X-Git-Url: http://git.vanrenterghem.biz/git.ikiwiki.info.git/blobdiff_plain/d8c28006748ffe6037104bba4c040b2850cd8402..b7a4e5a51cbb3867e37f4ed5de8f94e0d41fd152:/doc/plugins/po.mdwn?ds=sidebyside diff --git a/doc/plugins/po.mdwn b/doc/plugins/po.mdwn index 64d22d34c..04a45f8f2 100644 --- a/doc/plugins/po.mdwn +++ b/doc/plugins/po.mdwn @@ -6,15 +6,17 @@ gettext, using [po4a](http://po4a.alioth.debian.org/). It depends on the Perl `Locale::Po4a::Po` library (`apt-get install po4a`). +[[!toc levels=2]] + Introduction ============ A language is chosen as the "master" one, and any other supported language is a "slave" one. -A page written in the "master" language is a "master" page, and is -written in any supported format but PO. It does not have to be named -a special way: migration from/to this plugin does not imply heavy +A page written in the "master" language is a "master" page. It can be +of any page type supported by ikiwiki, except `po`. It does not have to be +named a special way: migration to this plugin does not imply any page renaming work. Example: `bla/page.mdwn` is a "master" Markdown page written in @@ -22,7 +24,7 @@ English; if `usedirs` is enabled, it is rendered as `bla/page/index.en.html`, else as `bla/page.en.html`. Any translation of a "master" page into a "slave" language is called -a "slave" page; it is written in the gettext PO format. PO is now +a "slave" page; it is written in the gettext PO format. `po` is now a page type supported by ikiwiki. Example: `bla/page.fr.po` is the PO "message catalog" used to @@ -33,7 +35,10 @@ rendered as `bla/page/index.fr.html`, else as `bla/page.fr.html` Configuration ============= -`po_master_language` is used to set the master language in +Supported languages +------------------- + +`po_master_language` is used to set the "master" language in `ikiwiki.setup`, such as: po_master_language => { 'code' => 'en', 'name' => 'English' } @@ -53,23 +58,31 @@ The `po_translatable_pages` setting configures what pages are translatable. It is a [[ikiwiki/PageSpec]], so you have lots of control over what kind of pages are translatable. -The `*.LL.po` translations files are anyway not considered as being -translatable, so you don't need to worry about excluding them manually -from this [[ikiwiki/PageSpec]]. +The `.po` files are not considered as being translatable, so you don't need to +worry about excluding them explicitly from this [[ikiwiki/PageSpec]]. Internal links -------------- -One can use the `po_link_to_` option in `ikiwiki.setup` to choose how +The `po_link_to` option in `ikiwiki.setup` is used to decide how internal links should be generated, depending on web server features and site-specific preferences. ### Default linking behavior If `po_link_to` is unset, or set to `default`, ikiwiki's default -linking behavior is preserved: `\[[page]]` links to the master +linking behavior is preserved: `\[[destpage]]` links to the master language's page. +### Link to current language + +If `po_link_to` is set to `current`, `\[[destpage]]` links to the +`destpage`'s version written in the current page's language, if +available, *i.e.*: + +- `foo/destpage/index.LL.html` if `usedirs` is enabled +- `foo/destpage.LL.html` if `usedirs` is disabled + ### Link to negotiated language If `po_link_to` is set to `negotiated`, `\[[page]]` links to the @@ -77,20 +90,11 @@ negotiated preferred language, *i.e.* `foo/page/`. (In)compatibility notes: -- `po_link_to => negotiated` provides no useful behavior if `usedirs` - is disabled; this option combination is neither implemented nor - allowed -- `po_link_to => negotiated` provides no useful behavior if the web - server does not support Content Negotiation - -### Link to current language - -If `po_link_to` is set to `current` and the destination page is either -a translatable page or a translation, `\[[page]]` links to the current -page's language, *i.e.*: - -- `foo/page/index.LL.html` if `usedirs` is enabled -- `foo/page.LL.html` if `usedirs` is disabled +- if `usedirs` is disabled, it does not make sense to set `po_link_to` + to `negotiated`; this option combination is neither implemented + nor allowed. +- if the web server does not support Content Negotiation, setting + `po_link_to` to `negotiated` will produce a unusable website. Server support @@ -99,17 +103,16 @@ Server support Apache ------ -Using `mod_negotiation` makes it really easy to have Apache serve the -page in the client's preferred language, if available. This is the -default Debian Apache configuration. +Using Apache `mod_negotiation` makes it really easy to have Apache +serve any page in the client's preferred language, if available. +This is the default Debian Apache configuration. When `usedirs` is enabled, one has to set `DirectoryIndex index` for the wiki context. Setting `DefaultLanguage LL` (replace `LL` with your default MIME -language) for the wiki context can be needed, to ensure +language code) for the wiki context can help to ensure `bla/page/index.en.html` is served as `Content-Language: LL`. -**FIXME**: is it still needed with the new `.en.html` naming convention? lighttpd -------- @@ -126,134 +129,399 @@ Usage Templates --------- -The `OTHERLANGUAGES` loop provides ways to display the existing -translations and/or master page. One typically adds the following code -to `templates/page.tmpl`: +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. + +### Display page's versions in other languages + +The `OTHERLANGUAGES` loop provides ways to display other languages' +versions of the same page, and the translations' status. + +One typically adds the following code to `templates/page.tmpl`:
+The following variables are available inside the loop (for every page in): + +- `URL` - url to the page +- `CODE` - two-letters language code +- `LANGUAGE` - language name (as defined in `po_slave_languages`) +- `MASTER` - is true (1) if, and only if the page is a "master" page +- `PERCENT` - for "slave" pages, is set to the translation completeness, in percents + +### Display the current translation status + +The `PERCENTTRANSLATED` variable is set to the translation +completeness, expressed in percent, on "slave" pages. + +One can use it this way: + + +
+ +
+ + Additional PageSpec tests ------------------------- This plugin enhances the regular [[ikiwiki/PageSpec]] syntax with some additional tests that are documented [[here|ikiwiki/pagespec/po]]. +Automatic PO file update +------------------------ + +Committing changes to a "master" page: + +1. updates the POT file and the PO files for the "slave" languages; + the updated PO files are then put under version control; +2. triggers a refresh of the corresponding HTML slave pages. + +Also, when the plugin has just been enabled, or when a page has just +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 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. + +Translating +----------- + +One can edit the PO files using ikiwiki's CGI (a message-by-message +interface could also be implemented at some point). + +If [[tips/untrusted_git_push]] is setup, one can edit the PO files in one's +preferred `$EDITOR`, without needing to be online. TODO ==== -Link relationships ------------------- +Security checks +--------------- -Should pages using the `OTHERLANGUAGES` template loop be declared as -linking to the same page in other versions? +### Security history -View translation status ------------------------ +The only past security issues I could find in GNU gettext and po4a +are: -One should be able to view some information about the translation -completeness, either for a given page or for the whole wiki. +- [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. -This should not be too hard using gettext tools. If this is -implemented as a -[HTML::Template](http://search.cpan.org/search?mode=dist&query=HTML%3A%3ATemplate) -loop, a page using it should depend on any "master" and "slave" pages -whose status is being displayed. +**FIXME**: check whether this plugin would have been a possible attack +vector to exploit these vulnerabilities. -If it's not too heavy to compute, this status data may be made -available in the `OTHERLANGUAGES` template loop; else, a dedicated -loop would be needed. +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. -Automatic PO files update -------------------------- +### PO file features -Committing changes to a "master" page: +Can any sort of directives be put in po files that will cause mischief +(ie, include other files, run commands, crash gettext, whatever)? -1. updates the POT file and the PO files for the supported languages; - this is done in the `needsbuild` hook; **FIXME**: the updated PO - files must then be put under version control +> No [documented](http://www.gnu.org/software/gettext/manual/gettext.html#PO-Files) +> directive is supposed to do so. [[--intrigeri]] -2. triggers a refresh of the corresponding HTML slave pages: this is - achieved by making any "slave" page dependent on the corresponding - "master" page, in the `needsbuild` hook. +### Running po4a on untrusted content -**FIXME** Also, when the plugin has just been enabled, or when a page -has just been declared as being translatable: +Are there any security issues on running po4a on untrusted content? -- all the needed POT and PO files have to be created -- the PO files must be checked into version control +To say the least, this issue is not well covered, at least publicly: -**FIXME** `refreshpofiles` uses `system()`, whose args have to be -checked more thoroughly to prevent any security issue (command -injection, etc.). +- the documentation does not talk about it; +- grep'ing the source code for `security` or `trust` gives no answer. -UI consistency: rename "Edit" button on slave pages ---------------------------------------------------- +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. -It may be surprising to some, after having pressed *Edit* on a wiki -page, to end up editing a strange looking PO file. The *Edit* button -displayed on "slave" pages must therefore be renamed *Improve -translation* . +#### Already checked -Translation quality assurance ------------------------------ +- 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. -Modifying a PO file via the CGI must only be allowed if the new -version is a valid PO file. As a bonus, check that it provides a more -complete translation than the existing one. +#### To be checked -A new `cansave` type of hook would be needed to implement this. +##### Locale::Po4a modules -Note: committing to the underlying repository is a way to bypass -this check. +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? + +##### 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]] + +##### 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]] -Translating online ------------------- +### msgmerge -As PO is a wiki page type, we already have an online PO editor, that -is ikiwiki's CGI. +`refreshpofiles()` runs this external program. A po4a developer +answered he does "not expect any security issues from it". -A message-by-message interface could also be implemented at some -point; a nice way to do offline translation work (without VCS access) -still has to be offered, though. +### Fuzzing input -Translating offline without VCS access --------------------------------------- +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]] -The following workflow should be made possible for translators without -VCS access who need to edit the PO files in another editor than a web -browser: +> po4a was not fuzzy-tested, but according to one of its developers, +> "it would be really appreciated". [[--intrigeri]] -- download the page's PO file -- use any PO editor to update the translation -- upload the updated PO file +Test conditions: -Implementation note: a generic mechanism to upload a page's source is -needed: it's only an alternative way to allow saving a the modified -page's source with the CGI. +- 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`. + +#### 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 +-------------------------- + +- fix infinite loop when synchronizing two ikiwiki (when checkouts + live in different directories): say bla.fr.po has been updated in + repo2; pulling repo2 from repo1 seems to trigger a PO update, that + changes bla.fr.po in repo1; then pushing repo1 to repo2 triggers + 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. (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. + +Better links +------------ + +### Page title in links + +To use the page titles set with the [[meta|plugins/meta]] plugin when +rendering links would be very much nicer, than the current +"filename.LL" format. This is actually a duplicate for +[[bugs/pagetitle_function_does_not_respect_meta_titles]]. + +Going to work on this in my `meta` branch. + +### Translation status in links + +See [[contrib/po]]. + +### Backlinks + +They are not updated when the source page changes (e.g. meta title). + +Page formats +------------ + +Markdown is well supported, great, but what about others? + +The [[po|plugins/po]] uses `Locale::Po4a::Text` for every page format; +this can be expected to work out of the box with most other wiki-like +formats supported by ikiwiki. Some of their ad-hoc syntax might be +parsed in a strange way, but the worst problems I can imagine would be +wrapping issues; e.g. there is code in po4a dedicated to prevent +re-wrapping the underlined Markdown headers. + +While it would be easy to better support formats such as [[html]] or +LaTeX, by using for each one the dedicated po4a module, this can be +problematic from a security point of view. + +**TODO**: test the more popular formats and write proper documentation +about it. + +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. + +Note: committing to the underlying repository is a way to bypass +this check. + +Creating new pages on the web +----------------------------- -### Short-term workflow +See [[contrib/po]]. -A possible workaround is: +Documentation +------------- -- pretend to edit the PO file online -- copy the PO file content from the textarea -- cancel the edit -- paste the content into a local file. -- edit the local file in any PO editor -- pretend to edit the PO file online -- paste the modified local file's content into the edit textarea -- save +Maybe write separate documentation depending on the people it targets: +translators, wiki administrators, hackers. This plugin may be complex +enough to deserve this.