Annotation of src/usr.bin/ssh/sshsig.c, Revision 1.13
1.1 djm 1: /*
2: * Copyright (c) 2019 Google LLC
3: *
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.
7: *
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.
15: */
16:
17: #include <stdio.h>
18: #include <stdlib.h>
19: #include <stdarg.h>
20: #include <errno.h>
21: #include <string.h>
22: #include <unistd.h>
23:
24: #include "authfd.h"
25: #include "authfile.h"
26: #include "log.h"
27: #include "misc.h"
28: #include "sshbuf.h"
29: #include "sshsig.h"
30: #include "ssherr.h"
31: #include "sshkey.h"
32: #include "match.h"
33: #include "digest.h"
34:
35: #define SIG_VERSION 0x01
36: #define MAGIC_PREAMBLE "SSHSIG"
37: #define MAGIC_PREAMBLE_LEN (sizeof(MAGIC_PREAMBLE) - 1)
38: #define BEGIN_SIGNATURE "-----BEGIN SSH SIGNATURE-----\n"
39: #define END_SIGNATURE "-----END SSH SIGNATURE-----"
40: #define RSA_SIGN_ALG "rsa-sha2-512" /* XXX maybe make configurable */
41: #define RSA_SIGN_ALLOWED "rsa-sha2-512,rsa-sha2-256"
42: #define HASHALG_DEFAULT "sha512" /* XXX maybe make configurable */
43: #define HASHALG_ALLOWED "sha256,sha512"
44:
45: int
46: sshsig_armor(const struct sshbuf *blob, struct sshbuf **out)
47: {
48: struct sshbuf *buf = NULL;
49: int r = SSH_ERR_INTERNAL_ERROR;
50:
51: *out = NULL;
52:
53: if ((buf = sshbuf_new()) == NULL) {
54: error("%s: sshbuf_new failed", __func__);
55: r = SSH_ERR_ALLOC_FAIL;
56: goto out;
57: }
58:
59: if ((r = sshbuf_put(buf, BEGIN_SIGNATURE,
60: sizeof(BEGIN_SIGNATURE)-1)) != 0) {
61: error("%s: sshbuf_putf failed: %s", __func__, ssh_err(r));
62: goto out;
63: }
64:
65: if ((r = sshbuf_dtob64(blob, buf, 1)) != 0) {
66: error("%s: Couldn't base64 encode signature blob: %s",
67: __func__, ssh_err(r));
68: goto out;
69: }
70:
71: if ((r = sshbuf_put(buf, END_SIGNATURE,
72: sizeof(END_SIGNATURE)-1)) != 0 ||
73: (r = sshbuf_put_u8(buf, '\n')) != 0) {
74: error("%s: sshbuf_put failed: %s", __func__, ssh_err(r));
75: goto out;
76: }
77: /* success */
78: *out = buf;
79: buf = NULL; /* transferred */
80: r = 0;
81: out:
82: sshbuf_free(buf);
83: return r;
84: }
85:
86: int
87: sshsig_dearmor(struct sshbuf *sig, struct sshbuf **out)
88: {
89: int r;
90: size_t eoffset = 0;
91: struct sshbuf *buf = NULL;
92: struct sshbuf *sbuf = NULL;
93: char *b64 = NULL;
94:
95: if ((sbuf = sshbuf_fromb(sig)) == NULL) {
96: error("%s: sshbuf_fromb failed", __func__);
97: return SSH_ERR_ALLOC_FAIL;
98: }
99:
100: if ((r = sshbuf_cmp(sbuf, 0,
101: BEGIN_SIGNATURE, sizeof(BEGIN_SIGNATURE)-1)) != 0) {
102: error("Couldn't parse signature: missing header");
103: goto done;
104: }
105:
106: if ((r = sshbuf_consume(sbuf, sizeof(BEGIN_SIGNATURE)-1)) != 0) {
107: error("%s: sshbuf_consume failed: %s", __func__, ssh_err(r));
108: goto done;
109: }
110:
111: if ((r = sshbuf_find(sbuf, 0, "\n" END_SIGNATURE,
112: sizeof("\n" END_SIGNATURE)-1, &eoffset)) != 0) {
113: error("Couldn't parse signature: missing footer");
114: goto done;
115: }
116:
117: if ((r = sshbuf_consume_end(sbuf, sshbuf_len(sbuf)-eoffset)) != 0) {
118: error("%s: sshbuf_consume failed: %s", __func__, ssh_err(r));
119: goto done;
120: }
121:
122: if ((b64 = sshbuf_dup_string(sbuf)) == NULL) {
123: error("%s: sshbuf_dup_string failed", __func__);
124: r = SSH_ERR_ALLOC_FAIL;
125: goto done;
126: }
127:
128: if ((buf = sshbuf_new()) == NULL) {
129: error("%s: sshbuf_new() failed", __func__);
130: r = SSH_ERR_ALLOC_FAIL;
131: goto done;
132: }
133:
134: if ((r = sshbuf_b64tod(buf, b64)) != 0) {
1.3 naddy 135: error("Couldn't decode signature: %s", ssh_err(r));
1.1 djm 136: goto done;
137: }
138:
139: /* success */
140: *out = buf;
141: r = 0;
142: buf = NULL; /* transferred */
143: done:
144: sshbuf_free(buf);
145: sshbuf_free(sbuf);
146: free(b64);
147: return r;
148: }
149:
150: static int
151: sshsig_wrap_sign(struct sshkey *key, const char *hashalg,
1.7 djm 152: const char *sk_provider, const struct sshbuf *h_message,
153: const char *sig_namespace, struct sshbuf **out,
154: sshsig_signer *signer, void *signer_ctx)
1.1 djm 155: {
156: int r;
157: size_t slen = 0;
158: u_char *sig = NULL;
159: struct sshbuf *blob = NULL;
160: struct sshbuf *tosign = NULL;
161: const char *sign_alg = NULL;
162:
163: if ((tosign = sshbuf_new()) == NULL ||
164: (blob = sshbuf_new()) == NULL) {
165: error("%s: sshbuf_new failed", __func__);
166: r = SSH_ERR_ALLOC_FAIL;
167: goto done;
168: }
169:
170: if ((r = sshbuf_put(tosign, MAGIC_PREAMBLE, MAGIC_PREAMBLE_LEN)) != 0 ||
171: (r = sshbuf_put_cstring(tosign, sig_namespace)) != 0 ||
172: (r = sshbuf_put_string(tosign, NULL, 0)) != 0 || /* reserved */
173: (r = sshbuf_put_cstring(tosign, hashalg)) != 0 ||
1.6 djm 174: (r = sshbuf_put_stringb(tosign, h_message)) != 0) {
1.1 djm 175: error("Couldn't construct message to sign: %s", ssh_err(r));
176: goto done;
177: }
178:
179: /* If using RSA keys then default to a good signature algorithm */
180: if (sshkey_type_plain(key->type) == KEY_RSA)
181: sign_alg = RSA_SIGN_ALG;
182:
183: if (signer != NULL) {
184: if ((r = signer(key, &sig, &slen,
185: sshbuf_ptr(tosign), sshbuf_len(tosign),
1.7 djm 186: sign_alg, sk_provider, 0, signer_ctx)) != 0) {
1.1 djm 187: error("Couldn't sign message: %s", ssh_err(r));
188: goto done;
189: }
190: } else {
191: if ((r = sshkey_sign(key, &sig, &slen,
192: sshbuf_ptr(tosign), sshbuf_len(tosign),
1.7 djm 193: sign_alg, sk_provider, 0)) != 0) {
1.1 djm 194: error("Couldn't sign message: %s", ssh_err(r));
195: goto done;
196: }
197: }
198:
199: if ((r = sshbuf_put(blob, MAGIC_PREAMBLE, MAGIC_PREAMBLE_LEN)) != 0 ||
200: (r = sshbuf_put_u32(blob, SIG_VERSION)) != 0 ||
201: (r = sshkey_puts(key, blob)) != 0 ||
202: (r = sshbuf_put_cstring(blob, sig_namespace)) != 0 ||
203: (r = sshbuf_put_string(blob, NULL, 0)) != 0 || /* reserved */
204: (r = sshbuf_put_cstring(blob, hashalg)) != 0 ||
205: (r = sshbuf_put_string(blob, sig, slen)) != 0) {
206: error("Couldn't populate blob: %s", ssh_err(r));
207: goto done;
208: }
209:
1.12 markus 210: if (out != NULL) {
211: *out = blob;
212: blob = NULL;
213: }
1.1 djm 214: r = 0;
215: done:
216: free(sig);
217: sshbuf_free(blob);
218: sshbuf_free(tosign);
219: return r;
220: }
221:
222: /* Check preamble and version. */
223: static int
224: sshsig_parse_preamble(struct sshbuf *buf)
225: {
226: int r = SSH_ERR_INTERNAL_ERROR;
227: uint32_t sversion;
228:
229: if ((r = sshbuf_cmp(buf, 0, MAGIC_PREAMBLE, MAGIC_PREAMBLE_LEN)) != 0 ||
230: (r = sshbuf_consume(buf, (sizeof(MAGIC_PREAMBLE)-1))) != 0 ||
231: (r = sshbuf_get_u32(buf, &sversion)) != 0) {
232: error("Couldn't verify signature: invalid format");
233: return r;
234: }
235:
1.2 djm 236: if (sversion > SIG_VERSION) {
1.1 djm 237: error("Signature version %lu is larger than supported "
238: "version %u", (unsigned long)sversion, SIG_VERSION);
239: return SSH_ERR_INVALID_FORMAT;
240: }
241: return 0;
242: }
243:
244: static int
245: sshsig_check_hashalg(const char *hashalg)
246: {
1.2 djm 247: if (hashalg == NULL ||
248: match_pattern_list(hashalg, HASHALG_ALLOWED, 0) == 1)
1.1 djm 249: return 0;
250: error("%s: unsupported hash algorithm \"%.100s\"", __func__, hashalg);
251: return SSH_ERR_SIGN_ALG_UNSUPPORTED;
252: }
253:
254: static int
255: sshsig_peek_hashalg(struct sshbuf *signature, char **hashalgp)
256: {
257: struct sshbuf *buf = NULL;
258: char *hashalg = NULL;
259: int r = SSH_ERR_INTERNAL_ERROR;
260:
261: if (hashalgp != NULL)
262: *hashalgp = NULL;
263: if ((buf = sshbuf_fromb(signature)) == NULL)
264: return SSH_ERR_ALLOC_FAIL;
265: if ((r = sshsig_parse_preamble(buf)) != 0)
266: goto done;
267: if ((r = sshbuf_get_string_direct(buf, NULL, NULL)) != 0 ||
268: (r = sshbuf_get_string_direct(buf, NULL, NULL)) != 0 ||
269: (r = sshbuf_get_string(buf, NULL, NULL)) != 0 ||
270: (r = sshbuf_get_cstring(buf, &hashalg, NULL)) != 0 ||
271: (r = sshbuf_get_string_direct(buf, NULL, NULL)) != 0) {
272: error("Couldn't parse signature blob: %s", ssh_err(r));
273: goto done;
274: }
275:
276: /* success */
277: r = 0;
278: *hashalgp = hashalg;
279: hashalg = NULL;
280: done:
281: free(hashalg);
282: sshbuf_free(buf);
283: return r;
284: }
285:
286: static int
287: sshsig_wrap_verify(struct sshbuf *signature, const char *hashalg,
288: const struct sshbuf *h_message, const char *expect_namespace,
1.8 djm 289: struct sshkey **sign_keyp, struct sshkey_sig_details **sig_details)
1.1 djm 290: {
291: int r = SSH_ERR_INTERNAL_ERROR;
292: struct sshbuf *buf = NULL, *toverify = NULL;
293: struct sshkey *key = NULL;
294: const u_char *sig;
295: char *got_namespace = NULL, *sigtype = NULL, *sig_hashalg = NULL;
296: size_t siglen;
297:
1.2 djm 298: debug("%s: verify message length %zu", __func__, sshbuf_len(h_message));
1.8 djm 299: if (sig_details != NULL)
300: *sig_details = NULL;
1.1 djm 301: if (sign_keyp != NULL)
302: *sign_keyp = NULL;
303:
304: if ((toverify = sshbuf_new()) == NULL) {
305: error("%s: sshbuf_new failed", __func__);
306: r = SSH_ERR_ALLOC_FAIL;
307: goto done;
308: }
309: if ((r = sshbuf_put(toverify, MAGIC_PREAMBLE,
310: MAGIC_PREAMBLE_LEN)) != 0 ||
311: (r = sshbuf_put_cstring(toverify, expect_namespace)) != 0 ||
312: (r = sshbuf_put_string(toverify, NULL, 0)) != 0 || /* reserved */
313: (r = sshbuf_put_cstring(toverify, hashalg)) != 0 ||
1.6 djm 314: (r = sshbuf_put_stringb(toverify, h_message)) != 0) {
1.1 djm 315: error("Couldn't construct message to verify: %s", ssh_err(r));
316: goto done;
317: }
318:
319: if ((r = sshsig_parse_preamble(signature)) != 0)
320: goto done;
321:
322: if ((r = sshkey_froms(signature, &key)) != 0 ||
323: (r = sshbuf_get_cstring(signature, &got_namespace, NULL)) != 0 ||
324: (r = sshbuf_get_string(signature, NULL, NULL)) != 0 ||
325: (r = sshbuf_get_cstring(signature, &sig_hashalg, NULL)) != 0 ||
326: (r = sshbuf_get_string_direct(signature, &sig, &siglen)) != 0) {
327: error("Couldn't parse signature blob: %s", ssh_err(r));
328: goto done;
329: }
330:
331: if (sshbuf_len(signature) != 0) {
332: error("Signature contains trailing data");
333: r = SSH_ERR_INVALID_FORMAT;
334: goto done;
335: }
336:
337: if (strcmp(expect_namespace, got_namespace) != 0) {
338: error("Couldn't verify signature: namespace does not match");
339: debug("%s: expected namespace \"%s\" received \"%s\"",
340: __func__, expect_namespace, got_namespace);
341: r = SSH_ERR_SIGNATURE_INVALID;
342: goto done;
343: }
344: if (strcmp(hashalg, sig_hashalg) != 0) {
345: error("Couldn't verify signature: hash algorithm mismatch");
346: debug("%s: expected algorithm \"%s\" received \"%s\"",
347: __func__, hashalg, sig_hashalg);
348: r = SSH_ERR_SIGNATURE_INVALID;
349: goto done;
350: }
351: /* Ensure that RSA keys use an acceptable signature algorithm */
352: if (sshkey_type_plain(key->type) == KEY_RSA) {
353: if ((r = sshkey_get_sigtype(sig, siglen, &sigtype)) != 0) {
354: error("Couldn't verify signature: unable to get "
355: "signature type: %s", ssh_err(r));
356: goto done;
357: }
358: if (match_pattern_list(sigtype, RSA_SIGN_ALLOWED, 0) != 1) {
359: error("Couldn't verify signature: unsupported RSA "
360: "signature algorithm %s", sigtype);
361: r = SSH_ERR_SIGN_ALG_UNSUPPORTED;
362: goto done;
363: }
364: }
365: if ((r = sshkey_verify(key, sig, siglen, sshbuf_ptr(toverify),
1.8 djm 366: sshbuf_len(toverify), NULL, 0, sig_details)) != 0) {
1.1 djm 367: error("Signature verification failed: %s", ssh_err(r));
368: goto done;
369: }
370:
371: /* success */
372: r = 0;
373: if (sign_keyp != NULL) {
374: *sign_keyp = key;
375: key = NULL; /* transferred */
376: }
377: done:
378: free(got_namespace);
379: free(sigtype);
380: free(sig_hashalg);
381: sshbuf_free(buf);
382: sshbuf_free(toverify);
383: sshkey_free(key);
384: return r;
385: }
386:
1.2 djm 387: static int
388: hash_buffer(const struct sshbuf *m, const char *hashalg, struct sshbuf **bp)
1.1 djm 389: {
1.2 djm 390: char *hex, hash[SSH_DIGEST_MAX_LENGTH];
391: int alg, r = SSH_ERR_INTERNAL_ERROR;
1.1 djm 392: struct sshbuf *b = NULL;
393:
1.2 djm 394: *bp = NULL;
395: memset(hash, 0, sizeof(hash));
1.1 djm 396:
397: if ((r = sshsig_check_hashalg(hashalg)) != 0)
398: return r;
399: if ((alg = ssh_digest_alg_by_name(hashalg)) == -1) {
400: error("%s: can't look up hash algorithm %s",
1.2 djm 401: __func__, hashalg);
1.1 djm 402: return SSH_ERR_INTERNAL_ERROR;
403: }
1.2 djm 404: if ((r = ssh_digest_buffer(alg, m, hash, sizeof(hash))) != 0) {
1.1 djm 405: error("%s: ssh_digest_buffer failed: %s", __func__, ssh_err(r));
406: return r;
407: }
1.2 djm 408: if ((hex = tohex(hash, ssh_digest_bytes(alg))) != NULL) {
409: debug3("%s: final hash: %s", __func__, hex);
410: freezero(hex, strlen(hex));
411: }
412: if ((b = sshbuf_new()) == NULL) {
1.1 djm 413: r = SSH_ERR_ALLOC_FAIL;
414: goto out;
415: }
1.2 djm 416: if ((r = sshbuf_put(b, hash, ssh_digest_bytes(alg))) != 0) {
417: error("%s: sshbuf_put: %s", __func__, ssh_err(r));
418: goto out;
419: }
420: *bp = b;
421: b = NULL; /* transferred */
422: /* success */
423: r = 0;
424: out:
425: sshbuf_free(b);
426: explicit_bzero(hash, sizeof(hash));
1.12 markus 427: return r;
1.2 djm 428: }
429:
430: int
1.7 djm 431: sshsig_signb(struct sshkey *key, const char *hashalg, const char *sk_provider,
1.2 djm 432: const struct sshbuf *message, const char *sig_namespace,
433: struct sshbuf **out, sshsig_signer *signer, void *signer_ctx)
434: {
435: struct sshbuf *b = NULL;
436: int r = SSH_ERR_INTERNAL_ERROR;
437:
438: if (hashalg == NULL)
439: hashalg = HASHALG_DEFAULT;
440: if (out != NULL)
441: *out = NULL;
442: if ((r = hash_buffer(message, hashalg, &b)) != 0) {
443: error("%s: hash_buffer failed: %s", __func__, ssh_err(r));
444: goto out;
445: }
1.7 djm 446: if ((r = sshsig_wrap_sign(key, hashalg, sk_provider, b,
447: sig_namespace, out, signer, signer_ctx)) != 0)
1.1 djm 448: goto out;
449: /* success */
450: r = 0;
451: out:
452: sshbuf_free(b);
453: return r;
454: }
455:
456: int
1.2 djm 457: sshsig_verifyb(struct sshbuf *signature, const struct sshbuf *message,
1.8 djm 458: const char *expect_namespace, struct sshkey **sign_keyp,
459: struct sshkey_sig_details **sig_details)
1.1 djm 460: {
461: struct sshbuf *b = NULL;
1.2 djm 462: int r = SSH_ERR_INTERNAL_ERROR;
1.1 djm 463: char *hashalg = NULL;
464:
1.8 djm 465: if (sig_details != NULL)
466: *sig_details = NULL;
1.1 djm 467: if (sign_keyp != NULL)
468: *sign_keyp = NULL;
469: if ((r = sshsig_peek_hashalg(signature, &hashalg)) != 0)
470: return r;
1.2 djm 471: debug("%s: signature made with hash \"%s\"", __func__, hashalg);
472: if ((r = hash_buffer(message, hashalg, &b)) != 0) {
473: error("%s: hash_buffer failed: %s", __func__, ssh_err(r));
1.1 djm 474: goto out;
475: }
476: if ((r = sshsig_wrap_verify(signature, hashalg, b, expect_namespace,
1.8 djm 477: sign_keyp, sig_details)) != 0)
1.1 djm 478: goto out;
479: /* success */
480: r = 0;
481: out:
482: sshbuf_free(b);
483: free(hashalg);
484: return r;
485: }
486:
487: static int
1.2 djm 488: hash_file(int fd, const char *hashalg, struct sshbuf **bp)
1.1 djm 489: {
1.2 djm 490: char *hex, rbuf[8192], hash[SSH_DIGEST_MAX_LENGTH];
1.1 djm 491: ssize_t n, total = 0;
492: struct ssh_digest_ctx *ctx;
1.2 djm 493: int alg, oerrno, r = SSH_ERR_INTERNAL_ERROR;
494: struct sshbuf *b = NULL;
495:
496: *bp = NULL;
497: memset(hash, 0, sizeof(hash));
1.1 djm 498:
1.2 djm 499: if ((r = sshsig_check_hashalg(hashalg)) != 0)
500: return r;
501: if ((alg = ssh_digest_alg_by_name(hashalg)) == -1) {
502: error("%s: can't look up hash algorithm %s",
503: __func__, hashalg);
504: return SSH_ERR_INTERNAL_ERROR;
505: }
506: if ((ctx = ssh_digest_start(alg)) == NULL) {
1.1 djm 507: error("%s: ssh_digest_start failed", __func__);
508: return SSH_ERR_INTERNAL_ERROR;
509: }
510: for (;;) {
511: if ((n = read(fd, rbuf, sizeof(rbuf))) == -1) {
512: if (errno == EINTR || errno == EAGAIN)
513: continue;
514: oerrno = errno;
515: error("%s: read: %s", __func__, strerror(errno));
516: ssh_digest_free(ctx);
517: errno = oerrno;
1.2 djm 518: r = SSH_ERR_SYSTEM_ERROR;
519: goto out;
1.1 djm 520: } else if (n == 0) {
521: debug2("%s: hashed %zu bytes", __func__, total);
522: break; /* EOF */
523: }
524: total += (size_t)n;
525: if ((r = ssh_digest_update(ctx, rbuf, (size_t)n)) != 0) {
526: error("%s: ssh_digest_update: %s",
527: __func__, ssh_err(r));
1.2 djm 528: goto out;
1.1 djm 529: }
530: }
1.2 djm 531: if ((r = ssh_digest_final(ctx, hash, sizeof(hash))) != 0) {
1.1 djm 532: error("%s: ssh_digest_final: %s", __func__, ssh_err(r));
1.2 djm 533: goto out;
1.1 djm 534: }
1.2 djm 535: if ((hex = tohex(hash, ssh_digest_bytes(alg))) != NULL) {
1.1 djm 536: debug3("%s: final hash: %s", __func__, hex);
537: freezero(hex, strlen(hex));
538: }
1.2 djm 539: if ((b = sshbuf_new()) == NULL) {
540: r = SSH_ERR_ALLOC_FAIL;
541: goto out;
542: }
543: if ((r = sshbuf_put(b, hash, ssh_digest_bytes(alg))) != 0) {
544: error("%s: sshbuf_put: %s", __func__, ssh_err(r));
545: goto out;
546: }
547: *bp = b;
548: b = NULL; /* transferred */
1.1 djm 549: /* success */
1.2 djm 550: r = 0;
551: out:
552: sshbuf_free(b);
1.1 djm 553: ssh_digest_free(ctx);
1.2 djm 554: explicit_bzero(hash, sizeof(hash));
1.12 markus 555: return r;
1.1 djm 556: }
557:
558: int
1.7 djm 559: sshsig_sign_fd(struct sshkey *key, const char *hashalg, const char *sk_provider,
1.1 djm 560: int fd, const char *sig_namespace, struct sshbuf **out,
561: sshsig_signer *signer, void *signer_ctx)
562: {
563: struct sshbuf *b = NULL;
1.2 djm 564: int r = SSH_ERR_INTERNAL_ERROR;
1.1 djm 565:
1.2 djm 566: if (hashalg == NULL)
567: hashalg = HASHALG_DEFAULT;
1.1 djm 568: if (out != NULL)
569: *out = NULL;
1.2 djm 570: if ((r = hash_file(fd, hashalg, &b)) != 0) {
1.1 djm 571: error("%s: hash_file failed: %s", __func__, ssh_err(r));
572: return r;
573: }
1.7 djm 574: if ((r = sshsig_wrap_sign(key, hashalg, sk_provider, b,
575: sig_namespace, out, signer, signer_ctx)) != 0)
1.1 djm 576: goto out;
577: /* success */
578: r = 0;
579: out:
580: sshbuf_free(b);
581: return r;
582: }
583:
584: int
585: sshsig_verify_fd(struct sshbuf *signature, int fd,
1.8 djm 586: const char *expect_namespace, struct sshkey **sign_keyp,
587: struct sshkey_sig_details **sig_details)
1.1 djm 588: {
589: struct sshbuf *b = NULL;
1.2 djm 590: int r = SSH_ERR_INTERNAL_ERROR;
1.1 djm 591: char *hashalg = NULL;
592:
1.8 djm 593: if (sig_details != NULL)
594: *sig_details = NULL;
1.1 djm 595: if (sign_keyp != NULL)
596: *sign_keyp = NULL;
597: if ((r = sshsig_peek_hashalg(signature, &hashalg)) != 0)
598: return r;
1.2 djm 599: debug("%s: signature made with hash \"%s\"", __func__, hashalg);
600: if ((r = hash_file(fd, hashalg, &b)) != 0) {
1.1 djm 601: error("%s: hash_file failed: %s", __func__, ssh_err(r));
602: goto out;
603: }
604: if ((r = sshsig_wrap_verify(signature, hashalg, b, expect_namespace,
1.8 djm 605: sign_keyp, sig_details)) != 0)
1.1 djm 606: goto out;
607: /* success */
608: r = 0;
609: out:
610: sshbuf_free(b);
611: free(hashalg);
612: return r;
613: }
614:
1.4 djm 615: struct sshsigopt {
1.1 djm 616: int ca;
617: char *namespaces;
618: };
619:
1.4 djm 620: struct sshsigopt *
621: sshsigopt_parse(const char *opts, const char *path, u_long linenum,
1.1 djm 622: const char **errstrp)
623: {
1.4 djm 624: struct sshsigopt *ret;
1.1 djm 625: int r;
626: const char *errstr = NULL;
627:
628: if ((ret = calloc(1, sizeof(*ret))) == NULL)
629: return NULL;
630: if (opts == NULL || *opts == '\0')
631: return ret; /* Empty options yields empty options :) */
632:
633: while (*opts && *opts != ' ' && *opts != '\t') {
634: /* flag options */
635: if ((r = opt_flag("cert-authority", 0, &opts)) != -1) {
636: ret->ca = 1;
637: } else if (opt_match(&opts, "namespaces")) {
638: if (ret->namespaces != NULL) {
639: errstr = "multiple \"namespaces\" clauses";
640: goto fail;
641: }
642: ret->namespaces = opt_dequote(&opts, &errstr);
643: if (ret->namespaces == NULL)
644: goto fail;
645: }
646: /*
647: * Skip the comma, and move to the next option
648: * (or break out if there are no more).
649: */
650: if (*opts == '\0' || *opts == ' ' || *opts == '\t')
651: break; /* End of options. */
652: /* Anything other than a comma is an unknown option */
653: if (*opts != ',') {
654: errstr = "unknown key option";
655: goto fail;
656: }
657: opts++;
658: if (*opts == '\0') {
659: errstr = "unexpected end-of-options";
660: goto fail;
661: }
662: }
663: /* success */
664: return ret;
665: fail:
666: if (errstrp != NULL)
667: *errstrp = errstr;
1.5 djm 668: sshsigopt_free(ret);
1.1 djm 669: return NULL;
670: }
671:
1.4 djm 672: void
673: sshsigopt_free(struct sshsigopt *opts)
1.1 djm 674: {
675: if (opts == NULL)
676: return;
677: free(opts->namespaces);
678: free(opts);
679: }
680:
681: static int
1.9 djm 682: parse_principals_key_and_options(const char *path, u_long linenum, char *line,
683: const char *required_principal, char **principalsp, struct sshkey **keyp,
684: struct sshsigopt **sigoptsp)
1.1 djm 685: {
1.9 djm 686: char *opts = NULL, *tmp, *cp, *principals = NULL;
1.1 djm 687: const char *reason = NULL;
1.4 djm 688: struct sshsigopt *sigopts = NULL;
1.9 djm 689: struct sshkey *key = NULL;
690: int r = SSH_ERR_INTERNAL_ERROR;
1.1 djm 691:
1.9 djm 692: if (principalsp != NULL)
693: *principalsp = NULL;
694: if (sigoptsp != NULL)
695: *sigoptsp = NULL;
696: if (keyp != NULL)
697: *keyp = NULL;
1.1 djm 698:
699: cp = line;
700: cp = cp + strspn(cp, " \t"); /* skip leading whitespace */
701: if (*cp == '#' || *cp == '\0')
1.9 djm 702: return SSH_ERR_KEY_NOT_FOUND; /* blank or all-comment line */
703:
704: /* format: identity[,identity...] [option[,option...]] key */
705: if ((tmp = strdelimw(&cp)) == NULL) {
1.1 djm 706: error("%s:%lu: invalid line", path, linenum);
1.9 djm 707: r = SSH_ERR_INVALID_FORMAT;
708: goto out;
1.1 djm 709: }
1.9 djm 710: if ((principals = strdup(tmp)) == NULL) {
711: error("%s: strdup failed", __func__);
712: r = SSH_ERR_ALLOC_FAIL;
713: goto out;
714: }
715: /*
716: * Bail out early if we're looking for a particular principal and this
717: * line does not list it.
718: */
719: if (required_principal != NULL) {
720: if (match_pattern_list(required_principal,
721: principals, 0) != 1) {
722: /* principal didn't match */
723: r = SSH_ERR_KEY_NOT_FOUND;
724: goto out;
725: }
726: debug("%s: %s:%lu: matched principal \"%s\"",
727: __func__, path, linenum, required_principal);
1.1 djm 728: }
729:
1.9 djm 730: if ((key = sshkey_new(KEY_UNSPEC)) == NULL) {
731: error("%s: sshkey_new failed", __func__);
732: r = SSH_ERR_ALLOC_FAIL;
733: goto out;
734: }
735: if (sshkey_read(key, &cp) != 0) {
1.1 djm 736: /* no key? Check for options */
737: opts = cp;
738: if (sshkey_advance_past_options(&cp) != 0) {
1.9 djm 739: error("%s:%lu: invalid options", path, linenum);
740: r = SSH_ERR_INVALID_FORMAT;
741: goto out;
1.1 djm 742: }
743: *cp++ = '\0';
744: skip_space(&cp);
1.9 djm 745: if (sshkey_read(key, &cp) != 0) {
746: error("%s:%lu: invalid key", path, linenum);
747: r = SSH_ERR_INVALID_FORMAT;
748: goto out;
1.1 djm 749: }
750: }
751: debug3("%s:%lu: options %s", path, linenum, opts == NULL ? "" : opts);
1.4 djm 752: if ((sigopts = sshsigopt_parse(opts, path, linenum, &reason)) == NULL) {
1.1 djm 753: error("%s:%lu: bad options: %s", path, linenum, reason);
1.9 djm 754: r = SSH_ERR_INVALID_FORMAT;
755: goto out;
756: }
757: /* success */
758: if (principalsp != NULL) {
759: *principalsp = principals;
760: principals = NULL; /* transferred */
761: }
762: if (sigoptsp != NULL) {
763: *sigoptsp = sigopts;
764: sigopts = NULL; /* transferred */
765: }
766: if (keyp != NULL) {
767: *keyp = key;
768: key = NULL; /* transferred */
769: }
770: r = 0;
771: out:
772: free(principals);
773: sshsigopt_free(sigopts);
774: sshkey_free(key);
775: return r;
776: }
777:
778: static int
779: check_allowed_keys_line(const char *path, u_long linenum, char *line,
780: const struct sshkey *sign_key, const char *principal,
781: const char *sig_namespace)
782: {
783: struct sshkey *found_key = NULL;
784: int r, found = 0;
785: const char *reason = NULL;
786: struct sshsigopt *sigopts = NULL;
787:
788: /* Parse the line */
789: if ((r = parse_principals_key_and_options(path, linenum, line,
790: principal, NULL, &found_key, &sigopts)) != 0) {
791: /* error already logged */
1.1 djm 792: goto done;
793: }
794:
795: /* Check whether options preclude the use of this key */
796: if (sigopts->namespaces != NULL &&
797: match_pattern_list(sig_namespace, sigopts->namespaces, 0) != 1) {
798: error("%s:%lu: key is not permitted for use in signature "
799: "namespace \"%s\"", path, linenum, sig_namespace);
800: goto done;
801: }
802:
803: if (!sigopts->ca && sshkey_equal(found_key, sign_key)) {
804: /* Exact match of key */
805: debug("%s:%lu: matched key and principal", path, linenum);
806: /* success */
807: found = 1;
808: } else if (sigopts->ca && sshkey_is_cert(sign_key) &&
809: sshkey_equal_public(sign_key->cert->signature_key, found_key)) {
810: /* Match of certificate's CA key */
811: if ((r = sshkey_cert_check_authority(sign_key, 0, 1,
812: principal, &reason)) != 0) {
813: error("%s:%lu: certificate not authorized: %s",
814: path, linenum, reason);
815: goto done;
816: }
817: debug("%s:%lu: matched certificate CA key", path, linenum);
818: /* success */
819: found = 1;
820: } else {
821: /* Principal matched but key didn't */
822: goto done;
823: }
824: done:
825: sshkey_free(found_key);
1.4 djm 826: sshsigopt_free(sigopts);
1.1 djm 827: return found ? 0 : SSH_ERR_KEY_NOT_FOUND;
828: }
829:
830: int
831: sshsig_check_allowed_keys(const char *path, const struct sshkey *sign_key,
832: const char *principal, const char *sig_namespace)
833: {
834: FILE *f = NULL;
835: char *line = NULL;
836: size_t linesize = 0;
837: u_long linenum = 0;
1.12 markus 838: int r = SSH_ERR_INTERNAL_ERROR, oerrno;
1.1 djm 839:
840: /* Check key and principal against file */
841: if ((f = fopen(path, "r")) == NULL) {
842: oerrno = errno;
843: error("Unable to open allowed keys file \"%s\": %s",
844: path, strerror(errno));
845: errno = oerrno;
846: return SSH_ERR_SYSTEM_ERROR;
847: }
848:
849: while (getline(&line, &linesize, f) != -1) {
850: linenum++;
851: r = check_allowed_keys_line(path, linenum, line, sign_key,
852: principal, sig_namespace);
1.2 djm 853: free(line);
854: line = NULL;
1.1 djm 855: if (r == SSH_ERR_KEY_NOT_FOUND)
856: continue;
857: else if (r == 0) {
858: /* success */
859: fclose(f);
860: return 0;
861: } else
862: break;
863: }
864: /* Either we hit an error parsing or we simply didn't find the key */
865: fclose(f);
866: free(line);
867: return r == 0 ? SSH_ERR_KEY_NOT_FOUND : r;
868: }
1.10 djm 869:
870: static int
1.11 djm 871: cert_filter_principals(const char *path, u_long linenum,
872: char **principalsp, const struct sshkey *cert)
873: {
874: char *cp, *oprincipals, *principals;
875: const char *reason;
876: struct sshbuf *nprincipals;
877: int r = SSH_ERR_INTERNAL_ERROR, success = 0;
878:
879: oprincipals = principals = *principalsp;
880: *principalsp = NULL;
881:
882: if ((nprincipals = sshbuf_new()) == NULL)
883: return SSH_ERR_ALLOC_FAIL;
884:
885: while ((cp = strsep(&principals, ",")) != NULL && *cp != '\0') {
886: if (strcspn(cp, "!?*") != strlen(cp)) {
887: debug("%s:%lu: principal \"%s\" not authorized: "
888: "contains wildcards", path, linenum, cp);
889: continue;
890: }
891: /* Check against principals list in certificate */
892: if ((r = sshkey_cert_check_authority(cert, 0, 1,
893: cp, &reason)) != 0) {
894: debug("%s:%lu: principal \"%s\" not authorized: %s",
895: path, linenum, cp, reason);
896: continue;
897: }
898: if ((r = sshbuf_putf(nprincipals, "%s%s",
899: sshbuf_len(nprincipals) != 0 ? "," : "", cp)) != 0) {
900: error("%s: buffer error", __func__);
901: goto out;
902: }
903: }
904: if (sshbuf_len(nprincipals) == 0) {
905: error("%s:%lu: no valid principals found", path, linenum);
906: r = SSH_ERR_KEY_CERT_INVALID;
907: goto out;
908: }
909: if ((principals = sshbuf_dup_string(nprincipals)) == NULL) {
910: error("%s: buffer error", __func__);
911: goto out;
912: }
913: /* success */
914: success = 1;
915: *principalsp = principals;
916: out:
917: sshbuf_free(nprincipals);
918: free(oprincipals);
919: return success ? 0 : r;
920: }
921:
922: static int
923: get_matching_principals_from_line(const char *path, u_long linenum, char *line,
1.10 djm 924: const struct sshkey *sign_key, char **principalsp)
925: {
926: struct sshkey *found_key = NULL;
927: char *principals = NULL;
928: int r, found = 0;
929: struct sshsigopt *sigopts = NULL;
930:
931: if (principalsp != NULL)
932: *principalsp = NULL;
933:
934: /* Parse the line */
935: if ((r = parse_principals_key_and_options(path, linenum, line,
936: NULL, &principals, &found_key, &sigopts)) != 0) {
937: /* error already logged */
938: goto done;
939: }
940:
941: if (!sigopts->ca && sshkey_equal(found_key, sign_key)) {
942: /* Exact match of key */
943: debug("%s:%lu: matched key", path, linenum);
944: /* success */
945: found = 1;
946: } else if (sigopts->ca && sshkey_is_cert(sign_key) &&
947: sshkey_equal_public(sign_key->cert->signature_key, found_key)) {
1.11 djm 948: /* Remove principals listed in file but not allowed by cert */
949: if ((r = cert_filter_principals(path, linenum,
950: &principals, sign_key)) != 0) {
951: /* error already displayed */
952: debug("%s:%lu: cert_filter_principals: %s",
953: path, linenum, ssh_err(r));
1.10 djm 954: goto done;
955: }
956: debug("%s:%lu: matched certificate CA key", path, linenum);
957: /* success */
958: found = 1;
959: } else {
960: /* Key didn't match */
961: goto done;
962: }
963: done:
1.13 ! markus 964: if (found && principalsp != NULL) {
1.10 djm 965: *principalsp = principals;
966: principals = NULL; /* transferred */
967: }
968: free(principals);
969: sshkey_free(found_key);
970: sshsigopt_free(sigopts);
971: return found ? 0 : SSH_ERR_KEY_NOT_FOUND;
972: }
973:
974: int
1.11 djm 975: sshsig_find_principals(const char *path, const struct sshkey *sign_key,
976: char **principals)
1.10 djm 977: {
978: FILE *f = NULL;
979: char *line = NULL;
980: size_t linesize = 0;
981: u_long linenum = 0;
982: int r, oerrno;
983:
984: if ((f = fopen(path, "r")) == NULL) {
985: oerrno = errno;
986: error("Unable to open allowed keys file \"%s\": %s",
987: path, strerror(errno));
988: errno = oerrno;
989: return SSH_ERR_SYSTEM_ERROR;
990: }
991:
992: while (getline(&line, &linesize, f) != -1) {
993: linenum++;
1.11 djm 994: r = get_matching_principals_from_line(path, linenum, line,
995: sign_key, principals);
1.10 djm 996: free(line);
997: line = NULL;
998: if (r == SSH_ERR_KEY_NOT_FOUND)
999: continue;
1000: else if (r == 0) {
1001: /* success */
1002: fclose(f);
1003: return 0;
1004: } else
1005: break;
1006: }
1007: free(line);
1008: /* Either we hit an error parsing or we simply didn't find the key */
1009: if (ferror(f) != 0) {
1010: oerrno = errno;
1011: fclose(f);
1012: error("Unable to read allowed keys file \"%s\": %s",
1013: path, strerror(errno));
1014: errno = oerrno;
1015: return SSH_ERR_SYSTEM_ERROR;
1016: }
1017: fclose(f);
1018: return r == 0 ? SSH_ERR_KEY_NOT_FOUND : r;
1019: }
1020:
1021: int
1022: sshsig_get_pubkey(struct sshbuf *signature, struct sshkey **pubkey)
1023: {
1024: struct sshkey *pk = NULL;
1025: int r = SSH_ERR_SIGNATURE_INVALID;
1026:
1.13 ! markus 1027: if (pubkey == NULL)
! 1028: return SSH_ERR_INTERNAL_ERROR;
1.10 djm 1029: if ((r = sshsig_parse_preamble(signature)) != 0)
1030: return r;
1031: if ((r = sshkey_froms(signature, &pk)) != 0)
1032: return r;
1033:
1034: *pubkey = pk;
1035: pk = NULL;
1036: return 0;
1037: }
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