Annotation of src/usr.bin/ssh/ssh-rsa.c, Revision 1.51
1.51 ! djm 1: /* $OpenBSD: ssh-rsa.c,v 1.50 2014/01/09 23:20:00 djm Exp $ */
1.1 markus 2: /*
1.30 markus 3: * Copyright (c) 2000, 2003 Markus Friedl <markus@openbsd.org>
1.1 markus 4: *
1.30 markus 5: * Permission to use, copy, modify, and distribute this software for any
6: * purpose with or without fee is hereby granted, provided that the above
7: * copyright notice and this permission notice appear in all copies.
1.1 markus 8: *
1.30 markus 9: * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
10: * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
11: * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
12: * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
13: * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
14: * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
15: * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
1.1 markus 16: */
1.39 deraadt 17:
18: #include <sys/types.h>
1.5 markus 19:
20: #include <openssl/evp.h>
21: #include <openssl/err.h>
1.38 stevesk 22:
23: #include <string.h>
1.1 markus 24:
25: #include "xmalloc.h"
1.5 markus 26: #include "log.h"
1.1 markus 27: #include "buffer.h"
28: #include "key.h"
1.8 markus 29: #include "compat.h"
1.42 djm 30: #include "misc.h"
1.17 stevesk 31: #include "ssh.h"
1.50 djm 32: #include "digest.h"
1.1 markus 33:
1.27 deraadt 34: static int openssh_RSA_verify(int, u_char *, u_int, u_char *, u_int, RSA *);
1.25 markus 35:
1.1 markus 36: /* RSASSA-PKCS1-v1_5 (PKCS #1 v2.0 signature) with SHA1 */
37: int
1.31 jakob 38: ssh_rsa_sign(const Key *key, u_char **sigp, u_int *lenp,
39: const u_char *data, u_int datalen)
1.1 markus 40: {
1.50 djm 41: int hash_alg;
42: u_char digest[SSH_DIGEST_MAX_LENGTH], *sig;
1.2 markus 43: u_int slen, dlen, len;
1.7 markus 44: int ok, nid;
1.1 markus 45: Buffer b;
46:
1.47 djm 47: if (key == NULL || key_type_plain(key->type) != KEY_RSA ||
48: key->rsa == NULL) {
49: error("%s: no RSA key", __func__);
1.1 markus 50: return -1;
51: }
1.47 djm 52:
1.50 djm 53: /* hash the data */
54: hash_alg = SSH_DIGEST_SHA1;
1.49 djm 55: nid = NID_sha1;
1.50 djm 56: if ((dlen = ssh_digest_bytes(hash_alg)) == 0) {
57: error("%s: bad hash algorithm %d", __func__, hash_alg);
58: return -1;
59: }
60: if (ssh_digest_memory(hash_alg, data, datalen,
61: digest, sizeof(digest)) != 0) {
62: error("%s: ssh_digest_memory failed", __func__);
1.7 markus 63: return -1;
64: }
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);
1.51 ! djm 70: explicit_bzero(digest, sizeof(digest));
1.1 markus 71:
72: if (ok != 1) {
73: int ecode = ERR_get_error();
1.35 deraadt 74:
1.47 djm 75: error("%s: RSA_sign failed: %s", __func__,
1.21 deraadt 76: ERR_error_string(ecode, NULL));
1.46 djm 77: free(sig);
1.1 markus 78: return -1;
79: }
80: if (len < slen) {
1.24 markus 81: u_int diff = slen - len;
1.21 deraadt 82: debug("slen %u > len %u", slen, len);
1.1 markus 83: memmove(sig + diff, sig, len);
1.51 ! djm 84: explicit_bzero(sig, diff);
1.1 markus 85: } else if (len > slen) {
1.47 djm 86: error("%s: slen %u slen2 %u", __func__, slen, len);
1.46 djm 87: free(sig);
1.1 markus 88: return -1;
89: }
90: /* encode signature */
91: buffer_init(&b);
92: buffer_put_cstring(&b, "ssh-rsa");
93: buffer_put_string(&b, sig, slen);
94: len = buffer_len(&b);
1.23 markus 95: if (lenp != NULL)
96: *lenp = len;
97: if (sigp != NULL) {
98: *sigp = xmalloc(len);
99: memcpy(*sigp, buffer_ptr(&b), len);
100: }
1.1 markus 101: buffer_free(&b);
1.51 ! djm 102: explicit_bzero(sig, slen);
1.46 djm 103: free(sig);
1.1 markus 104:
105: return 0;
106: }
107:
108: int
1.31 jakob 109: ssh_rsa_verify(const Key *key, const u_char *signature, u_int signaturelen,
110: const u_char *data, u_int datalen)
1.1 markus 111: {
112: Buffer b;
1.50 djm 113: int hash_alg;
1.1 markus 114: char *ktype;
1.50 djm 115: u_char digest[SSH_DIGEST_MAX_LENGTH], *sigblob;
1.19 markus 116: u_int len, dlen, modlen;
1.50 djm 117: int rlen, ret;
1.1 markus 118:
1.47 djm 119: if (key == NULL || key_type_plain(key->type) != KEY_RSA ||
120: key->rsa == NULL) {
121: error("%s: no RSA key", __func__);
1.4 markus 122: return -1;
123: }
1.47 djm 124:
1.17 stevesk 125: if (BN_num_bits(key->rsa->n) < SSH_RSA_MINIMUM_MODULUS_SIZE) {
1.47 djm 126: error("%s: RSA modulus too small: %d < minimum %d bits",
127: __func__, BN_num_bits(key->rsa->n),
128: SSH_RSA_MINIMUM_MODULUS_SIZE);
1.1 markus 129: return -1;
130: }
131: buffer_init(&b);
1.10 stevesk 132: buffer_append(&b, signature, signaturelen);
1.45 djm 133: ktype = buffer_get_cstring(&b, NULL);
1.1 markus 134: if (strcmp("ssh-rsa", ktype) != 0) {
1.47 djm 135: error("%s: cannot handle type %s", __func__, ktype);
1.1 markus 136: buffer_free(&b);
1.46 djm 137: free(ktype);
1.1 markus 138: return -1;
139: }
1.46 djm 140: free(ktype);
1.10 stevesk 141: sigblob = buffer_get_string(&b, &len);
1.1 markus 142: rlen = buffer_len(&b);
143: buffer_free(&b);
1.14 deraadt 144: if (rlen != 0) {
1.47 djm 145: error("%s: remaining bytes in signature %d", __func__, rlen);
1.46 djm 146: free(sigblob);
1.1 markus 147: return -1;
1.19 markus 148: }
149: /* RSA_verify expects a signature of RSA_size */
150: modlen = RSA_size(key->rsa);
151: if (len > modlen) {
1.47 djm 152: error("%s: len %u > modlen %u", __func__, len, modlen);
1.46 djm 153: free(sigblob);
1.19 markus 154: return -1;
155: } else if (len < modlen) {
1.24 markus 156: u_int diff = modlen - len;
1.47 djm 157: debug("%s: add padding: modlen %u > len %u", __func__,
1.19 markus 158: modlen, len);
1.36 djm 159: sigblob = xrealloc(sigblob, 1, modlen);
1.19 markus 160: memmove(sigblob + diff, sigblob, len);
1.51 ! djm 161: explicit_bzero(sigblob, diff);
1.19 markus 162: len = modlen;
1.1 markus 163: }
1.50 djm 164: /* hash the data */
165: hash_alg = SSH_DIGEST_SHA1;
166: if ((dlen = ssh_digest_bytes(hash_alg)) == 0) {
167: error("%s: bad hash algorithm %d", __func__, hash_alg);
168: return -1;
169: }
170: if (ssh_digest_memory(hash_alg, data, datalen,
171: digest, sizeof(digest)) != 0) {
172: error("%s: ssh_digest_memory failed", __func__);
1.7 markus 173: return -1;
174: }
1.1 markus 175:
1.50 djm 176: ret = openssh_RSA_verify(hash_alg, digest, dlen, sigblob, len,
177: key->rsa);
1.51 ! djm 178: explicit_bzero(digest, sizeof(digest));
! 179: explicit_bzero(sigblob, len);
1.46 djm 180: free(sigblob);
1.47 djm 181: debug("%s: signature %scorrect", __func__, (ret == 0) ? "in" : "");
1.25 markus 182: return ret;
183: }
184:
185: /*
186: * See:
187: * http://www.rsasecurity.com/rsalabs/pkcs/pkcs-1/
188: * ftp://ftp.rsasecurity.com/pub/pkcs/pkcs-1/pkcs-1v2-1.asn
189: */
190: /*
191: * id-sha1 OBJECT IDENTIFIER ::= { iso(1) identified-organization(3)
192: * oiw(14) secsig(3) algorithms(2) 26 }
193: */
194: static const u_char id_sha1[] = {
195: 0x30, 0x21, /* type Sequence, length 0x21 (33) */
196: 0x30, 0x09, /* type Sequence, length 0x09 */
197: 0x06, 0x05, /* type OID, length 0x05 */
198: 0x2b, 0x0e, 0x03, 0x02, 0x1a, /* id-sha1 OID */
199: 0x05, 0x00, /* NULL */
200: 0x04, 0x14 /* Octet string, length 0x14 (20), followed by sha1 hash */
201: };
202:
203: static int
1.50 djm 204: openssh_RSA_verify(int hash_alg, u_char *hash, u_int hashlen,
1.25 markus 205: u_char *sigbuf, u_int siglen, RSA *rsa)
206: {
1.26 stevesk 207: u_int ret, rsasize, oidlen = 0, hlen = 0;
1.44 djm 208: int len, oidmatch, hashmatch;
1.25 markus 209: const u_char *oid = NULL;
210: u_char *decrypted = NULL;
211:
212: ret = 0;
1.50 djm 213: switch (hash_alg) {
214: case SSH_DIGEST_SHA1:
1.25 markus 215: oid = id_sha1;
216: oidlen = sizeof(id_sha1);
217: hlen = 20;
218: break;
219: default:
220: goto done;
221: }
222: if (hashlen != hlen) {
223: error("bad hashlen");
224: goto done;
225: }
226: rsasize = RSA_size(rsa);
227: if (siglen == 0 || siglen > rsasize) {
228: error("bad siglen");
229: goto done;
230: }
231: decrypted = xmalloc(rsasize);
232: if ((len = RSA_public_decrypt(siglen, sigbuf, decrypted, rsa,
233: RSA_PKCS1_PADDING)) < 0) {
234: error("RSA_public_decrypt failed: %s",
235: ERR_error_string(ERR_get_error(), NULL));
236: goto done;
237: }
1.32 djm 238: if (len < 0 || (u_int)len != hlen + oidlen) {
1.30 markus 239: error("bad decrypted len: %d != %d + %d", len, hlen, oidlen);
1.25 markus 240: goto done;
241: }
1.44 djm 242: oidmatch = timingsafe_bcmp(decrypted, oid, oidlen) == 0;
243: hashmatch = timingsafe_bcmp(decrypted + oidlen, hash, hlen) == 0;
244: if (!oidmatch) {
1.25 markus 245: error("oid mismatch");
246: goto done;
247: }
1.44 djm 248: if (!hashmatch) {
1.25 markus 249: error("hash mismatch");
250: goto done;
251: }
252: ret = 1;
253: done:
1.46 djm 254: free(decrypted);
1.1 markus 255: return ret;
256: }
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