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
74struct 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 */
86struct 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 * @ivsize: see struct skcipher_alg
119 * @chunksize: see struct skcipher_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 * @base: Definition of a generic crypto cipher algorithm.
132 *
133 * All fields except @ivsize is mandatory and must be filled.
134 */
135struct aead_alg {
136 int (*setkey)(struct crypto_aead *tfm, const u8 *key,
137 unsigned int keylen);
138 int (*setauthsize)(struct crypto_aead *tfm, unsigned int authsize);
139 int (*encrypt)(struct aead_request *req);
140 int (*decrypt)(struct aead_request *req);
141 int (*init)(struct crypto_aead *tfm);
142 void (*exit)(struct crypto_aead *tfm);
143
144 unsigned int ivsize;
145 unsigned int maxauthsize;
146 unsigned int chunksize;
147
148 struct crypto_alg base;
149};
150
151struct crypto_aead {
152 unsigned int authsize;
153 unsigned int reqsize;
154
155 struct crypto_tfm base;
156};
157
158static 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 */
177struct crypto_aead *crypto_alloc_aead(const char *alg_name, u32 type, u32 mask);
178
179static 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 */
188static inline void crypto_free_aead(struct crypto_aead *tfm)
189{
190 crypto_destroy_tfm(tfm, crypto_aead_tfm(tfm));
191}
192
193static 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
199static 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 */
213static 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 */
230static 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 */
245static inline unsigned int crypto_aead_blocksize(struct crypto_aead *tfm)
246{
247 return crypto_tfm_alg_blocksize(crypto_aead_tfm(tfm));
248}
249
250static inline unsigned int crypto_aead_alignmask(struct crypto_aead *tfm)
251{
252 return crypto_tfm_alg_alignmask(crypto_aead_tfm(tfm));
253}
254
255static inline u32 crypto_aead_get_flags(struct crypto_aead *tfm)
256{
257 return crypto_tfm_get_flags(crypto_aead_tfm(tfm));
258}
259
260static 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
265static 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 */
286int 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 */
299int crypto_aead_setauthsize(struct crypto_aead *tfm, unsigned int authsize);
300
301static 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 */
325static inline int crypto_aead_encrypt(struct aead_request *req)
326{
327 struct crypto_aead *aead = crypto_aead_reqtfm(req);
328 struct crypto_alg *alg = aead->base.__crt_alg;
329 unsigned int cryptlen = req->cryptlen;
330 int ret;
331
332 crypto_stats_get(alg);
333 if (crypto_aead_get_flags(aead) & CRYPTO_TFM_NEED_KEY)
334 ret = -ENOKEY;
335 else
336 ret = crypto_aead_alg(aead)->encrypt(req);
337 crypto_stats_aead_encrypt(cryptlen, alg, ret);
338 return ret;
339}
340
341/**
342 * crypto_aead_decrypt() - decrypt ciphertext
343 * @req: reference to the ablkcipher_request handle that holds all information
344 * needed to perform the cipher operation
345 *
346 * Decrypt ciphertext data using the aead_request handle. That data structure
347 * and how it is filled with data is discussed with the aead_request_*
348 * functions.
349 *
350 * IMPORTANT NOTE The caller must concatenate the ciphertext followed by the
351 * authentication data / tag. That authentication data / tag
352 * must have the size defined by the crypto_aead_setauthsize
353 * invocation.
354 *
355 *
356 * Return: 0 if the cipher operation was successful; -EBADMSG: The AEAD
357 * cipher operation performs the authentication of the data during the
358 * decryption operation. Therefore, the function returns this error if
359 * the authentication of the ciphertext was unsuccessful (i.e. the
360 * integrity of the ciphertext or the associated data was violated);
361 * < 0 if an error occurred.
362 */
363static inline int crypto_aead_decrypt(struct aead_request *req)
364{
365 struct crypto_aead *aead = crypto_aead_reqtfm(req);
366 struct crypto_alg *alg = aead->base.__crt_alg;
367 unsigned int cryptlen = req->cryptlen;
368 int ret;
369
370 crypto_stats_get(alg);
371 if (crypto_aead_get_flags(aead) & CRYPTO_TFM_NEED_KEY)
372 ret = -ENOKEY;
373 else if (req->cryptlen < crypto_aead_authsize(aead))
374 ret = -EINVAL;
375 else
376 ret = crypto_aead_alg(aead)->decrypt(req);
377 crypto_stats_aead_decrypt(cryptlen, alg, ret);
378 return ret;
379}
380
381/**
382 * DOC: Asynchronous AEAD Request Handle
383 *
384 * The aead_request data structure contains all pointers to data required for
385 * the AEAD cipher operation. This includes the cipher handle (which can be
386 * used by multiple aead_request instances), pointer to plaintext and
387 * ciphertext, asynchronous callback function, etc. It acts as a handle to the
388 * aead_request_* API calls in a similar way as AEAD handle to the
389 * crypto_aead_* API calls.
390 */
391
392/**
393 * crypto_aead_reqsize() - obtain size of the request data structure
394 * @tfm: cipher handle
395 *
396 * Return: number of bytes
397 */
398static inline unsigned int crypto_aead_reqsize(struct crypto_aead *tfm)
399{
400 return tfm->reqsize;
401}
402
403/**
404 * aead_request_set_tfm() - update cipher handle reference in request
405 * @req: request handle to be modified
406 * @tfm: cipher handle that shall be added to the request handle
407 *
408 * Allow the caller to replace the existing aead handle in the request
409 * data structure with a different one.
410 */
411static inline void aead_request_set_tfm(struct aead_request *req,
412 struct crypto_aead *tfm)
413{
414 req->base.tfm = crypto_aead_tfm(tfm);
415}
416
417/**
418 * aead_request_alloc() - allocate request data structure
419 * @tfm: cipher handle to be registered with the request
420 * @gfp: memory allocation flag that is handed to kmalloc by the API call.
421 *
422 * Allocate the request data structure that must be used with the AEAD
423 * encrypt and decrypt API calls. During the allocation, the provided aead
424 * handle is registered in the request data structure.
425 *
426 * Return: allocated request handle in case of success, or NULL if out of memory
427 */
428static inline struct aead_request *aead_request_alloc(struct crypto_aead *tfm,
429 gfp_t gfp)
430{
431 struct aead_request *req;
432
433 req = kmalloc(sizeof(*req) + crypto_aead_reqsize(tfm), gfp);
434
435 if (likely(req))
436 aead_request_set_tfm(req, tfm);
437
438 return req;
439}
440
441/**
442 * aead_request_free() - zeroize and free request data structure
443 * @req: request data structure cipher handle to be freed
444 */
445static inline void aead_request_free(struct aead_request *req)
446{
447 kzfree(req);
448}
449
450/**
451 * aead_request_set_callback() - set asynchronous callback function
452 * @req: request handle
453 * @flags: specify zero or an ORing of the flags
454 * CRYPTO_TFM_REQ_MAY_BACKLOG the request queue may back log and
455 * increase the wait queue beyond the initial maximum size;
456 * CRYPTO_TFM_REQ_MAY_SLEEP the request processing may sleep
457 * @compl: callback function pointer to be registered with the request handle
458 * @data: The data pointer refers to memory that is not used by the kernel
459 * crypto API, but provided to the callback function for it to use. Here,
460 * the caller can provide a reference to memory the callback function can
461 * operate on. As the callback function is invoked asynchronously to the
462 * related functionality, it may need to access data structures of the
463 * related functionality which can be referenced using this pointer. The
464 * callback function can access the memory via the "data" field in the
465 * crypto_async_request data structure provided to the callback function.
466 *
467 * Setting the callback function that is triggered once the cipher operation
468 * completes
469 *
470 * The callback function is registered with the aead_request handle and
471 * must comply with the following template::
472 *
473 * void callback_function(struct crypto_async_request *req, int error)
474 */
475static inline void aead_request_set_callback(struct aead_request *req,
476 u32 flags,
477 crypto_completion_t compl,
478 void *data)
479{
480 req->base.complete = compl;
481 req->base.data = data;
482 req->base.flags = flags;
483}
484
485/**
486 * aead_request_set_crypt - set data buffers
487 * @req: request handle
488 * @src: source scatter / gather list
489 * @dst: destination scatter / gather list
490 * @cryptlen: number of bytes to process from @src
491 * @iv: IV for the cipher operation which must comply with the IV size defined
492 * by crypto_aead_ivsize()
493 *
494 * Setting the source data and destination data scatter / gather lists which
495 * hold the associated data concatenated with the plaintext or ciphertext. See
496 * below for the authentication tag.
497 *
498 * For encryption, the source is treated as the plaintext and the
499 * destination is the ciphertext. For a decryption operation, the use is
500 * reversed - the source is the ciphertext and the destination is the plaintext.
501 *
502 * The memory structure for cipher operation has the following structure:
503 *
504 * - AEAD encryption input: assoc data || plaintext
505 * - AEAD encryption output: assoc data || cipherntext || auth tag
506 * - AEAD decryption input: assoc data || ciphertext || auth tag
507 * - AEAD decryption output: assoc data || plaintext
508 *
509 * Albeit the kernel requires the presence of the AAD buffer, however,
510 * the kernel does not fill the AAD buffer in the output case. If the
511 * caller wants to have that data buffer filled, the caller must either
512 * use an in-place cipher operation (i.e. same memory location for
513 * input/output memory location).
514 */
515static inline void aead_request_set_crypt(struct aead_request *req,
516 struct scatterlist *src,
517 struct scatterlist *dst,
518 unsigned int cryptlen, u8 *iv)
519{
520 req->src = src;
521 req->dst = dst;
522 req->cryptlen = cryptlen;
523 req->iv = iv;
524}
525
526/**
527 * aead_request_set_ad - set associated data information
528 * @req: request handle
529 * @assoclen: number of bytes in associated data
530 *
531 * Setting the AD information. This function sets the length of
532 * the associated data.
533 */
534static inline void aead_request_set_ad(struct aead_request *req,
535 unsigned int assoclen)
536{
537 req->assoclen = assoclen;
538}
539
540#endif /* _CRYPTO_AEAD_H */
541