Annotation of src/usr.bin/ssh/ssh-rsa.c, Revision 1.40
1.40 ! djm 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: */
1.39 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:
1.40 ! djm 46: if (key == NULL ||
! 47: (key->type != KEY_RSA && key->type != KEY_RSA_CERT) ||
! 48: key->rsa == NULL) {
1.1 markus 49: error("ssh_rsa_sign: no RSA key");
50: return -1;
51: }
1.8 markus 52: nid = (datafellows & SSH_BUG_RSASIGMD5) ? NID_md5 : NID_sha1;
1.7 markus 53: if ((evp_md = EVP_get_digestbynid(nid)) == NULL) {
54: error("ssh_rsa_sign: EVP_get_digestbynid %d failed", nid);
55: return -1;
56: }
1.1 markus 57: EVP_DigestInit(&md, evp_md);
58: EVP_DigestUpdate(&md, data, datalen);
1.15 markus 59: EVP_DigestFinal(&md, digest, &dlen);
1.1 markus 60:
1.7 markus 61: slen = RSA_size(key->rsa);
62: sig = xmalloc(slen);
63:
64: ok = RSA_sign(nid, digest, dlen, sig, &len, key->rsa);
1.15 markus 65: memset(digest, 'd', sizeof(digest));
1.1 markus 66:
67: if (ok != 1) {
68: int ecode = ERR_get_error();
1.35 deraadt 69:
1.21 deraadt 70: error("ssh_rsa_sign: RSA_sign failed: %s",
71: ERR_error_string(ecode, NULL));
1.1 markus 72: xfree(sig);
73: return -1;
74: }
75: if (len < slen) {
1.24 markus 76: u_int diff = slen - len;
1.21 deraadt 77: debug("slen %u > len %u", slen, len);
1.1 markus 78: memmove(sig + diff, sig, len);
79: memset(sig, 0, diff);
80: } else if (len > slen) {
1.21 deraadt 81: error("ssh_rsa_sign: slen %u slen2 %u", slen, len);
1.1 markus 82: xfree(sig);
83: return -1;
84: }
85: /* encode signature */
86: buffer_init(&b);
87: buffer_put_cstring(&b, "ssh-rsa");
88: buffer_put_string(&b, sig, slen);
89: len = buffer_len(&b);
1.23 markus 90: if (lenp != NULL)
91: *lenp = len;
92: if (sigp != NULL) {
93: *sigp = xmalloc(len);
94: memcpy(*sigp, buffer_ptr(&b), len);
95: }
1.1 markus 96: buffer_free(&b);
97: memset(sig, 's', slen);
98: xfree(sig);
99:
100: return 0;
101: }
102:
103: int
1.31 jakob 104: ssh_rsa_verify(const Key *key, const u_char *signature, u_int signaturelen,
105: const u_char *data, u_int datalen)
1.1 markus 106: {
107: Buffer b;
1.7 markus 108: const EVP_MD *evp_md;
1.1 markus 109: EVP_MD_CTX md;
110: char *ktype;
1.15 markus 111: u_char digest[EVP_MAX_MD_SIZE], *sigblob;
1.19 markus 112: u_int len, dlen, modlen;
1.7 markus 113: int rlen, ret, nid;
1.1 markus 114:
1.40 ! djm 115: if (key == NULL ||
! 116: (key->type != KEY_RSA && key->type != KEY_RSA_CERT) ||
! 117: key->rsa == NULL) {
1.1 markus 118: error("ssh_rsa_verify: no RSA key");
1.4 markus 119: return -1;
120: }
1.17 stevesk 121: if (BN_num_bits(key->rsa->n) < SSH_RSA_MINIMUM_MODULUS_SIZE) {
1.20 stevesk 122: error("ssh_rsa_verify: RSA modulus too small: %d < minimum %d bits",
123: BN_num_bits(key->rsa->n), SSH_RSA_MINIMUM_MODULUS_SIZE);
1.1 markus 124: return -1;
125: }
126: buffer_init(&b);
1.10 stevesk 127: buffer_append(&b, signature, signaturelen);
1.1 markus 128: ktype = buffer_get_string(&b, NULL);
129: if (strcmp("ssh-rsa", ktype) != 0) {
130: error("ssh_rsa_verify: cannot handle type %s", ktype);
131: buffer_free(&b);
132: xfree(ktype);
133: return -1;
134: }
135: xfree(ktype);
1.10 stevesk 136: sigblob = buffer_get_string(&b, &len);
1.1 markus 137: rlen = buffer_len(&b);
138: buffer_free(&b);
1.14 deraadt 139: if (rlen != 0) {
1.12 markus 140: error("ssh_rsa_verify: remaining bytes in signature %d", rlen);
1.7 markus 141: xfree(sigblob);
1.1 markus 142: return -1;
1.19 markus 143: }
144: /* RSA_verify expects a signature of RSA_size */
145: modlen = RSA_size(key->rsa);
146: if (len > modlen) {
1.21 deraadt 147: error("ssh_rsa_verify: len %u > modlen %u", len, modlen);
1.19 markus 148: xfree(sigblob);
149: return -1;
150: } else if (len < modlen) {
1.24 markus 151: u_int diff = modlen - len;
1.21 deraadt 152: debug("ssh_rsa_verify: add padding: modlen %u > len %u",
1.19 markus 153: modlen, len);
1.36 djm 154: sigblob = xrealloc(sigblob, 1, modlen);
1.19 markus 155: memmove(sigblob + diff, sigblob, len);
156: memset(sigblob, 0, diff);
157: len = modlen;
1.1 markus 158: }
1.8 markus 159: nid = (datafellows & SSH_BUG_RSASIGMD5) ? NID_md5 : NID_sha1;
1.7 markus 160: if ((evp_md = EVP_get_digestbynid(nid)) == NULL) {
1.12 markus 161: error("ssh_rsa_verify: EVP_get_digestbynid %d failed", nid);
1.7 markus 162: xfree(sigblob);
163: return -1;
164: }
1.1 markus 165: EVP_DigestInit(&md, evp_md);
166: EVP_DigestUpdate(&md, data, datalen);
1.15 markus 167: EVP_DigestFinal(&md, digest, &dlen);
1.1 markus 168:
1.25 markus 169: ret = openssh_RSA_verify(nid, digest, dlen, sigblob, len, key->rsa);
1.15 markus 170: memset(digest, 'd', sizeof(digest));
1.1 markus 171: memset(sigblob, 's', len);
172: xfree(sigblob);
173: debug("ssh_rsa_verify: signature %scorrect", (ret==0) ? "in" : "");
1.25 markus 174: return ret;
175: }
176:
177: /*
178: * See:
179: * http://www.rsasecurity.com/rsalabs/pkcs/pkcs-1/
180: * ftp://ftp.rsasecurity.com/pub/pkcs/pkcs-1/pkcs-1v2-1.asn
181: */
182: /*
183: * id-sha1 OBJECT IDENTIFIER ::= { iso(1) identified-organization(3)
184: * oiw(14) secsig(3) algorithms(2) 26 }
185: */
186: static const u_char id_sha1[] = {
187: 0x30, 0x21, /* type Sequence, length 0x21 (33) */
188: 0x30, 0x09, /* type Sequence, length 0x09 */
189: 0x06, 0x05, /* type OID, length 0x05 */
190: 0x2b, 0x0e, 0x03, 0x02, 0x1a, /* id-sha1 OID */
191: 0x05, 0x00, /* NULL */
192: 0x04, 0x14 /* Octet string, length 0x14 (20), followed by sha1 hash */
193: };
194: /*
195: * id-md5 OBJECT IDENTIFIER ::= { iso(1) member-body(2) us(840)
196: * rsadsi(113549) digestAlgorithm(2) 5 }
197: */
198: static const u_char id_md5[] = {
199: 0x30, 0x20, /* type Sequence, length 0x20 (32) */
200: 0x30, 0x0c, /* type Sequence, length 0x09 */
201: 0x06, 0x08, /* type OID, length 0x05 */
202: 0x2a, 0x86, 0x48, 0x86, 0xF7, 0x0D, 0x02, 0x05, /* id-md5 */
203: 0x05, 0x00, /* NULL */
204: 0x04, 0x10 /* Octet string, length 0x10 (16), followed by md5 hash */
205: };
206:
207: static int
208: openssh_RSA_verify(int type, u_char *hash, u_int hashlen,
209: u_char *sigbuf, u_int siglen, RSA *rsa)
210: {
1.26 stevesk 211: u_int ret, rsasize, oidlen = 0, hlen = 0;
212: int len;
1.25 markus 213: const u_char *oid = NULL;
214: u_char *decrypted = NULL;
215:
216: ret = 0;
217: switch (type) {
218: case NID_sha1:
219: oid = id_sha1;
220: oidlen = sizeof(id_sha1);
221: hlen = 20;
222: break;
223: case NID_md5:
224: oid = id_md5;
225: oidlen = sizeof(id_md5);
226: hlen = 16;
227: break;
228: default:
229: goto done;
230: }
231: if (hashlen != hlen) {
232: error("bad hashlen");
233: goto done;
234: }
235: rsasize = RSA_size(rsa);
236: if (siglen == 0 || siglen > rsasize) {
237: error("bad siglen");
238: goto done;
239: }
240: decrypted = xmalloc(rsasize);
241: if ((len = RSA_public_decrypt(siglen, sigbuf, decrypted, rsa,
242: RSA_PKCS1_PADDING)) < 0) {
243: error("RSA_public_decrypt failed: %s",
244: ERR_error_string(ERR_get_error(), NULL));
245: goto done;
246: }
1.32 djm 247: if (len < 0 || (u_int)len != hlen + oidlen) {
1.30 markus 248: error("bad decrypted len: %d != %d + %d", len, hlen, oidlen);
1.25 markus 249: goto done;
250: }
251: if (memcmp(decrypted, oid, oidlen) != 0) {
252: error("oid mismatch");
253: goto done;
254: }
255: if (memcmp(decrypted + oidlen, hash, hlen) != 0) {
256: error("hash mismatch");
257: goto done;
258: }
259: ret = 1;
260: done:
261: if (decrypted)
262: xfree(decrypted);
1.1 markus 263: return ret;
264: }
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