Basic checks on file to ensure it's an mdb database. bug # 587739

src/libmdb/catalog.c

@@ -71,6 +71,8 @@ int type;
  /* mdb_table_dump(&msysobj); */
 
  table = mdb_read_table(&msysobj);
+ if (!table) return NULL;
+
  mdb_read_columns(table);
 
  mdb_bind_column(table, 1, parentid);

src/libmdb/file.c

@@ -106,18 +106,25 @@ MdbFile *f;
 		fprintf(stderr,"Couldn't open file %s\n",f->filename); 
 		return NULL;
 	}
-	f->refs++;
 	if (!mdb_read_pg(mdb, 0)) {
 		fprintf(stderr,"Couldn't read first page.\n");
 		return NULL;
 	}
+	if (mdb->pg_buf[0] != 0) {
+		close(f->fd);
+		return NULL; 
+	}
 	f->jet_version = mdb_pg_get_int32(mdb, 0x14);
 	if (IS_JET4(mdb)) {
 		mdb->fmt = &MdbJet4Constants;
-	} else {
+	} else if (IS_JET3(mdb)) {
 		mdb->fmt = &MdbJet3Constants;
+	} else {
+		fprintf(stderr,"Unknown Jet version.\n");
+		return NULL; 
 	}
 
+	f->refs++;
 	return mdb;
 }
 MdbHandle *mdb_open(char *filename)

src/libmdb/table.c

@@ -55,6 +55,8 @@ int rownum, row_start, row_end;
 	table = mdb_alloc_tabledef(entry);
 
 	mdb_read_pg(mdb, entry->table_pg);
+	if (mdb->pg_buf[0] != 0x02) return NULL; /* not a valid table def page */
+
 	len = mdb_pg_get_int16(mdb,8);
 
 	table->num_rows = mdb_pg_get_int32(mdb, fmt->tab_num_rows_offset);