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384 lines
12 KiB
384 lines
12 KiB
commit c04a21e050d64a1193a6daab872bca2528bda44b
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Author: Florian Weimer <fweimer@redhat.com>
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Date: Thu Apr 25 15:01:07 2024 +0200
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CVE-2024-33601, CVE-2024-33602: nscd: netgroup: Use two buffers in addgetnetgrentX (bug 31680)
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This avoids potential memory corruption when the underlying NSS
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callback function does not use the buffer space to store all strings
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(e.g., for constant strings).
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Instead of custom buffer management, two scratch buffers are used.
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This increases stack usage somewhat.
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Scratch buffer allocation failure is handled by return -1
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(an invalid timeout value) instead of terminating the process.
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This fixes bug 31679.
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Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
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diff --git a/nscd/netgroupcache.c b/nscd/netgroupcache.c
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index f656872ae8c3b888..dd180f8083e7c9f9 100644
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--- a/nscd/netgroupcache.c
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+++ b/nscd/netgroupcache.c
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@@ -24,6 +24,7 @@
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#include <stdlib.h>
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#include <unistd.h>
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#include <sys/mman.h>
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+#include <scratch_buffer.h>
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#include "../inet/netgroup.h"
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#include "nscd.h"
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@@ -66,6 +67,16 @@ struct dataset
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char strdata[0];
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};
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+/* Send a notfound response to FD. Always returns -1 to indicate an
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+ ephemeral error. */
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+static time_t
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+send_notfound (int fd)
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+{
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+ if (fd != -1)
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+ TEMP_FAILURE_RETRY (send (fd, ¬found, sizeof (notfound), MSG_NOSIGNAL));
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+ return -1;
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+}
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+
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/* Sends a notfound message and prepares a notfound dataset to write to the
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cache. Returns true if there was enough memory to allocate the dataset and
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returns the dataset in DATASETP, total bytes to write in TOTALP and the
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@@ -84,8 +95,7 @@ do_notfound (struct database_dyn *db, int fd, request_header *req,
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total = sizeof (notfound);
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timeout = time (NULL) + db->negtimeout;
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- if (fd != -1)
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- TEMP_FAILURE_RETRY (send (fd, ¬found, total, MSG_NOSIGNAL));
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+ send_notfound (fd);
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dataset = mempool_alloc (db, sizeof (struct dataset) + req->key_len, 1);
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/* If we cannot permanently store the result, so be it. */
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@@ -110,11 +120,78 @@ do_notfound (struct database_dyn *db, int fd, request_header *req,
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return cacheable;
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}
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+struct addgetnetgrentX_scratch
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+{
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+ /* This is the result that the caller should use. It can be NULL,
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+ point into buffer, or it can be in the cache. */
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+ struct dataset *dataset;
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+
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+ struct scratch_buffer buffer;
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+
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+ /* Used internally in addgetnetgrentX as a staging area. */
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+ struct scratch_buffer tmp;
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+
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+ /* Number of bytes in buffer that are actually used. */
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+ size_t buffer_used;
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+};
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+
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+static void
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+addgetnetgrentX_scratch_init (struct addgetnetgrentX_scratch *scratch)
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+{
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+ scratch->dataset = NULL;
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+ scratch_buffer_init (&scratch->buffer);
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+ scratch_buffer_init (&scratch->tmp);
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+
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+ /* Reserve space for the header. */
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+ scratch->buffer_used = sizeof (struct dataset);
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+ static_assert (sizeof (struct dataset) < sizeof (scratch->tmp.__space),
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+ "initial buffer space");
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+ memset (scratch->tmp.data, 0, sizeof (struct dataset));
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+}
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+
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+static void
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+addgetnetgrentX_scratch_free (struct addgetnetgrentX_scratch *scratch)
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+{
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+ scratch_buffer_free (&scratch->buffer);
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+ scratch_buffer_free (&scratch->tmp);
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+}
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+
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+/* Copy LENGTH bytes from S into SCRATCH. Returns NULL if SCRATCH
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+ could not be resized, otherwise a pointer to the copy. */
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+static char *
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+addgetnetgrentX_append_n (struct addgetnetgrentX_scratch *scratch,
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+ const char *s, size_t length)
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+{
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+ while (true)
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+ {
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+ size_t remaining = scratch->buffer.length - scratch->buffer_used;
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+ if (remaining >= length)
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+ break;
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+ if (!scratch_buffer_grow_preserve (&scratch->buffer))
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+ return NULL;
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+ }
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+ char *copy = scratch->buffer.data + scratch->buffer_used;
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+ memcpy (copy, s, length);
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+ scratch->buffer_used += length;
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+ return copy;
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+}
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+
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+/* Copy S into SCRATCH, including its null terminator. Returns false
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+ if SCRATCH could not be resized. */
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+static bool
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+addgetnetgrentX_append (struct addgetnetgrentX_scratch *scratch, const char *s)
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+{
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+ if (s == NULL)
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+ s = "";
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+ return addgetnetgrentX_append_n (scratch, s, strlen (s) + 1) != NULL;
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+}
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+
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+/* Caller must initialize and free *SCRATCH. If the return value is
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+ negative, this function has sent a notfound response. */
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static time_t
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addgetnetgrentX (struct database_dyn *db, int fd, request_header *req,
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const char *key, uid_t uid, struct hashentry *he,
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- struct datahead *dh, struct dataset **resultp,
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- void **tofreep)
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+ struct datahead *dh, struct addgetnetgrentX_scratch *scratch)
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{
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if (__glibc_unlikely (debug_level > 0))
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{
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@@ -133,14 +210,10 @@ addgetnetgrentX (struct database_dyn *db, int fd, request_header *req,
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char *key_copy = NULL;
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struct __netgrent data;
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- size_t buflen = MAX (1024, sizeof (*dataset) + req->key_len);
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- size_t buffilled = sizeof (*dataset);
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- char *buffer = NULL;
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size_t nentries = 0;
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size_t group_len = strlen (key) + 1;
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struct name_list *first_needed
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= alloca (sizeof (struct name_list) + group_len);
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- *tofreep = NULL;
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if (netgroup_database == NULL
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&& __nss_database_lookup2 ("netgroup", NULL, NULL, &netgroup_database))
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@@ -152,8 +225,6 @@ addgetnetgrentX (struct database_dyn *db, int fd, request_header *req,
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}
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memset (&data, '\0', sizeof (data));
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- buffer = xmalloc (buflen);
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- *tofreep = buffer;
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first_needed->next = first_needed;
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memcpy (first_needed->name, key, group_len);
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data.needed_groups = first_needed;
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@@ -196,8 +267,8 @@ addgetnetgrentX (struct database_dyn *db, int fd, request_header *req,
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while (1)
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{
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int e;
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- status = getfct.f (&data, buffer + buffilled,
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- buflen - buffilled - req->key_len, &e);
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+ status = getfct.f (&data, scratch->tmp.data,
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+ scratch->tmp.length, &e);
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if (status == NSS_STATUS_SUCCESS)
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{
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if (data.type == triple_val)
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@@ -205,68 +276,10 @@ addgetnetgrentX (struct database_dyn *db, int fd, request_header *req,
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const char *nhost = data.val.triple.host;
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const char *nuser = data.val.triple.user;
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const char *ndomain = data.val.triple.domain;
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-
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- size_t hostlen = strlen (nhost ?: "") + 1;
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- size_t userlen = strlen (nuser ?: "") + 1;
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- size_t domainlen = strlen (ndomain ?: "") + 1;
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-
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- if (nhost == NULL || nuser == NULL || ndomain == NULL
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- || nhost > nuser || nuser > ndomain)
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- {
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- const char *last = nhost;
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- if (last == NULL
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- || (nuser != NULL && nuser > last))
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- last = nuser;
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- if (last == NULL
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- || (ndomain != NULL && ndomain > last))
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- last = ndomain;
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-
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- size_t bufused
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- = (last == NULL
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- ? buffilled
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- : last + strlen (last) + 1 - buffer);
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-
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- /* We have to make temporary copies. */
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- size_t needed = hostlen + userlen + domainlen;
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-
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- if (buflen - req->key_len - bufused < needed)
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- {
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- buflen += MAX (buflen, 2 * needed);
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- /* Save offset in the old buffer. We don't
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- bother with the NULL check here since
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- we'll do that later anyway. */
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- size_t nhostdiff = nhost - buffer;
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- size_t nuserdiff = nuser - buffer;
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- size_t ndomaindiff = ndomain - buffer;
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-
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- char *newbuf = xrealloc (buffer, buflen);
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- /* Fix up the triplet pointers into the new
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- buffer. */
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- nhost = (nhost ? newbuf + nhostdiff
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- : NULL);
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- nuser = (nuser ? newbuf + nuserdiff
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- : NULL);
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- ndomain = (ndomain ? newbuf + ndomaindiff
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- : NULL);
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- *tofreep = buffer = newbuf;
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- }
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-
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- nhost = memcpy (buffer + bufused,
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- nhost ?: "", hostlen);
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- nuser = memcpy ((char *) nhost + hostlen,
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- nuser ?: "", userlen);
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- ndomain = memcpy ((char *) nuser + userlen,
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- ndomain ?: "", domainlen);
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- }
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-
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- char *wp = buffer + buffilled;
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- wp = memmove (wp, nhost ?: "", hostlen);
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- wp += hostlen;
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- wp = memmove (wp, nuser ?: "", userlen);
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- wp += userlen;
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- wp = memmove (wp, ndomain ?: "", domainlen);
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- wp += domainlen;
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- buffilled = wp - buffer;
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+ if (!(addgetnetgrentX_append (scratch, nhost)
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+ && addgetnetgrentX_append (scratch, nuser)
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+ && addgetnetgrentX_append (scratch, ndomain)))
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+ return send_notfound (fd);
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++nentries;
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}
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else
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@@ -318,8 +331,8 @@ addgetnetgrentX (struct database_dyn *db, int fd, request_header *req,
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}
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else if (status == NSS_STATUS_TRYAGAIN && e == ERANGE)
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{
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- buflen *= 2;
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- *tofreep = buffer = xrealloc (buffer, buflen);
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+ if (!scratch_buffer_grow (&scratch->tmp))
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+ return send_notfound (fd);
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}
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else if (status == NSS_STATUS_RETURN
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|| status == NSS_STATUS_NOTFOUND
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@@ -352,10 +365,17 @@ addgetnetgrentX (struct database_dyn *db, int fd, request_header *req,
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goto maybe_cache_add;
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}
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- total = buffilled;
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+ /* Capture the result size without the key appended. */
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+ total = scratch->buffer_used;
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+
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+ /* Make a copy of the key. The scratch buffer must not move after
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+ this point. */
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+ key_copy = addgetnetgrentX_append_n (scratch, key, req->key_len);
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+ if (key_copy == NULL)
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+ return send_notfound (fd);
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/* Fill in the dataset. */
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- dataset = (struct dataset *) buffer;
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+ dataset = scratch->buffer.data;
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timeout = datahead_init_pos (&dataset->head, total + req->key_len,
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total - offsetof (struct dataset, resp),
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he == NULL ? 0 : dh->nreloads + 1,
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@@ -364,11 +384,7 @@ addgetnetgrentX (struct database_dyn *db, int fd, request_header *req,
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dataset->resp.version = NSCD_VERSION;
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dataset->resp.found = 1;
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dataset->resp.nresults = nentries;
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- dataset->resp.result_len = buffilled - sizeof (*dataset);
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-
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- assert (buflen - buffilled >= req->key_len);
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- key_copy = memcpy (buffer + buffilled, key, req->key_len);
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- buffilled += req->key_len;
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+ dataset->resp.result_len = total - sizeof (*dataset);
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/* Now we can determine whether on refill we have to create a new
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record or not. */
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@@ -399,7 +415,7 @@ addgetnetgrentX (struct database_dyn *db, int fd, request_header *req,
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if (__glibc_likely (newp != NULL))
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{
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/* Adjust pointer into the memory block. */
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- key_copy = (char *) newp + (key_copy - buffer);
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+ key_copy = (char *) newp + (key_copy - (char *) dataset);
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dataset = memcpy (newp, dataset, total + req->key_len);
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cacheable = true;
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@@ -440,7 +456,7 @@ addgetnetgrentX (struct database_dyn *db, int fd, request_header *req,
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}
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out:
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- *resultp = dataset;
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+ scratch->dataset = dataset;
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return timeout;
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}
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@@ -461,6 +477,9 @@ addinnetgrX (struct database_dyn *db, int fd, request_header *req,
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if (user != NULL)
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key = (char *) rawmemchr (key, '\0') + 1;
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const char *domain = *key++ ? key : NULL;
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+ struct addgetnetgrentX_scratch scratch;
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+
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+ addgetnetgrentX_scratch_init (&scratch);
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if (__glibc_unlikely (debug_level > 0))
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{
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@@ -476,12 +495,8 @@ addinnetgrX (struct database_dyn *db, int fd, request_header *req,
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group, group_len,
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db, uid);
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time_t timeout;
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- void *tofree;
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if (result != NULL)
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- {
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- timeout = result->head.timeout;
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- tofree = NULL;
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- }
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+ timeout = result->head.timeout;
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else
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{
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request_header req_get =
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@@ -490,7 +505,10 @@ addinnetgrX (struct database_dyn *db, int fd, request_header *req,
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.key_len = group_len
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};
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timeout = addgetnetgrentX (db, -1, &req_get, group, uid, NULL, NULL,
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- &result, &tofree);
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+ &scratch);
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+ result = scratch.dataset;
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+ if (timeout < 0)
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+ goto out;
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}
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struct indataset
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@@ -604,7 +622,7 @@ addinnetgrX (struct database_dyn *db, int fd, request_header *req,
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}
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out:
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- free (tofree);
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+ addgetnetgrentX_scratch_free (&scratch);
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return timeout;
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}
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@@ -614,11 +632,12 @@ addgetnetgrentX_ignore (struct database_dyn *db, int fd, request_header *req,
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const char *key, uid_t uid, struct hashentry *he,
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struct datahead *dh)
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{
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- struct dataset *ignore;
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- void *tofree;
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- time_t timeout = addgetnetgrentX (db, fd, req, key, uid, he, dh,
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- &ignore, &tofree);
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- free (tofree);
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+ struct addgetnetgrentX_scratch scratch;
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+ addgetnetgrentX_scratch_init (&scratch);
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+ time_t timeout = addgetnetgrentX (db, fd, req, key, uid, he, dh, &scratch);
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+ addgetnetgrentX_scratch_free (&scratch);
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+ if (timeout < 0)
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+ timeout = 0;
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return timeout;
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}
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@@ -662,5 +681,9 @@ readdinnetgr (struct database_dyn *db, struct hashentry *he,
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.key_len = he->len
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};
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- return addinnetgrX (db, -1, &req, db->data + he->key, he->owner, he, dh);
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+ int timeout = addinnetgrX (db, -1, &req, db->data + he->key, he->owner,
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+ he, dh);
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+ if (timeout < 0)
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+ timeout = 0;
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+ return timeout;
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}
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