1/* crypto/dh/dh_kdf.c */
2/*
3 * Written by Stephen Henson for the OpenSSL project.
4 */
5/* ====================================================================
6 * Copyright (c) 2013 The OpenSSL Project.  All rights reserved.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 *
12 * 1. Redistributions of source code must retain the above copyright
13 *    notice, this list of conditions and the following disclaimer.
14 *
15 * 2. Redistributions in binary form must reproduce the above copyright
16 *    notice, this list of conditions and the following disclaimer in
17 *    the documentation and/or other materials provided with the
18 *    distribution.
19 *
20 * 3. All advertising materials mentioning features or use of this
21 *    software must display the following acknowledgment:
22 *    "This product includes software developed by the OpenSSL Project
23 *    for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
24 *
25 * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
26 *    endorse or promote products derived from this software without
27 *    prior written permission. For written permission, please contact
28 *    openssl-core@openssl.org.
29 *
30 * 5. Products derived from this software may not be called "OpenSSL"
31 *    nor may "OpenSSL" appear in their names without prior written
32 *    permission of the OpenSSL Project.
33 *
34 * 6. Redistributions of any form whatsoever must retain the following
35 *    acknowledgment:
36 *    "This product includes software developed by the OpenSSL Project
37 *    for use in the OpenSSL Toolkit (http://www.openssl.org/)"
38 *
39 * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
40 * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
41 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
42 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE OpenSSL PROJECT OR
43 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
44 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
45 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
46 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
47 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
48 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
49 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
50 * OF THE POSSIBILITY OF SUCH DAMAGE.
51 * ====================================================================
52 */
53
54#include <string.h>
55#include <openssl/dh.h>
56#include <openssl/evp.h>
57#include <openssl/asn1.h>
58#include <openssl/cms.h>
59
60/* Key derivation from X9.42/RFC2631 */
61
62#define DH_KDF_MAX      (1L << 30)
63
64/* Skip past an ASN1 structure: for OBJECT skip content octets too */
65
66static int skip_asn1(unsigned char **pp, long *plen, int exptag)
67{
68    const unsigned char *q = *pp;
69    int i, tag, xclass;
70    long tmplen;
71    i = ASN1_get_object(&q, &tmplen, &tag, &xclass, *plen);
72    if (i & 0x80)
73        return 0;
74    if (tag != exptag || xclass != V_ASN1_UNIVERSAL)
75        return 0;
76    if (tag == V_ASN1_OBJECT)
77        q += tmplen;
78    *plen -= q - *pp;
79    *pp = (unsigned char *)q;
80    return 1;
81}
82
83/*
84 * Encode the DH shared info structure, return an offset to the counter value
85 * so we can update the structure without reencoding it.
86 */
87
88static int dh_sharedinfo_encode(unsigned char **pder, unsigned char **pctr,
89                                ASN1_OBJECT *key_oid, size_t outlen,
90                                const unsigned char *ukm, size_t ukmlen)
91{
92    unsigned char *p;
93    int derlen;
94    long tlen;
95    /* "magic" value to check offset is sane */
96    static unsigned char ctr[4] = { 0xF3, 0x17, 0x22, 0x53 };
97    X509_ALGOR atmp;
98    ASN1_OCTET_STRING ctr_oct, ukm_oct, *pukm_oct;
99    ASN1_TYPE ctr_atype;
100    if (ukmlen > DH_KDF_MAX || outlen > DH_KDF_MAX)
101        return 0;
102    ctr_oct.data = ctr;
103    ctr_oct.length = 4;
104    ctr_oct.flags = 0;
105    ctr_oct.type = V_ASN1_OCTET_STRING;
106    ctr_atype.type = V_ASN1_OCTET_STRING;
107    ctr_atype.value.octet_string = &ctr_oct;
108    atmp.algorithm = key_oid;
109    atmp.parameter = &ctr_atype;
110    if (ukm) {
111        ukm_oct.type = V_ASN1_OCTET_STRING;
112        ukm_oct.flags = 0;
113        ukm_oct.data = (unsigned char *)ukm;
114        ukm_oct.length = ukmlen;
115        pukm_oct = &ukm_oct;
116    } else
117        pukm_oct = NULL;
118    derlen = CMS_SharedInfo_encode(pder, &atmp, pukm_oct, outlen);
119    if (derlen <= 0)
120        return 0;
121    p = *pder;
122    tlen = derlen;
123    if (!skip_asn1(&p, &tlen, V_ASN1_SEQUENCE))
124        return 0;
125    if (!skip_asn1(&p, &tlen, V_ASN1_SEQUENCE))
126        return 0;
127    if (!skip_asn1(&p, &tlen, V_ASN1_OBJECT))
128        return 0;
129    if (!skip_asn1(&p, &tlen, V_ASN1_OCTET_STRING))
130        return 0;
131    if (CRYPTO_memcmp(p, ctr, 4))
132        return 0;
133    *pctr = p;
134    return derlen;
135}
136
137int DH_KDF_X9_42(unsigned char *out, size_t outlen,
138                 const unsigned char *Z, size_t Zlen,
139                 ASN1_OBJECT *key_oid,
140                 const unsigned char *ukm, size_t ukmlen, const EVP_MD *md)
141{
142    EVP_MD_CTX mctx;
143    int rv = 0;
144    unsigned int i;
145    size_t mdlen;
146    unsigned char *der = NULL, *ctr;
147    int derlen;
148    if (Zlen > DH_KDF_MAX)
149        return 0;
150    mdlen = EVP_MD_size(md);
151    EVP_MD_CTX_init(&mctx);
152    derlen = dh_sharedinfo_encode(&der, &ctr, key_oid, outlen, ukm, ukmlen);
153    if (derlen == 0)
154        goto err;
155    for (i = 1;; i++) {
156        unsigned char mtmp[EVP_MAX_MD_SIZE];
157        EVP_DigestInit_ex(&mctx, md, NULL);
158        if (!EVP_DigestUpdate(&mctx, Z, Zlen))
159            goto err;
160        ctr[3] = i & 0xFF;
161        ctr[2] = (i >> 8) & 0xFF;
162        ctr[1] = (i >> 16) & 0xFF;
163        ctr[0] = (i >> 24) & 0xFF;
164        if (!EVP_DigestUpdate(&mctx, der, derlen))
165            goto err;
166        if (outlen >= mdlen) {
167            if (!EVP_DigestFinal(&mctx, out, NULL))
168                goto err;
169            outlen -= mdlen;
170            if (outlen == 0)
171                break;
172            out += mdlen;
173        } else {
174            if (!EVP_DigestFinal(&mctx, mtmp, NULL))
175                goto err;
176            memcpy(out, mtmp, outlen);
177            OPENSSL_cleanse(mtmp, mdlen);
178            break;
179        }
180    }
181    rv = 1;
182 err:
183    if (der)
184        OPENSSL_free(der);
185    EVP_MD_CTX_cleanup(&mctx);
186    return rv;
187}
188