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 34 #if !defined(MBEDTLS_CONFIG_FILE) 35 #include "mbedtls/config.h" 36 #else 37 #include MBEDTLS_CONFIG_FILE 38 #endif 39 40 #include "mbedtls/cipher.h" 41 42 #include <stdint.h> 43 44 #define MBEDTLS_GCM_ENCRYPT 1 45 #define MBEDTLS_GCM_DECRYPT 0 46 47 #define MBEDTLS_ERR_GCM_AUTH_FAILED -0x0012 /**< Authenticated decryption failed. */ 48 49 /* MBEDTLS_ERR_GCM_HW_ACCEL_FAILED is deprecated and should not be used. */ 50 #define MBEDTLS_ERR_GCM_HW_ACCEL_FAILED -0x0013 /**< GCM hardware accelerator failed. */ 51 52 #define MBEDTLS_ERR_GCM_BAD_INPUT -0x0014 /**< Bad input parameters to function. */ 53 54 #ifdef __cplusplus 55 extern "C" { 56 #endif 57 58 #if !defined(MBEDTLS_GCM_ALT) 59 60 /** 61 * \brief The GCM context structure. 62 */ 63 typedef struct mbedtls_gcm_context 64 { 65 mbedtls_cipher_context_t cipher_ctx; /*!< The cipher context used. */ 66 uint64_t HL[16]; /*!< Precalculated HTable low. */ 67 uint64_t HH[16]; /*!< Precalculated HTable high. */ 68 uint64_t len; /*!< The total length of the encrypted data. */ 69 uint64_t add_len; /*!< The total length of the additional data. */ 70 unsigned char base_ectr[16]; /*!< The first ECTR for tag. */ 71 unsigned char y[16]; /*!< The Y working value. */ 72 unsigned char buf[16]; /*!< The buf working value. */ 73 int mode; /*!< The operation to perform: 74 #MBEDTLS_GCM_ENCRYPT or 75 #MBEDTLS_GCM_DECRYPT. */ 76 } 77 mbedtls_gcm_context; 78 79 #else /* !MBEDTLS_GCM_ALT */ 80 #include "gcm_alt.h" 81 #endif /* !MBEDTLS_GCM_ALT */ 82 83 /** 84 * \brief This function initializes the specified GCM context, 85 * to make references valid, and prepares the context 86 * for mbedtls_gcm_setkey() or mbedtls_gcm_free(). 87 * 88 * The function does not bind the GCM context to a particular 89 * cipher, nor set the key. For this purpose, use 90 * mbedtls_gcm_setkey(). 91 * 92 * \param ctx The GCM context to initialize. This must not be \c NULL. 93 */ 94 void mbedtls_gcm_init( mbedtls_gcm_context *ctx ); 95 96 /** 97 * \brief This function associates a GCM context with a 98 * cipher algorithm and a key. 99 * 100 * \param ctx The GCM context. This must be initialized. 101 * \param cipher The 128-bit block cipher to use. 102 * \param key The encryption key. This must be a readable buffer of at 103 * least \p keybits bits. 104 * \param keybits The key size in bits. Valid options are: 105 * <ul><li>128 bits</li> 106 * <li>192 bits</li> 107 * <li>256 bits</li></ul> 108 * 109 * \return \c 0 on success. 110 * \return A cipher-specific error code on failure. 111 */ 112 int mbedtls_gcm_setkey( mbedtls_gcm_context *ctx, 113 mbedtls_cipher_id_t cipher, 114 const unsigned char *key, 115 unsigned int keybits ); 116 117 /** 118 * \brief This function performs GCM encryption or decryption of a buffer. 119 * 120 * \note For encryption, the output buffer can be the same as the 121 * input buffer. For decryption, the output buffer cannot be 122 * the same as input buffer. If the buffers overlap, the output 123 * buffer must trail at least 8 Bytes behind the input buffer. 124 * 125 * \warning When this function performs a decryption, it outputs the 126 * authentication tag and does not verify that the data is 127 * authentic. You should use this function to perform encryption 128 * only. For decryption, use mbedtls_gcm_auth_decrypt() instead. 129 * 130 * \param ctx The GCM context to use for encryption or decryption. This 131 * must be initialized. 132 * \param mode The operation to perform: 133 * - #MBEDTLS_GCM_ENCRYPT to perform authenticated encryption. 134 * The ciphertext is written to \p output and the 135 * authentication tag is written to \p tag. 136 * - #MBEDTLS_GCM_DECRYPT to perform decryption. 137 * The plaintext is written to \p output and the 138 * authentication tag is written to \p tag. 139 * Note that this mode is not recommended, because it does 140 * not verify the authenticity of the data. For this reason, 141 * you should use mbedtls_gcm_auth_decrypt() instead of 142 * calling this function in decryption mode. 143 * \param length The length of the input data, which is equal to the length 144 * of the output data. 145 * \param iv The initialization vector. This must be a readable buffer of 146 * at least \p iv_len Bytes. 147 * \param iv_len The length of the IV. 148 * \param add The buffer holding the additional data. This must be of at 149 * least that size in Bytes. 150 * \param add_len The length of the additional data. 151 * \param input The buffer holding the input data. If \p length is greater 152 * than zero, this must be a readable buffer of at least that 153 * size in Bytes. 154 * \param output The buffer for holding the output data. If \p length is greater 155 * than zero, this must be a writable buffer of at least that 156 * size in Bytes. 157 * \param tag_len The length of the tag to generate. 158 * \param tag The buffer for holding the tag. This must be a writable 159 * buffer of at least \p tag_len Bytes. 160 * 161 * \return \c 0 if the encryption or decryption was performed 162 * successfully. Note that in #MBEDTLS_GCM_DECRYPT mode, 163 * this does not indicate that the data is authentic. 164 * \return #MBEDTLS_ERR_GCM_BAD_INPUT if the lengths or pointers are 165 * not valid or a cipher-specific error code if the encryption 166 * or decryption failed. 167 */ 168 int mbedtls_gcm_crypt_and_tag( mbedtls_gcm_context *ctx, 169 int mode, 170 size_t length, 171 const unsigned char *iv, 172 size_t iv_len, 173 const unsigned char *add, 174 size_t add_len, 175 const unsigned char *input, 176 unsigned char *output, 177 size_t tag_len, 178 unsigned char *tag ); 179 180 /** 181 * \brief This function performs a GCM authenticated decryption of a 182 * buffer. 183 * 184 * \note For decryption, the output buffer cannot be the same as 185 * input buffer. If the buffers overlap, the output buffer 186 * must trail at least 8 Bytes behind the input buffer. 187 * 188 * \param ctx The GCM context. This must be initialized. 189 * \param length The length of the ciphertext to decrypt, which is also 190 * the length of the decrypted plaintext. 191 * \param iv The initialization vector. This must be a readable buffer 192 * of at least \p iv_len Bytes. 193 * \param iv_len The length of the IV. 194 * \param add The buffer holding the additional data. This must be of at 195 * least that size in Bytes. 196 * \param add_len The length of the additional data. 197 * \param tag The buffer holding the tag to verify. This must be a 198 * readable buffer of at least \p tag_len Bytes. 199 * \param tag_len The length of the tag to verify. 200 * \param input The buffer holding the ciphertext. If \p length is greater 201 * than zero, this must be a readable buffer of at least that 202 * size. 203 * \param output The buffer for holding the decrypted plaintext. If \p length 204 * is greater than zero, this must be a writable buffer of at 205 * least that size. 206 * 207 * \return \c 0 if successful and authenticated. 208 * \return #MBEDTLS_ERR_GCM_AUTH_FAILED if the tag does not match. 209 * \return #MBEDTLS_ERR_GCM_BAD_INPUT if the lengths or pointers are 210 * not valid or a cipher-specific error code if the decryption 211 * failed. 212 */ 213 int mbedtls_gcm_auth_decrypt( mbedtls_gcm_context *ctx, 214 size_t length, 215 const unsigned char *iv, 216 size_t iv_len, 217 const unsigned char *add, 218 size_t add_len, 219 const unsigned char *tag, 220 size_t tag_len, 221 const unsigned char *input, 222 unsigned char *output ); 223 224 /** 225 * \brief This function starts a GCM encryption or decryption 226 * operation. 227 * 228 * \param ctx The GCM context. This must be initialized. 229 * \param mode The operation to perform: #MBEDTLS_GCM_ENCRYPT or 230 * #MBEDTLS_GCM_DECRYPT. 231 * \param iv The initialization vector. This must be a readable buffer of 232 * at least \p iv_len Bytes. 233 * \param iv_len The length of the IV. 234 * \param add The buffer holding the additional data, or \c NULL 235 * if \p add_len is \c 0. 236 * \param add_len The length of the additional data. If \c 0, 237 * \p add may be \c NULL. 238 * 239 * \return \c 0 on success. 240 */ 241 int mbedtls_gcm_starts( mbedtls_gcm_context *ctx, 242 int mode, 243 const unsigned char *iv, 244 size_t iv_len, 245 const unsigned char *add, 246 size_t add_len ); 247 248 /** 249 * \brief This function feeds an input buffer into an ongoing GCM 250 * encryption or decryption operation. 251 * 252 * ` The function expects input to be a multiple of 16 253 * Bytes. Only the last call before calling 254 * mbedtls_gcm_finish() can be less than 16 Bytes. 255 * 256 * \note For decryption, the output buffer cannot be the same as 257 * input buffer. If the buffers overlap, the output buffer 258 * must trail at least 8 Bytes behind the input buffer. 259 * 260 * \param ctx The GCM context. This must be initialized. 261 * \param length The length of the input data. This must be a multiple of 262 * 16 except in the last call before mbedtls_gcm_finish(). 263 * \param input The buffer holding the input data. If \p length is greater 264 * than zero, this must be a readable buffer of at least that 265 * size in Bytes. 266 * \param output The buffer for holding the output data. If \p length is 267 * greater than zero, this must be a writable buffer of at 268 * least that size in Bytes. 269 * 270 * \return \c 0 on success. 271 * \return #MBEDTLS_ERR_GCM_BAD_INPUT on failure. 272 */ 273 int mbedtls_gcm_update( mbedtls_gcm_context *ctx, 274 size_t length, 275 const unsigned char *input, 276 unsigned char *output ); 277 278 /** 279 * \brief This function finishes the GCM operation and generates 280 * the authentication tag. 281 * 282 * It wraps up the GCM stream, and generates the 283 * tag. The tag can have a maximum length of 16 Bytes. 284 * 285 * \param ctx The GCM context. This must be initialized. 286 * \param tag The buffer for holding the tag. This must be a writable 287 * buffer of at least \p tag_len Bytes. 288 * \param tag_len The length of the tag to generate. This must be at least 289 * four. 290 * 291 * \return \c 0 on success. 292 * \return #MBEDTLS_ERR_GCM_BAD_INPUT on failure. 293 */ 294 int mbedtls_gcm_finish( mbedtls_gcm_context *ctx, 295 unsigned char *tag, 296 size_t tag_len ); 297 298 /** 299 * \brief This function clears a GCM context and the underlying 300 * cipher sub-context. 301 * 302 * \param ctx The GCM context to clear. If this is \c NULL, the call has 303 * no effect. Otherwise, this must be initialized. 304 */ 305 void mbedtls_gcm_free( mbedtls_gcm_context *ctx ); 306 307 #if defined(MBEDTLS_SELF_TEST) 308 309 /** 310 * \brief The GCM checkup routine. 311 * 312 * \return \c 0 on success. 313 * \return \c 1 on failure. 314 */ 315 int mbedtls_gcm_self_test( int verbose ); 316 317 #endif /* MBEDTLS_SELF_TEST */ 318 319 #ifdef __cplusplus 320 } 321 #endif 322 323 324 #endif /* gcm.h */ 325