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