From: Stephan Mueller Subject: [PATCH v2 08/11] crypto: Documentation - AEAD API documentation Date: Sun, 02 Nov 2014 21:40:07 +0100 Message-ID: <1883672.3CPmHykk4r@tachyon.chronox.de> References: <6375771.bx7QqLJLuR@tachyon.chronox.de> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7Bit Cc: "David S. Miller" , Marek Vasut , Jason Cooper , Grant Likely , Geert Uytterhoeven , Linux Kernel Developers List , linux-crypto@vger.kernel.org To: Herbert Xu Return-path: In-Reply-To: <6375771.bx7QqLJLuR@tachyon.chronox.de> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-crypto.vger.kernel.org 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 CC: Marek Vasut --- include/linux/crypto.h | 259 +++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 259 insertions(+) diff --git a/include/linux/crypto.h b/include/linux/crypto.h index 67acda4..12c8a7a 100644 --- a/include/linux/crypto.h +++ b/include/linux/crypto.h @@ -1194,11 +1194,53 @@ static inline void ablkcipher_request_set_crypt( req->info = iv; } +/** + * Authenticated Encryption with Associated Data (AEAD) cipher API to use 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(, ) + * + * 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; } +/** + * 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. + * + * @alg_name is the cra_name / name or cra_driver_name / driver name of the + * AEAD cipher + * @type specifies the type of the cipher (see Documentation/crypto/) + * @mask specifies the mask for the cipher (see Documentation/crypto/) + * + * return value: + * 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) @@ -1206,6 +1248,11 @@ static inline struct crypto_tfm *crypto_aead_tfm(struct crypto_aead *tfm) return &tfm->base; } +/** + * The referenced aead handle is zeroized and subsequently freed. + * + * @tfm cipher handle to be freed + */ static inline void crypto_free_aead(struct crypto_aead *tfm) { crypto_free_tfm(crypto_aead_tfm(tfm)); @@ -1216,16 +1263,47 @@ static inline struct aead_tfm *crypto_aead_crt(struct crypto_aead *tfm) return &crypto_aead_tfm(tfm)->crt_aead; } +/** + * 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. + * + * @tfm cipher handle + * + * return value: + * IV size in bytes + */ static inline unsigned int crypto_aead_ivsize(struct crypto_aead *tfm) { return crypto_aead_crt(tfm)->ivsize; } +/** + * 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". + * + * @tfm cipher handle + * + * return value: + * authentication data size / tag size in bytes + */ static inline unsigned int crypto_aead_authsize(struct crypto_aead *tfm) { return crypto_aead_crt(tfm)->authsize; } +/** + * 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 + * + * @tfm cipher handle + * + * return value: + * block size of cipher + */ static inline unsigned int crypto_aead_blocksize(struct crypto_aead *tfm) { return crypto_tfm_alg_blocksize(crypto_aead_tfm(tfm)); @@ -1251,6 +1329,23 @@ static inline void crypto_aead_clear_flags(struct crypto_aead *tfm, u32 flags) crypto_tfm_clear_flags(crypto_aead_tfm(tfm), flags); } +/** + * 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. + * + * @tfm cipher handle + * @key buffer holding the key + * @keylen length of the key in bytes + * + * return value: + * 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) { @@ -1259,6 +1354,17 @@ static inline int crypto_aead_setkey(struct crypto_aead *tfm, const u8 *key, return crt->setkey(crt->base, key, keylen); } +/** + * Set the authentication data size / tag size. AEAD requires an authentication + * tag (or MAC) in addition to the associated data. + * + * @tfm cipher handle + * @authsize size of the authentication data / tag in bytes + * + * return value: + * 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) @@ -1266,27 +1372,105 @@ static inline struct crypto_aead *crypto_aead_reqtfm(struct aead_request *req) return __crypto_aead_cast(req->base.tfm); } +/** + * 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. + * + * @req reference to the aead_request handle that holds all information + * needed to perform the cipher operation + * + * return value: + * 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); } +/** + * 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. + * + * @req reference to the ablkcipher_request handle that holds all information + * needed to perform the cipher operation + * + * return value: + * 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); } +/** + * 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. + */ + +/** + * Return the size of the aead_request data structure to the caller. + * + * @tfm cipher handle + * + * return value: + * number of bytes + */ static inline unsigned int crypto_aead_reqsize(struct crypto_aead *tfm) { return crypto_aead_crt(tfm)->reqsize; } +/** + * Allow the caller to replace the existing aead handle in the request + * data structure with a different one. + * + * @req request handle to be modified + * @tfm cipher handle that shall be added to the request handle + */ 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); } +/** + * 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. + * + * @tfm cipher handle to be registered with the request + * @gfp memory allocation flag that is handed to kmalloc by the API call. + * + * return value: + * 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) { @@ -1300,11 +1484,40 @@ static inline struct aead_request *aead_request_alloc(struct crypto_aead *tfm, return req; } +/** + * The referenced request data structure is zeroized and subsequently freed. + * + * @req request data structure cipher handle to be freed + */ static inline void aead_request_free(struct aead_request *req) { kzfree(req); } +/** + * 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) + * + * @req request handle + * @flags specify zero or an ORing of the following 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. + */ static inline void aead_request_set_callback(struct aead_request *req, u32 flags, crypto_completion_t compl, @@ -1315,6 +1528,42 @@ static inline void aead_request_set_callback(struct aead_request *req, req->base.flags = flags; } +/** + * 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: + * + * //sg is the pointer to plaintext and will hold the cipher text + * //authsize is the size of the authentication tag + * //enc is 1 for encryption, 0 for decryption + * //ptbuf is the buffer with the plaintext + * //ptbuflen is the plaintext buffer size + * buffer = kmalloc(ptbuflen + (enc ? authsize : 0)); + * memcpy(buffer, ptbuf, ptbuflen); + * sg_init_one(&sg, buffer, ptbuflen + (enc ? authsize : 0)); + * aead_request_set_crypt(req, &sg, &sg, ptbuflen, iv); + * + * @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 + */ static inline void aead_request_set_crypt(struct aead_request *req, struct scatterlist *src, struct scatterlist *dst, @@ -1326,6 +1575,16 @@ static inline void aead_request_set_crypt(struct aead_request *req, req->iv = iv; } +/** + * Setting the associated data scatter / gather list. + * + * For encryption, the memory is filled with the associated data. For + * decryption, the memory must point to the associated data. + * + * @req request handle + * @assoc associated data scatter / gather list + * @assoclen number of bytes to process from @assoc + */ static inline void aead_request_set_assoc(struct aead_request *req, struct scatterlist *assoc, unsigned int assoclen) -- 2.1.0