forked from openssh/openssh-portable
-
Notifications
You must be signed in to change notification settings - Fork 3
/
auth2-pubkey.c
1185 lines (1077 loc) · 32.6 KB
/
auth2-pubkey.c
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
/* $OpenBSD: auth2-pubkey.c,v 1.86 2018/09/20 03:28:06 djm Exp $ */
/*
* Copyright (c) 2000 Markus Friedl. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
/*
* Copyright 2008 Sun Microsystems, Inc. All rights reserved.
* Copyright 2015 Joyent, Inc.
* Use is subject to license terms.
*/
#include "includes.h"
#include <sys/types.h>
#include <sys/stat.h>
#include <errno.h>
#include <fcntl.h>
#ifdef HAVE_PATHS_H
# include <paths.h>
#endif
#include <pwd.h>
#include <signal.h>
#include <stdio.h>
#include <stdarg.h>
#include <string.h>
#include <time.h>
#include <unistd.h>
#include <limits.h>
#include <dlfcn.h>
#include "xmalloc.h"
#include "ssh.h"
#include "ssh2.h"
#include "packet.h"
#include "sshbuf.h"
#include "digest.h"
#include "log.h"
#include "misc.h"
#include "servconf.h"
#include "compat.h"
#include "sshkey.h"
#include "hostfile.h"
#include "auth.h"
#include "pathnames.h"
#include "uidswap.h"
#include "auth-options.h"
#include "canohost.h"
#ifdef GSSAPI
#include "ssh-gss.h"
#endif
#include "monitor_wrap.h"
#include "authfile.h"
#include "match.h"
#include "ssherr.h"
#include "channels.h" /* XXX for session.h */
#include "session.h" /* XXX for child_set_env(); refactor? */
/* import */
extern ServerOptions options;
extern u_char *session_id2;
extern u_int session_id2_len;
static const char *RSA_SYM_NAME = "sshd_user_rsa_key_allowed";
static const char *ECDSA_SYM_NAME = "sshd_user_ecdsa_key_allowed";
typedef int (*RSA_SYM)(struct passwd *, RSA *, const char *);
typedef int (*ECDSA_SYM)(struct passwd *, EC_KEY *, const char *);
static const char *UNIV_SYM_NAME = "sshd_user_key_allowed";
typedef int (*UNIV_SYM)(struct passwd *, const char *,
const u_char *, size_t);
static char *
format_key(const struct sshkey *key)
{
char *ret, *fp = sshkey_fingerprint(key,
options.fingerprint_hash, SSH_FP_DEFAULT);
xasprintf(&ret, "%s %s", sshkey_type(key), fp);
free(fp);
return ret;
}
static int
userauth_pubkey(struct ssh *ssh)
{
Authctxt *authctxt = ssh->authctxt;
struct passwd *pw = authctxt->pw;
struct sshbuf *b = NULL;
struct sshkey *key = NULL;
char *pkalg = NULL, *userstyle = NULL, *key_s = NULL, *ca_s = NULL;
u_char *pkblob = NULL, *sig = NULL, have_sig;
size_t blen, slen;
int r, pktype;
int authenticated = 0;
struct sshauthopt *authopts = NULL;
if ((r = sshpkt_get_u8(ssh, &have_sig)) != 0 ||
(r = sshpkt_get_cstring(ssh, &pkalg, NULL)) != 0 ||
(r = sshpkt_get_string(ssh, &pkblob, &blen)) != 0)
fatal("%s: parse request failed: %s", __func__, ssh_err(r));
pktype = sshkey_type_from_name(pkalg);
if (pktype == KEY_UNSPEC) {
/* this is perfectly legal */
verbose("%s: unsupported public key algorithm: %s",
__func__, pkalg);
goto done;
}
if ((r = sshkey_from_blob(pkblob, blen, &key)) != 0) {
error("%s: could not parse key: %s", __func__, ssh_err(r));
goto done;
}
if (key == NULL) {
error("%s: cannot decode key: %s", __func__, pkalg);
goto done;
}
if (key->type != pktype) {
error("%s: type mismatch for decoded key "
"(received %d, expected %d)", __func__, key->type, pktype);
goto done;
}
if (sshkey_type_plain(key->type) == KEY_RSA &&
(ssh->compat & SSH_BUG_RSASIGMD5) != 0) {
logit("Refusing RSA key because client uses unsafe "
"signature scheme");
goto done;
}
if (auth2_key_already_used(authctxt, key)) {
logit("refusing previously-used %s key", sshkey_type(key));
goto done;
}
if (match_pattern_list(pkalg, options.pubkey_key_types, 0) != 1) {
logit("%s: key type %s not in PubkeyAcceptedKeyTypes",
__func__, sshkey_ssh_name(key));
goto done;
}
if ((r = sshkey_check_cert_sigtype(key,
options.ca_sign_algorithms)) != 0) {
logit("%s: certificate signature algorithm %s: %s", __func__,
(key->cert == NULL || key->cert->signature_type == NULL) ?
"(null)" : key->cert->signature_type, ssh_err(r));
goto done;
}
key_s = format_key(key);
if (sshkey_is_cert(key))
ca_s = format_key(key->cert->signature_key);
if (have_sig) {
debug3("%s: have %s signature for %s%s%s",
__func__, pkalg, key_s,
ca_s == NULL ? "" : " CA ",
ca_s == NULL ? "" : ca_s);
if ((r = sshpkt_get_string(ssh, &sig, &slen)) != 0 ||
(r = sshpkt_get_end(ssh)) != 0)
fatal("%s: %s", __func__, ssh_err(r));
if ((b = sshbuf_new()) == NULL)
fatal("%s: sshbuf_new failed", __func__);
if (ssh->compat & SSH_OLD_SESSIONID) {
if ((r = sshbuf_put(b, session_id2,
session_id2_len)) != 0)
fatal("%s: sshbuf_put session id: %s",
__func__, ssh_err(r));
} else {
if ((r = sshbuf_put_string(b, session_id2,
session_id2_len)) != 0)
fatal("%s: sshbuf_put_string session id: %s",
__func__, ssh_err(r));
}
if (!authctxt->valid || authctxt->user == NULL) {
debug2("%s: disabled because of invalid user",
__func__);
goto done;
}
/* reconstruct packet */
xasprintf(&userstyle, "%s%s%s", authctxt->user,
authctxt->style ? ":" : "",
authctxt->style ? authctxt->style : "");
if ((r = sshbuf_put_u8(b, SSH2_MSG_USERAUTH_REQUEST)) != 0 ||
(r = sshbuf_put_cstring(b, userstyle)) != 0 ||
(r = sshbuf_put_cstring(b, authctxt->service)) != 0 ||
(r = sshbuf_put_cstring(b, "publickey")) != 0 ||
(r = sshbuf_put_u8(b, have_sig)) != 0 ||
(r = sshbuf_put_cstring(b, pkalg)) != 0 ||
(r = sshbuf_put_string(b, pkblob, blen)) != 0)
fatal("%s: build packet failed: %s",
__func__, ssh_err(r));
#ifdef DEBUG_PK
sshbuf_dump(b, stderr);
#endif
/* test for correct signature */
authenticated = 0;
if (PRIVSEP(user_key_allowed(ssh, pw, key, 1, &authopts)) &&
PRIVSEP(sshkey_verify(key, sig, slen,
sshbuf_ptr(b), sshbuf_len(b),
(ssh->compat & SSH_BUG_SIGTYPE) == 0 ? pkalg : NULL,
ssh->compat)) == 0) {
authenticated = 1;
}
auth2_record_key(authctxt, authenticated, key);
} else {
debug("%s: test pkalg %s pkblob %s%s%s",
__func__, pkalg, key_s,
ca_s == NULL ? "" : " CA ",
ca_s == NULL ? "" : ca_s);
if ((r = sshpkt_get_end(ssh)) != 0)
fatal("%s: %s", __func__, ssh_err(r));
if (!authctxt->valid || authctxt->user == NULL) {
debug2("%s: disabled because of invalid user",
__func__);
goto done;
}
/* XXX fake reply and always send PK_OK ? */
/*
* XXX this allows testing whether a user is allowed
* to login: if you happen to have a valid pubkey this
* message is sent. the message is NEVER sent at all
* if a user is not allowed to login. is this an
* issue? -markus
*/
if (PRIVSEP(user_key_allowed(ssh, pw, key, 0, NULL))) {
if ((r = sshpkt_start(ssh, SSH2_MSG_USERAUTH_PK_OK))
!= 0 ||
(r = sshpkt_put_cstring(ssh, pkalg)) != 0 ||
(r = sshpkt_put_string(ssh, pkblob, blen)) != 0 ||
(r = sshpkt_send(ssh)) != 0 ||
(r = ssh_packet_write_wait(ssh)) != 0)
fatal("%s: %s", __func__, ssh_err(r));
authctxt->postponed = 1;
}
}
done:
if (authenticated == 1 && auth_activate_options(ssh, authopts) != 0) {
debug("%s: key options inconsistent with existing", __func__);
authenticated = 0;
}
debug2("%s: authenticated %d pkalg %s", __func__, authenticated, pkalg);
sshbuf_free(b);
sshauthopt_free(authopts);
sshkey_free(key);
free(userstyle);
free(pkalg);
free(pkblob);
free(key_s);
free(ca_s);
free(sig);
return authenticated;
}
static int
match_principals_option(const char *principal_list, struct sshkey_cert *cert)
{
char *result;
u_int i;
/* XXX percent_expand() sequences for authorized_principals? */
for (i = 0; i < cert->nprincipals; i++) {
if ((result = match_list(cert->principals[i],
principal_list, NULL)) != NULL) {
debug3("matched principal from key options \"%.100s\"",
result);
free(result);
return 1;
}
}
return 0;
}
/*
* Process a single authorized_principals format line. Returns 0 and sets
* authoptsp is principal is authorised, -1 otherwise. "loc" is used as a
* log preamble for file/line information.
*/
static int
check_principals_line(struct ssh *ssh, char *cp, const struct sshkey_cert *cert,
const char *loc, struct sshauthopt **authoptsp)
{
u_int i, found = 0;
char *ep, *line_opts;
const char *reason = NULL;
struct sshauthopt *opts = NULL;
if (authoptsp != NULL)
*authoptsp = NULL;
/* Trim trailing whitespace. */
ep = cp + strlen(cp) - 1;
while (ep > cp && (*ep == '\n' || *ep == ' ' || *ep == '\t'))
*ep-- = '\0';
/*
* If the line has internal whitespace then assume it has
* key options.
*/
line_opts = NULL;
if ((ep = strrchr(cp, ' ')) != NULL ||
(ep = strrchr(cp, '\t')) != NULL) {
for (; *ep == ' ' || *ep == '\t'; ep++)
;
line_opts = cp;
cp = ep;
}
if ((opts = sshauthopt_parse(line_opts, &reason)) == NULL) {
debug("%s: bad principals options: %s", loc, reason);
auth_debug_add("%s: bad principals options: %s", loc, reason);
return -1;
}
/* Check principals in cert against those on line */
for (i = 0; i < cert->nprincipals; i++) {
if (strcmp(cp, cert->principals[i]) != 0)
continue;
debug3("%s: matched principal \"%.100s\"",
loc, cert->principals[i]);
found = 1;
}
if (found && authoptsp != NULL) {
*authoptsp = opts;
opts = NULL;
}
sshauthopt_free(opts);
return found ? 0 : -1;
}
static int
process_principals(struct ssh *ssh, FILE *f, const char *file,
const struct sshkey_cert *cert, struct sshauthopt **authoptsp)
{
char loc[256], *line = NULL, *cp, *ep;
size_t linesize = 0;
u_long linenum = 0;
u_int found_principal = 0;
if (authoptsp != NULL)
*authoptsp = NULL;
while (getline(&line, &linesize, f) != -1) {
linenum++;
/* Always consume entire input */
if (found_principal)
continue;
/* Skip leading whitespace. */
for (cp = line; *cp == ' ' || *cp == '\t'; cp++)
;
/* Skip blank and comment lines. */
if ((ep = strchr(cp, '#')) != NULL)
*ep = '\0';
if (!*cp || *cp == '\n')
continue;
snprintf(loc, sizeof(loc), "%.200s:%lu", file, linenum);
if (check_principals_line(ssh, cp, cert, loc, authoptsp) == 0)
found_principal = 1;
}
free(line);
return found_principal;
}
/* XXX remove pw args here and elsewhere once ssh->authctxt is guaranteed */
static int
match_principals_file(struct ssh *ssh, struct passwd *pw, char *file,
struct sshkey_cert *cert, struct sshauthopt **authoptsp)
{
FILE *f;
int success;
if (authoptsp != NULL)
*authoptsp = NULL;
temporarily_use_uid(pw);
debug("trying authorized principals file %s", file);
if ((f = auth_openprincipals(file, pw, options.strict_modes)) == NULL) {
restore_uid();
return 0;
}
success = process_principals(ssh, f, file, cert, authoptsp);
fclose(f);
restore_uid();
return success;
}
/*
* Checks whether principal is allowed in output of command.
* returns 1 if the principal is allowed or 0 otherwise.
*/
static int
match_principals_command(struct ssh *ssh, struct passwd *user_pw,
const struct sshkey *key, struct sshauthopt **authoptsp)
{
struct passwd *runas_pw = NULL;
const struct sshkey_cert *cert = key->cert;
FILE *f = NULL;
int r, ok, found_principal = 0;
int i, ac = 0, uid_swapped = 0;
pid_t pid;
char *tmp, *username = NULL, *command = NULL, **av = NULL;
char *ca_fp = NULL, *key_fp = NULL, *catext = NULL, *keytext = NULL;
char serial_s[16], uidstr[32];
void (*osigchld)(int);
if (authoptsp != NULL)
*authoptsp = NULL;
if (options.authorized_principals_command == NULL)
return 0;
if (options.authorized_principals_command_user == NULL) {
error("No user for AuthorizedPrincipalsCommand specified, "
"skipping");
return 0;
}
/*
* NB. all returns later this function should go via "out" to
* ensure the original SIGCHLD handler is restored properly.
*/
osigchld = signal(SIGCHLD, SIG_DFL);
/* Prepare and verify the user for the command */
username = percent_expand(options.authorized_principals_command_user,
"u", user_pw->pw_name, (char *)NULL);
runas_pw = getpwnam(username);
if (runas_pw == NULL) {
error("AuthorizedPrincipalsCommandUser \"%s\" not found: %s",
username, strerror(errno));
goto out;
}
/* Turn the command into an argument vector */
if (argv_split(options.authorized_principals_command, &ac, &av) != 0) {
error("AuthorizedPrincipalsCommand \"%s\" contains "
"invalid quotes", command);
goto out;
}
if (ac == 0) {
error("AuthorizedPrincipalsCommand \"%s\" yielded no arguments",
command);
goto out;
}
if ((ca_fp = sshkey_fingerprint(cert->signature_key,
options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) {
error("%s: sshkey_fingerprint failed", __func__);
goto out;
}
if ((key_fp = sshkey_fingerprint(key,
options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) {
error("%s: sshkey_fingerprint failed", __func__);
goto out;
}
if ((r = sshkey_to_base64(cert->signature_key, &catext)) != 0) {
error("%s: sshkey_to_base64 failed: %s", __func__, ssh_err(r));
goto out;
}
if ((r = sshkey_to_base64(key, &keytext)) != 0) {
error("%s: sshkey_to_base64 failed: %s", __func__, ssh_err(r));
goto out;
}
snprintf(serial_s, sizeof(serial_s), "%llu",
(unsigned long long)cert->serial);
snprintf(uidstr, sizeof(uidstr), "%llu",
(unsigned long long)user_pw->pw_uid);
for (i = 1; i < ac; i++) {
tmp = percent_expand(av[i],
"U", uidstr,
"u", user_pw->pw_name,
"h", user_pw->pw_dir,
"t", sshkey_ssh_name(key),
"T", sshkey_ssh_name(cert->signature_key),
"f", key_fp,
"F", ca_fp,
"k", keytext,
"K", catext,
"i", cert->key_id,
"s", serial_s,
(char *)NULL);
if (tmp == NULL)
fatal("%s: percent_expand failed", __func__);
free(av[i]);
av[i] = tmp;
}
/* Prepare a printable command for logs, etc. */
command = argv_assemble(ac, av);
if ((pid = subprocess("AuthorizedPrincipalsCommand", runas_pw, command,
ac, av, &f,
SSH_SUBPROCESS_STDOUT_CAPTURE|SSH_SUBPROCESS_STDERR_DISCARD)) == 0)
goto out;
uid_swapped = 1;
temporarily_use_uid(runas_pw);
ok = process_principals(ssh, f, "(command)", cert, authoptsp);
fclose(f);
f = NULL;
if (exited_cleanly(pid, "AuthorizedPrincipalsCommand", command, 0) != 0)
goto out;
/* Read completed successfully */
found_principal = ok;
out:
if (f != NULL)
fclose(f);
signal(SIGCHLD, osigchld);
for (i = 0; i < ac; i++)
free(av[i]);
free(av);
if (uid_swapped)
restore_uid();
free(command);
free(username);
free(ca_fp);
free(key_fp);
free(catext);
free(keytext);
return found_principal;
}
static void
skip_space(char **cpp)
{
char *cp;
for (cp = *cpp; *cp == ' ' || *cp == '\t'; cp++)
;
*cpp = cp;
}
/*
* Advanced *cpp past the end of key options, defined as the first unquoted
* whitespace character. Returns 0 on success or -1 on failure (e.g.
* unterminated quotes).
*/
static int
advance_past_options(char **cpp)
{
char *cp = *cpp;
int quoted = 0;
for (; *cp && (quoted || (*cp != ' ' && *cp != '\t')); cp++) {
if (*cp == '\\' && cp[1] == '"')
cp++; /* Skip both */
else if (*cp == '"')
quoted = !quoted;
}
*cpp = cp;
/* return failure for unterminated quotes */
return (*cp == '\0' && quoted) ? -1 : 0;
}
/*
* Check a single line of an authorized_keys-format file. Returns 0 if key
* matches, -1 otherwise. Will return key/cert options via *authoptsp
* on success. "loc" is used as file/line location in log messages.
*/
static int
check_authkey_line(struct ssh *ssh, struct passwd *pw, struct sshkey *key,
char *cp, const char *loc, struct sshauthopt **authoptsp)
{
int want_keytype = sshkey_is_cert(key) ? KEY_UNSPEC : key->type;
struct sshkey *found = NULL;
struct sshauthopt *keyopts = NULL, *certopts = NULL, *finalopts = NULL;
char *key_options = NULL, *fp = NULL;
const char *reason = NULL;
int ret = -1;
if (authoptsp != NULL)
*authoptsp = NULL;
if ((found = sshkey_new(want_keytype)) == NULL) {
debug3("%s: keytype %d failed", __func__, want_keytype);
goto out;
}
/* XXX djm: peek at key type in line and skip if unwanted */
if (sshkey_read(found, &cp) != 0) {
/* no key? check for options */
debug2("%s: check options: '%s'", loc, cp);
key_options = cp;
if (advance_past_options(&cp) != 0) {
reason = "invalid key option string";
goto fail_reason;
}
skip_space(&cp);
if (sshkey_read(found, &cp) != 0) {
/* still no key? advance to next line*/
debug2("%s: advance: '%s'", loc, cp);
goto out;
}
}
/* Parse key options now; we need to know if this is a CA key */
if ((keyopts = sshauthopt_parse(key_options, &reason)) == NULL) {
debug("%s: bad key options: %s", loc, reason);
auth_debug_add("%s: bad key options: %s", loc, reason);
goto out;
}
/* Ignore keys that don't match or incorrectly marked as CAs */
if (sshkey_is_cert(key)) {
/* Certificate; check signature key against CA */
if (!sshkey_equal(found, key->cert->signature_key) ||
!keyopts->cert_authority)
goto out;
} else {
/* Plain key: check it against key found in file */
if (!sshkey_equal(found, key) || keyopts->cert_authority)
goto out;
}
/* We have a candidate key, perform authorisation checks */
if ((fp = sshkey_fingerprint(found,
options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL)
fatal("%s: fingerprint failed", __func__);
debug("%s: matching %s found: %s %s", loc,
sshkey_is_cert(key) ? "CA" : "key", sshkey_type(found), fp);
if (auth_authorise_keyopts(ssh, pw, keyopts,
sshkey_is_cert(key), loc) != 0) {
reason = "Refused by key options";
goto fail_reason;
}
/* That's all we need for plain keys. */
if (!sshkey_is_cert(key)) {
verbose("Accepted key %s %s found at %s",
sshkey_type(found), fp, loc);
finalopts = keyopts;
keyopts = NULL;
goto success;
}
/*
* Additional authorisation for certificates.
*/
/* Parse and check options present in certificate */
if ((certopts = sshauthopt_from_cert(key)) == NULL) {
reason = "Invalid certificate options";
goto fail_reason;
}
if (auth_authorise_keyopts(ssh, pw, certopts, 0, loc) != 0) {
reason = "Refused by certificate options";
goto fail_reason;
}
if ((finalopts = sshauthopt_merge(keyopts, certopts, &reason)) == NULL)
goto fail_reason;
/*
* If the user has specified a list of principals as
* a key option, then prefer that list to matching
* their username in the certificate principals list.
*/
if (keyopts->cert_principals != NULL &&
!match_principals_option(keyopts->cert_principals, key->cert)) {
reason = "Certificate does not contain an authorized principal";
goto fail_reason;
}
if (sshkey_cert_check_authority(key, 0, 0,
keyopts->cert_principals == NULL ? pw->pw_name : NULL, &reason) != 0)
goto fail_reason;
verbose("Accepted certificate ID \"%s\" (serial %llu) "
"signed by CA %s %s found at %s",
key->cert->key_id,
(unsigned long long)key->cert->serial,
sshkey_type(found), fp, loc);
success:
if (finalopts == NULL)
fatal("%s: internal error: missing options", __func__);
if (authoptsp != NULL) {
*authoptsp = finalopts;
finalopts = NULL;
}
/* success */
ret = 0;
goto out;
fail_reason:
error("%s", reason);
auth_debug_add("%s", reason);
out:
free(fp);
sshauthopt_free(keyopts);
sshauthopt_free(certopts);
sshauthopt_free(finalopts);
sshkey_free(found);
return ret;
}
/*
* Checks whether key is allowed in authorized_keys-format file,
* returns 1 if the key is allowed or 0 otherwise.
*/
static int
check_authkeys_file(struct ssh *ssh, struct passwd *pw, FILE *f,
char *file, struct sshkey *key, struct sshauthopt **authoptsp)
{
char *cp, *line = NULL, loc[256];
size_t linesize = 0;
int found_key = 0;
u_long linenum = 0;
if (authoptsp != NULL)
*authoptsp = NULL;
while (getline(&line, &linesize, f) != -1) {
linenum++;
/* Always consume entire file */
if (found_key)
continue;
/* Skip leading whitespace, empty and comment lines. */
cp = line;
skip_space(&cp);
if (!*cp || *cp == '\n' || *cp == '#')
continue;
snprintf(loc, sizeof(loc), "%.200s:%lu", file, linenum);
if (check_authkey_line(ssh, pw, key, cp, loc, authoptsp) == 0)
found_key = 1;
}
free(line);
return found_key;
}
/* Authenticate a certificate key against TrustedUserCAKeys */
static int
user_cert_trusted_ca(struct ssh *ssh, struct passwd *pw, struct sshkey *key,
struct sshauthopt **authoptsp)
{
char *ca_fp, *principals_file = NULL;
const char *reason;
struct sshauthopt *principals_opts = NULL, *cert_opts = NULL;
struct sshauthopt *final_opts = NULL;
int r, ret = 0, found_principal = 0, use_authorized_principals;
if (authoptsp != NULL)
*authoptsp = NULL;
if (!sshkey_is_cert(key) || options.trusted_user_ca_keys == NULL)
return 0;
if ((ca_fp = sshkey_fingerprint(key->cert->signature_key,
options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL)
return 0;
if ((r = sshkey_in_file(key->cert->signature_key,
options.trusted_user_ca_keys, 1, 0)) != 0) {
debug2("%s: CA %s %s is not listed in %s: %s", __func__,
sshkey_type(key->cert->signature_key), ca_fp,
options.trusted_user_ca_keys, ssh_err(r));
goto out;
}
/*
* If AuthorizedPrincipals is in use, then compare the certificate
* principals against the names in that file rather than matching
* against the username.
*/
if ((principals_file = authorized_principals_file(pw)) != NULL) {
if (match_principals_file(ssh, pw, principals_file,
key->cert, &principals_opts))
found_principal = 1;
}
/* Try querying command if specified */
if (!found_principal && match_principals_command(ssh, pw, key,
&principals_opts))
found_principal = 1;
/* If principals file or command is specified, then require a match */
use_authorized_principals = principals_file != NULL ||
options.authorized_principals_command != NULL;
if (!found_principal && use_authorized_principals) {
reason = "Certificate does not contain an authorized principal";
goto fail_reason;
}
if (use_authorized_principals && principals_opts == NULL)
fatal("%s: internal error: missing principals_opts", __func__);
if (sshkey_cert_check_authority(key, 0, 1,
use_authorized_principals ? NULL : pw->pw_name, &reason) != 0)
goto fail_reason;
/* Check authority from options in key and from principals file/cmd */
if ((cert_opts = sshauthopt_from_cert(key)) == NULL) {
reason = "Invalid certificate options";
goto fail_reason;
}
if (auth_authorise_keyopts(ssh, pw, cert_opts, 0, "cert") != 0) {
reason = "Refused by certificate options";
goto fail_reason;
}
if (principals_opts == NULL) {
final_opts = cert_opts;
cert_opts = NULL;
} else {
if (auth_authorise_keyopts(ssh, pw, principals_opts, 0,
"principals") != 0) {
reason = "Refused by certificate principals options";
goto fail_reason;
}
if ((final_opts = sshauthopt_merge(principals_opts,
cert_opts, &reason)) == NULL) {
fail_reason:
error("%s", reason);
auth_debug_add("%s", reason);
goto out;
}
}
/* Success */
verbose("Accepted certificate ID \"%s\" (serial %llu) signed by "
"%s CA %s via %s", key->cert->key_id,
(unsigned long long)key->cert->serial,
sshkey_type(key->cert->signature_key), ca_fp,
options.trusted_user_ca_keys);
if (authoptsp != NULL) {
*authoptsp = final_opts;
final_opts = NULL;
}
ret = 1;
out:
sshauthopt_free(principals_opts);
sshauthopt_free(cert_opts);
sshauthopt_free(final_opts);
free(principals_file);
free(ca_fp);
return ret;
}
/*
* Checks whether key is allowed in file.
* returns 1 if the key is allowed or 0 otherwise.
*/
static int
user_key_allowed2(struct ssh *ssh, struct passwd *pw, struct sshkey *key,
char *file, struct sshauthopt **authoptsp)
{
FILE *f;
int found_key = 0;
if (authoptsp != NULL)
*authoptsp = NULL;
/* Temporarily use the user's uid. */
temporarily_use_uid(pw);
debug("trying public key file %s", file);
if ((f = auth_openkeyfile(file, pw, options.strict_modes)) != NULL) {
found_key = check_authkeys_file(ssh, pw, f, file,
key, authoptsp);
fclose(f);
}
restore_uid();
return found_key;
}
/*
* Checks whether key is allowed in output of command.
* returns 1 if the key is allowed or 0 otherwise.
*/
static int
user_key_command_allowed2(struct ssh *ssh, struct passwd *user_pw,
struct sshkey *key, struct sshauthopt **authoptsp)
{
struct passwd *runas_pw = NULL;
FILE *f = NULL;
int r, ok, found_key = 0;
int i, uid_swapped = 0, ac = 0;
pid_t pid;
char *username = NULL, *key_fp = NULL, *keytext = NULL;
char uidstr[32], *tmp, *command = NULL, **av = NULL;
void (*osigchld)(int);
if (authoptsp != NULL)
*authoptsp = NULL;
if (options.authorized_keys_command == NULL)
return 0;
if (options.authorized_keys_command_user == NULL) {
error("No user for AuthorizedKeysCommand specified, skipping");
return 0;
}
/*
* NB. all returns later this function should go via "out" to
* ensure the original SIGCHLD handler is restored properly.
*/
osigchld = signal(SIGCHLD, SIG_DFL);
/* Prepare and verify the user for the command */
username = percent_expand(options.authorized_keys_command_user,
"u", user_pw->pw_name, (char *)NULL);
runas_pw = getpwnam(username);
if (runas_pw == NULL) {
error("AuthorizedKeysCommandUser \"%s\" not found: %s",
username, strerror(errno));
goto out;
}
/* Prepare AuthorizedKeysCommand */
if ((key_fp = sshkey_fingerprint(key, options.fingerprint_hash,
SSH_FP_DEFAULT)) == NULL) {
error("%s: sshkey_fingerprint failed", __func__);
goto out;
}
if ((r = sshkey_to_base64(key, &keytext)) != 0) {
error("%s: sshkey_to_base64 failed: %s", __func__, ssh_err(r));
goto out;
}
/* Turn the command into an argument vector */
if (argv_split(options.authorized_keys_command, &ac, &av) != 0) {
error("AuthorizedKeysCommand \"%s\" contains invalid quotes",
command);
goto out;
}
if (ac == 0) {
error("AuthorizedKeysCommand \"%s\" yielded no arguments",
command);
goto out;
}
snprintf(uidstr, sizeof(uidstr), "%llu",
(unsigned long long)user_pw->pw_uid);
for (i = 1; i < ac; i++) {
tmp = percent_expand(av[i],
"U", uidstr,
"u", user_pw->pw_name,
"h", user_pw->pw_dir,
"t", sshkey_ssh_name(key),
"f", key_fp,
"k", keytext,
(char *)NULL);
if (tmp == NULL)
fatal("%s: percent_expand failed", __func__);
free(av[i]);
av[i] = tmp;
}
/* Prepare a printable command for logs, etc. */
command = argv_assemble(ac, av);
/*
* If AuthorizedKeysCommand was run without arguments
* then fall back to the old behaviour of passing the
* target username as a single argument.
*/
if (ac == 1) {
av = xreallocarray(av, ac + 2, sizeof(*av));
av[1] = xstrdup(user_pw->pw_name);
av[2] = NULL;
/* Fix up command too, since it is used in log messages */
free(command);
xasprintf(&command, "%s %s", av[0], av[1]);
}
if ((pid = subprocess("AuthorizedKeysCommand", runas_pw, command,
ac, av, &f,
SSH_SUBPROCESS_STDOUT_CAPTURE|SSH_SUBPROCESS_STDERR_DISCARD)) == 0)
goto out;
uid_swapped = 1;
temporarily_use_uid(runas_pw);
ok = check_authkeys_file(ssh, user_pw, f,
options.authorized_keys_command, key, authoptsp);
fclose(f);
f = NULL;
if (exited_cleanly(pid, "AuthorizedKeysCommand", command, 0) != 0)
goto out;
/* Read completed successfully */
found_key = ok;
out:
if (f != NULL)
fclose(f);
signal(SIGCHLD, osigchld);
for (i = 0; i < ac; i++)
free(av[i]);
free(av);