1 files changed, 351 insertions, 0 deletions
diff --git a/lib/tdb/common/rescue.c b/lib/tdb/common/rescue.c
new file mode 100644
index 0000000..7a85ebc
--- /dev/null
+++ b/lib/tdb/common/rescue.c
@@ -0,0 +1,351 @@
+ /*
+   Unix SMB/CIFS implementation.
+
+   trivial database library, rescue attempt code.
+
+   Copyright (C) Rusty Russell		   2012
+
+     ** 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 <assert.h>
+
+
+struct found {
+	tdb_off_t head; /* 0 -> invalid. */
+	struct tdb_record rec;
+	TDB_DATA key;
+	bool in_hash;
+	bool in_free;
+};
+
+struct found_table {
+	/* As an ordered array (by head offset). */
+	struct found *arr;
+	unsigned int num, max;
+};
+
+static bool looks_like_valid_record(struct tdb_context *tdb,
+				    tdb_off_t off,
+				    const struct tdb_record *rec,
+				    TDB_DATA *key)
+{
+	unsigned int hval;
+
+	if (rec->magic != TDB_MAGIC)
+		return false;
+
+	if (rec->key_len + rec->data_len > rec->rec_len)
+		return false;
+
+	if (rec->rec_len % TDB_ALIGNMENT)
+		return false;
+
+	/* Next pointer must make some sense. */
+	if (rec->next > 0 && rec->next < TDB_DATA_START(tdb->hash_size))
+		return false;
+
+	if (tdb_oob(tdb, rec->next, sizeof(*rec), 1))
+		return false;
+
+	key->dsize = rec->key_len;
+	key->dptr = tdb_alloc_read(tdb, off + sizeof(*rec), key->dsize);
+	if (!key->dptr)
+		return false;
+
+	hval = tdb->hash_fn(key);
+	if (hval != rec->full_hash) {
+		free(key->dptr);
+		return false;
+	}
+
+	/* Caller frees up key->dptr */
+	return true;
+}
+
+static bool add_to_table(struct found_table *found,
+			 tdb_off_t off,
+			 struct tdb_record *rec,
+			 TDB_DATA key)
+{
+	if (found->num + 1 > found->max) {
+		struct found *new;
+		found->max = (found->max ? found->max * 2 : 128);
+		new = realloc(found->arr, found->max * sizeof(found->arr[0]));
+		if (!new)
+			return false;
+		found->arr = new;
+	}
+
+	found->arr[found->num].head = off;
+	found->arr[found->num].rec = *rec;
+	found->arr[found->num].key = key;
+	found->arr[found->num].in_hash = false;
+	found->arr[found->num].in_free = false;
+
+	found->num++;
+	return true;
+}
+
+static bool walk_record(struct tdb_context *tdb,
+			const struct found *f,
+			void (*walk)(TDB_DATA, TDB_DATA, void *private_data),
+			void *private_data)
+{
+	TDB_DATA data;
+
+	data.dsize = f->rec.data_len;
+	data.dptr = tdb_alloc_read(tdb,
+				   f->head + sizeof(f->rec) + f->rec.key_len,
+				   data.dsize);
+	if (!data.dptr) {
+		if (tdb->ecode == TDB_ERR_OOM)
+			return false;
+		/* I/O errors are expected. */
+		return true;
+	}
+
+	walk(f->key, data, private_data);
+	free(data.dptr);
+	return true;
+}
+
+/* First entry which has offset >= this one. */
+static unsigned int find_entry(struct found_table *found, tdb_off_t off)
+{
+	unsigned int start = 0, end = found->num;
+
+	while (start < end) {
+		/* We can't overflow here. */
+		unsigned int mid = (start + end) / 2;
+
+		if (off < found->arr[mid].head) {
+			end = mid;
+		} else if (off > found->arr[mid].head) {
+			start = mid + 1;
+		} else {
+			return mid;
+		}
+	}
+
+	assert(start == end);
+	return end;
+}
+
+static void found_in_hashchain(struct found_table *found, tdb_off_t head)
+{
+	unsigned int match;
+
+	match = find_entry(found, head);
+	if (match < found->num && found->arr[match].head == head) {
+		found->arr[match].in_hash = true;
+	}
+}
+
+static void mark_free_area(struct found_table *found, tdb_off_t head,
+			   tdb_len_t len)
+{
+	unsigned int match;
+
+	match = find_entry(found, head);
+	/* Mark everything within this free entry. */
+	while (match < found->num) {
+		if (found->arr[match].head >= head + len) {
+			break;
+		}
+		found->arr[match].in_free = true;
+		match++;
+	}
+}
+
+static int cmp_key(const void *a, const void *b)
+{
+	const struct found *fa = a, *fb = b;
+
+	if (fa->key.dsize < fb->key.dsize) {
+		return -1;
+	} else if (fa->key.dsize > fb->key.dsize) {
+		return 1;
+	}
+	return memcmp(fa->key.dptr, fb->key.dptr, fa->key.dsize);
+}
+
+static bool key_eq(TDB_DATA a, TDB_DATA b)
+{
+	return a.dsize == b.dsize
+		&& memcmp(a.dptr, b.dptr, a.dsize) == 0;
+}
+
+static void free_table(struct found_table *found)
+{
+	unsigned int i;
+
+	for (i = 0; i < found->num; i++) {
+		free(found->arr[i].key.dptr);
+	}
+	free(found->arr);
+}
+
+static void logging_suppressed(struct tdb_context *tdb,
+			       enum tdb_debug_level level, const char *fmt, ...)
+{
+}
+
+_PUBLIC_ int tdb_rescue(struct tdb_context *tdb,
+			void (*walk)(TDB_DATA, TDB_DATA, void *private_data),
+			void *private_data)
+{
+	struct found_table found = { NULL, 0, 0 };
+	tdb_off_t h, off, i;
+	tdb_log_func oldlog = tdb->log.log_fn;
+	struct tdb_record rec;
+	TDB_DATA key;
+	bool locked;
+
+	/* Read-only databases use no locking at all: it's best-effort.
+	 * We may have a write lock already, so skip that case too. */
+	if (tdb->read_only || tdb->allrecord_lock.count != 0) {
+		locked = false;
+	} else {
+		if (tdb_lockall_read(tdb) == -1)
+			return -1;
+		locked = true;
+	}
+
+	/* Make sure we know true size of the underlying file. */
+	tdb_oob(tdb, tdb->map_size, 1, 1);
+
+	/* Suppress logging, since we anticipate errors. */
+	tdb->log.log_fn = logging_suppressed;
+
+	/* Now walk entire db looking for records. */
+	for (off = TDB_DATA_START(tdb->hash_size);
+	     off < tdb->map_size;
+	     off += TDB_ALIGNMENT) {
+		if (tdb->methods->tdb_read(tdb, off, &rec, sizeof(rec),
+					   DOCONV()) == -1)
+			continue;
+
+		if (looks_like_valid_record(tdb, off, &rec, &key)) {
+			if (!add_to_table(&found, off, &rec, key)) {
+				goto oom;
+			}
+		}
+	}
+
+	/* Walk hash chains to positive vet. */
+	for (h = 0; h < 1+tdb->hash_size; h++) {
+		bool slow_chase = false;
+		tdb_off_t slow_off = FREELIST_TOP + h*sizeof(tdb_off_t);
+
+		if (tdb_ofs_read(tdb, FREELIST_TOP + h*sizeof(tdb_off_t),
+				 &off) == -1)
+			continue;
+
+		while (off && off != slow_off) {
+			if (tdb->methods->tdb_read(tdb, off, &rec, sizeof(rec),
+						   DOCONV()) != 0) {
+				break;
+			}
+
+			/* 0 is the free list, rest are hash chains. */
+			if (h == 0) {
+				/* Don't mark garbage as free. */
+				if (rec.magic != TDB_FREE_MAGIC) {
+					break;
+				}
+				mark_free_area(&found, off,
+					       sizeof(rec) + rec.rec_len);
+			} else {
+				found_in_hashchain(&found, off);
+			}
+
+			off = rec.next;
+
+			/* Loop detection using second pointer at half-speed */
+			if (slow_chase) {
+				/* First entry happens to be next ptr */
+				tdb_ofs_read(tdb, slow_off, &slow_off);
+			}
+			slow_chase = !slow_chase;
+		}
+	}
+
+	/* Recovery area: must be marked as free, since it often has old
+	 * records in there! */
+	if (tdb_ofs_read(tdb, TDB_RECOVERY_HEAD, &off) == 0 && off != 0) {
+		if (tdb->methods->tdb_read(tdb, off, &rec, sizeof(rec),
+					   DOCONV()) == 0) {
+			mark_free_area(&found, off, sizeof(rec) + rec.rec_len);
+		}
+	}
+
+	/* Now sort by key! */
+	if (found.arr != NULL) {
+		qsort(found.arr, found.num, sizeof(found.arr[0]), cmp_key);
+	}
+
+	for (i = 0; (found.arr != NULL) && i < found.num; ) {
+		unsigned int num, num_in_hash = 0;
+
+		/* How many are identical? */
+		for (num = 0; num < found.num - i; num++) {
+			if (!key_eq(found.arr[i].key, found.arr[i+num].key)) {
+				break;
+			}
+			if (found.arr[i+num].in_hash) {
+				if (!walk_record(tdb, &found.arr[i+num],
+						 walk, private_data))
+					goto oom;
+				num_in_hash++;
+			}
+		}
+		assert(num);
+
+		/* If none were in the hash, we print any not in free list. */
+		if (num_in_hash == 0) {
+			unsigned int j;
+
+			for (j = i; j < i + num; j++) {
+				if (!found.arr[j].in_free) {
+					if (!walk_record(tdb, &found.arr[j],
+							 walk, private_data))
+						goto oom;
+				}
+			}
+		}
+
+		i += num;
+	}
+
+	tdb->log.log_fn = oldlog;
+	if (locked) {
+		tdb_unlockall_read(tdb);
+	}
+	return 0;
+
+oom:
+	tdb->log.log_fn = oldlog;
+	tdb->ecode = TDB_ERR_OOM;
+	TDB_LOG((tdb, TDB_DEBUG_ERROR, "tdb_rescue: failed allocating\n"));
+	free_table(&found);
+	if (locked) {
+		tdb_unlockall_read(tdb);
+	}
+	return -1;
+}