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 /** The requested operation is not permitted in the current state. */ 45 #define MBEDTLS_ERR_CHACHAPOLY_BAD_STATE -0x0054 46 /** Authenticated decryption failed: data was not authentic. */ 47 #define MBEDTLS_ERR_CHACHAPOLY_AUTH_FAILED -0x0056 48 49 #ifdef __cplusplus 50 extern "C" { 51 #endif 52 53 typedef enum 54 { 55 MBEDTLS_CHACHAPOLY_ENCRYPT, /**< The mode value for performing encryption. */ 56 MBEDTLS_CHACHAPOLY_DECRYPT /**< The mode value for performing decryption. */ 57 } 58 mbedtls_chachapoly_mode_t; 59 60 #if !defined(MBEDTLS_CHACHAPOLY_ALT) 61 62 #include "mbedtls/chacha20.h" 63 64 typedef struct mbedtls_chachapoly_context 65 { 66 mbedtls_chacha20_context chacha20_ctx; /**< The ChaCha20 context. */ 67 mbedtls_poly1305_context poly1305_ctx; /**< The Poly1305 context. */ 68 uint64_t aad_len; /**< The length (bytes) of the Additional Authenticated Data. */ 69 uint64_t ciphertext_len; /**< The length (bytes) of the ciphertext. */ 70 int state; /**< The current state of the context. */ 71 mbedtls_chachapoly_mode_t mode; /**< Cipher mode (encrypt or decrypt). */ 72 } 73 mbedtls_chachapoly_context; 74 75 #else /* !MBEDTLS_CHACHAPOLY_ALT */ 76 #include "chachapoly_alt.h" 77 #endif /* !MBEDTLS_CHACHAPOLY_ALT */ 78 79 /** 80 * \brief This function initializes the specified ChaCha20-Poly1305 context. 81 * 82 * It must be the first API called before using 83 * the context. It must be followed by a call to 84 * \c mbedtls_chachapoly_setkey() before any operation can be 85 * done, and to \c mbedtls_chachapoly_free() once all 86 * operations with that context have been finished. 87 * 88 * In order to encrypt or decrypt full messages at once, for 89 * each message you should make a single call to 90 * \c mbedtls_chachapoly_crypt_and_tag() or 91 * \c mbedtls_chachapoly_auth_decrypt(). 92 * 93 * In order to encrypt messages piecewise, for each 94 * message you should make a call to 95 * \c mbedtls_chachapoly_starts(), then 0 or more calls to 96 * \c mbedtls_chachapoly_update_aad(), then 0 or more calls to 97 * \c mbedtls_chachapoly_update(), then one call to 98 * \c mbedtls_chachapoly_finish(). 99 * 100 * \warning Decryption with the piecewise API is discouraged! Always 101 * use \c mbedtls_chachapoly_auth_decrypt() when possible! 102 * 103 * If however this is not possible because the data is too 104 * large to fit in memory, you need to: 105 * 106 * - call \c mbedtls_chachapoly_starts() and (if needed) 107 * \c mbedtls_chachapoly_update_aad() as above, 108 * - call \c mbedtls_chachapoly_update() multiple times and 109 * ensure its output (the plaintext) is NOT used in any other 110 * way than placing it in temporary storage at this point, 111 * - call \c mbedtls_chachapoly_finish() to compute the 112 * authentication tag and compared it in constant time to the 113 * tag received with the ciphertext. 114 * 115 * If the tags are not equal, you must immediately discard 116 * all previous outputs of \c mbedtls_chachapoly_update(), 117 * otherwise you can now safely use the plaintext. 118 * 119 * \param ctx The ChachaPoly context to initialize. Must not be \c NULL. 120 */ 121 void mbedtls_chachapoly_init( mbedtls_chachapoly_context *ctx ); 122 123 /** 124 * \brief This function releases and clears the specified 125 * ChaCha20-Poly1305 context. 126 * 127 * \param ctx The ChachaPoly context to clear. This may be \c NULL, in which 128 * case this function is a no-op. 129 */ 130 void mbedtls_chachapoly_free( mbedtls_chachapoly_context *ctx ); 131 132 /** 133 * \brief This function sets the ChaCha20-Poly1305 134 * symmetric encryption key. 135 * 136 * \param ctx The ChaCha20-Poly1305 context to which the key should be 137 * bound. This must be initialized. 138 * \param key The \c 256 Bit (\c 32 Bytes) key. 139 * 140 * \return \c 0 on success. 141 * \return A negative error code on failure. 142 */ 143 int mbedtls_chachapoly_setkey( mbedtls_chachapoly_context *ctx, 144 const unsigned char key[32] ); 145 146 /** 147 * \brief This function starts a ChaCha20-Poly1305 encryption or 148 * decryption operation. 149 * 150 * \warning You must never use the same nonce twice with the same key. 151 * This would void any confidentiality and authenticity 152 * guarantees for the messages encrypted with the same nonce 153 * and key. 154 * 155 * \note If the context is being used for AAD only (no data to 156 * encrypt or decrypt) then \p mode can be set to any value. 157 * 158 * \warning Decryption with the piecewise API is discouraged, see the 159 * warning on \c mbedtls_chachapoly_init(). 160 * 161 * \param ctx The ChaCha20-Poly1305 context. This must be initialized 162 * and bound to a key. 163 * \param nonce The nonce/IV to use for the message. 164 * This must be a readable buffer of length \c 12 Bytes. 165 * \param mode The operation to perform: #MBEDTLS_CHACHAPOLY_ENCRYPT or 166 * #MBEDTLS_CHACHAPOLY_DECRYPT (discouraged, see warning). 167 * 168 * \return \c 0 on success. 169 * \return A negative error code on failure. 170 */ 171 int mbedtls_chachapoly_starts( mbedtls_chachapoly_context *ctx, 172 const unsigned char nonce[12], 173 mbedtls_chachapoly_mode_t mode ); 174 175 /** 176 * \brief This function feeds additional data to be authenticated 177 * into an ongoing ChaCha20-Poly1305 operation. 178 * 179 * The Additional Authenticated Data (AAD), also called 180 * Associated Data (AD) is only authenticated but not 181 * encrypted nor included in the encrypted output. It is 182 * usually transmitted separately from the ciphertext or 183 * computed locally by each party. 184 * 185 * \note This function is called before data is encrypted/decrypted. 186 * I.e. call this function to process the AAD before calling 187 * \c mbedtls_chachapoly_update(). 188 * 189 * You may call this function multiple times to process 190 * an arbitrary amount of AAD. It is permitted to call 191 * this function 0 times, if no AAD is used. 192 * 193 * This function cannot be called any more if data has 194 * been processed by \c mbedtls_chachapoly_update(), 195 * or if the context has been finished. 196 * 197 * \warning Decryption with the piecewise API is discouraged, see the 198 * warning on \c mbedtls_chachapoly_init(). 199 * 200 * \param ctx The ChaCha20-Poly1305 context. This must be initialized 201 * and bound to a key. 202 * \param aad_len The length in Bytes of the AAD. The length has no 203 * restrictions. 204 * \param aad Buffer containing the AAD. 205 * This pointer can be \c NULL if `aad_len == 0`. 206 * 207 * \return \c 0 on success. 208 * \return #MBEDTLS_ERR_POLY1305_BAD_INPUT_DATA 209 * if \p ctx or \p aad are NULL. 210 * \return #MBEDTLS_ERR_CHACHAPOLY_BAD_STATE 211 * if the operations has not been started or has been 212 * finished, or if the AAD has been finished. 213 */ 214 int mbedtls_chachapoly_update_aad( mbedtls_chachapoly_context *ctx, 215 const unsigned char *aad, 216 size_t aad_len ); 217 218 /** 219 * \brief Thus function feeds data to be encrypted or decrypted 220 * into an on-going ChaCha20-Poly1305 221 * operation. 222 * 223 * The direction (encryption or decryption) depends on the 224 * mode that was given when calling 225 * \c mbedtls_chachapoly_starts(). 226 * 227 * You may call this function multiple times to process 228 * an arbitrary amount of data. It is permitted to call 229 * this function 0 times, if no data is to be encrypted 230 * or decrypted. 231 * 232 * \warning Decryption with the piecewise API is discouraged, see the 233 * warning on \c mbedtls_chachapoly_init(). 234 * 235 * \param ctx The ChaCha20-Poly1305 context to use. This must be initialized. 236 * \param len The length (in bytes) of the data to encrypt or decrypt. 237 * \param input The buffer containing the data to encrypt or decrypt. 238 * This pointer can be \c NULL if `len == 0`. 239 * \param output The buffer to where the encrypted or decrypted data is 240 * written. This must be able to hold \p len bytes. 241 * This pointer can be \c NULL if `len == 0`. 242 * 243 * \return \c 0 on success. 244 * \return #MBEDTLS_ERR_CHACHAPOLY_BAD_STATE 245 * if the operation has not been started or has been 246 * finished. 247 * \return Another negative error code on other kinds of failure. 248 */ 249 int mbedtls_chachapoly_update( mbedtls_chachapoly_context *ctx, 250 size_t len, 251 const unsigned char *input, 252 unsigned char *output ); 253 254 /** 255 * \brief This function finished the ChaCha20-Poly1305 operation and 256 * generates the MAC (authentication tag). 257 * 258 * \param ctx The ChaCha20-Poly1305 context to use. This must be initialized. 259 * \param mac The buffer to where the 128-bit (16 bytes) MAC is written. 260 * 261 * \warning Decryption with the piecewise API is discouraged, see the 262 * warning on \c mbedtls_chachapoly_init(). 263 * 264 * \return \c 0 on success. 265 * \return #MBEDTLS_ERR_CHACHAPOLY_BAD_STATE 266 * if the operation has not been started or has been 267 * finished. 268 * \return Another negative error code on other kinds of failure. 269 */ 270 int mbedtls_chachapoly_finish( mbedtls_chachapoly_context *ctx, 271 unsigned char mac[16] ); 272 273 /** 274 * \brief This function performs a complete ChaCha20-Poly1305 275 * authenticated encryption with the previously-set key. 276 * 277 * \note Before using this function, you must set the key with 278 * \c mbedtls_chachapoly_setkey(). 279 * 280 * \warning You must never use the same nonce twice with the same key. 281 * This would void any confidentiality and authenticity 282 * guarantees for the messages encrypted with the same nonce 283 * and key. 284 * 285 * \param ctx The ChaCha20-Poly1305 context to use (holds the key). 286 * This must be initialized. 287 * \param length The length (in bytes) of the data to encrypt or decrypt. 288 * \param nonce The 96-bit (12 bytes) nonce/IV to use. 289 * \param aad The buffer containing the additional authenticated 290 * data (AAD). This pointer can be \c NULL if `aad_len == 0`. 291 * \param aad_len The length (in bytes) of the AAD data to process. 292 * \param input The buffer containing the data to encrypt or decrypt. 293 * This pointer can be \c NULL if `ilen == 0`. 294 * \param output The buffer to where the encrypted or decrypted data 295 * is written. This pointer can be \c NULL if `ilen == 0`. 296 * \param tag The buffer to where the computed 128-bit (16 bytes) MAC 297 * is written. This must not be \c NULL. 298 * 299 * \return \c 0 on success. 300 * \return A negative error code on failure. 301 */ 302 int mbedtls_chachapoly_encrypt_and_tag( mbedtls_chachapoly_context *ctx, 303 size_t length, 304 const unsigned char nonce[12], 305 const unsigned char *aad, 306 size_t aad_len, 307 const unsigned char *input, 308 unsigned char *output, 309 unsigned char tag[16] ); 310 311 /** 312 * \brief This function performs a complete ChaCha20-Poly1305 313 * authenticated decryption with the previously-set key. 314 * 315 * \note Before using this function, you must set the key with 316 * \c mbedtls_chachapoly_setkey(). 317 * 318 * \param ctx The ChaCha20-Poly1305 context to use (holds the key). 319 * \param length The length (in Bytes) of the data to decrypt. 320 * \param nonce The \c 96 Bit (\c 12 bytes) nonce/IV to use. 321 * \param aad The buffer containing the additional authenticated data (AAD). 322 * This pointer can be \c NULL if `aad_len == 0`. 323 * \param aad_len The length (in bytes) of the AAD data to process. 324 * \param tag The buffer holding the authentication tag. 325 * This must be a readable buffer of length \c 16 Bytes. 326 * \param input The buffer containing the data to decrypt. 327 * This pointer can be \c NULL if `ilen == 0`. 328 * \param output The buffer to where the decrypted data is written. 329 * This pointer can be \c NULL if `ilen == 0`. 330 * 331 * \return \c 0 on success. 332 * \return #MBEDTLS_ERR_CHACHAPOLY_AUTH_FAILED 333 * if the data was not authentic. 334 * \return Another negative error code on other kinds of failure. 335 */ 336 int mbedtls_chachapoly_auth_decrypt( mbedtls_chachapoly_context *ctx, 337 size_t length, 338 const unsigned char nonce[12], 339 const unsigned char *aad, 340 size_t aad_len, 341 const unsigned char tag[16], 342 const unsigned char *input, 343 unsigned char *output ); 344 345 #if defined(MBEDTLS_SELF_TEST) 346 /** 347 * \brief The ChaCha20-Poly1305 checkup routine. 348 * 349 * \return \c 0 on success. 350 * \return \c 1 on failure. 351 */ 352 int mbedtls_chachapoly_self_test( int verbose ); 353 #endif /* MBEDTLS_SELF_TEST */ 354 355 #ifdef __cplusplus 356 } 357 #endif 358 359 #endif /* MBEDTLS_CHACHAPOLY_H */ 360