1 /* 2 * AEAD: Authenticated Encryption with Associated Data 3 * 4 * Copyright (c) 2007-2015 Herbert Xu <herbert@gondor.apana.org.au> 5 * 6 * This program is free software; you can redistribute it and/or modify it 7 * under the terms of the GNU General Public License as published by the Free 8 * Software Foundation; either version 2 of the License, or (at your option) 9 * any later version. 10 * 11 */ 12 13 #ifndef _CRYPTO_AEAD_H 14 #define _CRYPTO_AEAD_H 15 16 #include <linux/crypto.h> 17 #include <linux/kernel.h> 18 #include <linux/slab.h> 19 20 /** 21 * DOC: Authenticated Encryption With Associated Data (AEAD) Cipher API 22 * 23 * The AEAD cipher API is used with the ciphers of type CRYPTO_ALG_TYPE_AEAD 24 * (listed as type "aead" in /proc/crypto) 25 * 26 * The most prominent examples for this type of encryption is GCM and CCM. 27 * However, the kernel supports other types of AEAD ciphers which are defined 28 * with the following cipher string: 29 * 30 * authenc(keyed message digest, block cipher) 31 * 32 * For example: authenc(hmac(sha256), cbc(aes)) 33 * 34 * The example code provided for the symmetric key cipher operation 35 * applies here as well. Naturally all *skcipher* symbols must be exchanged 36 * the *aead* pendants discussed in the following. In addition, for the AEAD 37 * operation, the aead_request_set_ad function must be used to set the 38 * pointer to the associated data memory location before performing the 39 * encryption or decryption operation. In case of an encryption, the associated 40 * data memory is filled during the encryption operation. For decryption, the 41 * associated data memory must contain data that is used to verify the integrity 42 * of the decrypted data. Another deviation from the asynchronous block cipher 43 * operation is that the caller should explicitly check for -EBADMSG of the 44 * crypto_aead_decrypt. That error indicates an authentication error, i.e. 45 * a breach in the integrity of the message. In essence, that -EBADMSG error 46 * code is the key bonus an AEAD cipher has over "standard" block chaining 47 * modes. 48 * 49 * Memory Structure: 50 * 51 * To support the needs of the most prominent user of AEAD ciphers, namely 52 * IPSEC, the AEAD ciphers have a special memory layout the caller must adhere 53 * to. 54 * 55 * The scatter list pointing to the input data must contain: 56 * 57 * * for RFC4106 ciphers, the concatenation of 58 * associated authentication data || IV || plaintext or ciphertext. Note, the 59 * same IV (buffer) is also set with the aead_request_set_crypt call. Note, 60 * the API call of aead_request_set_ad must provide the length of the AAD and 61 * the IV. The API call of aead_request_set_crypt only points to the size of 62 * the input plaintext or ciphertext. 63 * 64 * * for "normal" AEAD ciphers, the concatenation of 65 * associated authentication data || plaintext or ciphertext. 66 * 67 * It is important to note that if multiple scatter gather list entries form 68 * the input data mentioned above, the first entry must not point to a NULL 69 * buffer. If there is any potential where the AAD buffer can be NULL, the 70 * calling code must contain a precaution to ensure that this does not result 71 * in the first scatter gather list entry pointing to a NULL buffer. 72 */ 73 74 struct crypto_aead; 75 76 /** 77 * struct aead_request - AEAD request 78 * @base: Common attributes for async crypto requests 79 * @assoclen: Length in bytes of associated data for authentication 80 * @cryptlen: Length of data to be encrypted or decrypted 81 * @iv: Initialisation vector 82 * @src: Source data 83 * @dst: Destination data 84 * @__ctx: Start of private context data 85 */ 86 struct aead_request { 87 struct crypto_async_request base; 88 89 unsigned int assoclen; 90 unsigned int cryptlen; 91 92 u8 *iv; 93 94 struct scatterlist *src; 95 struct scatterlist *dst; 96 97 void *__ctx[] CRYPTO_MINALIGN_ATTR; 98 }; 99 100 /** 101 * struct aead_alg - AEAD cipher definition 102 * @maxauthsize: Set the maximum authentication tag size supported by the 103 * transformation. A transformation may support smaller tag sizes. 104 * As the authentication tag is a message digest to ensure the 105 * integrity of the encrypted data, a consumer typically wants the 106 * largest authentication tag possible as defined by this 107 * variable. 108 * @setauthsize: Set authentication size for the AEAD transformation. This 109 * function is used to specify the consumer requested size of the 110 * authentication tag to be either generated by the transformation 111 * during encryption or the size of the authentication tag to be 112 * supplied during the decryption operation. This function is also 113 * responsible for checking the authentication tag size for 114 * validity. 115 * @setkey: see struct skcipher_alg 116 * @encrypt: see struct skcipher_alg 117 * @decrypt: see struct skcipher_alg 118 * @geniv: 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 128 * in place. 129 * @exit: Deinitialize the cryptographic transformation object. This is a 130 * counterpart to @init, used to remove various changes set in 131 * @init. 132 * @base: Definition of a generic crypto cipher algorithm. 133 * 134 * All fields except @ivsize is mandatory and must be filled. 135 */ 136 struct aead_alg { 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); 144 145 const char *geniv; 146 147 unsigned int ivsize; 148 unsigned int maxauthsize; 149 unsigned int chunksize; 150 151 struct crypto_alg base; 152 }; 153 154 struct crypto_aead { 155 unsigned int authsize; 156 unsigned int reqsize; 157 158 struct crypto_tfm base; 159 }; 160 161 static inline struct crypto_aead *__crypto_aead_cast(struct crypto_tfm *tfm) 162 { 163 return container_of(tfm, struct crypto_aead, base); 164 } 165 166 /** 167 * crypto_alloc_aead() - allocate AEAD cipher handle 168 * @alg_name: is the cra_name / name or cra_driver_name / driver name of the 169 * AEAD cipher 170 * @type: specifies the type of the cipher 171 * @mask: specifies the mask for the cipher 172 * 173 * Allocate a cipher handle for an AEAD. The returned struct 174 * crypto_aead is the cipher handle that is required for any subsequent 175 * API invocation for that AEAD. 176 * 177 * Return: allocated cipher handle in case of success; IS_ERR() is true in case 178 * of an error, PTR_ERR() returns the error code. 179 */ 180 struct crypto_aead *crypto_alloc_aead(const char *alg_name, u32 type, u32 mask); 181 182 static inline struct crypto_tfm *crypto_aead_tfm(struct crypto_aead *tfm) 183 { 184 return &tfm->base; 185 } 186 187 /** 188 * crypto_free_aead() - zeroize and free aead handle 189 * @tfm: cipher handle to be freed 190 */ 191 static inline void crypto_free_aead(struct crypto_aead *tfm) 192 { 193 crypto_destroy_tfm(tfm, crypto_aead_tfm(tfm)); 194 } 195 196 static inline struct aead_alg *crypto_aead_alg(struct crypto_aead *tfm) 197 { 198 return container_of(crypto_aead_tfm(tfm)->__crt_alg, 199 struct aead_alg, base); 200 } 201 202 static inline unsigned int crypto_aead_alg_ivsize(struct aead_alg *alg) 203 { 204 return alg->ivsize; 205 } 206 207 /** 208 * crypto_aead_ivsize() - obtain IV size 209 * @tfm: cipher handle 210 * 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. 213 * 214 * Return: IV size in bytes 215 */ 216 static inline unsigned int crypto_aead_ivsize(struct crypto_aead *tfm) 217 { 218 return crypto_aead_alg_ivsize(crypto_aead_alg(tfm)); 219 } 220 221 /** 222 * crypto_aead_authsize() - obtain maximum authentication data size 223 * @tfm: cipher handle 224 * 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. 228 * 229 * The authentication data may also be known as "tag value". 230 * 231 * Return: authentication data size / tag size in bytes 232 */ 233 static inline unsigned int crypto_aead_authsize(struct crypto_aead *tfm) 234 { 235 return tfm->authsize; 236 } 237 238 /** 239 * crypto_aead_blocksize() - obtain block size of cipher 240 * @tfm: cipher handle 241 * 242 * The block size for the AEAD referenced with the cipher handle is returned. 243 * The caller may use that information to allocate appropriate memory for the 244 * data returned by the encryption or decryption operation 245 * 246 * Return: block size of cipher 247 */ 248 static inline unsigned int crypto_aead_blocksize(struct crypto_aead *tfm) 249 { 250 return crypto_tfm_alg_blocksize(crypto_aead_tfm(tfm)); 251 } 252 253 static inline unsigned int crypto_aead_alignmask(struct crypto_aead *tfm) 254 { 255 return crypto_tfm_alg_alignmask(crypto_aead_tfm(tfm)); 256 } 257 258 static inline u32 crypto_aead_get_flags(struct crypto_aead *tfm) 259 { 260 return crypto_tfm_get_flags(crypto_aead_tfm(tfm)); 261 } 262 263 static inline void crypto_aead_set_flags(struct crypto_aead *tfm, u32 flags) 264 { 265 crypto_tfm_set_flags(crypto_aead_tfm(tfm), flags); 266 } 267 268 static inline void crypto_aead_clear_flags(struct crypto_aead *tfm, u32 flags) 269 { 270 crypto_tfm_clear_flags(crypto_aead_tfm(tfm), flags); 271 } 272 273 /** 274 * crypto_aead_setkey() - set key for cipher 275 * @tfm: cipher handle 276 * @key: buffer holding the key 277 * @keylen: length of the key in bytes 278 * 279 * The caller provided key is set for the AEAD referenced by the cipher 280 * handle. 281 * 282 * Note, the key length determines the cipher type. Many block ciphers implement 283 * different cipher modes depending on the key size, such as AES-128 vs AES-192 284 * vs. AES-256. When providing a 16 byte key for an AES cipher handle, AES-128 285 * is performed. 286 * 287 * Return: 0 if the setting of the key was successful; < 0 if an error occurred 288 */ 289 int crypto_aead_setkey(struct crypto_aead *tfm, 290 const u8 *key, unsigned int keylen); 291 292 /** 293 * crypto_aead_setauthsize() - set authentication data size 294 * @tfm: cipher handle 295 * @authsize: size of the authentication data / tag in bytes 296 * 297 * Set the authentication data size / tag size. AEAD requires an authentication 298 * tag (or MAC) in addition to the associated data. 299 * 300 * Return: 0 if the setting of the key was successful; < 0 if an error occurred 301 */ 302 int crypto_aead_setauthsize(struct crypto_aead *tfm, unsigned int authsize); 303 304 static inline struct crypto_aead *crypto_aead_reqtfm(struct aead_request *req) 305 { 306 return __crypto_aead_cast(req->base.tfm); 307 } 308 309 /** 310 * crypto_aead_encrypt() - encrypt plaintext 311 * @req: reference to the aead_request handle that holds all information 312 * needed to perform the cipher operation 313 * 314 * Encrypt plaintext data using the aead_request handle. That data structure 315 * and how it is filled with data is discussed with the aead_request_* 316 * functions. 317 * 318 * IMPORTANT NOTE The encryption operation creates the authentication data / 319 * tag. That data is concatenated with the created ciphertext. 320 * The ciphertext memory size is therefore the given number of 321 * block cipher blocks + the size defined by the 322 * crypto_aead_setauthsize invocation. The caller must ensure 323 * that sufficient memory is available for the ciphertext and 324 * the authentication tag. 325 * 326 * Return: 0 if the cipher operation was successful; < 0 if an error occurred 327 */ 328 static inline int crypto_aead_encrypt(struct aead_request *req) 329 { 330 struct crypto_aead *aead = crypto_aead_reqtfm(req); 331 struct crypto_alg *alg = aead->base.__crt_alg; 332 unsigned int cryptlen = req->cryptlen; 333 int ret; 334 335 crypto_stats_get(alg); 336 if (crypto_aead_get_flags(aead) & CRYPTO_TFM_NEED_KEY) 337 ret = -ENOKEY; 338 else 339 ret = crypto_aead_alg(aead)->encrypt(req); 340 crypto_stats_aead_encrypt(cryptlen, alg, ret); 341 return ret; 342 } 343 344 /** 345 * crypto_aead_decrypt() - decrypt ciphertext 346 * @req: reference to the ablkcipher_request handle that holds all information 347 * needed to perform the cipher operation 348 * 349 * Decrypt ciphertext data using the aead_request handle. That data structure 350 * and how it is filled with data is discussed with the aead_request_* 351 * functions. 352 * 353 * IMPORTANT NOTE The caller must concatenate the ciphertext followed by the 354 * authentication data / tag. That authentication data / tag 355 * must have the size defined by the crypto_aead_setauthsize 356 * invocation. 357 * 358 * 359 * Return: 0 if the cipher operation was successful; -EBADMSG: The AEAD 360 * cipher operation performs the authentication of the data during the 361 * decryption operation. Therefore, the function returns this error if 362 * the authentication of the ciphertext was unsuccessful (i.e. the 363 * integrity of the ciphertext or the associated data was violated); 364 * < 0 if an error occurred. 365 */ 366 static inline int crypto_aead_decrypt(struct aead_request *req) 367 { 368 struct crypto_aead *aead = crypto_aead_reqtfm(req); 369 struct crypto_alg *alg = aead->base.__crt_alg; 370 unsigned int cryptlen = req->cryptlen; 371 int ret; 372 373 crypto_stats_get(alg); 374 if (crypto_aead_get_flags(aead) & CRYPTO_TFM_NEED_KEY) 375 ret = -ENOKEY; 376 else if (req->cryptlen < crypto_aead_authsize(aead)) 377 ret = -EINVAL; 378 else 379 ret = crypto_aead_alg(aead)->decrypt(req); 380 crypto_stats_aead_decrypt(cryptlen, alg, ret); 381 return ret; 382 } 383 384 /** 385 * DOC: Asynchronous AEAD Request Handle 386 * 387 * The aead_request data structure contains all pointers to data required for 388 * the AEAD cipher operation. This includes the cipher handle (which can be 389 * used by multiple aead_request instances), pointer to plaintext and 390 * ciphertext, asynchronous callback function, etc. It acts as a handle to the 391 * aead_request_* API calls in a similar way as AEAD handle to the 392 * crypto_aead_* API calls. 393 */ 394 395 /** 396 * crypto_aead_reqsize() - obtain size of the request data structure 397 * @tfm: cipher handle 398 * 399 * Return: number of bytes 400 */ 401 static inline unsigned int crypto_aead_reqsize(struct crypto_aead *tfm) 402 { 403 return tfm->reqsize; 404 } 405 406 /** 407 * aead_request_set_tfm() - update cipher handle reference in request 408 * @req: request handle to be modified 409 * @tfm: cipher handle that shall be added to the request handle 410 * 411 * Allow the caller to replace the existing aead handle in the request 412 * data structure with a different one. 413 */ 414 static inline void aead_request_set_tfm(struct aead_request *req, 415 struct crypto_aead *tfm) 416 { 417 req->base.tfm = crypto_aead_tfm(tfm); 418 } 419 420 /** 421 * aead_request_alloc() - allocate request data structure 422 * @tfm: cipher handle to be registered with the request 423 * @gfp: memory allocation flag that is handed to kmalloc by the API call. 424 * 425 * Allocate the request data structure that must be used with the AEAD 426 * encrypt and decrypt API calls. During the allocation, the provided aead 427 * handle is registered in the request data structure. 428 * 429 * Return: allocated request handle in case of success, or NULL if out of memory 430 */ 431 static inline struct aead_request *aead_request_alloc(struct crypto_aead *tfm, 432 gfp_t gfp) 433 { 434 struct aead_request *req; 435 436 req = kmalloc(sizeof(*req) + crypto_aead_reqsize(tfm), gfp); 437 438 if (likely(req)) 439 aead_request_set_tfm(req, tfm); 440 441 return req; 442 } 443 444 /** 445 * aead_request_free() - zeroize and free request data structure 446 * @req: request data structure cipher handle to be freed 447 */ 448 static inline void aead_request_free(struct aead_request *req) 449 { 450 kzfree(req); 451 } 452 453 /** 454 * aead_request_set_callback() - set asynchronous callback function 455 * @req: request handle 456 * @flags: specify zero or an ORing of the flags 457 * CRYPTO_TFM_REQ_MAY_BACKLOG the request queue may back log and 458 * increase the wait queue beyond the initial maximum size; 459 * CRYPTO_TFM_REQ_MAY_SLEEP the request processing may sleep 460 * @compl: callback function pointer to be registered with the request handle 461 * @data: The data pointer refers to memory that is not used by the kernel 462 * crypto API, but provided to the callback function for it to use. Here, 463 * the caller can provide a reference to memory the callback function can 464 * operate on. As the callback function is invoked asynchronously to the 465 * related functionality, it may need to access data structures of the 466 * related functionality which can be referenced using this pointer. The 467 * callback function can access the memory via the "data" field in the 468 * crypto_async_request data structure provided to the callback function. 469 * 470 * Setting the callback function that is triggered once the cipher operation 471 * completes 472 * 473 * The callback function is registered with the aead_request handle and 474 * must comply with the following template:: 475 * 476 * void callback_function(struct crypto_async_request *req, int error) 477 */ 478 static inline void aead_request_set_callback(struct aead_request *req, 479 u32 flags, 480 crypto_completion_t compl, 481 void *data) 482 { 483 req->base.complete = compl; 484 req->base.data = data; 485 req->base.flags = flags; 486 } 487 488 /** 489 * aead_request_set_crypt - set data buffers 490 * @req: request handle 491 * @src: source scatter / gather list 492 * @dst: destination scatter / gather list 493 * @cryptlen: number of bytes to process from @src 494 * @iv: IV for the cipher operation which must comply with the IV size defined 495 * by crypto_aead_ivsize() 496 * 497 * Setting the source data and destination data scatter / gather lists which 498 * hold the associated data concatenated with the plaintext or ciphertext. See 499 * below for the authentication tag. 500 * 501 * For encryption, the source is treated as the plaintext and the 502 * destination is the ciphertext. For a decryption operation, the use is 503 * reversed - the source is the ciphertext and the destination is the plaintext. 504 * 505 * The memory structure for cipher operation has the following structure: 506 * 507 * - AEAD encryption input: assoc data || plaintext 508 * - AEAD encryption output: assoc data || cipherntext || auth tag 509 * - AEAD decryption input: assoc data || ciphertext || auth tag 510 * - AEAD decryption output: assoc data || plaintext 511 * 512 * Albeit the kernel requires the presence of the AAD buffer, however, 513 * the kernel does not fill the AAD buffer in the output case. If the 514 * caller wants to have that data buffer filled, the caller must either 515 * use an in-place cipher operation (i.e. same memory location for 516 * input/output memory location). 517 */ 518 static inline void aead_request_set_crypt(struct aead_request *req, 519 struct scatterlist *src, 520 struct scatterlist *dst, 521 unsigned int cryptlen, u8 *iv) 522 { 523 req->src = src; 524 req->dst = dst; 525 req->cryptlen = cryptlen; 526 req->iv = iv; 527 } 528 529 /** 530 * aead_request_set_ad - set associated data information 531 * @req: request handle 532 * @assoclen: number of bytes in associated data 533 * 534 * Setting the AD information. This function sets the length of 535 * the associated data. 536 */ 537 static inline void aead_request_set_ad(struct aead_request *req, 538 unsigned int assoclen) 539 { 540 req->assoclen = assoclen; 541 } 542 543 #endif /* _CRYPTO_AEAD_H */ 544