/*

 * Copyright 2013-2016 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 "e_os.h"

#ifndef OPENSSL_NO_CMS

#include <string.h>

#include <openssl/dh.h>

#include <openssl/evp.h>

#include <openssl/asn1.h>

#include <openssl/cms.h>

/* Key derivation from X9.42/RFC2631 */

/* Uses CMS functions, hence the #ifdef wrapper. */

#define DH_KDF_MAX      (1L << 30)

/* Skip past an ASN1 structure: for OBJECT skip content octets too */

static int skip_asn1(unsigned char **pp, long *plen, int exptag)

{

    const unsigned char *q = *pp;

    int i, tag, xclass;

    long tmplen;

    i = ASN1_get_object(&q, &tmplen, &tag, &xclass, *plen);

    if (i & 0x80)

        return 0;

    if (tag != exptag || xclass != V_ASN1_UNIVERSAL)

        return 0;

    if (tag == V_ASN1_OBJECT)

        q += tmplen;

    *plen -= q - *pp;

    *pp = (unsigned char *)q;

    return 1;

}

/*

 * Encode the DH shared info structure, return an offset to the counter value

 * so we can update the structure without reencoding it.

 */

static int dh_sharedinfo_encode(unsigned char **pder, unsigned char **pctr,

                                ASN1_OBJECT *key_oid, size_t outlen,

                                const unsigned char *ukm, size_t ukmlen)

{

    unsigned char *p;

    int derlen;

    long tlen;

    /* "magic" value to check offset is sane */

    static unsigned char ctr[4] = { 0xF3, 0x17, 0x22, 0x53 };

    X509_ALGOR atmp;

    ASN1_OCTET_STRING ctr_oct, ukm_oct, *pukm_oct;

    ASN1_TYPE ctr_atype;

    if (ukmlen > DH_KDF_MAX || outlen > DH_KDF_MAX)

        return 0;

    ctr_oct.data = ctr;

    ctr_oct.length = 4;

    ctr_oct.flags = 0;

    ctr_oct.type = V_ASN1_OCTET_STRING;

    ctr_atype.type = V_ASN1_OCTET_STRING;

    ctr_atype.value.octet_string = &ctr_oct;

    atmp.algorithm = key_oid;

    atmp.parameter = &ctr_atype;

    if (ukm) {

        ukm_oct.type = V_ASN1_OCTET_STRING;

        ukm_oct.flags = 0;

        ukm_oct.data = (unsigned char *)ukm;

        ukm_oct.length = ukmlen;

        pukm_oct = &ukm_oct;

    } else

        pukm_oct = NULL;

    derlen = CMS_SharedInfo_encode(pder, &atmp, pukm_oct, outlen);

    if (derlen <= 0)

        return 0;

    p = *pder;

    tlen = derlen;

    if (!skip_asn1(&p, &tlen, V_ASN1_SEQUENCE))

        return 0;

    if (!skip_asn1(&p, &tlen, V_ASN1_SEQUENCE))

        return 0;

    if (!skip_asn1(&p, &tlen, V_ASN1_OBJECT))

        return 0;

    if (!skip_asn1(&p, &tlen, V_ASN1_OCTET_STRING))

        return 0;

    if (CRYPTO_memcmp(p, ctr, 4))

        return 0;

    *pctr = p;

    return derlen;

}

int DH_KDF_X9_42(unsigned char *out, size_t outlen,

                 const unsigned char *Z, size_t Zlen,

                 ASN1_OBJECT *key_oid,

                 const unsigned char *ukm, size_t ukmlen, const EVP_MD *md)

{

    EVP_MD_CTX *mctx = NULL;

    int rv = 0;

    unsigned int i;

    size_t mdlen;

    unsigned char *der = NULL, *ctr;

    int derlen;

    if (Zlen > DH_KDF_MAX)

        return 0;

    mctx = EVP_MD_CTX_new();

    if (mctx == NULL)

        return 0;

    mdlen = EVP_MD_size(md);

    derlen = dh_sharedinfo_encode(&der, &ctr, key_oid, outlen, ukm, ukmlen);

    if (derlen == 0)

        goto err;

    for (i = 1;; i++) {

        unsigned char mtmp[EVP_MAX_MD_SIZE];

        if (!EVP_DigestInit_ex(mctx, md, NULL)

            || !EVP_DigestUpdate(mctx, Z, Zlen))

            goto err;

        ctr[3] = i & 0xFF;

        ctr[2] = (i >> 8) & 0xFF;

        ctr[1] = (i >> 16) & 0xFF;

        ctr[0] = (i >> 24) & 0xFF;

        if (!EVP_DigestUpdate(mctx, der, derlen))

            goto err;

        if (outlen >= mdlen) {

            if (!EVP_DigestFinal(mctx, out, NULL))

                goto err;

            outlen -= mdlen;

            if (outlen == 0)

                break;

            out += mdlen;

        } else {

            if (!EVP_DigestFinal(mctx, mtmp, NULL))

                goto err;

            memcpy(out, mtmp, outlen);

            OPENSSL_cleanse(mtmp, mdlen);

            break;

        }

    }

    rv = 1;

 err:

    OPENSSL_free(der);

    EVP_MD_CTX_free(mctx);

    return rv;

}

#endif