1/* $OpenBSD: auth-krb5.c,v 1.24 2021/04/03 06:18:40 djm Exp $ */
2/*
3 *    Kerberos v5 authentication and ticket-passing routines.
4 *
5 * From: FreeBSD: src/crypto/openssh/auth-krb5.c,v 1.6 2001/02/13 16:58:04 assar
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 "packet.h"
40#include "log.h"
41#include "sshbuf.h"
42#include "sshkey.h"
43#include "misc.h"
44#include "servconf.h"
45#include "uidswap.h"
46#include "hostfile.h"
47#include "auth.h"
48
49#ifdef KRB5
50#include <errno.h>
51#include <unistd.h>
52#include <string.h>
53#include <krb5.h>
54
55extern ServerOptions	 options;
56
57static int
58krb5_init(void *context)
59{
60	Authctxt *authctxt = (Authctxt *)context;
61	krb5_error_code problem;
62
63	if (authctxt->krb5_ctx == NULL) {
64		problem = krb5_init_context(&authctxt->krb5_ctx);
65		if (problem)
66			return (problem);
67	}
68	return (0);
69}
70
71int
72auth_krb5_password(Authctxt *authctxt, const char *password)
73{
74#ifndef HEIMDAL
75	krb5_creds creds;
76	krb5_principal server;
77#endif
78	krb5_error_code problem;
79	krb5_ccache ccache = NULL;
80	int len;
81	char *client, *platform_client;
82	const char *errmsg;
83
84	/* get platform-specific kerberos client principal name (if it exists) */
85	platform_client = platform_krb5_get_principal_name(authctxt->pw->pw_name);
86	client = platform_client ? platform_client : authctxt->pw->pw_name;
87
88	temporarily_use_uid(authctxt->pw);
89
90	problem = krb5_init(authctxt);
91	if (problem)
92		goto out;
93
94	problem = krb5_parse_name(authctxt->krb5_ctx, client,
95		    &authctxt->krb5_user);
96	if (problem)
97		goto out;
98
99#ifdef HEIMDAL
100# ifdef HAVE_KRB5_CC_NEW_UNIQUE
101	problem = krb5_cc_new_unique(authctxt->krb5_ctx,
102	    krb5_mcc_ops.prefix, NULL, &ccache);
103# else
104	problem = krb5_cc_gen_new(authctxt->krb5_ctx, &krb5_mcc_ops, &ccache);
105# endif
106	if (problem)
107		goto out;
108
109	problem = krb5_cc_initialize(authctxt->krb5_ctx, ccache,
110		authctxt->krb5_user);
111	if (problem)
112		goto out;
113
114	restore_uid();
115
116	problem = krb5_verify_user(authctxt->krb5_ctx, authctxt->krb5_user,
117	    ccache, password, 1, NULL);
118
119	temporarily_use_uid(authctxt->pw);
120
121	if (problem)
122		goto out;
123
124# ifdef HAVE_KRB5_CC_NEW_UNIQUE
125	problem = krb5_cc_new_unique(authctxt->krb5_ctx,
126	    krb5_fcc_ops.prefix, NULL, &authctxt->krb5_fwd_ccache);
127# else
128	problem = krb5_cc_gen_new(authctxt->krb5_ctx, &krb5_fcc_ops,
129	    &authctxt->krb5_fwd_ccache);
130# endif
131	if (problem)
132		goto out;
133
134	problem = krb5_cc_copy_cache(authctxt->krb5_ctx, ccache,
135	    authctxt->krb5_fwd_ccache);
136	krb5_cc_destroy(authctxt->krb5_ctx, ccache);
137	ccache = NULL;
138	if (problem)
139		goto out;
140
141#else
142	problem = krb5_get_init_creds_password(authctxt->krb5_ctx, &creds,
143	    authctxt->krb5_user, (char *)password, NULL, NULL, 0, NULL, NULL);
144	if (problem)
145		goto out;
146
147	problem = krb5_sname_to_principal(authctxt->krb5_ctx, NULL, NULL,
148	    KRB5_NT_SRV_HST, &server);
149	if (problem)
150		goto out;
151
152	restore_uid();
153	problem = krb5_verify_init_creds(authctxt->krb5_ctx, &creds, server,
154	    NULL, NULL, NULL);
155	krb5_free_principal(authctxt->krb5_ctx, server);
156	temporarily_use_uid(authctxt->pw);
157	if (problem)
158		goto out;
159
160	if (!krb5_kuserok(authctxt->krb5_ctx, authctxt->krb5_user,
161	    authctxt->pw->pw_name)) {
162		problem = -1;
163		goto out;
164	}
165
166	problem = ssh_krb5_cc_gen(authctxt->krb5_ctx,
167	    &authctxt->krb5_fwd_ccache);
168	if (problem)
169		goto out;
170
171	problem = krb5_cc_initialize(authctxt->krb5_ctx,
172	    authctxt->krb5_fwd_ccache, authctxt->krb5_user);
173	if (problem)
174		goto out;
175
176	problem = krb5_cc_store_cred(authctxt->krb5_ctx,
177	    authctxt->krb5_fwd_ccache, &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