Annotation of src/usr.bin/ssh/ssh-dss.c, Revision 1.30
1.30 ! djm 1: /* $OpenBSD: ssh-dss.c,v 1.29 2013/12/27 22:30:17 djm Exp $ */
1.1 markus 2: /*
3: * Copyright (c) 2000 Markus Friedl. All rights reserved.
4: *
5: * Redistribution and use in source and binary forms, with or without
6: * modification, are permitted provided that the following conditions
7: * are met:
8: * 1. Redistributions of source code must retain the above copyright
9: * notice, this list of conditions and the following disclaimer.
10: * 2. Redistributions in binary form must reproduce the above copyright
11: * notice, this list of conditions and the following disclaimer in the
12: * documentation and/or other materials provided with the distribution.
13: *
14: * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
15: * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
16: * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
17: * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
18: * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
19: * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
20: * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
21: * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
22: * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
23: * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
24: */
25:
1.23 deraadt 26: #include <sys/types.h>
1.4 markus 27:
28: #include <openssl/bn.h>
29: #include <openssl/evp.h>
1.22 stevesk 30:
31: #include <string.h>
1.1 markus 32:
33: #include "xmalloc.h"
34: #include "buffer.h"
35: #include "compat.h"
1.4 markus 36: #include "log.h"
1.1 markus 37: #include "key.h"
1.30 ! djm 38: #include "digest.h"
1.1 markus 39:
40: #define INTBLOB_LEN 20
41: #define SIGBLOB_LEN (2*INTBLOB_LEN)
42:
43: int
1.19 jakob 44: ssh_dss_sign(const Key *key, u_char **sigp, u_int *lenp,
45: const u_char *data, u_int datalen)
1.1 markus 46: {
47: DSA_SIG *sig;
1.30 ! djm 48: u_char digest[SSH_DIGEST_MAX_LENGTH], sigblob[SIGBLOB_LEN];
! 49: u_int rlen, slen, len, dlen = ssh_digest_bytes(SSH_DIGEST_SHA1);
1.1 markus 50: Buffer b;
51:
1.29 djm 52: if (key == NULL || key_type_plain(key->type) != KEY_DSA ||
53: key->dsa == NULL) {
54: error("%s: no DSA key", __func__);
1.1 markus 55: return -1;
56: }
1.29 djm 57:
1.30 ! djm 58: if (ssh_digest_memory(SSH_DIGEST_SHA1, data, datalen,
! 59: digest, sizeof(digest)) != 0) {
! 60: error("%s: ssh_digest_memory failed", __func__);
! 61: return -1;
! 62: }
1.1 markus 63:
1.3 markus 64: sig = DSA_do_sign(digest, dlen, key->dsa);
1.12 markus 65: memset(digest, 'd', sizeof(digest));
1.7 markus 66:
1.1 markus 67: if (sig == NULL) {
1.7 markus 68: error("ssh_dss_sign: sign failed");
69: return -1;
1.1 markus 70: }
71:
72: rlen = BN_num_bytes(sig->r);
73: slen = BN_num_bytes(sig->s);
74: if (rlen > INTBLOB_LEN || slen > INTBLOB_LEN) {
1.15 deraadt 75: error("bad sig size %u %u", rlen, slen);
1.1 markus 76: DSA_SIG_free(sig);
77: return -1;
78: }
79: memset(sigblob, 0, SIGBLOB_LEN);
80: BN_bn2bin(sig->r, sigblob+ SIGBLOB_LEN - INTBLOB_LEN - rlen);
81: BN_bn2bin(sig->s, sigblob+ SIGBLOB_LEN - slen);
82: DSA_SIG_free(sig);
83:
84: if (datafellows & SSH_BUG_SIGBLOB) {
85: if (lenp != NULL)
86: *lenp = SIGBLOB_LEN;
1.17 markus 87: if (sigp != NULL) {
88: *sigp = xmalloc(SIGBLOB_LEN);
89: memcpy(*sigp, sigblob, SIGBLOB_LEN);
90: }
1.1 markus 91: } else {
92: /* ietf-drafts */
93: buffer_init(&b);
94: buffer_put_cstring(&b, "ssh-dss");
95: buffer_put_string(&b, sigblob, SIGBLOB_LEN);
96: len = buffer_len(&b);
97: if (lenp != NULL)
98: *lenp = len;
1.17 markus 99: if (sigp != NULL) {
100: *sigp = xmalloc(len);
101: memcpy(*sigp, buffer_ptr(&b), len);
102: }
103: buffer_free(&b);
1.1 markus 104: }
105: return 0;
106: }
107: int
1.19 jakob 108: ssh_dss_verify(const Key *key, const u_char *signature, u_int signaturelen,
109: const u_char *data, u_int datalen)
1.1 markus 110: {
111: DSA_SIG *sig;
1.30 ! djm 112: u_char digest[SSH_DIGEST_MAX_LENGTH], *sigblob;
! 113: u_int len, dlen = ssh_digest_bytes(SSH_DIGEST_SHA1);
1.7 markus 114: int rlen, ret;
115: Buffer b;
1.1 markus 116:
1.29 djm 117: if (key == NULL || key_type_plain(key->type) != KEY_DSA ||
118: key->dsa == NULL) {
119: error("%s: no DSA key", __func__);
1.1 markus 120: return -1;
121: }
122:
123: /* fetch signature */
124: if (datafellows & SSH_BUG_SIGBLOB) {
1.19 jakob 125: sigblob = xmalloc(signaturelen);
126: memcpy(sigblob, signature, signaturelen);
1.1 markus 127: len = signaturelen;
128: } else {
129: /* ietf-drafts */
130: char *ktype;
131: buffer_init(&b);
1.8 stevesk 132: buffer_append(&b, signature, signaturelen);
1.27 djm 133: ktype = buffer_get_cstring(&b, NULL);
1.1 markus 134: if (strcmp("ssh-dss", ktype) != 0) {
1.29 djm 135: error("%s: cannot handle type %s", __func__, ktype);
1.1 markus 136: buffer_free(&b);
1.28 djm 137: free(ktype);
1.1 markus 138: return -1;
139: }
1.28 djm 140: free(ktype);
1.8 stevesk 141: sigblob = buffer_get_string(&b, &len);
1.1 markus 142: rlen = buffer_len(&b);
1.9 markus 143: buffer_free(&b);
1.10 deraadt 144: if (rlen != 0) {
1.29 djm 145: error("%s: remaining bytes in signature %d",
146: __func__, rlen);
1.28 djm 147: free(sigblob);
1.1 markus 148: return -1;
149: }
150: }
151:
152: if (len != SIGBLOB_LEN) {
1.15 deraadt 153: fatal("bad sigbloblen %u != SIGBLOB_LEN", len);
1.1 markus 154: }
155:
156: /* parse signature */
1.11 markus 157: if ((sig = DSA_SIG_new()) == NULL)
1.29 djm 158: fatal("%s: DSA_SIG_new failed", __func__);
1.11 markus 159: if ((sig->r = BN_new()) == NULL)
1.29 djm 160: fatal("%s: BN_new failed", __func__);
1.11 markus 161: if ((sig->s = BN_new()) == NULL)
162: fatal("ssh_dss_verify: BN_new failed");
1.24 markus 163: if ((BN_bin2bn(sigblob, INTBLOB_LEN, sig->r) == NULL) ||
164: (BN_bin2bn(sigblob+ INTBLOB_LEN, INTBLOB_LEN, sig->s) == NULL))
1.29 djm 165: fatal("%s: BN_bin2bn failed", __func__);
1.1 markus 166:
1.19 jakob 167: /* clean up */
168: memset(sigblob, 0, len);
1.28 djm 169: free(sigblob);
1.5 stevesk 170:
1.1 markus 171: /* sha1 the data */
1.30 ! djm 172: if (ssh_digest_memory(SSH_DIGEST_SHA1, data, datalen,
! 173: digest, sizeof(digest)) != 0) {
! 174: error("%s: digest_memory failed", __func__);
! 175: return -1;
! 176: }
1.1 markus 177:
178: ret = DSA_do_verify(digest, dlen, sig, key->dsa);
1.12 markus 179: memset(digest, 'd', sizeof(digest));
1.1 markus 180:
181: DSA_SIG_free(sig);
182:
1.29 djm 183: debug("%s: signature %s", __func__,
1.7 markus 184: ret == 1 ? "correct" : ret == 0 ? "incorrect" : "error");
1.1 markus 185: return ret;
186: }
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