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