Annotation of src/usr.bin/ssh/ssh-rsa.c, Revision 1.28
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"
1.28 ! markus 26: RCSID("$OpenBSD: ssh-rsa.c,v 1.27 2002/11/21 23:03:51 deraadt Exp $");
1.5 markus 27:
28: #include <openssl/evp.h>
29: #include <openssl/err.h>
1.1 markus 30:
31: #include "xmalloc.h"
1.5 markus 32: #include "log.h"
1.1 markus 33: #include "buffer.h"
34: #include "bufaux.h"
35: #include "key.h"
1.8 markus 36: #include "compat.h"
1.17 stevesk 37: #include "ssh.h"
1.1 markus 38:
1.27 deraadt 39: static int openssh_RSA_verify(int, u_char *, u_int, u_char *, u_int, RSA *);
1.25 markus 40:
1.1 markus 41: /* RSASSA-PKCS1-v1_5 (PKCS #1 v2.0 signature) with SHA1 */
42: int
1.21 deraadt 43: ssh_rsa_sign(Key *key, u_char **sigp, u_int *lenp,
1.16 markus 44: u_char *data, u_int datalen)
1.1 markus 45: {
1.7 markus 46: const EVP_MD *evp_md;
1.1 markus 47: EVP_MD_CTX md;
1.23 markus 48: u_char digest[EVP_MAX_MD_SIZE], *sig;
1.2 markus 49: u_int slen, dlen, len;
1.7 markus 50: int ok, nid;
1.1 markus 51: Buffer b;
52:
53: if (key == NULL || key->type != KEY_RSA || key->rsa == NULL) {
54: error("ssh_rsa_sign: no RSA key");
55: return -1;
56: }
1.8 markus 57: nid = (datafellows & SSH_BUG_RSASIGMD5) ? NID_md5 : NID_sha1;
1.7 markus 58: if ((evp_md = EVP_get_digestbynid(nid)) == NULL) {
59: error("ssh_rsa_sign: EVP_get_digestbynid %d failed", nid);
60: return -1;
61: }
1.1 markus 62: EVP_DigestInit(&md, evp_md);
63: EVP_DigestUpdate(&md, data, datalen);
1.15 markus 64: EVP_DigestFinal(&md, digest, &dlen);
1.1 markus 65:
1.7 markus 66: slen = RSA_size(key->rsa);
67: sig = xmalloc(slen);
68:
69: ok = RSA_sign(nid, digest, dlen, sig, &len, key->rsa);
1.15 markus 70: memset(digest, 'd', sizeof(digest));
1.1 markus 71:
72: if (ok != 1) {
73: int ecode = ERR_get_error();
1.21 deraadt 74: error("ssh_rsa_sign: RSA_sign failed: %s",
75: ERR_error_string(ecode, NULL));
1.1 markus 76: xfree(sig);
77: return -1;
78: }
79: if (len < slen) {
1.24 markus 80: u_int diff = slen - len;
1.21 deraadt 81: debug("slen %u > len %u", slen, len);
1.1 markus 82: memmove(sig + diff, sig, len);
83: memset(sig, 0, diff);
84: } else if (len > slen) {
1.21 deraadt 85: error("ssh_rsa_sign: slen %u slen2 %u", slen, len);
1.1 markus 86: xfree(sig);
87: return -1;
88: }
89: /* encode signature */
90: buffer_init(&b);
91: buffer_put_cstring(&b, "ssh-rsa");
92: buffer_put_string(&b, sig, slen);
93: len = buffer_len(&b);
1.23 markus 94: if (lenp != NULL)
95: *lenp = len;
96: if (sigp != NULL) {
97: *sigp = xmalloc(len);
98: memcpy(*sigp, buffer_ptr(&b), len);
99: }
1.1 markus 100: buffer_free(&b);
101: memset(sig, 's', slen);
102: xfree(sig);
103:
104: return 0;
105: }
106:
107: int
1.21 deraadt 108: ssh_rsa_verify(Key *key, u_char *signature, u_int signaturelen,
1.16 markus 109: u_char *data, u_int datalen)
1.1 markus 110: {
111: Buffer b;
1.7 markus 112: const EVP_MD *evp_md;
1.1 markus 113: EVP_MD_CTX md;
114: char *ktype;
1.15 markus 115: u_char digest[EVP_MAX_MD_SIZE], *sigblob;
1.19 markus 116: u_int len, dlen, modlen;
1.7 markus 117: int rlen, ret, nid;
1.1 markus 118:
119: if (key == NULL || key->type != KEY_RSA || key->rsa == NULL) {
120: error("ssh_rsa_verify: no RSA key");
1.4 markus 121: return -1;
122: }
1.17 stevesk 123: if (BN_num_bits(key->rsa->n) < SSH_RSA_MINIMUM_MODULUS_SIZE) {
1.20 stevesk 124: error("ssh_rsa_verify: RSA modulus too small: %d < minimum %d bits",
125: BN_num_bits(key->rsa->n), SSH_RSA_MINIMUM_MODULUS_SIZE);
1.1 markus 126: return -1;
127: }
128: buffer_init(&b);
1.10 stevesk 129: buffer_append(&b, signature, signaturelen);
1.1 markus 130: ktype = buffer_get_string(&b, NULL);
131: if (strcmp("ssh-rsa", ktype) != 0) {
132: error("ssh_rsa_verify: cannot handle type %s", ktype);
133: buffer_free(&b);
134: xfree(ktype);
135: return -1;
136: }
137: xfree(ktype);
1.10 stevesk 138: sigblob = buffer_get_string(&b, &len);
1.1 markus 139: rlen = buffer_len(&b);
140: buffer_free(&b);
1.14 deraadt 141: if (rlen != 0) {
1.12 markus 142: error("ssh_rsa_verify: remaining bytes in signature %d", rlen);
1.7 markus 143: xfree(sigblob);
1.1 markus 144: return -1;
1.19 markus 145: }
146: /* RSA_verify expects a signature of RSA_size */
147: modlen = RSA_size(key->rsa);
148: if (len > modlen) {
1.21 deraadt 149: error("ssh_rsa_verify: len %u > modlen %u", len, modlen);
1.19 markus 150: xfree(sigblob);
151: return -1;
152: } else if (len < modlen) {
1.24 markus 153: u_int diff = modlen - len;
1.21 deraadt 154: debug("ssh_rsa_verify: add padding: modlen %u > len %u",
1.19 markus 155: modlen, len);
156: sigblob = xrealloc(sigblob, modlen);
157: memmove(sigblob + diff, sigblob, len);
158: memset(sigblob, 0, diff);
159: len = modlen;
1.1 markus 160: }
1.8 markus 161: nid = (datafellows & SSH_BUG_RSASIGMD5) ? NID_md5 : NID_sha1;
1.7 markus 162: if ((evp_md = EVP_get_digestbynid(nid)) == NULL) {
1.12 markus 163: error("ssh_rsa_verify: EVP_get_digestbynid %d failed", nid);
1.7 markus 164: xfree(sigblob);
165: return -1;
166: }
1.1 markus 167: EVP_DigestInit(&md, evp_md);
168: EVP_DigestUpdate(&md, data, datalen);
1.15 markus 169: EVP_DigestFinal(&md, digest, &dlen);
1.1 markus 170:
1.25 markus 171: ret = openssh_RSA_verify(nid, digest, dlen, sigblob, len, key->rsa);
1.15 markus 172: memset(digest, 'd', sizeof(digest));
1.1 markus 173: memset(sigblob, 's', len);
174: xfree(sigblob);
175: debug("ssh_rsa_verify: signature %scorrect", (ret==0) ? "in" : "");
1.25 markus 176: return ret;
177: }
178:
179: /*
180: * See:
181: * http://www.rsasecurity.com/rsalabs/pkcs/pkcs-1/
182: * ftp://ftp.rsasecurity.com/pub/pkcs/pkcs-1/pkcs-1v2-1.asn
183: */
184: /*
185: * id-sha1 OBJECT IDENTIFIER ::= { iso(1) identified-organization(3)
186: * oiw(14) secsig(3) algorithms(2) 26 }
187: */
188: static const u_char id_sha1[] = {
189: 0x30, 0x21, /* type Sequence, length 0x21 (33) */
190: 0x30, 0x09, /* type Sequence, length 0x09 */
191: 0x06, 0x05, /* type OID, length 0x05 */
192: 0x2b, 0x0e, 0x03, 0x02, 0x1a, /* id-sha1 OID */
193: 0x05, 0x00, /* NULL */
194: 0x04, 0x14 /* Octet string, length 0x14 (20), followed by sha1 hash */
195: };
196: /*
197: * id-md5 OBJECT IDENTIFIER ::= { iso(1) member-body(2) us(840)
198: * rsadsi(113549) digestAlgorithm(2) 5 }
199: */
200: static const u_char id_md5[] = {
201: 0x30, 0x20, /* type Sequence, length 0x20 (32) */
202: 0x30, 0x0c, /* type Sequence, length 0x09 */
203: 0x06, 0x08, /* type OID, length 0x05 */
204: 0x2a, 0x86, 0x48, 0x86, 0xF7, 0x0D, 0x02, 0x05, /* id-md5 */
205: 0x05, 0x00, /* NULL */
206: 0x04, 0x10 /* Octet string, length 0x10 (16), followed by md5 hash */
207: };
208:
209: static int
210: openssh_RSA_verify(int type, u_char *hash, u_int hashlen,
211: u_char *sigbuf, u_int siglen, RSA *rsa)
212: {
1.26 stevesk 213: u_int ret, rsasize, oidlen = 0, hlen = 0;
214: int len;
1.25 markus 215: const u_char *oid = NULL;
216: u_char *decrypted = NULL;
217:
218: ret = 0;
219: switch (type) {
220: case NID_sha1:
221: oid = id_sha1;
222: oidlen = sizeof(id_sha1);
223: hlen = 20;
224: break;
225: case NID_md5:
226: oid = id_md5;
227: oidlen = sizeof(id_md5);
228: hlen = 16;
229: break;
230: default:
231: goto done;
232: break;
233: }
234: if (hashlen != hlen) {
235: error("bad hashlen");
236: goto done;
237: }
238: rsasize = RSA_size(rsa);
239: if (siglen == 0 || siglen > rsasize) {
240: error("bad siglen");
241: goto done;
242: }
243: decrypted = xmalloc(rsasize);
244: if ((len = RSA_public_decrypt(siglen, sigbuf, decrypted, rsa,
245: RSA_PKCS1_PADDING)) < 0) {
246: error("RSA_public_decrypt failed: %s",
247: ERR_error_string(ERR_get_error(), NULL));
248: goto done;
249: }
250: if (len != hlen + oidlen) {
251: error("bad decrypted len: %d != %d + %d", len, hlen, oidlen);
252: goto done;
253: }
254: if (memcmp(decrypted, oid, oidlen) != 0) {
255: error("oid mismatch");
256: goto done;
257: }
258: if (memcmp(decrypted + oidlen, hash, hlen) != 0) {
259: error("hash mismatch");
260: goto done;
261: }
262: ret = 1;
263: done:
264: if (decrypted)
265: xfree(decrypted);
1.1 markus 266: return ret;
267: }
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