xref: /openssh-portable/gss-serv-krb5.c (revision b8d9214d)
1 /* $OpenBSD: gss-serv-krb5.c,v 1.9 2018/07/09 21:37:55 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 <sys/types.h>
33 
34 #include <stdarg.h>
35 #include <string.h>
36 
37 #include "xmalloc.h"
38 #include "sshkey.h"
39 #include "hostfile.h"
40 #include "auth.h"
41 #include "log.h"
42 #include "misc.h"
43 #include "servconf.h"
44 
45 #include "ssh-gss.h"
46 
47 extern ServerOptions options;
48 
49 #ifdef HEIMDAL
50 # include <krb5.h>
51 #endif
52 #ifdef HAVE_GSSAPI_KRB5_H
53 # include <gssapi_krb5.h>
54 #elif HAVE_GSSAPI_GSSAPI_KRB5_H
55 # include <gssapi/gssapi_krb5.h>
56 #endif
57 
58 static krb5_context krb_context = NULL;
59 
60 /* Initialise the krb5 library, for the stuff that GSSAPI won't do */
61 
62 static int
ssh_gssapi_krb5_init(void)63 ssh_gssapi_krb5_init(void)
64 {
65 	krb5_error_code problem;
66 
67 	if (krb_context != NULL)
68 		return 1;
69 
70 	problem = krb5_init_context(&krb_context);
71 	if (problem) {
72 		logit("Cannot initialize krb5 context");
73 		return 0;
74 	}
75 
76 	return 1;
77 }
78 
79 /* Check if this user is OK to login. This only works with krb5 - other
80  * GSSAPI mechanisms will need their own.
81  * Returns true if the user is OK to log in, otherwise returns 0
82  */
83 
84 static int
ssh_gssapi_krb5_userok(ssh_gssapi_client * client,char * name)85 ssh_gssapi_krb5_userok(ssh_gssapi_client *client, char *name)
86 {
87 	krb5_principal princ;
88 	int retval;
89 	const char *errmsg;
90 
91 	if (ssh_gssapi_krb5_init() == 0)
92 		return 0;
93 
94 	if ((retval = krb5_parse_name(krb_context, client->exportedname.value,
95 	    &princ))) {
96 		errmsg = krb5_get_error_message(krb_context, retval);
97 		logit("krb5_parse_name(): %.100s", errmsg);
98 		krb5_free_error_message(krb_context, errmsg);
99 		return 0;
100 	}
101 	if (krb5_kuserok(krb_context, princ, name)) {
102 		retval = 1;
103 		logit("Authorized to %s, krb5 principal %s (krb5_kuserok)",
104 		    name, (char *)client->displayname.value);
105 	} else
106 		retval = 0;
107 
108 	krb5_free_principal(krb_context, princ);
109 	return retval;
110 }
111 
112 
113 /* This writes out any forwarded credentials from the structure populated
114  * during userauth. Called after we have setuid to the user */
115 
116 static void
ssh_gssapi_krb5_storecreds(ssh_gssapi_client * client)117 ssh_gssapi_krb5_storecreds(ssh_gssapi_client *client)
118 {
119 	krb5_ccache ccache;
120 	krb5_error_code problem;
121 	krb5_principal princ;
122 	OM_uint32 maj_status, min_status;
123 	int len;
124 	const char *errmsg;
125 
126 	if (client->creds == NULL) {
127 		debug("No credentials stored");
128 		return;
129 	}
130 
131 	if (ssh_gssapi_krb5_init() == 0)
132 		return;
133 
134 #ifdef HEIMDAL
135 # ifdef HAVE_KRB5_CC_NEW_UNIQUE
136 	if ((problem = krb5_cc_new_unique(krb_context, krb5_fcc_ops.prefix,
137 	    NULL, &ccache)) != 0) {
138 		errmsg = krb5_get_error_message(krb_context, problem);
139 		logit("krb5_cc_new_unique(): %.100s", errmsg);
140 # else
141 	if ((problem = krb5_cc_gen_new(krb_context, &krb5_fcc_ops, &ccache))) {
142 	    logit("krb5_cc_gen_new(): %.100s",
143 		krb5_get_err_text(krb_context, problem));
144 # endif
145 		krb5_free_error_message(krb_context, errmsg);
146 		return;
147 	}
148 #else
149 	if ((problem = ssh_krb5_cc_gen(krb_context, &ccache))) {
150 		errmsg = krb5_get_error_message(krb_context, problem);
151 		logit("ssh_krb5_cc_gen(): %.100s", errmsg);
152 		krb5_free_error_message(krb_context, errmsg);
153 		return;
154 	}
155 #endif	/* #ifdef HEIMDAL */
156 
157 	if ((problem = krb5_parse_name(krb_context,
158 	    client->exportedname.value, &princ))) {
159 		errmsg = krb5_get_error_message(krb_context, problem);
160 		logit("krb5_parse_name(): %.100s", errmsg);
161 		krb5_free_error_message(krb_context, errmsg);
162 		return;
163 	}
164 
165 	if ((problem = krb5_cc_initialize(krb_context, ccache, princ))) {
166 		errmsg = krb5_get_error_message(krb_context, problem);
167 		logit("krb5_cc_initialize(): %.100s", errmsg);
168 		krb5_free_error_message(krb_context, errmsg);
169 		krb5_free_principal(krb_context, princ);
170 		krb5_cc_destroy(krb_context, ccache);
171 		return;
172 	}
173 
174 	krb5_free_principal(krb_context, princ);
175 
176 	if ((maj_status = gss_krb5_copy_ccache(&min_status,
177 	    client->creds, ccache))) {
178 		logit("gss_krb5_copy_ccache() failed");
179 		krb5_cc_destroy(krb_context, ccache);
180 		return;
181 	}
182 
183 	client->store.filename = xstrdup(krb5_cc_get_name(krb_context, ccache));
184 	client->store.envvar = "KRB5CCNAME";
185 	len = strlen(client->store.filename) + 6;
186 	client->store.envval = xmalloc(len);
187 	snprintf(client->store.envval, len, "FILE:%s", client->store.filename);
188 
189 #ifdef USE_PAM
190 	if (options.use_pam)
191 		do_pam_putenv(client->store.envvar, client->store.envval);
192 #endif
193 
194 	krb5_cc_close(krb_context, ccache);
195 
196 	return;
197 }
198 
199 ssh_gssapi_mech gssapi_kerberos_mech = {
200 	"toWM5Slw5Ew8Mqkay+al2g==",
201 	"Kerberos",
202 	{9, "\x2A\x86\x48\x86\xF7\x12\x01\x02\x02"},
203 	NULL,
204 	&ssh_gssapi_krb5_userok,
205 	NULL,
206 	&ssh_gssapi_krb5_storecreds
207 };
208 
209 #endif /* KRB5 */
210 
211 #endif /* GSSAPI */
212