Annotation of src/usr.bin/ssh/sshsig.c, Revision 1.7
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:
210: *out = blob;
211: blob = NULL;
212: r = 0;
213: done:
214: free(sig);
215: sshbuf_free(blob);
216: sshbuf_free(tosign);
217: return r;
218: }
219:
220: /* Check preamble and version. */
221: static int
222: sshsig_parse_preamble(struct sshbuf *buf)
223: {
224: int r = SSH_ERR_INTERNAL_ERROR;
225: uint32_t sversion;
226:
227: if ((r = sshbuf_cmp(buf, 0, MAGIC_PREAMBLE, MAGIC_PREAMBLE_LEN)) != 0 ||
228: (r = sshbuf_consume(buf, (sizeof(MAGIC_PREAMBLE)-1))) != 0 ||
229: (r = sshbuf_get_u32(buf, &sversion)) != 0) {
230: error("Couldn't verify signature: invalid format");
231: return r;
232: }
233:
1.2 djm 234: if (sversion > SIG_VERSION) {
1.1 djm 235: error("Signature version %lu is larger than supported "
236: "version %u", (unsigned long)sversion, SIG_VERSION);
237: return SSH_ERR_INVALID_FORMAT;
238: }
239: return 0;
240: }
241:
242: static int
243: sshsig_check_hashalg(const char *hashalg)
244: {
1.2 djm 245: if (hashalg == NULL ||
246: match_pattern_list(hashalg, HASHALG_ALLOWED, 0) == 1)
1.1 djm 247: return 0;
248: error("%s: unsupported hash algorithm \"%.100s\"", __func__, hashalg);
249: return SSH_ERR_SIGN_ALG_UNSUPPORTED;
250: }
251:
252: static int
253: sshsig_peek_hashalg(struct sshbuf *signature, char **hashalgp)
254: {
255: struct sshbuf *buf = NULL;
256: char *hashalg = NULL;
257: int r = SSH_ERR_INTERNAL_ERROR;
258:
259: if (hashalgp != NULL)
260: *hashalgp = NULL;
261: if ((buf = sshbuf_fromb(signature)) == NULL)
262: return SSH_ERR_ALLOC_FAIL;
263: if ((r = sshsig_parse_preamble(buf)) != 0)
264: goto done;
265: if ((r = sshbuf_get_string_direct(buf, NULL, NULL)) != 0 ||
266: (r = sshbuf_get_string_direct(buf, NULL, NULL)) != 0 ||
267: (r = sshbuf_get_string(buf, NULL, NULL)) != 0 ||
268: (r = sshbuf_get_cstring(buf, &hashalg, NULL)) != 0 ||
269: (r = sshbuf_get_string_direct(buf, NULL, NULL)) != 0) {
270: error("Couldn't parse signature blob: %s", ssh_err(r));
271: goto done;
272: }
273:
274: /* success */
275: r = 0;
276: *hashalgp = hashalg;
277: hashalg = NULL;
278: done:
279: free(hashalg);
280: sshbuf_free(buf);
281: return r;
282: }
283:
284: static int
285: sshsig_wrap_verify(struct sshbuf *signature, const char *hashalg,
286: const struct sshbuf *h_message, const char *expect_namespace,
287: struct sshkey **sign_keyp)
288: {
289: int r = SSH_ERR_INTERNAL_ERROR;
290: struct sshbuf *buf = NULL, *toverify = NULL;
291: struct sshkey *key = NULL;
292: const u_char *sig;
293: char *got_namespace = NULL, *sigtype = NULL, *sig_hashalg = NULL;
294: size_t siglen;
295:
1.2 djm 296: debug("%s: verify message length %zu", __func__, sshbuf_len(h_message));
1.1 djm 297: if (sign_keyp != NULL)
298: *sign_keyp = NULL;
299:
300: if ((toverify = sshbuf_new()) == NULL) {
301: error("%s: sshbuf_new failed", __func__);
302: r = SSH_ERR_ALLOC_FAIL;
303: goto done;
304: }
305: if ((r = sshbuf_put(toverify, MAGIC_PREAMBLE,
306: MAGIC_PREAMBLE_LEN)) != 0 ||
307: (r = sshbuf_put_cstring(toverify, expect_namespace)) != 0 ||
308: (r = sshbuf_put_string(toverify, NULL, 0)) != 0 || /* reserved */
309: (r = sshbuf_put_cstring(toverify, hashalg)) != 0 ||
1.6 djm 310: (r = sshbuf_put_stringb(toverify, h_message)) != 0) {
1.1 djm 311: error("Couldn't construct message to verify: %s", ssh_err(r));
312: goto done;
313: }
314:
315: if ((r = sshsig_parse_preamble(signature)) != 0)
316: goto done;
317:
318: if ((r = sshkey_froms(signature, &key)) != 0 ||
319: (r = sshbuf_get_cstring(signature, &got_namespace, NULL)) != 0 ||
320: (r = sshbuf_get_string(signature, NULL, NULL)) != 0 ||
321: (r = sshbuf_get_cstring(signature, &sig_hashalg, NULL)) != 0 ||
322: (r = sshbuf_get_string_direct(signature, &sig, &siglen)) != 0) {
323: error("Couldn't parse signature blob: %s", ssh_err(r));
324: goto done;
325: }
326:
327: if (sshbuf_len(signature) != 0) {
328: error("Signature contains trailing data");
329: r = SSH_ERR_INVALID_FORMAT;
330: goto done;
331: }
332:
333: if (strcmp(expect_namespace, got_namespace) != 0) {
334: error("Couldn't verify signature: namespace does not match");
335: debug("%s: expected namespace \"%s\" received \"%s\"",
336: __func__, expect_namespace, got_namespace);
337: r = SSH_ERR_SIGNATURE_INVALID;
338: goto done;
339: }
340: if (strcmp(hashalg, sig_hashalg) != 0) {
341: error("Couldn't verify signature: hash algorithm mismatch");
342: debug("%s: expected algorithm \"%s\" received \"%s\"",
343: __func__, hashalg, sig_hashalg);
344: r = SSH_ERR_SIGNATURE_INVALID;
345: goto done;
346: }
347: /* Ensure that RSA keys use an acceptable signature algorithm */
348: if (sshkey_type_plain(key->type) == KEY_RSA) {
349: if ((r = sshkey_get_sigtype(sig, siglen, &sigtype)) != 0) {
350: error("Couldn't verify signature: unable to get "
351: "signature type: %s", ssh_err(r));
352: goto done;
353: }
354: if (match_pattern_list(sigtype, RSA_SIGN_ALLOWED, 0) != 1) {
355: error("Couldn't verify signature: unsupported RSA "
356: "signature algorithm %s", sigtype);
357: r = SSH_ERR_SIGN_ALG_UNSUPPORTED;
358: goto done;
359: }
360: }
361: if ((r = sshkey_verify(key, sig, siglen, sshbuf_ptr(toverify),
362: sshbuf_len(toverify), NULL, 0)) != 0) {
363: error("Signature verification failed: %s", ssh_err(r));
364: goto done;
365: }
366:
367: /* success */
368: r = 0;
369: if (sign_keyp != NULL) {
370: *sign_keyp = key;
371: key = NULL; /* transferred */
372: }
373: done:
374: free(got_namespace);
375: free(sigtype);
376: free(sig_hashalg);
377: sshbuf_free(buf);
378: sshbuf_free(toverify);
379: sshkey_free(key);
380: return r;
381: }
382:
1.2 djm 383: static int
384: hash_buffer(const struct sshbuf *m, const char *hashalg, struct sshbuf **bp)
1.1 djm 385: {
1.2 djm 386: char *hex, hash[SSH_DIGEST_MAX_LENGTH];
387: int alg, r = SSH_ERR_INTERNAL_ERROR;
1.1 djm 388: struct sshbuf *b = NULL;
389:
1.2 djm 390: *bp = NULL;
391: memset(hash, 0, sizeof(hash));
1.1 djm 392:
393: if ((r = sshsig_check_hashalg(hashalg)) != 0)
394: return r;
395: if ((alg = ssh_digest_alg_by_name(hashalg)) == -1) {
396: error("%s: can't look up hash algorithm %s",
1.2 djm 397: __func__, hashalg);
1.1 djm 398: return SSH_ERR_INTERNAL_ERROR;
399: }
1.2 djm 400: if ((r = ssh_digest_buffer(alg, m, hash, sizeof(hash))) != 0) {
1.1 djm 401: error("%s: ssh_digest_buffer failed: %s", __func__, ssh_err(r));
402: return r;
403: }
1.2 djm 404: if ((hex = tohex(hash, ssh_digest_bytes(alg))) != NULL) {
405: debug3("%s: final hash: %s", __func__, hex);
406: freezero(hex, strlen(hex));
407: }
408: if ((b = sshbuf_new()) == NULL) {
1.1 djm 409: r = SSH_ERR_ALLOC_FAIL;
410: goto out;
411: }
1.2 djm 412: if ((r = sshbuf_put(b, hash, ssh_digest_bytes(alg))) != 0) {
413: error("%s: sshbuf_put: %s", __func__, ssh_err(r));
414: goto out;
415: }
416: *bp = b;
417: b = NULL; /* transferred */
418: /* success */
419: r = 0;
420: out:
421: sshbuf_free(b);
422: explicit_bzero(hash, sizeof(hash));
423: return 0;
424: }
425:
426: int
1.7 ! djm 427: sshsig_signb(struct sshkey *key, const char *hashalg, const char *sk_provider,
1.2 djm 428: const struct sshbuf *message, const char *sig_namespace,
429: struct sshbuf **out, sshsig_signer *signer, void *signer_ctx)
430: {
431: struct sshbuf *b = NULL;
432: int r = SSH_ERR_INTERNAL_ERROR;
433:
434: if (hashalg == NULL)
435: hashalg = HASHALG_DEFAULT;
436: if (out != NULL)
437: *out = NULL;
438: if ((r = hash_buffer(message, hashalg, &b)) != 0) {
439: error("%s: hash_buffer failed: %s", __func__, ssh_err(r));
440: goto out;
441: }
1.7 ! djm 442: if ((r = sshsig_wrap_sign(key, hashalg, sk_provider, b,
! 443: sig_namespace, out, signer, signer_ctx)) != 0)
1.1 djm 444: goto out;
445: /* success */
446: r = 0;
447: out:
448: sshbuf_free(b);
449: return r;
450: }
451:
452: int
1.2 djm 453: sshsig_verifyb(struct sshbuf *signature, const struct sshbuf *message,
1.1 djm 454: const char *expect_namespace, struct sshkey **sign_keyp)
455: {
456: struct sshbuf *b = NULL;
1.2 djm 457: int r = SSH_ERR_INTERNAL_ERROR;
1.1 djm 458: char *hashalg = NULL;
459:
460: if (sign_keyp != NULL)
461: *sign_keyp = NULL;
462:
463: if ((r = sshsig_peek_hashalg(signature, &hashalg)) != 0)
464: return r;
1.2 djm 465: debug("%s: signature made with hash \"%s\"", __func__, hashalg);
466: if ((r = hash_buffer(message, hashalg, &b)) != 0) {
467: error("%s: hash_buffer failed: %s", __func__, ssh_err(r));
1.1 djm 468: goto out;
469: }
470: if ((r = sshsig_wrap_verify(signature, hashalg, b, expect_namespace,
471: sign_keyp)) != 0)
472: goto out;
473: /* success */
474: r = 0;
475: out:
476: sshbuf_free(b);
477: free(hashalg);
478: return r;
479: }
480:
481: static int
1.2 djm 482: hash_file(int fd, const char *hashalg, struct sshbuf **bp)
1.1 djm 483: {
1.2 djm 484: char *hex, rbuf[8192], hash[SSH_DIGEST_MAX_LENGTH];
1.1 djm 485: ssize_t n, total = 0;
486: struct ssh_digest_ctx *ctx;
1.2 djm 487: int alg, oerrno, r = SSH_ERR_INTERNAL_ERROR;
488: struct sshbuf *b = NULL;
489:
490: *bp = NULL;
491: memset(hash, 0, sizeof(hash));
1.1 djm 492:
1.2 djm 493: if ((r = sshsig_check_hashalg(hashalg)) != 0)
494: return r;
495: if ((alg = ssh_digest_alg_by_name(hashalg)) == -1) {
496: error("%s: can't look up hash algorithm %s",
497: __func__, hashalg);
498: return SSH_ERR_INTERNAL_ERROR;
499: }
500: if ((ctx = ssh_digest_start(alg)) == NULL) {
1.1 djm 501: error("%s: ssh_digest_start failed", __func__);
502: return SSH_ERR_INTERNAL_ERROR;
503: }
504: for (;;) {
505: if ((n = read(fd, rbuf, sizeof(rbuf))) == -1) {
506: if (errno == EINTR || errno == EAGAIN)
507: continue;
508: oerrno = errno;
509: error("%s: read: %s", __func__, strerror(errno));
510: ssh_digest_free(ctx);
511: errno = oerrno;
1.2 djm 512: r = SSH_ERR_SYSTEM_ERROR;
513: goto out;
1.1 djm 514: } else if (n == 0) {
515: debug2("%s: hashed %zu bytes", __func__, total);
516: break; /* EOF */
517: }
518: total += (size_t)n;
519: if ((r = ssh_digest_update(ctx, rbuf, (size_t)n)) != 0) {
520: error("%s: ssh_digest_update: %s",
521: __func__, ssh_err(r));
1.2 djm 522: goto out;
1.1 djm 523: }
524: }
1.2 djm 525: if ((r = ssh_digest_final(ctx, hash, sizeof(hash))) != 0) {
1.1 djm 526: error("%s: ssh_digest_final: %s", __func__, ssh_err(r));
1.2 djm 527: goto out;
1.1 djm 528: }
1.2 djm 529: if ((hex = tohex(hash, ssh_digest_bytes(alg))) != NULL) {
1.1 djm 530: debug3("%s: final hash: %s", __func__, hex);
531: freezero(hex, strlen(hex));
532: }
1.2 djm 533: if ((b = sshbuf_new()) == NULL) {
534: r = SSH_ERR_ALLOC_FAIL;
535: goto out;
536: }
537: if ((r = sshbuf_put(b, hash, ssh_digest_bytes(alg))) != 0) {
538: error("%s: sshbuf_put: %s", __func__, ssh_err(r));
539: goto out;
540: }
541: *bp = b;
542: b = NULL; /* transferred */
1.1 djm 543: /* success */
1.2 djm 544: r = 0;
545: out:
546: sshbuf_free(b);
1.1 djm 547: ssh_digest_free(ctx);
1.2 djm 548: explicit_bzero(hash, sizeof(hash));
1.1 djm 549: return 0;
550: }
551:
552: int
1.7 ! djm 553: sshsig_sign_fd(struct sshkey *key, const char *hashalg, const char *sk_provider,
1.1 djm 554: int fd, const char *sig_namespace, struct sshbuf **out,
555: sshsig_signer *signer, void *signer_ctx)
556: {
557: struct sshbuf *b = NULL;
1.2 djm 558: int r = SSH_ERR_INTERNAL_ERROR;
1.1 djm 559:
1.2 djm 560: if (hashalg == NULL)
561: hashalg = HASHALG_DEFAULT;
1.1 djm 562: if (out != NULL)
563: *out = NULL;
1.2 djm 564: if ((r = hash_file(fd, hashalg, &b)) != 0) {
1.1 djm 565: error("%s: hash_file failed: %s", __func__, ssh_err(r));
566: return r;
567: }
1.7 ! djm 568: if ((r = sshsig_wrap_sign(key, hashalg, sk_provider, b,
! 569: sig_namespace, out, signer, signer_ctx)) != 0)
1.1 djm 570: goto out;
571: /* success */
572: r = 0;
573: out:
574: sshbuf_free(b);
575: return r;
576: }
577:
578: int
579: sshsig_verify_fd(struct sshbuf *signature, int fd,
580: const char *expect_namespace, struct sshkey **sign_keyp)
581: {
582: struct sshbuf *b = NULL;
1.2 djm 583: int r = SSH_ERR_INTERNAL_ERROR;
1.1 djm 584: char *hashalg = NULL;
585:
586: if (sign_keyp != NULL)
587: *sign_keyp = NULL;
588:
589: if ((r = sshsig_peek_hashalg(signature, &hashalg)) != 0)
590: return r;
1.2 djm 591: debug("%s: signature made with hash \"%s\"", __func__, hashalg);
592: if ((r = hash_file(fd, hashalg, &b)) != 0) {
1.1 djm 593: error("%s: hash_file failed: %s", __func__, ssh_err(r));
594: goto out;
595: }
596: if ((r = sshsig_wrap_verify(signature, hashalg, b, expect_namespace,
597: sign_keyp)) != 0)
598: goto out;
599: /* success */
600: r = 0;
601: out:
602: sshbuf_free(b);
603: free(hashalg);
604: return r;
605: }
606:
1.4 djm 607: struct sshsigopt {
1.1 djm 608: int ca;
609: char *namespaces;
610: };
611:
1.4 djm 612: struct sshsigopt *
613: sshsigopt_parse(const char *opts, const char *path, u_long linenum,
1.1 djm 614: const char **errstrp)
615: {
1.4 djm 616: struct sshsigopt *ret;
1.1 djm 617: int r;
618: const char *errstr = NULL;
619:
620: if ((ret = calloc(1, sizeof(*ret))) == NULL)
621: return NULL;
622: if (opts == NULL || *opts == '\0')
623: return ret; /* Empty options yields empty options :) */
624:
625: while (*opts && *opts != ' ' && *opts != '\t') {
626: /* flag options */
627: if ((r = opt_flag("cert-authority", 0, &opts)) != -1) {
628: ret->ca = 1;
629: } else if (opt_match(&opts, "namespaces")) {
630: if (ret->namespaces != NULL) {
631: errstr = "multiple \"namespaces\" clauses";
632: goto fail;
633: }
634: ret->namespaces = opt_dequote(&opts, &errstr);
635: if (ret->namespaces == NULL)
636: goto fail;
637: }
638: /*
639: * Skip the comma, and move to the next option
640: * (or break out if there are no more).
641: */
642: if (*opts == '\0' || *opts == ' ' || *opts == '\t')
643: break; /* End of options. */
644: /* Anything other than a comma is an unknown option */
645: if (*opts != ',') {
646: errstr = "unknown key option";
647: goto fail;
648: }
649: opts++;
650: if (*opts == '\0') {
651: errstr = "unexpected end-of-options";
652: goto fail;
653: }
654: }
655: /* success */
656: return ret;
657: fail:
658: if (errstrp != NULL)
659: *errstrp = errstr;
1.5 djm 660: sshsigopt_free(ret);
1.1 djm 661: return NULL;
662: }
663:
1.4 djm 664: void
665: sshsigopt_free(struct sshsigopt *opts)
1.1 djm 666: {
667: if (opts == NULL)
668: return;
669: free(opts->namespaces);
670: free(opts);
671: }
672:
673: static int
674: check_allowed_keys_line(const char *path, u_long linenum, char *line,
675: const struct sshkey *sign_key, const char *principal,
676: const char *sig_namespace)
677: {
678: struct sshkey *found_key = NULL;
679: char *cp, *opts = NULL, *identities = NULL;
680: int r, found = 0;
681: const char *reason = NULL;
1.4 djm 682: struct sshsigopt *sigopts = NULL;
1.1 djm 683:
684: if ((found_key = sshkey_new(KEY_UNSPEC)) == NULL) {
685: error("%s: sshkey_new failed", __func__);
686: return SSH_ERR_ALLOC_FAIL;
687: }
688:
689: /* format: identity[,identity...] [option[,option...]] key */
690: cp = line;
691: cp = cp + strspn(cp, " \t"); /* skip leading whitespace */
692: if (*cp == '#' || *cp == '\0')
693: goto done;
694: if ((identities = strdelimw(&cp)) == NULL) {
695: error("%s:%lu: invalid line", path, linenum);
696: goto done;
697: }
698: if (match_pattern_list(principal, identities, 0) != 1) {
699: /* principal didn't match */
700: goto done;
701: }
702: debug("%s: %s:%lu: matched principal \"%s\"",
703: __func__, path, linenum, principal);
704:
705: if (sshkey_read(found_key, &cp) != 0) {
706: /* no key? Check for options */
707: opts = cp;
708: if (sshkey_advance_past_options(&cp) != 0) {
709: error("%s:%lu: invalid options",
710: path, linenum);
711: goto done;
712: }
713: *cp++ = '\0';
714: skip_space(&cp);
715: if (sshkey_read(found_key, &cp) != 0) {
716: error("%s:%lu: invalid key", path,
717: linenum);
718: goto done;
719: }
720: }
721: debug3("%s:%lu: options %s", path, linenum, opts == NULL ? "" : opts);
1.4 djm 722: if ((sigopts = sshsigopt_parse(opts, path, linenum, &reason)) == NULL) {
1.1 djm 723: error("%s:%lu: bad options: %s", path, linenum, reason);
724: goto done;
725: }
726:
727: /* Check whether options preclude the use of this key */
728: if (sigopts->namespaces != NULL &&
729: match_pattern_list(sig_namespace, sigopts->namespaces, 0) != 1) {
730: error("%s:%lu: key is not permitted for use in signature "
731: "namespace \"%s\"", path, linenum, sig_namespace);
732: goto done;
733: }
734:
735: if (!sigopts->ca && sshkey_equal(found_key, sign_key)) {
736: /* Exact match of key */
737: debug("%s:%lu: matched key and principal", path, linenum);
738: /* success */
739: found = 1;
740: } else if (sigopts->ca && sshkey_is_cert(sign_key) &&
741: sshkey_equal_public(sign_key->cert->signature_key, found_key)) {
742: /* Match of certificate's CA key */
743: if ((r = sshkey_cert_check_authority(sign_key, 0, 1,
744: principal, &reason)) != 0) {
745: error("%s:%lu: certificate not authorized: %s",
746: path, linenum, reason);
747: goto done;
748: }
749: debug("%s:%lu: matched certificate CA key", path, linenum);
750: /* success */
751: found = 1;
752: } else {
753: /* Principal matched but key didn't */
754: goto done;
755: }
756: done:
757: sshkey_free(found_key);
1.4 djm 758: sshsigopt_free(sigopts);
1.1 djm 759: return found ? 0 : SSH_ERR_KEY_NOT_FOUND;
760: }
761:
762: int
763: sshsig_check_allowed_keys(const char *path, const struct sshkey *sign_key,
764: const char *principal, const char *sig_namespace)
765: {
766: FILE *f = NULL;
767: char *line = NULL;
768: size_t linesize = 0;
769: u_long linenum = 0;
770: int r, oerrno;
771:
772: /* Check key and principal against file */
773: if ((f = fopen(path, "r")) == NULL) {
774: oerrno = errno;
775: error("Unable to open allowed keys file \"%s\": %s",
776: path, strerror(errno));
777: errno = oerrno;
778: return SSH_ERR_SYSTEM_ERROR;
779: }
780:
781: while (getline(&line, &linesize, f) != -1) {
782: linenum++;
783: r = check_allowed_keys_line(path, linenum, line, sign_key,
784: principal, sig_namespace);
1.2 djm 785: free(line);
786: line = NULL;
1.1 djm 787: if (r == SSH_ERR_KEY_NOT_FOUND)
788: continue;
789: else if (r == 0) {
790: /* success */
791: fclose(f);
792: return 0;
793: } else
794: break;
795: }
796: /* Either we hit an error parsing or we simply didn't find the key */
797: fclose(f);
798: free(line);
799: return r == 0 ? SSH_ERR_KEY_NOT_FOUND : r;
800: }
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