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117 lines
3.5 KiB
C
117 lines
3.5 KiB
C
/* NSS actions, elements in a nsswitch.conf configuration line.
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Copyright (c) 2020-2025 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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#include <nsswitch.h>
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#include <string.h>
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#include <libc-lock.h>
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/* Maintain a global list of NSS action lists. Since most databases
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use the same list of actions, this list is usually short.
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Deduplication in __nss_action_allocate ensures that the list does
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not grow without bounds. */
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struct nss_action_list_wrapper
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{
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/* The next element of the list. */
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struct nss_action_list_wrapper *next;
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/* Number of elements in the list (excluding the terminator). */
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size_t count;
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/* NULL-terminated list of actions. */
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struct nss_action actions[];
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};
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/* Toplevel list of allocated NSS action lists. */
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static struct nss_action_list_wrapper *nss_actions;
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/* Lock covers the nss_actions list. */
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__libc_lock_define (static, nss_actions_lock);
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/* Returns true if the actions are equal (same module, same actions
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array). */
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static bool
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actions_equal (const struct nss_action *a, const struct nss_action *b)
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{
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return a->module == b->module && a->action_bits == b->action_bits;
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}
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/* Returns true if COUNT actions at A and B are equal (according to
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actions_equal above). Caller must ensure that either A or B have at
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least COUNT actions. */
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static bool
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action_lists_equal (const struct nss_action *a, const struct nss_action *b,
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size_t count)
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{
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for (size_t i = 0; i < count; ++i)
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if (!actions_equal (a + i, b + i))
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return false;
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return true;
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}
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/* Returns a pre-allocated action list for COUNT actions at ACTIONS,
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or NULL if no such list exists. */
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static nss_action_list
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find_allocated (struct nss_action *actions, size_t count)
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{
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for (struct nss_action_list_wrapper *p = nss_actions; p != NULL; p = p->next)
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if (p->count == count && action_lists_equal (p->actions, actions, count))
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return p->actions;
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return NULL;
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}
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nss_action_list
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__nss_action_allocate (struct nss_action *actions, size_t count)
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{
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nss_action_list result = NULL;
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__libc_lock_lock (nss_actions_lock);
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result = find_allocated (actions, count);
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if (result == NULL)
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{
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struct nss_action_list_wrapper *wrapper
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= malloc (sizeof (*wrapper) + sizeof (*actions) * count);
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if (wrapper != NULL)
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{
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wrapper->next = nss_actions;
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wrapper->count = count;
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memcpy (wrapper->actions, actions, sizeof (*actions) * count);
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nss_actions = wrapper;
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result = wrapper->actions;
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}
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}
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__libc_lock_unlock (nss_actions_lock);
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return result;
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}
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void
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__nss_action_freeres (void)
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{
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struct nss_action_list_wrapper *current = nss_actions;
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while (current != NULL)
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{
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struct nss_action_list_wrapper *next = current->next;
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free (current);
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current = next;
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}
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nss_actions = NULL;
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}
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