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 * @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 */
136struct 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
154struct crypto_aead {
155 unsigned int authsize;
156 unsigned int reqsize;
157
158 struct crypto_tfm base;
159};
160
161static 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 */
180struct crypto_aead *crypto_alloc_aead(const char *alg_name, u32 type, u32 mask);
181
182static 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 */
191static inline void crypto_free_aead(struct crypto_aead *tfm)
192{
193 crypto_destroy_tfm(tfm, crypto_aead_tfm(tfm));
194}
195
196static 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
202static 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 */
216static 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 */
233static 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 */
248static inline unsigned int crypto_aead_blocksize(struct crypto_aead *tfm)
249{
250 return crypto_tfm_alg_blocksize(crypto_aead_tfm(tfm));
251}
252
253static inline unsigned int crypto_aead_alignmask(struct crypto_aead *tfm)
254{
255 return crypto_tfm_alg_alignmask(crypto_aead_tfm(tfm));
256}
257
258static inline u32 crypto_aead_get_flags(struct crypto_aead *tfm)
259{
260 return crypto_tfm_get_flags(crypto_aead_tfm(tfm));
261}
262
263static 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
268static 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 */
289int 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 */
302int crypto_aead_setauthsize(struct crypto_aead *tfm, unsigned int authsize);
303
304static 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 */
328static inline int crypto_aead_encrypt(struct aead_request *req)
329{
330 struct crypto_aead *aead = crypto_aead_reqtfm(req);
331
332 if (crypto_aead_get_flags(aead) & CRYPTO_TFM_NEED_KEY)
333 return -ENOKEY;
334
335 return crypto_aead_alg(aead)->encrypt(req);
336}
337
338/**
339 * crypto_aead_decrypt() - decrypt ciphertext
340 * @req: reference to the ablkcipher_request handle that holds all information
341 * needed to perform the cipher operation
342 *
343 * Decrypt ciphertext data using the aead_request handle. That data structure
344 * and how it is filled with data is discussed with the aead_request_*
345 * functions.
346 *
347 * IMPORTANT NOTE The caller must concatenate the ciphertext followed by the
348 * authentication data / tag. That authentication data / tag
349 * must have the size defined by the crypto_aead_setauthsize
350 * invocation.
351 *
352 *
353 * Return: 0 if the cipher operation was successful; -EBADMSG: The AEAD
354 * cipher operation performs the authentication of the data during the
355 * decryption operation. Therefore, the function returns this error if
356 * the authentication of the ciphertext was unsuccessful (i.e. the
357 * integrity of the ciphertext or the associated data was violated);
358 * < 0 if an error occurred.
359 */
360static inline int crypto_aead_decrypt(struct aead_request *req)
361{
362 struct crypto_aead *aead = crypto_aead_reqtfm(req);
363
364 if (crypto_aead_get_flags(aead) & CRYPTO_TFM_NEED_KEY)
365 return -ENOKEY;
366
367 if (req->cryptlen < crypto_aead_authsize(aead))
368 return -EINVAL;
369
370 return crypto_aead_alg(aead)->decrypt(req);
371}
372
373/**
374 * DOC: Asynchronous AEAD Request Handle
375 *
376 * The aead_request data structure contains all pointers to data required for
377 * the AEAD cipher operation. This includes the cipher handle (which can be
378 * used by multiple aead_request instances), pointer to plaintext and
379 * ciphertext, asynchronous callback function, etc. It acts as a handle to the
380 * aead_request_* API calls in a similar way as AEAD handle to the
381 * crypto_aead_* API calls.
382 */
383
384/**
385 * crypto_aead_reqsize() - obtain size of the request data structure
386 * @tfm: cipher handle
387 *
388 * Return: number of bytes
389 */
390static inline unsigned int crypto_aead_reqsize(struct crypto_aead *tfm)
391{
392 return tfm->reqsize;
393}
394
395/**
396 * aead_request_set_tfm() - update cipher handle reference in request
397 * @req: request handle to be modified
398 * @tfm: cipher handle that shall be added to the request handle
399 *
400 * Allow the caller to replace the existing aead handle in the request
401 * data structure with a different one.
402 */
403static inline void aead_request_set_tfm(struct aead_request *req,
404 struct crypto_aead *tfm)
405{
406 req->base.tfm = crypto_aead_tfm(tfm);
407}
408
409/**
410 * aead_request_alloc() - allocate request data structure
411 * @tfm: cipher handle to be registered with the request
412 * @gfp: memory allocation flag that is handed to kmalloc by the API call.
413 *
414 * Allocate the request data structure that must be used with the AEAD
415 * encrypt and decrypt API calls. During the allocation, the provided aead
416 * handle is registered in the request data structure.
417 *
418 * Return: allocated request handle in case of success, or NULL if out of memory
419 */
420static inline struct aead_request *aead_request_alloc(struct crypto_aead *tfm,
421 gfp_t gfp)
422{
423 struct aead_request *req;
424
425 req = kmalloc(sizeof(*req) + crypto_aead_reqsize(tfm), gfp);
426
427 if (likely(req))
428 aead_request_set_tfm(req, tfm);
429
430 return req;
431}
432
433/**
434 * aead_request_free() - zeroize and free request data structure
435 * @req: request data structure cipher handle to be freed
436 */
437static inline void aead_request_free(struct aead_request *req)
438{
439 kzfree(req);
440}
441
442/**
443 * aead_request_set_callback() - set asynchronous callback function
444 * @req: request handle
445 * @flags: specify zero or an ORing of the flags
446 * CRYPTO_TFM_REQ_MAY_BACKLOG the request queue may back log and
447 * increase the wait queue beyond the initial maximum size;
448 * CRYPTO_TFM_REQ_MAY_SLEEP the request processing may sleep
449 * @compl: callback function pointer to be registered with the request handle
450 * @data: The data pointer refers to memory that is not used by the kernel
451 * crypto API, but provided to the callback function for it to use. Here,
452 * the caller can provide a reference to memory the callback function can
453 * operate on. As the callback function is invoked asynchronously to the
454 * related functionality, it may need to access data structures of the
455 * related functionality which can be referenced using this pointer. The
456 * callback function can access the memory via the "data" field in the
457 * crypto_async_request data structure provided to the callback function.
458 *
459 * Setting the callback function that is triggered once the cipher operation
460 * completes
461 *
462 * The callback function is registered with the aead_request handle and
463 * must comply with the following template::
464 *
465 * void callback_function(struct crypto_async_request *req, int error)
466 */
467static inline void aead_request_set_callback(struct aead_request *req,
468 u32 flags,
469 crypto_completion_t compl,
470 void *data)
471{
472 req->base.complete = compl;
473 req->base.data = data;
474 req->base.flags = flags;
475}
476
477/**
478 * aead_request_set_crypt - set data buffers
479 * @req: request handle
480 * @src: source scatter / gather list
481 * @dst: destination scatter / gather list
482 * @cryptlen: number of bytes to process from @src
483 * @iv: IV for the cipher operation which must comply with the IV size defined
484 * by crypto_aead_ivsize()
485 *
486 * Setting the source data and destination data scatter / gather lists which
487 * hold the associated data concatenated with the plaintext or ciphertext. See
488 * below for the authentication tag.
489 *
490 * For encryption, the source is treated as the plaintext and the
491 * destination is the ciphertext. For a decryption operation, the use is
492 * reversed - the source is the ciphertext and the destination is the plaintext.
493 *
494 * The memory structure for cipher operation has the following structure:
495 *
496 * - AEAD encryption input: assoc data || plaintext
497 * - AEAD encryption output: assoc data || cipherntext || auth tag
498 * - AEAD decryption input: assoc data || ciphertext || auth tag
499 * - AEAD decryption output: assoc data || plaintext
500 *
501 * Albeit the kernel requires the presence of the AAD buffer, however,
502 * the kernel does not fill the AAD buffer in the output case. If the
503 * caller wants to have that data buffer filled, the caller must either
504 * use an in-place cipher operation (i.e. same memory location for
505 * input/output memory location).
506 */
507static inline void aead_request_set_crypt(struct aead_request *req,
508 struct scatterlist *src,
509 struct scatterlist *dst,
510 unsigned int cryptlen, u8 *iv)
511{
512 req->src = src;
513 req->dst = dst;
514 req->cryptlen = cryptlen;
515 req->iv = iv;
516}
517
518/**
519 * aead_request_set_ad - set associated data information
520 * @req: request handle
521 * @assoclen: number of bytes in associated data
522 *
523 * Setting the AD information. This function sets the length of
524 * the associated data.
525 */
526static inline void aead_request_set_ad(struct aead_request *req,
527 unsigned int assoclen)
528{
529 req->assoclen = assoclen;
530}
531
532#endif /* _CRYPTO_AEAD_H */
533