1 /* SPDX-License-Identifier: GPL-2.0-or-later */
3 * AEAD: Authenticated Encryption with Associated Data
5 * Copyright (c) 2007-2015 Herbert Xu <herbert@gondor.apana.org.au>
11 #include <linux/crypto.h>
12 #include <linux/kernel.h>
13 #include <linux/slab.h>
16 * DOC: Authenticated Encryption With Associated Data (AEAD) Cipher API
18 * The AEAD cipher API is used with the ciphers of type CRYPTO_ALG_TYPE_AEAD
19 * (listed as type "aead" in /proc/crypto)
21 * The most prominent examples for this type of encryption is GCM and CCM.
22 * However, the kernel supports other types of AEAD ciphers which are defined
23 * with the following cipher string:
25 * authenc(keyed message digest, block cipher)
27 * For example: authenc(hmac(sha256), cbc(aes))
29 * The example code provided for the symmetric key cipher operation
30 * applies here as well. Naturally all *skcipher* symbols must be exchanged
31 * the *aead* pendants discussed in the following. In addition, for the AEAD
32 * operation, the aead_request_set_ad function must be used to set the
33 * pointer to the associated data memory location before performing the
34 * encryption or decryption operation. In case of an encryption, the associated
35 * data memory is filled during the encryption operation. For decryption, the
36 * associated data memory must contain data that is used to verify the integrity
37 * of the decrypted data. Another deviation from the asynchronous block cipher
38 * operation is that the caller should explicitly check for -EBADMSG of the
39 * crypto_aead_decrypt. That error indicates an authentication error, i.e.
40 * a breach in the integrity of the message. In essence, that -EBADMSG error
41 * code is the key bonus an AEAD cipher has over "standard" block chaining
46 * The source scatterlist must contain the concatenation of
47 * associated data || plaintext or ciphertext.
49 * The destination scatterlist has the same layout, except that the plaintext
50 * (resp. ciphertext) will grow (resp. shrink) by the authentication tag size
51 * during encryption (resp. decryption).
53 * In-place encryption/decryption is enabled by using the same scatterlist
54 * pointer for both the source and destination.
56 * Even in the out-of-place case, space must be reserved in the destination for
57 * the associated data, even though it won't be written to. This makes the
58 * in-place and out-of-place cases more consistent. It is permissible for the
59 * "destination" associated data to alias the "source" associated data.
61 * As with the other scatterlist crypto APIs, zero-length scatterlist elements
62 * are not allowed in the used part of the scatterlist. Thus, if there is no
63 * associated data, the first element must point to the plaintext/ciphertext.
65 * To meet the needs of IPsec, a special quirk applies to rfc4106, rfc4309,
66 * rfc4543, and rfc7539esp ciphers. For these ciphers, the final 'ivsize' bytes
67 * of the associated data buffer must contain a second copy of the IV. This is
68 * in addition to the copy passed to aead_request_set_crypt(). These two IV
69 * copies must not differ; different implementations of the same algorithm may
70 * behave differently in that case. Note that the algorithm might not actually
71 * treat the IV as associated data; nevertheless the length passed to
72 * aead_request_set_ad() must include it.
78 * struct aead_request - AEAD request
79 * @base: Common attributes for async crypto requests
80 * @assoclen: Length in bytes of associated data for authentication
81 * @cryptlen: Length of data to be encrypted or decrypted
82 * @iv: Initialisation vector
84 * @dst: Destination data
85 * @__ctx: Start of private context data
88 struct crypto_async_request base;
90 unsigned int assoclen;
91 unsigned int cryptlen;
95 struct scatterlist *src;
96 struct scatterlist *dst;
98 void *__ctx[] CRYPTO_MINALIGN_ATTR;
102 * struct aead_alg - AEAD cipher definition
103 * @maxauthsize: Set the maximum authentication tag size supported by the
104 * transformation. A transformation may support smaller tag sizes.
105 * As the authentication tag is a message digest to ensure the
106 * integrity of the encrypted data, a consumer typically wants the
107 * largest authentication tag possible as defined by this
109 * @setauthsize: Set authentication size for the AEAD transformation. This
110 * function is used to specify the consumer requested size of the
111 * authentication tag to be either generated by the transformation
112 * during encryption or the size of the authentication tag to be
113 * supplied during the decryption operation. This function is also
114 * responsible for checking the authentication tag size for
116 * @setkey: see struct skcipher_alg
117 * @encrypt: see struct skcipher_alg
118 * @decrypt: see struct skcipher_alg
119 * @ivsize: see struct skcipher_alg
120 * @chunksize: see struct skcipher_alg
121 * @init: Initialize the cryptographic transformation object. This function
122 * is used to initialize the cryptographic transformation object.
123 * This function is called only once at the instantiation time, right
124 * after the transformation context was allocated. In case the
125 * cryptographic hardware has some special requirements which need to
126 * be handled by software, this function shall check for the precise
127 * requirement of the transformation and put any software fallbacks
129 * @exit: Deinitialize the cryptographic transformation object. This is a
130 * counterpart to @init, used to remove various changes set in
132 * @base: Definition of a generic crypto cipher algorithm.
134 * All fields except @ivsize is mandatory and must be filled.
137 int (*setkey)(struct crypto_aead *tfm, const u8 *key,
138 unsigned int keylen);
139 int (*setauthsize)(struct crypto_aead *tfm, unsigned int authsize);
140 int (*encrypt)(struct aead_request *req);
141 int (*decrypt)(struct aead_request *req);
142 int (*init)(struct crypto_aead *tfm);
143 void (*exit)(struct crypto_aead *tfm);
146 unsigned int maxauthsize;
147 unsigned int chunksize;
149 struct crypto_alg base;
153 unsigned int authsize;
154 unsigned int reqsize;
156 struct crypto_tfm base;
159 static inline struct crypto_aead *__crypto_aead_cast(struct crypto_tfm *tfm)
161 return container_of(tfm, struct crypto_aead, base);
165 * crypto_alloc_aead() - allocate AEAD cipher handle
166 * @alg_name: is the cra_name / name or cra_driver_name / driver name of the
168 * @type: specifies the type of the cipher
169 * @mask: specifies the mask for the cipher
171 * Allocate a cipher handle for an AEAD. The returned struct
172 * crypto_aead is the cipher handle that is required for any subsequent
173 * API invocation for that AEAD.
175 * Return: allocated cipher handle in case of success; IS_ERR() is true in case
176 * of an error, PTR_ERR() returns the error code.
178 struct crypto_aead *crypto_alloc_aead(const char *alg_name, u32 type, u32 mask);
180 static inline struct crypto_tfm *crypto_aead_tfm(struct crypto_aead *tfm)
186 * crypto_free_aead() - zeroize and free aead handle
187 * @tfm: cipher handle to be freed
189 * If @tfm is a NULL or error pointer, this function does nothing.
191 static inline void crypto_free_aead(struct crypto_aead *tfm)
193 crypto_destroy_tfm(tfm, crypto_aead_tfm(tfm));
196 static inline struct aead_alg *crypto_aead_alg(struct crypto_aead *tfm)
198 return container_of(crypto_aead_tfm(tfm)->__crt_alg,
199 struct aead_alg, base);
202 static inline unsigned int crypto_aead_alg_ivsize(struct aead_alg *alg)
208 * crypto_aead_ivsize() - obtain IV size
209 * @tfm: cipher handle
211 * The size of the IV for the aead referenced by the cipher handle is
212 * returned. This IV size may be zero if the cipher does not need an IV.
214 * Return: IV size in bytes
216 static inline unsigned int crypto_aead_ivsize(struct crypto_aead *tfm)
218 return crypto_aead_alg_ivsize(crypto_aead_alg(tfm));
222 * crypto_aead_authsize() - obtain maximum authentication data size
223 * @tfm: cipher handle
225 * The maximum size of the authentication data for the AEAD cipher referenced
226 * by the AEAD cipher handle is returned. The authentication data size may be
227 * zero if the cipher implements a hard-coded maximum.
229 * The authentication data may also be known as "tag value".
231 * Return: authentication data size / tag size in bytes
233 static inline unsigned int crypto_aead_authsize(struct crypto_aead *tfm)
235 return tfm->authsize;
238 static inline unsigned int crypto_aead_alg_maxauthsize(struct aead_alg *alg)
240 return alg->maxauthsize;
243 static inline unsigned int crypto_aead_maxauthsize(struct crypto_aead *aead)
245 return crypto_aead_alg_maxauthsize(crypto_aead_alg(aead));
249 * crypto_aead_blocksize() - obtain block size of cipher
250 * @tfm: cipher handle
252 * The block size for the AEAD referenced with the cipher handle is returned.
253 * The caller may use that information to allocate appropriate memory for the
254 * data returned by the encryption or decryption operation
256 * Return: block size of cipher
258 static inline unsigned int crypto_aead_blocksize(struct crypto_aead *tfm)
260 return crypto_tfm_alg_blocksize(crypto_aead_tfm(tfm));
263 static inline unsigned int crypto_aead_alignmask(struct crypto_aead *tfm)
265 return crypto_tfm_alg_alignmask(crypto_aead_tfm(tfm));
268 static inline u32 crypto_aead_get_flags(struct crypto_aead *tfm)
270 return crypto_tfm_get_flags(crypto_aead_tfm(tfm));
273 static inline void crypto_aead_set_flags(struct crypto_aead *tfm, u32 flags)
275 crypto_tfm_set_flags(crypto_aead_tfm(tfm), flags);
278 static inline void crypto_aead_clear_flags(struct crypto_aead *tfm, u32 flags)
280 crypto_tfm_clear_flags(crypto_aead_tfm(tfm), flags);
284 * crypto_aead_setkey() - set key for cipher
285 * @tfm: cipher handle
286 * @key: buffer holding the key
287 * @keylen: length of the key in bytes
289 * The caller provided key is set for the AEAD referenced by the cipher
292 * Note, the key length determines the cipher type. Many block ciphers implement
293 * different cipher modes depending on the key size, such as AES-128 vs AES-192
294 * vs. AES-256. When providing a 16 byte key for an AES cipher handle, AES-128
297 * Return: 0 if the setting of the key was successful; < 0 if an error occurred
299 int crypto_aead_setkey(struct crypto_aead *tfm,
300 const u8 *key, unsigned int keylen);
303 * crypto_aead_setauthsize() - set authentication data size
304 * @tfm: cipher handle
305 * @authsize: size of the authentication data / tag in bytes
307 * Set the authentication data size / tag size. AEAD requires an authentication
308 * tag (or MAC) in addition to the associated data.
310 * Return: 0 if the setting of the key was successful; < 0 if an error occurred
312 int crypto_aead_setauthsize(struct crypto_aead *tfm, unsigned int authsize);
314 static inline struct crypto_aead *crypto_aead_reqtfm(struct aead_request *req)
316 return __crypto_aead_cast(req->base.tfm);
320 * crypto_aead_encrypt() - encrypt plaintext
321 * @req: reference to the aead_request handle that holds all information
322 * needed to perform the cipher operation
324 * Encrypt plaintext data using the aead_request handle. That data structure
325 * and how it is filled with data is discussed with the aead_request_*
328 * IMPORTANT NOTE The encryption operation creates the authentication data /
329 * tag. That data is concatenated with the created ciphertext.
330 * The ciphertext memory size is therefore the given number of
331 * block cipher blocks + the size defined by the
332 * crypto_aead_setauthsize invocation. The caller must ensure
333 * that sufficient memory is available for the ciphertext and
334 * the authentication tag.
336 * Return: 0 if the cipher operation was successful; < 0 if an error occurred
338 int crypto_aead_encrypt(struct aead_request *req);
341 * crypto_aead_decrypt() - decrypt ciphertext
342 * @req: reference to the aead_request handle that holds all information
343 * needed to perform the cipher operation
345 * Decrypt ciphertext data using the aead_request handle. That data structure
346 * and how it is filled with data is discussed with the aead_request_*
349 * IMPORTANT NOTE The caller must concatenate the ciphertext followed by the
350 * authentication data / tag. That authentication data / tag
351 * must have the size defined by the crypto_aead_setauthsize
355 * Return: 0 if the cipher operation was successful; -EBADMSG: The AEAD
356 * cipher operation performs the authentication of the data during the
357 * decryption operation. Therefore, the function returns this error if
358 * the authentication of the ciphertext was unsuccessful (i.e. the
359 * integrity of the ciphertext or the associated data was violated);
360 * < 0 if an error occurred.
362 int crypto_aead_decrypt(struct aead_request *req);
365 * DOC: Asynchronous AEAD Request Handle
367 * The aead_request data structure contains all pointers to data required for
368 * the AEAD cipher operation. This includes the cipher handle (which can be
369 * used by multiple aead_request instances), pointer to plaintext and
370 * ciphertext, asynchronous callback function, etc. It acts as a handle to the
371 * aead_request_* API calls in a similar way as AEAD handle to the
372 * crypto_aead_* API calls.
376 * crypto_aead_reqsize() - obtain size of the request data structure
377 * @tfm: cipher handle
379 * Return: number of bytes
381 static inline unsigned int crypto_aead_reqsize(struct crypto_aead *tfm)
387 * aead_request_set_tfm() - update cipher handle reference in request
388 * @req: request handle to be modified
389 * @tfm: cipher handle that shall be added to the request handle
391 * Allow the caller to replace the existing aead handle in the request
392 * data structure with a different one.
394 static inline void aead_request_set_tfm(struct aead_request *req,
395 struct crypto_aead *tfm)
397 req->base.tfm = crypto_aead_tfm(tfm);
401 * aead_request_alloc() - allocate request data structure
402 * @tfm: cipher handle to be registered with the request
403 * @gfp: memory allocation flag that is handed to kmalloc by the API call.
405 * Allocate the request data structure that must be used with the AEAD
406 * encrypt and decrypt API calls. During the allocation, the provided aead
407 * handle is registered in the request data structure.
409 * Return: allocated request handle in case of success, or NULL if out of memory
411 static inline struct aead_request *aead_request_alloc(struct crypto_aead *tfm,
414 struct aead_request *req;
416 req = kmalloc(sizeof(*req) + crypto_aead_reqsize(tfm), gfp);
419 aead_request_set_tfm(req, tfm);
425 * aead_request_free() - zeroize and free request data structure
426 * @req: request data structure cipher handle to be freed
428 static inline void aead_request_free(struct aead_request *req)
430 kfree_sensitive(req);
434 * aead_request_set_callback() - set asynchronous callback function
435 * @req: request handle
436 * @flags: specify zero or an ORing of the flags
437 * CRYPTO_TFM_REQ_MAY_BACKLOG the request queue may back log and
438 * increase the wait queue beyond the initial maximum size;
439 * CRYPTO_TFM_REQ_MAY_SLEEP the request processing may sleep
440 * @compl: callback function pointer to be registered with the request handle
441 * @data: The data pointer refers to memory that is not used by the kernel
442 * crypto API, but provided to the callback function for it to use. Here,
443 * the caller can provide a reference to memory the callback function can
444 * operate on. As the callback function is invoked asynchronously to the
445 * related functionality, it may need to access data structures of the
446 * related functionality which can be referenced using this pointer. The
447 * callback function can access the memory via the "data" field in the
448 * crypto_async_request data structure provided to the callback function.
450 * Setting the callback function that is triggered once the cipher operation
453 * The callback function is registered with the aead_request handle and
454 * must comply with the following template::
456 * void callback_function(struct crypto_async_request *req, int error)
458 static inline void aead_request_set_callback(struct aead_request *req,
460 crypto_completion_t compl,
463 req->base.complete = compl;
464 req->base.data = data;
465 req->base.flags = flags;
469 * aead_request_set_crypt - set data buffers
470 * @req: request handle
471 * @src: source scatter / gather list
472 * @dst: destination scatter / gather list
473 * @cryptlen: number of bytes to process from @src
474 * @iv: IV for the cipher operation which must comply with the IV size defined
475 * by crypto_aead_ivsize()
477 * Setting the source data and destination data scatter / gather lists which
478 * hold the associated data concatenated with the plaintext or ciphertext. See
479 * below for the authentication tag.
481 * For encryption, the source is treated as the plaintext and the
482 * destination is the ciphertext. For a decryption operation, the use is
483 * reversed - the source is the ciphertext and the destination is the plaintext.
485 * The memory structure for cipher operation has the following structure:
487 * - AEAD encryption input: assoc data || plaintext
488 * - AEAD encryption output: assoc data || cipherntext || auth tag
489 * - AEAD decryption input: assoc data || ciphertext || auth tag
490 * - AEAD decryption output: assoc data || plaintext
492 * Albeit the kernel requires the presence of the AAD buffer, however,
493 * the kernel does not fill the AAD buffer in the output case. If the
494 * caller wants to have that data buffer filled, the caller must either
495 * use an in-place cipher operation (i.e. same memory location for
496 * input/output memory location).
498 static inline void aead_request_set_crypt(struct aead_request *req,
499 struct scatterlist *src,
500 struct scatterlist *dst,
501 unsigned int cryptlen, u8 *iv)
505 req->cryptlen = cryptlen;
510 * aead_request_set_ad - set associated data information
511 * @req: request handle
512 * @assoclen: number of bytes in associated data
514 * Setting the AD information. This function sets the length of
515 * the associated data.
517 static inline void aead_request_set_ad(struct aead_request *req,
518 unsigned int assoclen)
520 req->assoclen = assoclen;
523 #endif /* _CRYPTO_AEAD_H */