Annotation of src/usr.bin/ssh/ssh-rsa.c, Revision 1.48
1.48 ! djm 1: /* $OpenBSD: ssh-rsa.c,v 1.47 2013/12/27 22:30:17 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"
1.1 markus 32:
1.27 deraadt 33: static int openssh_RSA_verify(int, u_char *, u_int, u_char *, u_int, RSA *);
1.25 markus 34:
1.1 markus 35: /* RSASSA-PKCS1-v1_5 (PKCS #1 v2.0 signature) with SHA1 */
36: int
1.31 jakob 37: ssh_rsa_sign(const Key *key, u_char **sigp, u_int *lenp,
38: const u_char *data, u_int datalen)
1.1 markus 39: {
1.7 markus 40: const EVP_MD *evp_md;
1.1 markus 41: EVP_MD_CTX md;
1.23 markus 42: u_char digest[EVP_MAX_MD_SIZE], *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:
1.8 markus 53: nid = (datafellows & SSH_BUG_RSASIGMD5) ? NID_md5 : NID_sha1;
1.7 markus 54: if ((evp_md = EVP_get_digestbynid(nid)) == NULL) {
1.47 djm 55: error("%s: EVP_get_digestbynid %d failed", __func__, nid);
1.7 markus 56: return -1;
57: }
1.1 markus 58: EVP_DigestInit(&md, evp_md);
59: EVP_DigestUpdate(&md, data, datalen);
1.15 markus 60: EVP_DigestFinal(&md, digest, &dlen);
1.1 markus 61:
1.7 markus 62: slen = RSA_size(key->rsa);
63: sig = xmalloc(slen);
64:
65: ok = RSA_sign(nid, digest, dlen, sig, &len, key->rsa);
1.15 markus 66: memset(digest, 'd', sizeof(digest));
1.1 markus 67:
68: if (ok != 1) {
69: int ecode = ERR_get_error();
1.35 deraadt 70:
1.47 djm 71: error("%s: RSA_sign failed: %s", __func__,
1.21 deraadt 72: ERR_error_string(ecode, NULL));
1.46 djm 73: free(sig);
1.1 markus 74: return -1;
75: }
76: if (len < slen) {
1.24 markus 77: u_int diff = slen - len;
1.21 deraadt 78: debug("slen %u > len %u", slen, len);
1.1 markus 79: memmove(sig + diff, sig, len);
80: memset(sig, 0, diff);
81: } else if (len > slen) {
1.47 djm 82: error("%s: slen %u slen2 %u", __func__, slen, len);
1.46 djm 83: free(sig);
1.1 markus 84: return -1;
85: }
86: /* encode signature */
87: buffer_init(&b);
88: buffer_put_cstring(&b, "ssh-rsa");
89: buffer_put_string(&b, sig, slen);
90: len = buffer_len(&b);
1.23 markus 91: if (lenp != NULL)
92: *lenp = len;
93: if (sigp != NULL) {
94: *sigp = xmalloc(len);
95: memcpy(*sigp, buffer_ptr(&b), len);
96: }
1.1 markus 97: buffer_free(&b);
98: memset(sig, 's', slen);
1.46 djm 99: free(sig);
1.1 markus 100:
101: return 0;
102: }
103:
104: int
1.31 jakob 105: ssh_rsa_verify(const Key *key, const u_char *signature, u_int signaturelen,
106: const u_char *data, u_int datalen)
1.1 markus 107: {
108: Buffer b;
1.7 markus 109: const EVP_MD *evp_md;
1.1 markus 110: EVP_MD_CTX md;
111: char *ktype;
1.15 markus 112: u_char digest[EVP_MAX_MD_SIZE], *sigblob;
1.19 markus 113: u_int len, dlen, modlen;
1.7 markus 114: int rlen, ret, nid;
1.1 markus 115:
1.47 djm 116: if (key == NULL || key_type_plain(key->type) != KEY_RSA ||
117: key->rsa == NULL) {
118: error("%s: no RSA key", __func__);
1.4 markus 119: return -1;
120: }
1.47 djm 121:
1.17 stevesk 122: if (BN_num_bits(key->rsa->n) < SSH_RSA_MINIMUM_MODULUS_SIZE) {
1.47 djm 123: error("%s: RSA modulus too small: %d < minimum %d bits",
124: __func__, BN_num_bits(key->rsa->n),
125: 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);
1.45 djm 130: ktype = buffer_get_cstring(&b, NULL);
1.1 markus 131: if (strcmp("ssh-rsa", ktype) != 0) {
1.47 djm 132: error("%s: cannot handle type %s", __func__, ktype);
1.1 markus 133: buffer_free(&b);
1.46 djm 134: free(ktype);
1.1 markus 135: return -1;
136: }
1.46 djm 137: free(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) {
1.47 djm 142: error("%s: remaining bytes in signature %d", __func__, rlen);
1.46 djm 143: free(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) {
1.47 djm 149: error("%s: len %u > modlen %u", __func__, len, modlen);
1.46 djm 150: free(sigblob);
1.19 markus 151: return -1;
152: } else if (len < modlen) {
1.24 markus 153: u_int diff = modlen - len;
1.47 djm 154: debug("%s: add padding: modlen %u > len %u", __func__,
1.19 markus 155: modlen, len);
1.36 djm 156: sigblob = xrealloc(sigblob, 1, modlen);
1.19 markus 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) {
1.47 djm 163: error("%s: EVP_get_digestbynid %d failed", __func__, nid);
1.46 djm 164: free(sigblob);
1.7 markus 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);
1.46 djm 174: free(sigblob);
1.47 djm 175: debug("%s: signature %scorrect", __func__, (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) */
1.48 ! djm 202: 0x30, 0x0c, /* type Sequence, length 0x0c (12) */
! 203: 0x06, 0x08, /* type OID, length 0x08 */
1.25 markus 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;
1.44 djm 214: int len, oidmatch, hashmatch;
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: }
233: if (hashlen != hlen) {
234: error("bad hashlen");
235: goto done;
236: }
237: rsasize = RSA_size(rsa);
238: if (siglen == 0 || siglen > rsasize) {
239: error("bad siglen");
240: goto done;
241: }
242: decrypted = xmalloc(rsasize);
243: if ((len = RSA_public_decrypt(siglen, sigbuf, decrypted, rsa,
244: RSA_PKCS1_PADDING)) < 0) {
245: error("RSA_public_decrypt failed: %s",
246: ERR_error_string(ERR_get_error(), NULL));
247: goto done;
248: }
1.32 djm 249: if (len < 0 || (u_int)len != hlen + oidlen) {
1.30 markus 250: error("bad decrypted len: %d != %d + %d", len, hlen, oidlen);
1.25 markus 251: goto done;
252: }
1.44 djm 253: oidmatch = timingsafe_bcmp(decrypted, oid, oidlen) == 0;
254: hashmatch = timingsafe_bcmp(decrypted + oidlen, hash, hlen) == 0;
255: if (!oidmatch) {
1.25 markus 256: error("oid mismatch");
257: goto done;
258: }
1.44 djm 259: if (!hashmatch) {
1.25 markus 260: error("hash mismatch");
261: goto done;
262: }
263: ret = 1;
264: done:
1.46 djm 265: free(decrypted);
1.1 markus 266: return ret;
267: }