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