Annotation of src/usr.bin/ssh/ssh-rsa.c, Revision 1.61
1.61 ! djm 1: /* $OpenBSD: ssh-rsa.c,v 1.60 2016/09/12 23:39:34 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:
1.52 djm 25: #include "sshbuf.h"
1.8 markus 26: #include "compat.h"
1.52 djm 27: #include "ssherr.h"
28: #define SSHKEY_INTERNAL
29: #include "sshkey.h"
1.50 djm 30: #include "digest.h"
1.1 markus 31:
1.52 djm 32: static int openssh_RSA_verify(int, u_char *, size_t, u_char *, size_t, RSA *);
1.25 markus 33:
1.55 markus 34: static const char *
35: rsa_hash_alg_ident(int hash_alg)
36: {
37: switch (hash_alg) {
38: case SSH_DIGEST_SHA1:
39: return "ssh-rsa";
40: case SSH_DIGEST_SHA256:
41: return "rsa-sha2-256";
42: case SSH_DIGEST_SHA512:
43: return "rsa-sha2-512";
44: }
45: return NULL;
46: }
47:
48: static int
49: rsa_hash_alg_from_ident(const char *ident)
50: {
1.60 djm 51: if (strcmp(ident, "ssh-rsa") == 0 ||
52: strcmp(ident, "ssh-rsa-cert-v01@openssh.com") == 0)
1.55 markus 53: return SSH_DIGEST_SHA1;
54: if (strcmp(ident, "rsa-sha2-256") == 0)
55: return SSH_DIGEST_SHA256;
56: if (strcmp(ident, "rsa-sha2-512") == 0)
57: return SSH_DIGEST_SHA512;
58: return -1;
59: }
60:
61: static int
62: rsa_hash_alg_nid(int type)
63: {
64: switch (type) {
65: case SSH_DIGEST_SHA1:
66: return NID_sha1;
67: case SSH_DIGEST_SHA256:
68: return NID_sha256;
69: case SSH_DIGEST_SHA512:
70: return NID_sha512;
71: default:
72: return -1;
73: }
74: }
75:
1.1 markus 76: /* RSASSA-PKCS1-v1_5 (PKCS #1 v2.0 signature) with SHA1 */
77: int
1.52 djm 78: ssh_rsa_sign(const struct sshkey *key, u_char **sigp, size_t *lenp,
1.55 markus 79: const u_char *data, size_t datalen, const char *alg_ident)
1.1 markus 80: {
1.52 djm 81: u_char digest[SSH_DIGEST_MAX_LENGTH], *sig = NULL;
82: size_t slen;
83: u_int dlen, len;
1.55 markus 84: int nid, hash_alg, ret = SSH_ERR_INTERNAL_ERROR;
1.52 djm 85: struct sshbuf *b = NULL;
86:
87: if (lenp != NULL)
88: *lenp = 0;
89: if (sigp != NULL)
90: *sigp = NULL;
91:
1.60 djm 92: if (alg_ident == NULL || strlen(alg_ident) == 0)
1.56 markus 93: hash_alg = SSH_DIGEST_SHA1;
94: else
95: hash_alg = rsa_hash_alg_from_ident(alg_ident);
1.55 markus 96: if (key == NULL || key->rsa == NULL || hash_alg == -1 ||
1.61 ! djm 97: sshkey_type_plain(key->type) != KEY_RSA)
1.52 djm 98: return SSH_ERR_INVALID_ARGUMENT;
1.61 ! djm 99: if (BN_num_bits(key->rsa->n) < SSH_RSA_MINIMUM_MODULUS_SIZE)
! 100: return SSH_ERR_KEY_LENGTH;
1.52 djm 101: slen = RSA_size(key->rsa);
102: if (slen <= 0 || slen > SSHBUF_MAX_BIGNUM)
103: return SSH_ERR_INVALID_ARGUMENT;
1.47 djm 104:
1.50 djm 105: /* hash the data */
1.55 markus 106: nid = rsa_hash_alg_nid(hash_alg);
1.52 djm 107: if ((dlen = ssh_digest_bytes(hash_alg)) == 0)
108: return SSH_ERR_INTERNAL_ERROR;
109: if ((ret = ssh_digest_memory(hash_alg, data, datalen,
110: digest, sizeof(digest))) != 0)
111: goto out;
112:
113: if ((sig = malloc(slen)) == NULL) {
114: ret = SSH_ERR_ALLOC_FAIL;
115: goto out;
1.50 djm 116: }
1.1 markus 117:
1.52 djm 118: if (RSA_sign(nid, digest, dlen, sig, &len, key->rsa) != 1) {
119: ret = SSH_ERR_LIBCRYPTO_ERROR;
120: goto out;
1.1 markus 121: }
122: if (len < slen) {
1.52 djm 123: size_t diff = slen - len;
1.1 markus 124: memmove(sig + diff, sig, len);
1.51 djm 125: explicit_bzero(sig, diff);
1.1 markus 126: } else if (len > slen) {
1.52 djm 127: ret = SSH_ERR_INTERNAL_ERROR;
128: goto out;
1.1 markus 129: }
130: /* encode signature */
1.52 djm 131: if ((b = sshbuf_new()) == NULL) {
132: ret = SSH_ERR_ALLOC_FAIL;
133: goto out;
134: }
1.55 markus 135: if ((ret = sshbuf_put_cstring(b, rsa_hash_alg_ident(hash_alg))) != 0 ||
1.52 djm 136: (ret = sshbuf_put_string(b, sig, slen)) != 0)
137: goto out;
138: len = sshbuf_len(b);
139: if (sigp != NULL) {
140: if ((*sigp = malloc(len)) == NULL) {
141: ret = SSH_ERR_ALLOC_FAIL;
142: goto out;
143: }
144: memcpy(*sigp, sshbuf_ptr(b), len);
145: }
1.23 markus 146: if (lenp != NULL)
147: *lenp = len;
1.52 djm 148: ret = 0;
149: out:
150: explicit_bzero(digest, sizeof(digest));
151: if (sig != NULL) {
152: explicit_bzero(sig, slen);
153: free(sig);
1.23 markus 154: }
1.58 mmcc 155: sshbuf_free(b);
1.53 djm 156: return ret;
1.1 markus 157: }
158:
159: int
1.52 djm 160: ssh_rsa_verify(const struct sshkey *key,
1.55 markus 161: const u_char *sig, size_t siglen, const u_char *data, size_t datalen)
1.1 markus 162: {
1.52 djm 163: char *ktype = NULL;
164: int hash_alg, ret = SSH_ERR_INTERNAL_ERROR;
165: size_t len, diff, modlen, dlen;
166: struct sshbuf *b = NULL;
167: u_char digest[SSH_DIGEST_MAX_LENGTH], *osigblob, *sigblob = NULL;
168:
169: if (key == NULL || key->rsa == NULL ||
170: sshkey_type_plain(key->type) != KEY_RSA ||
1.59 djm 171: sig == NULL || siglen == 0)
1.52 djm 172: return SSH_ERR_INVALID_ARGUMENT;
1.61 ! djm 173: if (BN_num_bits(key->rsa->n) < SSH_RSA_MINIMUM_MODULUS_SIZE)
! 174: return SSH_ERR_KEY_LENGTH;
1.52 djm 175:
1.55 markus 176: if ((b = sshbuf_from(sig, siglen)) == NULL)
1.52 djm 177: return SSH_ERR_ALLOC_FAIL;
178: if (sshbuf_get_cstring(b, &ktype, NULL) != 0) {
179: ret = SSH_ERR_INVALID_FORMAT;
180: goto out;
181: }
1.55 markus 182: if ((hash_alg = rsa_hash_alg_from_ident(ktype)) == -1) {
1.52 djm 183: ret = SSH_ERR_KEY_TYPE_MISMATCH;
184: goto out;
1.1 markus 185: }
1.52 djm 186: if (sshbuf_get_string(b, &sigblob, &len) != 0) {
187: ret = SSH_ERR_INVALID_FORMAT;
188: goto out;
189: }
190: if (sshbuf_len(b) != 0) {
191: ret = SSH_ERR_UNEXPECTED_TRAILING_DATA;
192: goto out;
1.19 markus 193: }
194: /* RSA_verify expects a signature of RSA_size */
195: modlen = RSA_size(key->rsa);
196: if (len > modlen) {
1.52 djm 197: ret = SSH_ERR_KEY_BITS_MISMATCH;
198: goto out;
1.19 markus 199: } else if (len < modlen) {
1.52 djm 200: diff = modlen - len;
201: osigblob = sigblob;
202: if ((sigblob = realloc(sigblob, modlen)) == NULL) {
203: sigblob = osigblob; /* put it back for clear/free */
204: ret = SSH_ERR_ALLOC_FAIL;
205: goto out;
206: }
1.19 markus 207: memmove(sigblob + diff, sigblob, len);
1.51 djm 208: explicit_bzero(sigblob, diff);
1.19 markus 209: len = modlen;
1.1 markus 210: }
1.50 djm 211: if ((dlen = ssh_digest_bytes(hash_alg)) == 0) {
1.52 djm 212: ret = SSH_ERR_INTERNAL_ERROR;
213: goto out;
1.7 markus 214: }
1.52 djm 215: if ((ret = ssh_digest_memory(hash_alg, data, datalen,
216: digest, sizeof(digest))) != 0)
217: goto out;
1.1 markus 218:
1.50 djm 219: ret = openssh_RSA_verify(hash_alg, digest, dlen, sigblob, len,
220: key->rsa);
1.52 djm 221: out:
222: if (sigblob != NULL) {
223: explicit_bzero(sigblob, len);
224: free(sigblob);
225: }
1.57 mmcc 226: free(ktype);
1.58 mmcc 227: sshbuf_free(b);
1.51 djm 228: explicit_bzero(digest, sizeof(digest));
1.25 markus 229: return ret;
230: }
231:
232: /*
233: * See:
234: * http://www.rsasecurity.com/rsalabs/pkcs/pkcs-1/
235: * ftp://ftp.rsasecurity.com/pub/pkcs/pkcs-1/pkcs-1v2-1.asn
236: */
1.55 markus 237:
1.25 markus 238: /*
239: * id-sha1 OBJECT IDENTIFIER ::= { iso(1) identified-organization(3)
240: * oiw(14) secsig(3) algorithms(2) 26 }
241: */
242: static const u_char id_sha1[] = {
243: 0x30, 0x21, /* type Sequence, length 0x21 (33) */
244: 0x30, 0x09, /* type Sequence, length 0x09 */
245: 0x06, 0x05, /* type OID, length 0x05 */
246: 0x2b, 0x0e, 0x03, 0x02, 0x1a, /* id-sha1 OID */
247: 0x05, 0x00, /* NULL */
248: 0x04, 0x14 /* Octet string, length 0x14 (20), followed by sha1 hash */
249: };
250:
1.55 markus 251: /*
252: * See http://csrc.nist.gov/groups/ST/crypto_apps_infra/csor/algorithms.html
253: * id-sha256 OBJECT IDENTIFIER ::= { joint-iso-itu-t(2) country(16) us(840)
254: * organization(1) gov(101) csor(3) nistAlgorithm(4) hashAlgs(2)
255: * id-sha256(1) }
256: */
257: static const u_char id_sha256[] = {
258: 0x30, 0x31, /* type Sequence, length 0x31 (49) */
259: 0x30, 0x0d, /* type Sequence, length 0x0d (13) */
260: 0x06, 0x09, /* type OID, length 0x09 */
261: 0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x01, /* id-sha256 */
262: 0x05, 0x00, /* NULL */
263: 0x04, 0x20 /* Octet string, length 0x20 (32), followed by sha256 hash */
264: };
265:
266: /*
267: * See http://csrc.nist.gov/groups/ST/crypto_apps_infra/csor/algorithms.html
268: * id-sha512 OBJECT IDENTIFIER ::= { joint-iso-itu-t(2) country(16) us(840)
269: * organization(1) gov(101) csor(3) nistAlgorithm(4) hashAlgs(2)
270: * id-sha256(3) }
271: */
272: static const u_char id_sha512[] = {
273: 0x30, 0x51, /* type Sequence, length 0x51 (81) */
274: 0x30, 0x0d, /* type Sequence, length 0x0d (13) */
275: 0x06, 0x09, /* type OID, length 0x09 */
276: 0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x03, /* id-sha512 */
277: 0x05, 0x00, /* NULL */
278: 0x04, 0x40 /* Octet string, length 0x40 (64), followed by sha512 hash */
279: };
280:
281: static int
282: rsa_hash_alg_oid(int hash_alg, const u_char **oidp, size_t *oidlenp)
283: {
284: switch (hash_alg) {
285: case SSH_DIGEST_SHA1:
286: *oidp = id_sha1;
287: *oidlenp = sizeof(id_sha1);
288: break;
289: case SSH_DIGEST_SHA256:
290: *oidp = id_sha256;
291: *oidlenp = sizeof(id_sha256);
292: break;
293: case SSH_DIGEST_SHA512:
294: *oidp = id_sha512;
295: *oidlenp = sizeof(id_sha512);
296: break;
297: default:
298: return SSH_ERR_INVALID_ARGUMENT;
299: }
300: return 0;
301: }
302:
1.25 markus 303: static int
1.52 djm 304: openssh_RSA_verify(int hash_alg, u_char *hash, size_t hashlen,
305: u_char *sigbuf, size_t siglen, RSA *rsa)
1.25 markus 306: {
1.54 djm 307: size_t rsasize = 0, oidlen = 0, hlen = 0;
308: int ret, len, oidmatch, hashmatch;
1.25 markus 309: const u_char *oid = NULL;
310: u_char *decrypted = NULL;
311:
1.55 markus 312: if ((ret = rsa_hash_alg_oid(hash_alg, &oid, &oidlen)) != 0)
313: return ret;
1.52 djm 314: ret = SSH_ERR_INTERNAL_ERROR;
1.55 markus 315: hlen = ssh_digest_bytes(hash_alg);
1.25 markus 316: if (hashlen != hlen) {
1.52 djm 317: ret = SSH_ERR_INVALID_ARGUMENT;
1.25 markus 318: goto done;
319: }
320: rsasize = RSA_size(rsa);
1.52 djm 321: if (rsasize <= 0 || rsasize > SSHBUF_MAX_BIGNUM ||
322: siglen == 0 || siglen > rsasize) {
323: ret = SSH_ERR_INVALID_ARGUMENT;
324: goto done;
325: }
326: if ((decrypted = malloc(rsasize)) == NULL) {
327: ret = SSH_ERR_ALLOC_FAIL;
1.25 markus 328: goto done;
329: }
330: if ((len = RSA_public_decrypt(siglen, sigbuf, decrypted, rsa,
331: RSA_PKCS1_PADDING)) < 0) {
1.52 djm 332: ret = SSH_ERR_LIBCRYPTO_ERROR;
1.25 markus 333: goto done;
334: }
1.52 djm 335: if (len < 0 || (size_t)len != hlen + oidlen) {
336: ret = SSH_ERR_INVALID_FORMAT;
1.25 markus 337: goto done;
338: }
1.44 djm 339: oidmatch = timingsafe_bcmp(decrypted, oid, oidlen) == 0;
340: hashmatch = timingsafe_bcmp(decrypted + oidlen, hash, hlen) == 0;
1.52 djm 341: if (!oidmatch || !hashmatch) {
342: ret = SSH_ERR_SIGNATURE_INVALID;
1.25 markus 343: goto done;
344: }
1.52 djm 345: ret = 0;
346: done:
347: if (decrypted) {
348: explicit_bzero(decrypted, rsasize);
349: free(decrypted);
1.25 markus 350: }
1.1 markus 351: return ret;
352: }
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