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Guard one-time initialization with memory barriers
[nss_nonlocal.git] / nonlocal-shadow.c
1 /*
2  * nonlocal-shadow.c
3  * shadow database for nss_nonlocal proxy.
4  *
5  * Copyright © 2007–2010 Anders Kaseorg <andersk@mit.edu>
6  *
7  * This file is part of nss_nonlocal.
8  *
9  * nss_nonlocal is free software; you can redistribute it and/or
10  * modify it under the terms of the GNU Lesser General Public License
11  * as published by the Free Software Foundation; either version 2.1 of
12  * the License, or (at your option) any later version.
13  *
14  * nss_nonlocal is distributed in the hope that it will be useful, but
15  * WITHOUT ANY WARRANTY; without even the implied warranty of
16  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
17  * Lesser General Public License for more details.
18  *
19  * You should have received a copy of the GNU Lesser General Public
20  * License along with nss_nonlocal; if not, write to the Free Software
21  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
22  * 02110-1301  USA
23  */
24
25 #define _GNU_SOURCE
26
27 #include <sys/types.h>
28 #include <dlfcn.h>
29 #include <errno.h>
30 #include <nss.h>
31 #include <shadow.h>
32 #include <stdbool.h>
33 #include <stddef.h>
34 #include <stdlib.h>
35 #include <string.h>
36 #include <syslog.h>
37
38 #include "nsswitch-internal.h"
39 #include "nonlocal.h"
40
41
42 static service_user *__nss_shadow_nonlocal_database;
43
44 static int
45 internal_function
46 __nss_shadow_nonlocal_lookup(service_user **ni, const char *fct_name,
47                             void **fctp)
48 {
49     if (__nss_shadow_nonlocal_database == NULL
50         && __nss_database_lookup("shadow_nonlocal", NULL, NULL,
51                                  &__nss_shadow_nonlocal_database) < 0)
52         return -1;
53
54     *ni = __nss_shadow_nonlocal_database;
55
56     *fctp = __nss_lookup_function(*ni, fct_name);
57     return 0;
58 }
59
60
61 static bool spent_initialized = false;
62 static service_user *spent_startp, *spent_nip;
63 static void *spent_fct_start;
64 static union {
65     enum nss_status (*l)(struct spwd *pwd, char *buffer, size_t buflen,
66                          int *errnop);
67     void *ptr;
68 } spent_fct;
69 static const char *spent_fct_name = "getspent_r";
70
71 enum nss_status
72 _nss_nonlocal_setspent(int stayopen)
73 {
74     enum nss_status status;
75     const struct walk_nss w = {
76         .lookup = &__nss_shadow_nonlocal_lookup, .fct_name = "setspent",
77         .status = &status
78     };
79     const __typeof__(&_nss_nonlocal_setspent) self = NULL;
80 #define args (stayopen)
81 #include "walk_nss.h"
82 #undef args
83     if (status != NSS_STATUS_SUCCESS)
84         return status;
85
86     if (!spent_initialized) {
87         __nss_shadow_nonlocal_lookup(&spent_startp, spent_fct_name,
88                                      &spent_fct_start);
89         __sync_synchronize();
90         spent_initialized = true;
91     }
92     spent_nip = spent_startp;
93     spent_fct.ptr = spent_fct_start;
94     return NSS_STATUS_SUCCESS;
95 }
96
97 enum nss_status
98 _nss_nonlocal_endspent(void)
99 {
100     enum nss_status status;
101     const struct walk_nss w = {
102         .lookup = &__nss_shadow_nonlocal_lookup, .fct_name = "endspent",
103         .status = &status
104     };
105     const __typeof__(&_nss_nonlocal_endspent) self = NULL;
106
107     spent_nip = NULL;
108
109 #define args ()
110 #include "walk_nss.h"
111 #undef args
112     return status;
113 }
114
115 enum nss_status
116 _nss_nonlocal_getspent_r(struct spwd *pwd, char *buffer, size_t buflen,
117                          int *errnop)
118 {
119     enum nss_status status;
120
121     char *nonlocal_ignore = getenv(NONLOCAL_IGNORE_ENV);
122     if (nonlocal_ignore != NULL && nonlocal_ignore[0] != '\0')
123         return NSS_STATUS_UNAVAIL;
124
125     if (spent_nip == NULL) {
126         status = _nss_nonlocal_setspent(0);
127         if (status != NSS_STATUS_SUCCESS)
128             return status;
129     }
130     do {
131         if (spent_fct.ptr == NULL)
132             status = NSS_STATUS_UNAVAIL;
133         else
134             status = DL_CALL_FCT(spent_fct.l, (pwd, buffer, buflen, errnop));   
135         if (status == NSS_STATUS_TRYAGAIN && *errnop == ERANGE)
136             return status;
137
138         if (status == NSS_STATUS_SUCCESS)
139             return NSS_STATUS_SUCCESS;
140     } while (__nss_next(&spent_nip, spent_fct_name, &spent_fct.ptr, status, 0) == 0);
141
142     spent_nip = NULL;
143     return NSS_STATUS_NOTFOUND;
144 }
145
146
147 enum nss_status
148 _nss_nonlocal_getspnam_r(const char *name, struct spwd *pwd,
149                          char *buffer, size_t buflen, int *errnop)
150 {
151     enum nss_status status;
152     const struct walk_nss w = {
153         .lookup = __nss_shadow_nonlocal_lookup, .fct_name = "getspnam_r",
154         .status = &status, .errnop = errnop
155     };
156     const __typeof__(&_nss_nonlocal_getspnam_r) self = NULL;
157 #define args (name, pwd, buffer, buflen, errnop)
158 #include "walk_nss.h"
159 #undef args
160     if (status != NSS_STATUS_SUCCESS)
161         return status;
162
163     if (strcmp(name, pwd->sp_namp) != 0) {
164         syslog(LOG_ERR, "nss_nonlocal: discarding shadow %s from lookup for shadow %s\n", pwd->sp_namp, name);
165         return NSS_STATUS_NOTFOUND;
166     }
167
168     return NSS_STATUS_SUCCESS;
169 }
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