Annotation of src/usr.bin/ssh/ssh-dss.c, Revision 1.3
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"
1.3 ! markus 26: RCSID("$OpenBSD: ssh-dss.c,v 1.2 2000/12/19 23:17:58 markus Exp $");
1.1 markus 27:
28: #include "ssh.h"
29: #include "xmalloc.h"
30: #include "buffer.h"
31: #include "bufaux.h"
32: #include "compat.h"
33:
34: #include <openssl/bn.h>
35: #include <openssl/rsa.h>
36: #include <openssl/dsa.h>
37: #include <openssl/evp.h>
38:
39: #include "key.h"
40:
41: #define INTBLOB_LEN 20
42: #define SIGBLOB_LEN (2*INTBLOB_LEN)
43:
44: int
45: ssh_dss_sign(
46: Key *key,
1.2 markus 47: u_char **sigp, int *lenp,
48: u_char *data, int datalen)
1.1 markus 49: {
1.2 markus 50: u_char *digest;
51: u_char *ret;
1.1 markus 52: DSA_SIG *sig;
53: EVP_MD *evp_md = EVP_sha1();
54: EVP_MD_CTX md;
1.2 markus 55: u_int rlen;
56: u_int slen;
1.3 ! markus 57: u_int len, dlen;
1.2 markus 58: u_char sigblob[SIGBLOB_LEN];
1.1 markus 59: Buffer b;
60:
61: if (key == NULL || key->type != KEY_DSA || key->dsa == NULL) {
62: error("ssh_dss_sign: no DSA key");
63: return -1;
64: }
1.3 ! markus 65: dlen = evp_md->md_size;
! 66: digest = xmalloc(dlen);
1.1 markus 67: EVP_DigestInit(&md, evp_md);
68: EVP_DigestUpdate(&md, data, datalen);
69: EVP_DigestFinal(&md, digest, NULL);
70:
1.3 ! markus 71: sig = DSA_do_sign(digest, dlen, key->dsa);
1.1 markus 72: if (sig == NULL) {
73: fatal("ssh_dss_sign: cannot sign");
74: }
1.3 ! markus 75: memset(digest, 0, dlen);
! 76: xfree(digest);
1.1 markus 77:
78: rlen = BN_num_bytes(sig->r);
79: slen = BN_num_bytes(sig->s);
80: if (rlen > INTBLOB_LEN || slen > INTBLOB_LEN) {
81: error("bad sig size %d %d", rlen, slen);
82: DSA_SIG_free(sig);
83: return -1;
84: }
85: debug("sig size %d %d", rlen, slen);
86:
87: memset(sigblob, 0, SIGBLOB_LEN);
88: BN_bn2bin(sig->r, sigblob+ SIGBLOB_LEN - INTBLOB_LEN - rlen);
89: BN_bn2bin(sig->s, sigblob+ SIGBLOB_LEN - slen);
90: DSA_SIG_free(sig);
91:
92: if (datafellows & SSH_BUG_SIGBLOB) {
93: debug("datafellows");
94: ret = xmalloc(SIGBLOB_LEN);
95: memcpy(ret, sigblob, SIGBLOB_LEN);
96: if (lenp != NULL)
97: *lenp = SIGBLOB_LEN;
98: if (sigp != NULL)
99: *sigp = ret;
100: } else {
101: /* ietf-drafts */
102: buffer_init(&b);
103: buffer_put_cstring(&b, "ssh-dss");
104: buffer_put_string(&b, sigblob, SIGBLOB_LEN);
105: len = buffer_len(&b);
106: ret = xmalloc(len);
107: memcpy(ret, buffer_ptr(&b), len);
108: buffer_free(&b);
109: if (lenp != NULL)
110: *lenp = len;
111: if (sigp != NULL)
112: *sigp = ret;
113: }
114: return 0;
115: }
116: int
117: ssh_dss_verify(
118: Key *key,
1.2 markus 119: u_char *signature, int signaturelen,
120: u_char *data, int datalen)
1.1 markus 121: {
122: Buffer b;
1.2 markus 123: u_char *digest;
1.1 markus 124: DSA_SIG *sig;
125: EVP_MD *evp_md = EVP_sha1();
126: EVP_MD_CTX md;
1.2 markus 127: u_char *sigblob;
1.1 markus 128: char *txt;
1.2 markus 129: u_int len, dlen;
1.1 markus 130: int rlen;
131: int ret;
132:
133: if (key == NULL || key->type != KEY_DSA || key->dsa == NULL) {
134: error("ssh_dss_verify: no DSA key");
135: return -1;
136: }
137:
138: if (!(datafellows & SSH_BUG_SIGBLOB) &&
139: signaturelen == SIGBLOB_LEN) {
140: datafellows |= ~SSH_BUG_SIGBLOB;
141: log("autodetect SSH_BUG_SIGBLOB");
142: } else if ((datafellows & SSH_BUG_SIGBLOB) &&
143: signaturelen != SIGBLOB_LEN) {
144: log("autoremove SSH_BUG_SIGBLOB");
145: datafellows &= ~SSH_BUG_SIGBLOB;
146: }
147:
148: debug("len %d datafellows %d", signaturelen, datafellows);
149:
150: /* fetch signature */
151: if (datafellows & SSH_BUG_SIGBLOB) {
152: sigblob = signature;
153: len = signaturelen;
154: } else {
155: /* ietf-drafts */
156: char *ktype;
157: buffer_init(&b);
158: buffer_append(&b, (char *) signature, signaturelen);
159: ktype = buffer_get_string(&b, NULL);
160: if (strcmp("ssh-dss", ktype) != 0) {
161: error("ssh_dss_verify: cannot handle type %s", ktype);
162: buffer_free(&b);
163: return -1;
164: }
1.2 markus 165: sigblob = (u_char *)buffer_get_string(&b, &len);
1.1 markus 166: rlen = buffer_len(&b);
167: if(rlen != 0) {
168: error("remaining bytes in signature %d", rlen);
169: buffer_free(&b);
170: return -1;
171: }
172: buffer_free(&b);
173: xfree(ktype);
174: }
175:
176: if (len != SIGBLOB_LEN) {
177: fatal("bad sigbloblen %d != SIGBLOB_LEN", len);
178: }
179:
180: /* parse signature */
181: sig = DSA_SIG_new();
182: sig->r = BN_new();
183: sig->s = BN_new();
184: BN_bin2bn(sigblob, INTBLOB_LEN, sig->r);
185: BN_bin2bn(sigblob+ INTBLOB_LEN, INTBLOB_LEN, sig->s);
186:
187: if (!(datafellows & SSH_BUG_SIGBLOB)) {
188: memset(sigblob, 0, len);
189: xfree(sigblob);
190: }
191:
192: /* sha1 the data */
193: dlen = evp_md->md_size;
194: digest = xmalloc(dlen);
195: EVP_DigestInit(&md, evp_md);
196: EVP_DigestUpdate(&md, data, datalen);
197: EVP_DigestFinal(&md, digest, NULL);
198:
199: ret = DSA_do_verify(digest, dlen, sig, key->dsa);
200:
201: memset(digest, 0, dlen);
202: xfree(digest);
203: DSA_SIG_free(sig);
204:
205: switch (ret) {
206: case 1:
207: txt = "correct";
208: break;
209: case 0:
210: txt = "incorrect";
211: break;
212: case -1:
213: default:
214: txt = "error";
215: break;
216: }
217: debug("ssh_dss_verify: signature %s", txt);
218: return ret;
219: }
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