crypto/kdf/hkdf.c

   1 /*
   2  * Copyright 2016-2018 The OpenSSL Project Authors. All Rights Reserved.
   3  *
   4  * Licensed under the Apache License 2.0 (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 #include <stdlib.h>
  11 #include <stdarg.h>
  12 #include <string.h>
  13 #include <openssl/hmac.h>
  14 #include <openssl/evp.h>
  15 #include <openssl/kdf.h>
  16 #include "internal/cryptlib.h"
  17 #include "internal/numbers.h"
  18 #include "internal/evp_int.h"
  19 #include "kdf_local.h"
  20
  21 #define HKDF_MAXBUF 1024
  22
  23 static void kdf_hkdf_reset(EVP_KDF_IMPL *impl);
  24 static int HKDF(const EVP_MD *evp_md,
  25                 const unsigned char *salt, size_t salt_len,
  26                 const unsigned char *key, size_t key_len,
  27                 const unsigned char *info, size_t info_len,
  28                 unsigned char *okm, size_t okm_len);
  29 static int HKDF_Extract(const EVP_MD *evp_md,
  30                         const unsigned char *salt, size_t salt_len,
  31                         const unsigned char *key, size_t key_len,
  32                         unsigned char *prk, size_t prk_len);
  33 static int HKDF_Expand(const EVP_MD *evp_md,
  34                        const unsigned char *prk, size_t prk_len,
  35                        const unsigned char *info, size_t info_len,
  36                        unsigned char *okm, size_t okm_len);
  37
  38 struct evp_kdf_impl_st {
  39     int mode;
  40     const EVP_MD *md;
  41     unsigned char *salt;
  42     size_t salt_len;
  43     unsigned char *key;
  44     size_t key_len;
  45     unsigned char info[HKDF_MAXBUF];
  46     size_t info_len;
  47 };
  48
  49 static EVP_KDF_IMPL *kdf_hkdf_new(void)
  50 {
  51     EVP_KDF_IMPL *impl;
  52
  53     if ((impl = OPENSSL_zalloc(sizeof(*impl))) == NULL)
  54         KDFerr(KDF_F_KDF_HKDF_NEW, ERR_R_MALLOC_FAILURE);
  55     return impl;
  56 }
  57
  58 static void kdf_hkdf_free(EVP_KDF_IMPL *impl)
  59 {
  60     kdf_hkdf_reset(impl);
  61     OPENSSL_free(impl);
  62 }
  63
  64 static void kdf_hkdf_reset(EVP_KDF_IMPL *impl)
  65 {
  66     OPENSSL_free(impl->salt);
  67     OPENSSL_clear_free(impl->key, impl->key_len);
  68     OPENSSL_cleanse(impl->info, impl->info_len);
  69     memset(impl, 0, sizeof(*impl));
  70 }
  71
  72 static int kdf_hkdf_ctrl(EVP_KDF_IMPL *impl, int cmd, va_list args)
  73 {
  74     const unsigned char *p;
  75     size_t len;
  76     const EVP_MD *md;
  77
  78     switch (cmd) {
  79     case EVP_KDF_CTRL_SET_MD:
  80         md = va_arg(args, const EVP_MD *);
  81         if (md == NULL)
  82             return 0;
  83
  84         impl->md = md;
  85         return 1;
  86
  87     case EVP_KDF_CTRL_SET_HKDF_MODE:
  88         impl->mode = va_arg(args, int);
  89         return 1;
  90
  91     case EVP_KDF_CTRL_SET_SALT:
  92         p = va_arg(args, const unsigned char *);
  93         len = va_arg(args, size_t);
  94         if (len == 0 || p == NULL)
  95             return 1;
  96
  97         OPENSSL_free(impl->salt);
  98         impl->salt = OPENSSL_memdup(p, len);
  99         if (impl->salt == NULL)
 100             return 0;
 101
 102         impl->salt_len = len;
 103         return 1;
 104
 105     case EVP_KDF_CTRL_SET_KEY:
 106         p = va_arg(args, const unsigned char *);
 107         len = va_arg(args, size_t);
 108         OPENSSL_clear_free(impl->key, impl->key_len);
 109         impl->key = OPENSSL_memdup(p, len);
 110         if (impl->key == NULL)
 111             return 0;
 112
 113         impl->key_len  = len;
 114         return 1;
 115
 116     case EVP_KDF_CTRL_RESET_HKDF_INFO:
 117         OPENSSL_cleanse(impl->info, impl->info_len);
 118         impl->info_len = 0;
 119         return 1;
 120
 121     case EVP_KDF_CTRL_ADD_HKDF_INFO:
 122         p = va_arg(args, const unsigned char *);
 123         len = va_arg(args, size_t);
 124         if (len == 0 || p == NULL)
 125             return 1;
 126
 127         if (len > (HKDF_MAXBUF - impl->info_len))
 128             return 0;
 129
 130         memcpy(impl->info + impl->info_len, p, len);
 131         impl->info_len += len;
 132         return 1;
 133
 134     default:
 135         return -2;
 136     }
 137 }
 138
 139 static int kdf_hkdf_ctrl_str(EVP_KDF_IMPL *impl, const char *type,
 140                              const char *value)
 141 {
 142     if (strcmp(type, "mode") == 0) {
 143         int mode;
 144
 145         if (strcmp(value, "EXTRACT_AND_EXPAND") == 0)
 146             mode = EVP_KDF_HKDF_MODE_EXTRACT_AND_EXPAND;
 147         else if (strcmp(value, "EXTRACT_ONLY") == 0)
 148             mode = EVP_KDF_HKDF_MODE_EXTRACT_ONLY;
 149         else if (strcmp(value, "EXPAND_ONLY") == 0)
 150             mode = EVP_KDF_HKDF_MODE_EXPAND_ONLY;
 151         else
 152             return 0;
 153
 154         return call_ctrl(kdf_hkdf_ctrl, impl, EVP_KDF_CTRL_SET_HKDF_MODE, mode);
 155     }
 156
 157     if (strcmp(type, "digest") == 0)
 158         return kdf_md2ctrl(impl, kdf_hkdf_ctrl, EVP_KDF_CTRL_SET_MD, value);
 159
 160     if (strcmp(type, "salt") == 0)
 161         return kdf_str2ctrl(impl, kdf_hkdf_ctrl, EVP_KDF_CTRL_SET_SALT, value);
 162
 163     if (strcmp(type, "hexsalt") == 0)
 164         return kdf_hex2ctrl(impl, kdf_hkdf_ctrl, EVP_KDF_CTRL_SET_SALT, value);
 165
 166     if (strcmp(type, "key") == 0)
 167         return kdf_str2ctrl(impl, kdf_hkdf_ctrl, EVP_KDF_CTRL_SET_KEY, value);
 168
 169     if (strcmp(type, "hexkey") == 0)
 170         return kdf_hex2ctrl(impl, kdf_hkdf_ctrl, EVP_KDF_CTRL_SET_KEY, value);
 171
 172     if (strcmp(type, "info") == 0)
 173         return kdf_str2ctrl(impl, kdf_hkdf_ctrl, EVP_KDF_CTRL_ADD_HKDF_INFO,
 174                             value);
 175
 176     if (strcmp(type, "hexinfo") == 0)
 177         return kdf_hex2ctrl(impl, kdf_hkdf_ctrl, EVP_KDF_CTRL_ADD_HKDF_INFO,
 178                             value);
 179
 180     return -2;
 181 }
 182
 183 static size_t kdf_hkdf_size(EVP_KDF_IMPL *impl)
 184 {
 185     int sz;
 186
 187     if (impl->mode != EVP_KDF_HKDF_MODE_EXTRACT_ONLY)
 188         return SIZE_MAX;
 189
 190     if (impl->md == NULL) {
 191         KDFerr(KDF_F_KDF_HKDF_SIZE, KDF_R_MISSING_MESSAGE_DIGEST);
 192         return 0;
 193     }
 194     sz = EVP_MD_size(impl->md);
 195     if (sz < 0)
 196         return 0;
 197
 198     return sz;
 199 }
 200
 201 static int kdf_hkdf_derive(EVP_KDF_IMPL *impl, unsigned char *key,
 202                            size_t keylen)
 203 {
 204     if (impl->md == NULL) {
 205         KDFerr(KDF_F_KDF_HKDF_DERIVE, KDF_R_MISSING_MESSAGE_DIGEST);
 206         return 0;
 207     }
 208     if (impl->key == NULL) {
 209         KDFerr(KDF_F_KDF_HKDF_DERIVE, KDF_R_MISSING_KEY);
 210         return 0;
 211     }
 212
 213     switch (impl->mode) {
 214     case EVP_KDF_HKDF_MODE_EXTRACT_AND_EXPAND:
 215         return HKDF(impl->md, impl->salt, impl->salt_len, impl->key,
 216                     impl->key_len, impl->info, impl->info_len, key,
 217                     keylen);
 218
 219     case EVP_KDF_HKDF_MODE_EXTRACT_ONLY:
 220         return HKDF_Extract(impl->md, impl->salt, impl->salt_len, impl->key,
 221                             impl->key_len, key, keylen);
 222
 223     case EVP_KDF_HKDF_MODE_EXPAND_ONLY:
 224         return HKDF_Expand(impl->md, impl->key, impl->key_len, impl->info,
 225                            impl->info_len, key, keylen);
 226
 227     default:
 228         return 0;
 229     }
 230 }
 231
 232 const EVP_KDF_METHOD hkdf_kdf_meth = {
 233     EVP_KDF_HKDF,
 234     kdf_hkdf_new,
 235     kdf_hkdf_free,
 236     kdf_hkdf_reset,
 237     kdf_hkdf_ctrl,
 238     kdf_hkdf_ctrl_str,
 239     kdf_hkdf_size,
 240     kdf_hkdf_derive
 241 };
 242
 243 static int HKDF(const EVP_MD *evp_md,
 244                 const unsigned char *salt, size_t salt_len,
 245                 const unsigned char *key, size_t key_len,
 246                 const unsigned char *info, size_t info_len,
 247                 unsigned char *okm, size_t okm_len)
 248 {
 249     unsigned char prk[EVP_MAX_MD_SIZE];
 250     int ret, sz;
 251     size_t prk_len;
 252
 253     sz = EVP_MD_size(evp_md);
 254     if (sz < 0)
 255         return 0;
 256     prk_len = (size_t)sz;
 257
 258     if (!HKDF_Extract(evp_md, salt, salt_len, key, key_len, prk, prk_len))
 259         return 0;
 260
 261     ret = HKDF_Expand(evp_md, prk, prk_len, info, info_len, okm, okm_len);
 262     OPENSSL_cleanse(prk, sizeof(prk));
 263
 264     return ret;
 265 }
 266
 267 static int HKDF_Extract(const EVP_MD *evp_md,
 268                         const unsigned char *salt, size_t salt_len,
 269                         const unsigned char *key, size_t key_len,
 270                         unsigned char *prk, size_t prk_len)
 271 {
 272     int sz = EVP_MD_size(evp_md);
 273
 274     if (sz < 0)
 275         return 0;
 276     if (prk_len != (size_t)sz) {
 277         KDFerr(KDF_F_HKDF_EXTRACT, KDF_R_WRONG_OUTPUT_BUFFER_SIZE);
 278         return 0;
 279     }
 280     return HMAC(evp_md, salt, salt_len, key, key_len, prk, NULL) != NULL;
 281 }
 282
 283 static int HKDF_Expand(const EVP_MD *evp_md,
 284                        const unsigned char *prk, size_t prk_len,
 285                        const unsigned char *info, size_t info_len,
 286                        unsigned char *okm, size_t okm_len)
 287 {
 288     HMAC_CTX *hmac;
 289     int ret = 0, sz;
 290     unsigned int i;
 291     unsigned char prev[EVP_MAX_MD_SIZE];
 292     size_t done_len = 0, dig_len, n;
 293
 294     sz = EVP_MD_size(evp_md);
 295     if (sz <= 0)
 296         return 0;
 297     dig_len = (size_t)sz;
 298     n = okm_len / dig_len;
 299
 300     if (okm_len % dig_len)
 301         n++;
 302
 303     if (n > 255 || okm == NULL)
 304         return 0;
 305
 306     if ((hmac = HMAC_CTX_new()) == NULL)
 307         return 0;
 308
 309     if (!HMAC_Init_ex(hmac, prk, prk_len, evp_md, NULL))
 310         goto err;
 311
 312     for (i = 1; i <= n; i++) {
 313         size_t copy_len;
 314         const unsigned char ctr = i;
 315
 316         if (i > 1) {
 317             if (!HMAC_Init_ex(hmac, NULL, 0, NULL, NULL))
 318                 goto err;
 319
 320             if (!HMAC_Update(hmac, prev, dig_len))
 321                 goto err;
 322         }
 323
 324         if (!HMAC_Update(hmac, info, info_len))
 325             goto err;
 326
 327         if (!HMAC_Update(hmac, &ctr, 1))
 328             goto err;
 329
 330         if (!HMAC_Final(hmac, prev, NULL))
 331             goto err;
 332
 333         copy_len = (done_len + dig_len > okm_len) ?
 334                        okm_len - done_len :
 335                        dig_len;
 336
 337         memcpy(okm + done_len, prev, copy_len);
 338
 339         done_len += copy_len;
 340     }
 341     ret = 1;
 342
 343  err:
 344     OPENSSL_cleanse(prev, sizeof(prev));
 345     HMAC_CTX_free(hmac);
 346     return ret;
 347 }