| 1 | /* -*-c-*- |
| 2 | * |
| 3 | * The EAX authenticated-encryption mode |
| 4 | * |
| 5 | * (c) 2017 Straylight/Edgeware |
| 6 | */ |
| 7 | |
| 8 | /*----- Licensing notice --------------------------------------------------* |
| 9 | * |
| 10 | * This file is part of Catacomb. |
| 11 | * |
| 12 | * Catacomb is free software; you can redistribute it and/or modify |
| 13 | * it under the terms of the GNU Library General Public License as |
| 14 | * published by the Free Software Foundation; either version 2 of the |
| 15 | * License, or (at your option) any later version. |
| 16 | * |
| 17 | * Catacomb is distributed in the hope that it will be useful, |
| 18 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 19 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 20 | * GNU Library General Public License for more details. |
| 21 | * |
| 22 | * You should have received a copy of the GNU Library General Public |
| 23 | * License along with Catacomb; if not, write to the Free |
| 24 | * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, |
| 25 | * MA 02111-1307, USA. |
| 26 | */ |
| 27 | |
| 28 | /*----- Notes on EAX ------------------------------------------------------* |
| 29 | * |
| 30 | * The name doesn't appear to be short for anything convincing. EAX was |
| 31 | * designed in 2004 by Mihir Bellare, Phillip Rogaway, and David Wagner, as a |
| 32 | * response to CCM's deficiencies, which Rogaway and Wagner had complained |
| 33 | * about the previous year. Like CCM, it's a patent-free authenticated |
| 34 | * encryption scheme based on counter mode and CBC-MAC, and needs two |
| 35 | * blockcipher applications per message block, but it's much more refined |
| 36 | * than CCM. The EAX specification is clear about how the mode applies to |
| 37 | * arbitrary block sizes, and I've not had to make any decisions on how to |
| 38 | * extend it myself. |
| 39 | * |
| 40 | * EAX allows arbitrarily sized nonces, and doesn't require precommitment to |
| 41 | * any lengths, and allows header data to be processed independently of any |
| 42 | * message. It's basically about as good as a rate-1/2 scheme is going to |
| 43 | * be. |
| 44 | */ |
| 45 | |
| 46 | #ifndef CATACOMB_EAX_H |
| 47 | #define CATACOMB_EAX_H |
| 48 | |
| 49 | #ifdef __cplusplus |
| 50 | extern "C" { |
| 51 | #endif |
| 52 | |
| 53 | /*----- Header files ------------------------------------------------------*/ |
| 54 | |
| 55 | #include <stddef.h> |
| 56 | |
| 57 | #include <mLib/bits.h> |
| 58 | #include <mLib/buf.h> |
| 59 | |
| 60 | #ifndef CATACOMB_GAEAD_H |
| 61 | # include "gaead.h" |
| 62 | #endif |
| 63 | |
| 64 | /*----- Macros ------------------------------------------------------------*/ |
| 65 | |
| 66 | /* --- @EAX_DECL@ --- * |
| 67 | * |
| 68 | * Arguments: @PRE@, @pre@ = prefixes for the underlying block cipher |
| 69 | * |
| 70 | * Use: Creates declarations for EAX authenticated-encryption mode. |
| 71 | */ |
| 72 | |
| 73 | #define EAX_DECL(PRE, pre) \ |
| 74 | \ |
| 75 | typedef struct pre##_eaxkey { \ |
| 76 | pre##_ctx ctx; /* Block cipher key */ \ |
| 77 | uint32 m0[PRE##_BLKSZ/4], m1[PRE##_BLKSZ/4]; /* Final OMAC masks */ \ |
| 78 | uint32 v0[PRE##_BLKSZ/4], /* OMAC tweak accumulators */ \ |
| 79 | v1[PRE##_BLKSZ/4], v2[PRE##_BLKSZ/4]; \ |
| 80 | uint32 z0[PRE##_BLKSZ/4], /* Empty-message tag values */ \ |
| 81 | z1[PRE##_BLKSZ/4], z2[PRE##_BLKSZ/4]; \ |
| 82 | } pre##_eaxkey; \ |
| 83 | \ |
| 84 | typedef struct pre##_eaxaadctx { \ |
| 85 | pre##_eaxkey k; /* Underlying key */ \ |
| 86 | uint32 a[PRE##_BLKSZ/4]; /* OMAC accumulator */ \ |
| 87 | octet b[PRE##_BLKSZ]; /* Input buffer */ \ |
| 88 | unsigned off; /* Length of stuff in buffer */ \ |
| 89 | } pre##_eaxaadctx; \ |
| 90 | \ |
| 91 | typedef struct pre##_eaxctx { \ |
| 92 | /* The buffer is split into two portions. The first N octets hold a \ |
| 93 | * chunk of ciphertext, which will be fed into the OMAC calculation; \ |
| 94 | * the remaining BLKSZ - N octets hold E_K(C), which is the XOR mask \ |
| 95 | * to apply to the plaintext or ciphertext. \ |
| 96 | */ \ |
| 97 | pre##_eaxkey k; /* Underlying key */ \ |
| 98 | uint32 c[PRE##_BLKSZ/4]; /* Current counter value */ \ |
| 99 | uint32 c0[PRE##_BLKSZ/4]; /* Initial counter */ \ |
| 100 | uint32 a[PRE##_BLKSZ]; /* OMAC accumulator */ \ |
| 101 | octet b[PRE##_BLKSZ]; /* Ciphertext/mask buffer */ \ |
| 102 | unsigned off; /* Crossover point in buffer */ \ |
| 103 | } pre##_eaxctx; \ |
| 104 | \ |
| 105 | extern const octet pre##_eaxnoncesz[], pre##_eaxtagsz[]; \ |
| 106 | \ |
| 107 | /* --- @pre_eaxsetkey@ --- * \ |
| 108 | * \ |
| 109 | * Arguments: @pre_eaxkey *key@ = pointer to key block to fill in \ |
| 110 | * @const void *k@ = pointer to key material \ |
| 111 | * @size_t ksz@ = size of key material \ |
| 112 | * \ |
| 113 | * Returns: --- \ |
| 114 | * \ |
| 115 | * Use: Initializes an EAX key block. \ |
| 116 | */ \ |
| 117 | \ |
| 118 | extern void pre##_eaxsetkey(pre##_eaxkey */*key*/, \ |
| 119 | const void */*k*/, size_t /*ksz*/); \ |
| 120 | \ |
| 121 | /* --- @pre_eaxaadinit@ --- * \ |
| 122 | * \ |
| 123 | * Arguments: @pre_eaxaadctx *aad@ = pointer to AAD context \ |
| 124 | * @const pre_eaxkey *key@ = pointer to key block \ |
| 125 | * \ |
| 126 | * Returns: --- \ |
| 127 | * \ |
| 128 | * Use: Initializes an EAX AAD (`additional authenticated \ |
| 129 | * data') context associated with a given key. AAD \ |
| 130 | * contexts can be copied and/or reused, saving time if \ |
| 131 | * the AAD for a number of messages has a common prefix. \ |
| 132 | * \ |
| 133 | * The @key@ doesn't need to be kept around, though \ |
| 134 | * usually there'll at least be another copy in some EAX \ |
| 135 | * operation context because the AAD on its own isn't much \ |
| 136 | * good. \ |
| 137 | */ \ |
| 138 | \ |
| 139 | extern void pre##_eaxaadinit(pre##_eaxaadctx */*aad*/, \ |
| 140 | const pre##_eaxkey */*key*/); \ |
| 141 | \ |
| 142 | /* --- @pre_eaxaadhash@ --- * \ |
| 143 | * \ |
| 144 | * Arguments: @pre_eaxaadctx *aad@ = pointer to AAD context \ |
| 145 | * @const void *p@ = pointer to AAD material \ |
| 146 | * @size_t sz@ = length of AAD material \ |
| 147 | * \ |
| 148 | * Returns: --- \ |
| 149 | * \ |
| 150 | * Use: Feeds AAD into the context. \ |
| 151 | */ \ |
| 152 | \ |
| 153 | extern void pre##_eaxaadhash(pre##_eaxaadctx */*aad*/, \ |
| 154 | const void */*p*/, size_t /*sz*/); \ |
| 155 | \ |
| 156 | /* --- @pre_eaxinit@ --- * \ |
| 157 | * \ |
| 158 | * Arguments: @pre_eaxctx *ctx@ = pointer to EAX context \ |
| 159 | * @const pre_eaxkey *key@ = pointer to key block \ |
| 160 | * @const void *n@ = pointer to nonce \ |
| 161 | * @size_t nsz@ = size of nonce \ |
| 162 | * \ |
| 163 | * Returns: --- \ |
| 164 | * \ |
| 165 | * Use: Initialize an EAX operation context with a given key. \ |
| 166 | * \ |
| 167 | * The original key needn't be kept around any more. \ |
| 168 | */ \ |
| 169 | \ |
| 170 | extern void pre##_eaxinit(pre##_eaxctx */*ctx*/, \ |
| 171 | const pre##_eaxkey */*k*/, \ |
| 172 | const void */*n*/, size_t /*nsz*/); \ |
| 173 | \ |
| 174 | /* --- @pre_eaxreinit@ --- * \ |
| 175 | * \ |
| 176 | * Arguments: @pre_eaxctx *ctx@ = pointer to EAX context \ |
| 177 | * @const void *n@ = pointer to nonce \ |
| 178 | * @size_t nsz@ = size of nonce \ |
| 179 | * \ |
| 180 | * Returns: --- \ |
| 181 | * \ |
| 182 | * Use: Reinitialize an EAX operation context, changing the \ |
| 183 | * nonce. \ |
| 184 | */ \ |
| 185 | \ |
| 186 | extern void pre##_eaxreinit(pre##_eaxctx */*ctx*/, \ |
| 187 | const void */*n*/, size_t /*nsz*/); \ |
| 188 | \ |
| 189 | /* --- @pre_eaxencrypt@ --- * \ |
| 190 | * \ |
| 191 | * Arguments: @pre_eaxctx *ctx@ = pointer to EAX operation context \ |
| 192 | * @const void *src@ = pointer to plaintext message chunk \ |
| 193 | * @size_t sz@ = size of the plaintext \ |
| 194 | * @buf *dst@ = a buffer to write the ciphertext to \ |
| 195 | * \ |
| 196 | * Returns: Zero on success; @-1@ on failure. \ |
| 197 | * \ |
| 198 | * Use: Encrypts a chunk of a plaintext message, writing a \ |
| 199 | * chunk of ciphertext to the output buffer and updating \ |
| 200 | * the operation state. \ |
| 201 | * \ |
| 202 | * For EAX, we always write a ciphertext chunk the same \ |
| 203 | * size as the plaintext. The messing about with @buf@ \ |
| 204 | * objects makes the interface consistent with other AEAD \ |
| 205 | * schemes which can't do this. \ |
| 206 | */ \ |
| 207 | \ |
| 208 | extern int pre##_eaxencrypt(pre##_eaxctx */*ctx*/, \ |
| 209 | const void */*src*/, size_t /*sz*/, \ |
| 210 | buf */*dst*/); \ |
| 211 | \ |
| 212 | /* --- @pre_eaxdecrypt@ --- * \ |
| 213 | * \ |
| 214 | * Arguments: @pre_eaxctx *ctx@ = pointer to EAX operation context \ |
| 215 | * @const void *src@ = pointer to ciphertext message chunk \ |
| 216 | * @size_t sz@ = size of the ciphertext \ |
| 217 | * @buf *dst@ = a buffer to write the plaintext to \ |
| 218 | * \ |
| 219 | * Returns: Zero on success; @-1@ on failure. \ |
| 220 | * \ |
| 221 | * Use: Decrypts a chunk of a ciphertext message, writing a \ |
| 222 | * chunk of plaintext to the output buffer and updating \ |
| 223 | * the operation state. \ |
| 224 | * \ |
| 225 | * For EAX, we always write a plaintext chunk the same \ |
| 226 | * size as the ciphertext. The messing about with @buf@ \ |
| 227 | * objects makes the interface consistent with other AEAD \ |
| 228 | * schemes which can't do this. \ |
| 229 | */ \ |
| 230 | \ |
| 231 | extern int pre##_eaxdecrypt(pre##_eaxctx */*ctx*/, \ |
| 232 | const void */*src*/, size_t /*sz*/, \ |
| 233 | buf */*dst*/); \ |
| 234 | \ |
| 235 | /* --- @pre_eaxencryptdone@ --- * \ |
| 236 | * \ |
| 237 | * Arguments: @pre_eaxctx *ctx@ = pointer to an EAX context \ |
| 238 | * @const pre_eaxaadctx *aad@ = pointer to AAD context, or \ |
| 239 | * null \ |
| 240 | * @buf *dst@ = buffer for remaining ciphertext \ |
| 241 | * @void *tag@ = where to write the tag \ |
| 242 | * @size_t tsz@ = length of tag to store \ |
| 243 | * \ |
| 244 | * Returns: Zero on success; @-1@ on failure. \ |
| 245 | * \ |
| 246 | * Use: Completes an EAX encryption operation. The @aad@ \ |
| 247 | * pointer may be null if there is no additional \ |
| 248 | * authenticated data. EAX doesn't buffer ciphertext, but \ |
| 249 | * the output buffer is provided anyway for consistency \ |
| 250 | * with other AEAD schemes which don't have this property; \ |
| 251 | * the function will fail if the output buffer is broken. \ |
| 252 | */ \ |
| 253 | \ |
| 254 | extern int pre##_eaxencryptdone(pre##_eaxctx */*ctx*/, \ |
| 255 | const pre##_eaxaadctx */*aad*/, \ |
| 256 | buf */*dst*/, \ |
| 257 | void */*tag*/, size_t /*tsz*/); \ |
| 258 | \ |
| 259 | /* --- @pre_eaxdecryptdone@ --- * \ |
| 260 | * \ |
| 261 | * Arguments: @pre_eaxctx *ctx@ = pointer to an EAX context \ |
| 262 | * @const pre_eaxaadctx *aad@ = pointer to AAD context, or \ |
| 263 | * null \ |
| 264 | * @buf *dst@ = buffer for remaining plaintext \ |
| 265 | * @const void *tag@ = tag to verify \ |
| 266 | * @size_t tsz@ = length of tag \ |
| 267 | * \ |
| 268 | * Returns: @+1@ for complete success; @0@ if tag verification \ |
| 269 | * failed; @-1@ for other kinds of errors. \ |
| 270 | * \ |
| 271 | * Use: Completes an EAX decryption operation. The @aad@ \ |
| 272 | * pointer may be null if there is no additional \ |
| 273 | * authenticated data. EAX doesn't buffer plaintext, but \ |
| 274 | * the output buffer is provided anyway for consistency \ |
| 275 | * with other AEAD schemes which don't have this property; \ |
| 276 | * the function will fail if the output buffer is broken. \ |
| 277 | */ \ |
| 278 | \ |
| 279 | extern int pre##_eaxdecryptdone(pre##_eaxctx */*ctx*/, \ |
| 280 | const pre##_eaxaadctx */*aad*/, \ |
| 281 | buf */*dst*/, \ |
| 282 | const void */*tag*/, size_t /*tsz*/); \ |
| 283 | \ |
| 284 | /* --- Generic AEAD interface --- */ \ |
| 285 | \ |
| 286 | extern const gcaead pre##_eax; |
| 287 | |
| 288 | /*----- That's all, folks -------------------------------------------------*/ |
| 289 | |
| 290 | #ifdef __cplusplus |
| 291 | } |
| 292 | #endif |
| 293 | |
| 294 | #endif |