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