Annotation of src/usr.bin/ssh/ssh-rsa.c, Revision 1.41
1.41 ! djm 1: /* $OpenBSD: ssh-rsa.c,v 1.40 2010/02/26 20:29:54 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"
1.17 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:
1.41 ! djm 46: if (key == NULL || key->rsa == NULL || (key->type != KEY_RSA &&
! 47: key->type != KEY_RSA_CERT && key->type != KEY_RSA_CERT_V00)) {
1.1 markus 48: error("ssh_rsa_sign: no RSA key");
49: return -1;
50: }
1.8 markus 51: nid = (datafellows & SSH_BUG_RSASIGMD5) ? NID_md5 : NID_sha1;
1.7 markus 52: if ((evp_md = EVP_get_digestbynid(nid)) == NULL) {
53: error("ssh_rsa_sign: EVP_get_digestbynid %d failed", nid);
54: return -1;
55: }
1.1 markus 56: EVP_DigestInit(&md, evp_md);
57: EVP_DigestUpdate(&md, data, datalen);
1.15 markus 58: EVP_DigestFinal(&md, digest, &dlen);
1.1 markus 59:
1.7 markus 60: slen = RSA_size(key->rsa);
61: sig = xmalloc(slen);
62:
63: ok = RSA_sign(nid, digest, dlen, sig, &len, key->rsa);
1.15 markus 64: memset(digest, 'd', sizeof(digest));
1.1 markus 65:
66: if (ok != 1) {
67: int ecode = ERR_get_error();
1.35 deraadt 68:
1.21 deraadt 69: error("ssh_rsa_sign: RSA_sign failed: %s",
70: ERR_error_string(ecode, NULL));
1.1 markus 71: xfree(sig);
72: return -1;
73: }
74: if (len < slen) {
1.24 markus 75: u_int diff = slen - len;
1.21 deraadt 76: debug("slen %u > len %u", slen, len);
1.1 markus 77: memmove(sig + diff, sig, len);
78: memset(sig, 0, diff);
79: } else if (len > slen) {
1.21 deraadt 80: error("ssh_rsa_sign: slen %u slen2 %u", slen, len);
1.1 markus 81: xfree(sig);
82: return -1;
83: }
84: /* encode signature */
85: buffer_init(&b);
86: buffer_put_cstring(&b, "ssh-rsa");
87: buffer_put_string(&b, sig, slen);
88: len = buffer_len(&b);
1.23 markus 89: if (lenp != NULL)
90: *lenp = len;
91: if (sigp != NULL) {
92: *sigp = xmalloc(len);
93: memcpy(*sigp, buffer_ptr(&b), len);
94: }
1.1 markus 95: buffer_free(&b);
96: memset(sig, 's', slen);
97: xfree(sig);
98:
99: return 0;
100: }
101:
102: int
1.31 jakob 103: ssh_rsa_verify(const Key *key, const u_char *signature, u_int signaturelen,
104: const u_char *data, u_int datalen)
1.1 markus 105: {
106: Buffer b;
1.7 markus 107: const EVP_MD *evp_md;
1.1 markus 108: EVP_MD_CTX md;
109: char *ktype;
1.15 markus 110: u_char digest[EVP_MAX_MD_SIZE], *sigblob;
1.19 markus 111: u_int len, dlen, modlen;
1.7 markus 112: int rlen, ret, nid;
1.1 markus 113:
1.41 ! djm 114: if (key == NULL || key->rsa == NULL || (key->type != KEY_RSA &&
! 115: key->type != KEY_RSA_CERT && key->type != KEY_RSA_CERT_V00)) {
1.1 markus 116: error("ssh_rsa_verify: no RSA key");
1.4 markus 117: return -1;
118: }
1.17 stevesk 119: if (BN_num_bits(key->rsa->n) < SSH_RSA_MINIMUM_MODULUS_SIZE) {
1.20 stevesk 120: error("ssh_rsa_verify: RSA modulus too small: %d < minimum %d bits",
121: BN_num_bits(key->rsa->n), SSH_RSA_MINIMUM_MODULUS_SIZE);
1.1 markus 122: return -1;
123: }
124: buffer_init(&b);
1.10 stevesk 125: buffer_append(&b, signature, signaturelen);
1.1 markus 126: ktype = buffer_get_string(&b, NULL);
127: if (strcmp("ssh-rsa", ktype) != 0) {
128: error("ssh_rsa_verify: cannot handle type %s", ktype);
129: buffer_free(&b);
130: xfree(ktype);
131: return -1;
132: }
133: xfree(ktype);
1.10 stevesk 134: sigblob = buffer_get_string(&b, &len);
1.1 markus 135: rlen = buffer_len(&b);
136: buffer_free(&b);
1.14 deraadt 137: if (rlen != 0) {
1.12 markus 138: error("ssh_rsa_verify: remaining bytes in signature %d", rlen);
1.7 markus 139: xfree(sigblob);
1.1 markus 140: return -1;
1.19 markus 141: }
142: /* RSA_verify expects a signature of RSA_size */
143: modlen = RSA_size(key->rsa);
144: if (len > modlen) {
1.21 deraadt 145: error("ssh_rsa_verify: len %u > modlen %u", len, modlen);
1.19 markus 146: xfree(sigblob);
147: return -1;
148: } else if (len < modlen) {
1.24 markus 149: u_int diff = modlen - len;
1.21 deraadt 150: debug("ssh_rsa_verify: add padding: modlen %u > len %u",
1.19 markus 151: modlen, len);
1.36 djm 152: sigblob = xrealloc(sigblob, 1, modlen);
1.19 markus 153: memmove(sigblob + diff, sigblob, len);
154: memset(sigblob, 0, diff);
155: len = modlen;
1.1 markus 156: }
1.8 markus 157: nid = (datafellows & SSH_BUG_RSASIGMD5) ? NID_md5 : NID_sha1;
1.7 markus 158: if ((evp_md = EVP_get_digestbynid(nid)) == NULL) {
1.12 markus 159: error("ssh_rsa_verify: EVP_get_digestbynid %d failed", nid);
1.7 markus 160: xfree(sigblob);
161: return -1;
162: }
1.1 markus 163: EVP_DigestInit(&md, evp_md);
164: EVP_DigestUpdate(&md, data, datalen);
1.15 markus 165: EVP_DigestFinal(&md, digest, &dlen);
1.1 markus 166:
1.25 markus 167: ret = openssh_RSA_verify(nid, digest, dlen, sigblob, len, key->rsa);
1.15 markus 168: memset(digest, 'd', sizeof(digest));
1.1 markus 169: memset(sigblob, 's', len);
170: xfree(sigblob);
171: debug("ssh_rsa_verify: signature %scorrect", (ret==0) ? "in" : "");
1.25 markus 172: return ret;
173: }
174:
175: /*
176: * See:
177: * http://www.rsasecurity.com/rsalabs/pkcs/pkcs-1/
178: * ftp://ftp.rsasecurity.com/pub/pkcs/pkcs-1/pkcs-1v2-1.asn
179: */
180: /*
181: * id-sha1 OBJECT IDENTIFIER ::= { iso(1) identified-organization(3)
182: * oiw(14) secsig(3) algorithms(2) 26 }
183: */
184: static const u_char id_sha1[] = {
185: 0x30, 0x21, /* type Sequence, length 0x21 (33) */
186: 0x30, 0x09, /* type Sequence, length 0x09 */
187: 0x06, 0x05, /* type OID, length 0x05 */
188: 0x2b, 0x0e, 0x03, 0x02, 0x1a, /* id-sha1 OID */
189: 0x05, 0x00, /* NULL */
190: 0x04, 0x14 /* Octet string, length 0x14 (20), followed by sha1 hash */
191: };
192: /*
193: * id-md5 OBJECT IDENTIFIER ::= { iso(1) member-body(2) us(840)
194: * rsadsi(113549) digestAlgorithm(2) 5 }
195: */
196: static const u_char id_md5[] = {
197: 0x30, 0x20, /* type Sequence, length 0x20 (32) */
198: 0x30, 0x0c, /* type Sequence, length 0x09 */
199: 0x06, 0x08, /* type OID, length 0x05 */
200: 0x2a, 0x86, 0x48, 0x86, 0xF7, 0x0D, 0x02, 0x05, /* id-md5 */
201: 0x05, 0x00, /* NULL */
202: 0x04, 0x10 /* Octet string, length 0x10 (16), followed by md5 hash */
203: };
204:
205: static int
206: openssh_RSA_verify(int type, u_char *hash, u_int hashlen,
207: u_char *sigbuf, u_int siglen, RSA *rsa)
208: {
1.26 stevesk 209: u_int ret, rsasize, oidlen = 0, hlen = 0;
210: int len;
1.25 markus 211: const u_char *oid = NULL;
212: u_char *decrypted = NULL;
213:
214: ret = 0;
215: switch (type) {
216: case NID_sha1:
217: oid = id_sha1;
218: oidlen = sizeof(id_sha1);
219: hlen = 20;
220: break;
221: case NID_md5:
222: oid = id_md5;
223: oidlen = sizeof(id_md5);
224: hlen = 16;
225: break;
226: default:
227: goto done;
228: }
229: if (hashlen != hlen) {
230: error("bad hashlen");
231: goto done;
232: }
233: rsasize = RSA_size(rsa);
234: if (siglen == 0 || siglen > rsasize) {
235: error("bad siglen");
236: goto done;
237: }
238: decrypted = xmalloc(rsasize);
239: if ((len = RSA_public_decrypt(siglen, sigbuf, decrypted, rsa,
240: RSA_PKCS1_PADDING)) < 0) {
241: error("RSA_public_decrypt failed: %s",
242: ERR_error_string(ERR_get_error(), NULL));
243: goto done;
244: }
1.32 djm 245: if (len < 0 || (u_int)len != hlen + oidlen) {
1.30 markus 246: error("bad decrypted len: %d != %d + %d", len, hlen, oidlen);
1.25 markus 247: goto done;
248: }
249: if (memcmp(decrypted, oid, oidlen) != 0) {
250: error("oid mismatch");
251: goto done;
252: }
253: if (memcmp(decrypted + oidlen, hash, hlen) != 0) {
254: error("hash mismatch");
255: goto done;
256: }
257: ret = 1;
258: done:
259: if (decrypted)
260: xfree(decrypted);
1.1 markus 261: return ret;
262: }
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