1 /** 2 * \file chachapoly.h 3 * 4 * \brief This file contains the AEAD-ChaCha20-Poly1305 definitions and 5 * functions. 6 * 7 * ChaCha20-Poly1305 is an algorithm for Authenticated Encryption 8 * with Associated Data (AEAD) that can be used to encrypt and 9 * authenticate data. It is based on ChaCha20 and Poly1305 by Daniel 10 * Bernstein and was standardized in RFC 7539. 11 * 12 * \author Daniel King <damaki.gh@gmail.com> 13 */ 14 15 /* 16 * Copyright The Mbed TLS Contributors 17 * SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later 18 * 19 * This file is provided under the Apache License 2.0, or the 20 * GNU General Public License v2.0 or later. 21 * 22 * ********** 23 * Apache License 2.0: 24 * 25 * Licensed under the Apache License, Version 2.0 (the "License"); you may 26 * not use this file except in compliance with the License. 27 * You may obtain a copy of the License at 28 * 29 * http://www.apache.org/licenses/LICENSE-2.0 30 * 31 * Unless required by applicable law or agreed to in writing, software 32 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT 33 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 34 * See the License for the specific language governing permissions and 35 * limitations under the License. 36 * 37 * ********** 38 * 39 * ********** 40 * GNU General Public License v2.0 or later: 41 * 42 * This program is free software; you can redistribute it and/or modify 43 * it under the terms of the GNU General Public License as published by 44 * the Free Software Foundation; either version 2 of the License, or 45 * (at your option) any later version. 46 * 47 * This program is distributed in the hope that it will be useful, 48 * but WITHOUT ANY WARRANTY; without even the implied warranty of 49 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 50 * GNU General Public License for more details. 51 * 52 * You should have received a copy of the GNU General Public License along 53 * with this program; if not, write to the Free Software Foundation, Inc., 54 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. 55 * 56 * ********** 57 */ 58 59 #ifndef MBEDTLS_CHACHAPOLY_H 60 #define MBEDTLS_CHACHAPOLY_H 61 62 #if !defined(MBEDTLS_CONFIG_FILE) 63 #include "config.h" 64 #else 65 #include MBEDTLS_CONFIG_FILE 66 #endif 67 68 /* for shared error codes */ 69 #include "poly1305.h" 70 71 #define MBEDTLS_ERR_CHACHAPOLY_BAD_STATE -0x0054 /**< The requested operation is not permitted in the current state. */ 72 #define MBEDTLS_ERR_CHACHAPOLY_AUTH_FAILED -0x0056 /**< Authenticated decryption failed: data was not authentic. */ 73 74 #ifdef __cplusplus 75 extern "C" { 76 #endif 77 78 typedef enum 79 { 80 MBEDTLS_CHACHAPOLY_ENCRYPT, /**< The mode value for performing encryption. */ 81 MBEDTLS_CHACHAPOLY_DECRYPT /**< The mode value for performing decryption. */ 82 } 83 mbedtls_chachapoly_mode_t; 84 85 #if !defined(MBEDTLS_CHACHAPOLY_ALT) 86 87 #include "chacha20.h" 88 89 typedef struct mbedtls_chachapoly_context 90 { 91 mbedtls_chacha20_context chacha20_ctx; /**< The ChaCha20 context. */ 92 mbedtls_poly1305_context poly1305_ctx; /**< The Poly1305 context. */ 93 uint64_t aad_len; /**< The length (bytes) of the Additional Authenticated Data. */ 94 uint64_t ciphertext_len; /**< The length (bytes) of the ciphertext. */ 95 int state; /**< The current state of the context. */ 96 mbedtls_chachapoly_mode_t mode; /**< Cipher mode (encrypt or decrypt). */ 97 } 98 mbedtls_chachapoly_context; 99 100 #else /* !MBEDTLS_CHACHAPOLY_ALT */ 101 #include "chachapoly_alt.h" 102 #endif /* !MBEDTLS_CHACHAPOLY_ALT */ 103 104 /** 105 * \brief This function initializes the specified ChaCha20-Poly1305 context. 106 * 107 * It must be the first API called before using 108 * the context. It must be followed by a call to 109 * \c mbedtls_chachapoly_setkey() before any operation can be 110 * done, and to \c mbedtls_chachapoly_free() once all 111 * operations with that context have been finished. 112 * 113 * In order to encrypt or decrypt full messages at once, for 114 * each message you should make a single call to 115 * \c mbedtls_chachapoly_crypt_and_tag() or 116 * \c mbedtls_chachapoly_auth_decrypt(). 117 * 118 * In order to encrypt messages piecewise, for each 119 * message you should make a call to 120 * \c mbedtls_chachapoly_starts(), then 0 or more calls to 121 * \c mbedtls_chachapoly_update_aad(), then 0 or more calls to 122 * \c mbedtls_chachapoly_update(), then one call to 123 * \c mbedtls_chachapoly_finish(). 124 * 125 * \warning Decryption with the piecewise API is discouraged! Always 126 * use \c mbedtls_chachapoly_auth_decrypt() when possible! 127 * 128 * If however this is not possible because the data is too 129 * large to fit in memory, you need to: 130 * 131 * - call \c mbedtls_chachapoly_starts() and (if needed) 132 * \c mbedtls_chachapoly_update_aad() as above, 133 * - call \c mbedtls_chachapoly_update() multiple times and 134 * ensure its output (the plaintext) is NOT used in any other 135 * way than placing it in temporary storage at this point, 136 * - call \c mbedtls_chachapoly_finish() to compute the 137 * authentication tag and compared it in constant time to the 138 * tag received with the ciphertext. 139 * 140 * If the tags are not equal, you must immediately discard 141 * all previous outputs of \c mbedtls_chachapoly_update(), 142 * otherwise you can now safely use the plaintext. 143 * 144 * \param ctx The ChachaPoly context to initialize. Must not be \c NULL. 145 */ 146 void mbedtls_chachapoly_init( mbedtls_chachapoly_context *ctx ); 147 148 /** 149 * \brief This function releases and clears the specified 150 * ChaCha20-Poly1305 context. 151 * 152 * \param ctx The ChachaPoly context to clear. This may be \c NULL, in which 153 * case this function is a no-op. 154 */ 155 void mbedtls_chachapoly_free( mbedtls_chachapoly_context *ctx ); 156 157 /** 158 * \brief This function sets the ChaCha20-Poly1305 159 * symmetric encryption key. 160 * 161 * \param ctx The ChaCha20-Poly1305 context to which the key should be 162 * bound. This must be initialized. 163 * \param key The \c 256 Bit (\c 32 Bytes) key. 164 * 165 * \return \c 0 on success. 166 * \return A negative error code on failure. 167 */ 168 int mbedtls_chachapoly_setkey( mbedtls_chachapoly_context *ctx, 169 const unsigned char key[32] ); 170 171 /** 172 * \brief This function starts a ChaCha20-Poly1305 encryption or 173 * decryption operation. 174 * 175 * \warning You must never use the same nonce twice with the same key. 176 * This would void any confidentiality and authenticity 177 * guarantees for the messages encrypted with the same nonce 178 * and key. 179 * 180 * \note If the context is being used for AAD only (no data to 181 * encrypt or decrypt) then \p mode can be set to any value. 182 * 183 * \warning Decryption with the piecewise API is discouraged, see the 184 * warning on \c mbedtls_chachapoly_init(). 185 * 186 * \param ctx The ChaCha20-Poly1305 context. This must be initialized 187 * and bound to a key. 188 * \param nonce The nonce/IV to use for the message. 189 * This must be a redable buffer of length \c 12 Bytes. 190 * \param mode The operation to perform: #MBEDTLS_CHACHAPOLY_ENCRYPT or 191 * #MBEDTLS_CHACHAPOLY_DECRYPT (discouraged, see warning). 192 * 193 * \return \c 0 on success. 194 * \return A negative error code on failure. 195 */ 196 int mbedtls_chachapoly_starts( mbedtls_chachapoly_context *ctx, 197 const unsigned char nonce[12], 198 mbedtls_chachapoly_mode_t mode ); 199 200 /** 201 * \brief This function feeds additional data to be authenticated 202 * into an ongoing ChaCha20-Poly1305 operation. 203 * 204 * The Additional Authenticated Data (AAD), also called 205 * Associated Data (AD) is only authenticated but not 206 * encrypted nor included in the encrypted output. It is 207 * usually transmitted separately from the ciphertext or 208 * computed locally by each party. 209 * 210 * \note This function is called before data is encrypted/decrypted. 211 * I.e. call this function to process the AAD before calling 212 * \c mbedtls_chachapoly_update(). 213 * 214 * You may call this function multiple times to process 215 * an arbitrary amount of AAD. It is permitted to call 216 * this function 0 times, if no AAD is used. 217 * 218 * This function cannot be called any more if data has 219 * been processed by \c mbedtls_chachapoly_update(), 220 * or if the context has been finished. 221 * 222 * \warning Decryption with the piecewise API is discouraged, see the 223 * warning on \c mbedtls_chachapoly_init(). 224 * 225 * \param ctx The ChaCha20-Poly1305 context. This must be initialized 226 * and bound to a key. 227 * \param aad_len The length in Bytes of the AAD. The length has no 228 * restrictions. 229 * \param aad Buffer containing the AAD. 230 * This pointer can be \c NULL if `aad_len == 0`. 231 * 232 * \return \c 0 on success. 233 * \return #MBEDTLS_ERR_POLY1305_BAD_INPUT_DATA 234 * if \p ctx or \p aad are NULL. 235 * \return #MBEDTLS_ERR_CHACHAPOLY_BAD_STATE 236 * if the operations has not been started or has been 237 * finished, or if the AAD has been finished. 238 */ 239 int mbedtls_chachapoly_update_aad( mbedtls_chachapoly_context *ctx, 240 const unsigned char *aad, 241 size_t aad_len ); 242 243 /** 244 * \brief Thus function feeds data to be encrypted or decrypted 245 * into an on-going ChaCha20-Poly1305 246 * operation. 247 * 248 * The direction (encryption or decryption) depends on the 249 * mode that was given when calling 250 * \c mbedtls_chachapoly_starts(). 251 * 252 * You may call this function multiple times to process 253 * an arbitrary amount of data. It is permitted to call 254 * this function 0 times, if no data is to be encrypted 255 * or decrypted. 256 * 257 * \warning Decryption with the piecewise API is discouraged, see the 258 * warning on \c mbedtls_chachapoly_init(). 259 * 260 * \param ctx The ChaCha20-Poly1305 context to use. This must be initialized. 261 * \param len The length (in bytes) of the data to encrypt or decrypt. 262 * \param input The buffer containing the data to encrypt or decrypt. 263 * This pointer can be \c NULL if `len == 0`. 264 * \param output The buffer to where the encrypted or decrypted data is 265 * written. This must be able to hold \p len bytes. 266 * This pointer can be \c NULL if `len == 0`. 267 * 268 * \return \c 0 on success. 269 * \return #MBEDTLS_ERR_CHACHAPOLY_BAD_STATE 270 * if the operation has not been started or has been 271 * finished. 272 * \return Another negative error code on other kinds of failure. 273 */ 274 int mbedtls_chachapoly_update( mbedtls_chachapoly_context *ctx, 275 size_t len, 276 const unsigned char *input, 277 unsigned char *output ); 278 279 /** 280 * \brief This function finished the ChaCha20-Poly1305 operation and 281 * generates the MAC (authentication tag). 282 * 283 * \param ctx The ChaCha20-Poly1305 context to use. This must be initialized. 284 * \param mac The buffer to where the 128-bit (16 bytes) MAC is written. 285 * 286 * \warning Decryption with the piecewise API is discouraged, see the 287 * warning on \c mbedtls_chachapoly_init(). 288 * 289 * \return \c 0 on success. 290 * \return #MBEDTLS_ERR_CHACHAPOLY_BAD_STATE 291 * if the operation has not been started or has been 292 * finished. 293 * \return Another negative error code on other kinds of failure. 294 */ 295 int mbedtls_chachapoly_finish( mbedtls_chachapoly_context *ctx, 296 unsigned char mac[16] ); 297 298 /** 299 * \brief This function performs a complete ChaCha20-Poly1305 300 * authenticated encryption with the previously-set key. 301 * 302 * \note Before using this function, you must set the key with 303 * \c mbedtls_chachapoly_setkey(). 304 * 305 * \warning You must never use the same nonce twice with the same key. 306 * This would void any confidentiality and authenticity 307 * guarantees for the messages encrypted with the same nonce 308 * and key. 309 * 310 * \param ctx The ChaCha20-Poly1305 context to use (holds the key). 311 * This must be initialized. 312 * \param length The length (in bytes) of the data to encrypt or decrypt. 313 * \param nonce The 96-bit (12 bytes) nonce/IV to use. 314 * \param aad The buffer containing the additional authenticated 315 * data (AAD). This pointer can be \c NULL if `aad_len == 0`. 316 * \param aad_len The length (in bytes) of the AAD data to process. 317 * \param input The buffer containing the data to encrypt or decrypt. 318 * This pointer can be \c NULL if `ilen == 0`. 319 * \param output The buffer to where the encrypted or decrypted data 320 * is written. This pointer can be \c NULL if `ilen == 0`. 321 * \param tag The buffer to where the computed 128-bit (16 bytes) MAC 322 * is written. This must not be \c NULL. 323 * 324 * \return \c 0 on success. 325 * \return A negative error code on failure. 326 */ 327 int mbedtls_chachapoly_encrypt_and_tag( mbedtls_chachapoly_context *ctx, 328 size_t length, 329 const unsigned char nonce[12], 330 const unsigned char *aad, 331 size_t aad_len, 332 const unsigned char *input, 333 unsigned char *output, 334 unsigned char tag[16] ); 335 336 /** 337 * \brief This function performs a complete ChaCha20-Poly1305 338 * authenticated decryption with the previously-set key. 339 * 340 * \note Before using this function, you must set the key with 341 * \c mbedtls_chachapoly_setkey(). 342 * 343 * \param ctx The ChaCha20-Poly1305 context to use (holds the key). 344 * \param length The length (in Bytes) of the data to decrypt. 345 * \param nonce The \c 96 Bit (\c 12 bytes) nonce/IV to use. 346 * \param aad The buffer containing the additional authenticated data (AAD). 347 * This pointer can be \c NULL if `aad_len == 0`. 348 * \param aad_len The length (in bytes) of the AAD data to process. 349 * \param tag The buffer holding the authentication tag. 350 * This must be a readable buffer of length \c 16 Bytes. 351 * \param input The buffer containing the data to decrypt. 352 * This pointer can be \c NULL if `ilen == 0`. 353 * \param output The buffer to where the decrypted data is written. 354 * This pointer can be \c NULL if `ilen == 0`. 355 * 356 * \return \c 0 on success. 357 * \return #MBEDTLS_ERR_CHACHAPOLY_AUTH_FAILED 358 * if the data was not authentic. 359 * \return Another negative error code on other kinds of failure. 360 */ 361 int mbedtls_chachapoly_auth_decrypt( mbedtls_chachapoly_context *ctx, 362 size_t length, 363 const unsigned char nonce[12], 364 const unsigned char *aad, 365 size_t aad_len, 366 const unsigned char tag[16], 367 const unsigned char *input, 368 unsigned char *output ); 369 370 #if defined(MBEDTLS_SELF_TEST) 371 /** 372 * \brief The ChaCha20-Poly1305 checkup routine. 373 * 374 * \return \c 0 on success. 375 * \return \c 1 on failure. 376 */ 377 int mbedtls_chachapoly_self_test( int verbose ); 378 #endif /* MBEDTLS_SELF_TEST */ 379 380 #ifdef __cplusplus 381 } 382 #endif 383 384 #endif /* MBEDTLS_CHACHAPOLY_H */ 385