Annotation of src/usr.bin/ssh/ssh-rsa.c, Revision 1.28.2.1
1.1 markus 1: /*
1.28.2.1! brad 2: * Copyright (c) 2000, 2003 Markus Friedl <markus@openbsd.org>
1.1 markus 3: *
1.28.2.1! brad 4: * Permission to use, copy, modify, and distribute this software for any
! 5: * purpose with or without fee is hereby granted, provided that the above
! 6: * copyright notice and this permission notice appear in all copies.
1.1 markus 7: *
1.28.2.1! brad 8: * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
! 9: * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
! 10: * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
! 11: * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
! 12: * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
! 13: * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
! 14: * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
1.1 markus 15: */
16: #include "includes.h"
1.28.2.1! brad 17: RCSID("$OpenBSD: ssh-rsa.c,v 1.30 2003/06/18 11:28:11 markus Exp $");
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
1.21 deraadt 34: ssh_rsa_sign(Key *key, u_char **sigp, u_int *lenp,
1.16 markus 35: 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();
1.21 deraadt 65: error("ssh_rsa_sign: RSA_sign failed: %s",
66: ERR_error_string(ecode, NULL));
1.1 markus 67: xfree(sig);
68: return -1;
69: }
70: if (len < slen) {
1.24 markus 71: u_int diff = slen - len;
1.21 deraadt 72: debug("slen %u > len %u", slen, len);
1.1 markus 73: memmove(sig + diff, sig, len);
74: memset(sig, 0, diff);
75: } else if (len > slen) {
1.21 deraadt 76: error("ssh_rsa_sign: slen %u slen2 %u", slen, len);
1.1 markus 77: xfree(sig);
78: return -1;
79: }
80: /* encode signature */
81: buffer_init(&b);
82: buffer_put_cstring(&b, "ssh-rsa");
83: buffer_put_string(&b, sig, slen);
84: len = buffer_len(&b);
1.23 markus 85: if (lenp != NULL)
86: *lenp = len;
87: if (sigp != NULL) {
88: *sigp = xmalloc(len);
89: memcpy(*sigp, buffer_ptr(&b), len);
90: }
1.1 markus 91: buffer_free(&b);
92: memset(sig, 's', slen);
93: xfree(sig);
94:
95: return 0;
96: }
97:
98: int
1.21 deraadt 99: ssh_rsa_verify(Key *key, u_char *signature, u_int signaturelen,
1.16 markus 100: u_char *data, u_int datalen)
1.1 markus 101: {
102: Buffer b;
1.7 markus 103: const EVP_MD *evp_md;
1.1 markus 104: EVP_MD_CTX md;
105: char *ktype;
1.15 markus 106: u_char digest[EVP_MAX_MD_SIZE], *sigblob;
1.19 markus 107: u_int len, dlen, modlen;
1.7 markus 108: int rlen, ret, nid;
1.1 markus 109:
110: if (key == NULL || key->type != KEY_RSA || key->rsa == NULL) {
111: error("ssh_rsa_verify: no RSA key");
1.4 markus 112: return -1;
113: }
1.17 stevesk 114: if (BN_num_bits(key->rsa->n) < SSH_RSA_MINIMUM_MODULUS_SIZE) {
1.20 stevesk 115: error("ssh_rsa_verify: RSA modulus too small: %d < minimum %d bits",
116: BN_num_bits(key->rsa->n), SSH_RSA_MINIMUM_MODULUS_SIZE);
1.1 markus 117: return -1;
118: }
119: buffer_init(&b);
1.10 stevesk 120: buffer_append(&b, signature, signaturelen);
1.1 markus 121: ktype = buffer_get_string(&b, NULL);
122: if (strcmp("ssh-rsa", ktype) != 0) {
123: error("ssh_rsa_verify: cannot handle type %s", ktype);
124: buffer_free(&b);
125: xfree(ktype);
126: return -1;
127: }
128: xfree(ktype);
1.10 stevesk 129: sigblob = buffer_get_string(&b, &len);
1.1 markus 130: rlen = buffer_len(&b);
131: buffer_free(&b);
1.14 deraadt 132: if (rlen != 0) {
1.12 markus 133: error("ssh_rsa_verify: remaining bytes in signature %d", rlen);
1.7 markus 134: xfree(sigblob);
1.1 markus 135: return -1;
1.19 markus 136: }
137: /* RSA_verify expects a signature of RSA_size */
138: modlen = RSA_size(key->rsa);
139: if (len > modlen) {
1.21 deraadt 140: error("ssh_rsa_verify: len %u > modlen %u", len, modlen);
1.19 markus 141: xfree(sigblob);
142: return -1;
143: } else if (len < modlen) {
1.24 markus 144: u_int diff = modlen - len;
1.21 deraadt 145: debug("ssh_rsa_verify: add padding: modlen %u > len %u",
1.19 markus 146: modlen, len);
147: sigblob = xrealloc(sigblob, modlen);
148: memmove(sigblob + diff, sigblob, len);
149: memset(sigblob, 0, diff);
150: len = modlen;
1.1 markus 151: }
1.8 markus 152: nid = (datafellows & SSH_BUG_RSASIGMD5) ? NID_md5 : NID_sha1;
1.7 markus 153: if ((evp_md = EVP_get_digestbynid(nid)) == NULL) {
1.12 markus 154: error("ssh_rsa_verify: EVP_get_digestbynid %d failed", nid);
1.7 markus 155: xfree(sigblob);
156: return -1;
157: }
1.1 markus 158: EVP_DigestInit(&md, evp_md);
159: EVP_DigestUpdate(&md, data, datalen);
1.15 markus 160: EVP_DigestFinal(&md, digest, &dlen);
1.1 markus 161:
1.25 markus 162: ret = openssh_RSA_verify(nid, digest, dlen, sigblob, len, key->rsa);
1.15 markus 163: memset(digest, 'd', sizeof(digest));
1.1 markus 164: memset(sigblob, 's', len);
165: xfree(sigblob);
166: debug("ssh_rsa_verify: signature %scorrect", (ret==0) ? "in" : "");
1.25 markus 167: return ret;
168: }
169:
170: /*
171: * See:
172: * http://www.rsasecurity.com/rsalabs/pkcs/pkcs-1/
173: * ftp://ftp.rsasecurity.com/pub/pkcs/pkcs-1/pkcs-1v2-1.asn
174: */
175: /*
176: * id-sha1 OBJECT IDENTIFIER ::= { iso(1) identified-organization(3)
177: * oiw(14) secsig(3) algorithms(2) 26 }
178: */
179: static const u_char id_sha1[] = {
180: 0x30, 0x21, /* type Sequence, length 0x21 (33) */
181: 0x30, 0x09, /* type Sequence, length 0x09 */
182: 0x06, 0x05, /* type OID, length 0x05 */
183: 0x2b, 0x0e, 0x03, 0x02, 0x1a, /* id-sha1 OID */
184: 0x05, 0x00, /* NULL */
185: 0x04, 0x14 /* Octet string, length 0x14 (20), followed by sha1 hash */
186: };
187: /*
188: * id-md5 OBJECT IDENTIFIER ::= { iso(1) member-body(2) us(840)
189: * rsadsi(113549) digestAlgorithm(2) 5 }
190: */
191: static const u_char id_md5[] = {
192: 0x30, 0x20, /* type Sequence, length 0x20 (32) */
193: 0x30, 0x0c, /* type Sequence, length 0x09 */
194: 0x06, 0x08, /* type OID, length 0x05 */
195: 0x2a, 0x86, 0x48, 0x86, 0xF7, 0x0D, 0x02, 0x05, /* id-md5 */
196: 0x05, 0x00, /* NULL */
197: 0x04, 0x10 /* Octet string, length 0x10 (16), followed by md5 hash */
198: };
199:
200: static int
201: openssh_RSA_verify(int type, u_char *hash, u_int hashlen,
202: u_char *sigbuf, u_int siglen, RSA *rsa)
203: {
1.26 stevesk 204: u_int ret, rsasize, oidlen = 0, hlen = 0;
205: int len;
1.25 markus 206: const u_char *oid = NULL;
207: u_char *decrypted = NULL;
208:
209: ret = 0;
210: switch (type) {
211: case NID_sha1:
212: oid = id_sha1;
213: oidlen = sizeof(id_sha1);
214: hlen = 20;
215: break;
216: case NID_md5:
217: oid = id_md5;
218: oidlen = sizeof(id_md5);
219: hlen = 16;
220: break;
221: default:
222: goto done;
223: break;
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: }
241: if (len != hlen + oidlen) {
242: error("bad decrypted len: %d != %d + %d", len, hlen, oidlen);
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: }
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