gss-serv-krb5.c revision 124208 
1/*	$OpenBSD: gss-serv-krb5.c,v 1.1 2003/08/22 10:56:09 markus Exp $	*/
2
3/*
4 * Copyright (c) 2001-2003 Simon Wilkinson. All rights reserved.
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
8 * are met:
9 * 1. Redistributions of source code must retain the above copyright
10 *    notice, this list of conditions and the following disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 *    notice, this list of conditions and the following disclaimer in the
13 *    documentation and/or other materials provided with the distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR `AS IS'' AND ANY EXPRESS OR
16 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
17 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
18 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
19 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
20 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
21 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
22 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
23 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
24 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
25 */
26
27#include "includes.h"
28
29#ifdef GSSAPI
30#ifdef KRB5
31
32#include "auth.h"
33#include "xmalloc.h"
34#include "log.h"
35#include "servconf.h"
36
37#include "ssh-gss.h"
38
39extern ServerOptions options;
40
41#ifdef HEIMDAL
42#include <krb5.h>
43#else
44#include <gssapi_krb5.h>
45#endif
46
47static krb5_context krb_context = NULL;
48
49/* Initialise the krb5 library, for the stuff that GSSAPI won't do */
50
51static int
52ssh_gssapi_krb5_init()
53{
54	krb5_error_code problem;
55
56	if (krb_context != NULL)
57		return 1;
58
59	problem = krb5_init_context(&krb_context);
60	if (problem) {
61		logit("Cannot initialize krb5 context");
62		return 0;
63	}
64	krb5_init_ets(krb_context);
65
66	return 1;
67}
68
69/* Check if this user is OK to login. This only works with krb5 - other
70 * GSSAPI mechanisms will need their own.
71 * Returns true if the user is OK to log in, otherwise returns 0
72 */
73
74static int
75ssh_gssapi_krb5_userok(ssh_gssapi_client *client, char *name)
76{
77	krb5_principal princ;
78	int retval;
79
80	if (ssh_gssapi_krb5_init() == 0)
81		return 0;
82
83	if ((retval = krb5_parse_name(krb_context, client->exportedname.value,
84	    &princ))) {
85		logit("krb5_parse_name(): %.100s",
86		    krb5_get_err_text(krb_context, retval));
87		return 0;
88	}
89	if (krb5_kuserok(krb_context, princ, name)) {
90		retval = 1;
91		logit("Authorized to %s, krb5 principal %s (krb5_kuserok)",
92		    name, (char *)client->displayname.value);
93	} else
94		retval = 0;
95
96	krb5_free_principal(krb_context, princ);
97	return retval;
98}
99
100
101/* This writes out any forwarded credentials from the structure populated
102 * during userauth. Called after we have setuid to the user */
103
104static void
105ssh_gssapi_krb5_storecreds(ssh_gssapi_client *client)
106{
107	krb5_ccache ccache;
108	krb5_error_code problem;
109	krb5_principal princ;
110	OM_uint32 maj_status, min_status;
111
112	if (client->creds == NULL) {
113		debug("No credentials stored");
114		return;
115	}
116
117	if (ssh_gssapi_krb5_init() == 0)
118		return;
119
120#ifdef HEIMDAL
121	if ((problem = krb5_cc_gen_new(krb_context, &krb5_fcc_ops, &ccache))) {
122		logit("krb5_cc_gen_new(): %.100s",
123		    krb5_get_err_text(krb_context, problem));
124		return;
125	}
126#else
127	{
128		int tmpfd;
129		char ccname[40];
130
131		snprintf(ccname, sizeof(ccname),
132		    "FILE:/tmp/krb5cc_%d_XXXXXX", geteuid());
133
134		if ((tmpfd = mkstemp(ccname + strlen("FILE:"))) == -1) {
135			logit("mkstemp(): %.100s", strerror(errno));
136			problem = errno;
137			return;
138		}
139		if (fchmod(tmpfd, S_IRUSR | S_IWUSR) == -1) {
140			logit("fchmod(): %.100s", strerror(errno));
141			close(tmpfd);
142			problem = errno;
143			return;
144		}
145		close(tmpfd);
146		if ((problem = krb5_cc_resolve(krb_context, ccname, &ccache))) {
147			logit("krb5_cc_resolve(): %.100s",
148			    krb5_get_err_text(krb_context, problem));
149			return;
150		}
151	}
152#endif	/* #ifdef HEIMDAL */
153
154	if ((problem = krb5_parse_name(krb_context,
155	    client->exportedname.value, &princ))) {
156		logit("krb5_parse_name(): %.100s",
157		    krb5_get_err_text(krb_context, problem));
158		krb5_cc_destroy(krb_context, ccache);
159		return;
160	}
161
162	if ((problem = krb5_cc_initialize(krb_context, ccache, princ))) {
163		logit("krb5_cc_initialize(): %.100s",
164		    krb5_get_err_text(krb_context, problem));
165		krb5_free_principal(krb_context, princ);
166		krb5_cc_destroy(krb_context, ccache);
167		return;
168	}
169
170	krb5_free_principal(krb_context, princ);
171
172	if ((maj_status = gss_krb5_copy_ccache(&min_status,
173	    client->creds, ccache))) {
174		logit("gss_krb5_copy_ccache() failed");
175		krb5_cc_destroy(krb_context, ccache);
176		return;
177	}
178
179	client->store.filename = xstrdup(krb5_cc_get_name(krb_context, ccache));
180	client->store.envvar = "KRB5CCNAME";
181	client->store.envval = xstrdup(client->store.filename);
182
183#ifdef USE_PAM
184	if (options.use_pam)
185		do_pam_putenv(client->store.envvar,client->store.envval);
186#endif
187
188	krb5_cc_close(krb_context, ccache);
189
190	return;
191}
192
193ssh_gssapi_mech gssapi_kerberos_mech = {
194	"toWM5Slw5Ew8Mqkay+al2g==",
195	"Kerberos",
196	{9, "\x2A\x86\x48\x86\xF7\x12\x01\x02\x02"},
197	NULL,
198	&ssh_gssapi_krb5_userok,
199	NULL,
200	&ssh_gssapi_krb5_storecreds
201};
202
203#endif /* KRB5 */
204
205#endif /* GSSAPI */
206