/*
* Copyright 2016 The OpenSSL Project Authors. All Rights Reserved.
*
* Licensed under the OpenSSL license (the "License"). You may not use
* this file except in compliance with the License. You can obtain a copy
* in the file LICENSE in the source distribution or at
* https://www.openssl.org/source/license.html
*/
#include <stdlib.h>
#include <string.h>
#include <openssl/hmac.h>
#include <openssl/kdf.h>
#include <openssl/evp.h>
#include "internal/cryptlib.h"
#include "internal/evp_int.h"
#define HKDF_MAXBUF 1024
static unsigned char *HKDF(const EVP_MD *evp_md,
const unsigned char *salt, size_t salt_len,
const unsigned char *key, size_t key_len,
const unsigned char *info, size_t info_len,
unsigned char *okm, size_t okm_len);
static unsigned char *HKDF_Extract(const EVP_MD *evp_md,
const unsigned char *salt, size_t salt_len,
const unsigned char *key, size_t key_len,
unsigned char *prk, size_t *prk_len);
static unsigned char *HKDF_Expand(const EVP_MD *evp_md,
const unsigned char *prk, size_t prk_len,
const unsigned char *info, size_t info_len,
unsigned char *okm, size_t okm_len);
typedef struct {
const EVP_MD *md;
unsigned char *salt;
size_t salt_len;
unsigned char *key;
size_t key_len;
unsigned char info[HKDF_MAXBUF];
size_t info_len;
} HKDF_PKEY_CTX;
static int pkey_hkdf_init(EVP_PKEY_CTX *ctx)
{
HKDF_PKEY_CTX *kctx;
kctx = OPENSSL_zalloc(sizeof(*kctx));
if (kctx == NULL)
return 0;
ctx->data = kctx;
return 1;
}
static void pkey_hkdf_cleanup(EVP_PKEY_CTX *ctx)
{
HKDF_PKEY_CTX *kctx = ctx->data;
OPENSSL_clear_free(kctx->salt, kctx->salt_len);
OPENSSL_clear_free(kctx->key, kctx->key_len);
OPENSSL_cleanse(kctx->info, kctx->info_len);
OPENSSL_free(kctx);
}
static int pkey_hkdf_ctrl(EVP_PKEY_CTX *ctx, int type, int p1, void *p2)
{
HKDF_PKEY_CTX *kctx = ctx->data;
switch (type) {
case EVP_PKEY_CTRL_HKDF_MD:
if (p2 == NULL)
return 0;
kctx->md = p2;
return 1;
case EVP_PKEY_CTRL_HKDF_SALT:
if (p1 == 0 || p2 == NULL)
return 1;
if (p1 < 0)
return 0;
if (kctx->salt != NULL)
OPENSSL_clear_free(kctx->salt, kctx->salt_len);
kctx->salt = OPENSSL_memdup(p2, p1);
if (kctx->salt == NULL)
return 0;
kctx->salt_len = p1;
return 1;
case EVP_PKEY_CTRL_HKDF_KEY:
if (p1 < 0)
return 0;
if (kctx->key != NULL)
OPENSSL_clear_free(kctx->key, kctx->key_len);
kctx->key = OPENSSL_memdup(p2, p1);
if (kctx->key == NULL)
return 0;
kctx->key_len = p1;
return 1;
case EVP_PKEY_CTRL_HKDF_INFO:
if (p1 == 0 || p2 == NULL)
return 1;
if (p1 < 0 || p1 > (int)(HKDF_MAXBUF - kctx->info_len))
return 0;
memcpy(kctx->info + kctx->info_len, p2, p1);
kctx->info_len += p1;
return 1;
default:
return -2;
}
}
static int pkey_hkdf_ctrl_str(EVP_PKEY_CTX *ctx, const char *type,
const char *value)
{
if (strcmp(type, "md") == 0)
return EVP_PKEY_CTX_set_hkdf_md(ctx, EVP_get_digestbyname(value));
if (strcmp(type, "salt") == 0)
return EVP_PKEY_CTX_str2ctrl(ctx, EVP_PKEY_CTRL_HKDF_SALT, value);
if (strcmp(type, "hexsalt") == 0)
return EVP_PKEY_CTX_hex2ctrl(ctx, EVP_PKEY_CTRL_HKDF_SALT, value);
if (strcmp(type, "key") == 0)
return EVP_PKEY_CTX_str2ctrl(ctx, EVP_PKEY_CTRL_HKDF_KEY, value);
if (strcmp(type, "hexkey") == 0)
return EVP_PKEY_CTX_hex2ctrl(ctx, EVP_PKEY_CTRL_HKDF_KEY, value);
if (strcmp(type, "info") == 0)
return EVP_PKEY_CTX_str2ctrl(ctx, EVP_PKEY_CTRL_HKDF_INFO, value);
if (strcmp(type, "hexinfo") == 0)
return EVP_PKEY_CTX_hex2ctrl(ctx, EVP_PKEY_CTRL_HKDF_INFO, value);
return -2;
}
static int pkey_hkdf_derive(EVP_PKEY_CTX *ctx, unsigned char *key,
size_t *keylen)
{
HKDF_PKEY_CTX *kctx = ctx->data;
if (kctx->md == NULL || kctx->key == NULL)
return 0;
if (HKDF(kctx->md, kctx->salt, kctx->salt_len, kctx->key, kctx->key_len,
kctx->info, kctx->info_len, key, *keylen) == NULL)
{
return 0;
}
return 1;
}
const EVP_PKEY_METHOD hkdf_pkey_meth = {
EVP_PKEY_HKDF,
0,
pkey_hkdf_init,
0,
pkey_hkdf_cleanup,
0, 0,
0, 0,
0,
0,
0,
0,
0, 0,
0, 0, 0, 0,
0, 0,
0, 0,
0,
pkey_hkdf_derive,
pkey_hkdf_ctrl,
pkey_hkdf_ctrl_str
};
static unsigned char *HKDF(const EVP_MD *evp_md,
const unsigned char *salt, size_t salt_len,
const unsigned char *key, size_t key_len,
const unsigned char *info, size_t info_len,
unsigned char *okm, size_t okm_len)
{
unsigned char prk[EVP_MAX_MD_SIZE];
size_t prk_len;
if (!HKDF_Extract(evp_md, salt, salt_len, key, key_len, prk, &prk_len))
return NULL;
return HKDF_Expand(evp_md, prk, prk_len, info, info_len, okm, okm_len);
}
static unsigned char *HKDF_Extract(const EVP_MD *evp_md,
const unsigned char *salt, size_t salt_len,
const unsigned char *key, size_t key_len,
unsigned char *prk, size_t *prk_len)
{
unsigned int tmp_len;
if (!HMAC(evp_md, salt, salt_len, key, key_len, prk, &tmp_len))
return NULL;
*prk_len = tmp_len;
return prk;
}
static unsigned char *HKDF_Expand(const EVP_MD *evp_md,
const unsigned char *prk, size_t prk_len,
const unsigned char *info, size_t info_len,
unsigned char *okm, size_t okm_len)
{
HMAC_CTX *hmac;
unsigned int i;
unsigned char prev[EVP_MAX_MD_SIZE];
size_t done_len = 0, dig_len = EVP_MD_size(evp_md);
size_t n = okm_len / dig_len;
if (okm_len % dig_len)
n++;
if (n > 255)
return NULL;
if ((hmac = HMAC_CTX_new()) == NULL)
return NULL;
if (!HMAC_Init_ex(hmac, prk, prk_len, evp_md, NULL))
goto err;
for (i = 1; i <= n; i++) {
size_t copy_len;
const unsigned char ctr = i;
if (i > 1) {
if (!HMAC_Init_ex(hmac, NULL, 0, NULL, NULL))
goto err;
if (!HMAC_Update(hmac, prev, dig_len))
goto err;
}
if (!HMAC_Update(hmac, info, info_len))
goto err;
if (!HMAC_Update(hmac, &ctr, 1))
goto err;
if (!HMAC_Final(hmac, prev, NULL))
goto err;
copy_len = (done_len + dig_len > okm_len) ?
okm_len - done_len :
dig_len;
memcpy(okm + done_len, prev, copy_len);
done_len += copy_len;
}
HMAC_CTX_free(hmac);
return okm;
err:
HMAC_CTX_free(hmac);
return NULL;
}
