Annotation of src/usr.bin/ssh/ssh-dss.c, Revision 1.20
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"
1.4 markus 26:
27: #include <openssl/bn.h>
28: #include <openssl/evp.h>
1.1 markus 29:
30: #include "xmalloc.h"
31: #include "buffer.h"
32: #include "bufaux.h"
33: #include "compat.h"
1.4 markus 34: #include "log.h"
1.1 markus 35: #include "key.h"
36:
37: #define INTBLOB_LEN 20
38: #define SIGBLOB_LEN (2*INTBLOB_LEN)
39:
40: int
1.19 jakob 41: ssh_dss_sign(const Key *key, u_char **sigp, u_int *lenp,
42: const u_char *data, u_int datalen)
1.1 markus 43: {
44: DSA_SIG *sig;
1.14 markus 45: const EVP_MD *evp_md = EVP_sha1();
1.1 markus 46: EVP_MD_CTX md;
1.17 markus 47: u_char digest[EVP_MAX_MD_SIZE], sigblob[SIGBLOB_LEN];
1.7 markus 48: u_int rlen, slen, len, dlen;
1.1 markus 49: Buffer b;
50:
51: if (key == NULL || key->type != KEY_DSA || key->dsa == NULL) {
52: error("ssh_dss_sign: no DSA key");
53: return -1;
54: }
55: EVP_DigestInit(&md, evp_md);
56: EVP_DigestUpdate(&md, data, datalen);
1.12 markus 57: EVP_DigestFinal(&md, digest, &dlen);
1.1 markus 58:
1.3 markus 59: sig = DSA_do_sign(digest, dlen, key->dsa);
1.12 markus 60: memset(digest, 'd', sizeof(digest));
1.7 markus 61:
1.1 markus 62: if (sig == NULL) {
1.7 markus 63: error("ssh_dss_sign: sign failed");
64: return -1;
1.1 markus 65: }
66:
67: rlen = BN_num_bytes(sig->r);
68: slen = BN_num_bytes(sig->s);
69: if (rlen > INTBLOB_LEN || slen > INTBLOB_LEN) {
1.15 deraadt 70: error("bad sig size %u %u", rlen, slen);
1.1 markus 71: DSA_SIG_free(sig);
72: return -1;
73: }
74: memset(sigblob, 0, SIGBLOB_LEN);
75: BN_bn2bin(sig->r, sigblob+ SIGBLOB_LEN - INTBLOB_LEN - rlen);
76: BN_bn2bin(sig->s, sigblob+ SIGBLOB_LEN - slen);
77: DSA_SIG_free(sig);
78:
79: if (datafellows & SSH_BUG_SIGBLOB) {
80: if (lenp != NULL)
81: *lenp = SIGBLOB_LEN;
1.17 markus 82: if (sigp != NULL) {
83: *sigp = xmalloc(SIGBLOB_LEN);
84: memcpy(*sigp, sigblob, SIGBLOB_LEN);
85: }
1.1 markus 86: } else {
87: /* ietf-drafts */
88: buffer_init(&b);
89: buffer_put_cstring(&b, "ssh-dss");
90: buffer_put_string(&b, sigblob, SIGBLOB_LEN);
91: len = buffer_len(&b);
92: if (lenp != NULL)
93: *lenp = len;
1.17 markus 94: if (sigp != NULL) {
95: *sigp = xmalloc(len);
96: memcpy(*sigp, buffer_ptr(&b), len);
97: }
98: buffer_free(&b);
1.1 markus 99: }
100: return 0;
101: }
102: int
1.19 jakob 103: ssh_dss_verify(const Key *key, const u_char *signature, u_int signaturelen,
104: const u_char *data, u_int datalen)
1.1 markus 105: {
106: DSA_SIG *sig;
1.14 markus 107: const EVP_MD *evp_md = EVP_sha1();
1.1 markus 108: EVP_MD_CTX md;
1.12 markus 109: u_char digest[EVP_MAX_MD_SIZE], *sigblob;
1.2 markus 110: u_int len, dlen;
1.7 markus 111: int rlen, ret;
112: Buffer b;
1.1 markus 113:
114: if (key == NULL || key->type != KEY_DSA || key->dsa == NULL) {
115: error("ssh_dss_verify: no DSA key");
116: return -1;
117: }
118:
119: /* fetch signature */
120: if (datafellows & SSH_BUG_SIGBLOB) {
1.19 jakob 121: sigblob = xmalloc(signaturelen);
122: memcpy(sigblob, signature, signaturelen);
1.1 markus 123: len = signaturelen;
124: } else {
125: /* ietf-drafts */
126: char *ktype;
127: buffer_init(&b);
1.8 stevesk 128: buffer_append(&b, signature, signaturelen);
1.1 markus 129: ktype = buffer_get_string(&b, NULL);
130: if (strcmp("ssh-dss", ktype) != 0) {
131: error("ssh_dss_verify: cannot handle type %s", ktype);
132: buffer_free(&b);
1.9 markus 133: xfree(ktype);
1.1 markus 134: return -1;
135: }
1.9 markus 136: xfree(ktype);
1.8 stevesk 137: sigblob = buffer_get_string(&b, &len);
1.1 markus 138: rlen = buffer_len(&b);
1.9 markus 139: buffer_free(&b);
1.10 deraadt 140: if (rlen != 0) {
1.9 markus 141: error("ssh_dss_verify: "
142: "remaining bytes in signature %d", rlen);
143: xfree(sigblob);
1.1 markus 144: return -1;
145: }
146: }
147:
148: if (len != SIGBLOB_LEN) {
1.15 deraadt 149: fatal("bad sigbloblen %u != SIGBLOB_LEN", len);
1.1 markus 150: }
151:
152: /* parse signature */
1.11 markus 153: if ((sig = DSA_SIG_new()) == NULL)
154: fatal("ssh_dss_verify: DSA_SIG_new failed");
155: if ((sig->r = BN_new()) == NULL)
156: fatal("ssh_dss_verify: BN_new failed");
157: if ((sig->s = BN_new()) == NULL)
158: fatal("ssh_dss_verify: BN_new failed");
1.1 markus 159: BN_bin2bn(sigblob, INTBLOB_LEN, sig->r);
160: BN_bin2bn(sigblob+ INTBLOB_LEN, INTBLOB_LEN, sig->s);
161:
1.19 jakob 162: /* clean up */
163: memset(sigblob, 0, len);
164: xfree(sigblob);
1.5 stevesk 165:
1.1 markus 166: /* sha1 the data */
167: EVP_DigestInit(&md, evp_md);
168: EVP_DigestUpdate(&md, data, datalen);
1.12 markus 169: EVP_DigestFinal(&md, digest, &dlen);
1.1 markus 170:
171: ret = DSA_do_verify(digest, dlen, sig, key->dsa);
1.12 markus 172: memset(digest, 'd', sizeof(digest));
1.1 markus 173:
174: DSA_SIG_free(sig);
175:
1.7 markus 176: debug("ssh_dss_verify: signature %s",
177: ret == 1 ? "correct" : ret == 0 ? "incorrect" : "error");
1.1 markus 178: return ret;
179: }
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