Annotation of src/usr.bin/ssh/ssh-rsa.c, Revision 1.32.2.1
1.32.2.1! brad 1: /* $OpenBSD: ssh-rsa.c,v 1.39 2006/08/03 03:34:42 deraadt 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: */
1.32.2.1! brad 17:
! 18: #include <sys/types.h>
1.5 markus 19:
20: #include <openssl/evp.h>
21: #include <openssl/err.h>
1.1 markus 22:
1.32.2.1! brad 23: #include <string.h>
! 24:
1.1 markus 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"
1.17 stevesk 30: #include "ssh.h"
1.1 markus 31:
1.27 deraadt 32: static int openssh_RSA_verify(int, u_char *, u_int, u_char *, u_int, RSA *);
1.25 markus 33:
1.1 markus 34: /* RSASSA-PKCS1-v1_5 (PKCS #1 v2.0 signature) with SHA1 */
35: int
1.31 jakob 36: ssh_rsa_sign(const Key *key, u_char **sigp, u_int *lenp,
37: const u_char *data, u_int datalen)
1.1 markus 38: {
1.7 markus 39: const EVP_MD *evp_md;
1.1 markus 40: EVP_MD_CTX md;
1.23 markus 41: u_char digest[EVP_MAX_MD_SIZE], *sig;
1.2 markus 42: u_int slen, dlen, len;
1.7 markus 43: int ok, nid;
1.1 markus 44: Buffer b;
45:
46: if (key == NULL || key->type != KEY_RSA || key->rsa == NULL) {
47: error("ssh_rsa_sign: no RSA key");
48: return -1;
49: }
1.8 markus 50: nid = (datafellows & SSH_BUG_RSASIGMD5) ? NID_md5 : NID_sha1;
1.7 markus 51: if ((evp_md = EVP_get_digestbynid(nid)) == NULL) {
52: error("ssh_rsa_sign: EVP_get_digestbynid %d failed", nid);
53: return -1;
54: }
1.1 markus 55: EVP_DigestInit(&md, evp_md);
56: EVP_DigestUpdate(&md, data, datalen);
1.15 markus 57: EVP_DigestFinal(&md, digest, &dlen);
1.1 markus 58:
1.7 markus 59: slen = RSA_size(key->rsa);
60: sig = xmalloc(slen);
61:
62: ok = RSA_sign(nid, digest, dlen, sig, &len, key->rsa);
1.15 markus 63: memset(digest, 'd', sizeof(digest));
1.1 markus 64:
65: if (ok != 1) {
66: int ecode = ERR_get_error();
1.32.2.1! brad 67:
1.21 deraadt 68: error("ssh_rsa_sign: RSA_sign failed: %s",
69: ERR_error_string(ecode, NULL));
1.1 markus 70: xfree(sig);
71: return -1;
72: }
73: if (len < slen) {
1.24 markus 74: u_int diff = slen - len;
1.21 deraadt 75: debug("slen %u > len %u", slen, len);
1.1 markus 76: memmove(sig + diff, sig, len);
77: memset(sig, 0, diff);
78: } else if (len > slen) {
1.21 deraadt 79: error("ssh_rsa_sign: slen %u slen2 %u", slen, len);
1.1 markus 80: xfree(sig);
81: return -1;
82: }
83: /* encode signature */
84: buffer_init(&b);
85: buffer_put_cstring(&b, "ssh-rsa");
86: buffer_put_string(&b, sig, slen);
87: len = buffer_len(&b);
1.23 markus 88: if (lenp != NULL)
89: *lenp = len;
90: if (sigp != NULL) {
91: *sigp = xmalloc(len);
92: memcpy(*sigp, buffer_ptr(&b), len);
93: }
1.1 markus 94: buffer_free(&b);
95: memset(sig, 's', slen);
96: xfree(sig);
97:
98: return 0;
99: }
100:
101: int
1.31 jakob 102: ssh_rsa_verify(const Key *key, const u_char *signature, u_int signaturelen,
103: const u_char *data, u_int datalen)
1.1 markus 104: {
105: Buffer b;
1.7 markus 106: const EVP_MD *evp_md;
1.1 markus 107: EVP_MD_CTX md;
108: char *ktype;
1.15 markus 109: u_char digest[EVP_MAX_MD_SIZE], *sigblob;
1.19 markus 110: u_int len, dlen, modlen;
1.7 markus 111: int rlen, ret, nid;
1.1 markus 112:
113: if (key == NULL || key->type != KEY_RSA || key->rsa == NULL) {
114: error("ssh_rsa_verify: no RSA key");
1.4 markus 115: return -1;
116: }
1.17 stevesk 117: if (BN_num_bits(key->rsa->n) < SSH_RSA_MINIMUM_MODULUS_SIZE) {
1.20 stevesk 118: error("ssh_rsa_verify: RSA modulus too small: %d < minimum %d bits",
119: BN_num_bits(key->rsa->n), SSH_RSA_MINIMUM_MODULUS_SIZE);
1.1 markus 120: return -1;
121: }
122: buffer_init(&b);
1.10 stevesk 123: buffer_append(&b, signature, signaturelen);
1.1 markus 124: ktype = buffer_get_string(&b, NULL);
125: if (strcmp("ssh-rsa", ktype) != 0) {
126: error("ssh_rsa_verify: cannot handle type %s", ktype);
127: buffer_free(&b);
128: xfree(ktype);
129: return -1;
130: }
131: xfree(ktype);
1.10 stevesk 132: sigblob = buffer_get_string(&b, &len);
1.1 markus 133: rlen = buffer_len(&b);
134: buffer_free(&b);
1.14 deraadt 135: if (rlen != 0) {
1.12 markus 136: error("ssh_rsa_verify: remaining bytes in signature %d", rlen);
1.7 markus 137: xfree(sigblob);
1.1 markus 138: return -1;
1.19 markus 139: }
140: /* RSA_verify expects a signature of RSA_size */
141: modlen = RSA_size(key->rsa);
142: if (len > modlen) {
1.21 deraadt 143: error("ssh_rsa_verify: len %u > modlen %u", len, modlen);
1.19 markus 144: xfree(sigblob);
145: return -1;
146: } else if (len < modlen) {
1.24 markus 147: u_int diff = modlen - len;
1.21 deraadt 148: debug("ssh_rsa_verify: add padding: modlen %u > len %u",
1.19 markus 149: modlen, len);
1.32.2.1! brad 150: sigblob = xrealloc(sigblob, 1, modlen);
1.19 markus 151: memmove(sigblob + diff, sigblob, len);
152: memset(sigblob, 0, diff);
153: len = modlen;
1.1 markus 154: }
1.8 markus 155: nid = (datafellows & SSH_BUG_RSASIGMD5) ? NID_md5 : NID_sha1;
1.7 markus 156: if ((evp_md = EVP_get_digestbynid(nid)) == NULL) {
1.12 markus 157: error("ssh_rsa_verify: EVP_get_digestbynid %d failed", nid);
1.7 markus 158: xfree(sigblob);
159: return -1;
160: }
1.1 markus 161: EVP_DigestInit(&md, evp_md);
162: EVP_DigestUpdate(&md, data, datalen);
1.15 markus 163: EVP_DigestFinal(&md, digest, &dlen);
1.1 markus 164:
1.25 markus 165: ret = openssh_RSA_verify(nid, digest, dlen, sigblob, len, key->rsa);
1.15 markus 166: memset(digest, 'd', sizeof(digest));
1.1 markus 167: memset(sigblob, 's', len);
168: xfree(sigblob);
169: debug("ssh_rsa_verify: signature %scorrect", (ret==0) ? "in" : "");
1.25 markus 170: return ret;
171: }
172:
173: /*
174: * See:
175: * http://www.rsasecurity.com/rsalabs/pkcs/pkcs-1/
176: * ftp://ftp.rsasecurity.com/pub/pkcs/pkcs-1/pkcs-1v2-1.asn
177: */
178: /*
179: * id-sha1 OBJECT IDENTIFIER ::= { iso(1) identified-organization(3)
180: * oiw(14) secsig(3) algorithms(2) 26 }
181: */
182: static const u_char id_sha1[] = {
183: 0x30, 0x21, /* type Sequence, length 0x21 (33) */
184: 0x30, 0x09, /* type Sequence, length 0x09 */
185: 0x06, 0x05, /* type OID, length 0x05 */
186: 0x2b, 0x0e, 0x03, 0x02, 0x1a, /* id-sha1 OID */
187: 0x05, 0x00, /* NULL */
188: 0x04, 0x14 /* Octet string, length 0x14 (20), followed by sha1 hash */
189: };
190: /*
191: * id-md5 OBJECT IDENTIFIER ::= { iso(1) member-body(2) us(840)
192: * rsadsi(113549) digestAlgorithm(2) 5 }
193: */
194: static const u_char id_md5[] = {
195: 0x30, 0x20, /* type Sequence, length 0x20 (32) */
196: 0x30, 0x0c, /* type Sequence, length 0x09 */
197: 0x06, 0x08, /* type OID, length 0x05 */
198: 0x2a, 0x86, 0x48, 0x86, 0xF7, 0x0D, 0x02, 0x05, /* id-md5 */
199: 0x05, 0x00, /* NULL */
200: 0x04, 0x10 /* Octet string, length 0x10 (16), followed by md5 hash */
201: };
202:
203: static int
204: openssh_RSA_verify(int type, u_char *hash, u_int hashlen,
205: u_char *sigbuf, u_int siglen, RSA *rsa)
206: {
1.26 stevesk 207: u_int ret, rsasize, oidlen = 0, hlen = 0;
208: int len;
1.25 markus 209: const u_char *oid = NULL;
210: u_char *decrypted = NULL;
211:
212: ret = 0;
213: switch (type) {
214: case NID_sha1:
215: oid = id_sha1;
216: oidlen = sizeof(id_sha1);
217: hlen = 20;
218: break;
219: case NID_md5:
220: oid = id_md5;
221: oidlen = sizeof(id_md5);
222: hlen = 16;
223: break;
224: default:
225: goto done;
226: }
227: if (hashlen != hlen) {
228: error("bad hashlen");
229: goto done;
230: }
231: rsasize = RSA_size(rsa);
232: if (siglen == 0 || siglen > rsasize) {
233: error("bad siglen");
234: goto done;
235: }
236: decrypted = xmalloc(rsasize);
237: if ((len = RSA_public_decrypt(siglen, sigbuf, decrypted, rsa,
238: RSA_PKCS1_PADDING)) < 0) {
239: error("RSA_public_decrypt failed: %s",
240: ERR_error_string(ERR_get_error(), NULL));
241: goto done;
242: }
1.32 djm 243: if (len < 0 || (u_int)len != hlen + oidlen) {
1.30 markus 244: error("bad decrypted len: %d != %d + %d", len, hlen, oidlen);
1.25 markus 245: goto done;
246: }
247: if (memcmp(decrypted, oid, oidlen) != 0) {
248: error("oid mismatch");
249: goto done;
250: }
251: if (memcmp(decrypted + oidlen, hash, hlen) != 0) {
252: error("hash mismatch");
253: goto done;
254: }
255: ret = 1;
256: done:
257: if (decrypted)
258: xfree(decrypted);
1.1 markus 259: return ret;
260: }
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