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 /* Copyright (C) 2006-2018, Arm Limited (or its affiliates), All Rights Reserved. 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 * This file is part of Mbed TLS (https://tls.mbed.org) 31 */ 32 33 #ifndef MBEDTLS_CHACHAPOLY_H 34 #define MBEDTLS_CHACHAPOLY_H 35 36 #if !defined(MBEDTLS_CONFIG_FILE) 37 #include "config.h" 38 #else 39 #include MBEDTLS_CONFIG_FILE 40 #endif 41 42 /* for shared error codes */ 43 #include "poly1305.h" 44 45 #define MBEDTLS_ERR_CHACHAPOLY_BAD_STATE -0x0054 /**< The requested operation is not permitted in the current state. */ 46 #define MBEDTLS_ERR_CHACHAPOLY_AUTH_FAILED -0x0056 /**< Authenticated decryption failed: data was not authentic. */ 47 48 #ifdef __cplusplus 49 extern "C" { 50 #endif 51 52 typedef enum 53 { 54 MBEDTLS_CHACHAPOLY_ENCRYPT, /**< The mode value for performing encryption. */ 55 MBEDTLS_CHACHAPOLY_DECRYPT /**< The mode value for performing decryption. */ 56 } 57 mbedtls_chachapoly_mode_t; 58 59 #if !defined(MBEDTLS_CHACHAPOLY_ALT) 60 61 #include "chacha20.h" 62 63 typedef struct mbedtls_chachapoly_context 64 { 65 mbedtls_chacha20_context chacha20_ctx; /**< The ChaCha20 context. */ 66 mbedtls_poly1305_context poly1305_ctx; /**< The Poly1305 context. */ 67 uint64_t aad_len; /**< The length (bytes) of the Additional Authenticated Data. */ 68 uint64_t ciphertext_len; /**< The length (bytes) of the ciphertext. */ 69 int state; /**< The current state of the context. */ 70 mbedtls_chachapoly_mode_t mode; /**< Cipher mode (encrypt or decrypt). */ 71 } 72 mbedtls_chachapoly_context; 73 74 #else /* !MBEDTLS_CHACHAPOLY_ALT */ 75 #include "chachapoly_alt.h" 76 #endif /* !MBEDTLS_CHACHAPOLY_ALT */ 77 78 /** 79 * \brief This function initializes the specified ChaCha20-Poly1305 context. 80 * 81 * It must be the first API called before using 82 * the context. It must be followed by a call to 83 * \c mbedtls_chachapoly_setkey() before any operation can be 84 * done, and to \c mbedtls_chachapoly_free() once all 85 * operations with that context have been finished. 86 * 87 * In order to encrypt or decrypt full messages at once, for 88 * each message you should make a single call to 89 * \c mbedtls_chachapoly_crypt_and_tag() or 90 * \c mbedtls_chachapoly_auth_decrypt(). 91 * 92 * In order to encrypt messages piecewise, for each 93 * message you should make a call to 94 * \c mbedtls_chachapoly_starts(), then 0 or more calls to 95 * \c mbedtls_chachapoly_update_aad(), then 0 or more calls to 96 * \c mbedtls_chachapoly_update(), then one call to 97 * \c mbedtls_chachapoly_finish(). 98 * 99 * \warning Decryption with the piecewise API is discouraged! Always 100 * use \c mbedtls_chachapoly_auth_decrypt() when possible! 101 * 102 * If however this is not possible because the data is too 103 * large to fit in memory, you need to: 104 * 105 * - call \c mbedtls_chachapoly_starts() and (if needed) 106 * \c mbedtls_chachapoly_update_aad() as above, 107 * - call \c mbedtls_chachapoly_update() multiple times and 108 * ensure its output (the plaintext) is NOT used in any other 109 * way than placing it in temporary storage at this point, 110 * - call \c mbedtls_chachapoly_finish() to compute the 111 * authentication tag and compared it in constant time to the 112 * tag received with the ciphertext. 113 * 114 * If the tags are not equal, you must immediately discard 115 * all previous outputs of \c mbedtls_chachapoly_update(), 116 * otherwise you can now safely use the plaintext. 117 * 118 * \param ctx The ChachaPoly context to initialize. Must not be \c NULL. 119 */ 120 void mbedtls_chachapoly_init( mbedtls_chachapoly_context *ctx ); 121 122 /** 123 * \brief This function releases and clears the specified 124 * ChaCha20-Poly1305 context. 125 * 126 * \param ctx The ChachaPoly context to clear. This may be \c NULL, in which 127 * case this function is a no-op. 128 */ 129 void mbedtls_chachapoly_free( mbedtls_chachapoly_context *ctx ); 130 131 /** 132 * \brief This function sets the ChaCha20-Poly1305 133 * symmetric encryption key. 134 * 135 * \param ctx The ChaCha20-Poly1305 context to which the key should be 136 * bound. This must be initialized. 137 * \param key The \c 256 Bit (\c 32 Bytes) key. 138 * 139 * \return \c 0 on success. 140 * \return A negative error code on failure. 141 */ 142 int mbedtls_chachapoly_setkey( mbedtls_chachapoly_context *ctx, 143 const unsigned char key[32] ); 144 145 /** 146 * \brief This function starts a ChaCha20-Poly1305 encryption or 147 * decryption operation. 148 * 149 * \warning You must never use the same nonce twice with the same key. 150 * This would void any confidentiality and authenticity 151 * guarantees for the messages encrypted with the same nonce 152 * and key. 153 * 154 * \note If the context is being used for AAD only (no data to 155 * encrypt or decrypt) then \p mode can be set to any value. 156 * 157 * \warning Decryption with the piecewise API is discouraged, see the 158 * warning on \c mbedtls_chachapoly_init(). 159 * 160 * \param ctx The ChaCha20-Poly1305 context. This must be initialized 161 * and bound to a key. 162 * \param nonce The nonce/IV to use for the message. 163 * This must be a redable buffer of length \c 12 Bytes. 164 * \param mode The operation to perform: #MBEDTLS_CHACHAPOLY_ENCRYPT or 165 * #MBEDTLS_CHACHAPOLY_DECRYPT (discouraged, see warning). 166 * 167 * \return \c 0 on success. 168 * \return A negative error code on failure. 169 */ 170 int mbedtls_chachapoly_starts( mbedtls_chachapoly_context *ctx, 171 const unsigned char nonce[12], 172 mbedtls_chachapoly_mode_t mode ); 173 174 /** 175 * \brief This function feeds additional data to be authenticated 176 * into an ongoing ChaCha20-Poly1305 operation. 177 * 178 * The Additional Authenticated Data (AAD), also called 179 * Associated Data (AD) is only authenticated but not 180 * encrypted nor included in the encrypted output. It is 181 * usually transmitted separately from the ciphertext or 182 * computed locally by each party. 183 * 184 * \note This function is called before data is encrypted/decrypted. 185 * I.e. call this function to process the AAD before calling 186 * \c mbedtls_chachapoly_update(). 187 * 188 * You may call this function multiple times to process 189 * an arbitrary amount of AAD. It is permitted to call 190 * this function 0 times, if no AAD is used. 191 * 192 * This function cannot be called any more if data has 193 * been processed by \c mbedtls_chachapoly_update(), 194 * or if the context has been finished. 195 * 196 * \warning Decryption with the piecewise API is discouraged, see the 197 * warning on \c mbedtls_chachapoly_init(). 198 * 199 * \param ctx The ChaCha20-Poly1305 context. This must be initialized 200 * and bound to a key. 201 * \param aad_len The length in Bytes of the AAD. The length has no 202 * restrictions. 203 * \param aad Buffer containing the AAD. 204 * This pointer can be \c NULL if `aad_len == 0`. 205 * 206 * \return \c 0 on success. 207 * \return #MBEDTLS_ERR_POLY1305_BAD_INPUT_DATA 208 * if \p ctx or \p aad are NULL. 209 * \return #MBEDTLS_ERR_CHACHAPOLY_BAD_STATE 210 * if the operations has not been started or has been 211 * finished, or if the AAD has been finished. 212 */ 213 int mbedtls_chachapoly_update_aad( mbedtls_chachapoly_context *ctx, 214 const unsigned char *aad, 215 size_t aad_len ); 216 217 /** 218 * \brief Thus function feeds data to be encrypted or decrypted 219 * into an on-going ChaCha20-Poly1305 220 * operation. 221 * 222 * The direction (encryption or decryption) depends on the 223 * mode that was given when calling 224 * \c mbedtls_chachapoly_starts(). 225 * 226 * You may call this function multiple times to process 227 * an arbitrary amount of data. It is permitted to call 228 * this function 0 times, if no data is to be encrypted 229 * or decrypted. 230 * 231 * \warning Decryption with the piecewise API is discouraged, see the 232 * warning on \c mbedtls_chachapoly_init(). 233 * 234 * \param ctx The ChaCha20-Poly1305 context to use. This must be initialized. 235 * \param len The length (in bytes) of the data to encrypt or decrypt. 236 * \param input The buffer containing the data to encrypt or decrypt. 237 * This pointer can be \c NULL if `len == 0`. 238 * \param output The buffer to where the encrypted or decrypted data is 239 * written. This must be able to hold \p len bytes. 240 * This pointer can be \c NULL if `len == 0`. 241 * 242 * \return \c 0 on success. 243 * \return #MBEDTLS_ERR_CHACHAPOLY_BAD_STATE 244 * if the operation has not been started or has been 245 * finished. 246 * \return Another negative error code on other kinds of failure. 247 */ 248 int mbedtls_chachapoly_update( mbedtls_chachapoly_context *ctx, 249 size_t len, 250 const unsigned char *input, 251 unsigned char *output ); 252 253 /** 254 * \brief This function finished the ChaCha20-Poly1305 operation and 255 * generates the MAC (authentication tag). 256 * 257 * \param ctx The ChaCha20-Poly1305 context to use. This must be initialized. 258 * \param mac The buffer to where the 128-bit (16 bytes) MAC is written. 259 * 260 * \warning Decryption with the piecewise API is discouraged, see the 261 * warning on \c mbedtls_chachapoly_init(). 262 * 263 * \return \c 0 on success. 264 * \return #MBEDTLS_ERR_CHACHAPOLY_BAD_STATE 265 * if the operation has not been started or has been 266 * finished. 267 * \return Another negative error code on other kinds of failure. 268 */ 269 int mbedtls_chachapoly_finish( mbedtls_chachapoly_context *ctx, 270 unsigned char mac[16] ); 271 272 /** 273 * \brief This function performs a complete ChaCha20-Poly1305 274 * authenticated encryption with the previously-set key. 275 * 276 * \note Before using this function, you must set the key with 277 * \c mbedtls_chachapoly_setkey(). 278 * 279 * \warning You must never use the same nonce twice with the same key. 280 * This would void any confidentiality and authenticity 281 * guarantees for the messages encrypted with the same nonce 282 * and key. 283 * 284 * \param ctx The ChaCha20-Poly1305 context to use (holds the key). 285 * This must be initialized. 286 * \param length The length (in bytes) of the data to encrypt or decrypt. 287 * \param nonce The 96-bit (12 bytes) nonce/IV to use. 288 * \param aad The buffer containing the additional authenticated 289 * data (AAD). This pointer can be \c NULL if `aad_len == 0`. 290 * \param aad_len The length (in bytes) of the AAD data to process. 291 * \param input The buffer containing the data to encrypt or decrypt. 292 * This pointer can be \c NULL if `ilen == 0`. 293 * \param output The buffer to where the encrypted or decrypted data 294 * is written. This pointer can be \c NULL if `ilen == 0`. 295 * \param tag The buffer to where the computed 128-bit (16 bytes) MAC 296 * is written. This must not be \c NULL. 297 * 298 * \return \c 0 on success. 299 * \return A negative error code on failure. 300 */ 301 int mbedtls_chachapoly_encrypt_and_tag( mbedtls_chachapoly_context *ctx, 302 size_t length, 303 const unsigned char nonce[12], 304 const unsigned char *aad, 305 size_t aad_len, 306 const unsigned char *input, 307 unsigned char *output, 308 unsigned char tag[16] ); 309 310 /** 311 * \brief This function performs a complete ChaCha20-Poly1305 312 * authenticated decryption with the previously-set key. 313 * 314 * \note Before using this function, you must set the key with 315 * \c mbedtls_chachapoly_setkey(). 316 * 317 * \param ctx The ChaCha20-Poly1305 context to use (holds the key). 318 * \param length The length (in Bytes) of the data to decrypt. 319 * \param nonce The \c 96 Bit (\c 12 bytes) nonce/IV to use. 320 * \param aad The buffer containing the additional authenticated data (AAD). 321 * This pointer can be \c NULL if `aad_len == 0`. 322 * \param aad_len The length (in bytes) of the AAD data to process. 323 * \param tag The buffer holding the authentication tag. 324 * This must be a readable buffer of length \c 16 Bytes. 325 * \param input The buffer containing the data to decrypt. 326 * This pointer can be \c NULL if `ilen == 0`. 327 * \param output The buffer to where the decrypted data is written. 328 * This pointer can be \c NULL if `ilen == 0`. 329 * 330 * \return \c 0 on success. 331 * \return #MBEDTLS_ERR_CHACHAPOLY_AUTH_FAILED 332 * if the data was not authentic. 333 * \return Another negative error code on other kinds of failure. 334 */ 335 int mbedtls_chachapoly_auth_decrypt( mbedtls_chachapoly_context *ctx, 336 size_t length, 337 const unsigned char nonce[12], 338 const unsigned char *aad, 339 size_t aad_len, 340 const unsigned char tag[16], 341 const unsigned char *input, 342 unsigned char *output ); 343 344 #if defined(MBEDTLS_SELF_TEST) 345 /** 346 * \brief The ChaCha20-Poly1305 checkup routine. 347 * 348 * \return \c 0 on success. 349 * \return \c 1 on failure. 350 */ 351 int mbedtls_chachapoly_self_test( int verbose ); 352 #endif /* MBEDTLS_SELF_TEST */ 353 354 #ifdef __cplusplus 355 } 356 #endif 357 358 #endif /* MBEDTLS_CHACHAPOLY_H */ 359