Commit aacfb134 authored by Alessandro Ghedini's avatar Alessandro Ghedini Committed by Rich Salz
Browse files

GH355: Implement HKDF 



This patch implements the HMAC-based Extract-and-Expand Key Derivation
Function (HKDF) as defined in RFC 5869.

It is required to implement the QUIC and TLS 1.3 protocols (among others).

Signed-off-by: default avatarRich Salz <rsalz@openssl.org>
Reviewed-by: default avatarDr. Stephen Henson <steve@openssl.org>
parent b894054e

crypto/evp/pmeth_lib.c

+2 −1
Original line number Diff line number Diff line
@@ -90,7 +90,8 @@ static const EVP_PKEY_METHOD *standard_methods[] = { 
#ifndef OPENSSL_NO_DH

    &dhx_pkey_meth,

#endif

    &tls1_prf_pkey_meth

    &tls1_prf_pkey_meth,

    &hkdf_pkey_meth

};



DECLARE_OBJ_BSEARCH_CMP_FN(const EVP_PKEY_METHOD *, const EVP_PKEY_METHOD *,

crypto/include/internal/evp_int.h

+1 −0
Original line number Diff line number Diff line
@@ -131,6 +131,7 @@ extern const EVP_PKEY_METHOD ec_pkey_meth; 
extern const EVP_PKEY_METHOD hmac_pkey_meth;

extern const EVP_PKEY_METHOD rsa_pkey_meth;

extern const EVP_PKEY_METHOD tls1_prf_pkey_meth;

extern const EVP_PKEY_METHOD hkdf_pkey_meth;



struct evp_md_st {

    int type;

crypto/kdf/Makefile.in

+2 −2
Original line number Diff line number Diff line
@@ -15,8 +15,8 @@ CFLAGS= $(INCLUDES) $(CFLAG) $(SHARED_CFLAG) 
GENERAL=Makefile



LIB=$(TOP)/libcrypto.a

LIBSRC=tls1_prf.c kdf_err.c

LIBOBJ=tls1_prf.o kdf_err.o

LIBSRC=tls1_prf.c kdf_err.c hkdf.c

LIBOBJ=tls1_prf.o kdf_err.o hkdf.o



SRC= $(LIBSRC)

crypto/kdf/build.info

+1 −1
Original line number Diff line number Diff line 
LIBS=../../libcrypto

SOURCE[../../libcrypto]=\

        tls1_prf.c kdf_err.c
 
        tls1_prf.c kdf_err.c hkdf.c

crypto/kdf/hkdf.c

0 → 100644
+332 −0
Original line number Diff line number Diff line 
/* ====================================================================

 * Copyright (c) 2016 The OpenSSL Project.  All rights reserved.

 *

 * Redistribution and use in source and binary forms, with or without

 * modification, are permitted provided that the following conditions

 * are met:

 *

 * 1. Redistributions of source code must retain the above copyright

 *    notice, this list of conditions and the following disclaimer.

 *

 * 2. Redistributions in binary form must reproduce the above copyright

 *    notice, this list of conditions and the following disclaimer in

 *    the documentation and/or other materials provided with the

 *    distribution.

 *

 * 3. All advertising materials mentioning features or use of this

 *    software must display the following acknowledgment:

 *    "This product includes software developed by the OpenSSL Project

 *    for use in the OpenSSL Toolkit. (http://www.openssl.org/)"

 *

 * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to

 *    endorse or promote products derived from this software without

 *    prior written permission. For written permission, please contact

 *    openssl-core@openssl.org.

 *

 * 5. Products derived from this software may not be called "OpenSSL"

 *    nor may "OpenSSL" appear in their names without prior written

 *    permission of the OpenSSL Project.

 *

 * 6. Redistributions of any form whatsoever must retain the following

 *    acknowledgment:

 *    "This product includes software developed by the OpenSSL Project

 *    for use in the OpenSSL Toolkit (http://www.openssl.org/)"

 *

 * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY

 * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE

 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR

 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE OpenSSL PROJECT OR

 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,

 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT

 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;

 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)

 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,

 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)

 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED

 * OF THE POSSIBILITY OF SUCH DAMAGE.

 */



#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;

}