Annotation of src/usr.bin/ssh/ssh-rsa.c, Revision 1.34
1.1 markus 1: /*
1.30 markus 2: * Copyright (c) 2000, 2003 Markus Friedl <markus@openbsd.org>
1.1 markus 3: *
1.30 markus 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: *
1.30 markus 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"
1.5 markus 17:
18: #include <openssl/evp.h>
19: #include <openssl/err.h>
1.1 markus 20:
21: #include "xmalloc.h"
1.5 markus 22: #include "log.h"
1.1 markus 23: #include "buffer.h"
24: #include "bufaux.h"
25: #include "key.h"
1.8 markus 26: #include "compat.h"
1.17 stevesk 27: #include "ssh.h"
1.1 markus 28:
1.27 deraadt 29: static int openssh_RSA_verify(int, u_char *, u_int, u_char *, u_int, RSA *);
1.25 markus 30:
1.1 markus 31: /* RSASSA-PKCS1-v1_5 (PKCS #1 v2.0 signature) with SHA1 */
32: int
1.31 jakob 33: ssh_rsa_sign(const Key *key, u_char **sigp, u_int *lenp,
34: const u_char *data, u_int datalen)
1.1 markus 35: {
1.7 markus 36: const EVP_MD *evp_md;
1.1 markus 37: EVP_MD_CTX md;
1.23 markus 38: u_char digest[EVP_MAX_MD_SIZE], *sig;
1.2 markus 39: u_int slen, dlen, len;
1.7 markus 40: int ok, nid;
1.1 markus 41: Buffer b;
42:
43: if (key == NULL || key->type != KEY_RSA || key->rsa == NULL) {
44: error("ssh_rsa_sign: no RSA key");
45: return -1;
46: }
1.8 markus 47: nid = (datafellows & SSH_BUG_RSASIGMD5) ? NID_md5 : NID_sha1;
1.7 markus 48: if ((evp_md = EVP_get_digestbynid(nid)) == NULL) {
49: error("ssh_rsa_sign: EVP_get_digestbynid %d failed", nid);
50: return -1;
51: }
1.1 markus 52: EVP_DigestInit(&md, evp_md);
53: EVP_DigestUpdate(&md, data, datalen);
1.15 markus 54: EVP_DigestFinal(&md, digest, &dlen);
1.1 markus 55:
1.7 markus 56: slen = RSA_size(key->rsa);
57: sig = xmalloc(slen);
58:
59: ok = RSA_sign(nid, digest, dlen, sig, &len, key->rsa);
1.15 markus 60: memset(digest, 'd', sizeof(digest));
1.1 markus 61:
62: if (ok != 1) {
63: int ecode = ERR_get_error();
1.21 deraadt 64: error("ssh_rsa_sign: RSA_sign failed: %s",
65: ERR_error_string(ecode, NULL));
1.1 markus 66: xfree(sig);
67: return -1;
68: }
69: if (len < slen) {
1.24 markus 70: u_int diff = slen - len;
1.21 deraadt 71: debug("slen %u > len %u", slen, len);
1.1 markus 72: memmove(sig + diff, sig, len);
73: memset(sig, 0, diff);
74: } else if (len > slen) {
1.21 deraadt 75: error("ssh_rsa_sign: slen %u slen2 %u", slen, len);
1.1 markus 76: xfree(sig);
77: return -1;
78: }
79: /* encode signature */
80: buffer_init(&b);
81: buffer_put_cstring(&b, "ssh-rsa");
82: buffer_put_string(&b, sig, slen);
83: len = buffer_len(&b);
1.23 markus 84: if (lenp != NULL)
85: *lenp = len;
86: if (sigp != NULL) {
87: *sigp = xmalloc(len);
88: memcpy(*sigp, buffer_ptr(&b), len);
89: }
1.1 markus 90: buffer_free(&b);
91: memset(sig, 's', slen);
92: xfree(sig);
93:
94: return 0;
95: }
96:
97: int
1.31 jakob 98: ssh_rsa_verify(const Key *key, const u_char *signature, u_int signaturelen,
99: const u_char *data, u_int datalen)
1.1 markus 100: {
101: Buffer b;
1.7 markus 102: const EVP_MD *evp_md;
1.1 markus 103: EVP_MD_CTX md;
104: char *ktype;
1.15 markus 105: u_char digest[EVP_MAX_MD_SIZE], *sigblob;
1.19 markus 106: u_int len, dlen, modlen;
1.7 markus 107: int rlen, ret, nid;
1.1 markus 108:
109: if (key == NULL || key->type != KEY_RSA || key->rsa == NULL) {
110: error("ssh_rsa_verify: no RSA key");
1.4 markus 111: return -1;
112: }
1.17 stevesk 113: if (BN_num_bits(key->rsa->n) < SSH_RSA_MINIMUM_MODULUS_SIZE) {
1.20 stevesk 114: error("ssh_rsa_verify: RSA modulus too small: %d < minimum %d bits",
115: BN_num_bits(key->rsa->n), SSH_RSA_MINIMUM_MODULUS_SIZE);
1.1 markus 116: return -1;
117: }
118: buffer_init(&b);
1.10 stevesk 119: buffer_append(&b, signature, signaturelen);
1.1 markus 120: ktype = buffer_get_string(&b, NULL);
121: if (strcmp("ssh-rsa", ktype) != 0) {
122: error("ssh_rsa_verify: cannot handle type %s", ktype);
123: buffer_free(&b);
124: xfree(ktype);
125: return -1;
126: }
127: xfree(ktype);
1.10 stevesk 128: sigblob = buffer_get_string(&b, &len);
1.1 markus 129: rlen = buffer_len(&b);
130: buffer_free(&b);
1.14 deraadt 131: if (rlen != 0) {
1.12 markus 132: error("ssh_rsa_verify: remaining bytes in signature %d", rlen);
1.7 markus 133: xfree(sigblob);
1.1 markus 134: return -1;
1.19 markus 135: }
136: /* RSA_verify expects a signature of RSA_size */
137: modlen = RSA_size(key->rsa);
138: if (len > modlen) {
1.21 deraadt 139: error("ssh_rsa_verify: len %u > modlen %u", len, modlen);
1.19 markus 140: xfree(sigblob);
141: return -1;
142: } else if (len < modlen) {
1.24 markus 143: u_int diff = modlen - len;
1.21 deraadt 144: debug("ssh_rsa_verify: add padding: modlen %u > len %u",
1.19 markus 145: modlen, len);
146: sigblob = xrealloc(sigblob, modlen);
147: memmove(sigblob + diff, sigblob, len);
148: memset(sigblob, 0, diff);
149: len = modlen;
1.1 markus 150: }
1.8 markus 151: nid = (datafellows & SSH_BUG_RSASIGMD5) ? NID_md5 : NID_sha1;
1.7 markus 152: if ((evp_md = EVP_get_digestbynid(nid)) == NULL) {
1.12 markus 153: error("ssh_rsa_verify: EVP_get_digestbynid %d failed", nid);
1.7 markus 154: xfree(sigblob);
155: return -1;
156: }
1.1 markus 157: EVP_DigestInit(&md, evp_md);
158: EVP_DigestUpdate(&md, data, datalen);
1.15 markus 159: EVP_DigestFinal(&md, digest, &dlen);
1.1 markus 160:
1.25 markus 161: ret = openssh_RSA_verify(nid, digest, dlen, sigblob, len, key->rsa);
1.15 markus 162: memset(digest, 'd', sizeof(digest));
1.1 markus 163: memset(sigblob, 's', len);
164: xfree(sigblob);
165: debug("ssh_rsa_verify: signature %scorrect", (ret==0) ? "in" : "");
1.25 markus 166: return ret;
167: }
168:
169: /*
170: * See:
171: * http://www.rsasecurity.com/rsalabs/pkcs/pkcs-1/
172: * ftp://ftp.rsasecurity.com/pub/pkcs/pkcs-1/pkcs-1v2-1.asn
173: */
174: /*
175: * id-sha1 OBJECT IDENTIFIER ::= { iso(1) identified-organization(3)
176: * oiw(14) secsig(3) algorithms(2) 26 }
177: */
178: static const u_char id_sha1[] = {
179: 0x30, 0x21, /* type Sequence, length 0x21 (33) */
180: 0x30, 0x09, /* type Sequence, length 0x09 */
181: 0x06, 0x05, /* type OID, length 0x05 */
182: 0x2b, 0x0e, 0x03, 0x02, 0x1a, /* id-sha1 OID */
183: 0x05, 0x00, /* NULL */
184: 0x04, 0x14 /* Octet string, length 0x14 (20), followed by sha1 hash */
185: };
186: /*
187: * id-md5 OBJECT IDENTIFIER ::= { iso(1) member-body(2) us(840)
188: * rsadsi(113549) digestAlgorithm(2) 5 }
189: */
190: static const u_char id_md5[] = {
191: 0x30, 0x20, /* type Sequence, length 0x20 (32) */
192: 0x30, 0x0c, /* type Sequence, length 0x09 */
193: 0x06, 0x08, /* type OID, length 0x05 */
194: 0x2a, 0x86, 0x48, 0x86, 0xF7, 0x0D, 0x02, 0x05, /* id-md5 */
195: 0x05, 0x00, /* NULL */
196: 0x04, 0x10 /* Octet string, length 0x10 (16), followed by md5 hash */
197: };
198:
199: static int
200: openssh_RSA_verify(int type, u_char *hash, u_int hashlen,
201: u_char *sigbuf, u_int siglen, RSA *rsa)
202: {
1.26 stevesk 203: u_int ret, rsasize, oidlen = 0, hlen = 0;
204: int len;
1.25 markus 205: const u_char *oid = NULL;
206: u_char *decrypted = NULL;
207:
208: ret = 0;
209: switch (type) {
210: case NID_sha1:
211: oid = id_sha1;
212: oidlen = sizeof(id_sha1);
213: hlen = 20;
214: break;
215: case NID_md5:
216: oid = id_md5;
217: oidlen = sizeof(id_md5);
218: hlen = 16;
219: break;
220: default:
221: goto done;
222: }
223: if (hashlen != hlen) {
224: error("bad hashlen");
225: goto done;
226: }
227: rsasize = RSA_size(rsa);
228: if (siglen == 0 || siglen > rsasize) {
229: error("bad siglen");
230: goto done;
231: }
232: decrypted = xmalloc(rsasize);
233: if ((len = RSA_public_decrypt(siglen, sigbuf, decrypted, rsa,
234: RSA_PKCS1_PADDING)) < 0) {
235: error("RSA_public_decrypt failed: %s",
236: ERR_error_string(ERR_get_error(), NULL));
237: goto done;
238: }
1.32 djm 239: if (len < 0 || (u_int)len != hlen + oidlen) {
1.30 markus 240: error("bad decrypted len: %d != %d + %d", len, hlen, oidlen);
1.25 markus 241: goto done;
242: }
243: if (memcmp(decrypted, oid, oidlen) != 0) {
244: error("oid mismatch");
245: goto done;
246: }
247: if (memcmp(decrypted + oidlen, hash, hlen) != 0) {
248: error("hash mismatch");
249: goto done;
250: }
251: ret = 1;
252: done:
253: if (decrypted)
254: xfree(decrypted);
1.1 markus 255: return ret;
256: }