crypto/kmac/kmac.c

   1 /*
   2  * Copyright 2018 The OpenSSL Project Authors. All Rights Reserved.
   3  *
   4  * Licensed under the OpenSSL license (the "License").  You may not use
   5  * this file except in compliance with the License.  You can obtain a copy
   6  * in the file LICENSE in the source distribution or at
   7  * https://www.openssl.org/source/license.html
   8  */
   9
  10 /*
  11  * See SP800-185 "Appendix A - KMAC, .... in Terms of Keccak[c]"
  12  *
  13  * Inputs are:
  14  *    K = Key                  (len(K) < 2^2040 bits)
  15  *    X = Input
  16  *    L = Output length        (0 <= L < 2^2040 bits)
  17  *    S = Customization String Default="" (len(S) < 2^2040 bits)
  18  *
  19  * KMAC128(K, X, L, S)
  20  * {
  21  *     newX = bytepad(encode_string(K), 168) ||  X || right_encode(L).
  22  *     T = bytepad(encode_string(“KMAC”) || encode_string(S), 168).
  23  *     return KECCAK[256](T || newX || 00, L).
  24  * }
  25  *
  26  * KMAC256(K, X, L, S)
  27  * {
  28  *     newX = bytepad(encode_string(K), 136) ||  X || right_encode(L).
  29  *     T = bytepad(encode_string(“KMAC”) || encode_string(S), 136).
  30  *     return KECCAK[512](T || newX || 00, L).
  31  * }
  32  *
  33  * KMAC128XOF(K, X, L, S)
  34  * {
  35  *     newX = bytepad(encode_string(K), 168) ||  X || right_encode(0).
  36  *     T = bytepad(encode_string(“KMAC”) || encode_string(S), 168).
  37  *     return KECCAK[256](T || newX || 00, L).
  38  * }
  39  *
  40  * KMAC256XOF(K, X, L, S)
  41  * {
  42  *     newX = bytepad(encode_string(K), 136) ||  X || right_encode(0).
  43  *     T = bytepad(encode_string(“KMAC”) || encode_string(S), 136).
  44  *     return KECCAK[512](T || newX || 00, L).
  45  * }
  46  *
  47  */
  48
  49 #include <stdlib.h>
  50 #include <openssl/evp.h>
  51 #include "internal/cryptlib.h"
  52 #include "internal/evp_int.h"
  53
  54 #define KMAC_MAX_BLOCKSIZE ((1600 - 128*2) / 8) /* 168 */
  55 #define KMAC_MIN_BLOCKSIZE ((1600 - 256*2) / 8) /* 136 */
  56
  57 /* Length encoding will be  a 1 byte size + length in bits (2 bytes max) */
  58 #define KMAC_MAX_ENCODED_HEADER_LEN 3
  59
  60 /*
  61  * Custom string max size is chosen such that:
  62  *   len(encoded_string(custom) + len(kmac_encoded_string) <= KMAC_MIN_BLOCKSIZE
  63  *   i.e: (KMAC_MAX_CUSTOM + KMAC_MAX_ENCODED_LEN) + 6 <= 136
  64  */
  65 #define KMAC_MAX_CUSTOM 127
  66
  67 /* Maximum size of encoded custom string */
  68 #define KMAC_MAX_CUSTOM_ENCODED (KMAC_MAX_CUSTOM + KMAC_MAX_ENCODED_HEADER_LEN)
  69
  70 /* Maximum key size in bytes = 2040 / 8 */
  71 #define KMAC_MAX_KEY 255
  72
  73 /*
  74  * Maximum Encoded Key size will be padded to a multiple of the blocksize
  75  * i.e KMAC_MAX_KEY + KMAC_MAX_ENCODED_LEN = 258
  76  * Padded to a multiple of KMAC_MAX_BLOCKSIZE
  77  */
  78 #define KMAC_MAX_KEY_ENCODED (KMAC_MAX_BLOCKSIZE * 2)
  79
  80 /* Fixed value of encode_string("KMAC") */
  81 static const unsigned char kmac_string[] = {
  82     0x01, 0x20, 0x4B, 0x4D, 0x41, 0x43
  83 };
  84
  85
  86 #define KMAC_FLAG_XOF_MODE          1
  87
  88 /* typedef EVP_MAC_IMPL */
  89 struct evp_mac_impl_st {
  90     EVP_MD_CTX *ctx;
  91     const EVP_MD *md;
  92     size_t out_len;
  93     int key_len;
  94     int custom_len;
  95     /* If xof_mode = 1 then we use right_encode(0) */
  96     int xof_mode;
  97     /* key and custom are stored in encoded form */
  98     unsigned char key[KMAC_MAX_KEY_ENCODED];
  99     unsigned char custom[KMAC_MAX_CUSTOM_ENCODED];
 100 };
 101
 102 static int encode_string(unsigned char *out, int *out_len,
 103                          const unsigned char *in, int in_len);
 104 static int right_encode(unsigned char *out, int *out_len, size_t bits);
 105 static int bytepad(unsigned char *out, int *out_len,
 106                    const unsigned char *in1, int in1_len,
 107                    const unsigned char *in2, int in2_len,
 108                    int w);
 109 static int kmac_bytepad_encode_key(unsigned char *out, int *out_len,
 110                                    const unsigned char *in, int in_len,
 111                                    int w);
 112 static int kmac_ctrl_str(EVP_MAC_IMPL *kctx, const char *type,
 113                          const char *value);
 114
 115
 116 static void kmac_free(EVP_MAC_IMPL *kctx)
 117 {
 118     if (kctx != NULL) {
 119         EVP_MD_CTX_free(kctx->ctx);
 120         OPENSSL_cleanse(kctx->key, kctx->key_len);
 121         OPENSSL_cleanse(kctx->custom, kctx->custom_len);
 122         OPENSSL_free(kctx);
 123     }
 124 }
 125
 126 static EVP_MAC_IMPL *kmac_new(const EVP_MD *md)
 127 {
 128     EVP_MAC_IMPL *kctx = NULL;
 129
 130     if ((kctx = OPENSSL_zalloc(sizeof(*kctx))) == NULL
 131             || (kctx->ctx = EVP_MD_CTX_new()) == NULL) {
 132         kmac_free(kctx);
 133         return NULL;
 134     }
 135     kctx->md = md;
 136     kctx->out_len = md->md_size;
 137     return kctx;
 138 }
 139
 140 static EVP_MAC_IMPL *kmac128_new(void)
 141 {
 142     return kmac_new(evp_keccak_kmac128());
 143 }
 144
 145 static EVP_MAC_IMPL *kmac256_new(void)
 146 {
 147     return kmac_new(evp_keccak_kmac256());
 148 }
 149
 150 static int kmac_copy(EVP_MAC_IMPL *gdst, EVP_MAC_IMPL *gsrc)
 151 {
 152     gdst->md = gsrc->md;
 153     gdst->out_len = gsrc->out_len;
 154     gdst->key_len = gsrc->key_len;
 155     gdst->custom_len = gsrc->custom_len;
 156     gdst->xof_mode = gsrc->xof_mode;
 157     memcpy(gdst->key, gsrc->key, gsrc->key_len);
 158     memcpy(gdst->custom, gsrc->custom, gdst->custom_len);
 159
 160     return EVP_MD_CTX_copy(gdst->ctx, gsrc->ctx);
 161 }
 162
 163 /*
 164  * The init() assumes that any ctrl methods are set beforehand for
 165  * md, key and custom. Setting the fields afterwards will have no
 166  * effect on the output mac.
 167  */
 168 static int kmac_init(EVP_MAC_IMPL *kctx)
 169 {
 170     EVP_MD_CTX *ctx = kctx->ctx;
 171     unsigned char out[KMAC_MAX_BLOCKSIZE];
 172     int out_len, block_len;
 173
 174     /* Check key has been set */
 175     if (kctx->key_len == 0) {
 176         EVPerr(EVP_F_KMAC_INIT, EVP_R_NO_KEY_SET);
 177         return 0;
 178     }
 179     if (!EVP_DigestInit_ex(kctx->ctx, kctx->md, NULL))
 180         return 0;
 181
 182     block_len = EVP_MD_block_size(kctx->md);
 183
 184     /* Set default custom string if it is not already set */
 185     if (kctx->custom_len == 0)
 186         (void)kmac_ctrl_str(kctx, "custom", "");
 187
 188     return bytepad(out, &out_len, kmac_string, sizeof(kmac_string),
 189                    kctx->custom, kctx->custom_len, block_len)
 190            && EVP_DigestUpdate(ctx, out, out_len)
 191            && EVP_DigestUpdate(ctx, kctx->key, kctx->key_len);
 192 }
 193
 194 static size_t kmac_size(EVP_MAC_IMPL *kctx)
 195 {
 196     return kctx->out_len;
 197 }
 198
 199 static int kmac_update(EVP_MAC_IMPL *kctx, const unsigned char *data,
 200                        size_t datalen)
 201 {
 202     return EVP_DigestUpdate(kctx->ctx, data, datalen);
 203 }
 204
 205 static int kmac_final(EVP_MAC_IMPL *kctx, unsigned char *out)
 206 {
 207     EVP_MD_CTX *ctx = kctx->ctx;
 208     int lbits, len;
 209     unsigned char encoded_outlen[KMAC_MAX_ENCODED_HEADER_LEN];
 210
 211     /* KMAC XOF mode sets the encoded length to 0 */
 212     lbits = (kctx->xof_mode ? 0 : (kctx->out_len * 8));
 213
 214     return right_encode(encoded_outlen, &len, lbits)
 215            && EVP_DigestUpdate(ctx, encoded_outlen, len)
 216            && EVP_DigestFinalXOF(ctx, out, kctx->out_len);
 217 }
 218
 219 /*
 220  * The following Ctrl functions can be set any time before final():
 221  *     - EVP_MAC_CTRL_SET_SIZE: The requested output length.
 222  *     - EVP_MAC_CTRL_SET_XOF: If set, this indicates that right_encoded(0) is
 223  *                             part of the digested data, otherwise it uses
 224  *                             right_encoded(requested output length).
 225
 226  * All other Ctrl functions should be set before init().
 227  */
 228 static int kmac_ctrl(EVP_MAC_IMPL *kctx, int cmd, va_list args)
 229 {
 230     const unsigned char *p;
 231     size_t len;
 232     size_t size;
 233
 234     switch (cmd) {
 235     case EVP_MAC_CTRL_SET_XOF:
 236         kctx->xof_mode = va_arg(args, int);
 237         return 1;
 238
 239     case EVP_MAC_CTRL_SET_SIZE:
 240         size = va_arg(args, size_t);
 241         kctx->out_len = size;
 242         return 1;
 243
 244     case EVP_MAC_CTRL_SET_KEY:
 245         p = va_arg(args, const unsigned char *);
 246         len = va_arg(args, size_t);
 247         if (len < 4 || len > KMAC_MAX_KEY) {
 248             EVPerr(EVP_F_KMAC_CTRL, EVP_R_INVALID_KEY_LENGTH);
 249             return 0;
 250         }
 251         return kmac_bytepad_encode_key(kctx->key, &kctx->key_len, p, len,
 252                                        EVP_MD_block_size(kctx->md));
 253
 254     case EVP_MAC_CTRL_SET_CUSTOM:
 255         p = va_arg(args, const unsigned char *);
 256         len = va_arg(args, size_t);
 257         if (len > KMAC_MAX_CUSTOM) {
 258             EVPerr(EVP_F_KMAC_CTRL, EVP_R_INVALID_CUSTOM_LENGTH);
 259             return 0;
 260         }
 261         return encode_string(kctx->custom, &kctx->custom_len, p, len);
 262
 263     default:
 264         return -2;
 265     }
 266 }
 267
 268 static int kmac_ctrl_int(EVP_MAC_IMPL *kctx, int cmd, ...)
 269 {
 270     int rv;
 271     va_list args;
 272
 273     va_start(args, cmd);
 274     rv = kmac_ctrl(kctx, cmd, args);
 275     va_end(args);
 276
 277     return rv;
 278 }
 279
 280 static int kmac_ctrl_str_cb(void *kctx, int cmd, void *buf, size_t buflen)
 281 {
 282     return kmac_ctrl_int(kctx, cmd, buf, buflen);
 283 }
 284
 285 static int kmac_ctrl_str(EVP_MAC_IMPL *kctx, const char *type,
 286                          const char *value)
 287 {
 288     if (value == NULL)
 289         return 0;
 290
 291     if (strcmp(type, "outlen") == 0)
 292         return kmac_ctrl_int(kctx, EVP_MAC_CTRL_SET_SIZE, (size_t)atoi(value));
 293     if (strcmp(type, "xof") == 0)
 294         return kmac_ctrl_int(kctx, EVP_MAC_CTRL_SET_XOF, atoi(value));
 295     if (strcmp(type, "key") == 0)
 296         return EVP_str2ctrl(kmac_ctrl_str_cb, kctx, EVP_MAC_CTRL_SET_KEY,
 297                             value);
 298     if (strcmp(type, "hexkey") == 0)
 299         return EVP_hex2ctrl(kmac_ctrl_str_cb, kctx, EVP_MAC_CTRL_SET_KEY,
 300                             value);
 301     if (strcmp(type, "custom") == 0)
 302         return EVP_str2ctrl(kmac_ctrl_str_cb, kctx, EVP_MAC_CTRL_SET_CUSTOM,
 303                             value);
 304     if (strcmp(type, "hexcustom") == 0)
 305         return EVP_hex2ctrl(kmac_ctrl_str_cb, kctx, EVP_MAC_CTRL_SET_CUSTOM,
 306                             value);
 307     return -2;
 308 }
 309
 310 /*
 311  * Encoding/Padding Methods.
 312  */
 313
 314 /* Returns the number of bytes required to store 'bits' into a byte array */
 315 static unsigned int get_encode_size(size_t bits)
 316 {
 317     unsigned int cnt = 0, sz = sizeof(size_t);
 318
 319     while (bits && (cnt < sz)) {
 320         ++cnt;
 321         bits >>= 8;
 322     }
 323     /* If bits is zero 1 byte is required */
 324     if (cnt == 0)
 325         cnt = 1;
 326     return cnt;
 327 }
 328
 329 /*
 330  * Convert an integer into bytes . The number of bytes is appended
 331  * to the end of the buffer. Returns an array of bytes 'out' of size
 332  * *out_len.
 333  *
 334  * e.g if bits = 32, out[2] = { 0x20, 0x01 }
 335  *
 336  */
 337 static int right_encode(unsigned char *out, int *out_len, size_t bits)
 338 {
 339     unsigned int len = get_encode_size(bits);
 340     int i;
 341
 342     /* The length is constrained to a single byte: 2040/8 = 255 */
 343     if (len > 0xFF)
 344         return 0;
 345
 346     /* MSB's are at the start of the bytes array */
 347     for (i = len - 1; i >= 0; --i) {
 348         out[i] = (unsigned char)(bits & 0xFF);
 349         bits >>= 8;
 350     }
 351     /* Tack the length onto the end */
 352     out[len] = (unsigned char)len;
 353
 354     /* The Returned length includes the tacked on byte */
 355     *out_len = len + 1;
 356     return 1;
 357 }
 358
 359 /*
 360  * Encodes a string with a left encoded length added. Note that the
 361  * in_len is converted to bits (*8).
 362  *
 363  * e.g- in="KMAC" gives out[6] = { 0x01, 0x20, 0x4B, 0x4D, 0x41, 0x43 }
 364  *                                 len   bits    K     M     A     C
 365  */
 366 static int encode_string(unsigned char *out, int *out_len,
 367                          const unsigned char *in, int in_len)
 368 {
 369     if (in == NULL) {
 370         *out_len = 0;
 371     } else {
 372         int i, bits, len;
 373
 374         bits = 8 * in_len;
 375         len = get_encode_size(bits);
 376         if (len > 0xFF)
 377             return 0;
 378
 379         out[0] = len;
 380         for (i = len; i > 0; --i) {
 381             out[i] = (bits & 0xFF);
 382             bits >>= 8;
 383         }
 384         memcpy(out + len + 1, in, in_len);
 385         *out_len = (1 + len + in_len);
 386     }
 387     return 1;
 388 }
 389
 390 /*
 391  * Returns a zero padded encoding of the inputs in1 and an optional
 392  * in2 (can be NULL). The padded output must be a multiple of the blocksize 'w'.
 393  * The value of w is in bytes (< 256).
 394  *
 395  * The returned output is:
 396  *    zero_padded(multiple of w, (left_encode(w) || in1 [|| in2])
 397  */
 398 static int bytepad(unsigned char *out, int *out_len,
 399                    const unsigned char *in1, int in1_len,
 400                    const unsigned char *in2, int in2_len, int w)
 401 {
 402     int len;
 403     unsigned char *p = out;
 404     int sz = w;
 405
 406     /* Left encoded w */
 407     *p++ = 1;
 408     *p++ = w;
 409     /* || in1 */
 410     memcpy(p, in1, in1_len);
 411     p += in1_len;
 412     /* [ || in2 ] */
 413     if (in2 != NULL && in2_len > 0) {
 414         memcpy(p, in2, in2_len);
 415         p += in2_len;
 416     }
 417     /* Figure out the pad size (divisible by w) */
 418     len = p - out;
 419     while (len > sz) {
 420         sz += w;
 421     }
 422     /* zero pad the end of the buffer */
 423     memset(p, 0, sz - len);
 424     *out_len = sz;
 425     return 1;
 426 }
 427
 428 /*
 429  * Returns out = bytepad(encode_string(in), w)
 430  */
 431 static int kmac_bytepad_encode_key(unsigned char *out, int *out_len,
 432                                    const unsigned char *in, int in_len,
 433                                    int w)
 434 {
 435     unsigned char tmp[KMAC_MAX_KEY + KMAC_MAX_ENCODED_HEADER_LEN];
 436     int tmp_len;
 437
 438     if (!encode_string(tmp, &tmp_len, in, in_len))
 439         return 0;
 440
 441     return bytepad(out, out_len, tmp, tmp_len, NULL, 0, w);
 442 }
 443
 444 const EVP_MAC kmac128_meth = {
 445     EVP_MAC_KMAC128,
 446     kmac128_new,
 447     kmac_copy,
 448     kmac_free,
 449     kmac_size,
 450     kmac_init,
 451     kmac_update,
 452     kmac_final,
 453     kmac_ctrl,
 454     kmac_ctrl_str
 455 };
 456
 457 const EVP_MAC kmac256_meth = {
 458     EVP_MAC_KMAC256,
 459     kmac256_new,
 460     kmac_copy,
 461     kmac_free,
 462     kmac_size,
 463     kmac_init,
 464     kmac_update,
 465     kmac_final,
 466     kmac_ctrl,
 467     kmac_ctrl_str
 468 };
 469