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 asynchronous block cipher operation 35 * applies here as well. Naturally all *ablkcipher* symbols must be exchanged 36 * the *aead* pendants discussed in the following. In addition, for the AEAD 37 * operation, the aead_request_set_assoc 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 ablkcipher_alg 116 * @encrypt: see struct ablkcipher_alg 117 * @decrypt: see struct ablkcipher_alg 118 * @geniv: see struct ablkcipher_alg 119 * @ivsize: see struct ablkcipher_alg 120 * @init: Initialize the cryptographic transformation object. This function 121 * is used to initialize the cryptographic transformation object. 122 * This function is called only once at the instantiation time, right 123 * after the transformation context was allocated. In case the 124 * cryptographic hardware has some special requirements which need to 125 * be handled by software, this function shall check for the precise 126 * requirement of the transformation and put any software fallbacks 127 * in place. 128 * @exit: Deinitialize the cryptographic transformation object. This is a 129 * counterpart to @init, used to remove various changes set in 130 * @init. 131 * 132 * All fields except @ivsize is mandatory and must be filled. 133 */ 134 struct aead_alg { 135 int (*setkey)(struct crypto_aead *tfm, const u8 *key, 136 unsigned int keylen); 137 int (*setauthsize)(struct crypto_aead *tfm, unsigned int authsize); 138 int (*encrypt)(struct aead_request *req); 139 int (*decrypt)(struct aead_request *req); 140 int (*init)(struct crypto_aead *tfm); 141 void (*exit)(struct crypto_aead *tfm); 142 143 const char *geniv; 144 145 unsigned int ivsize; 146 unsigned int maxauthsize; 147 148 struct crypto_alg base; 149 }; 150 151 struct crypto_aead { 152 unsigned int authsize; 153 unsigned int reqsize; 154 155 struct crypto_tfm base; 156 }; 157 158 static inline struct crypto_aead *__crypto_aead_cast(struct crypto_tfm *tfm) 159 { 160 return container_of(tfm, struct crypto_aead, base); 161 } 162 163 /** 164 * crypto_alloc_aead() - allocate AEAD cipher handle 165 * @alg_name: is the cra_name / name or cra_driver_name / driver name of the 166 * AEAD cipher 167 * @type: specifies the type of the cipher 168 * @mask: specifies the mask for the cipher 169 * 170 * Allocate a cipher handle for an AEAD. The returned struct 171 * crypto_aead is the cipher handle that is required for any subsequent 172 * API invocation for that AEAD. 173 * 174 * Return: allocated cipher handle in case of success; IS_ERR() is true in case 175 * of an error, PTR_ERR() returns the error code. 176 */ 177 struct crypto_aead *crypto_alloc_aead(const char *alg_name, u32 type, u32 mask); 178 179 static inline struct crypto_tfm *crypto_aead_tfm(struct crypto_aead *tfm) 180 { 181 return &tfm->base; 182 } 183 184 /** 185 * crypto_free_aead() - zeroize and free aead handle 186 * @tfm: cipher handle to be freed 187 */ 188 static inline void crypto_free_aead(struct crypto_aead *tfm) 189 { 190 crypto_destroy_tfm(tfm, crypto_aead_tfm(tfm)); 191 } 192 193 static inline struct aead_alg *crypto_aead_alg(struct crypto_aead *tfm) 194 { 195 return container_of(crypto_aead_tfm(tfm)->__crt_alg, 196 struct aead_alg, base); 197 } 198 199 static inline unsigned int crypto_aead_alg_ivsize(struct aead_alg *alg) 200 { 201 return alg->ivsize; 202 } 203 204 /** 205 * crypto_aead_ivsize() - obtain IV size 206 * @tfm: cipher handle 207 * 208 * The size of the IV for the aead referenced by the cipher handle is 209 * returned. This IV size may be zero if the cipher does not need an IV. 210 * 211 * Return: IV size in bytes 212 */ 213 static inline unsigned int crypto_aead_ivsize(struct crypto_aead *tfm) 214 { 215 return crypto_aead_alg_ivsize(crypto_aead_alg(tfm)); 216 } 217 218 /** 219 * crypto_aead_authsize() - obtain maximum authentication data size 220 * @tfm: cipher handle 221 * 222 * The maximum size of the authentication data for the AEAD cipher referenced 223 * by the AEAD cipher handle is returned. The authentication data size may be 224 * zero if the cipher implements a hard-coded maximum. 225 * 226 * The authentication data may also be known as "tag value". 227 * 228 * Return: authentication data size / tag size in bytes 229 */ 230 static inline unsigned int crypto_aead_authsize(struct crypto_aead *tfm) 231 { 232 return tfm->authsize; 233 } 234 235 /** 236 * crypto_aead_blocksize() - obtain block size of cipher 237 * @tfm: cipher handle 238 * 239 * The block size for the AEAD referenced with the cipher handle is returned. 240 * The caller may use that information to allocate appropriate memory for the 241 * data returned by the encryption or decryption operation 242 * 243 * Return: block size of cipher 244 */ 245 static inline unsigned int crypto_aead_blocksize(struct crypto_aead *tfm) 246 { 247 return crypto_tfm_alg_blocksize(crypto_aead_tfm(tfm)); 248 } 249 250 static inline unsigned int crypto_aead_alignmask(struct crypto_aead *tfm) 251 { 252 return crypto_tfm_alg_alignmask(crypto_aead_tfm(tfm)); 253 } 254 255 static inline u32 crypto_aead_get_flags(struct crypto_aead *tfm) 256 { 257 return crypto_tfm_get_flags(crypto_aead_tfm(tfm)); 258 } 259 260 static inline void crypto_aead_set_flags(struct crypto_aead *tfm, u32 flags) 261 { 262 crypto_tfm_set_flags(crypto_aead_tfm(tfm), flags); 263 } 264 265 static inline void crypto_aead_clear_flags(struct crypto_aead *tfm, u32 flags) 266 { 267 crypto_tfm_clear_flags(crypto_aead_tfm(tfm), flags); 268 } 269 270 /** 271 * crypto_aead_setkey() - set key for cipher 272 * @tfm: cipher handle 273 * @key: buffer holding the key 274 * @keylen: length of the key in bytes 275 * 276 * The caller provided key is set for the AEAD referenced by the cipher 277 * handle. 278 * 279 * Note, the key length determines the cipher type. Many block ciphers implement 280 * different cipher modes depending on the key size, such as AES-128 vs AES-192 281 * vs. AES-256. When providing a 16 byte key for an AES cipher handle, AES-128 282 * is performed. 283 * 284 * Return: 0 if the setting of the key was successful; < 0 if an error occurred 285 */ 286 int crypto_aead_setkey(struct crypto_aead *tfm, 287 const u8 *key, unsigned int keylen); 288 289 /** 290 * crypto_aead_setauthsize() - set authentication data size 291 * @tfm: cipher handle 292 * @authsize: size of the authentication data / tag in bytes 293 * 294 * Set the authentication data size / tag size. AEAD requires an authentication 295 * tag (or MAC) in addition to the associated data. 296 * 297 * Return: 0 if the setting of the key was successful; < 0 if an error occurred 298 */ 299 int crypto_aead_setauthsize(struct crypto_aead *tfm, unsigned int authsize); 300 301 static inline struct crypto_aead *crypto_aead_reqtfm(struct aead_request *req) 302 { 303 return __crypto_aead_cast(req->base.tfm); 304 } 305 306 /** 307 * crypto_aead_encrypt() - encrypt plaintext 308 * @req: reference to the aead_request handle that holds all information 309 * needed to perform the cipher operation 310 * 311 * Encrypt plaintext data using the aead_request handle. That data structure 312 * and how it is filled with data is discussed with the aead_request_* 313 * functions. 314 * 315 * IMPORTANT NOTE The encryption operation creates the authentication data / 316 * tag. That data is concatenated with the created ciphertext. 317 * The ciphertext memory size is therefore the given number of 318 * block cipher blocks + the size defined by the 319 * crypto_aead_setauthsize invocation. The caller must ensure 320 * that sufficient memory is available for the ciphertext and 321 * the authentication tag. 322 * 323 * Return: 0 if the cipher operation was successful; < 0 if an error occurred 324 */ 325 static inline int crypto_aead_encrypt(struct aead_request *req) 326 { 327 return crypto_aead_alg(crypto_aead_reqtfm(req))->encrypt(req); 328 } 329 330 /** 331 * crypto_aead_decrypt() - decrypt ciphertext 332 * @req: reference to the ablkcipher_request handle that holds all information 333 * needed to perform the cipher operation 334 * 335 * Decrypt ciphertext data using the aead_request handle. That data structure 336 * and how it is filled with data is discussed with the aead_request_* 337 * functions. 338 * 339 * IMPORTANT NOTE The caller must concatenate the ciphertext followed by the 340 * authentication data / tag. That authentication data / tag 341 * must have the size defined by the crypto_aead_setauthsize 342 * invocation. 343 * 344 * 345 * Return: 0 if the cipher operation was successful; -EBADMSG: The AEAD 346 * cipher operation performs the authentication of the data during the 347 * decryption operation. Therefore, the function returns this error if 348 * the authentication of the ciphertext was unsuccessful (i.e. the 349 * integrity of the ciphertext or the associated data was violated); 350 * < 0 if an error occurred. 351 */ 352 static inline int crypto_aead_decrypt(struct aead_request *req) 353 { 354 struct crypto_aead *aead = crypto_aead_reqtfm(req); 355 356 if (req->cryptlen < crypto_aead_authsize(aead)) 357 return -EINVAL; 358 359 return crypto_aead_alg(aead)->decrypt(req); 360 } 361 362 /** 363 * DOC: Asynchronous AEAD Request Handle 364 * 365 * The aead_request data structure contains all pointers to data required for 366 * the AEAD cipher operation. This includes the cipher handle (which can be 367 * used by multiple aead_request instances), pointer to plaintext and 368 * ciphertext, asynchronous callback function, etc. It acts as a handle to the 369 * aead_request_* API calls in a similar way as AEAD handle to the 370 * crypto_aead_* API calls. 371 */ 372 373 /** 374 * crypto_aead_reqsize() - obtain size of the request data structure 375 * @tfm: cipher handle 376 * 377 * Return: number of bytes 378 */ 379 static inline unsigned int crypto_aead_reqsize(struct crypto_aead *tfm) 380 { 381 return tfm->reqsize; 382 } 383 384 /** 385 * aead_request_set_tfm() - update cipher handle reference in request 386 * @req: request handle to be modified 387 * @tfm: cipher handle that shall be added to the request handle 388 * 389 * Allow the caller to replace the existing aead handle in the request 390 * data structure with a different one. 391 */ 392 static inline void aead_request_set_tfm(struct aead_request *req, 393 struct crypto_aead *tfm) 394 { 395 req->base.tfm = crypto_aead_tfm(tfm); 396 } 397 398 /** 399 * aead_request_alloc() - allocate request data structure 400 * @tfm: cipher handle to be registered with the request 401 * @gfp: memory allocation flag that is handed to kmalloc by the API call. 402 * 403 * Allocate the request data structure that must be used with the AEAD 404 * encrypt and decrypt API calls. During the allocation, the provided aead 405 * handle is registered in the request data structure. 406 * 407 * Return: allocated request handle in case of success; IS_ERR() is true in case 408 * of an error, PTR_ERR() returns the error code. 409 */ 410 static inline struct aead_request *aead_request_alloc(struct crypto_aead *tfm, 411 gfp_t gfp) 412 { 413 struct aead_request *req; 414 415 req = kmalloc(sizeof(*req) + crypto_aead_reqsize(tfm), gfp); 416 417 if (likely(req)) 418 aead_request_set_tfm(req, tfm); 419 420 return req; 421 } 422 423 /** 424 * aead_request_free() - zeroize and free request data structure 425 * @req: request data structure cipher handle to be freed 426 */ 427 static inline void aead_request_free(struct aead_request *req) 428 { 429 kzfree(req); 430 } 431 432 /** 433 * aead_request_set_callback() - set asynchronous callback function 434 * @req: request handle 435 * @flags: specify zero or an ORing of the flags 436 * CRYPTO_TFM_REQ_MAY_BACKLOG the request queue may back log and 437 * increase the wait queue beyond the initial maximum size; 438 * CRYPTO_TFM_REQ_MAY_SLEEP the request processing may sleep 439 * @compl: callback function pointer to be registered with the request handle 440 * @data: The data pointer refers to memory that is not used by the kernel 441 * crypto API, but provided to the callback function for it to use. Here, 442 * the caller can provide a reference to memory the callback function can 443 * operate on. As the callback function is invoked asynchronously to the 444 * related functionality, it may need to access data structures of the 445 * related functionality which can be referenced using this pointer. The 446 * callback function can access the memory via the "data" field in the 447 * crypto_async_request data structure provided to the callback function. 448 * 449 * Setting the callback function that is triggered once the cipher operation 450 * completes 451 * 452 * The callback function is registered with the aead_request handle and 453 * must comply with the following template 454 * 455 * void callback_function(struct crypto_async_request *req, int error) 456 */ 457 static inline void aead_request_set_callback(struct aead_request *req, 458 u32 flags, 459 crypto_completion_t compl, 460 void *data) 461 { 462 req->base.complete = compl; 463 req->base.data = data; 464 req->base.flags = flags; 465 } 466 467 /** 468 * aead_request_set_crypt - set data buffers 469 * @req: request handle 470 * @src: source scatter / gather list 471 * @dst: destination scatter / gather list 472 * @cryptlen: number of bytes to process from @src 473 * @iv: IV for the cipher operation which must comply with the IV size defined 474 * by crypto_aead_ivsize() 475 * 476 * Setting the source data and destination data scatter / gather lists which 477 * hold the associated data concatenated with the plaintext or ciphertext. See 478 * below for the authentication tag. 479 * 480 * For encryption, the source is treated as the plaintext and the 481 * destination is the ciphertext. For a decryption operation, the use is 482 * reversed - the source is the ciphertext and the destination is the plaintext. 483 * 484 * For both src/dst the layout is associated data, plain/cipher text, 485 * authentication tag. 486 * 487 * The content of the AD in the destination buffer after processing 488 * will either be untouched, or it will contain a copy of the AD 489 * from the source buffer. In order to ensure that it always has 490 * a copy of the AD, the user must copy the AD over either before 491 * or after processing. Of course this is not relevant if the user 492 * is doing in-place processing where src == dst. 493 * 494 * IMPORTANT NOTE AEAD requires an authentication tag (MAC). For decryption, 495 * the caller must concatenate the ciphertext followed by the 496 * authentication tag and provide the entire data stream to the 497 * decryption operation (i.e. the data length used for the 498 * initialization of the scatterlist and the data length for the 499 * decryption operation is identical). For encryption, however, 500 * the authentication tag is created while encrypting the data. 501 * The destination buffer must hold sufficient space for the 502 * ciphertext and the authentication tag while the encryption 503 * invocation must only point to the plaintext data size. The 504 * following code snippet illustrates the memory usage 505 * buffer = kmalloc(ptbuflen + (enc ? authsize : 0)); 506 * sg_init_one(&sg, buffer, ptbuflen + (enc ? authsize : 0)); 507 * aead_request_set_crypt(req, &sg, &sg, ptbuflen, iv); 508 */ 509 static inline void aead_request_set_crypt(struct aead_request *req, 510 struct scatterlist *src, 511 struct scatterlist *dst, 512 unsigned int cryptlen, u8 *iv) 513 { 514 req->src = src; 515 req->dst = dst; 516 req->cryptlen = cryptlen; 517 req->iv = iv; 518 } 519 520 /** 521 * aead_request_set_ad - set associated data information 522 * @req: request handle 523 * @assoclen: number of bytes in associated data 524 * 525 * Setting the AD information. This function sets the length of 526 * the associated data. 527 */ 528 static inline void aead_request_set_ad(struct aead_request *req, 529 unsigned int assoclen) 530 { 531 req->assoclen = assoclen; 532 } 533 534 #endif /* _CRYPTO_AEAD_H */ 535