It depends on the Perl `Locale::Po4a::Po` library (`apt-get install po4a`).
-[[!toc]]
+[[!toc levels=2]]
Introduction
============
Templates
---------
+When `po_link_to` is not set to `negotiated`, one should replace some
+occurrences of `BASEURL` with `HOMEPAGEURL` to get correct links to
+the wiki homepage.
+
The `ISTRANSLATION` and `ISTRANSLATABLE` variables can be used to
display things only on translatable or translation pages.
been declared as being translatable, the needed POT and PO files are
created, and the PO files are checked into version control.
-Discussion pages
-----------------
+Discussion pages and other sub-pages
+------------------------------------
Discussion should happen in the language in which the pages are
written for real, *i.e.* the "master" one. If discussion pages are
enabled, "slave" pages therefore link to the "master" page's
discussion page.
+Likewise, "slave" pages are not supposed to have sub-pages;
+[[WikiLinks|wikilink]] that appear on a "slave" page therefore link to
+the master page's sub-pages.
+
Translating
-----------
If [[tips/untrusted_git_push]] is setup, one can edit the PO files in one's
preferred `$EDITOR`, without needing to be online.
+Markup languages support
+------------------------
+
+Markdown is well supported. Some other markup languages supported by
+ikiwiki mostly work, but some pieces of syntax are not rendered
+correctly on the slave pages:
+
+* [[reStructuredText|rst]]: anonymous hyperlinks and internal
+ cross-references
+* [[wikitext]]: conversion of newlines to paragraphs
+* [[creole]]: verbatim text is wrapped, tables are broken
+* [[html]] and LaTeX: not supported yet; the dedicated po4a modules
+ could be used to support them, but they would need a security audit
+* other markup languages have not been tested.
+
+
TODO
====
(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.
+> 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.
->
-> I'll ask their opinion to the po4a maintainers.
->
-> I'm not in a position to audit the code, but I had a look anyway:
->
-> - no use of `system()`, `exec()` or backticks in `Locale::Po4a`; are
-> there any other way to run external programs in Perl?
-> - a symlink attack vulnerability was already discovered, so I "hope"
-> the code has been checked to find some more already
-> - the po4a parts we are using themselves use the following Perl
-> modules: `DynaLoader`, `Encode`, `Encode::Guess`,
-> `Text::WrapI18N`, `Locale::gettext` (`bindtextdomain`,
-> `textdomain`, `gettext`, `dgettext`)
->
-> --[[intrigeri]]
+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".
+
+### msgfmt
+
+`isvalidpo()` runs this external program. Its security should be checked.
### Fuzzing input
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 gettext/po4a's heads against such
+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):
+
+ Use of uninitialized value in string ne at /usr/share/perl5/Locale/Po4a/TransTractor.pm line 854.
+ Use of uninitialized value in string ne at /usr/share/perl5/Locale/Po4a/TransTractor.pm line 840.
+ Use of uninitialized value in pattern match (m//) at /usr/share/perl5/Locale/Po4a/Po.pm line 1002.
+
+While:
+
+ zzuf -cv -s 0:10 -r 0.001:0.3 \
+ po4a-translate -d -f text -o markdown -M utf-8 -L utf-8 \
+ -k 0 -m LICENSES -p LICENSES.fr.po -l test.fr
+
+... seems to lose the fight, at the `readpo(LICENSES.fr.po)` step,
+against some kind of infinite loop, deadlock, or any similar beast.
+It does not seem to eat memory, though.
+
+Whatever format module is used does not change anything. This is thus
+probably a bug in po4a's core or in a lib it depends on.
+
+The sub `read`, in `TransTractor.pm`, seems to be a good debugging
+starting point.
+
+#### msgmerge
+
+`msgmerge` is run in our `refreshpofiles` function. I did not manage
+to crash it with `zzuf`.
+
gettext/po4a rough corners
--------------------------
a PO update, that changes bla.fr.po in repo2; etc.; quickly fixed in
`629968fc89bced6727981c0a1138072631751fee`, by disabling references
in Pot files. Using `Locale::Po4a::write_if_needed` might be
- a cleaner solution.
+ a cleaner solution. (warning: this function runs the external
+ `diff` program, have to check security)
- new translations created in the web interface must get proper
charset/encoding gettext metadata, else the next automatic PO update
removes any non-ascii chars; possible solution: put such metadata
into the Pot file, and let it propagate; should be fixed in
`773de05a7a1ee68d2bed173367cf5e716884945a`, time will tell.
-Misc. improvements
-------------------
+Better links
+------------
-### page titles
+### Page title in links
-Use nice page titles from meta plugin in links, as inline already
-does. This is actually a duplicate for
-[[bugs/pagetitle_function_does_not_respect_meta_titles]], which might
-be fixed by something like [[todo/using_meta_titles_for_parentlinks]].
+Using the fix to
+[[bugs/pagetitle_function_does_not_respect_meta_titles]] from
+[[intrigeri]]'s `meta` branch, the generated links' text is based on
+the page titles set with the [[meta|plugins/meta]] plugin. This has to
+be merged upstream, though.
Translation quality assurance
-----------------------------
-Modifying a PO file via the CGI must be forbidden if the new version
-is not a valid PO file. As a bonus, check that it provides a more
-complete translation than the existing one.
-
-A new `cansave` type of hook would be needed to implement this.
+Modifying a PO file via the CGI is already forbidden if the new
+version is not a valid PO file. As a bonus, check that it provides
+a more complete translation than the existing one.
Note: committing to the underlying repository is a way to bypass
this check.
+
+Robustness tests
+----------------
+
+### Disabling the plugin
+
+- enabling the plugin with `po_translatable_pages` set
+- enabling the plugin without `po_translatable_pages` set: **OK**
+- disabling the plugin: **OK**
+
+### Changing the plugin config
+
+- adding existing pages to `po_translatable_pages`: **OK**
+- removing existing pages from `po_translatable_pages`: **OK**
+- adding a language to `po_slave_languages`: **OK**
+- removing a language from `po_slave_languages`: **OK**
+- changing `po_master_language`: **OK**
+- replacing `po_master_language` with a language previously part of
+ `po_slave_languages`: needs two rebuilds, but **OK** (this is quite
+ a perverse test actually)
+
+### Creating pages
+
+- creating a master page via RCS: **OK**
+- creating a master page via CGI: **OK**
+
+### Deleting pages
+
+- removing a master page via RCS: **OK**
+- removing a translation via RCS: **OK**
+- removing a master page via CGI: **OK**
+- removing a translation via CGI: **OK**
+
+### Renaming pages
+
+- renaming a master page via RCS: **OK** (but the old translations
+ are lost, because not all RCS track file renaming)
+- renaming a master page and its translations via RCS: **OK**
+- renaming a master page via CGI: **OK**
+- renaming a translation via RCS
+- renaming a translation via CGI
+
+### Misc
+
+- general test with `usedirs` disabled: **OK**
+- general test with `indexpages` enabled
+- general test with `po_link_to=default`
+
+Documentation
+-------------
+
+Maybe write separate documentation depending on the people it targets:
+translators, wiki administrators, hackers. This plugin may be complex
+enough to deserve this.
+
+Gettext-ize the plugin code.
+
+Misc
+----
+
+* Can the form validation system be used instead of creating the
+ `cansave` hook?
sipb-www / ikiwiki.git / blobdiff