ccan/tdb: tdb_check() function.

ccan/tdb/check.c

+ /* 
+   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;
+}
+
+		
+
+	
+
+	

ccan/tdb/tdb.h

@@ -148,6 +148,9 @@ void tdb_add_flags(struct tdb_context *tdb, unsigned flag);
 void tdb_remove_flags(struct tdb_context *tdb, unsigned flag);
 void tdb_enable_seqnum(struct tdb_context *tdb);
 void tdb_increment_seqnum_nonblock(struct tdb_context *tdb);
+int tdb_check(struct tdb_context *tdb,
+	      int (*check)(TDB_DATA key, TDB_DATA data, void *private),
+	      void *private);
 
 /* Low level locking functions: use with care */
 int tdb_chainlock(struct tdb_context *tdb, TDB_DATA key);

ccan/tdb/test/run-check.c

+#define _XOPEN_SOURCE 500
+#include "tdb/tdb.h"
+#include "tdb/io.c"
+#include "tdb/tdb.c"
+#include "tdb/lock.c"
+#include "tdb/freelist.c"
+#include "tdb/traverse.c"
+#include "tdb/transaction.c"
+#include "tdb/error.c"
+#include "tdb/open.c"
+#include "tdb/check.c"
+#include "tap/tap.h"
+#include <stdlib.h>
+#include <err.h>
+
+int main(int argc, char *argv[])
+{
+	struct tdb_context *tdb;
+	TDB_DATA key, data;
+
+	plan_tests(9);
+	tdb = tdb_open("/tmp/test5.tdb", 1, TDB_CLEAR_IF_FIRST,
+		       O_CREAT|O_TRUNC|O_RDWR, 0600);
+
+	ok1(tdb);
+	ok1(tdb_check(tdb, NULL, NULL) == 0);
+	
+	key.dsize = strlen("hi");
+	key.dptr = (void *)"hi";
+	data.dsize = strlen("world");
+	data.dptr = (void *)"world";
+
+	ok1(tdb_store(tdb, key, data, TDB_INSERT) == 0);
+	ok1(tdb_check(tdb, NULL, NULL) == 0);
+	tdb_close(tdb);
+
+	tdb = tdb_open("/tmp/test5.tdb", 1024, 0, O_RDWR, 0);
+	ok1(tdb);
+	ok1(tdb_check(tdb, NULL, NULL) == 0);
+	tdb_close(tdb);
+
+	tdb = tdb_open("test/tdb.corrupt", 1024, 0, O_RDWR, 0);
+	ok1(tdb);
+	ok1(tdb_check(tdb, NULL, NULL) == -1);
+	ok1(tdb_error(tdb) == TDB_ERR_CORRUPT);
+	tdb_close(tdb);
+
+	return exit_status();
+}

ccan/tdb/test/run-corrupt.c

+#define _XOPEN_SOURCE 500
+#include "tdb/tdb.h"
+#include "tdb/io.c"
+#include "tdb/tdb.c"
+#include "tdb/lock.c"
+#include "tdb/freelist.c"
+#include "tdb/traverse.c"
+#include "tdb/transaction.c"
+#include "tdb/error.c"
+#include "tdb/open.c"
+#include "tdb/check.c"
+#include "tap/tap.h"
+#include <stdlib.h>
+#include <err.h>
+
+static int check(TDB_DATA key, TDB_DATA data, void *private)
+{
+	unsigned int *sizes = private;
+
+	if (key.dsize > strlen("hello"))
+		return -1;
+	if (memcmp(key.dptr, "hello", key.dsize) != 0)
+		return -1;
+
+	if (data.dsize != strlen("world"))
+		return -1;
+	if (memcmp(data.dptr, "world", data.dsize) != 0)
+		return -1;
+
+	sizes[0] += key.dsize;
+	sizes[1] += data.dsize;
+	return 0;
+}
+
+int main(int argc, char *argv[])
+{
+	struct tdb_context *tdb;
+	TDB_DATA key, data;
+	unsigned int i, verifiable, corrupt, sizes[2], dsize, ksize;
+
+	plan_tests(2);
+	tdb = tdb_open("/tmp/test6.tdb", 2, TDB_CLEAR_IF_FIRST,
+		       O_CREAT|O_TRUNC|O_RDWR, 0600);
+
+	if (!tdb)
+		abort();
+	ok1(tdb_check(tdb, NULL, NULL) == 0);
+	
+	key.dptr = (void *)"hello";
+	data.dsize = strlen("world");
+	data.dptr = (void *)"world";
+
+	/* Key and data size respectively. */
+	dsize = ksize = 0;
+
+	/* 5 keys in hash size 2 means we'll have multichains. */
+	for (key.dsize = 1; key.dsize <= 5; key.dsize++) {
+		ksize += key.dsize;
+		dsize += data.dsize;
+		if (tdb_store(tdb, key, data, TDB_INSERT) != 0)
+			abort();
+	}
+
+	/* This is how many bytes we expect to be verifiable. */
+	/* From the file header. */
+	verifiable = strlen(TDB_MAGIC_FOOD) + 1
+		+ 2 * sizeof(uint32_t) + 2 * sizeof(tdb_off_t);
+	/* From the free list chain and hash chains. */
+	verifiable += 3 * sizeof(tdb_off_t);
+	/* From the record headers & tailer */
+	verifiable += 5 * (sizeof(struct list_struct) + sizeof(uint32_t));
+	/* The free block: we ignore datalen, keylen, full_hash. */
+	verifiable += sizeof(struct list_struct) - 3*sizeof(uint32_t) +
+		sizeof(uint32_t);
+	/* Our check function verifies the key and data. */
+	verifiable += ksize + dsize;
+
+	/* Flip one bit at a time, make sure it detects verifiable bytes. */
+	for (i = 0, corrupt = 0; i < tdb->map_size * CHAR_BIT; i++) {
+		bit_flip(tdb->map_ptr, i);
+		memset(sizes, 0, sizeof(sizes));
+		if (tdb_check(tdb, check, sizes) != 0)
+			corrupt++;
+		else if (sizes[0] != ksize || sizes[1] != dsize)
+			corrupt++;
+		bit_flip(tdb->map_ptr, i);
+	}
+	ok(corrupt == verifiable * CHAR_BIT, "corrupt %u should be %u",
+	   corrupt, verifiable * CHAR_BIT);
+	tdb_close(tdb);
+
+	return exit_status();
+}