crypto/kdf/hkdf.c

   1 /*
   2  * Copyright 2016-2018 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 #include <stdlib.h>
  11 #include <string.h>
  12 #include <openssl/hmac.h>
  13 #include <openssl/kdf.h>
  14 #include <openssl/evp.h>
  15 #include "internal/cryptlib.h"
  16 #include "internal/evp_int.h"
  17
  18 #define HKDF_MAXBUF 1024
  19
  20 static unsigned char *HKDF(const EVP_MD *evp_md,
  21                            const unsigned char *salt, size_t salt_len,
  22                            const unsigned char *key, size_t key_len,
  23                            const unsigned char *info, size_t info_len,
  24                            unsigned char *okm, size_t okm_len);
  25
  26 static unsigned char *HKDF_Extract(const EVP_MD *evp_md,
  27                                    const unsigned char *salt, size_t salt_len,
  28                                    const unsigned char *key, size_t key_len,
  29                                    unsigned char *prk, size_t *prk_len);
  30
  31 static unsigned char *HKDF_Expand(const EVP_MD *evp_md,
  32                                   const unsigned char *prk, size_t prk_len,
  33                                   const unsigned char *info, size_t info_len,
  34                                   unsigned char *okm, size_t okm_len);
  35
  36 typedef struct {
  37     int mode;
  38     const EVP_MD *md;
  39     unsigned char *salt;
  40     size_t salt_len;
  41     unsigned char *key;
  42     size_t key_len;
  43     unsigned char info[HKDF_MAXBUF];
  44     size_t info_len;
  45 } HKDF_PKEY_CTX;
  46
  47 static int pkey_hkdf_init(EVP_PKEY_CTX *ctx)
  48 {
  49     HKDF_PKEY_CTX *kctx;
  50
  51     if ((kctx = OPENSSL_zalloc(sizeof(*kctx))) == NULL) {
  52         KDFerr(KDF_F_PKEY_HKDF_INIT, ERR_R_MALLOC_FAILURE);
  53         return 0;
  54     }
  55
  56     ctx->data = kctx;
  57
  58     return 1;
  59 }
  60
  61 static void pkey_hkdf_cleanup(EVP_PKEY_CTX *ctx)
  62 {
  63     HKDF_PKEY_CTX *kctx = ctx->data;
  64     OPENSSL_clear_free(kctx->salt, kctx->salt_len);
  65     OPENSSL_clear_free(kctx->key, kctx->key_len);
  66     OPENSSL_cleanse(kctx->info, kctx->info_len);
  67     OPENSSL_free(kctx);
  68 }
  69
  70 static int pkey_hkdf_ctrl(EVP_PKEY_CTX *ctx, int type, int p1, void *p2)
  71 {
  72     HKDF_PKEY_CTX *kctx = ctx->data;
  73
  74     switch (type) {
  75     case EVP_PKEY_CTRL_HKDF_MD:
  76         if (p2 == NULL)
  77             return 0;
  78
  79         kctx->md = p2;
  80         return 1;
  81
  82     case EVP_PKEY_CTRL_HKDF_MODE:
  83         kctx->mode = p1;
  84         return 1;
  85
  86     case EVP_PKEY_CTRL_HKDF_SALT:
  87         if (p1 == 0 || p2 == NULL)
  88             return 1;
  89
  90         if (p1 < 0)
  91             return 0;
  92
  93         if (kctx->salt != NULL)
  94             OPENSSL_clear_free(kctx->salt, kctx->salt_len);
  95
  96         kctx->salt = OPENSSL_memdup(p2, p1);
  97         if (kctx->salt == NULL)
  98             return 0;
  99
 100         kctx->salt_len = p1;
 101         return 1;
 102
 103     case EVP_PKEY_CTRL_HKDF_KEY:
 104         if (p1 < 0)
 105             return 0;
 106
 107         if (kctx->key != NULL)
 108             OPENSSL_clear_free(kctx->key, kctx->key_len);
 109
 110         kctx->key = OPENSSL_memdup(p2, p1);
 111         if (kctx->key == NULL)
 112             return 0;
 113
 114         kctx->key_len  = p1;
 115         return 1;
 116
 117     case EVP_PKEY_CTRL_HKDF_INFO:
 118         if (p1 == 0 || p2 == NULL)
 119             return 1;
 120
 121         if (p1 < 0 || p1 > (int)(HKDF_MAXBUF - kctx->info_len))
 122             return 0;
 123
 124         memcpy(kctx->info + kctx->info_len, p2, p1);
 125         kctx->info_len += p1;
 126         return 1;
 127
 128     default:
 129         return -2;
 130
 131     }
 132 }
 133
 134 static int pkey_hkdf_ctrl_str(EVP_PKEY_CTX *ctx, const char *type,
 135                               const char *value)
 136 {
 137     if (strcmp(type, "mode") == 0) {
 138         int mode;
 139
 140         if (strcmp(value, "EXTRACT_AND_EXPAND") == 0)
 141             mode = EVP_PKEY_HKDEF_MODE_EXTRACT_AND_EXPAND;
 142         else if (strcmp(value, "EXTRACT_ONLY") == 0)
 143             mode = EVP_PKEY_HKDEF_MODE_EXTRACT_ONLY;
 144         else if (strcmp(value, "EXPAND_ONLY") == 0)
 145             mode = EVP_PKEY_HKDEF_MODE_EXPAND_ONLY;
 146         else
 147             return 0;
 148
 149         return EVP_PKEY_CTX_hkdf_mode(ctx, mode);
 150     }
 151
 152     if (strcmp(type, "md") == 0)
 153         return EVP_PKEY_CTX_md(ctx, EVP_PKEY_OP_DERIVE,
 154                                EVP_PKEY_CTRL_HKDF_MD, value);
 155
 156     if (strcmp(type, "salt") == 0)
 157         return EVP_PKEY_CTX_str2ctrl(ctx, EVP_PKEY_CTRL_HKDF_SALT, value);
 158
 159     if (strcmp(type, "hexsalt") == 0)
 160         return EVP_PKEY_CTX_hex2ctrl(ctx, EVP_PKEY_CTRL_HKDF_SALT, value);
 161
 162     if (strcmp(type, "key") == 0)
 163         return EVP_PKEY_CTX_str2ctrl(ctx, EVP_PKEY_CTRL_HKDF_KEY, value);
 164
 165     if (strcmp(type, "hexkey") == 0)
 166         return EVP_PKEY_CTX_hex2ctrl(ctx, EVP_PKEY_CTRL_HKDF_KEY, value);
 167
 168     if (strcmp(type, "info") == 0)
 169         return EVP_PKEY_CTX_str2ctrl(ctx, EVP_PKEY_CTRL_HKDF_INFO, value);
 170
 171     if (strcmp(type, "hexinfo") == 0)
 172         return EVP_PKEY_CTX_hex2ctrl(ctx, EVP_PKEY_CTRL_HKDF_INFO, value);
 173
 174     KDFerr(KDF_F_PKEY_HKDF_CTRL_STR, KDF_R_UNKNOWN_PARAMETER_TYPE);
 175     return -2;
 176 }
 177
 178 static int pkey_hkdf_derive_init(EVP_PKEY_CTX *ctx)
 179 {
 180     HKDF_PKEY_CTX *kctx = ctx->data;
 181
 182     OPENSSL_clear_free(kctx->key, kctx->key_len);
 183     OPENSSL_clear_free(kctx->salt, kctx->salt_len);
 184     OPENSSL_cleanse(kctx->info, kctx->info_len);
 185     memset(kctx, 0, sizeof(*kctx));
 186
 187     return 1;
 188 }
 189
 190 static int pkey_hkdf_derive(EVP_PKEY_CTX *ctx, unsigned char *key,
 191                             size_t *keylen)
 192 {
 193     HKDF_PKEY_CTX *kctx = ctx->data;
 194
 195     if (kctx->md == NULL) {
 196         KDFerr(KDF_F_PKEY_HKDF_DERIVE, KDF_R_MISSING_MESSAGE_DIGEST);
 197         return 0;
 198     }
 199     if (kctx->key == NULL) {
 200         KDFerr(KDF_F_PKEY_HKDF_DERIVE, KDF_R_MISSING_KEY);
 201         return 0;
 202     }
 203
 204     switch (kctx->mode) {
 205     case EVP_PKEY_HKDEF_MODE_EXTRACT_AND_EXPAND:
 206         return HKDF(kctx->md, kctx->salt, kctx->salt_len, kctx->key,
 207                     kctx->key_len, kctx->info, kctx->info_len, key,
 208                     *keylen) != NULL;
 209
 210     case EVP_PKEY_HKDEF_MODE_EXTRACT_ONLY:
 211         if (key == NULL) {
 212             *keylen = EVP_MD_size(kctx->md);
 213             return 1;
 214         }
 215         return HKDF_Extract(kctx->md, kctx->salt, kctx->salt_len, kctx->key,
 216                             kctx->key_len, key, keylen) != NULL;
 217
 218     case EVP_PKEY_HKDEF_MODE_EXPAND_ONLY:
 219         return HKDF_Expand(kctx->md, kctx->key, kctx->key_len, kctx->info,
 220                            kctx->info_len, key, *keylen) != NULL;
 221
 222     default:
 223         return 0;
 224     }
 225 }
 226
 227 const EVP_PKEY_METHOD hkdf_pkey_meth = {
 228     EVP_PKEY_HKDF,
 229     0,
 230     pkey_hkdf_init,
 231     0,
 232     pkey_hkdf_cleanup,
 233
 234     0, 0,
 235     0, 0,
 236
 237     0,
 238     0,
 239
 240     0,
 241     0,
 242
 243     0, 0,
 244
 245     0, 0, 0, 0,
 246
 247     0, 0,
 248
 249     0, 0,
 250
 251     pkey_hkdf_derive_init,
 252     pkey_hkdf_derive,
 253     pkey_hkdf_ctrl,
 254     pkey_hkdf_ctrl_str
 255 };
 256
 257 static unsigned char *HKDF(const EVP_MD *evp_md,
 258                            const unsigned char *salt, size_t salt_len,
 259                            const unsigned char *key, size_t key_len,
 260                            const unsigned char *info, size_t info_len,
 261                            unsigned char *okm, size_t okm_len)
 262 {
 263     unsigned char prk[EVP_MAX_MD_SIZE];
 264     unsigned char *ret;
 265     size_t prk_len;
 266
 267     if (!HKDF_Extract(evp_md, salt, salt_len, key, key_len, prk, &prk_len))
 268         return NULL;
 269
 270     ret = HKDF_Expand(evp_md, prk, prk_len, info, info_len, okm, okm_len);
 271     OPENSSL_cleanse(prk, sizeof(prk));
 272
 273     return ret;
 274 }
 275
 276 static unsigned char *HKDF_Extract(const EVP_MD *evp_md,
 277                                    const unsigned char *salt, size_t salt_len,
 278                                    const unsigned char *key, size_t key_len,
 279                                    unsigned char *prk, size_t *prk_len)
 280 {
 281     unsigned int tmp_len;
 282
 283     if (!HMAC(evp_md, salt, salt_len, key, key_len, prk, &tmp_len))
 284         return NULL;
 285
 286     *prk_len = tmp_len;
 287     return prk;
 288 }
 289
 290 static unsigned char *HKDF_Expand(const EVP_MD *evp_md,
 291                                   const unsigned char *prk, size_t prk_len,
 292                                   const unsigned char *info, size_t info_len,
 293                                   unsigned char *okm, size_t okm_len)
 294 {
 295     HMAC_CTX *hmac;
 296     unsigned char *ret = NULL;
 297
 298     unsigned int i;
 299
 300     unsigned char prev[EVP_MAX_MD_SIZE];
 301
 302     size_t done_len = 0, dig_len = EVP_MD_size(evp_md);
 303
 304     size_t n = okm_len / dig_len;
 305     if (okm_len % dig_len)
 306         n++;
 307
 308     if (n > 255 || okm == NULL)
 309         return NULL;
 310
 311     if ((hmac = HMAC_CTX_new()) == NULL)
 312         return NULL;
 313
 314     if (!HMAC_Init_ex(hmac, prk, prk_len, evp_md, NULL))
 315         goto err;
 316
 317     for (i = 1; i <= n; i++) {
 318         size_t copy_len;
 319         const unsigned char ctr = i;
 320
 321         if (i > 1) {
 322             if (!HMAC_Init_ex(hmac, NULL, 0, NULL, NULL))
 323                 goto err;
 324
 325             if (!HMAC_Update(hmac, prev, dig_len))
 326                 goto err;
 327         }
 328
 329         if (!HMAC_Update(hmac, info, info_len))
 330             goto err;
 331
 332         if (!HMAC_Update(hmac, &ctr, 1))
 333             goto err;
 334
 335         if (!HMAC_Final(hmac, prev, NULL))
 336             goto err;
 337
 338         copy_len = (done_len + dig_len > okm_len) ?
 339                        okm_len - done_len :
 340                        dig_len;
 341
 342         memcpy(okm + done_len, prev, copy_len);
 343
 344         done_len += copy_len;
 345     }
 346     ret = okm;
 347
 348  err:
 349     OPENSSL_cleanse(prev, sizeof(prev));
 350     HMAC_CTX_free(hmac);
 351     return ret;
 352 }