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1 /* $OpenBSD: gss-serv-krb5.c,v 1.8 2013/07/20 01:55:13 djm 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 <sys/types.h>
33 
34 #include <stdarg.h>
35 #include <string.h>
36 
37 #include "xmalloc.h"
38 #include "key.h"
39 #include "hostfile.h"
40 #include "auth.h"
41 #include "log.h"
42 #include "misc.h"
43 #include "servconf.h"
44 
45 #include "buffer.h"
46 #include "ssh-gss.h"
47 
48 extern ServerOptions options;
49 
50 #ifdef HEIMDAL
51 # include <krb5.h>
52 #endif
53 #ifdef HAVE_GSSAPI_KRB5_H
54 # include <gssapi_krb5.h>
55 #elif HAVE_GSSAPI_GSSAPI_KRB5_H
56 # include <gssapi/gssapi_krb5.h>
57 #endif
58 
59 static krb5_context krb_context = NULL;
60 
61 /* Initialise the krb5 library, for the stuff that GSSAPI won't do */
62 
63 static int
ssh_gssapi_krb5_init(void)64 ssh_gssapi_krb5_init(void)
65 {
66 	krb5_error_code problem;
67 
68 	if (krb_context != NULL)
69 		return 1;
70 
71 	problem = krb5_init_context(&krb_context);
72 	if (problem) {
73 		logit("Cannot initialize krb5 context");
74 		return 0;
75 	}
76 
77 	return 1;
78 }
79 
80 /* Check if this user is OK to login. This only works with krb5 - other
81  * GSSAPI mechanisms will need their own.
82  * Returns true if the user is OK to log in, otherwise returns 0
83  */
84 
85 static int
ssh_gssapi_krb5_userok(ssh_gssapi_client * client,char * name)86 ssh_gssapi_krb5_userok(ssh_gssapi_client *client, char *name)
87 {
88 	krb5_principal princ;
89 	int retval;
90 	const char *errmsg;
91 
92 	if (ssh_gssapi_krb5_init() == 0)
93 		return 0;
94 
95 	if ((retval = krb5_parse_name(krb_context, client->exportedname.value,
96 	    &princ))) {
97 		errmsg = krb5_get_error_message(krb_context, retval);
98 		logit("krb5_parse_name(): %.100s", errmsg);
99 		krb5_free_error_message(krb_context, errmsg);
100 		return 0;
101 	}
102 	if (krb5_kuserok(krb_context, princ, name)) {
103 		retval = 1;
104 		logit("Authorized to %s, krb5 principal %s (krb5_kuserok)",
105 		    name, (char *)client->displayname.value);
106 	} else
107 		retval = 0;
108 
109 	krb5_free_principal(krb_context, princ);
110 	return retval;
111 }
112 
113 
114 /* This writes out any forwarded credentials from the structure populated
115  * during userauth. Called after we have setuid to the user */
116 
117 static void
ssh_gssapi_krb5_storecreds(ssh_gssapi_client * client)118 ssh_gssapi_krb5_storecreds(ssh_gssapi_client *client)
119 {
120 	krb5_ccache ccache;
121 	krb5_error_code problem;
122 	krb5_principal princ;
123 	OM_uint32 maj_status, min_status;
124 	int len;
125 	const char *errmsg;
126 
127 	if (client->creds == NULL) {
128 		debug("No credentials stored");
129 		return;
130 	}
131 
132 	if (ssh_gssapi_krb5_init() == 0)
133 		return;
134 
135 #ifdef HEIMDAL
136 # ifdef HAVE_KRB5_CC_NEW_UNIQUE
137 	if ((problem = krb5_cc_new_unique(krb_context, krb5_fcc_ops.prefix,
138 	    NULL, &ccache)) != 0) {
139 		errmsg = krb5_get_error_message(krb_context, problem);
140 		logit("krb5_cc_new_unique(): %.100s", errmsg);
141 # else
142 	if ((problem = krb5_cc_gen_new(krb_context, &krb5_fcc_ops, &ccache))) {
143 	    logit("krb5_cc_gen_new(): %.100s",
144 		krb5_get_err_text(krb_context, problem));
145 # endif
146 		krb5_free_error_message(krb_context, errmsg);
147 		return;
148 	}
149 #else
150 	if ((problem = ssh_krb5_cc_gen(krb_context, &ccache))) {
151 		errmsg = krb5_get_error_message(krb_context, problem);
152 		logit("ssh_krb5_cc_gen(): %.100s", errmsg);
153 		krb5_free_error_message(krb_context, errmsg);
154 		return;
155 	}
156 #endif	/* #ifdef HEIMDAL */
157 
158 	if ((problem = krb5_parse_name(krb_context,
159 	    client->exportedname.value, &princ))) {
160 		errmsg = krb5_get_error_message(krb_context, problem);
161 		logit("krb5_parse_name(): %.100s", errmsg);
162 		krb5_free_error_message(krb_context, errmsg);
163 		return;
164 	}
165 
166 	if ((problem = krb5_cc_initialize(krb_context, ccache, princ))) {
167 		errmsg = krb5_get_error_message(krb_context, problem);
168 		logit("krb5_cc_initialize(): %.100s", errmsg);
169 		krb5_free_error_message(krb_context, errmsg);
170 		krb5_free_principal(krb_context, princ);
171 		krb5_cc_destroy(krb_context, ccache);
172 		return;
173 	}
174 
175 	krb5_free_principal(krb_context, princ);
176 
177 	if ((maj_status = gss_krb5_copy_ccache(&min_status,
178 	    client->creds, ccache))) {
179 		logit("gss_krb5_copy_ccache() failed");
180 		krb5_cc_destroy(krb_context, ccache);
181 		return;
182 	}
183 
184 	client->store.filename = xstrdup(krb5_cc_get_name(krb_context, ccache));
185 	client->store.envvar = "KRB5CCNAME";
186 	len = strlen(client->store.filename) + 6;
187 	client->store.envval = xmalloc(len);
188 	snprintf(client->store.envval, len, "FILE:%s", client->store.filename);
189 
190 #ifdef USE_PAM
191 	if (options.use_pam)
192 		do_pam_putenv(client->store.envvar, client->store.envval);
193 #endif
194 
195 	krb5_cc_close(krb_context, ccache);
196 
197 	return;
198 }
199 
200 ssh_gssapi_mech gssapi_kerberos_mech = {
201 	"toWM5Slw5Ew8Mqkay+al2g==",
202 	"Kerberos",
203 	{9, "\x2A\x86\x48\x86\xF7\x12\x01\x02\x02"},
204 	NULL,
205 	&ssh_gssapi_krb5_userok,
206 	NULL,
207 	&ssh_gssapi_krb5_storecreds
208 };
209 
210 #endif /* KRB5 */
211 
212 #endif /* GSSAPI */
213