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Linux/include/crypto/aead.h

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  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  * @base: Definition of a generic crypto cipher algorithm.
132  *
133  * All fields except @ivsize is mandatory and must be filled.
134  */
135 struct 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         const char *geniv;
145 
146         unsigned int ivsize;
147         unsigned int maxauthsize;
148 
149         struct crypto_alg base;
150 };
151 
152 struct crypto_aead {
153         unsigned int authsize;
154         unsigned int reqsize;
155 
156         struct crypto_tfm base;
157 };
158 
159 static inline struct crypto_aead *__crypto_aead_cast(struct crypto_tfm *tfm)
160 {
161         return container_of(tfm, struct crypto_aead, base);
162 }
163 
164 /**
165  * crypto_alloc_aead() - allocate AEAD cipher handle
166  * @alg_name: is the cra_name / name or cra_driver_name / driver name of the
167  *           AEAD cipher
168  * @type: specifies the type of the cipher
169  * @mask: specifies the mask for the cipher
170  *
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.
174  *
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.
177  */
178 struct crypto_aead *crypto_alloc_aead(const char *alg_name, u32 type, u32 mask);
179 
180 static inline struct crypto_tfm *crypto_aead_tfm(struct crypto_aead *tfm)
181 {
182         return &tfm->base;
183 }
184 
185 /**
186  * crypto_free_aead() - zeroize and free aead handle
187  * @tfm: cipher handle to be freed
188  */
189 static inline void crypto_free_aead(struct crypto_aead *tfm)
190 {
191         crypto_destroy_tfm(tfm, crypto_aead_tfm(tfm));
192 }
193 
194 static inline struct aead_alg *crypto_aead_alg(struct crypto_aead *tfm)
195 {
196         return container_of(crypto_aead_tfm(tfm)->__crt_alg,
197                             struct aead_alg, base);
198 }
199 
200 static inline unsigned int crypto_aead_alg_ivsize(struct aead_alg *alg)
201 {
202         return alg->ivsize;
203 }
204 
205 /**
206  * crypto_aead_ivsize() - obtain IV size
207  * @tfm: cipher handle
208  *
209  * The size of the IV for the aead referenced by the cipher handle is
210  * returned. This IV size may be zero if the cipher does not need an IV.
211  *
212  * Return: IV size in bytes
213  */
214 static inline unsigned int crypto_aead_ivsize(struct crypto_aead *tfm)
215 {
216         return crypto_aead_alg_ivsize(crypto_aead_alg(tfm));
217 }
218 
219 /**
220  * crypto_aead_authsize() - obtain maximum authentication data size
221  * @tfm: cipher handle
222  *
223  * The maximum size of the authentication data for the AEAD cipher referenced
224  * by the AEAD cipher handle is returned. The authentication data size may be
225  * zero if the cipher implements a hard-coded maximum.
226  *
227  * The authentication data may also be known as "tag value".
228  *
229  * Return: authentication data size / tag size in bytes
230  */
231 static inline unsigned int crypto_aead_authsize(struct crypto_aead *tfm)
232 {
233         return tfm->authsize;
234 }
235 
236 /**
237  * crypto_aead_blocksize() - obtain block size of cipher
238  * @tfm: cipher handle
239  *
240  * The block size for the AEAD referenced with the cipher handle is returned.
241  * The caller may use that information to allocate appropriate memory for the
242  * data returned by the encryption or decryption operation
243  *
244  * Return: block size of cipher
245  */
246 static inline unsigned int crypto_aead_blocksize(struct crypto_aead *tfm)
247 {
248         return crypto_tfm_alg_blocksize(crypto_aead_tfm(tfm));
249 }
250 
251 static inline unsigned int crypto_aead_alignmask(struct crypto_aead *tfm)
252 {
253         return crypto_tfm_alg_alignmask(crypto_aead_tfm(tfm));
254 }
255 
256 static inline u32 crypto_aead_get_flags(struct crypto_aead *tfm)
257 {
258         return crypto_tfm_get_flags(crypto_aead_tfm(tfm));
259 }
260 
261 static inline void crypto_aead_set_flags(struct crypto_aead *tfm, u32 flags)
262 {
263         crypto_tfm_set_flags(crypto_aead_tfm(tfm), flags);
264 }
265 
266 static inline void crypto_aead_clear_flags(struct crypto_aead *tfm, u32 flags)
267 {
268         crypto_tfm_clear_flags(crypto_aead_tfm(tfm), flags);
269 }
270 
271 /**
272  * crypto_aead_setkey() - set key for cipher
273  * @tfm: cipher handle
274  * @key: buffer holding the key
275  * @keylen: length of the key in bytes
276  *
277  * The caller provided key is set for the AEAD referenced by the cipher
278  * handle.
279  *
280  * Note, the key length determines the cipher type. Many block ciphers implement
281  * different cipher modes depending on the key size, such as AES-128 vs AES-192
282  * vs. AES-256. When providing a 16 byte key for an AES cipher handle, AES-128
283  * is performed.
284  *
285  * Return: 0 if the setting of the key was successful; < 0 if an error occurred
286  */
287 int crypto_aead_setkey(struct crypto_aead *tfm,
288                        const u8 *key, unsigned int keylen);
289 
290 /**
291  * crypto_aead_setauthsize() - set authentication data size
292  * @tfm: cipher handle
293  * @authsize: size of the authentication data / tag in bytes
294  *
295  * Set the authentication data size / tag size. AEAD requires an authentication
296  * tag (or MAC) in addition to the associated data.
297  *
298  * Return: 0 if the setting of the key was successful; < 0 if an error occurred
299  */
300 int crypto_aead_setauthsize(struct crypto_aead *tfm, unsigned int authsize);
301 
302 static inline struct crypto_aead *crypto_aead_reqtfm(struct aead_request *req)
303 {
304         return __crypto_aead_cast(req->base.tfm);
305 }
306 
307 /**
308  * crypto_aead_encrypt() - encrypt plaintext
309  * @req: reference to the aead_request handle that holds all information
310  *       needed to perform the cipher operation
311  *
312  * Encrypt plaintext data using the aead_request handle. That data structure
313  * and how it is filled with data is discussed with the aead_request_*
314  * functions.
315  *
316  * IMPORTANT NOTE The encryption operation creates the authentication data /
317  *                tag. That data is concatenated with the created ciphertext.
318  *                The ciphertext memory size is therefore the given number of
319  *                block cipher blocks + the size defined by the
320  *                crypto_aead_setauthsize invocation. The caller must ensure
321  *                that sufficient memory is available for the ciphertext and
322  *                the authentication tag.
323  *
324  * Return: 0 if the cipher operation was successful; < 0 if an error occurred
325  */
326 static inline int crypto_aead_encrypt(struct aead_request *req)
327 {
328         return crypto_aead_alg(crypto_aead_reqtfm(req))->encrypt(req);
329 }
330 
331 /**
332  * crypto_aead_decrypt() - decrypt ciphertext
333  * @req: reference to the ablkcipher_request handle that holds all information
334  *       needed to perform the cipher operation
335  *
336  * Decrypt ciphertext data using the aead_request handle. That data structure
337  * and how it is filled with data is discussed with the aead_request_*
338  * functions.
339  *
340  * IMPORTANT NOTE The caller must concatenate the ciphertext followed by the
341  *                authentication data / tag. That authentication data / tag
342  *                must have the size defined by the crypto_aead_setauthsize
343  *                invocation.
344  *
345  *
346  * Return: 0 if the cipher operation was successful; -EBADMSG: The AEAD
347  *         cipher operation performs the authentication of the data during the
348  *         decryption operation. Therefore, the function returns this error if
349  *         the authentication of the ciphertext was unsuccessful (i.e. the
350  *         integrity of the ciphertext or the associated data was violated);
351  *         < 0 if an error occurred.
352  */
353 static inline int crypto_aead_decrypt(struct aead_request *req)
354 {
355         struct crypto_aead *aead = crypto_aead_reqtfm(req);
356 
357         if (req->cryptlen < crypto_aead_authsize(aead))
358                 return -EINVAL;
359 
360         return crypto_aead_alg(aead)->decrypt(req);
361 }
362 
363 /**
364  * DOC: Asynchronous AEAD Request Handle
365  *
366  * The aead_request data structure contains all pointers to data required for
367  * the AEAD cipher operation. This includes the cipher handle (which can be
368  * used by multiple aead_request instances), pointer to plaintext and
369  * ciphertext, asynchronous callback function, etc. It acts as a handle to the
370  * aead_request_* API calls in a similar way as AEAD handle to the
371  * crypto_aead_* API calls.
372  */
373 
374 /**
375  * crypto_aead_reqsize() - obtain size of the request data structure
376  * @tfm: cipher handle
377  *
378  * Return: number of bytes
379  */
380 static inline unsigned int crypto_aead_reqsize(struct crypto_aead *tfm)
381 {
382         return tfm->reqsize;
383 }
384 
385 /**
386  * aead_request_set_tfm() - update cipher handle reference in request
387  * @req: request handle to be modified
388  * @tfm: cipher handle that shall be added to the request handle
389  *
390  * Allow the caller to replace the existing aead handle in the request
391  * data structure with a different one.
392  */
393 static inline void aead_request_set_tfm(struct aead_request *req,
394                                         struct crypto_aead *tfm)
395 {
396         req->base.tfm = crypto_aead_tfm(tfm);
397 }
398 
399 /**
400  * aead_request_alloc() - allocate request data structure
401  * @tfm: cipher handle to be registered with the request
402  * @gfp: memory allocation flag that is handed to kmalloc by the API call.
403  *
404  * Allocate the request data structure that must be used with the AEAD
405  * encrypt and decrypt API calls. During the allocation, the provided aead
406  * handle is registered in the request data structure.
407  *
408  * Return: allocated request handle in case of success; IS_ERR() is true in case
409  *         of an error, PTR_ERR() returns the error code.
410  */
411 static inline struct aead_request *aead_request_alloc(struct crypto_aead *tfm,
412                                                       gfp_t gfp)
413 {
414         struct aead_request *req;
415 
416         req = kmalloc(sizeof(*req) + crypto_aead_reqsize(tfm), gfp);
417 
418         if (likely(req))
419                 aead_request_set_tfm(req, tfm);
420 
421         return req;
422 }
423 
424 /**
425  * aead_request_free() - zeroize and free request data structure
426  * @req: request data structure cipher handle to be freed
427  */
428 static inline void aead_request_free(struct aead_request *req)
429 {
430         kzfree(req);
431 }
432 
433 /**
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.
449  *
450  * Setting the callback function that is triggered once the cipher operation
451  * completes
452  *
453  * The callback function is registered with the aead_request handle and
454  * must comply with the following template
455  *
456  *      void callback_function(struct crypto_async_request *req, int error)
457  */
458 static inline void aead_request_set_callback(struct aead_request *req,
459                                              u32 flags,
460                                              crypto_completion_t compl,
461                                              void *data)
462 {
463         req->base.complete = compl;
464         req->base.data = data;
465         req->base.flags = flags;
466 }
467 
468 /**
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()
476  *
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.
480  *
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.
484  *
485  * For both src/dst the layout is associated data, plain/cipher text,
486  * authentication tag.
487  *
488  * The content of the AD in the destination buffer after processing
489  * will either be untouched, or it will contain a copy of the AD
490  * from the source buffer.  In order to ensure that it always has
491  * a copy of the AD, the user must copy the AD over either before
492  * or after processing.  Of course this is not relevant if the user
493  * is doing in-place processing where src == dst.
494  *
495  * IMPORTANT NOTE AEAD requires an authentication tag (MAC). For decryption,
496  *                the caller must concatenate the ciphertext followed by the
497  *                authentication tag and provide the entire data stream to the
498  *                decryption operation (i.e. the data length used for the
499  *                initialization of the scatterlist and the data length for the
500  *                decryption operation is identical). For encryption, however,
501  *                the authentication tag is created while encrypting the data.
502  *                The destination buffer must hold sufficient space for the
503  *                ciphertext and the authentication tag while the encryption
504  *                invocation must only point to the plaintext data size. The
505  *                following code snippet illustrates the memory usage
506  *                buffer = kmalloc(ptbuflen + (enc ? authsize : 0));
507  *                sg_init_one(&sg, buffer, ptbuflen + (enc ? authsize : 0));
508  *                aead_request_set_crypt(req, &sg, &sg, ptbuflen, iv);
509  */
510 static inline void aead_request_set_crypt(struct aead_request *req,
511                                           struct scatterlist *src,
512                                           struct scatterlist *dst,
513                                           unsigned int cryptlen, u8 *iv)
514 {
515         req->src = src;
516         req->dst = dst;
517         req->cryptlen = cryptlen;
518         req->iv = iv;
519 }
520 
521 /**
522  * aead_request_set_ad - set associated data information
523  * @req: request handle
524  * @assoclen: number of bytes in associated data
525  *
526  * Setting the AD information.  This function sets the length of
527  * the associated data.
528  */
529 static inline void aead_request_set_ad(struct aead_request *req,
530                                        unsigned int assoclen)
531 {
532         req->assoclen = assoclen;
533 }
534 
535 #endif  /* _CRYPTO_AEAD_H */
536 

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