Annotation of src/usr.bin/ssh/ssh-rsa.c, Revision 1.37
1.37 ! djm 1: /* $OpenBSD$ */
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: */
17: #include "includes.h"
1.5 markus 18:
19: #include <openssl/evp.h>
20: #include <openssl/err.h>
1.1 markus 21:
22: #include "xmalloc.h"
1.5 markus 23: #include "log.h"
1.1 markus 24: #include "buffer.h"
25: #include "bufaux.h"
26: #include "key.h"
1.8 markus 27: #include "compat.h"
1.17 stevesk 28: #include "ssh.h"
1.1 markus 29:
1.27 deraadt 30: static int openssh_RSA_verify(int, u_char *, u_int, u_char *, u_int, RSA *);
1.25 markus 31:
1.1 markus 32: /* RSASSA-PKCS1-v1_5 (PKCS #1 v2.0 signature) with SHA1 */
33: int
1.31 jakob 34: ssh_rsa_sign(const Key *key, u_char **sigp, u_int *lenp,
35: const u_char *data, u_int datalen)
1.1 markus 36: {
1.7 markus 37: const EVP_MD *evp_md;
1.1 markus 38: EVP_MD_CTX md;
1.23 markus 39: u_char digest[EVP_MAX_MD_SIZE], *sig;
1.2 markus 40: u_int slen, dlen, len;
1.7 markus 41: int ok, nid;
1.1 markus 42: Buffer b;
43:
44: if (key == NULL || key->type != KEY_RSA || key->rsa == NULL) {
45: error("ssh_rsa_sign: no RSA key");
46: return -1;
47: }
1.8 markus 48: nid = (datafellows & SSH_BUG_RSASIGMD5) ? NID_md5 : NID_sha1;
1.7 markus 49: if ((evp_md = EVP_get_digestbynid(nid)) == NULL) {
50: error("ssh_rsa_sign: EVP_get_digestbynid %d failed", nid);
51: return -1;
52: }
1.1 markus 53: EVP_DigestInit(&md, evp_md);
54: EVP_DigestUpdate(&md, data, datalen);
1.15 markus 55: EVP_DigestFinal(&md, digest, &dlen);
1.1 markus 56:
1.7 markus 57: slen = RSA_size(key->rsa);
58: sig = xmalloc(slen);
59:
60: ok = RSA_sign(nid, digest, dlen, sig, &len, key->rsa);
1.15 markus 61: memset(digest, 'd', sizeof(digest));
1.1 markus 62:
63: if (ok != 1) {
64: int ecode = ERR_get_error();
1.35 deraadt 65:
1.21 deraadt 66: error("ssh_rsa_sign: RSA_sign failed: %s",
67: ERR_error_string(ecode, NULL));
1.1 markus 68: xfree(sig);
69: return -1;
70: }
71: if (len < slen) {
1.24 markus 72: u_int diff = slen - len;
1.21 deraadt 73: debug("slen %u > len %u", slen, len);
1.1 markus 74: memmove(sig + diff, sig, len);
75: memset(sig, 0, diff);
76: } else if (len > slen) {
1.21 deraadt 77: error("ssh_rsa_sign: slen %u slen2 %u", slen, len);
1.1 markus 78: xfree(sig);
79: return -1;
80: }
81: /* encode signature */
82: buffer_init(&b);
83: buffer_put_cstring(&b, "ssh-rsa");
84: buffer_put_string(&b, sig, slen);
85: len = buffer_len(&b);
1.23 markus 86: if (lenp != NULL)
87: *lenp = len;
88: if (sigp != NULL) {
89: *sigp = xmalloc(len);
90: memcpy(*sigp, buffer_ptr(&b), len);
91: }
1.1 markus 92: buffer_free(&b);
93: memset(sig, 's', slen);
94: xfree(sig);
95:
96: return 0;
97: }
98:
99: int
1.31 jakob 100: ssh_rsa_verify(const Key *key, const u_char *signature, u_int signaturelen,
101: const u_char *data, u_int datalen)
1.1 markus 102: {
103: Buffer b;
1.7 markus 104: const EVP_MD *evp_md;
1.1 markus 105: EVP_MD_CTX md;
106: char *ktype;
1.15 markus 107: u_char digest[EVP_MAX_MD_SIZE], *sigblob;
1.19 markus 108: u_int len, dlen, modlen;
1.7 markus 109: int rlen, ret, nid;
1.1 markus 110:
111: if (key == NULL || key->type != KEY_RSA || key->rsa == NULL) {
112: error("ssh_rsa_verify: no RSA key");
1.4 markus 113: return -1;
114: }
1.17 stevesk 115: if (BN_num_bits(key->rsa->n) < SSH_RSA_MINIMUM_MODULUS_SIZE) {
1.20 stevesk 116: error("ssh_rsa_verify: RSA modulus too small: %d < minimum %d bits",
117: BN_num_bits(key->rsa->n), SSH_RSA_MINIMUM_MODULUS_SIZE);
1.1 markus 118: return -1;
119: }
120: buffer_init(&b);
1.10 stevesk 121: buffer_append(&b, signature, signaturelen);
1.1 markus 122: ktype = buffer_get_string(&b, NULL);
123: if (strcmp("ssh-rsa", ktype) != 0) {
124: error("ssh_rsa_verify: cannot handle type %s", ktype);
125: buffer_free(&b);
126: xfree(ktype);
127: return -1;
128: }
129: xfree(ktype);
1.10 stevesk 130: sigblob = buffer_get_string(&b, &len);
1.1 markus 131: rlen = buffer_len(&b);
132: buffer_free(&b);
1.14 deraadt 133: if (rlen != 0) {
1.12 markus 134: error("ssh_rsa_verify: remaining bytes in signature %d", rlen);
1.7 markus 135: xfree(sigblob);
1.1 markus 136: return -1;
1.19 markus 137: }
138: /* RSA_verify expects a signature of RSA_size */
139: modlen = RSA_size(key->rsa);
140: if (len > modlen) {
1.21 deraadt 141: error("ssh_rsa_verify: len %u > modlen %u", len, modlen);
1.19 markus 142: xfree(sigblob);
143: return -1;
144: } else if (len < modlen) {
1.24 markus 145: u_int diff = modlen - len;
1.21 deraadt 146: debug("ssh_rsa_verify: add padding: modlen %u > len %u",
1.19 markus 147: modlen, len);
1.36 djm 148: sigblob = xrealloc(sigblob, 1, modlen);
1.19 markus 149: memmove(sigblob + diff, sigblob, len);
150: memset(sigblob, 0, diff);
151: len = modlen;
1.1 markus 152: }
1.8 markus 153: nid = (datafellows & SSH_BUG_RSASIGMD5) ? NID_md5 : NID_sha1;
1.7 markus 154: if ((evp_md = EVP_get_digestbynid(nid)) == NULL) {
1.12 markus 155: error("ssh_rsa_verify: EVP_get_digestbynid %d failed", nid);
1.7 markus 156: xfree(sigblob);
157: return -1;
158: }
1.1 markus 159: EVP_DigestInit(&md, evp_md);
160: EVP_DigestUpdate(&md, data, datalen);
1.15 markus 161: EVP_DigestFinal(&md, digest, &dlen);
1.1 markus 162:
1.25 markus 163: ret = openssh_RSA_verify(nid, digest, dlen, sigblob, len, key->rsa);
1.15 markus 164: memset(digest, 'd', sizeof(digest));
1.1 markus 165: memset(sigblob, 's', len);
166: xfree(sigblob);
167: debug("ssh_rsa_verify: signature %scorrect", (ret==0) ? "in" : "");
1.25 markus 168: return ret;
169: }
170:
171: /*
172: * See:
173: * http://www.rsasecurity.com/rsalabs/pkcs/pkcs-1/
174: * ftp://ftp.rsasecurity.com/pub/pkcs/pkcs-1/pkcs-1v2-1.asn
175: */
176: /*
177: * id-sha1 OBJECT IDENTIFIER ::= { iso(1) identified-organization(3)
178: * oiw(14) secsig(3) algorithms(2) 26 }
179: */
180: static const u_char id_sha1[] = {
181: 0x30, 0x21, /* type Sequence, length 0x21 (33) */
182: 0x30, 0x09, /* type Sequence, length 0x09 */
183: 0x06, 0x05, /* type OID, length 0x05 */
184: 0x2b, 0x0e, 0x03, 0x02, 0x1a, /* id-sha1 OID */
185: 0x05, 0x00, /* NULL */
186: 0x04, 0x14 /* Octet string, length 0x14 (20), followed by sha1 hash */
187: };
188: /*
189: * id-md5 OBJECT IDENTIFIER ::= { iso(1) member-body(2) us(840)
190: * rsadsi(113549) digestAlgorithm(2) 5 }
191: */
192: static const u_char id_md5[] = {
193: 0x30, 0x20, /* type Sequence, length 0x20 (32) */
194: 0x30, 0x0c, /* type Sequence, length 0x09 */
195: 0x06, 0x08, /* type OID, length 0x05 */
196: 0x2a, 0x86, 0x48, 0x86, 0xF7, 0x0D, 0x02, 0x05, /* id-md5 */
197: 0x05, 0x00, /* NULL */
198: 0x04, 0x10 /* Octet string, length 0x10 (16), followed by md5 hash */
199: };
200:
201: static int
202: openssh_RSA_verify(int type, u_char *hash, u_int hashlen,
203: u_char *sigbuf, u_int siglen, RSA *rsa)
204: {
1.26 stevesk 205: u_int ret, rsasize, oidlen = 0, hlen = 0;
206: int len;
1.25 markus 207: const u_char *oid = NULL;
208: u_char *decrypted = NULL;
209:
210: ret = 0;
211: switch (type) {
212: case NID_sha1:
213: oid = id_sha1;
214: oidlen = sizeof(id_sha1);
215: hlen = 20;
216: break;
217: case NID_md5:
218: oid = id_md5;
219: oidlen = sizeof(id_md5);
220: hlen = 16;
221: break;
222: default:
223: goto done;
224: }
225: if (hashlen != hlen) {
226: error("bad hashlen");
227: goto done;
228: }
229: rsasize = RSA_size(rsa);
230: if (siglen == 0 || siglen > rsasize) {
231: error("bad siglen");
232: goto done;
233: }
234: decrypted = xmalloc(rsasize);
235: if ((len = RSA_public_decrypt(siglen, sigbuf, decrypted, rsa,
236: RSA_PKCS1_PADDING)) < 0) {
237: error("RSA_public_decrypt failed: %s",
238: ERR_error_string(ERR_get_error(), NULL));
239: goto done;
240: }
1.32 djm 241: if (len < 0 || (u_int)len != hlen + oidlen) {
1.30 markus 242: error("bad decrypted len: %d != %d + %d", len, hlen, oidlen);
1.25 markus 243: goto done;
244: }
245: if (memcmp(decrypted, oid, oidlen) != 0) {
246: error("oid mismatch");
247: goto done;
248: }
249: if (memcmp(decrypted + oidlen, hash, hlen) != 0) {
250: error("hash mismatch");
251: goto done;
252: }
253: ret = 1;
254: done:
255: if (decrypted)
256: xfree(decrypted);
1.1 markus 257: return ret;
258: }