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[utils.git] / pam_krb5auto.c
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1/*
2 * pam_krb5auto - Gets initial credentials non-interactively
3 * Copyright (C) 2004 Fredrik Tolf (fredrik@dolda2000.com)
4 *
5 * This program is free software; you can redistribute it and/or modify
6 * it under the terms of the GNU General Public License as published by
7 * the Free Software Foundation; either version 2 of the License, or
8 * (at your option) any later version.
9 *
10 * This program is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 * GNU General Public License for more details.
14 *
15 * You should have received a copy of the GNU General Public License
16 * along with this program; if not, write to the Free Software
17 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
18*/
dc647f87 19#include <stdlib.h>
2febc19a 20#include <stdio.h>
dc647f87 21#include <unistd.h>
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22#include <string.h>
23#include <stdarg.h>
24#include <malloc.h>
324b1cfb 25#include <syslog.h>
dc647f87 26#include <krb5.h>
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27#include <pwd.h>
28#include <errno.h>
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29
30#define PAM_SM_AUTH
31
32#include <security/pam_modules.h>
33
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34#define DEF_INSTANCE "autologin"
35
36struct options
37{
38 char *realm;
39 char *instance;
40 char *keytab;
41 int debug;
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42 int forwardable;
43 int renewable;
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44};
45
46struct data
47{
48 krb5_context ctx;
49 krb5_ccache cc;
50 krb5_principal me;
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51 krb5_creds initcreds;
52 int hascreds;
53 uid_t uid;
e1427cb7 54 gid_t gid;
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55};
56
57static void log(int prio, char *format, ...)
58{
59 va_list args;
60 char buf[1024];
61
62 va_start(args, format);
63 snprintf(buf, sizeof(buf), "pam_krb5auto[%i]: %s", getpid(), format);
64 vsyslog(prio, buf, args);
65 va_end(args);
66}
67
68static struct options *parseopts(int argc, const char **argv)
69{
70 int i;
71 struct options *opts;
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72 const char *p;
73 int unit;
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74
75 opts = malloc(sizeof(*opts));
76 memset(opts, 0, sizeof(*opts));
77 for(i = 0; i < argc; i++) {
78 if(!strncmp(argv[i], "realm=", 6))
79 opts->realm = strdup(argv[i] + 6);
80 if(!strncmp(argv[i], "instance=", 9))
81 opts->instance = strdup(argv[i] + 9);
82 if(!strncmp(argv[i], "keytab=", 7))
83 opts->keytab = strdup(argv[i] + 7);
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84 if(!strncmp(argv[i], "renew=", 6)) {
85 p = argv[i] + strlen(argv[i]) - 1;
86 unit = 1;
87 if((*p >= 'a') && (*p <= 'z')) {
88 if(*p == 'm')
89 unit = 60;
90 else if(*p == 'h')
91 unit = 3600;
92 else if(*p == 'd')
93 unit = 86400;
94 else
95 unit = 1;
96 }
97 opts->renewable = atoi(argv[i] + 6) * unit;
98 }
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99 if(!strcmp(argv[i], "forwardable"))
100 opts->forwardable = 1;
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101 if(!strcmp(argv[i], "debug"))
102 opts->debug = 1;
103 }
104 return(opts);
105}
106
107static void freeopts(struct options *opts)
108{
109 if(opts->realm != NULL)
110 free(opts->realm);
111 if(opts->instance != NULL)
112 free(opts->instance);
113 if(opts->keytab != NULL)
114 free(opts->keytab);
115 free(opts);
116}
117
118static void freedata(struct data *data)
119{
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120 if(data->hascreds)
121 krb5_free_cred_contents(data->ctx, &data->initcreds);
122 if(data->cc != NULL)
123 krb5_cc_close(data->ctx, data->cc);
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124 if(data->me != NULL)
125 krb5_free_principal(data->ctx, data->me);
126 if(data->ctx != NULL)
127 krb5_free_context(data->ctx);
128 free(data);
129}
130
131static void cleanupdata(pam_handle_t *pamh, struct data *data, int error_status)
132{
133 freedata(data);
134}
135
136static struct data *getdata(pam_handle_t *pamh, struct options *opts)
137{
138 int ret;
139 struct data *data;
140 char buf[1024];
141 const char *user, *instance;
eb2a40de 142 struct passwd *pwent;
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143
144 data = NULL;
145 pam_get_data(pamh, "krb5auto-data", (const void **)&data);
146 if(data == NULL) {
147 if(opts->debug)
148 log(LOG_DEBUG, "creating new instance");
149 data = malloc(sizeof(*data));
150 memset(data, 0, sizeof(*data));
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151 pam_get_user(pamh, &user, NULL);
152 if(user == NULL) {
153 log(LOG_ERR, "could not get user name");
154 freedata(data);
155 return(NULL);
156 }
157 errno = 0;
158 if((pwent = getpwnam(user)) == NULL) {
159 log(LOG_ERR, "could not user information for `%s': %s", user, (errno == 0)?"user not found":strerror(errno));
160 freedata(data);
161 return(NULL);
162 }
163 data->uid = pwent->pw_uid;
e1427cb7 164 data->gid = pwent->pw_gid;
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165 if((ret = krb5_init_context(&data->ctx)) != 0) {
166 log(LOG_CRIT, "could not create krb5 context: %s", error_message(ret));
167 freedata(data);
168 return(NULL);
169 }
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170 if(opts->instance)
171 instance = opts->instance;
172 else
173 instance = DEF_INSTANCE;
174 if(opts->realm)
175 snprintf(buf, sizeof(buf), "%s/%s@%s", user, instance, opts->realm);
176 else
177 snprintf(buf, sizeof(buf), "%s/%s", user, instance);
178 if((ret = krb5_parse_name(data->ctx, buf, &data->me)) != 0) {
179 log(LOG_ERR, "could not parse principal name `%s': %s", buf, error_message(ret));
180 freedata(data);
181 return(NULL);
182 }
183 pam_set_data(pamh, "krb5auto-data", data, (void (*)(pam_handle_t *, void *, int))cleanupdata);
184 }
185 return(data);
186}
187
eb2a40de 188static int savecreds(pam_handle_t *pamh, struct options *opts, struct data *data)
2febc19a 189{
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190 int ret, fd;
191 krb5_keytab kt;
192 krb5_get_init_creds_opt icopts;
193 char buf[1024], *ccname, *filename;
194
195 krb5_get_init_creds_opt_init(&icopts);
196 kt = NULL;
197
198 if(opts->keytab) {
199 if((ret = krb5_kt_resolve(data->ctx, opts->keytab, &kt)) != 0) {
200 log(LOG_ERR, "could not resolve keytab `%s': %s", opts->keytab, error_message(ret));
201 ret = PAM_SERVICE_ERR;
202 goto out;
203 }
204 if(opts->debug)
205 log(LOG_DEBUG, "using keytab `%s'", opts->keytab);
206 }
207 krb5_get_init_creds_opt_set_forwardable(&icopts, opts->forwardable);
208 krb5_get_init_creds_opt_set_renew_life(&icopts, opts->renewable);
209 if(data->hascreds) {
210 krb5_free_cred_contents(data->ctx, &data->initcreds);
211 data->hascreds = 0;
212 }
213 if((ret = krb5_get_init_creds_keytab(data->ctx, &data->initcreds, data->me, kt, 0, NULL, &icopts)) != 0) {
214 log(LOG_ERR, "could not get credentials: %s", error_message(ret));
215 ret = PAM_SERVICE_ERR;
216 goto out;
217 }
218 data->hascreds = 1;
219 if(opts->debug)
220 log(LOG_DEBUG, "got creds successfully");
221 snprintf(buf, sizeof(buf), "KRB5CCNAME=FILE:/tmp/krb5cc_%i_XXXXXX", data->uid);
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222 ccname = buf + sizeof("KRB5CCNAME=") - 1;
223 filename = ccname + sizeof("FILE:") - 1;
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224 if((fd = mkstemp(filename)) < 0) {
225 log(LOG_ERR, "could not create tempfile for credentials cache: %s", strerror(errno));
226 ret = PAM_SERVICE_ERR;
227 goto out;
228 }
229 close(fd);
230 if(opts->debug)
231 log(LOG_DEBUG, "created ccache `%s'", filename);
232 if((ret = krb5_cc_resolve(data->ctx, ccname, &data->cc)) != 0) {
233 log(LOG_ERR, "could not resolve ccache `%s': %s", ccname, error_message(ret));
234 unlink(filename);
235 ret = PAM_SERVICE_ERR;
236 goto out;
237 }
238 if((ret = krb5_cc_initialize(data->ctx, data->cc, data->me)) != 0) {
239 log(LOG_ERR, "could not initialize credentials cache `%s': %s", ccname, error_message(ret));
240 unlink(filename);
241 ret = PAM_SERVICE_ERR;
242 goto out;
243 }
244 if((ret = krb5_cc_store_cred(data->ctx, data->cc, &data->initcreds)) != 0) {
245 log(LOG_ERR, "could not store credentials: %s", error_message(ret));
246 unlink(filename);
247 ret = PAM_SERVICE_ERR;
248 goto out;
249 }
e1427cb7 250 chown(filename, data->uid, data->gid);
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251 pam_putenv(pamh, strdup(buf));
252 if(opts->debug)
253 log(LOG_DEBUG, "successfully initialized ccache");
254 ret = PAM_SUCCESS;
255
256 out:
257 if(kt != NULL)
258 krb5_kt_close(data->ctx, kt);
259 return(ret);
260}
261
262static int delcreds(pam_handle_t *pamh, struct options *opts, struct data *data)
263{
264 if(opts->debug)
265 log(LOG_DEBUG, "deleting credentials");
266 if(data->hascreds) {
267 krb5_free_cred_contents(data->ctx, &data->initcreds);
268 data->hascreds = 0;
269 if(opts->debug)
270 log(LOG_DEBUG, "freed internal creds");
271 }
272 if(data->cc != NULL) {
273 krb5_cc_destroy(data->ctx, data->cc);
274 data->cc = NULL;
275 if(opts->debug)
276 log(LOG_DEBUG, "destroyed ccache");
277 }
278 return(PAM_SUCCESS);
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279}
280
281PAM_EXTERN int pam_sm_authenticate(pam_handle_t *pamh, int flags, int argc, const char **argv)
282{
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283 struct options *opts;
284
285 opts = parseopts(argc, argv);
286 if(opts->debug)
287 log(LOG_DEBUG, "pam_sm_authenticate called");
288 freeopts(opts);
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289 return(PAM_IGNORE);
290}
291
292PAM_EXTERN int pam_sm_setcred(pam_handle_t *pamh, int flags, int argc, const char **argv)
293{
294 struct options *opts;
295 struct data *data;
eb2a40de 296 int ret;
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297
298 opts = parseopts(argc, argv);
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299 if(opts->debug)
300 log(LOG_DEBUG, "pam_sm_setcred called");
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301 data = getdata(pamh, opts);
302 if(data == NULL) {
303 log(LOG_ERR, "could not get data, erroring out");
304 return(PAM_SERVICE_ERR);
305 }
eb2a40de 306 ret = PAM_SERVICE_ERR;
2febc19a 307 if(flags & PAM_ESTABLISH_CRED) {
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308 ret = savecreds(pamh, opts, data);
309 } else if(flags & PAM_DELETE_CRED) {
310 ret = delcreds(pamh, opts, data);
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311 }
312 freeopts(opts);
eb2a40de 313 return(ret);
2febc19a 314}
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315
316/*
317 * Local Variables:
4aa1b80b 318 * compile-command: "gcc -Wall -g --shared -fPIC -o pam_krb5auto.so pam_krb5auto.c -lkrb5"
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319 * End:
320 */