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1 | /* $OpenBSD: gss-serv-krb5.c,v 1.7 2006/08/03 03:34:42 deraadt Exp $ */ | |
2 | ||
3 | /* | |
4 | * Copyright (c) 2001-2007 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 "servconf.h" | |
43 | ||
44 | #include "buffer.h" | |
45 | #include "ssh-gss.h" | |
46 | ||
47 | extern ServerOptions options; | |
48 | ||
49 | #ifdef HEIMDAL | |
50 | # include <krb5.h> | |
51 | #elif !defined(MECHGLUE) | |
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 | #endif | |
58 | ||
59 | static krb5_context krb_context = NULL; | |
60 | static int ssh_gssapi_krb5_init(); | |
61 | static int ssh_gssapi_krb5_userok(ssh_gssapi_client *client, char *name); | |
62 | static int ssh_gssapi_krb5_localname(ssh_gssapi_client *client, char **user); | |
63 | static void ssh_gssapi_krb5_storecreds(ssh_gssapi_client *client); | |
64 | ||
65 | ssh_gssapi_mech gssapi_kerberos_mech = { | |
66 | "toWM5Slw5Ew8Mqkay+al2g==", | |
67 | "Kerberos", | |
68 | {9, "\x2A\x86\x48\x86\xF7\x12\x01\x02\x02"}, | |
69 | NULL, | |
70 | &ssh_gssapi_krb5_userok, | |
71 | &ssh_gssapi_krb5_localname, | |
72 | &ssh_gssapi_krb5_storecreds, | |
73 | &ssh_gssapi_krb5_updatecreds | |
74 | }; | |
75 | ||
76 | /* Initialise the krb5 library, for the stuff that GSSAPI won't do */ | |
77 | ||
78 | static int | |
79 | ssh_gssapi_krb5_init(void) | |
80 | { | |
81 | krb5_error_code problem; | |
82 | ||
83 | if (krb_context != NULL) | |
84 | return 1; | |
85 | ||
86 | problem = krb5_init_context(&krb_context); | |
87 | if (problem) { | |
88 | logit("Cannot initialize krb5 context"); | |
89 | return 0; | |
90 | } | |
91 | ||
92 | return 1; | |
93 | } | |
94 | ||
95 | /* Check if this user is OK to login. This only works with krb5 - other | |
96 | * GSSAPI mechanisms will need their own. | |
97 | * Returns true if the user is OK to log in, otherwise returns 0 | |
98 | */ | |
99 | ||
100 | static int | |
101 | ssh_gssapi_krb5_userok(ssh_gssapi_client *client, char *name) | |
102 | { | |
103 | krb5_principal princ; | |
104 | int retval; | |
105 | ||
106 | if (ssh_gssapi_krb5_init() == 0) | |
107 | return 0; | |
108 | ||
109 | if ((retval = krb5_parse_name(krb_context, client->exportedname.value, | |
110 | &princ))) { | |
111 | logit("krb5_parse_name(): %.100s", | |
112 | krb5_get_err_text(krb_context, retval)); | |
113 | return 0; | |
114 | } | |
115 | if (krb5_kuserok(krb_context, princ, name)) { | |
116 | retval = 1; | |
117 | logit("Authorized to %s, krb5 principal %s (krb5_kuserok)", | |
118 | name, (char *)client->displayname.value); | |
119 | } else | |
120 | retval = 0; | |
121 | ||
122 | krb5_free_principal(krb_context, princ); | |
123 | return retval; | |
124 | } | |
125 | ||
126 | ||
127 | /* Retrieve the local username associated with a set of Kerberos | |
128 | * credentials. Hopefully we can use this for the 'empty' username | |
129 | * logins discussed in the draft */ | |
130 | static int | |
131 | ssh_gssapi_krb5_localname(ssh_gssapi_client *client, char **user) { | |
132 | krb5_principal princ; | |
133 | int retval; | |
134 | ||
135 | if (ssh_gssapi_krb5_init() == 0) | |
136 | return 0; | |
137 | ||
138 | if ((retval=krb5_parse_name(krb_context, client->displayname.value, | |
139 | &princ))) { | |
140 | logit("krb5_parse_name(): %.100s", | |
141 | krb5_get_err_text(krb_context,retval)); | |
142 | return 0; | |
143 | } | |
144 | ||
145 | /* We've got to return a malloc'd string */ | |
146 | *user = (char *)xmalloc(256); | |
147 | if (krb5_aname_to_localname(krb_context, princ, 256, *user)) { | |
148 | xfree(*user); | |
149 | *user = NULL; | |
150 | return(0); | |
151 | } | |
152 | ||
153 | return(1); | |
154 | } | |
155 | ||
156 | /* This writes out any forwarded credentials from the structure populated | |
157 | * during userauth. Called after we have setuid to the user */ | |
158 | ||
159 | static void | |
160 | ssh_gssapi_krb5_storecreds(ssh_gssapi_client *client) | |
161 | { | |
162 | krb5_ccache ccache; | |
163 | krb5_error_code problem; | |
164 | krb5_principal princ; | |
165 | OM_uint32 maj_status, min_status; | |
166 | gss_cred_id_t krb5_cred_handle; | |
167 | int len; | |
168 | const char *new_ccname; | |
169 | ||
170 | if (client->creds == NULL) { | |
171 | debug("No credentials stored"); | |
172 | return; | |
173 | } | |
174 | ||
175 | if (ssh_gssapi_krb5_init() == 0) | |
176 | return; | |
177 | ||
178 | #ifdef HEIMDAL | |
179 | if ((problem = krb5_cc_gen_new(krb_context, &krb5_fcc_ops, &ccache))) { | |
180 | logit("krb5_cc_gen_new(): %.100s", | |
181 | krb5_get_err_text(krb_context, problem)); | |
182 | return; | |
183 | } | |
184 | #else | |
185 | if ((problem = ssh_krb5_cc_gen(krb_context, &ccache))) { | |
186 | logit("ssh_krb5_cc_gen(): %.100s", | |
187 | krb5_get_err_text(krb_context, problem)); | |
188 | return; | |
189 | } | |
190 | #endif /* #ifdef HEIMDAL */ | |
191 | ||
192 | if ((problem = krb5_parse_name(krb_context, | |
193 | client->exportedname.value, &princ))) { | |
194 | logit("krb5_parse_name(): %.100s", | |
195 | krb5_get_err_text(krb_context, problem)); | |
196 | krb5_cc_destroy(krb_context, ccache); | |
197 | return; | |
198 | } | |
199 | ||
200 | if ((problem = krb5_cc_initialize(krb_context, ccache, princ))) { | |
201 | logit("krb5_cc_initialize(): %.100s", | |
202 | krb5_get_err_text(krb_context, problem)); | |
203 | krb5_free_principal(krb_context, princ); | |
204 | krb5_cc_destroy(krb_context, ccache); | |
205 | return; | |
206 | } | |
207 | ||
208 | krb5_free_principal(krb_context, princ); | |
209 | ||
210 | #ifdef MECHGLUE | |
211 | krb5_cred_handle = | |
212 | __gss_get_mechanism_cred(client->creds, | |
213 | &(gssapi_kerberos_mech.oid)); | |
214 | #else | |
215 | krb5_cred_handle = client->creds; | |
216 | #endif | |
217 | ||
218 | if ((maj_status = gss_krb5_copy_ccache(&min_status, | |
219 | krb5_cred_handle, ccache))) { | |
220 | logit("gss_krb5_copy_ccache() failed"); | |
221 | krb5_cc_destroy(krb_context, ccache); | |
222 | return; | |
223 | } | |
224 | ||
225 | new_ccname = krb5_cc_get_name(krb_context, ccache); | |
226 | ||
227 | client->store.envvar = "KRB5CCNAME"; | |
228 | #ifdef USE_CCAPI | |
229 | xasprintf(&client->store.envval, "API:%s", new_ccname); | |
230 | client->store.filename = NULL; | |
231 | #else | |
232 | xasprintf(&client->store.envval, "FILE:%s", new_ccname); | |
233 | client->store.filename = xstrdup(new_ccname); | |
234 | #endif | |
235 | ||
236 | #ifdef USE_PAM | |
237 | if (options.use_pam) | |
238 | do_pam_putenv(client->store.envvar, client->store.envval); | |
239 | #endif | |
240 | ||
241 | krb5_cc_close(krb_context, ccache); | |
242 | ||
243 | return; | |
244 | } | |
245 | ||
246 | int | |
247 | ssh_gssapi_krb5_updatecreds(ssh_gssapi_ccache *store, | |
248 | ssh_gssapi_client *client) | |
249 | { | |
250 | krb5_ccache ccache = NULL; | |
251 | krb5_principal principal = NULL; | |
252 | char *name = NULL; | |
253 | krb5_error_code problem; | |
254 | OM_uint32 maj_status, min_status; | |
255 | ||
256 | if ((problem = krb5_cc_resolve(krb_context, store->envval, &ccache))) { | |
257 | logit("krb5_cc_resolve(): %.100s", | |
258 | krb5_get_err_text(krb_context, problem)); | |
259 | return 0; | |
260 | } | |
261 | ||
262 | /* Find out who the principal in this cache is */ | |
263 | if ((problem = krb5_cc_get_principal(krb_context, ccache, | |
264 | &principal))) { | |
265 | logit("krb5_cc_get_principal(): %.100s", | |
266 | krb5_get_err_text(krb_context, problem)); | |
267 | krb5_cc_close(krb_context, ccache); | |
268 | return 0; | |
269 | } | |
270 | ||
271 | if ((problem = krb5_unparse_name(krb_context, principal, &name))) { | |
272 | logit("krb5_unparse_name(): %.100s", | |
273 | krb5_get_err_text(krb_context, problem)); | |
274 | krb5_free_principal(krb_context, principal); | |
275 | krb5_cc_close(krb_context, ccache); | |
276 | return 0; | |
277 | } | |
278 | ||
279 | ||
280 | if (strcmp(name,client->exportedname.value)!=0) { | |
281 | debug("Name in local credentials cache differs. Not storing"); | |
282 | krb5_free_principal(krb_context, principal); | |
283 | krb5_cc_close(krb_context, ccache); | |
284 | krb5_free_unparsed_name(krb_context, name); | |
285 | return 0; | |
286 | } | |
287 | krb5_free_unparsed_name(krb_context, name); | |
288 | ||
289 | /* Name matches, so lets get on with it! */ | |
290 | ||
291 | if ((problem = krb5_cc_initialize(krb_context, ccache, principal))) { | |
292 | logit("krb5_cc_initialize(): %.100s", | |
293 | krb5_get_err_text(krb_context, problem)); | |
294 | krb5_free_principal(krb_context, principal); | |
295 | krb5_cc_close(krb_context, ccache); | |
296 | return 0; | |
297 | } | |
298 | ||
299 | krb5_free_principal(krb_context, principal); | |
300 | ||
301 | if ((maj_status = gss_krb5_copy_ccache(&min_status, client->creds, | |
302 | ccache))) { | |
303 | logit("gss_krb5_copy_ccache() failed. Sorry!"); | |
304 | krb5_cc_close(krb_context, ccache); | |
305 | return 0; | |
306 | } | |
307 | ||
308 | return 1; | |
309 | } | |
310 | ||
311 | #endif /* KRB5 */ | |
312 | ||
313 | #endif /* GSSAPI */ |