po(doc): moved security analysis to its own page
Signed-off-by: intrigeri <intrigeri@boum.org>master
intrigeri
parent
df82b5e62a
commit
40de619d49
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@ -86,8 +86,8 @@ If `po_link_to` is set to `current`, `\[[destpage]]` links to the
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`destpage`'s version written in the current page's language, if
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`destpage`'s version written in the current page's language, if
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available, *i.e.*:
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available, *i.e.*:
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- `foo/destpage/index.LL.html` if `usedirs` is enabled
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* `foo/destpage/index.LL.html` if `usedirs` is enabled
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- `foo/destpage.LL.html` if `usedirs` is disabled
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* `foo/destpage.LL.html` if `usedirs` is disabled
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### Link to negotiated language
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### Link to negotiated language
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@ -96,10 +96,10 @@ negotiated preferred language, *i.e.* `foo/page/`.
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(In)compatibility notes:
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(In)compatibility notes:
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- if `usedirs` is disabled, it does not make sense to set `po_link_to`
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* if `usedirs` is disabled, it does not make sense to set `po_link_to`
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to `negotiated`; this option combination is neither implemented
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to `negotiated`; this option combination is neither implemented
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nor allowed.
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nor allowed.
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- if the web server does not support Content Negotiation, setting
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* if the web server does not support Content Negotiation, setting
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`po_link_to` to `negotiated` will produce a unusable website.
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`po_link_to` to `negotiated` will produce a unusable website.
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@ -166,11 +166,11 @@ One typically adds the following code to `templates/page.tmpl`:
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The following variables are available inside the loop (for every page in):
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The following variables are available inside the loop (for every page in):
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- `URL` - url to the page
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* `URL` - url to the page
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- `CODE` - two-letters language code
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* `CODE` - two-letters language code
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- `LANGUAGE` - language name (as defined in `po_slave_languages`)
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* `LANGUAGE` - language name (as defined in `po_slave_languages`)
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- `MASTER` - is true (1) if, and only if the page is a "master" page
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* `MASTER` - is true (1) if, and only if the page is a "master" page
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- `PERCENT` - for "slave" pages, is set to the translation completeness, in percents
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* `PERCENT` - for "slave" pages, is set to the translation completeness, in percents
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### Display the current translation status
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### Display the current translation status
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@ -240,228 +240,19 @@ correctly on the slave pages:
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could be used to support them, but they would need a security audit
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could be used to support them, but they would need a security audit
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* other markup languages have not been tested.
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* other markup languages have not been tested.
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Security
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========
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[[./security]] contains a detailed security analysis of this plugin
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and its dependencies.
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When using po4a older than 0.35, it is recommended to uninstall
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`Text::WrapI18N` (Debian package `libtext-wrapi18n-perl`), in order to
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avoid a potential denial of service.
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TODO
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TODO
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====
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====
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Security checks
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---------------
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### Security history
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The only past security issues I could find in GNU gettext and po4a
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are:
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- [CVE-2004-0966](http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2004-0966),
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*i.e.* [Debian bug #278283](http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=278283):
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the autopoint and gettextize scripts in the GNU gettext package
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1.14 and later versions, as used in Trustix Secure Linux 1.5
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through 2.1 and other operating systems, allows local users to
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overwrite files via a symlink attack on temporary files.
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- [CVE-2007-4462](http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2007-4462):
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`lib/Locale/Po4a/Po.pm` in po4a before 0.32 allows local users to
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overwrite arbitrary files via a symlink attack on the
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gettextization.failed.po temporary file.
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**FIXME**: check whether this plugin would have been a possible attack
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vector to exploit these vulnerabilities.
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Depending on my mood, the lack of found security issues can either
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indicate that there are none, or reveal that no-one ever bothered to
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find (and publish) them.
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### PO file features
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Can any sort of directives be put in po files that will cause mischief
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(ie, include other files, run commands, crash gettext, whatever)?
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> No [documented](http://www.gnu.org/software/gettext/manual/gettext.html#PO-Files)
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> directive is supposed to do so. [[--intrigeri]]
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### Running po4a on untrusted content
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Are there any security issues on running po4a on untrusted content?
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To say the least, this issue is not well covered, at least publicly:
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- the documentation does not talk about it;
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- grep'ing the source code for `security` or `trust` gives no answer.
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On the other hand, a po4a developer answered my questions in
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a convincing manner, stating that processing untrusted content was not
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an initial goal, and analysing in detail the possible issues.
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#### Already checked
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- the core (`Po.pm`, `Transtractor.pm`) should be safe
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- po4a source code was fully checked for other potential symlink
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attacks, after discovery of one such issue
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- the only external program run by the core is `diff`, in `Po.pm` (in
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parts of its code we don't use)
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- `Locale::gettext`: only used to display translated error messages
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- Nicolas François "hopes" `DynaLoader` is safe, and has "no reason to
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think that `Encode` is not safe"
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- Nicolas François has "no reason to think that `Encode::Guess` is not
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safe". The po plugin nevertheless avoids using it by defining the
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input charset (`file_in_charset`) before asking `Transtractor` to
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read any file. NB: this hack depends on po4a internals to stay
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the same.
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##### Locale::Po4a modules
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The modules we want to use have to be checked, as not all are safe
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(e.g. the LaTeX module's behaviour is changed by commands included in
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the content); they may use regexps generated from the content.
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`Chooser.pm` only loads the plugin we tell it too: currently, this
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means the `Text` module only.
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`Text` module (I checked the CVS version):
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- it does not run any external program
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- only `do_paragraph()` builds regexp's that expand untrusted
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variables; they seem safe to me, but someone more expert than me
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will need to check. Joey?
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> Freaky code, but seems ok due to use of `quotementa`.
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#### To be checked
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##### Text::WrapI18N
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`Text::WrapI18N` can cause DoS (see the
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[Debian bug #470250](http://bugs.debian.org/470250)), but it is
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optional and we do not need the features it provides.
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> If a recent enough po4a is installed, this module's use is fully disabled.
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> This feature has been merged in po4a CVS on 2009-01-15. --[[intrigeri]]
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##### Term::ReadKey
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`Term::ReadKey` is not a hard dependency in our case, *i.e.* po4a
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works nicely without it. But the po4a Debian package recommends
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`libterm-readkey-perl`, so it will probably be installed on most
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systems using the po plugin.
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`Term::ReadKey` has too far reaching implications for us to
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be able to guarantee anything wrt. security.
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> The option that disables `Text::WrapI18N` also disables
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> `Term::ReadKey` as a consequence. [[--intrigeri]]
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### msgmerge
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`refreshpofiles()` runs this external program.
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A po4a developer answered he does "not expect any security issues from
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it". I did not manage to crash it with `zzuf`, nor was able to find
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any past security holes.
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### msgfmt
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`isvalidpo()` runs this external program.
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* I could not manage to make it behave badly using zzuf, it exits
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cleanly when too many errors are detected.
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* I could not find any past security holes.
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### Fuzzing input
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Test conditions:
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- a 21M file containing 100 concatenated copies of all the files in my
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`/usr/share/common-licenses/`; I had no existing PO file or
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translated versions at hand, which renders these tests
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quite incomplete.
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- po4a was the Debian 0.34-2 package; the same tests were also run
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after replacing the `Text` module with the CVS one (the core was not
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changed in CVS since 0.34-2 was released), without any significant
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difference in the results.
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- Perl 5.10.0-16
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#### po4a-gettextize
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`po4a-gettextize` uses more or less the same po4a features as our
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`refreshpot` function.
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Without specifying an input charset, zzuf'ed `po4a-gettextize` quickly
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errors out, complaining it was not able to detect the input charset;
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it leaves no incomplete file on disk.
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So I had to pretend the input was in UTF-8, as does the po plugin.
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Two ways of crashing were revealed by this command-line:
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zzuf -vc -s 0:100 -r 0.1:0.5 \
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po4a-gettextize -f text -o markdown -M utf-8 -L utf-8 \
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-m LICENSES >/dev/null
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They are:
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Malformed UTF-8 character (UTF-16 surrogate 0xdcc9) in substitution iterator at /usr/share/perl5/Locale/Po4a/Po.pm line 1443.
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Malformed UTF-8 character (fatal) at /usr/share/perl5/Locale/Po4a/Po.pm line 1443.
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and
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Malformed UTF-8 character (UTF-16 surrogate 0xdcec) in substitution (s///) at /usr/share/perl5/Locale/Po4a/Po.pm line 1443.
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Malformed UTF-8 character (fatal) at /usr/share/perl5/Locale/Po4a/Po.pm line 1443.
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Perl seems to exit cleanly, and an incomplete PO file is written on
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disk. I not sure whether if this is a bug in Perl or in `Po.pm`.
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> It's fairly standard perl behavior when fed malformed utf-8. As long as it doesn't
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> crash ikiwiki, it's probably acceptable. Ikiwiki can do some similar things itself when fed malformed utf-8 (doesn't crash tho) --[[Joey]]
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#### po4a-translate
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`po4a-translate` uses more or less the same po4a features as our
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`filter` function.
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Without specifying an input charset, same behaviour as
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`po4a-gettextize`, so let's specify UTF-8 as input charset as of now.
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zzuf -cv \
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po4a-translate -d -f text -o markdown -M utf-8 -L utf-8 \
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-k 0 -m LICENSES -p LICENSES.fr.po -l test.fr
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... prints tons of occurences of the following error, but a complete
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translated document is written (obviously with some weird chars
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inside):
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Use of uninitialized value in string ne at /usr/share/perl5/Locale/Po4a/TransTractor.pm line 854.
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Use of uninitialized value in string ne at /usr/share/perl5/Locale/Po4a/TransTractor.pm line 840.
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Use of uninitialized value in pattern match (m//) at /usr/share/perl5/Locale/Po4a/Po.pm line 1002.
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While:
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zzuf -cv -s 0:10 -r 0.001:0.3 \
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po4a-translate -d -f text -o markdown -M utf-8 -L utf-8 \
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-k 0 -m LICENSES -p LICENSES.fr.po -l test.fr
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... seems to lose the fight, at the `readpo(LICENSES.fr.po)` step,
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against some kind of infinite loop, deadlock, or any similar beast.
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The root of this bug lies in `Text::WrapI18N`, see above for
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possible solutions.
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gettext/po4a rough corners
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--------------------------
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- fix infinite loop when synchronizing two ikiwiki (when checkouts
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live in different directories): say bla.fr.po has been updated in
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repo2; pulling repo2 from repo1 seems to trigger a PO update, that
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changes bla.fr.po in repo1; then pushing repo1 to repo2 triggers
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a PO update, that changes bla.fr.po in repo2; etc.; quickly fixed in
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`629968fc89bced6727981c0a1138072631751fee`, by disabling references
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in Pot files. Using `Locale::Po4a::write_if_needed` might be
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a cleaner solution. (warning: this function runs the external
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`diff` program, have to check security)
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- new translations created in the web interface must get proper
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charset/encoding gettext metadata, else the next automatic PO update
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removes any non-ascii chars; possible solution: put such metadata
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into the Pot file, and let it propagate; should be fixed in
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`773de05a7a1ee68d2bed173367cf5e716884945a`, time will tell.
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Better links
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Better links
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------------
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------------
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@ -478,19 +269,19 @@ Robustness tests
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### Enabling/disabling the plugin
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### Enabling/disabling the plugin
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- enabling the plugin with `po_translatable_pages` set to blacklist: **OK**
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* enabling the plugin with `po_translatable_pages` set to blacklist: **OK**
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- enabling the plugin with `po_translatable_pages` set to whitelist: **OK**
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* enabling the plugin with `po_translatable_pages` set to whitelist: **OK**
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- enabling the plugin without `po_translatable_pages` set: **OK**
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* enabling the plugin without `po_translatable_pages` set: **OK**
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- disabling the plugin: **OK**
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* disabling the plugin: **OK**
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### Changing the plugin config
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### Changing the plugin config
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- adding existing pages to `po_translatable_pages`: **OK**
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* adding existing pages to `po_translatable_pages`: **OK**
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- removing existing pages from `po_translatable_pages`: **OK**
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* removing existing pages from `po_translatable_pages`: **OK**
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- adding a language to `po_slave_languages`: **OK**
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* adding a language to `po_slave_languages`: **OK**
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- removing a language from `po_slave_languages`: **OK**
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* removing a language from `po_slave_languages`: **OK**
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- changing `po_master_language`: **OK**
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* changing `po_master_language`: **OK**
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- replacing `po_master_language` with a language previously part of
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* replacing `po_master_language` with a language previously part of
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`po_slave_languages`: needs two rebuilds, but **OK** (this is quite
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`po_slave_languages`: needs two rebuilds, but **OK** (this is quite
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a perverse test actually)
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a perverse test actually)
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@ -501,10 +292,10 @@ and via CGI, have been tested.
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### Misc
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### Misc
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- general test with `usedirs` disabled: **OK**
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* general test with `usedirs` disabled: **OK**
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- general test with `indexpages` enabled: **not OK**
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* general test with `indexpages` enabled: **not OK**
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- general test with `po_link_to=default` with `userdirs` enabled: **OK**
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* general test with `po_link_to=default` with `userdirs` enabled: **OK**
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- general test with `po_link_to=default` with `userdirs` disabled: **OK**
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* general test with `po_link_to=default` with `userdirs` disabled: **OK**
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Misc. bugs
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Misc. bugs
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----------
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----------
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@ -0,0 +1,206 @@
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[[!toc levels=2]]
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----
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# Probable holes
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_(The list of things to fix.)_
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## po4a-gettextize
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* po4a CVS 2009-01-16
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* Perl 5.10.0
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`po4a-gettextize` uses more or less the same po4a features as our
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`refreshpot` function.
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Without specifying an input charset, zzuf'ed `po4a-gettextize` quickly
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errors out, complaining it was not able to detect the input charset;
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it leaves no incomplete file on disk. I therefore had to pretend the
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input was in UTF-8, as does the po plugin.
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zzuf -c -s 13 -r 0.1 \
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po4a-gettextize -f text -o markdown -M utf-8 -L utf-8 \
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-m GPL-3 -p GPL-3.pot
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Crashes with:
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Malformed UTF-8 character (UTF-16 surrogate 0xdfa4) in substitution
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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
|
||||||
|
|
||||||
Loading…
Reference in New Issue