1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
|
/*-
* SPDX-License-Identifier: BSD-2-Clause-FreeBSD
*
* Copyright (c) 2002 Jacques A. Vidrine <nectar@FreeBSD.org>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include <sys/param.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <krb5.h>
#define PAM_SM_AUTH
#define PAM_SM_CRED
#include <security/pam_appl.h>
#include <security/pam_modules.h>
#include <security/pam_mod_misc.h>
static const char superuser[] = "root";
static long get_su_principal(krb5_context, const char *, const char *,
char **, krb5_principal *);
static int auth_krb5(pam_handle_t *, krb5_context, const char *,
krb5_principal);
PAM_EXTERN int
pam_sm_authenticate(pam_handle_t *pamh, int flags __unused,
int argc __unused, const char *argv[] __unused)
{
krb5_context context;
krb5_principal su_principal;
const char *user;
const void *ruser;
char *su_principal_name;
long rv;
int pamret;
pamret = pam_get_user(pamh, &user, NULL);
if (pamret != PAM_SUCCESS)
return (pamret);
PAM_LOG("Got user: %s", user);
pamret = pam_get_item(pamh, PAM_RUSER, &ruser);
if (pamret != PAM_SUCCESS)
return (pamret);
PAM_LOG("Got ruser: %s", (const char *)ruser);
rv = krb5_init_context(&context);
if (rv != 0) {
const char *msg = krb5_get_error_message(context, rv);
PAM_LOG("krb5_init_context failed: %s", msg);
krb5_free_error_message(context, msg);
return (PAM_SERVICE_ERR);
}
rv = get_su_principal(context, user, ruser, &su_principal_name, &su_principal);
if (rv != 0)
return (PAM_AUTH_ERR);
PAM_LOG("kuserok: %s -> %s", su_principal_name, user);
rv = krb5_kuserok(context, su_principal, user);
pamret = rv ? auth_krb5(pamh, context, su_principal_name, su_principal) : PAM_AUTH_ERR;
free(su_principal_name);
krb5_free_principal(context, su_principal);
krb5_free_context(context);
return (pamret);
}
PAM_EXTERN int
pam_sm_setcred(pam_handle_t *pamh __unused, int flags __unused,
int ac __unused, const char *av[] __unused)
{
return (PAM_SUCCESS);
}
/* Authenticate using Kerberos 5.
* pamh -- The PAM handle.
* context -- An initialized krb5_context.
* su_principal_name -- The target principal name, used only for password prompts.
* If NULL, the password prompts will not include a principal
* name.
* su_principal -- The target krb5_principal.
* Note that a valid keytab in the default location with a host entry
* must be available, and that the PAM application must have sufficient
* privileges to access it.
* Returns PAM_SUCCESS if authentication was successful, or an appropriate
* PAM error code if it was not.
*/
static int
auth_krb5(pam_handle_t *pamh, krb5_context context, const char *su_principal_name,
krb5_principal su_principal)
{
krb5_creds creds;
krb5_get_init_creds_opt *gic_opt;
krb5_verify_init_creds_opt vic_opt;
const char *pass;
char *prompt;
long rv;
int pamret;
prompt = NULL;
krb5_verify_init_creds_opt_init(&vic_opt);
if (su_principal_name != NULL)
(void)asprintf(&prompt, "Password for %s:", su_principal_name);
else
(void)asprintf(&prompt, "Password:");
if (prompt == NULL)
return (PAM_BUF_ERR);
pass = NULL;
pamret = pam_get_authtok(pamh, PAM_AUTHTOK, &pass, prompt);
free(prompt);
if (pamret != PAM_SUCCESS)
return (pamret);
rv = krb5_get_init_creds_opt_alloc(context, &gic_opt);
if (rv != 0) {
const char *msg = krb5_get_error_message(context, rv);
PAM_LOG("krb5_get_init_creds_opt_alloc: %s", msg);
krb5_free_error_message(context, msg);
return (PAM_AUTH_ERR);
}
rv = krb5_get_init_creds_password(context, &creds, su_principal,
pass, NULL, NULL, 0, NULL, gic_opt);
krb5_get_init_creds_opt_free(context, gic_opt);
if (rv != 0) {
const char *msg = krb5_get_error_message(context, rv);
PAM_LOG("krb5_get_init_creds_password: %s", msg);
krb5_free_error_message(context, msg);
return (PAM_AUTH_ERR);
}
krb5_verify_init_creds_opt_set_ap_req_nofail(&vic_opt, 1);
rv = krb5_verify_init_creds(context, &creds, NULL, NULL, NULL,
&vic_opt);
krb5_free_cred_contents(context, &creds);
if (rv != 0) {
const char *msg = krb5_get_error_message(context, rv);
PAM_LOG("krb5_verify_init_creds: %s", msg);
krb5_free_error_message(context, msg);
return (PAM_AUTH_ERR);
}
return (PAM_SUCCESS);
}
/* Determine the target principal given the current user and the target user.
* context -- An initialized krb5_context.
* target_user -- The target username.
* current_user -- The current username.
* su_principal_name -- (out) The target principal name.
* su_principal -- (out) The target krb5_principal.
* When the target user is `root', the target principal will be a `root
* instance', e.g. `luser/root@REA.LM'. Otherwise, the target principal
* will simply be the current user's default principal name. Note that
* in any case, if KRB5CCNAME is set and a credentials cache exists, the
* principal name found there will be the `starting point', rather than
* the ruser parameter.
*
* Returns 0 for success, or a com_err error code on failure.
*/
static long
get_su_principal(krb5_context context, const char *target_user, const char *current_user,
char **su_principal_name, krb5_principal *su_principal)
{
krb5_principal default_principal;
krb5_ccache ccache;
char *principal_name, *ccname, *p;
long rv;
uid_t euid, ruid;
*su_principal = NULL;
default_principal = NULL;
/* Unless KRB5CCNAME was explicitly set, we won't really be able
* to look at the credentials cache since krb5_cc_default will
* look at getuid().
*/
ruid = getuid();
euid = geteuid();
rv = seteuid(ruid);
if (rv != 0)
return (errno);
p = getenv("KRB5CCNAME");
if (p != NULL)
ccname = strdup(p);
else
(void)asprintf(&ccname, "%s%lu", KRB5_DEFAULT_CCROOT, (unsigned long)ruid);
if (ccname == NULL)
return (errno);
rv = krb5_cc_resolve(context, ccname, &ccache);
free(ccname);
if (rv == 0) {
rv = krb5_cc_get_principal(context, ccache, &default_principal);
krb5_cc_close(context, ccache);
if (rv != 0)
default_principal = NULL; /* just to be safe */
}
rv = seteuid(euid);
if (rv != 0)
return (errno);
if (default_principal == NULL) {
rv = krb5_make_principal(context, &default_principal, NULL, current_user, NULL);
if (rv != 0) {
PAM_LOG("Could not determine default principal name.");
return (rv);
}
}
/* Now that we have some principal, if the target account is
* `root', then transform it into a `root' instance, e.g.
* `user@REA.LM' -> `user/root@REA.LM'.
*/
rv = krb5_unparse_name(context, default_principal, &principal_name);
krb5_free_principal(context, default_principal);
if (rv != 0) {
const char *msg = krb5_get_error_message(context, rv);
PAM_LOG("krb5_unparse_name: %s", msg);
krb5_free_error_message(context, msg);
return (rv);
}
PAM_LOG("Default principal name: %s", principal_name);
if (strcmp(target_user, superuser) == 0) {
p = strrchr(principal_name, '@');
if (p == NULL) {
PAM_LOG("malformed principal name `%s'", principal_name);
free(principal_name);
return (rv);
}
*p++ = '\0';
*su_principal_name = NULL;
(void)asprintf(su_principal_name, "%s/%s@%s", principal_name, superuser, p);
free(principal_name);
} else
*su_principal_name = principal_name;
if (*su_principal_name == NULL)
return (errno);
rv = krb5_parse_name(context, *su_principal_name, &default_principal);
if (rv != 0) {
const char *msg = krb5_get_error_message(context, rv);
PAM_LOG("krb5_parse_name `%s': %s", *su_principal_name, msg);
krb5_free_error_message(context, msg);
free(*su_principal_name);
return (rv);
}
PAM_LOG("Target principal name: %s", *su_principal_name);
*su_principal = default_principal;
return (0);
}
PAM_MODULE_ENTRY("pam_ksu");
|
