ldb: baseinfo pack format check on init

We will be adding a new packing format in forthcoming commits and there
may be more versions in the future. We need to make sure the database
contains records in a format we know how to read and write.
Done by fetching the @BASEINFO record and reading the first 4
bytes which contain the packing format version.

NOTE: Configure with --abi-check-disable to build this commit. This
patch is part of a set of LDB ABI changes, and the version update is
done on the last commit.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=13977

Signed-off-by: Aaron Haslett <aaronhaslett@catalyst.net.nz>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>
Reviewed-by: Gary Lockyer <gary@catalyst.net.nz>
(backported from commit 474e55523224430781ed22aa2d0c8a474306e794)

5 files changed, 71 insertions, 9 deletions

diff --git a/lib/ldb/common/ldb_pack.c b/lib/ldb/common/ldb_pack.c
index 448c577ae1b..286803f0b41 100644
--- a/lib/ldb/common/ldb_pack.c
+++ b/lib/ldb/common/ldb_pack.c
@@ -33,12 +33,6 @@
 
 #include "ldb_private.h"
 
-/* change this if the data format ever changes */
-#define LDB_PACKING_FORMAT 0x26011967
-
-/* old packing formats */
-#define LDB_PACKING_FORMAT_NODN 0x26011966
-
 /* use a portable integer format */
 static void put_uint32(uint8_t *p, int ofs, unsigned int val)
 {
@@ -229,7 +223,7 @@ int ldb_unpack_data_only_attr_list_flags(struct ldb_context *ldb,
 	size_t remaining;
 	size_t dn_len;
 	unsigned int i, j;
-	unsigned format;
+	uint32_t format;
 	unsigned int nelem = 0;
 	size_t len;
 	unsigned int found = 0;
@@ -247,7 +241,10 @@ int ldb_unpack_data_only_attr_list_flags(struct ldb_context *ldb,
 		goto failed;
 	}
 
-	format = pull_uint32(p, 0);
+	if (ldb_unpack_get_format(data, &format) != LDB_SUCCESS) {
+		errno = EIO;
+		goto failed;
+	}
 	message->num_elements = pull_uint32(p, 4);
 	p += 8;
 	if (nb_elements_in_db) {
@@ -504,6 +501,16 @@ failed:
 	return -1;
 }
 
+int ldb_unpack_get_format(const struct ldb_val *data,
+			  uint32_t *pack_format_version)
+{
+	if (data->length < 4) {
+		return LDB_ERR_OPERATIONS_ERROR;
+	}
+	*pack_format_version = pull_uint32(data->data, 0);
+	return LDB_SUCCESS;
+}
+
 /*
  * Unpack a ldb message from a linear buffer in ldb_val
  *
diff --git a/lib/ldb/include/ldb_module.h b/lib/ldb/include/ldb_module.h
index c73fc37f3aa..8c47082690b 100644
--- a/lib/ldb/include/ldb_module.h
+++ b/lib/ldb/include/ldb_module.h
@@ -561,11 +561,20 @@ int ldb_unpack_data_only_attr_list_flags(struct ldb_context *ldb,
 					 unsigned int flags,
 					 unsigned int *nb_elements_in_db);
 
+int ldb_unpack_get_format(const struct ldb_val *data,
+			  uint32_t *pack_format_version);
+
 #define LDB_UNPACK_DATA_FLAG_NO_DATA_ALLOC   0x0001
 #define LDB_UNPACK_DATA_FLAG_NO_DN           0x0002
 #define LDB_UNPACK_DATA_FLAG_NO_VALUES_ALLOC 0x0004
 #define LDB_UNPACK_DATA_FLAG_NO_ATTRS        0x0008
 
+/* In-use packing formats */
+#define LDB_PACKING_FORMAT 0x26011967
+
+/* Old packing formats */
+#define LDB_PACKING_FORMAT_NODN 0x26011966
+
 /**
  Forces a specific ldb handle to use the global event context.
 
diff --git a/lib/ldb/ldb_tdb/ldb_cache.c b/lib/ldb/ldb_tdb/ldb_cache.c
index 1856fb13877..eb14a74e0a1 100644
--- a/lib/ldb/ldb_tdb/ldb_cache.c
+++ b/lib/ldb/ldb_tdb/ldb_cache.c
@@ -387,6 +387,13 @@ int ltdb_cache_reload(struct ldb_module *module)
 	ltdb_cache_free(module);
 	return ltdb_cache_load(module);
 }
+static int get_pack_format_version(struct ldb_val key,
+				   struct ldb_val data,
+				   void *private_data)
+{
+	uint32_t *v = (uint32_t *) private_data;
+	return ldb_unpack_get_format(&data, v);
+}
 
 /*
   load the cache records
@@ -402,6 +409,9 @@ int ltdb_cache_load(struct ldb_module *module)
 	const struct ldb_schema_attribute *a;
 	bool have_write_txn = false;
 	int r;
+	uint32_t pack_format_version;
+	struct ldb_val key_ldb;
+	struct TDB_DATA key;
 
 	ldb = ldb_module_get_ctx(module);
 
@@ -425,7 +435,40 @@ int ltdb_cache_load(struct ldb_module *module)
 	if (r != LDB_SUCCESS) {
 		goto failed;
 	}
-	r= ltdb_search_dn1(module, baseinfo_dn, baseinfo, 0);
+
+	key = ltdb_key_dn(module, baseinfo, baseinfo_dn);
+	if (!key.dptr) {
+		goto failed_and_unlock;
+	}
+
+	key_ldb = (struct ldb_val){
+		.data = key.dptr,
+		.length = key.dsize
+	};
+
+	/* Read packing format from first 4 bytes of @BASEINFO record */
+	r = ltdb->kv_ops->fetch_and_parse(ltdb, key_ldb,
+					  get_pack_format_version,
+					  &pack_format_version);
+
+	if (r != LDB_ERR_NO_SUCH_OBJECT) {
+		if (r != LDB_SUCCESS) {
+			goto failed_and_unlock;
+		}
+
+		/* Make sure the database has the right format */
+		if (pack_format_version != ltdb->pack_format_version) {
+			ldb_debug(ldb, LDB_DEBUG_ERROR,
+				  "Unexpected packing format. "
+				  "Expected: %#010x, Got: %#010x",
+				  pack_format_version,
+				  ltdb->pack_format_version);
+			goto failed_and_unlock;
+		}
+	}
+
+	/* Now fetch the whole @BASEINFO record */
+	r = ltdb_search_dn1(module, baseinfo_dn, baseinfo, 0);
 	if (r != LDB_SUCCESS && r != LDB_ERR_NO_SUCH_OBJECT) {
 		goto failed_and_unlock;
 	}
diff --git a/lib/ldb/ldb_tdb/ldb_tdb.c b/lib/ldb/ldb_tdb/ldb_tdb.c
index 337e7d2ee22..e3f552805c2 100644
--- a/lib/ldb/ldb_tdb/ldb_tdb.c
+++ b/lib/ldb/ldb_tdb/ldb_tdb.c
@@ -2272,6 +2272,8 @@ int init_store(struct ltdb_private *ltdb,
 
 	ltdb->sequence_number = 0;
 
+	ltdb->pack_format_version = LDB_PACKING_FORMAT;
+
 	ltdb->pid = getpid();
 
 	ltdb->module = ldb_module_new(ldb, ldb, name, &ltdb_ops);
diff --git a/lib/ldb/ldb_tdb/ldb_tdb.h b/lib/ldb/ldb_tdb/ldb_tdb.h
index 2896c6376b8..6c50e2856dc 100644
--- a/lib/ldb/ldb_tdb/ldb_tdb.h
+++ b/lib/ldb/ldb_tdb/ldb_tdb.h
@@ -42,6 +42,7 @@ struct ltdb_private {
 	unsigned int connect_flags;
 	
 	unsigned long long sequence_number;
+	uint32_t pack_format_version;
 
 	/* the low level tdb seqnum - used to avoid loading BASEINFO when
 	   possible */