Annotation of src/usr.bin/ssh/ssh-dss.c, Revision 1.18.4.1
1.1 markus 1: /*
2: * Copyright (c) 2000 Markus Friedl. All rights reserved.
3: *
4: * Redistribution and use in source and binary forms, with or without
5: * modification, are permitted provided that the following conditions
6: * are met:
7: * 1. Redistributions of source code must retain the above copyright
8: * notice, this list of conditions and the following disclaimer.
9: * 2. Redistributions in binary form must reproduce the above copyright
10: * notice, this list of conditions and the following disclaimer in the
11: * documentation and/or other materials provided with the distribution.
12: *
13: * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
14: * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
15: * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
16: * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
17: * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
18: * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
19: * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
20: * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
21: * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
22: * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
23: */
24:
25: #include "includes.h"
1.18.4.1! brad 26: RCSID("$OpenBSD: ssh-dss.c,v 1.19 2003/11/10 16:23:41 jakob Exp $");
1.4 markus 27:
28: #include <openssl/bn.h>
29: #include <openssl/evp.h>
1.1 markus 30:
31: #include "xmalloc.h"
32: #include "buffer.h"
33: #include "bufaux.h"
34: #include "compat.h"
1.4 markus 35: #include "log.h"
1.1 markus 36: #include "key.h"
37:
38: #define INTBLOB_LEN 20
39: #define SIGBLOB_LEN (2*INTBLOB_LEN)
40:
41: int
1.18.4.1! brad 42: ssh_dss_sign(const Key *key, u_char **sigp, u_int *lenp,
! 43: const u_char *data, u_int datalen)
1.1 markus 44: {
45: DSA_SIG *sig;
1.14 markus 46: const EVP_MD *evp_md = EVP_sha1();
1.1 markus 47: EVP_MD_CTX md;
1.17 markus 48: u_char digest[EVP_MAX_MD_SIZE], sigblob[SIGBLOB_LEN];
1.7 markus 49: u_int rlen, slen, len, dlen;
1.1 markus 50: Buffer b;
51:
52: if (key == NULL || key->type != KEY_DSA || key->dsa == NULL) {
53: error("ssh_dss_sign: no DSA key");
54: return -1;
55: }
56: EVP_DigestInit(&md, evp_md);
57: EVP_DigestUpdate(&md, data, datalen);
1.12 markus 58: EVP_DigestFinal(&md, digest, &dlen);
1.1 markus 59:
1.3 markus 60: sig = DSA_do_sign(digest, dlen, key->dsa);
1.12 markus 61: memset(digest, 'd', sizeof(digest));
1.7 markus 62:
1.1 markus 63: if (sig == NULL) {
1.7 markus 64: error("ssh_dss_sign: sign failed");
65: return -1;
1.1 markus 66: }
67:
68: rlen = BN_num_bytes(sig->r);
69: slen = BN_num_bytes(sig->s);
70: if (rlen > INTBLOB_LEN || slen > INTBLOB_LEN) {
1.15 deraadt 71: error("bad sig size %u %u", rlen, slen);
1.1 markus 72: DSA_SIG_free(sig);
73: return -1;
74: }
75: memset(sigblob, 0, SIGBLOB_LEN);
76: BN_bn2bin(sig->r, sigblob+ SIGBLOB_LEN - INTBLOB_LEN - rlen);
77: BN_bn2bin(sig->s, sigblob+ SIGBLOB_LEN - slen);
78: DSA_SIG_free(sig);
79:
80: if (datafellows & SSH_BUG_SIGBLOB) {
81: if (lenp != NULL)
82: *lenp = SIGBLOB_LEN;
1.17 markus 83: if (sigp != NULL) {
84: *sigp = xmalloc(SIGBLOB_LEN);
85: memcpy(*sigp, sigblob, SIGBLOB_LEN);
86: }
1.1 markus 87: } else {
88: /* ietf-drafts */
89: buffer_init(&b);
90: buffer_put_cstring(&b, "ssh-dss");
91: buffer_put_string(&b, sigblob, SIGBLOB_LEN);
92: len = buffer_len(&b);
93: if (lenp != NULL)
94: *lenp = len;
1.17 markus 95: if (sigp != NULL) {
96: *sigp = xmalloc(len);
97: memcpy(*sigp, buffer_ptr(&b), len);
98: }
99: buffer_free(&b);
1.1 markus 100: }
101: return 0;
102: }
103: int
1.18.4.1! brad 104: ssh_dss_verify(const Key *key, const u_char *signature, u_int signaturelen,
! 105: const u_char *data, u_int datalen)
1.1 markus 106: {
107: DSA_SIG *sig;
1.14 markus 108: const EVP_MD *evp_md = EVP_sha1();
1.1 markus 109: EVP_MD_CTX md;
1.12 markus 110: u_char digest[EVP_MAX_MD_SIZE], *sigblob;
1.2 markus 111: u_int len, dlen;
1.7 markus 112: int rlen, ret;
113: Buffer b;
1.1 markus 114:
115: if (key == NULL || key->type != KEY_DSA || key->dsa == NULL) {
116: error("ssh_dss_verify: no DSA key");
117: return -1;
118: }
119:
120: /* fetch signature */
121: if (datafellows & SSH_BUG_SIGBLOB) {
1.18.4.1! brad 122: sigblob = xmalloc(signaturelen);
! 123: memcpy(sigblob, signature, signaturelen);
1.1 markus 124: len = signaturelen;
125: } else {
126: /* ietf-drafts */
127: char *ktype;
128: buffer_init(&b);
1.8 stevesk 129: buffer_append(&b, signature, signaturelen);
1.1 markus 130: ktype = buffer_get_string(&b, NULL);
131: if (strcmp("ssh-dss", ktype) != 0) {
132: error("ssh_dss_verify: cannot handle type %s", ktype);
133: buffer_free(&b);
1.9 markus 134: xfree(ktype);
1.1 markus 135: return -1;
136: }
1.9 markus 137: xfree(ktype);
1.8 stevesk 138: sigblob = buffer_get_string(&b, &len);
1.1 markus 139: rlen = buffer_len(&b);
1.9 markus 140: buffer_free(&b);
1.10 deraadt 141: if (rlen != 0) {
1.9 markus 142: error("ssh_dss_verify: "
143: "remaining bytes in signature %d", rlen);
144: xfree(sigblob);
1.1 markus 145: return -1;
146: }
147: }
148:
149: if (len != SIGBLOB_LEN) {
1.15 deraadt 150: fatal("bad sigbloblen %u != SIGBLOB_LEN", len);
1.1 markus 151: }
152:
153: /* parse signature */
1.11 markus 154: if ((sig = DSA_SIG_new()) == NULL)
155: fatal("ssh_dss_verify: DSA_SIG_new failed");
156: if ((sig->r = BN_new()) == NULL)
157: fatal("ssh_dss_verify: BN_new failed");
158: if ((sig->s = BN_new()) == NULL)
159: fatal("ssh_dss_verify: BN_new failed");
1.1 markus 160: BN_bin2bn(sigblob, INTBLOB_LEN, sig->r);
161: BN_bin2bn(sigblob+ INTBLOB_LEN, INTBLOB_LEN, sig->s);
162:
1.18.4.1! brad 163: /* clean up */
! 164: memset(sigblob, 0, len);
! 165: xfree(sigblob);
1.5 stevesk 166:
1.1 markus 167: /* sha1 the data */
168: EVP_DigestInit(&md, evp_md);
169: EVP_DigestUpdate(&md, data, datalen);
1.12 markus 170: EVP_DigestFinal(&md, digest, &dlen);
1.1 markus 171:
172: ret = DSA_do_verify(digest, dlen, sig, key->dsa);
1.12 markus 173: memset(digest, 'd', sizeof(digest));
1.1 markus 174:
175: DSA_SIG_free(sig);
176:
1.7 markus 177: debug("ssh_dss_verify: signature %s",
178: ret == 1 ? "correct" : ret == 0 ? "incorrect" : "error");
1.1 markus 179: return ret;
180: }
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