From 716560b7f15b6e15b246c39c11eb8181d91c8662 Mon Sep 17 00:00:00 2001 From: Joey Hess Date: Wed, 12 Nov 2008 17:19:41 -0500 Subject: check for invalid utf-8, and toss it back to avoid crashes Since ikiwiki uses open :utf8, perl assumes that files contain valid utf-8. If it turns out to be malformed it may later crash while processing strings read from them, with 'Malformed UTF-8 character (fatal)'. As at least a quick fix, use utf8::valid as soon as data is read, and if it's not valid, call encode_utf8 on the string, thus clearing the utf-8 flag. This may cause follow-on encoding problems, but will avoid this crash, and the input file was broken anyway, so GIGO is a reasonable response. (I looked at calling decode_utf8 after, but it seemed to cause more trouble than it was worth. BTW, use open ':encoding(utf8)' avaoids this problem, but the corrupted data later causes Storable to crash when writing the index.) This is a quick fix, clearly imperfect: - It might be better to explicitly call decode_utf8 when reading files, rather than using the IO layer. - Data read other than by readfile() can still sneak in bad utf-8. While ikiwiki does very little file input not using it, stdin for the CGI would be one way. --- doc/security.mdwn | 9 +++++++++ 1 file changed, 9 insertions(+) (limited to 'doc') diff --git a/doc/security.mdwn b/doc/security.mdwn index 0841abf49..1bc7b9e60 100644 --- a/doc/security.mdwn +++ b/doc/security.mdwn @@ -407,3 +407,12 @@ discovered on 30 May 2008 and fixed the same day. ([[!cve CVE-2008-0169]]) I recommend upgrading to 2.48 immediatly if your wiki allows both password and openid logins. + +## Malformed UTF-8 DOS + +Feeding ikiwiki page sources containing certian forms of malformed UTF-8 +can cause it to crash. This can potentially be used for a denial of service +attack. + +intrigeri discovered this problem on 12 Nov 2008 and a patch put in place +later that day. -- cgit v1.2.3