Annotation of src/usr.bin/ssh/ssh-rsa.c, Revision 1.65
1.65 ! jsing 1: /* $OpenBSD: ssh-rsa.c,v 1.64 2017/12/18 23:14:34 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"
1.64 djm 31: #include "log.h"
1.1 markus 32:
1.52 djm 33: static int openssh_RSA_verify(int, u_char *, size_t, u_char *, size_t, RSA *);
1.25 markus 34:
1.55 markus 35: static const char *
36: rsa_hash_alg_ident(int hash_alg)
37: {
38: switch (hash_alg) {
39: case SSH_DIGEST_SHA1:
40: return "ssh-rsa";
41: case SSH_DIGEST_SHA256:
42: return "rsa-sha2-256";
43: case SSH_DIGEST_SHA512:
44: return "rsa-sha2-512";
45: }
46: return NULL;
47: }
48:
49: static int
50: rsa_hash_alg_from_ident(const char *ident)
51: {
1.60 djm 52: if (strcmp(ident, "ssh-rsa") == 0 ||
53: strcmp(ident, "ssh-rsa-cert-v01@openssh.com") == 0)
1.55 markus 54: return SSH_DIGEST_SHA1;
55: if (strcmp(ident, "rsa-sha2-256") == 0)
56: return SSH_DIGEST_SHA256;
57: if (strcmp(ident, "rsa-sha2-512") == 0)
58: return SSH_DIGEST_SHA512;
59: return -1;
60: }
61:
62: static int
63: rsa_hash_alg_nid(int type)
64: {
65: switch (type) {
66: case SSH_DIGEST_SHA1:
67: return NID_sha1;
68: case SSH_DIGEST_SHA256:
69: return NID_sha256;
70: case SSH_DIGEST_SHA512:
71: return NID_sha512;
72: default:
73: return -1;
74: }
1.62 djm 75: }
76:
77: /* calculate p-1 and q-1 */
78: int
79: ssh_rsa_generate_additional_parameters(struct sshkey *key)
80: {
81: RSA *rsa;
82: BIGNUM *aux = NULL;
83: BN_CTX *ctx = NULL;
84: int r;
85:
86: if (key == NULL || key->rsa == NULL ||
87: sshkey_type_plain(key->type) != KEY_RSA)
88: return SSH_ERR_INVALID_ARGUMENT;
89:
90: if ((ctx = BN_CTX_new()) == NULL)
91: return SSH_ERR_ALLOC_FAIL;
92: if ((aux = BN_new()) == NULL) {
93: r = SSH_ERR_ALLOC_FAIL;
94: goto out;
95: }
96: rsa = key->rsa;
97:
98: if ((BN_sub(aux, rsa->q, BN_value_one()) == 0) ||
99: (BN_mod(rsa->dmq1, rsa->d, aux, ctx) == 0) ||
100: (BN_sub(aux, rsa->p, BN_value_one()) == 0) ||
101: (BN_mod(rsa->dmp1, rsa->d, aux, ctx) == 0)) {
102: r = SSH_ERR_LIBCRYPTO_ERROR;
103: goto out;
104: }
105: r = 0;
106: out:
107: BN_clear_free(aux);
108: BN_CTX_free(ctx);
109: return r;
1.55 markus 110: }
111:
1.1 markus 112: /* RSASSA-PKCS1-v1_5 (PKCS #1 v2.0 signature) with SHA1 */
113: int
1.52 djm 114: ssh_rsa_sign(const struct sshkey *key, u_char **sigp, size_t *lenp,
1.55 markus 115: const u_char *data, size_t datalen, const char *alg_ident)
1.1 markus 116: {
1.52 djm 117: u_char digest[SSH_DIGEST_MAX_LENGTH], *sig = NULL;
1.65 ! jsing 118: size_t slen = 0;
1.52 djm 119: u_int dlen, len;
1.55 markus 120: int nid, hash_alg, ret = SSH_ERR_INTERNAL_ERROR;
1.52 djm 121: struct sshbuf *b = NULL;
122:
123: if (lenp != NULL)
124: *lenp = 0;
125: if (sigp != NULL)
126: *sigp = NULL;
127:
1.60 djm 128: if (alg_ident == NULL || strlen(alg_ident) == 0)
1.56 markus 129: hash_alg = SSH_DIGEST_SHA1;
130: else
131: hash_alg = rsa_hash_alg_from_ident(alg_ident);
1.55 markus 132: if (key == NULL || key->rsa == NULL || hash_alg == -1 ||
1.61 djm 133: sshkey_type_plain(key->type) != KEY_RSA)
1.52 djm 134: return SSH_ERR_INVALID_ARGUMENT;
1.61 djm 135: if (BN_num_bits(key->rsa->n) < SSH_RSA_MINIMUM_MODULUS_SIZE)
136: return SSH_ERR_KEY_LENGTH;
1.52 djm 137: slen = RSA_size(key->rsa);
138: if (slen <= 0 || slen > SSHBUF_MAX_BIGNUM)
139: return SSH_ERR_INVALID_ARGUMENT;
1.47 djm 140:
1.50 djm 141: /* hash the data */
1.55 markus 142: nid = rsa_hash_alg_nid(hash_alg);
1.52 djm 143: if ((dlen = ssh_digest_bytes(hash_alg)) == 0)
144: return SSH_ERR_INTERNAL_ERROR;
145: if ((ret = ssh_digest_memory(hash_alg, data, datalen,
146: digest, sizeof(digest))) != 0)
147: goto out;
148:
149: if ((sig = malloc(slen)) == NULL) {
150: ret = SSH_ERR_ALLOC_FAIL;
151: goto out;
1.50 djm 152: }
1.1 markus 153:
1.52 djm 154: if (RSA_sign(nid, digest, dlen, sig, &len, key->rsa) != 1) {
155: ret = SSH_ERR_LIBCRYPTO_ERROR;
156: goto out;
1.1 markus 157: }
158: if (len < slen) {
1.52 djm 159: size_t diff = slen - len;
1.1 markus 160: memmove(sig + diff, sig, len);
1.51 djm 161: explicit_bzero(sig, diff);
1.1 markus 162: } else if (len > slen) {
1.52 djm 163: ret = SSH_ERR_INTERNAL_ERROR;
164: goto out;
1.1 markus 165: }
166: /* encode signature */
1.52 djm 167: if ((b = sshbuf_new()) == NULL) {
168: ret = SSH_ERR_ALLOC_FAIL;
169: goto out;
170: }
1.55 markus 171: if ((ret = sshbuf_put_cstring(b, rsa_hash_alg_ident(hash_alg))) != 0 ||
1.52 djm 172: (ret = sshbuf_put_string(b, sig, slen)) != 0)
173: goto out;
174: len = sshbuf_len(b);
175: if (sigp != NULL) {
176: if ((*sigp = malloc(len)) == NULL) {
177: ret = SSH_ERR_ALLOC_FAIL;
178: goto out;
179: }
180: memcpy(*sigp, sshbuf_ptr(b), len);
181: }
1.23 markus 182: if (lenp != NULL)
183: *lenp = len;
1.52 djm 184: ret = 0;
185: out:
186: explicit_bzero(digest, sizeof(digest));
1.65 ! jsing 187: freezero(sig, slen);
1.58 mmcc 188: sshbuf_free(b);
1.53 djm 189: return ret;
1.1 markus 190: }
191:
192: int
1.52 djm 193: ssh_rsa_verify(const struct sshkey *key,
1.63 djm 194: const u_char *sig, size_t siglen, const u_char *data, size_t datalen,
195: const char *alg)
1.1 markus 196: {
1.63 djm 197: char *sigtype = NULL;
1.52 djm 198: int hash_alg, ret = SSH_ERR_INTERNAL_ERROR;
1.65 ! jsing 199: size_t len = 0, diff, modlen, dlen;
1.52 djm 200: struct sshbuf *b = NULL;
201: u_char digest[SSH_DIGEST_MAX_LENGTH], *osigblob, *sigblob = NULL;
202:
203: if (key == NULL || key->rsa == NULL ||
204: sshkey_type_plain(key->type) != KEY_RSA ||
1.59 djm 205: sig == NULL || siglen == 0)
1.52 djm 206: return SSH_ERR_INVALID_ARGUMENT;
1.61 djm 207: if (BN_num_bits(key->rsa->n) < SSH_RSA_MINIMUM_MODULUS_SIZE)
208: return SSH_ERR_KEY_LENGTH;
1.52 djm 209:
1.55 markus 210: if ((b = sshbuf_from(sig, siglen)) == NULL)
1.52 djm 211: return SSH_ERR_ALLOC_FAIL;
1.63 djm 212: if (sshbuf_get_cstring(b, &sigtype, NULL) != 0) {
1.52 djm 213: ret = SSH_ERR_INVALID_FORMAT;
214: goto out;
215: }
1.63 djm 216: /* XXX djm: need cert types that reliably yield SHA-2 signatures */
217: if (alg != NULL && strcmp(alg, sigtype) != 0 &&
218: strcmp(alg, "ssh-rsa-cert-v01@openssh.com") != 0) {
1.64 djm 219: error("%s: RSA signature type mismatch: "
220: "expected %s received %s", __func__, alg, sigtype);
1.63 djm 221: ret = SSH_ERR_SIGNATURE_INVALID;
222: goto out;
223: }
224: if ((hash_alg = rsa_hash_alg_from_ident(sigtype)) == -1) {
1.52 djm 225: ret = SSH_ERR_KEY_TYPE_MISMATCH;
226: goto out;
1.1 markus 227: }
1.52 djm 228: if (sshbuf_get_string(b, &sigblob, &len) != 0) {
229: ret = SSH_ERR_INVALID_FORMAT;
230: goto out;
231: }
232: if (sshbuf_len(b) != 0) {
233: ret = SSH_ERR_UNEXPECTED_TRAILING_DATA;
234: goto out;
1.19 markus 235: }
236: /* RSA_verify expects a signature of RSA_size */
237: modlen = RSA_size(key->rsa);
238: if (len > modlen) {
1.52 djm 239: ret = SSH_ERR_KEY_BITS_MISMATCH;
240: goto out;
1.19 markus 241: } else if (len < modlen) {
1.52 djm 242: diff = modlen - len;
243: osigblob = sigblob;
244: if ((sigblob = realloc(sigblob, modlen)) == NULL) {
245: sigblob = osigblob; /* put it back for clear/free */
246: ret = SSH_ERR_ALLOC_FAIL;
247: goto out;
248: }
1.19 markus 249: memmove(sigblob + diff, sigblob, len);
1.51 djm 250: explicit_bzero(sigblob, diff);
1.19 markus 251: len = modlen;
1.1 markus 252: }
1.50 djm 253: if ((dlen = ssh_digest_bytes(hash_alg)) == 0) {
1.52 djm 254: ret = SSH_ERR_INTERNAL_ERROR;
255: goto out;
1.7 markus 256: }
1.52 djm 257: if ((ret = ssh_digest_memory(hash_alg, data, datalen,
258: digest, sizeof(digest))) != 0)
259: goto out;
1.1 markus 260:
1.50 djm 261: ret = openssh_RSA_verify(hash_alg, digest, dlen, sigblob, len,
262: key->rsa);
1.52 djm 263: out:
1.65 ! jsing 264: freezero(sigblob, len);
1.63 djm 265: free(sigtype);
1.58 mmcc 266: sshbuf_free(b);
1.51 djm 267: explicit_bzero(digest, sizeof(digest));
1.25 markus 268: return ret;
269: }
270:
271: /*
272: * See:
273: * http://www.rsasecurity.com/rsalabs/pkcs/pkcs-1/
274: * ftp://ftp.rsasecurity.com/pub/pkcs/pkcs-1/pkcs-1v2-1.asn
275: */
1.55 markus 276:
1.25 markus 277: /*
278: * id-sha1 OBJECT IDENTIFIER ::= { iso(1) identified-organization(3)
279: * oiw(14) secsig(3) algorithms(2) 26 }
280: */
281: static const u_char id_sha1[] = {
282: 0x30, 0x21, /* type Sequence, length 0x21 (33) */
283: 0x30, 0x09, /* type Sequence, length 0x09 */
284: 0x06, 0x05, /* type OID, length 0x05 */
285: 0x2b, 0x0e, 0x03, 0x02, 0x1a, /* id-sha1 OID */
286: 0x05, 0x00, /* NULL */
287: 0x04, 0x14 /* Octet string, length 0x14 (20), followed by sha1 hash */
288: };
289:
1.55 markus 290: /*
291: * See http://csrc.nist.gov/groups/ST/crypto_apps_infra/csor/algorithms.html
292: * id-sha256 OBJECT IDENTIFIER ::= { joint-iso-itu-t(2) country(16) us(840)
293: * organization(1) gov(101) csor(3) nistAlgorithm(4) hashAlgs(2)
294: * id-sha256(1) }
295: */
296: static const u_char id_sha256[] = {
297: 0x30, 0x31, /* type Sequence, length 0x31 (49) */
298: 0x30, 0x0d, /* type Sequence, length 0x0d (13) */
299: 0x06, 0x09, /* type OID, length 0x09 */
300: 0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x01, /* id-sha256 */
301: 0x05, 0x00, /* NULL */
302: 0x04, 0x20 /* Octet string, length 0x20 (32), followed by sha256 hash */
303: };
304:
305: /*
306: * See http://csrc.nist.gov/groups/ST/crypto_apps_infra/csor/algorithms.html
307: * id-sha512 OBJECT IDENTIFIER ::= { joint-iso-itu-t(2) country(16) us(840)
308: * organization(1) gov(101) csor(3) nistAlgorithm(4) hashAlgs(2)
309: * id-sha256(3) }
310: */
311: static const u_char id_sha512[] = {
312: 0x30, 0x51, /* type Sequence, length 0x51 (81) */
313: 0x30, 0x0d, /* type Sequence, length 0x0d (13) */
314: 0x06, 0x09, /* type OID, length 0x09 */
315: 0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x03, /* id-sha512 */
316: 0x05, 0x00, /* NULL */
317: 0x04, 0x40 /* Octet string, length 0x40 (64), followed by sha512 hash */
318: };
319:
320: static int
321: rsa_hash_alg_oid(int hash_alg, const u_char **oidp, size_t *oidlenp)
322: {
323: switch (hash_alg) {
324: case SSH_DIGEST_SHA1:
325: *oidp = id_sha1;
326: *oidlenp = sizeof(id_sha1);
327: break;
328: case SSH_DIGEST_SHA256:
329: *oidp = id_sha256;
330: *oidlenp = sizeof(id_sha256);
331: break;
332: case SSH_DIGEST_SHA512:
333: *oidp = id_sha512;
334: *oidlenp = sizeof(id_sha512);
335: break;
336: default:
337: return SSH_ERR_INVALID_ARGUMENT;
338: }
339: return 0;
340: }
341:
1.25 markus 342: static int
1.52 djm 343: openssh_RSA_verify(int hash_alg, u_char *hash, size_t hashlen,
344: u_char *sigbuf, size_t siglen, RSA *rsa)
1.25 markus 345: {
1.54 djm 346: size_t rsasize = 0, oidlen = 0, hlen = 0;
347: int ret, len, oidmatch, hashmatch;
1.25 markus 348: const u_char *oid = NULL;
349: u_char *decrypted = NULL;
350:
1.55 markus 351: if ((ret = rsa_hash_alg_oid(hash_alg, &oid, &oidlen)) != 0)
352: return ret;
1.52 djm 353: ret = SSH_ERR_INTERNAL_ERROR;
1.55 markus 354: hlen = ssh_digest_bytes(hash_alg);
1.25 markus 355: if (hashlen != hlen) {
1.52 djm 356: ret = SSH_ERR_INVALID_ARGUMENT;
1.25 markus 357: goto done;
358: }
359: rsasize = RSA_size(rsa);
1.52 djm 360: if (rsasize <= 0 || rsasize > SSHBUF_MAX_BIGNUM ||
361: siglen == 0 || siglen > rsasize) {
362: ret = SSH_ERR_INVALID_ARGUMENT;
363: goto done;
364: }
365: if ((decrypted = malloc(rsasize)) == NULL) {
366: ret = SSH_ERR_ALLOC_FAIL;
1.25 markus 367: goto done;
368: }
369: if ((len = RSA_public_decrypt(siglen, sigbuf, decrypted, rsa,
370: RSA_PKCS1_PADDING)) < 0) {
1.52 djm 371: ret = SSH_ERR_LIBCRYPTO_ERROR;
1.25 markus 372: goto done;
373: }
1.52 djm 374: if (len < 0 || (size_t)len != hlen + oidlen) {
375: ret = SSH_ERR_INVALID_FORMAT;
1.25 markus 376: goto done;
377: }
1.44 djm 378: oidmatch = timingsafe_bcmp(decrypted, oid, oidlen) == 0;
379: hashmatch = timingsafe_bcmp(decrypted + oidlen, hash, hlen) == 0;
1.52 djm 380: if (!oidmatch || !hashmatch) {
381: ret = SSH_ERR_SIGNATURE_INVALID;
1.25 markus 382: goto done;
383: }
1.52 djm 384: ret = 0;
385: done:
1.65 ! jsing 386: freezero(decrypted, rsasize);
1.1 markus 387: return ret;
388: }
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