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