diff options
| -rw-r--r-- | doc/plugins/po.mdwn | 273 | ||||
| -rw-r--r-- | doc/plugins/po/security.mdwn | 206 |
2 files changed, 238 insertions, 241 deletions
diff --git a/doc/plugins/po.mdwn b/doc/plugins/po.mdwn index 5c98f3485..7165015ab 100644 --- a/doc/plugins/po.mdwn +++ b/doc/plugins/po.mdwn @@ -86,8 +86,8 @@ 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 +* `foo/destpage/index.LL.html` if `usedirs` is enabled +* `foo/destpage.LL.html` if `usedirs` is disabled ### Link to negotiated language @@ -96,10 +96,10 @@ negotiated preferred language, *i.e.* `foo/page/`. (In)compatibility notes: -- if `usedirs` is disabled, it does not make sense to set `po_link_to` +* 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 +* if the web server does not support Content Negotiation, setting `po_link_to` to `negotiated` will produce a unusable website. @@ -166,11 +166,11 @@ 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 +* `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 @@ -240,227 +240,18 @@ correctly on the slave pages: could be used to support them, but they would need a security audit * other markup languages have not been tested. +Security +======== -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. - -##### 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`. - -#### To be checked - -##### 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. - -> If a recent enough po4a is installed, this module's use is fully disabled. -> This feature has been merged in po4a CVS on 2009-01-15. --[[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. - -`Term::ReadKey` has too far reaching implications for us to -be able to guarantee anything wrt. security. - -> The option that disables `Text::WrapI18N` also disables -> `Term::ReadKey` as a consequence. [[--intrigeri]] - -### msgmerge +[[./security]] contains a detailed security analysis of this plugin +and its dependencies. -`refreshpofiles()` runs this external program. +When using po4a older than 0.35, it is recommended to uninstall +`Text::WrapI18N` (Debian package `libtext-wrapi18n-perl`), in order to +avoid a potential denial of service. -A po4a developer answered he does "not expect any security issues from -it". I did not manage to crash it with `zzuf`, nor was able to find -any past security holes. - -### msgfmt - -`isvalidpo()` runs this external program. - -* I could not manage to make it behave badly using zzuf, it exits - cleanly when too many errors are detected. -* I could not find any past security holes. - -### Fuzzing input - -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. - -The root of this bug lies in `Text::WrapI18N`, see above for -possible solutions. - -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. +TODO +==== Better links ------------ @@ -478,19 +269,19 @@ Robustness tests ### Enabling/disabling the plugin -- enabling the plugin with `po_translatable_pages` set to blacklist: **OK** -- enabling the plugin with `po_translatable_pages` set to whitelist: **OK** -- enabling the plugin without `po_translatable_pages` set: **OK** -- disabling the plugin: **OK** +* enabling the plugin with `po_translatable_pages` set to blacklist: **OK** +* enabling the plugin with `po_translatable_pages` set to whitelist: **OK** +* 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 +* 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) @@ -501,10 +292,10 @@ and via CGI, have been tested. ### Misc -- general test with `usedirs` disabled: **OK** -- general test with `indexpages` enabled: **not OK** -- general test with `po_link_to=default` with `userdirs` enabled: **OK** -- general test with `po_link_to=default` with `userdirs` disabled: **OK** +* general test with `usedirs` disabled: **OK** +* general test with `indexpages` enabled: **not OK** +* general test with `po_link_to=default` with `userdirs` enabled: **OK** +* general test with `po_link_to=default` with `userdirs` disabled: **OK** Misc. bugs ---------- diff --git a/doc/plugins/po/security.mdwn b/doc/plugins/po/security.mdwn new file mode 100644 index 000000000..318083669 --- /dev/null +++ b/doc/plugins/po/security.mdwn @@ -0,0 +1,206 @@ +[[!toc levels=2]] + +---- + +# Probable holes + +_(The list of things to fix.)_ + +## po4a-gettextize + +* po4a CVS 2009-01-16 +* Perl 5.10.0 + +`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. I therefore had to pretend the +input was in UTF-8, as does the po plugin. + + zzuf -c -s 13 -r 0.1 \ + po4a-gettextize -f text -o markdown -M utf-8 -L utf-8 \ + -m GPL-3 -p GPL-3.pot + +Crashes with: + + Malformed UTF-8 character (UTF-16 surrogate 0xdfa4) in substitution + iterator at /usr/share/perl5/Locale/Po4a/Po.pm line 1449. + Malformed UTF-8 character (fatal) at /usr/share/perl5/Locale/Po4a/Po.pm + line 1449. + +An incomplete pot file is left on disk. Unfortunately Po.pm tells us +nothing about the place where the crash happens. + +> 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]] + +---- + +# Potential gotchas + +_(Things not to do.)_ + + +## Blindly activating more po4a format modules + +The format 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. + +---- + +# Hopefully non-holes + +_(AKA, the assumptions that will be the root of most security holes...)_ + +## PO file features + +No [documented](http://www.gnu.org/software/gettext/manual/gettext.html#PO-Files) +directive that can be put in po files is supposed to cause mischief +(ie, include other files, run commands, crash gettext, whatever). + +## gettext + +### Security history + +The only past security issue I could find in GNU gettext is +[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) may allow local users to overwrite files via +a symlink attack on temporary files. + +This plugin would not have allowed to exploit this bug, as it does not +use, either directly or indirectly, the faulty scripts. + +Note: the lack of found security issues can either indicate that there +are none, or reveal that no-one ever bothered to find or publish them. + +### msgmerge + +`refreshpofiles()` runs this external program. + +* I was not able to crash it with `zzuf`. +* I could not find any past security hole. + +### msgfmt + +`isvalidpo()` runs this external program. + +* I was not able to make it behave badly using zzuf: it exits cleanly + when too many errors are detected. +* I could not find any past security hole. + +## po4a + +### Security history + +The only past security issue I could find in po4a is +[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 allowed local users to +overwrite arbitrary files via a symlink attack on the +gettextization.failed.po temporary file. + +This plugin would not have allowed to exploit this bug, as it does not +use, either directly or indirectly, the faulty `gettextize` function. + +Note: the lack of found security issues can either indicate that there +are none, or reveal that no-one ever bothered to find or publish them. + +### General feeling + +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. +The following analysis was done with his help. + +### Details + +* 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` is 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. + +#### Locale::Po4a::Text + +* does not run any external program +* only `do_paragraph()` builds regexp's that expand untrusted + variables; according to [[Joey]], this is "Freaky code, but seems ok + due to use of `quotementa`". + +#### Text::WrapI18N + +`Text::WrapI18N` can cause DoS +([Debian bug #470250](http://bugs.debian.org/470250)). +It is optional, and we do not need the features it provides. + +If a recent enough po4a (>=2009-01-15 CVS, which will probably be +released as 0.35) is installed, this module's use is fully disabled. +Else, the wiki administrator is warned about this at runtime. + +#### 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. + +`Term::ReadKey` has too far reaching implications for us to +be able to guarantee anything wrt. security. + +If a recent enough po4a (>=2009-01-15 CVS, which will probably be +released as 0.35) is installed, this module's use is fully disabled. + +#### Fuzzing input + +##### po4a-translate + +* po4a CVS 2009-01-16 +* Perl 5.10.0 + +`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. + +`LICENSES` is a 21M file containing 100 concatenated copies of all the +files in `/usr/share/common-licenses/`; I had no existing PO file or +translated versions at hand, which renders these tests +quite incomplete. + + 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. + +The root of this bug lies in `Text::WrapI18N`, see the corresponding +section. + + +---- + +# Fixed holes + |