auth-krb5.c revision 295367 
1/* $OpenBSD: auth-krb5.c,v 1.20 2013/07/20 01:55:13 djm Exp $ */
2/*
3 *    Kerberos v5 authentication and ticket-passing routines.
4 *
5 * $FreeBSD: src/crypto/openssh/auth-krb5.c,v 1.6 2001/02/13 16:58:04 assar Exp $
6 */
7/*
8 * Copyright (c) 2002 Daniel Kouril.  All rights reserved.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 *    notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 *    notice, this list of conditions and the following disclaimer in the
17 *    documentation and/or other materials provided with the distribution.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
20 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
21 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
22 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
23 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
24 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
25 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
26 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
27 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
28 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
29 */
30
31#include "includes.h"
32
33#include <sys/types.h>
34#include <pwd.h>
35#include <stdarg.h>
36
37#include "xmalloc.h"
38#include "ssh.h"
39#include "ssh1.h"
40#include "packet.h"
41#include "log.h"
42#include "buffer.h"
43#include "misc.h"
44#include "servconf.h"
45#include "uidswap.h"
46#include "key.h"
47#include "hostfile.h"
48#include "auth.h"
49
50#ifdef KRB5
51#include <errno.h>
52#include <unistd.h>
53#include <string.h>
54#include <krb5.h>
55
56extern ServerOptions	 options;
57
58static int
59krb5_init(void *context)
60{
61	Authctxt *authctxt = (Authctxt *)context;
62	krb5_error_code problem;
63
64	if (authctxt->krb5_ctx == NULL) {
65		problem = krb5_init_context(&authctxt->krb5_ctx);
66		if (problem)
67			return (problem);
68	}
69	return (0);
70}
71
72int
73auth_krb5_password(Authctxt *authctxt, const char *password)
74{
75#ifndef HEIMDAL
76	krb5_creds creds;
77	krb5_principal server;
78#endif
79	krb5_error_code problem;
80	krb5_ccache ccache = NULL;
81	int len;
82	char *client, *platform_client;
83	const char *errmsg;
84
85	/* get platform-specific kerberos client principal name (if it exists) */
86	platform_client = platform_krb5_get_principal_name(authctxt->pw->pw_name);
87	client = platform_client ? platform_client : authctxt->pw->pw_name;
88
89	temporarily_use_uid(authctxt->pw);
90
91	problem = krb5_init(authctxt);
92	if (problem)
93		goto out;
94
95	problem = krb5_parse_name(authctxt->krb5_ctx, client,
96		    &authctxt->krb5_user);
97	if (problem)
98		goto out;
99
100#ifdef HEIMDAL
101# ifdef HAVE_KRB5_CC_NEW_UNIQUE
102	problem = krb5_cc_new_unique(authctxt->krb5_ctx,
103	     krb5_mcc_ops.prefix, NULL, &ccache);
104# else
105	problem = krb5_cc_gen_new(authctxt->krb5_ctx, &krb5_mcc_ops, &ccache);
106# endif
107	if (problem)
108		goto out;
109
110	problem = krb5_cc_initialize(authctxt->krb5_ctx, ccache,
111		authctxt->krb5_user);
112	if (problem)
113		goto out;
114
115	restore_uid();
116
117	problem = krb5_verify_user(authctxt->krb5_ctx, authctxt->krb5_user,
118	    ccache, password, 1, NULL);
119
120	temporarily_use_uid(authctxt->pw);
121
122	if (problem)
123		goto out;
124
125# ifdef HAVE_KRB5_CC_NEW_UNIQUE
126	problem = krb5_cc_new_unique(authctxt->krb5_ctx,
127	     krb5_fcc_ops.prefix, NULL, &authctxt->krb5_fwd_ccache);
128# else
129	problem = krb5_cc_gen_new(authctxt->krb5_ctx, &krb5_fcc_ops,
130	    &authctxt->krb5_fwd_ccache);
131# endif
132	if (problem)
133		goto out;
134
135	problem = krb5_cc_copy_cache(authctxt->krb5_ctx, ccache,
136	    authctxt->krb5_fwd_ccache);
137	krb5_cc_destroy(authctxt->krb5_ctx, ccache);
138	ccache = NULL;
139	if (problem)
140		goto out;
141
142#else
143	problem = krb5_get_init_creds_password(authctxt->krb5_ctx, &creds,
144	    authctxt->krb5_user, (char *)password, NULL, NULL, 0, NULL, NULL);
145	if (problem)
146		goto out;
147
148	problem = krb5_sname_to_principal(authctxt->krb5_ctx, NULL, NULL,
149	    KRB5_NT_SRV_HST, &server);
150	if (problem)
151		goto out;
152
153	restore_uid();
154	problem = krb5_verify_init_creds(authctxt->krb5_ctx, &creds, server,
155	    NULL, NULL, NULL);
156	krb5_free_principal(authctxt->krb5_ctx, server);
157	temporarily_use_uid(authctxt->pw);
158	if (problem)
159		goto out;
160
161	if (!krb5_kuserok(authctxt->krb5_ctx, authctxt->krb5_user,
162	    authctxt->pw->pw_name)) {
163		problem = -1;
164		goto out;
165	}
166
167	problem = ssh_krb5_cc_gen(authctxt->krb5_ctx, &authctxt->krb5_fwd_ccache);
168	if (problem)
169		goto out;
170
171	problem = krb5_cc_initialize(authctxt->krb5_ctx, authctxt->krb5_fwd_ccache,
172				     authctxt->krb5_user);
173	if (problem)
174		goto out;
175
176	problem= krb5_cc_store_cred(authctxt->krb5_ctx, authctxt->krb5_fwd_ccache,
177				 &creds);
178	if (problem)
179		goto out;
180#endif
181
182	authctxt->krb5_ticket_file = (char *)krb5_cc_get_name(authctxt->krb5_ctx, authctxt->krb5_fwd_ccache);
183
184	len = strlen(authctxt->krb5_ticket_file) + 6;
185	authctxt->krb5_ccname = xmalloc(len);
186	snprintf(authctxt->krb5_ccname, len, "FILE:%s",
187	    authctxt->krb5_ticket_file);
188
189#ifdef USE_PAM
190	if (options.use_pam)
191		do_pam_putenv("KRB5CCNAME", authctxt->krb5_ccname);
192#endif
193
194 out:
195	restore_uid();
196
197	free(platform_client);
198
199	if (problem) {
200		if (ccache)
201			krb5_cc_destroy(authctxt->krb5_ctx, ccache);
202
203		if (authctxt->krb5_ctx != NULL && problem!=-1) {
204			errmsg = krb5_get_error_message(authctxt->krb5_ctx,
205			    problem);
206 			debug("Kerberos password authentication failed: %s",
207			    errmsg);
208			krb5_free_error_message(authctxt->krb5_ctx, errmsg);
209		} else
210			debug("Kerberos password authentication failed: %d",
211			    problem);
212
213		krb5_cleanup_proc(authctxt);
214
215		if (options.kerberos_or_local_passwd)
216			return (-1);
217		else
218			return (0);
219	}
220	return (authctxt->valid ? 1 : 0);
221}
222
223void
224krb5_cleanup_proc(Authctxt *authctxt)
225{
226	debug("krb5_cleanup_proc called");
227	if (authctxt->krb5_fwd_ccache) {
228		krb5_cc_destroy(authctxt->krb5_ctx, authctxt->krb5_fwd_ccache);
229		authctxt->krb5_fwd_ccache = NULL;
230	}
231	if (authctxt->krb5_user) {
232		krb5_free_principal(authctxt->krb5_ctx, authctxt->krb5_user);
233		authctxt->krb5_user = NULL;
234	}
235	if (authctxt->krb5_ctx) {
236		krb5_free_context(authctxt->krb5_ctx);
237		authctxt->krb5_ctx = NULL;
238	}
239}
240
241#ifndef HEIMDAL
242krb5_error_code
243ssh_krb5_cc_gen(krb5_context ctx, krb5_ccache *ccache) {
244	int tmpfd, ret, oerrno;
245	char ccname[40];
246	mode_t old_umask;
247
248	ret = snprintf(ccname, sizeof(ccname),
249	    "FILE:/tmp/krb5cc_%d_XXXXXXXXXX", geteuid());
250	if (ret < 0 || (size_t)ret >= sizeof(ccname))
251		return ENOMEM;
252
253	old_umask = umask(0177);
254	tmpfd = mkstemp(ccname + strlen("FILE:"));
255	oerrno = errno;
256	umask(old_umask);
257	if (tmpfd == -1) {
258		logit("mkstemp(): %.100s", strerror(oerrno));
259		return oerrno;
260	}
261
262	if (fchmod(tmpfd,S_IRUSR | S_IWUSR) == -1) {
263		oerrno = errno;
264		logit("fchmod(): %.100s", strerror(oerrno));
265		close(tmpfd);
266		return oerrno;
267	}
268	close(tmpfd);
269
270	return (krb5_cc_resolve(ctx, ccname, ccache));
271}
272#endif /* !HEIMDAL */
273#endif /* KRB5 */
274