--- /dev/null
+ /*
+ Unix SMB/CIFS implementation.
+
+ trivial database library
+
+ Copyright (C) Rusty Russell 2009
+
+ ** NOTE! The following LGPL license applies to the tdb
+ ** library. This does NOT imply that all of Samba is released
+ ** under the LGPL
+
+ This library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 3 of the License, or (at your option) any later version.
+
+ This library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with this library; if not, see <http://www.gnu.org/licenses/>.
+*/
+#include "tdb_private.h"
+#include <limits.h>
+
+/*
+ For each value, we flip F bits in a bitmap of size 2^B. So we can think
+ of this as a F*B bit hash (this isn't quite true due to hash collisions,
+ but it seems good enough for F << B).
+
+ Assume that we only have a single error; this is *not* the birthday
+ problem, since the question is: "does that error hash to the same as
+ the correct value", ie. a simple 1 in 2^F*B. The chances of detecting
+ multiple errors is even higher (since we only need to detect one of
+ them).
+
+ Given that ldb uses a hash size of 10000, using 512 bytes per hash chain
+ (5M) seems reasonable. With 128 hashes, that's about 1 in a million chance
+ of missing a single linked list error.
+*/
+#define NUM_HASHES 128
+#define BITMAP_BITS (512 * CHAR_BIT)
+
+/* We use the excellent Jenkins lookup3 hash; this is based on hash_word2.
+ * See: http://burtleburtle.net/bob/c/lookup3.c
+ */
+#define rot(x,k) (((x)<<(k)) | ((x)>>(32-(k))))
+
+#define final(a,b,c) \
+{ \
+ c ^= b; c -= rot(b,14); \
+ a ^= c; a -= rot(c,11); \
+ b ^= a; b -= rot(a,25); \
+ c ^= b; c -= rot(b,16); \
+ a ^= c; a -= rot(c,4); \
+ b ^= a; b -= rot(a,14); \
+ c ^= b; c -= rot(b,24); \
+}
+
+static void hash(uint32_t key, uint32_t *pc, uint32_t *pb)
+{
+ uint32_t a,b,c;
+
+ /* Set up the internal state */
+ a = b = c = 0xdeadbeef + *pc;
+ c += *pb;
+
+ a += key;
+ final(a,b,c);
+ *pc=c; *pb=b;
+}
+
+static void bit_flip(unsigned char bits[], unsigned int idx)
+{
+ bits[idx / CHAR_BIT] ^= (1 << (idx % CHAR_BIT));
+}
+
+static void add_to_hash(unsigned char bits[], tdb_off_t off)
+{
+ uint32_t h1 = off, h2 = 0;
+ unsigned int i;
+ for (i = 0; i < NUM_HASHES / 2; i++) {
+ hash(off, &h1, &h2);
+ bit_flip(bits, h1 % BITMAP_BITS);
+ bit_flip(bits, h2 % BITMAP_BITS);
+ h2++;
+ }
+}
+
+/* Since we opened it, these shouldn't fail unless it's recent corruption. */
+static bool tdb_check_header(struct tdb_context *tdb, tdb_off_t *recovery)
+{
+ struct tdb_header hdr;
+
+ if (tdb->methods->tdb_read(tdb, 0, &hdr, sizeof(hdr), DOCONV()) == -1)
+ return false;
+ if (strcmp(hdr.magic_food, TDB_MAGIC_FOOD) != 0)
+ goto corrupt;
+
+ CONVERT(hdr);
+ if (hdr.version != TDB_VERSION)
+ goto corrupt;
+
+ if (hdr.rwlocks != 0)
+ goto corrupt;
+
+ if (hdr.hash_size == 0)
+ goto corrupt;
+
+ if (hdr.hash_size != tdb->header.hash_size)
+ goto corrupt;
+
+ if (hdr.recovery_start != 0 &&
+ hdr.recovery_start < TDB_DATA_START(tdb->header.hash_size))
+ goto corrupt;
+
+ *recovery = hdr.recovery_start;
+ return true;
+
+corrupt:
+ tdb->ecode = TDB_ERR_CORRUPT;
+ return false;
+}
+
+static bool tdb_check_record(struct tdb_context *tdb,
+ tdb_off_t off,
+ const struct list_struct *rec)
+{
+ tdb_off_t tailer;
+
+ /* Check rec->next: 0 or points to record offset, aligned. */
+ if (rec->next > 0 && rec->next < TDB_DATA_START(tdb->header.hash_size))
+ goto corrupt;
+ if (rec->next + sizeof(*rec) < rec->next)
+ goto corrupt;
+ if ((rec->next % TDB_ALIGNMENT) != 0)
+ goto corrupt;
+ if (tdb->methods->tdb_oob(tdb, rec->next+sizeof(*rec), 1))
+ goto corrupt;
+
+ /* Check rec_len: similar to rec->next, implies next record. */
+ if ((rec->rec_len % TDB_ALIGNMENT) != 0)
+ goto corrupt;
+ /* Must fit tailer. */
+ if (rec->rec_len < sizeof(tailer))
+ goto corrupt;
+ /* OOB allows "right at the end" access, so this works for last rec. */
+ if (tdb->methods->tdb_oob(tdb, off+sizeof(*rec)+rec->rec_len, 1))
+ goto corrupt;
+
+ /* Check tailer. */
+ if (tdb_ofs_read(tdb, off+sizeof(*rec)+rec->rec_len-sizeof(tailer),
+ &tailer) == -1)
+ goto corrupt;
+ if (tailer != sizeof(*rec) + rec->rec_len)
+ goto corrupt;
+
+ return true;
+
+corrupt:
+ tdb->ecode = TDB_ERR_CORRUPT;
+ return false;
+}
+
+static TDB_DATA get_data(struct tdb_context *tdb, tdb_off_t off, tdb_len_t len)
+{
+ TDB_DATA d;
+
+ d.dsize = len;
+
+ /* We've already done bounds check here. */
+ if (tdb->transaction == NULL && tdb->map_ptr != NULL)
+ d.dptr = (unsigned char *)tdb->map_ptr + off;
+ else
+ d.dptr = tdb_alloc_read(tdb, off, d.dsize);
+ return d;
+}
+
+static void put_data(struct tdb_context *tdb, TDB_DATA d)
+{
+ if (tdb->transaction == NULL && tdb->map_ptr != NULL)
+ return;
+ free(d.dptr);
+}
+
+static bool tdb_check_used_record(struct tdb_context *tdb,
+ tdb_off_t off,
+ const struct list_struct *rec,
+ unsigned char **hashes,
+ int (*check)(TDB_DATA, TDB_DATA, void *),
+ void *private)
+{
+ TDB_DATA key, data;
+
+ if (!tdb_check_record(tdb, off, rec))
+ return false;
+
+ /* key + data + tailer must fit in record */
+ if (rec->key_len + rec->data_len + sizeof(tdb_off_t) > rec->rec_len)
+ return false;
+
+ key = get_data(tdb, off + sizeof(*rec), rec->key_len);
+ if (!key.dptr)
+ return false;
+
+ if (tdb->hash_fn(&key) != rec->full_hash)
+ goto fail_put_key;
+
+ add_to_hash(hashes[BUCKET(rec->full_hash)+1], off);
+ if (rec->next)
+ add_to_hash(hashes[BUCKET(rec->full_hash)+1], rec->next);
+
+ /* If they supply a check function, get data. */
+ if (check) {
+ data = get_data(tdb, off + sizeof(*rec) + rec->key_len,
+ rec->data_len);
+ if (!data.dptr)
+ goto fail_put_key;
+
+ if (check(key, data, private) == -1)
+ goto fail_put_data;
+ put_data(tdb, data);
+ }
+
+ put_data(tdb, key);
+ return true;
+
+fail_put_data:
+ put_data(tdb, data);
+fail_put_key:
+ put_data(tdb, key);
+ return false;
+}
+
+static bool tdb_check_free_record(struct tdb_context *tdb,
+ tdb_off_t off,
+ const struct list_struct *rec,
+ unsigned char **hashes)
+{
+ if (!tdb_check_record(tdb, off, rec))
+ return false;
+
+ add_to_hash(hashes[0], off);
+ if (rec->next)
+ add_to_hash(hashes[0], rec->next);
+ return true;
+}
+
+/* We do this via linear scan, even though it's not 100% accurate. */
+int tdb_check(struct tdb_context *tdb,
+ int (*check)(TDB_DATA key, TDB_DATA data, void *private),
+ void *private)
+{
+ unsigned int h;
+ unsigned char **hashes;
+ tdb_off_t off, recovery_start;
+ struct list_struct rec;
+ bool found_recovery = false;
+
+ if (tdb_lockall(tdb) == -1)
+ return -1;
+
+ /* Make sure we know true size of the underlying file. */
+ tdb->methods->tdb_oob(tdb, tdb->map_size + 1, 1);
+
+ if (!tdb_check_header(tdb, &recovery_start))
+ goto unlock;
+
+ if (tdb->map_size < TDB_DATA_START(tdb->header.hash_size)) {
+ tdb->ecode = TDB_ERR_CORRUPT;
+ goto unlock;
+ }
+
+ /* One big malloc: pointers then bit arrays. */
+ hashes = calloc(1, sizeof(hashes[0]) * (1+tdb->header.hash_size)
+ + BITMAP_BITS / CHAR_BIT * (1+tdb->header.hash_size));
+ if (!hashes) {
+ tdb->ecode = TDB_ERR_OOM;
+ goto unlock;
+ }
+
+ /* Initialize pointers */
+ hashes[0] = (unsigned char *)(&hashes[1+tdb->header.hash_size]);
+ for (h = 1; h < 1+tdb->header.hash_size; h++)
+ hashes[h] = hashes[h-1] + BITMAP_BITS / CHAR_BIT;
+
+ /* Freelist and hash headers are all in a row. */
+ for (h = 0; h < 1+tdb->header.hash_size; h++) {
+ if (tdb_ofs_read(tdb, FREELIST_TOP + h*sizeof(tdb_off_t),
+ &off) == -1)
+ goto free;
+ if (off)
+ add_to_hash(hashes[h], off);
+ }
+
+ for (off = TDB_DATA_START(tdb->header.hash_size);
+ off < tdb->map_size;
+ off += sizeof(rec) + rec.rec_len) {
+ if (tdb->methods->tdb_read(tdb, off, &rec, sizeof(rec),
+ DOCONV()) == -1)
+ goto free;
+ switch (rec.magic) {
+ case TDB_MAGIC:
+ case TDB_DEAD_MAGIC:
+ if (!tdb_check_used_record(tdb, off, &rec, hashes,
+ check, private))
+ goto free;
+ break;
+ case TDB_FREE_MAGIC:
+ if (!tdb_check_free_record(tdb, off, &rec, hashes))
+ goto free;
+ break;
+ case TDB_RECOVERY_MAGIC:
+ if (recovery_start != off)
+ goto free;
+ found_recovery = true;
+ break;
+ default:
+ tdb->ecode = TDB_ERR_CORRUPT;
+ goto free;
+ }
+ }
+
+ /* Now, hashes should all be empty: each record exists and is referred
+ * to by one other. */
+ for (h = 0; h < 1+tdb->header.hash_size; h++) {
+ unsigned int i;
+ for (i = 0; i < BITMAP_BITS / CHAR_BIT; i++) {
+ if (hashes[h][i] != 0) {
+ tdb->ecode = TDB_ERR_CORRUPT;
+ goto free;
+ }
+ }
+ }
+
+ /* We must have found recovery area. */
+ if (recovery_start != 0 && !found_recovery)
+ goto free;
+
+ free(hashes);
+ tdb_unlockall(tdb);
+ return 0;
+
+free:
+ free(hashes);
+unlock:
+ tdb_unlockall(tdb);
+ return -1;
+}
+
+
+
+
+
+
projects / ccan / blobdiff