aead.h revision bb1ceac29bc7a18b94e3da78057dc41aa7071784
1/* Copyright (c) 2014, Google Inc. 2 * 3 * Permission to use, copy, modify, and/or distribute this software for any 4 * purpose with or without fee is hereby granted, provided that the above 5 * copyright notice and this permission notice appear in all copies. 6 * 7 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES 8 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF 9 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY 10 * SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES 11 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION 12 * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN 13 * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */ 14 15#ifndef OPENSSL_HEADER_AEAD_H 16#define OPENSSL_HEADER_AEAD_H 17 18#include <openssl/base.h> 19 20#if defined(__cplusplus) 21extern "C" { 22#endif 23 24 25/* Authenticated Encryption with Additional Data. 26 * 27 * AEAD couples confidentiality and integrity in a single primitive. AEAD 28 * algorithms take a key and then can seal and open individual messages. Each 29 * message has a unique, per-message nonce and, optionally, additional data 30 * which is authenticated but not included in the ciphertext. 31 * 32 * The |EVP_AEAD_CTX_init| function initialises an |EVP_AEAD_CTX| structure and 33 * performs any precomputation needed to use |aead| with |key|. The length of 34 * the key, |key_len|, is given in bytes. 35 * 36 * The |tag_len| argument contains the length of the tags, in bytes, and allows 37 * for the processing of truncated authenticators. A zero value indicates that 38 * the default tag length should be used and this is defined as 39 * |EVP_AEAD_DEFAULT_TAG_LENGTH| in order to make the code clear. Using 40 * truncated tags increases an attacker's chance of creating a valid forgery. 41 * Be aware that the attacker's chance may increase more than exponentially as 42 * would naively be expected. 43 * 44 * When no longer needed, the initialised |EVP_AEAD_CTX| structure must be 45 * passed to |EVP_AEAD_CTX_cleanup|, which will deallocate any memory used. 46 * 47 * With an |EVP_AEAD_CTX| in hand, one can seal and open messages. These 48 * operations are intended to meet the standard notions of privacy and 49 * authenticity for authenticated encryption. For formal definitions see 50 * Bellare and Namprempre, "Authenticated encryption: relations among notions 51 * and analysis of the generic composition paradigm," Lecture Notes in Computer 52 * Science B<1976> (2000), 531–545, 53 * http://www-cse.ucsd.edu/~mihir/papers/oem.html. 54 * 55 * When sealing messages, a nonce must be given. The length of the nonce is 56 * fixed by the AEAD in use and is returned by |EVP_AEAD_nonce_length|. *The 57 * nonce must be unique for all messages with the same key*. This is critically 58 * important - nonce reuse may completely undermine the security of the AEAD. 59 * Nonces may be predictable and public, so long as they are unique. Uniqueness 60 * may be achieved with a simple counter or, if large enough, may be generated 61 * randomly. The nonce must be passed into the "open" operation by the receiver 62 * so must either be implicit (e.g. a counter), or must be transmitted along 63 * with the sealed message. 64 * 65 * The "seal" and "open" operations are atomic - an entire message must be 66 * encrypted or decrypted in a single call. Large messages may have to be split 67 * up in order to accomodate this. When doing so, be mindful of the need not to 68 * repeat nonces and the possibility that an attacker could duplicate, reorder 69 * or drop message chunks. For example, using a single key for a given (large) 70 * message and sealing chunks with nonces counting from zero would be secure as 71 * long as the number of chunks was securely transmitted. (Otherwise an 72 * attacker could truncate the message by dropping chunks from the end.) 73 * 74 * The number of chunks could be transmitted by prefixing it to the plaintext, 75 * for example. This also assumes that no other message would ever use the same 76 * key otherwise the rule that nonces must be unique for a given key would be 77 * violated. 78 * 79 * The "seal" and "open" operations also permit additional data to be 80 * authenticated via the |ad| parameter. This data is not included in the 81 * ciphertext and must be identical for both the "seal" and "open" call. This 82 * permits implicit context to be authenticated but may be empty if not needed. 83 * 84 * The "seal" and "open" operations may work in-place if the |out| and |in| 85 * arguments are equal. Otherwise, if |out| and |in| alias, input data may be 86 * overwritten before it is read. This situation will cause an error. 87 * 88 * The "seal" and "open" operations return one on success and zero on error. */ 89 90 91/* AEAD algorithms. */ 92 93/* EVP_aead_aes_128_gcm is AES-128 in Galois Counter Mode. */ 94OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_128_gcm(void); 95 96/* EVP_aead_aes_256_gcm is AES-256 in Galois Counter Mode. */ 97OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_256_gcm(void); 98 99/* EVP_aead_chacha20_poly1305 is the AEAD built from ChaCha20 and 100 * Poly1305 as described in RFC 7539. */ 101OPENSSL_EXPORT const EVP_AEAD *EVP_aead_chacha20_poly1305(void); 102 103/* EVP_aead_chacha20_poly1305_old is an AEAD built from ChaCha20 and 104 * Poly1305 that is used in the experimental ChaCha20-Poly1305 TLS cipher 105 * suites. */ 106OPENSSL_EXPORT const EVP_AEAD *EVP_aead_chacha20_poly1305_old(void); 107 108/* EVP_aead_aes_128_ctr_hmac_sha256 is AES-128 in CTR mode with HMAC-SHA256 for 109 * authentication. The nonce is 12 bytes; the bottom 32-bits are used as the 110 * block counter, thus the maximum plaintext size is 64GB. */ 111OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_128_ctr_hmac_sha256(void); 112 113/* EVP_aead_aes_256_ctr_hmac_sha256 is AES-256 in CTR mode with HMAC-SHA256 for 114 * authentication. See |EVP_aead_aes_128_ctr_hmac_sha256| for details. */ 115OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_256_ctr_hmac_sha256(void); 116 117/* EVP_has_aes_hardware returns one if we enable hardware support for fast and 118 * constant-time AES-GCM. */ 119OPENSSL_EXPORT int EVP_has_aes_hardware(void); 120 121 122/* Utility functions. */ 123 124/* EVP_AEAD_key_length returns the length, in bytes, of the keys used by 125 * |aead|. */ 126OPENSSL_EXPORT size_t EVP_AEAD_key_length(const EVP_AEAD *aead); 127 128/* EVP_AEAD_nonce_length returns the length, in bytes, of the per-message nonce 129 * for |aead|. */ 130OPENSSL_EXPORT size_t EVP_AEAD_nonce_length(const EVP_AEAD *aead); 131 132/* EVP_AEAD_max_overhead returns the maximum number of additional bytes added 133 * by the act of sealing data with |aead|. */ 134OPENSSL_EXPORT size_t EVP_AEAD_max_overhead(const EVP_AEAD *aead); 135 136/* EVP_AEAD_max_tag_len returns the maximum tag length when using |aead|. This 137 * is the largest value that can be passed as |tag_len| to 138 * |EVP_AEAD_CTX_init|. */ 139OPENSSL_EXPORT size_t EVP_AEAD_max_tag_len(const EVP_AEAD *aead); 140 141 142/* AEAD operations. */ 143 144/* An EVP_AEAD_CTX represents an AEAD algorithm configured with a specific key 145 * and message-independent IV. */ 146typedef struct evp_aead_ctx_st { 147 const EVP_AEAD *aead; 148 /* aead_state is an opaque pointer to whatever state the AEAD needs to 149 * maintain. */ 150 void *aead_state; 151} EVP_AEAD_CTX; 152 153/* EVP_AEAD_MAX_KEY_LENGTH contains the maximum key length used by 154 * any AEAD defined in this header. */ 155#define EVP_AEAD_MAX_KEY_LENGTH 80 156 157/* EVP_AEAD_MAX_NONCE_LENGTH contains the maximum nonce length used by 158 * any AEAD defined in this header. */ 159#define EVP_AEAD_MAX_NONCE_LENGTH 16 160 161/* EVP_AEAD_MAX_OVERHEAD contains the maximum overhead used by any AEAD 162 * defined in this header. */ 163#define EVP_AEAD_MAX_OVERHEAD 64 164 165/* EVP_AEAD_DEFAULT_TAG_LENGTH is a magic value that can be passed to 166 * EVP_AEAD_CTX_init to indicate that the default tag length for an AEAD should 167 * be used. */ 168#define EVP_AEAD_DEFAULT_TAG_LENGTH 0 169 170/* EVP_AEAD_CTX_zero sets an uninitialized |ctx| to the zero state. It must be 171 * initialized with |EVP_AEAD_CTX_init| before use. It is safe, but not 172 * necessary, to call |EVP_AEAD_CTX_cleanup| in this state. This may be used for 173 * more uniform cleanup of |EVP_AEAD_CTX|. */ 174OPENSSL_EXPORT void EVP_AEAD_CTX_zero(EVP_AEAD_CTX *ctx); 175 176/* EVP_AEAD_CTX_init initializes |ctx| for the given AEAD algorithm. The |impl| 177 * argument is ignored and should be NULL. Authentication tags may be truncated 178 * by passing a size as |tag_len|. A |tag_len| of zero indicates the default 179 * tag length and this is defined as EVP_AEAD_DEFAULT_TAG_LENGTH for 180 * readability. 181 * 182 * Returns 1 on success. Otherwise returns 0 and pushes to the error stack. In 183 * the error case, you do not need to call |EVP_AEAD_CTX_cleanup|, but it's 184 * harmless to do so. */ 185OPENSSL_EXPORT int EVP_AEAD_CTX_init(EVP_AEAD_CTX *ctx, const EVP_AEAD *aead, 186 const uint8_t *key, size_t key_len, 187 size_t tag_len, ENGINE *impl); 188 189/* EVP_AEAD_CTX_cleanup frees any data allocated by |ctx|. It is a no-op to 190 * call |EVP_AEAD_CTX_cleanup| on a |EVP_AEAD_CTX| that has been |memset| to 191 * all zeros. */ 192OPENSSL_EXPORT void EVP_AEAD_CTX_cleanup(EVP_AEAD_CTX *ctx); 193 194/* EVP_AEAD_CTX_seal encrypts and authenticates |in_len| bytes from |in| and 195 * authenticates |ad_len| bytes from |ad| and writes the result to |out|. It 196 * returns one on success and zero otherwise. 197 * 198 * This function may be called (with the same |EVP_AEAD_CTX|) concurrently with 199 * itself or |EVP_AEAD_CTX_open|. 200 * 201 * At most |max_out_len| bytes are written to |out| and, in order to ensure 202 * success, |max_out_len| should be |in_len| plus the result of 203 * |EVP_AEAD_max_overhead|. On successful return, |*out_len| is set to the 204 * actual number of bytes written. 205 * 206 * The length of |nonce|, |nonce_len|, must be equal to the result of 207 * |EVP_AEAD_nonce_length| for this AEAD. 208 * 209 * |EVP_AEAD_CTX_seal| never results in a partial output. If |max_out_len| is 210 * insufficient, zero will be returned. (In this case, |*out_len| is set to 211 * zero.) 212 * 213 * If |in| and |out| alias then |out| must be == |in|. */ 214OPENSSL_EXPORT int EVP_AEAD_CTX_seal(const EVP_AEAD_CTX *ctx, uint8_t *out, 215 size_t *out_len, size_t max_out_len, 216 const uint8_t *nonce, size_t nonce_len, 217 const uint8_t *in, size_t in_len, 218 const uint8_t *ad, size_t ad_len); 219 220/* EVP_AEAD_CTX_open authenticates |in_len| bytes from |in| and |ad_len| bytes 221 * from |ad| and decrypts at most |in_len| bytes into |out|. It returns one on 222 * success and zero otherwise. 223 * 224 * This function may be called (with the same |EVP_AEAD_CTX|) concurrently with 225 * itself or |EVP_AEAD_CTX_seal|. 226 * 227 * At most |in_len| bytes are written to |out|. In order to ensure success, 228 * |max_out_len| should be at least |in_len|. On successful return, |*out_len| 229 * is set to the the actual number of bytes written. 230 * 231 * The length of |nonce|, |nonce_len|, must be equal to the result of 232 * |EVP_AEAD_nonce_length| for this AEAD. 233 * 234 * |EVP_AEAD_CTX_open| never results in a partial output. If |max_out_len| is 235 * insufficient, zero will be returned. (In this case, |*out_len| is set to 236 * zero.) 237 * 238 * If |in| and |out| alias then |out| must be == |in|. */ 239OPENSSL_EXPORT int EVP_AEAD_CTX_open(const EVP_AEAD_CTX *ctx, uint8_t *out, 240 size_t *out_len, size_t max_out_len, 241 const uint8_t *nonce, size_t nonce_len, 242 const uint8_t *in, size_t in_len, 243 const uint8_t *ad, size_t ad_len); 244 245/* EVP_AEAD_CTX_aead returns the underlying AEAD for |ctx|, or NULL if one has 246 * not been set. */ 247OPENSSL_EXPORT const EVP_AEAD *EVP_AEAD_CTX_aead(const EVP_AEAD_CTX *ctx); 248 249 250/* TLS-specific AEAD algorithms. 251 * 252 * These AEAD primitives do not meet the definition of generic AEADs. They are 253 * all specific to TLS and should not be used outside of that context. They must 254 * be initialized with |EVP_AEAD_CTX_init_with_direction|, are stateful, and may 255 * not be used concurrently. Any nonces are used as IVs, so they must be 256 * unpredictable. They only accept an |ad| parameter of length 11 (the standard 257 * TLS one with length omitted). */ 258 259OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_128_cbc_sha1_tls(void); 260OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_128_cbc_sha1_tls_implicit_iv(void); 261OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_128_cbc_sha256_tls(void); 262 263OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_256_cbc_sha1_tls(void); 264OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_256_cbc_sha1_tls_implicit_iv(void); 265OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_256_cbc_sha256_tls(void); 266OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_256_cbc_sha384_tls(void); 267 268OPENSSL_EXPORT const EVP_AEAD *EVP_aead_des_ede3_cbc_sha1_tls(void); 269OPENSSL_EXPORT const EVP_AEAD *EVP_aead_des_ede3_cbc_sha1_tls_implicit_iv(void); 270 271OPENSSL_EXPORT const EVP_AEAD *EVP_aead_null_sha1_tls(void); 272 273 274/* SSLv3-specific AEAD algorithms. 275 * 276 * These AEAD primitives do not meet the definition of generic AEADs. They are 277 * all specific to SSLv3 and should not be used outside of that context. They 278 * must be initialized with |EVP_AEAD_CTX_init_with_direction|, are stateful, 279 * and may not be used concurrently. They only accept an |ad| parameter of 280 * length 9 (the standard TLS one with length and version omitted). */ 281 282OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_128_cbc_sha1_ssl3(void); 283OPENSSL_EXPORT const EVP_AEAD *EVP_aead_aes_256_cbc_sha1_ssl3(void); 284OPENSSL_EXPORT const EVP_AEAD *EVP_aead_des_ede3_cbc_sha1_ssl3(void); 285OPENSSL_EXPORT const EVP_AEAD *EVP_aead_null_sha1_ssl3(void); 286 287 288/* Obscure functions. */ 289 290/* evp_aead_direction_t denotes the direction of an AEAD operation. */ 291enum evp_aead_direction_t { 292 evp_aead_open, 293 evp_aead_seal, 294}; 295 296/* EVP_AEAD_CTX_init_with_direction calls |EVP_AEAD_CTX_init| for normal 297 * AEADs. For TLS-specific and SSL3-specific AEADs, it initializes |ctx| for a 298 * given direction. */ 299OPENSSL_EXPORT int EVP_AEAD_CTX_init_with_direction( 300 EVP_AEAD_CTX *ctx, const EVP_AEAD *aead, const uint8_t *key, size_t key_len, 301 size_t tag_len, enum evp_aead_direction_t dir); 302 303/* EVP_AEAD_CTX_get_iv sets |*out_len| to the length of the IV for |ctx| and 304 * sets |*out_iv| to point to that many bytes of the current IV. This is only 305 * meaningful for AEADs with implicit IVs (i.e. CBC mode in SSLv3 and TLS 1.0). 306 * 307 * It returns one on success or zero on error. */ 308OPENSSL_EXPORT int EVP_AEAD_CTX_get_iv(const EVP_AEAD_CTX *ctx, 309 const uint8_t **out_iv, size_t *out_len); 310 311 312#if defined(__cplusplus) 313} /* extern C */ 314 315#if !defined(BORINGSSL_NO_CXX) 316extern "C++" { 317 318namespace bssl { 319 320using ScopedEVP_AEAD_CTX = 321 internal::StackAllocated<EVP_AEAD_CTX, void, EVP_AEAD_CTX_zero, 322 EVP_AEAD_CTX_cleanup>; 323 324} // namespace bssl 325 326} // extern C++ 327#endif 328 329#endif 330 331#endif /* OPENSSL_HEADER_AEAD_H */ 332