2 * Copyright 2013-2016 The OpenSSL Project Authors. All Rights Reserved.
4 * Licensed under the OpenSSL license (the "License"). You may not use
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
12 #ifndef OPENSSL_NO_CMS
14 #include <openssl/dh.h>
15 #include <openssl/evp.h>
16 #include <openssl/asn1.h>
17 #include <openssl/cms.h>
20 /* Key derivation from X9.42/RFC2631 */
21 /* Uses CMS functions, hence the #ifdef wrapper. */
23 #define DH_KDF_MAX (1L << 30)
25 /* Skip past an ASN1 structure: for OBJECT skip content octets too */
27 static int skip_asn1(unsigned char **pp, long *plen, int exptag)
29 const unsigned char *q = *pp;
32 i = ASN1_get_object(&q, &tmplen, &tag, &xclass, *plen);
35 if (tag != exptag || xclass != V_ASN1_UNIVERSAL)
37 if (tag == V_ASN1_OBJECT)
40 *pp = (unsigned char *)q;
45 * Encode the DH shared info structure, return an offset to the counter value
46 * so we can update the structure without reencoding it.
49 static int dh_sharedinfo_encode(unsigned char **pder, unsigned char **pctr,
50 ASN1_OBJECT *key_oid, size_t outlen,
51 const unsigned char *ukm, size_t ukmlen)
56 /* "magic" value to check offset is sane */
57 static unsigned char ctr[4] = { 0xF3, 0x17, 0x22, 0x53 };
59 ASN1_OCTET_STRING ctr_oct, ukm_oct, *pukm_oct;
61 if (ukmlen > DH_KDF_MAX || outlen > DH_KDF_MAX)
66 ctr_oct.type = V_ASN1_OCTET_STRING;
67 ctr_atype.type = V_ASN1_OCTET_STRING;
68 ctr_atype.value.octet_string = &ctr_oct;
69 atmp.algorithm = key_oid;
70 atmp.parameter = &ctr_atype;
72 ukm_oct.type = V_ASN1_OCTET_STRING;
74 ukm_oct.data = (unsigned char *)ukm;
75 ukm_oct.length = ukmlen;
79 derlen = CMS_SharedInfo_encode(pder, &atmp, pukm_oct, outlen);
84 if (!skip_asn1(&p, &tlen, V_ASN1_SEQUENCE))
86 if (!skip_asn1(&p, &tlen, V_ASN1_SEQUENCE))
88 if (!skip_asn1(&p, &tlen, V_ASN1_OBJECT))
90 if (!skip_asn1(&p, &tlen, V_ASN1_OCTET_STRING))
92 if (CRYPTO_memcmp(p, ctr, 4))
98 int DH_KDF_X9_42(unsigned char *out, size_t outlen,
99 const unsigned char *Z, size_t Zlen,
100 ASN1_OBJECT *key_oid,
101 const unsigned char *ukm, size_t ukmlen, const EVP_MD *md)
103 EVP_MD_CTX *mctx = NULL;
107 unsigned char *der = NULL, *ctr;
109 if (Zlen > DH_KDF_MAX)
111 mctx = EVP_MD_CTX_new();
114 mdlen = EVP_MD_size(md);
115 derlen = dh_sharedinfo_encode(&der, &ctr, key_oid, outlen, ukm, ukmlen);
119 unsigned char mtmp[EVP_MAX_MD_SIZE];
120 if (!EVP_DigestInit_ex(mctx, md, NULL)
121 || !EVP_DigestUpdate(mctx, Z, Zlen))
124 ctr[2] = (i >> 8) & 0xFF;
125 ctr[1] = (i >> 16) & 0xFF;
126 ctr[0] = (i >> 24) & 0xFF;
127 if (!EVP_DigestUpdate(mctx, der, derlen))
129 if (outlen >= mdlen) {
130 if (!EVP_DigestFinal(mctx, out, NULL))
137 if (!EVP_DigestFinal(mctx, mtmp, NULL))
139 memcpy(out, mtmp, outlen);
140 OPENSSL_cleanse(mtmp, mdlen);
147 EVP_MD_CTX_free(mctx);