**
* crypto_aead_setkey() - set key for cipher
* @tfm: cipher handle
* @key: buffer holding the key
* @keylen: length of the key in bytes
*
* The caller provided key is set for the AEAD referenced by the cipher
* handle.
*
* Note, the key length determines the cipher type. Many block ciphers implement
* different cipher modes depending on the key size, such as AES-128 vs AES-192
* vs. AES-256. When providing a 16 byte key for an AES cipher handle, AES-128
* is performed.
*
* Return: 0 if the setting of the key was successful; < 0 if an error occurred
*/
static inline int crypto_aead_setkey(struct crypto_aead *tfm, const u8 *key,
unsigned int keylen)
{
@ -1239,6 +1334,16 @@ static inline int crypto_aead_setkey(struct crypto_aead *tfm, const u8 *key,
return crt->setkey(crt->base, key, keylen);
}
/**
* crypto_aead_setauthsize() - set authentication data size
* @tfm: cipher handle
* @authsize: size of the authentication data / tag in bytes
*
* Set the authentication data size / tag size. AEAD requires an authentication
* tag (or MAC) in addition to the associated data.
*
* Return: 0 if the setting of the key was successful; < 0 if an error occurred
*/
int crypto_aead_setauthsize(struct crypto_aead *tfm, unsigned int authsize);
static inline struct crypto_aead *crypto_aead_reqtfm(struct aead_request *req)
@ -1246,27 +1351,105 @@ static inline struct crypto_aead *crypto_aead_reqtfm(struct aead_request *req)
return __crypto_aead_cast(req->base.tfm);
}
/**
* crypto_aead_encrypt() - encrypt plaintext
* @req: reference to the aead_request handle that holds all information
* needed to perform the cipher operation
*
* Encrypt plaintext data using the aead_request handle. That data structure
* and how it is filled with data is discussed with the aead_request_*
* functions.
*
* IMPORTANT NOTE The encryption operation creates the authentication data /
* tag. That data is concatenated with the created ciphertext.
* The ciphertext memory size is therefore the given number of
* block cipher blocks + the size defined by the
* crypto_aead_setauthsize invocation. The caller must ensure
* that sufficient memory is available for the ciphertext and
* the authentication tag.
*
* Return: 0 if the cipher operation was successful; < 0 if an error occurred
*/
static inline int crypto_aead_encrypt(struct aead_request *req)
{
return crypto_aead_crt(crypto_aead_reqtfm(req))->encrypt(req);
}
/**
* crypto_aead_decrypt() - decrypt ciphertext
* @req: reference to the ablkcipher_request handle that holds all information
* needed to perform the cipher operation
*
* Decrypt ciphertext data using the aead_request handle. That data structure
* and how it is filled with data is discussed with the aead_request_*
* functions.
*
* IMPORTANT NOTE The caller must concatenate the ciphertext followed by the
* authentication data / tag. That authentication data / tag
* must have the size defined by the crypto_aead_setauthsize
* invocation.
*
*
* Return: 0 if the cipher operation was successful; -EBADMSG: The AEAD
* cipher operation performs the authentication of the data during the
* decryption operation. Therefore, the function returns this error if
* the authentication of the ciphertext was unsuccessful (i.e. the
* integrity of the ciphertext or the associated data was violated);
* < 0 if an error occurred.
*/
static inline int crypto_aead_decrypt(struct aead_request *req)
{
return crypto_aead_crt(crypto_aead_reqtfm(req))->decrypt(req);
}
/**
* DOC: Asynchronous AEAD Request Handle
*
* The aead_request data structure contains all pointers to data required for
* the AEAD cipher operation. This includes the cipher handle (which can be
* used by multiple aead_request instances), pointer to plaintext and
* ciphertext, asynchronous callback function, etc. It acts as a handle to the
* aead_request_* API calls in a similar way as AEAD handle to the
* crypto_aead_* API calls.
*/
/**
* crypto_aead_reqsize() - obtain size of the request data structure
* @tfm: cipher handle
*
* Return: number of bytes
*/
static inline unsigned int crypto_aead_reqsize(struct crypto_aead *tfm)
{
return crypto_aead_crt(tfm)->reqsize;
}
/**
* aead_request_set_tfm() - update cipher handle reference in request
* @req: request handle to be modified
* @tfm: cipher handle that shall be added to the request handle
*
* Allow the caller to replace the existing aead handle in the request
* data structure with a different one.
*/
static inline void aead_request_set_tfm(struct aead_request *req,
struct crypto_aead *tfm)
{
req->base.tfm = crypto_aead_tfm(crypto_aead_crt(tfm)->base);
}
/**
* aead_request_alloc() - allocate request data structure
* @tfm: cipher handle to be registered with the request
* @gfp: memory allocation flag that is handed to kmalloc by the API call.
*
* Allocate the request data structure that must be used with the AEAD
* encrypt and decrypt API calls. During the allocation, the provided aead
* handle is registered in the request data structure.
*
* Return: allocated request handle in case of success; IS_ERR() is true in case
* of an error, PTR_ERR() returns the error code.
*/
static inline struct aead_request *aead_request_alloc(struct crypto_aead *tfm,
gfp_t gfp)
{
@ -1280,11 +1463,40 @@ static inline struct aead_request *aead_request_alloc(struct crypto_aead *tfm,
return req;
}
/**
* aead_request_free() - zeroize and free request data structure
* @req: request data structure cipher handle to be freed
*/
static inline void aead_request_free(struct aead_request *req)
{
kzfree(req);
}
/**
* aead_request_set_callback() - set asynchronous callback function
* @req: request handle
* @flags: specify zero or an ORing of the flags
* CRYPTO_TFM_REQ_MAY_BACKLOG the request queue may back log and
* increase the wait queue beyond the initial maximum size;
* CRYPTO_TFM_REQ_MAY_SLEEP the request processing may sleep
* @compl: callback function pointer to be registered with the request handle
* @data: The data pointer refers to memory that is not used by the kernel
* crypto API, but provided to the callback function for it to use. Here,
* the caller can provide a reference to memory the callback function can
* operate on. As the callback function is invoked asynchronously to the
* related functionality, it may need to access data structures of the
* related functionality which can be referenced using this pointer. The
* callback function can access the memory via the "data" field in the
* crypto_async_request data structure provided to the callback function.
*
* Setting the callback function that is triggered once the cipher operation
* completes
*
* The callback function is registered with the aead_request handle and
* must comply with the following template:
*
* void callback_function(struct crypto_async_request *req, int error)
*/
static inline void aead_request_set_callback(struct aead_request *req,
u32 flags,
crypto_completion_t compl,
@ -1295,6 +1507,36 @@ static inline void aead_request_set_callback(struct aead_request *req,
req->base.flags = flags;
}
/**
* aead_request_set_crypt - set data buffers
* @req: request handle
* @src: source scatter / gather list
* @dst: destination scatter / gather list
* @cryptlen: number of bytes to process from @src
* @iv: IV for the cipher operation which must comply with the IV size defined
* by crypto_aead_ivsize()
*
* Setting the source data and destination data scatter / gather lists.
*
* For encryption, the source is treated as the plaintext and the
* destination is the ciphertext. For a decryption operation, the use is
* reversed: the source is the ciphertext and the destination is the plaintext.
*
* IMPORTANT NOTE AEAD requires an authentication tag (MAC). For decryption,
* the caller must concatenate the ciphertext followed by the
* authentication tag and provide the entire data stream to the
* decryption operation (i.e. the data length used for the
* initialization of the scatterlist and the data length for the
* decryption operation is identical). For encryption, however,
* the authentication tag is created while encrypting the data.
* The destination buffer must hold sufficient space for the
* ciphertext and the authentication tag while the encryption
* invocation must only point to the plaintext data size. The
* following code snippet illustrates the memory usage
* buffer = kmalloc(ptbuflen + (enc ? authsize : 0));
* sg_init_one(&sg, buffer, ptbuflen + (enc ? authsize : 0));
* aead_request_set_crypt(req, &sg, &sg, ptbuflen, iv);
*/
static inline void aead_request_set_crypt(struct aead_request *req,
struct scatterlist *src,
struct scatterlist *dst,
@ -1306,6 +1548,15 @@ static inline void aead_request_set_crypt(struct aead_request *req,
req->iv = iv;
}
/**
* aead_request_set_assoc() - set the associated data scatter / gather list
* @req: request handle
* @assoc: associated data scatter / gather list
* @assoclen: number of bytes to process from @assoc
*
* For encryption, the memory is filled with the associated data. For
* decryption, the memory must point to the associated data.
*/
static inline void aead_request_set_assoc(struct aead_request *req,
struct scatterlist *assoc,
unsigned int assoclen)