1 /** 2 * \file gcm.h 3 * 4 * \brief This file contains GCM definitions and functions. 5 * 6 * The Galois/Counter Mode (GCM) for 128-bit block ciphers is defined 7 * in <em>D. McGrew, J. Viega, The Galois/Counter Mode of Operation 8 * (GCM), Natl. Inst. Stand. Technol.</em> 9 * 10 * For more information on GCM, see <em>NIST SP 800-38D: Recommendation for 11 * Block Cipher Modes of Operation: Galois/Counter Mode (GCM) and GMAC</em>. 12 * 13 */ 14 /* 15 * Copyright The Mbed TLS Contributors 16 * SPDX-License-Identifier: Apache-2.0 17 * 18 * Licensed under the Apache License, Version 2.0 (the "License"); you may 19 * not use this file except in compliance with the License. 20 * You may obtain a copy of the License at 21 * 22 * http://www.apache.org/licenses/LICENSE-2.0 23 * 24 * Unless required by applicable law or agreed to in writing, software 25 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT 26 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 27 * See the License for the specific language governing permissions and 28 * limitations under the License. 29 */ 30 31 #ifndef MBEDTLS_GCM_H 32 #define MBEDTLS_GCM_H 33 #include "mbedtls/private_access.h" 34 35 #include "mbedtls/build_info.h" 36 37 #include "mbedtls/cipher.h" 38 39 #include <stdint.h> 40 41 #define MBEDTLS_GCM_ENCRYPT 1 42 #define MBEDTLS_GCM_DECRYPT 0 43 44 /** Authenticated decryption failed. */ 45 #define MBEDTLS_ERR_GCM_AUTH_FAILED -0x0012 46 /** Bad input parameters to function. */ 47 #define MBEDTLS_ERR_GCM_BAD_INPUT -0x0014 48 /** An output buffer is too small. */ 49 #define MBEDTLS_ERR_GCM_BUFFER_TOO_SMALL -0x0016 50 51 #ifdef __cplusplus 52 extern "C" { 53 #endif 54 55 #if !defined(MBEDTLS_GCM_ALT) 56 57 /** 58 * \brief The GCM context structure. 59 */ 60 typedef struct mbedtls_gcm_context { 61 mbedtls_cipher_context_t MBEDTLS_PRIVATE(cipher_ctx); /*!< The cipher context used. */ 62 uint64_t MBEDTLS_PRIVATE(HL)[16]; /*!< Precalculated HTable low. */ 63 uint64_t MBEDTLS_PRIVATE(HH)[16]; /*!< Precalculated HTable high. */ 64 uint64_t MBEDTLS_PRIVATE(len); /*!< The total length of the encrypted data. */ 65 uint64_t MBEDTLS_PRIVATE(add_len); /*!< The total length of the additional data. */ 66 unsigned char MBEDTLS_PRIVATE(base_ectr)[16]; /*!< The first ECTR for tag. */ 67 unsigned char MBEDTLS_PRIVATE(y)[16]; /*!< The Y working value. */ 68 unsigned char MBEDTLS_PRIVATE(buf)[16]; /*!< The buf working value. */ 69 int MBEDTLS_PRIVATE(mode); /*!< The operation to perform: 70 #MBEDTLS_GCM_ENCRYPT or 71 #MBEDTLS_GCM_DECRYPT. */ 72 } 73 mbedtls_gcm_context; 74 75 #else /* !MBEDTLS_GCM_ALT */ 76 #include "gcm_alt.h" 77 #endif /* !MBEDTLS_GCM_ALT */ 78 79 /** 80 * \brief This function initializes the specified GCM context, 81 * to make references valid, and prepares the context 82 * for mbedtls_gcm_setkey() or mbedtls_gcm_free(). 83 * 84 * The function does not bind the GCM context to a particular 85 * cipher, nor set the key. For this purpose, use 86 * mbedtls_gcm_setkey(). 87 * 88 * \param ctx The GCM context to initialize. This must not be \c NULL. 89 */ 90 void mbedtls_gcm_init(mbedtls_gcm_context *ctx); 91 92 /** 93 * \brief This function associates a GCM context with a 94 * cipher algorithm and a key. 95 * 96 * \param ctx The GCM context. This must be initialized. 97 * \param cipher The 128-bit block cipher to use. 98 * \param key The encryption key. This must be a readable buffer of at 99 * least \p keybits bits. 100 * \param keybits The key size in bits. Valid options are: 101 * <ul><li>128 bits</li> 102 * <li>192 bits</li> 103 * <li>256 bits</li></ul> 104 * 105 * \return \c 0 on success. 106 * \return A cipher-specific error code on failure. 107 */ 108 int mbedtls_gcm_setkey(mbedtls_gcm_context *ctx, 109 mbedtls_cipher_id_t cipher, 110 const unsigned char *key, 111 unsigned int keybits); 112 113 /** 114 * \brief This function performs GCM encryption or decryption of a buffer. 115 * 116 * \note For encryption, the output buffer can be the same as the 117 * input buffer. For decryption, the output buffer cannot be 118 * the same as input buffer. If the buffers overlap, the output 119 * buffer must trail at least 8 Bytes behind the input buffer. 120 * 121 * \warning When this function performs a decryption, it outputs the 122 * authentication tag and does not verify that the data is 123 * authentic. You should use this function to perform encryption 124 * only. For decryption, use mbedtls_gcm_auth_decrypt() instead. 125 * 126 * \param ctx The GCM context to use for encryption or decryption. This 127 * must be initialized. 128 * \param mode The operation to perform: 129 * - #MBEDTLS_GCM_ENCRYPT to perform authenticated encryption. 130 * The ciphertext is written to \p output and the 131 * authentication tag is written to \p tag. 132 * - #MBEDTLS_GCM_DECRYPT to perform decryption. 133 * The plaintext is written to \p output and the 134 * authentication tag is written to \p tag. 135 * Note that this mode is not recommended, because it does 136 * not verify the authenticity of the data. For this reason, 137 * you should use mbedtls_gcm_auth_decrypt() instead of 138 * calling this function in decryption mode. 139 * \param length The length of the input data, which is equal to the length 140 * of the output data. 141 * \param iv The initialization vector. This must be a readable buffer of 142 * at least \p iv_len Bytes. 143 * \param iv_len The length of the IV. 144 * \param add The buffer holding the additional data. This must be of at 145 * least that size in Bytes. 146 * \param add_len The length of the additional data. 147 * \param input The buffer holding the input data. If \p length is greater 148 * than zero, this must be a readable buffer of at least that 149 * size in Bytes. 150 * \param output The buffer for holding the output data. If \p length is greater 151 * than zero, this must be a writable buffer of at least that 152 * size in Bytes. 153 * \param tag_len The length of the tag to generate. 154 * \param tag The buffer for holding the tag. This must be a writable 155 * buffer of at least \p tag_len Bytes. 156 * 157 * \return \c 0 if the encryption or decryption was performed 158 * successfully. Note that in #MBEDTLS_GCM_DECRYPT mode, 159 * this does not indicate that the data is authentic. 160 * \return #MBEDTLS_ERR_GCM_BAD_INPUT if the lengths or pointers are 161 * not valid or a cipher-specific error code if the encryption 162 * or decryption failed. 163 */ 164 int mbedtls_gcm_crypt_and_tag(mbedtls_gcm_context *ctx, 165 int mode, 166 size_t length, 167 const unsigned char *iv, 168 size_t iv_len, 169 const unsigned char *add, 170 size_t add_len, 171 const unsigned char *input, 172 unsigned char *output, 173 size_t tag_len, 174 unsigned char *tag); 175 176 /** 177 * \brief This function performs a GCM authenticated decryption of a 178 * buffer. 179 * 180 * \note For decryption, the output buffer cannot be the same as 181 * input buffer. If the buffers overlap, the output buffer 182 * must trail at least 8 Bytes behind the input buffer. 183 * 184 * \param ctx The GCM context. This must be initialized. 185 * \param length The length of the ciphertext to decrypt, which is also 186 * the length of the decrypted plaintext. 187 * \param iv The initialization vector. This must be a readable buffer 188 * of at least \p iv_len Bytes. 189 * \param iv_len The length of the IV. 190 * \param add The buffer holding the additional data. This must be of at 191 * least that size in Bytes. 192 * \param add_len The length of the additional data. 193 * \param tag The buffer holding the tag to verify. This must be a 194 * readable buffer of at least \p tag_len Bytes. 195 * \param tag_len The length of the tag to verify. 196 * \param input The buffer holding the ciphertext. If \p length is greater 197 * than zero, this must be a readable buffer of at least that 198 * size. 199 * \param output The buffer for holding the decrypted plaintext. If \p length 200 * is greater than zero, this must be a writable buffer of at 201 * least that size. 202 * 203 * \return \c 0 if successful and authenticated. 204 * \return #MBEDTLS_ERR_GCM_AUTH_FAILED if the tag does not match. 205 * \return #MBEDTLS_ERR_GCM_BAD_INPUT if the lengths or pointers are 206 * not valid or a cipher-specific error code if the decryption 207 * failed. 208 */ 209 int mbedtls_gcm_auth_decrypt(mbedtls_gcm_context *ctx, 210 size_t length, 211 const unsigned char *iv, 212 size_t iv_len, 213 const unsigned char *add, 214 size_t add_len, 215 const unsigned char *tag, 216 size_t tag_len, 217 const unsigned char *input, 218 unsigned char *output); 219 220 /** 221 * \brief This function starts a GCM encryption or decryption 222 * operation. 223 * 224 * \param ctx The GCM context. This must be initialized. 225 * \param mode The operation to perform: #MBEDTLS_GCM_ENCRYPT or 226 * #MBEDTLS_GCM_DECRYPT. 227 * \param iv The initialization vector. This must be a readable buffer of 228 * at least \p iv_len Bytes. 229 * \param iv_len The length of the IV. 230 * 231 * \return \c 0 on success. 232 */ 233 int mbedtls_gcm_starts(mbedtls_gcm_context *ctx, 234 int mode, 235 const unsigned char *iv, 236 size_t iv_len); 237 238 /** 239 * \brief This function feeds an input buffer as associated data 240 * (authenticated but not encrypted data) in a GCM 241 * encryption or decryption operation. 242 * 243 * Call this function after mbedtls_gcm_starts() to pass 244 * the associated data. If the associated data is empty, 245 * you do not need to call this function. You may not 246 * call this function after calling mbedtls_cipher_update(). 247 * 248 * \param ctx The GCM context. This must have been started with 249 * mbedtls_gcm_starts() and must not have yet received 250 * any input with mbedtls_gcm_update(). 251 * \param add The buffer holding the additional data, or \c NULL 252 * if \p add_len is \c 0. 253 * \param add_len The length of the additional data. If \c 0, 254 * \p add may be \c NULL. 255 * 256 * \return \c 0 on success. 257 */ 258 int mbedtls_gcm_update_ad(mbedtls_gcm_context *ctx, 259 const unsigned char *add, 260 size_t add_len); 261 262 /** 263 * \brief This function feeds an input buffer into an ongoing GCM 264 * encryption or decryption operation. 265 * 266 * You may call this function zero, one or more times 267 * to pass successive parts of the input: the plaintext to 268 * encrypt, or the ciphertext (not including the tag) to 269 * decrypt. After the last part of the input, call 270 * mbedtls_gcm_finish(). 271 * 272 * This function may produce output in one of the following 273 * ways: 274 * - Immediate output: the output length is always equal 275 * to the input length. 276 * - Buffered output: the output consists of a whole number 277 * of 16-byte blocks. If the total input length so far 278 * (not including associated data) is 16 \* *B* + *A* 279 * with *A* < 16 then the total output length is 16 \* *B*. 280 * 281 * In particular: 282 * - It is always correct to call this function with 283 * \p output_size >= \p input_length + 15. 284 * - If \p input_length is a multiple of 16 for all the calls 285 * to this function during an operation, then it is 286 * correct to use \p output_size = \p input_length. 287 * 288 * \note For decryption, the output buffer cannot be the same as 289 * input buffer. If the buffers overlap, the output buffer 290 * must trail at least 8 Bytes behind the input buffer. 291 * 292 * \param ctx The GCM context. This must be initialized. 293 * \param input The buffer holding the input data. If \p input_length 294 * is greater than zero, this must be a readable buffer 295 * of at least \p input_length bytes. 296 * \param input_length The length of the input data in bytes. 297 * \param output The buffer for the output data. If \p output_size 298 * is greater than zero, this must be a writable buffer of 299 * of at least \p output_size bytes. 300 * \param output_size The size of the output buffer in bytes. 301 * See the function description regarding the output size. 302 * \param output_length On success, \p *output_length contains the actual 303 * length of the output written in \p output. 304 * On failure, the content of \p *output_length is 305 * unspecified. 306 * 307 * \return \c 0 on success. 308 * \return #MBEDTLS_ERR_GCM_BAD_INPUT on failure: 309 * total input length too long, 310 * unsupported input/output buffer overlap detected, 311 * or \p output_size too small. 312 */ 313 int mbedtls_gcm_update(mbedtls_gcm_context *ctx, 314 const unsigned char *input, size_t input_length, 315 unsigned char *output, size_t output_size, 316 size_t *output_length); 317 318 /** 319 * \brief This function finishes the GCM operation and generates 320 * the authentication tag. 321 * 322 * It wraps up the GCM stream, and generates the 323 * tag. The tag can have a maximum length of 16 Bytes. 324 * 325 * \param ctx The GCM context. This must be initialized. 326 * \param tag The buffer for holding the tag. This must be a writable 327 * buffer of at least \p tag_len Bytes. 328 * \param tag_len The length of the tag to generate. This must be at least 329 * four. 330 * \param output The buffer for the final output. 331 * If \p output_size is nonzero, this must be a writable 332 * buffer of at least \p output_size bytes. 333 * \param output_size The size of the \p output buffer in bytes. 334 * This must be large enough for the output that 335 * mbedtls_gcm_update() has not produced. In particular: 336 * - If mbedtls_gcm_update() produces immediate output, 337 * or if the total input size is a multiple of \c 16, 338 * then mbedtls_gcm_finish() never produces any output, 339 * so \p output_size can be \c 0. 340 * - \p output_size never needs to be more than \c 15. 341 * \param output_length On success, \p *output_length contains the actual 342 * length of the output written in \p output. 343 * On failure, the content of \p *output_length is 344 * unspecified. 345 * 346 * \return \c 0 on success. 347 * \return #MBEDTLS_ERR_GCM_BAD_INPUT on failure: 348 * invalid value of \p tag_len, 349 * or \p output_size too small. 350 */ 351 int mbedtls_gcm_finish(mbedtls_gcm_context *ctx, 352 unsigned char *output, size_t output_size, 353 size_t *output_length, 354 unsigned char *tag, size_t tag_len); 355 356 /** 357 * \brief This function clears a GCM context and the underlying 358 * cipher sub-context. 359 * 360 * \param ctx The GCM context to clear. If this is \c NULL, the call has 361 * no effect. Otherwise, this must be initialized. 362 */ 363 void mbedtls_gcm_free(mbedtls_gcm_context *ctx); 364 365 #if defined(MBEDTLS_SELF_TEST) 366 367 /** 368 * \brief The GCM checkup routine. 369 * 370 * \return \c 0 on success. 371 * \return \c 1 on failure. 372 */ 373 int mbedtls_gcm_self_test(int verbose); 374 375 #endif /* MBEDTLS_SELF_TEST */ 376 377 #ifdef __cplusplus 378 } 379 #endif 380 381 382 #endif /* gcm.h */ 383