Annotation of src/usr.bin/ssh/ssh-dss.c, Revision 1.26
1.26 ! djm 1: /* $OpenBSD: ssh-dss.c,v 1.25 2010/02/26 20:29:54 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"
38:
39: #define INTBLOB_LEN 20
40: #define SIGBLOB_LEN (2*INTBLOB_LEN)
41:
42: int
1.19 jakob 43: ssh_dss_sign(const Key *key, u_char **sigp, u_int *lenp,
44: const u_char *data, u_int datalen)
1.1 markus 45: {
46: DSA_SIG *sig;
1.14 markus 47: const EVP_MD *evp_md = EVP_sha1();
1.1 markus 48: EVP_MD_CTX md;
1.17 markus 49: u_char digest[EVP_MAX_MD_SIZE], sigblob[SIGBLOB_LEN];
1.7 markus 50: u_int rlen, slen, len, dlen;
1.1 markus 51: Buffer b;
52:
1.26 ! djm 53: if (key == NULL || key->dsa == NULL || (key->type != KEY_DSA &&
! 54: key->type != KEY_DSA_CERT && key->type != KEY_DSA_CERT_V00)) {
1.1 markus 55: error("ssh_dss_sign: no DSA key");
56: return -1;
57: }
58: EVP_DigestInit(&md, evp_md);
59: EVP_DigestUpdate(&md, data, datalen);
1.12 markus 60: EVP_DigestFinal(&md, digest, &dlen);
1.1 markus 61:
1.3 markus 62: sig = DSA_do_sign(digest, dlen, key->dsa);
1.12 markus 63: memset(digest, 'd', sizeof(digest));
1.7 markus 64:
1.1 markus 65: if (sig == NULL) {
1.7 markus 66: error("ssh_dss_sign: sign failed");
67: return -1;
1.1 markus 68: }
69:
70: rlen = BN_num_bytes(sig->r);
71: slen = BN_num_bytes(sig->s);
72: if (rlen > INTBLOB_LEN || slen > INTBLOB_LEN) {
1.15 deraadt 73: error("bad sig size %u %u", rlen, slen);
1.1 markus 74: DSA_SIG_free(sig);
75: return -1;
76: }
77: memset(sigblob, 0, SIGBLOB_LEN);
78: BN_bn2bin(sig->r, sigblob+ SIGBLOB_LEN - INTBLOB_LEN - rlen);
79: BN_bn2bin(sig->s, sigblob+ SIGBLOB_LEN - slen);
80: DSA_SIG_free(sig);
81:
82: if (datafellows & SSH_BUG_SIGBLOB) {
83: if (lenp != NULL)
84: *lenp = SIGBLOB_LEN;
1.17 markus 85: if (sigp != NULL) {
86: *sigp = xmalloc(SIGBLOB_LEN);
87: memcpy(*sigp, sigblob, SIGBLOB_LEN);
88: }
1.1 markus 89: } else {
90: /* ietf-drafts */
91: buffer_init(&b);
92: buffer_put_cstring(&b, "ssh-dss");
93: buffer_put_string(&b, sigblob, SIGBLOB_LEN);
94: len = buffer_len(&b);
95: if (lenp != NULL)
96: *lenp = len;
1.17 markus 97: if (sigp != NULL) {
98: *sigp = xmalloc(len);
99: memcpy(*sigp, buffer_ptr(&b), len);
100: }
101: buffer_free(&b);
1.1 markus 102: }
103: return 0;
104: }
105: int
1.19 jakob 106: ssh_dss_verify(const Key *key, const u_char *signature, u_int signaturelen,
107: const u_char *data, u_int datalen)
1.1 markus 108: {
109: DSA_SIG *sig;
1.14 markus 110: const EVP_MD *evp_md = EVP_sha1();
1.1 markus 111: EVP_MD_CTX md;
1.12 markus 112: u_char digest[EVP_MAX_MD_SIZE], *sigblob;
1.2 markus 113: u_int len, dlen;
1.7 markus 114: int rlen, ret;
115: Buffer b;
1.1 markus 116:
1.26 ! djm 117: if (key == NULL || key->dsa == NULL || (key->type != KEY_DSA &&
! 118: key->type != KEY_DSA_CERT && key->type != KEY_DSA_CERT_V00)) {
1.1 markus 119: error("ssh_dss_verify: no DSA key");
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);
1.1 markus 133: ktype = buffer_get_string(&b, NULL);
134: if (strcmp("ssh-dss", ktype) != 0) {
135: error("ssh_dss_verify: cannot handle type %s", ktype);
136: buffer_free(&b);
1.9 markus 137: xfree(ktype);
1.1 markus 138: return -1;
139: }
1.9 markus 140: xfree(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) {
1.9 markus 145: error("ssh_dss_verify: "
146: "remaining bytes in signature %d", rlen);
147: xfree(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)
158: fatal("ssh_dss_verify: DSA_SIG_new failed");
159: if ((sig->r = BN_new()) == NULL)
160: fatal("ssh_dss_verify: BN_new failed");
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))
165: fatal("ssh_dss_verify: BN_bin2bn failed");
1.1 markus 166:
1.19 jakob 167: /* clean up */
168: memset(sigblob, 0, len);
169: xfree(sigblob);
1.5 stevesk 170:
1.1 markus 171: /* sha1 the data */
172: EVP_DigestInit(&md, evp_md);
173: EVP_DigestUpdate(&md, data, datalen);
1.12 markus 174: EVP_DigestFinal(&md, digest, &dlen);
1.1 markus 175:
176: ret = DSA_do_verify(digest, dlen, sig, key->dsa);
1.12 markus 177: memset(digest, 'd', sizeof(digest));
1.1 markus 178:
179: DSA_SIG_free(sig);
180:
1.7 markus 181: debug("ssh_dss_verify: signature %s",
182: ret == 1 ? "correct" : ret == 0 ? "incorrect" : "error");
1.1 markus 183: return ret;
184: }
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