1/* NSS actions, elements in a nsswitch.conf configuration line.
2 Copyright (c) 2020-2023 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4
5 The GNU C Library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Lesser General Public
7 License as published by the Free Software Foundation; either
8 version 2.1 of the License, or (at your option) any later version.
9
10 The GNU C Library 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 GNU
13 Lesser General Public License for more details.
14
15 You should have received a copy of the GNU Lesser General Public
16 License along with the GNU C Library; if not, see
17 <https://www.gnu.org/licenses/>. */
18
19#include <nsswitch.h>
20
21#include <string.h>
22#include <libc-lock.h>
23
24/* Maintain a global list of NSS action lists. Since most databases
25 use the same list of actions, this list is usually short.
26 Deduplication in __nss_action_allocate ensures that the list does
27 not grow without bounds. */
28
29struct nss_action_list_wrapper
30{
31 /* The next element of the list. */
32 struct nss_action_list_wrapper *next;
33
34 /* Number of elements in the list (excluding the terminator). */
35 size_t count;
36
37 /* NULL-terminated list of actions. */
38 struct nss_action actions[];
39};
40
41/* Toplevel list of allocated NSS action lists. */
42static struct nss_action_list_wrapper *nss_actions;
43
44/* Lock covers the nss_actions list. */
45__libc_lock_define (static, nss_actions_lock);
46
47/* Returns true if the actions are equal (same module, same actions
48 array). */
49static bool
50actions_equal (const struct nss_action *a, const struct nss_action *b)
51{
52 return a->module == b->module && a->action_bits == b->action_bits;
53}
54
55
56/* Returns true if COUNT actions at A and B are equal (according to
57 actions_equal above). Caller must ensure that either A or B have at
58 least COUNT actions. */
59static bool
60action_lists_equal (const struct nss_action *a, const struct nss_action *b,
61 size_t count)
62{
63 for (size_t i = 0; i < count; ++i)
64 if (!actions_equal (a + i, b + i))
65 return false;
66 return true;
67}
68
69/* Returns a pre-allocated action list for COUNT actions at ACTIONS,
70 or NULL if no such list exists. */
71static nss_action_list
72find_allocated (struct nss_action *actions, size_t count)
73{
74 for (struct nss_action_list_wrapper *p = nss_actions; p != NULL; p = p->next)
75 if (p->count == count && action_lists_equal (p->actions, actions, count))
76 return p->actions;
77 return NULL;
78}
79
80nss_action_list
81__nss_action_allocate (struct nss_action *actions, size_t count)
82{
83 nss_action_list result = NULL;
84 __libc_lock_lock (nss_actions_lock);
85
86 result = find_allocated (actions, count);
87 if (result == NULL)
88 {
89 struct nss_action_list_wrapper *wrapper
90 = malloc (sizeof (*wrapper) + sizeof (*actions) * count);
91 if (wrapper != NULL)
92 {
93 wrapper->next = nss_actions;
94 wrapper->count = count;
95 memcpy (wrapper->actions, actions, sizeof (*actions) * count);
96 nss_actions = wrapper;
97 result = wrapper->actions;
98 }
99 }
100
101 __libc_lock_unlock (nss_actions_lock);
102 return result;
103}
104
105void
106__nss_action_freeres (void)
107{
108 struct nss_action_list_wrapper *current = nss_actions;
109 while (current != NULL)
110 {
111 struct nss_action_list_wrapper *next = current->next;
112 free (current);
113 current = next;
114 }
115 nss_actions = NULL;
116}
117