[thirdparty/openssl.git] / crypto / kdf / hkdf.c

/*
 * Copyright 2016-2018 The OpenSSL Project Authors. All Rights Reserved.
 *
 * Licensed under the Apache License 2.0 (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 <stdarg.h>
#include <string.h>
#include <openssl/hmac.h>
#include <openssl/evp.h>
#include <openssl/kdf.h>
#include "internal/cryptlib.h"
#include "internal/numbers.h"
#include "internal/evp_int.h"
#include "kdf_local.h"

#define HKDF_MAXBUF 1024

static void kdf_hkdf_reset(EVP_KDF_IMPL *impl);
static int 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 int HKDF_Extract(const EVP_MD *evp_md,
                        const unsigned char *salt, size_t salt_len,
                        const unsigned char *ikm, size_t ikm_len,
                        unsigned char *prk, size_t prk_len);
static int 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);

struct evp_kdf_impl_st {
    int mode;
    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;
};

static EVP_KDF_IMPL *kdf_hkdf_new(void)
{
    EVP_KDF_IMPL *impl;

    if ((impl = OPENSSL_zalloc(sizeof(*impl))) == NULL)
        KDFerr(KDF_F_KDF_HKDF_NEW, ERR_R_MALLOC_FAILURE);
    return impl;
}

static void kdf_hkdf_free(EVP_KDF_IMPL *impl)
{
    kdf_hkdf_reset(impl);
    OPENSSL_free(impl);
}

static void kdf_hkdf_reset(EVP_KDF_IMPL *impl)
{
    OPENSSL_free(impl->salt);
    OPENSSL_clear_free(impl->key, impl->key_len);
    OPENSSL_cleanse(impl->info, impl->info_len);
    memset(impl, 0, sizeof(*impl));
}

static int kdf_hkdf_ctrl(EVP_KDF_IMPL *impl, int cmd, va_list args)
{
    const unsigned char *p;
    size_t len;
    const EVP_MD *md;

    switch (cmd) {
    case EVP_KDF_CTRL_SET_MD:
        md = va_arg(args, const EVP_MD *);
        if (md == NULL)
            return 0;

        impl->md = md;
        return 1;

    case EVP_KDF_CTRL_SET_HKDF_MODE:
        impl->mode = va_arg(args, int);
        return 1;

    case EVP_KDF_CTRL_SET_SALT:
        p = va_arg(args, const unsigned char *);
        len = va_arg(args, size_t);
        if (len == 0 || p == NULL)
            return 1;

        OPENSSL_free(impl->salt);
        impl->salt = OPENSSL_memdup(p, len);
        if (impl->salt == NULL)
            return 0;

        impl->salt_len = len;
        return 1;

    case EVP_KDF_CTRL_SET_KEY:
        p = va_arg(args, const unsigned char *);
        len = va_arg(args, size_t);
        OPENSSL_clear_free(impl->key, impl->key_len);
        impl->key = OPENSSL_memdup(p, len);
        if (impl->key == NULL)
            return 0;

        impl->key_len  = len;
        return 1;

    case EVP_KDF_CTRL_RESET_HKDF_INFO:
        OPENSSL_cleanse(impl->info, impl->info_len);
        impl->info_len = 0;
        return 1;

    case EVP_KDF_CTRL_ADD_HKDF_INFO:
        p = va_arg(args, const unsigned char *);
        len = va_arg(args, size_t);
        if (len == 0 || p == NULL)
            return 1;

        if (len > (HKDF_MAXBUF - impl->info_len))
            return 0;

        memcpy(impl->info + impl->info_len, p, len);
        impl->info_len += len;
        return 1;

    default:
        return -2;
    }
}

static int kdf_hkdf_ctrl_str(EVP_KDF_IMPL *impl, const char *type,
                             const char *value)
{
    if (strcmp(type, "mode") == 0) {
        int mode;

        if (strcmp(value, "EXTRACT_AND_EXPAND") == 0)
            mode = EVP_KDF_HKDF_MODE_EXTRACT_AND_EXPAND;
        else if (strcmp(value, "EXTRACT_ONLY") == 0)
            mode = EVP_KDF_HKDF_MODE_EXTRACT_ONLY;
        else if (strcmp(value, "EXPAND_ONLY") == 0)
            mode = EVP_KDF_HKDF_MODE_EXPAND_ONLY;
        else
            return 0;

        return call_ctrl(kdf_hkdf_ctrl, impl, EVP_KDF_CTRL_SET_HKDF_MODE, mode);
    }

    if (strcmp(type, "digest") == 0)
        return kdf_md2ctrl(impl, kdf_hkdf_ctrl, EVP_KDF_CTRL_SET_MD, value);

    if (strcmp(type, "salt") == 0)
        return kdf_str2ctrl(impl, kdf_hkdf_ctrl, EVP_KDF_CTRL_SET_SALT, value);

    if (strcmp(type, "hexsalt") == 0)
        return kdf_hex2ctrl(impl, kdf_hkdf_ctrl, EVP_KDF_CTRL_SET_SALT, value);

    if (strcmp(type, "key") == 0)
        return kdf_str2ctrl(impl, kdf_hkdf_ctrl, EVP_KDF_CTRL_SET_KEY, value);

    if (strcmp(type, "hexkey") == 0)
        return kdf_hex2ctrl(impl, kdf_hkdf_ctrl, EVP_KDF_CTRL_SET_KEY, value);

    if (strcmp(type, "info") == 0)
        return kdf_str2ctrl(impl, kdf_hkdf_ctrl, EVP_KDF_CTRL_ADD_HKDF_INFO,
                            value);

    if (strcmp(type, "hexinfo") == 0)
        return kdf_hex2ctrl(impl, kdf_hkdf_ctrl, EVP_KDF_CTRL_ADD_HKDF_INFO,
                            value);

    return -2;
}

static size_t kdf_hkdf_size(EVP_KDF_IMPL *impl)
{
    int sz;

    if (impl->mode != EVP_KDF_HKDF_MODE_EXTRACT_ONLY)
        return SIZE_MAX;

    if (impl->md == NULL) {
        KDFerr(KDF_F_KDF_HKDF_SIZE, KDF_R_MISSING_MESSAGE_DIGEST);
        return 0;
    }
    sz = EVP_MD_size(impl->md);
    if (sz < 0)
        return 0;

    return sz;
}

static int kdf_hkdf_derive(EVP_KDF_IMPL *impl, unsigned char *key,
                           size_t keylen)
{
    if (impl->md == NULL) {
        KDFerr(KDF_F_KDF_HKDF_DERIVE, KDF_R_MISSING_MESSAGE_DIGEST);
        return 0;
    }
    if (impl->key == NULL) {
        KDFerr(KDF_F_KDF_HKDF_DERIVE, KDF_R_MISSING_KEY);
        return 0;
    }

    switch (impl->mode) {
    case EVP_KDF_HKDF_MODE_EXTRACT_AND_EXPAND:
        return HKDF(impl->md, impl->salt, impl->salt_len, impl->key,
                    impl->key_len, impl->info, impl->info_len, key,
                    keylen);

    case EVP_KDF_HKDF_MODE_EXTRACT_ONLY:
        return HKDF_Extract(impl->md, impl->salt, impl->salt_len, impl->key,
                            impl->key_len, key, keylen);

    case EVP_KDF_HKDF_MODE_EXPAND_ONLY:
        return HKDF_Expand(impl->md, impl->key, impl->key_len, impl->info,
                           impl->info_len, key, keylen);

    default:
        return 0;
    }
}

const EVP_KDF hkdf_kdf_meth = {
    EVP_KDF_HKDF,
    kdf_hkdf_new,
    kdf_hkdf_free,
    kdf_hkdf_reset,
    kdf_hkdf_ctrl,
    kdf_hkdf_ctrl_str,
    kdf_hkdf_size,
    kdf_hkdf_derive
};

/*
 * Refer to "HMAC-based Extract-and-Expand Key Derivation Function (HKDF)"
 * Section 2 (https://tools.ietf.org/html/rfc5869#section-2) and
 * "Cryptographic Extraction and Key Derivation: The HKDF Scheme"
 * Section 4.2 (https://eprint.iacr.org/2010/264.pdf).
 *
 * From the paper:
 *   The scheme HKDF is specified as:
 *     HKDF(XTS, SKM, CTXinfo, L) = K(1) | K(2) | ... | K(t)
 *
 *     where:
 *       SKM is source key material
 *       XTS is extractor salt (which may be null or constant)
 *       CTXinfo is context information (may be null)
 *       L is the number of key bits to be produced by KDF
 *       k is the output length in bits of the hash function used with HMAC
 *       t = ceil(L/k)
 *       the value K(t) is truncated to its first d = L mod k bits.
 *
 * From RFC 5869:
 *   2.2.  Step 1: Extract
 *     HKDF-Extract(salt, IKM) -> PRK
 *   2.3.  Step 2: Expand
 *     HKDF-Expand(PRK, info, L) -> OKM
 */
static int HKDF(const EVP_MD *evp_md,
                const unsigned char *salt, size_t salt_len,
                const unsigned char *ikm, size_t ikm_len,
                const unsigned char *info, size_t info_len,
                unsigned char *okm, size_t okm_len)
{
    unsigned char prk[EVP_MAX_MD_SIZE];
    int ret, sz;
    size_t prk_len;

    sz = EVP_MD_size(evp_md);
    if (sz < 0)
        return 0;
    prk_len = (size_t)sz;

    /* Step 1: HKDF-Extract(salt, IKM) -> PRK */
    if (!HKDF_Extract(evp_md, salt, salt_len, ikm, ikm_len, prk, prk_len))
        return 0;

    /* Step 2: HKDF-Expand(PRK, info, L) -> OKM */
    ret = HKDF_Expand(evp_md, prk, prk_len, info, info_len, okm, okm_len);
    OPENSSL_cleanse(prk, sizeof(prk));

    return ret;
}

/*
 * Refer to "HMAC-based Extract-and-Expand Key Derivation Function (HKDF)"
 * Section 2.2 (https://tools.ietf.org/html/rfc5869#section-2.2).
 *
 * 2.2.  Step 1: Extract
 *
 *   HKDF-Extract(salt, IKM) -> PRK
 *
 *   Options:
 *      Hash     a hash function; HashLen denotes the length of the
 *               hash function output in octets
 *
 *   Inputs:
 *      salt     optional salt value (a non-secret random value);
 *               if not provided, it is set to a string of HashLen zeros.
 *      IKM      input keying material
 *
 *   Output:
 *      PRK      a pseudorandom key (of HashLen octets)
 *
 *   The output PRK is calculated as follows:
 *
 *   PRK = HMAC-Hash(salt, IKM)
 */
static int HKDF_Extract(const EVP_MD *evp_md,
                        const unsigned char *salt, size_t salt_len,
                        const unsigned char *ikm, size_t ikm_len,
                        unsigned char *prk, size_t prk_len)
{
    int sz = EVP_MD_size(evp_md);

    if (sz < 0)
        return 0;
    if (prk_len != (size_t)sz) {
        KDFerr(KDF_F_HKDF_EXTRACT, KDF_R_WRONG_OUTPUT_BUFFER_SIZE);
        return 0;
    }
    /* calc: PRK = HMAC-Hash(salt, IKM) */
    return HMAC(evp_md, salt, salt_len, ikm, ikm_len, prk, NULL) != NULL;
}

/*
 * Refer to "HMAC-based Extract-and-Expand Key Derivation Function (HKDF)"
 * Section 2.3 (https://tools.ietf.org/html/rfc5869#section-2.3).
 *
 * 2.3.  Step 2: Expand
 *
 *   HKDF-Expand(PRK, info, L) -> OKM
 *
 *   Options:
 *      Hash     a hash function; HashLen denotes the length of the
 *               hash function output in octets
 *
 *   Inputs:
 *      PRK      a pseudorandom key of at least HashLen octets
 *               (usually, the output from the extract step)
 *      info     optional context and application specific information
 *               (can be a zero-length string)
 *      L        length of output keying material in octets
 *               (<= 255*HashLen)
 *
 *   Output:
 *      OKM      output keying material (of L octets)
 *
 *   The output OKM is calculated as follows:
 *
 *   N = ceil(L/HashLen)
 *   T = T(1) | T(2) | T(3) | ... | T(N)
 *   OKM = first L octets of T
 *
 *   where:
 *   T(0) = empty string (zero length)
 *   T(1) = HMAC-Hash(PRK, T(0) | info | 0x01)
 *   T(2) = HMAC-Hash(PRK, T(1) | info | 0x02)
 *   T(3) = HMAC-Hash(PRK, T(2) | info | 0x03)
 *   ...
 *
 *   (where the constant concatenated to the end of each T(n) is a
 *   single octet.)
 */
static int 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;
    int ret = 0, sz;
    unsigned int i;
    unsigned char prev[EVP_MAX_MD_SIZE];
    size_t done_len = 0, dig_len, n;

    sz = EVP_MD_size(evp_md);
    if (sz <= 0)
        return 0;
    dig_len = (size_t)sz;

    /* calc: N = ceil(L/HashLen) */
    n = okm_len / dig_len;
    if (okm_len % dig_len)
        n++;

    if (n > 255 || okm == NULL)
        return 0;

    if ((hmac = HMAC_CTX_new()) == NULL)
        return 0;

    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;

        /* calc: T(i) = HMAC-Hash(PRK, T(i - 1) | info | 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;
    }
    ret = 1;

 err:
    OPENSSL_cleanse(prev, sizeof(prev));
    HMAC_CTX_free(hmac);
    return ret;
}
Commit	Line	Data
d2e9e320	1	/*
28428130	2	* Copyright 2016-2018 The OpenSSL Project Authors. All Rights Reserved.
aacfb134	3	*
7bb803e8	4	* Licensed under the Apache License 2.0 (the "License"). You may not use
d2e9e320 RS	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
aacfb134 AG	8	*/
	9
	10	#include <stdlib.h>
5a285add	11	#include <stdarg.h>
aacfb134 AG	12	#include <string.h>
aacfb134 AG	13	#include <openssl/hmac.h>
aacfb134	14	#include <openssl/evp.h>
5a285add	15	#include <openssl/kdf.h>
aacfb134	16	#include "internal/cryptlib.h"
cee719c2	17	#include "internal/numbers.h"
aacfb134	18	#include "internal/evp_int.h"
5a285add	19	#include "kdf_local.h"
aacfb134 AG	20
	21	#define HKDF_MAXBUF 1024
	22
5a285add DM	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,
e7018588	31	const unsigned char *ikm, size_t ikm_len,
5a285add DM	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 {
d2139cf8	39	int mode;
aacfb134 AG	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;
5a285add	47	};
aacfb134	48
5a285add	49	static EVP_KDF_IMPL *kdf_hkdf_new(void)
aacfb134	50	{
5a285add	51	EVP_KDF_IMPL *impl;
aacfb134	52
5a285add DM	53	if ((impl = OPENSSL_zalloc(sizeof(*impl))) == NULL)
	54	KDFerr(KDF_F_KDF_HKDF_NEW, ERR_R_MALLOC_FAILURE);
	55	return impl;
	56	}
aacfb134	57
5a285add DM	58	static void kdf_hkdf_free(EVP_KDF_IMPL *impl)
	59	{
	60	kdf_hkdf_reset(impl);
	61	OPENSSL_free(impl);
aacfb134 AG	62	}
aacfb134 AG	63
5a285add	64	static void kdf_hkdf_reset(EVP_KDF_IMPL *impl)
aacfb134	65	{
5a285add DM	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));
aacfb134 AG	70	}
aacfb134 AG	71
5a285add	72	static int kdf_hkdf_ctrl(EVP_KDF_IMPL *impl, int cmd, va_list args)
aacfb134	73	{
5a285add DM	74	const unsigned char *p;
	75	size_t len;
	76	const EVP_MD *md;
aacfb134	77
5a285add DM	78	switch (cmd) {
	79	case EVP_KDF_CTRL_SET_MD:
	80	md = va_arg(args, const EVP_MD *);
	81	if (md == NULL)
aacfb134 AG	82	return 0;
aacfb134 AG	83
5a285add	84	impl->md = md;
aacfb134 AG	85	return 1;
aacfb134 AG	86
5a285add DM	87	case EVP_KDF_CTRL_SET_HKDF_MODE:
5a285add DM	88	impl->mode = va_arg(args, int);
d2139cf8 MC	89	return 1;
d2139cf8 MC	90
5a285add DM	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)
aacfb134 AG	95	return 1;
aacfb134 AG	96
5a285add DM	97	OPENSSL_free(impl->salt);
	98	impl->salt = OPENSSL_memdup(p, len);
	99	if (impl->salt == NULL)
aacfb134 AG	100	return 0;
aacfb134 AG	101
5a285add	102	impl->salt_len = len;
aacfb134 AG	103	return 1;
aacfb134 AG	104
5a285add DM	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)
aacfb134 AG	111	return 0;
aacfb134 AG	112
5a285add DM	113	impl->key_len = len;
5a285add DM	114	return 1;
aacfb134	115
5a285add DM	116	case EVP_KDF_CTRL_RESET_HKDF_INFO:
	117	OPENSSL_cleanse(impl->info, impl->info_len);
	118	impl->info_len = 0;
aacfb134 AG	119	return 1;
aacfb134 AG	120
5a285add DM	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)
aacfb134 AG	125	return 1;
aacfb134 AG	126
5a285add	127	if (len > (HKDF_MAXBUF - impl->info_len))
aacfb134 AG	128	return 0;
aacfb134 AG	129
5a285add DM	130	memcpy(impl->info + impl->info_len, p, len);
5a285add DM	131	impl->info_len += len;
aacfb134 AG	132	return 1;
	133
	134	default:
	135	return -2;
aacfb134 AG	136	}
	137	}
	138
5a285add DM	139	static int kdf_hkdf_ctrl_str(EVP_KDF_IMPL impl, const char type,
5a285add DM	140	const char *value)
aacfb134	141	{
ddd2c389 MC	142	if (strcmp(type, "mode") == 0) {
	143	int mode;
	144
	145	if (strcmp(value, "EXTRACT_AND_EXPAND") == 0)
5a285add	146	mode = EVP_KDF_HKDF_MODE_EXTRACT_AND_EXPAND;
ddd2c389	147	else if (strcmp(value, "EXTRACT_ONLY") == 0)
5a285add	148	mode = EVP_KDF_HKDF_MODE_EXTRACT_ONLY;
ddd2c389	149	else if (strcmp(value, "EXPAND_ONLY") == 0)
5a285add	150	mode = EVP_KDF_HKDF_MODE_EXPAND_ONLY;
ddd2c389 MC	151	else
	152	return 0;
	153
5a285add	154	return call_ctrl(kdf_hkdf_ctrl, impl, EVP_KDF_CTRL_SET_HKDF_MODE, mode);
ddd2c389 MC	155	}
ddd2c389 MC	156
5a285add DM	157	if (strcmp(type, "digest") == 0)
5a285add DM	158	return kdf_md2ctrl(impl, kdf_hkdf_ctrl, EVP_KDF_CTRL_SET_MD, value);
aacfb134 AG	159
aacfb134 AG	160	if (strcmp(type, "salt") == 0)
5a285add	161	return kdf_str2ctrl(impl, kdf_hkdf_ctrl, EVP_KDF_CTRL_SET_SALT, value);
aacfb134 AG	162
aacfb134 AG	163	if (strcmp(type, "hexsalt") == 0)
5a285add	164	return kdf_hex2ctrl(impl, kdf_hkdf_ctrl, EVP_KDF_CTRL_SET_SALT, value);
aacfb134 AG	165
aacfb134 AG	166	if (strcmp(type, "key") == 0)
5a285add	167	return kdf_str2ctrl(impl, kdf_hkdf_ctrl, EVP_KDF_CTRL_SET_KEY, value);
aacfb134 AG	168
aacfb134 AG	169	if (strcmp(type, "hexkey") == 0)
5a285add	170	return kdf_hex2ctrl(impl, kdf_hkdf_ctrl, EVP_KDF_CTRL_SET_KEY, value);
aacfb134 AG	171
aacfb134 AG	172	if (strcmp(type, "info") == 0)
5a285add DM	173	return kdf_str2ctrl(impl, kdf_hkdf_ctrl, EVP_KDF_CTRL_ADD_HKDF_INFO,
5a285add DM	174	value);
aacfb134 AG	175
aacfb134 AG	176	if (strcmp(type, "hexinfo") == 0)
5a285add DM	177	return kdf_hex2ctrl(impl, kdf_hkdf_ctrl, EVP_KDF_CTRL_ADD_HKDF_INFO,
5a285add DM	178	value);
aacfb134 AG	179
	180	return -2;
	181	}
	182
5a285add	183	static size_t kdf_hkdf_size(EVP_KDF_IMPL *impl)
ca55d70b	184	{
97cc9c9b SL	185	int sz;
97cc9c9b SL	186
5a285add DM	187	if (impl->mode != EVP_KDF_HKDF_MODE_EXTRACT_ONLY)
5a285add DM	188	return SIZE_MAX;
ca55d70b	189
5a285add DM	190	if (impl->md == NULL) {
	191	KDFerr(KDF_F_KDF_HKDF_SIZE, KDF_R_MISSING_MESSAGE_DIGEST);
	192	return 0;
	193	}
97cc9c9b SL	194	sz = EVP_MD_size(impl->md);
	195	if (sz < 0)
	196	return 0;
	197
	198	return sz;
ca55d70b MC	199	}
ca55d70b MC	200
5a285add DM	201	static int kdf_hkdf_derive(EVP_KDF_IMPL impl, unsigned char key,
5a285add DM	202	size_t keylen)
aacfb134	203	{
5a285add DM	204	if (impl->md == NULL) {
5a285add DM	205	KDFerr(KDF_F_KDF_HKDF_DERIVE, KDF_R_MISSING_MESSAGE_DIGEST);
f55129c7 JB	206	return 0;
f55129c7 JB	207	}
5a285add DM	208	if (impl->key == NULL) {
5a285add DM	209	KDFerr(KDF_F_KDF_HKDF_DERIVE, KDF_R_MISSING_KEY);
aacfb134	210	return 0;
e65f6509	211	}
aacfb134	212
5a285add DM	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);
d2139cf8	218
5a285add DM	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);
d2139cf8	222
5a285add DM	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);
d2139cf8 MC	226
d2139cf8 MC	227	default:
aacfb134 AG	228	return 0;
aacfb134 AG	229	}
aacfb134 AG	230	}
aacfb134 AG	231
d2ba8123	232	const EVP_KDF hkdf_kdf_meth = {
5a285add DM	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
aacfb134 AG	241	};
aacfb134 AG	242
e7018588 DM	243	/*
	244	* Refer to "HMAC-based Extract-and-Expand Key Derivation Function (HKDF)"
	245	* Section 2 (https://tools.ietf.org/html/rfc5869#section-2) and
	246	* "Cryptographic Extraction and Key Derivation: The HKDF Scheme"
	247	* Section 4.2 (https://eprint.iacr.org/2010/264.pdf).
	248	*
	249	* From the paper:
	250	* The scheme HKDF is specified as:
	251	* HKDF(XTS, SKM, CTXinfo, L) = K(1) \| K(2) \| ... \| K(t)
	252	*
	253	* where:
	254	* SKM is source key material
	255	* XTS is extractor salt (which may be null or constant)
	256	* CTXinfo is context information (may be null)
	257	* L is the number of key bits to be produced by KDF
	258	* k is the output length in bits of the hash function used with HMAC
	259	* t = ceil(L/k)
	260	* the value K(t) is truncated to its first d = L mod k bits.
	261	*
	262	* From RFC 5869:
	263	* 2.2. Step 1: Extract
	264	* HKDF-Extract(salt, IKM) -> PRK
	265	* 2.3. Step 2: Expand
	266	* HKDF-Expand(PRK, info, L) -> OKM
	267	*/
5a285add DM	268	static int HKDF(const EVP_MD *evp_md,
5a285add DM	269	const unsigned char *salt, size_t salt_len,
e7018588	270	const unsigned char *ikm, size_t ikm_len,
5a285add DM	271	const unsigned char *info, size_t info_len,
5a285add DM	272	unsigned char *okm, size_t okm_len)
aacfb134 AG	273	{
aacfb134 AG	274	unsigned char prk[EVP_MAX_MD_SIZE];
97cc9c9b SL	275	int ret, sz;
	276	size_t prk_len;
	277
	278	sz = EVP_MD_size(evp_md);
	279	if (sz < 0)
	280	return 0;
	281	prk_len = (size_t)sz;
aacfb134	282
e7018588 DM	283	/* Step 1: HKDF-Extract(salt, IKM) -> PRK */
e7018588 DM	284	if (!HKDF_Extract(evp_md, salt, salt_len, ikm, ikm_len, prk, prk_len))
5a285add	285	return 0;
aacfb134	286
e7018588	287	/* Step 2: HKDF-Expand(PRK, info, L) -> OKM */
d2139cf8 MC	288	ret = HKDF_Expand(evp_md, prk, prk_len, info, info_len, okm, okm_len);
	289	OPENSSL_cleanse(prk, sizeof(prk));
	290
	291	return ret;
aacfb134 AG	292	}
aacfb134 AG	293
e7018588 DM	294	/*
	295	* Refer to "HMAC-based Extract-and-Expand Key Derivation Function (HKDF)"
	296	* Section 2.2 (https://tools.ietf.org/html/rfc5869#section-2.2).
	297	*
	298	* 2.2. Step 1: Extract
	299	*
	300	* HKDF-Extract(salt, IKM) -> PRK
	301	*
	302	* Options:
	303	* Hash a hash function; HashLen denotes the length of the
	304	* hash function output in octets
	305	*
	306	* Inputs:
	307	* salt optional salt value (a non-secret random value);
	308	* if not provided, it is set to a string of HashLen zeros.
	309	* IKM input keying material
	310	*
	311	* Output:
	312	* PRK a pseudorandom key (of HashLen octets)
	313	*
	314	* The output PRK is calculated as follows:
	315	*
	316	* PRK = HMAC-Hash(salt, IKM)
	317	*/
5a285add DM	318	static int HKDF_Extract(const EVP_MD *evp_md,
5a285add DM	319	const unsigned char *salt, size_t salt_len,
e7018588	320	const unsigned char *ikm, size_t ikm_len,
5a285add	321	unsigned char *prk, size_t prk_len)
aacfb134	322	{
97cc9c9b SL	323	int sz = EVP_MD_size(evp_md);
	324
	325	if (sz < 0)
	326	return 0;
	327	if (prk_len != (size_t)sz) {
5a285add DM	328	KDFerr(KDF_F_HKDF_EXTRACT, KDF_R_WRONG_OUTPUT_BUFFER_SIZE);
	329	return 0;
	330	}
e7018588 DM	331	/* calc: PRK = HMAC-Hash(salt, IKM) */
e7018588 DM	332	return HMAC(evp_md, salt, salt_len, ikm, ikm_len, prk, NULL) != NULL;
aacfb134 AG	333	}
aacfb134 AG	334
e7018588 DM	335	/*
	336	* Refer to "HMAC-based Extract-and-Expand Key Derivation Function (HKDF)"
	337	* Section 2.3 (https://tools.ietf.org/html/rfc5869#section-2.3).
	338	*
	339	* 2.3. Step 2: Expand
	340	*
	341	* HKDF-Expand(PRK, info, L) -> OKM
	342	*
	343	* Options:
	344	* Hash a hash function; HashLen denotes the length of the
	345	* hash function output in octets
	346	*
	347	* Inputs:
	348	* PRK a pseudorandom key of at least HashLen octets
	349	* (usually, the output from the extract step)
	350	* info optional context and application specific information
	351	* (can be a zero-length string)
	352	* L length of output keying material in octets
	353	* (<= 255*HashLen)
	354	*
	355	* Output:
	356	* OKM output keying material (of L octets)
	357	*
	358	* The output OKM is calculated as follows:
	359	*
	360	* N = ceil(L/HashLen)
	361	* T = T(1) \| T(2) \| T(3) \| ... \| T(N)
	362	* OKM = first L octets of T
	363	*
	364	* where:
	365	* T(0) = empty string (zero length)
	366	* T(1) = HMAC-Hash(PRK, T(0) \| info \| 0x01)
	367	* T(2) = HMAC-Hash(PRK, T(1) \| info \| 0x02)
	368	* T(3) = HMAC-Hash(PRK, T(2) \| info \| 0x03)
	369	* ...
	370	*
	371	* (where the constant concatenated to the end of each T(n) is a
	372	* single octet.)
	373	*/
5a285add DM	374	static int HKDF_Expand(const EVP_MD *evp_md,
	375	const unsigned char *prk, size_t prk_len,
	376	const unsigned char *info, size_t info_len,
	377	unsigned char *okm, size_t okm_len)
aacfb134 AG	378	{
aacfb134 AG	379	HMAC_CTX *hmac;
97cc9c9b	380	int ret = 0, sz;
aacfb134	381	unsigned int i;
aacfb134	382	unsigned char prev[EVP_MAX_MD_SIZE];
97cc9c9b SL	383	size_t done_len = 0, dig_len, n;
	384
	385	sz = EVP_MD_size(evp_md);
	386	if (sz <= 0)
	387	return 0;
	388	dig_len = (size_t)sz;
5a285add	389
e7018588 DM	390	/* calc: N = ceil(L/HashLen) */
e7018588 DM	391	n = okm_len / dig_len;
aacfb134 AG	392	if (okm_len % dig_len)
	393	n++;
	394
d2139cf8	395	if (n > 255 \|\| okm == NULL)
5a285add	396	return 0;
aacfb134 AG	397
aacfb134 AG	398	if ((hmac = HMAC_CTX_new()) == NULL)
5a285add	399	return 0;
aacfb134 AG	400
	401	if (!HMAC_Init_ex(hmac, prk, prk_len, evp_md, NULL))
	402	goto err;
	403
	404	for (i = 1; i <= n; i++) {
	405	size_t copy_len;
	406	const unsigned char ctr = i;
	407
e7018588	408	/* calc: T(i) = HMAC-Hash(PRK, T(i - 1) \| info \| i) */
aacfb134 AG	409	if (i > 1) {
	410	if (!HMAC_Init_ex(hmac, NULL, 0, NULL, NULL))
	411	goto err;
	412
	413	if (!HMAC_Update(hmac, prev, dig_len))
	414	goto err;
	415	}
	416
	417	if (!HMAC_Update(hmac, info, info_len))
	418	goto err;
	419
	420	if (!HMAC_Update(hmac, &ctr, 1))
	421	goto err;
	422
	423	if (!HMAC_Final(hmac, prev, NULL))
	424	goto err;
	425
	426	copy_len = (done_len + dig_len > okm_len) ?
	427	okm_len - done_len :
	428	dig_len;
	429
	430	memcpy(okm + done_len, prev, copy_len);
	431
	432	done_len += copy_len;
	433	}
5a285add	434	ret = 1;
aacfb134 AG	435
aacfb134 AG	436	err:
64ed55ab	437	OPENSSL_cleanse(prev, sizeof(prev));
aacfb134	438	HMAC_CTX_free(hmac);
64ed55ab	439	return ret;
aacfb134	440	}