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9b456c5da9
__nss_database_lookup2's extra arguments were left unused in the nsswitch reloading patch set; this broke compat (default config ignored) and shadow files (secondary name ignored) which relies on these fallbacks. This patch adds in the previous behavior by correcting the initialization of the database list to reflect the fallbacks. This means that the nss_database_lookup2 interface no longer needs to be passed the fallback info, so API and callers were adjusted. Since all callers needed to be edited anyway, the calls were changed from __nss_database_lookup2 to the faster __nss_database_get. This was an intended optimization which was deferred during the initial lookup changes to avoid touching so many files. The test case verifies that compat targets work (passwd) and that the default configuration works (group). Tested on x86-64.
372 lines
12 KiB
C
372 lines
12 KiB
C
/* Global list of NSS service modules.
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Copyright (c) 2020-2021 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 <nscd/nscd.h>
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#include <nscd/nscd_proto.h>
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#include <array_length.h>
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#include <assert.h>
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#include <atomic.h>
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#include <dlfcn.h>
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#include <gnu/lib-names.h>
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#include <libc-lock.h>
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#include <stddef.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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/* Suffix after .so of NSS service modules. This is a bit of magic,
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but we assume LIBNSS_FILES_SO looks like "libnss_files.so.2" and we
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want a pointer to the ".2" part. We have no API to extract this
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except through the auto-generated lib-names.h and some static
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pointer manipulation. The "-1" accounts for the trailing NUL
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included in the sizeof. */
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static const char *const __nss_shlib_revision
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= LIBNSS_FILES_SO + sizeof("libnss_files.so") - 1;
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/* A single-linked list used to implement a mapping from service names
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to NSS modules. (Most systems only use five or so modules, so a
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list is sufficient here.) Elements of this list are never freed
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during normal operation. */
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static struct nss_module *nss_module_list;
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/* Covers the list and also loading of individual NSS service
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modules. */
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__libc_lock_define (static, nss_module_list_lock);
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#if defined USE_NSCD && (!defined DO_STATIC_NSS || defined SHARED)
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/* Nonzero if this is the nscd process. */
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static bool is_nscd;
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/* The callback passed to the init functions when nscd is used. */
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static void (*nscd_init_cb) (size_t, struct traced_file *);
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#endif
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/* Allocate the service NAME with length NAME_LENGTH. If the service
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is already allocated in the nss_module_list cache then we return a
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pointer to the struct nss_module, otherwise we try to allocate a
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new struct nss_module entry and add it to the global
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nss_modules_list cache. If we fail to allocate the entry we return
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NULL. Failure to allocate the entry is always transient. */
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struct nss_module *
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__nss_module_allocate (const char *name, size_t name_length)
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{
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__libc_lock_lock (nss_module_list_lock);
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struct nss_module *result = NULL;
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for (struct nss_module *p = nss_module_list; p != NULL; p = p->next)
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if (strncmp (p->name, name, name_length) == 0
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&& p->name[name_length] == '\0')
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{
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/* Return the previously existing object. */
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result = p;
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break;
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}
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if (result == NULL)
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{
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/* Allocate a new list entry if the name was not found in the
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list. */
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result = malloc (sizeof (*result) + name_length + 1);
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if (result != NULL)
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{
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result->state = nss_module_uninitialized;
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memcpy (result->name, name, name_length);
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result->name[name_length] = '\0';
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result->handle = NULL;
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result->next = nss_module_list;
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nss_module_list = result;
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}
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}
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__libc_lock_unlock (nss_module_list_lock);
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return result;
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}
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/* Long enough to store the name of any function in the
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nss_function_name_array list below, as getprotobynumber_r is the
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longest entry in that list. */
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typedef char function_name[sizeof("getprotobynumber_r")];
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static const function_name nss_function_name_array[] =
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{
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#undef DEFINE_NSS_FUNCTION
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#define DEFINE_NSS_FUNCTION(x) #x,
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#include "function.def"
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};
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/* Internal implementation of __nss_module_load. */
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static bool
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module_load (struct nss_module *module)
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{
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void *handle;
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{
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char *shlib_name;
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if (__asprintf (&shlib_name, "libnss_%s.so%s",
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module->name, __nss_shlib_revision) < 0)
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/* This is definitely a temporary failure. Do not update
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module->state. This will trigger another attempt at the next
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call. */
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return false;
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handle = __libc_dlopen (shlib_name);
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free (shlib_name);
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}
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/* Failing to load the module can be caused by several different
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scenarios. One such scenario is that the module has been removed
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from the disk. In which case the in-memory version is all that
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we have, and if the module->state indidates it is loaded then we
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can use it. */
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if (handle == NULL)
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{
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/* dlopen failure. We do not know if this a temporary or
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permanent error. See bug 22041. Update the state using the
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double-checked locking idiom. */
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__libc_lock_lock (nss_module_list_lock);
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bool result = result;
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switch ((enum nss_module_state) atomic_load_acquire (&module->state))
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{
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case nss_module_uninitialized:
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atomic_store_release (&module->state, nss_module_failed);
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result = false;
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break;
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case nss_module_loaded:
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result = true;
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break;
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case nss_module_failed:
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result = false;
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break;
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}
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__libc_lock_unlock (nss_module_list_lock);
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return result;
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}
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nss_module_functions_untyped pointers;
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/* Look up and store locally all the function pointers we may need
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later. Doing this now means the data will not change in the
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future. */
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for (size_t idx = 0; idx < array_length (nss_function_name_array); ++idx)
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{
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char *function_name;
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if (__asprintf (&function_name, "_nss_%s_%s",
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module->name, nss_function_name_array[idx]) < 0)
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{
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/* Definitely a temporary error. */
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__libc_dlclose (handle);
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return false;
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}
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pointers[idx] = __libc_dlsym (handle, function_name);
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free (function_name);
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#ifdef PTR_MANGLE
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PTR_MANGLE (pointers[idx]);
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#endif
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}
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# ifdef USE_NSCD
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if (is_nscd)
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{
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/* Call the init function when nscd is used. */
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size_t initlen = (5 + strlen (module->name)
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+ strlen ("_init") + 1);
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char init_name[initlen];
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/* Construct the init function name. */
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__stpcpy (__stpcpy (__stpcpy (init_name,
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"_nss_"),
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module->name),
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"_init");
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/* Find the optional init function. */
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void (*ifct) (void (*) (size_t, struct traced_file *))
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= __libc_dlsym (handle, init_name);
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if (ifct != NULL)
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{
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void (*cb) (size_t, struct traced_file *) = nscd_init_cb;
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# ifdef PTR_DEMANGLE
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PTR_DEMANGLE (cb);
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# endif
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ifct (cb);
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}
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}
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# endif
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/* Install the function pointers, following the double-checked
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locking idiom. Delay this after all processing, in case loading
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the module triggers unwinding. */
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__libc_lock_lock (nss_module_list_lock);
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switch ((enum nss_module_state) atomic_load_acquire (&module->state))
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{
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case nss_module_uninitialized:
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case nss_module_failed:
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memcpy (module->functions.untyped, pointers,
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sizeof (module->functions.untyped));
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module->handle = handle;
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/* Synchronizes with unlocked __nss_module_load atomic_load_acquire. */
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atomic_store_release (&module->state, nss_module_loaded);
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break;
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case nss_module_loaded:
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/* If the module was already loaded, close our own handle. This
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does not actually unload the modules, only the reference
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counter is decremented for the loaded module. */
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__libc_dlclose (handle);
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break;
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}
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__libc_lock_unlock (nss_module_list_lock);
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return true;
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}
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/* Force the module identified by MODULE to be loaded. We return
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false if the module could not be loaded, true otherwise. Loading
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the module requires looking up all the possible interface APIs and
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caching the results. */
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bool
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__nss_module_load (struct nss_module *module)
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{
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switch ((enum nss_module_state) atomic_load_acquire (&module->state))
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{
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case nss_module_uninitialized:
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return module_load (module);
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case nss_module_loaded:
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/* Loading has already succeeded. */
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return true;
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case nss_module_failed:
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/* Loading previously failed. */
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return false;
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}
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__builtin_unreachable ();
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}
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static int
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name_search (const void *left, const void *right)
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{
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return strcmp (left, right);
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}
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/* Load module MODULE (if it isn't already) and return a pointer to
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the module's implementation of NAME, otherwise return NULL on
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failure or error. */
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void *
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__nss_module_get_function (struct nss_module *module, const char *name)
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{
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if (!__nss_module_load (module))
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return NULL;
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function_name *name_entry = bsearch (name, nss_function_name_array,
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array_length (nss_function_name_array),
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sizeof (function_name), name_search);
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assert (name_entry != NULL);
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size_t idx = name_entry - nss_function_name_array;
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void *fptr = module->functions.untyped[idx];
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#ifdef PTR_DEMANGLE
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PTR_DEMANGLE (fptr);
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#endif
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return fptr;
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}
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#if defined SHARED && defined USE_NSCD
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/* Load all libraries for the service. */
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static void
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nss_load_all_libraries (enum nss_database service)
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{
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nss_action_list ni = NULL;
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if (__nss_database_get (service, &ni))
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while (ni->module != NULL)
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{
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__nss_module_load (ni->module);
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++ni;
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}
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}
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define_traced_file (pwd, _PATH_NSSWITCH_CONF);
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define_traced_file (grp, _PATH_NSSWITCH_CONF);
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define_traced_file (hst, _PATH_NSSWITCH_CONF);
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define_traced_file (serv, _PATH_NSSWITCH_CONF);
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define_traced_file (netgr, _PATH_NSSWITCH_CONF);
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/* Called by nscd and nscd alone. */
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void
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__nss_disable_nscd (void (*cb) (size_t, struct traced_file *))
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{
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void (*cb1) (size_t, struct traced_file *);
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cb1 = cb;
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# ifdef PTR_MANGLE
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PTR_MANGLE (cb);
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# endif
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nscd_init_cb = cb;
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is_nscd = true;
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/* Find all the relevant modules so that the init functions are called. */
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nss_load_all_libraries (nss_database_passwd);
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nss_load_all_libraries (nss_database_group);
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nss_load_all_libraries (nss_database_hosts);
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nss_load_all_libraries (nss_database_services);
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/* Make sure NSCD purges its cache if nsswitch.conf changes. */
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init_traced_file (&pwd_traced_file.file, _PATH_NSSWITCH_CONF, 0);
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cb1 (pwddb, &pwd_traced_file.file);
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init_traced_file (&grp_traced_file.file, _PATH_NSSWITCH_CONF, 0);
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cb1 (grpdb, &grp_traced_file.file);
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init_traced_file (&hst_traced_file.file, _PATH_NSSWITCH_CONF, 0);
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cb1 (hstdb, &hst_traced_file.file);
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init_traced_file (&serv_traced_file.file, _PATH_NSSWITCH_CONF, 0);
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cb1 (servdb, &serv_traced_file.file);
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init_traced_file (&netgr_traced_file.file, _PATH_NSSWITCH_CONF, 0);
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cb1 (netgrdb, &netgr_traced_file.file);
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/* Disable all uses of NSCD. */
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__nss_not_use_nscd_passwd = -1;
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__nss_not_use_nscd_group = -1;
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__nss_not_use_nscd_hosts = -1;
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__nss_not_use_nscd_services = -1;
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__nss_not_use_nscd_netgroup = -1;
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}
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#endif
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/* Block attempts to dlopen any module we haven't already opened. */
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void
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__nss_module_disable_loading (void)
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{
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__libc_lock_lock (nss_module_list_lock);
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for (struct nss_module *p = nss_module_list; p != NULL; p = p->next)
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if (p->state == nss_module_uninitialized)
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p->state = nss_module_failed;
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__libc_lock_unlock (nss_module_list_lock);
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}
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void __libc_freeres_fn_section
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__nss_module_freeres (void)
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{
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struct nss_module *current = nss_module_list;
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while (current != NULL)
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{
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if (current->state == nss_module_loaded)
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__libc_dlclose (current->handle);
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struct nss_module *next = current->next;
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free (current);
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current = next;
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}
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nss_module_list = NULL;
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}
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