Arty has proposed merging
lp:~widelands-dev/widelands/bugfix-1805042-S2map-preloader-checks into
lp:widelands.
Commit message:
validity checks for S2 map headers to avoid crashes when preloading invalid S2
map files
Requested reviews:
Widelands Developers (widelands-dev)
Related bugs:
Bug #1805042 in widelands: "segfault when trying to preload invalid file"
https://bugs.launchpad.net/widelands/+bug/1805042
For more details, see:
https://code.launchpad.net/~widelands-dev/widelands/bugfix-1805042-S2map-preloader-checks/+merge/360762
--
Your team Widelands Developers is requested to review the proposed merge of
lp:~widelands-dev/widelands/bugfix-1805042-S2map-preloader-checks into
lp:widelands.
=== modified file 'src/map_io/s2map.cc'
--- src/map_io/s2map.cc 2018-04-11 06:55:01 +0000
+++ src/map_io/s2map.cc 2018-12-12 00:02:20 +0000
@@ -61,6 +61,29 @@
char bulk[2290]; // unknown
} /* size 2352 */;
+// Some basic checks to identify obviously invalid headers
+bool is_valid_header(const S2MapDescrHeader& header) {
+ if (strncmp(header.magic, "WORLD_V1.0", 10)) {
+ return false;
+ }
+ if (header.name[19]) {
+ return false;
+ }
+ if (header.w <= 0 || header.h <= 0) {
+ return false;
+ }
+ if (header.uses_world < 0 || header.uses_world > 2) {
+ return false;
+ }
+ if (header.nplayers < 0 || header.nplayers > 7) {
+ return false;
+ }
+ if (header.author[19]) {
+ return false;
+ }
+ return true;
+}
+
// TODO(unknown): the following bob types appear in S2 maps but are unknown
// Somebody who can run Settlers II please check them out
// 11 (0x0B)
@@ -400,9 +423,11 @@
}
/**
- * Load informational data of an S2 map
+ * Loads informational data of an S2 map.
+ * Throws exception if data is invalid.
*/
void S2MapLoader::load_s2mf_header(FileRead& fr) {
+ // no need to check file size: fr.data(..) already throws if the file is too small
S2MapDescrHeader header;
memcpy(&header, fr.data(sizeof(header)), sizeof(header));
@@ -414,6 +439,11 @@
header.h = swap_16(header.h);
#endif
+ // Check header validity to prevent unexpected crashes later
+ if (!is_valid_header(header)) {
+ throw wexception("invalid S2 file");
+ }
+
// don't really set size, but make the structures valid
map_.width_ = header.w;
map_.height_ = header.h;
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