-TODO
-====
-
-Security checks
----------------
-
-### Security history
-
-The only past security issues I could find in GNU gettext and po4a
-are:
-
-- [CVE-2004-0966](http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2004-0966),
- *i.e.* [Debian bug #278283](http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=278283):
- the autopoint and gettextize scripts in the GNU gettext package
- 1.14 and later versions, as used in Trustix Secure Linux 1.5
- through 2.1 and other operating systems, allows local users to
- overwrite files via a symlink attack on temporary files.
-- [CVE-2007-4462](http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2007-4462):
- `lib/Locale/Po4a/Po.pm` in po4a before 0.32 allows local users to
- overwrite arbitrary files via a symlink attack on the
- gettextization.failed.po temporary file.
-
-**FIXME**: check whether this plugin would have been a possible attack
-vector to exploit these vulnerabilities.
-
-Depending on my mood, the lack of found security issues can either
-indicate that there are none, or reveal that no-one ever bothered to
-find (and publish) them.
-
-### PO file features
-
-Can any sort of directives be put in po files that will cause mischief
-(ie, include other files, run commands, crash gettext, whatever)?
-
-> No [documented](http://www.gnu.org/software/gettext/manual/gettext.html#PO-Files)
-> directive is supposed to do so. [[--intrigeri]]
-
-### Running po4a on untrusted content
-
-Are there any security issues on running po4a on untrusted content?
-
-To say the least, this issue is not well covered, at least publicly:
-
-- the documentation does not talk about it;
-- grep'ing the source code for `security` or `trust` gives no answer.
-
-On the other hand, a po4a developer answered my questions in
-a convincing manner, stating that processing untrusted content was not
-an initial goal, and analysing in detail the possible issues.
-
-#### Already checked
-
-- the core (`Po.pm`, `Transtractor.pm`) should be safe
-- po4a source code was fully checked for other potential symlink
- attacks, after discovery of one such issue
-- the only external program run by the core is `diff`, in `Po.pm` (in
- parts of its code we don't use)
-- `Locale::gettext`: only used to display translated error messages
-- Nicolas François "hopes" `DynaLoader` is safe, and has "no reason to
- think that `Encode` is not safe"
-- Nicolas François has "no reason to think that `Encode::Guess` is not
- safe". The po plugin nevertheless avoids using it by defining the
- input charset (`file_in_charset`) before asking `Transtractor` to
- read any file. NB: this hack depends on po4a internals to stay
- the same.
-
-#### To be checked
-
-##### Locale::Po4a modules
-
-The modules we want to use have to be checked, as not all are safe
-(e.g. the LaTeX module's behaviour is changed by commands included in
-the content); they may use regexps generated from the content.
-
-`Chooser.pm` only loads the plugin we tell it too: currently, this
-means the `Text` module only.
-
-`Text` module (I checked the CVS version):
-
-- it does not run any external program
-- only `do_paragraph()` builds regexp's that expand untrusted
- variables; they seem safe to me, but someone more expert than me
- will need to check. Joey?
-
- > Freaky code, but seems ok due to use of `quotementa`.
-
-##### Text::WrapI18N
-
-`Text::WrapI18N` can cause DoS (see the
-[Debian bug #470250](http://bugs.debian.org/470250)), but it is
-optional and we do not need the features it provides.
-
-It is loaded if available by `Locale::Po4a::Common`; looking at the
-code, I'm not sure we can prevent this at all, but maybe some symbol
-table manipulation tricks could work; overriding
-`Locale::Po4a::Common::wrapi18n` may be easier. I'm no expert at all
-in this field. Joey? [[--intrigeri]]
-
-> Update: Nicolas François suggests we add an option to po4a to
-> disable it. It would do the trick, but only for people running
-> a brand new po4a (probably too late for Lenny). Anyway, this option
-> would have to take effect in a `BEGIN` / `eval` that I'm not
-> familiar with. I can learn and do it, in case no Perl wizard
-> volunteers to provide the po4a patch. [[--intrigeri]]
-
->> That doesn't really need to be in a BEGIN. This patch moves it to
->> `import`, and makes this disable wrap18n:
->> `use Locale::Po4a::Common q{nowrapi18n}` --[[Joey]]
-
-<pre>
---- /usr/share/perl5/Locale/Po4a/Common.pm 2008-07-21 14:54:52.000000000 -0400
-+++ Common.pm 2008-11-11 18:27:34.000000000 -0500
-@@ -30,8 +30,16 @@
- use strict;
- use warnings;
-
--BEGIN {
-- if (eval { require Text::WrapI18N }) {
-+sub import {
-+ my $class=shift;
-+ my $wrapi18n=1;
-+ if ($_[0] eq 'nowrapi18n') {
-+ shift;
-+ $wrapi18n=0;
-+ }
-+ $class->export_to_level(1, $class, @_);
-+
-+ if ($wrapi18n && eval { require Text::WrapI18N }) {
-
- # Don't bother determining the wrap column if we cannot wrap.
- my $col=$ENV{COLUMNS};
-</pre>
-
-##### Term::ReadKey
-
-`Term::ReadKey` is not a hard dependency in our case, *i.e.* po4a
-works nicely without it. But the po4a Debian package recommends
-`libterm-readkey-perl`, so it will probably be installed on most
-systems using the po plugin.
-
-If `$ENV{COLUMNS}` is not set, `Locale::Po4a::Common` uses
-`Term::ReadKey::GetTerminalSize()` to get the terminal size. How safe
-is this?
-
-Part of `Term::ReadKey` is written in C. Depending on the runtime
-platform, this function use ioctl, environment, or C library function
-calls, and may end up running the `resize` command (without
-arguments).
-
-IMHO, using Term::ReadKey has too far reaching implications for us to
-be able to guarantee anything wrt. security. Since it is anyway of no
-use in our case, I suggest we define `ENV{COLUMNS}` before loading
-`Locale::Po4a::Common`, just to be on the safe side. Joey?
-[[--intrigeri]]
-
-> Update: adding an option to disable `Text::WrapI18N`, as Nicolas
-> François suggested, would as a bonus disable `Term::ReadKey`
-> as well. [[--intrigeri]]
-
-### msgmerge
-
-`refreshpofiles()` runs this external program. A po4a developer
-answered he does "not expect any security issues from it".
-
-### Fuzzing input
-
-I was not able to find any public information about gettext or po4a
-having been tested with a fuzzing program, such as `zzuf` or `fusil`.
-Moreover, some gettext parsers seem to be quite
-[easy to crash](http://fusil.hachoir.org/trac/browser/trunk/fuzzers/fusil-gettext),
-so it might be useful to bang msgmerge/po4a's heads against such
-a program in order to easily detect some of the most obvious DoS.
-[[--intrigeri]]
-
-> po4a was not fuzzy-tested, but according to one of its developers,
-> "it would be really appreciated". [[--intrigeri]]
-
-Test conditions:
-
-- a 21M file containing 100 concatenated copies of all the files in my
- `/usr/share/common-licenses/`; I had no existing PO file or
- translated versions at hand, which renders these tests
- quite incomplete.
-- po4a was the Debian 0.34-2 package; the same tests were also run
- after replacing the `Text` module with the CVS one (the core was not
- changed in CVS since 0.34-2 was released), without any significant
- difference in the results.
-- Perl 5.10.0-16
-
-#### po4a-gettextize
-
-`po4a-gettextize` uses more or less the same po4a features as our
-`refreshpot` function.
-
-Without specifying an input charset, zzuf'ed `po4a-gettextize` quickly
-errors out, complaining it was not able to detect the input charset;
-it leaves no incomplete file on disk.
-
-So I had to pretend the input was in UTF-8, as does the po plugin.
-
-Two ways of crashing were revealed by this command-line:
-
- zzuf -vc -s 0:100 -r 0.1:0.5 \
- po4a-gettextize -f text -o markdown -M utf-8 -L utf-8 \
- -m LICENSES >/dev/null
-
-They are:
-
- Malformed UTF-8 character (UTF-16 surrogate 0xdcc9) in substitution iterator at /usr/share/perl5/Locale/Po4a/Po.pm line 1443.
- Malformed UTF-8 character (fatal) at /usr/share/perl5/Locale/Po4a/Po.pm line 1443.
-
-and
-
- Malformed UTF-8 character (UTF-16 surrogate 0xdcec) in substitution (s///) at /usr/share/perl5/Locale/Po4a/Po.pm line 1443.
- Malformed UTF-8 character (fatal) at /usr/share/perl5/Locale/Po4a/Po.pm line 1443.
-
-Perl seems to exit cleanly, and an incomplete PO file is written on
-disk. I not sure whether if this is a bug in Perl or in `Po.pm`.
-
-> It's fairly standard perl behavior when fed malformed utf-8. As long as it doesn't
-> crash ikiwiki, it's probably acceptable. Ikiwiki can do some similar things itself when fed malformed utf-8 (doesn't crash tho) --[[Joey]]
-
-#### po4a-translate
-
-`po4a-translate` uses more or less the same po4a features as our
-`filter` function.
-
-Without specifying an input charset, same behaviour as
-`po4a-gettextize`, so let's specify UTF-8 as input charset as of now.
-
- zzuf -cv \
- po4a-translate -d -f text -o markdown -M utf-8 -L utf-8 \
- -k 0 -m LICENSES -p LICENSES.fr.po -l test.fr
-
-... prints tons of occurences of the following error, but a complete
-translated document is written (obviously with some weird chars
-inside):