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security improvements, switched to single session db file

master
joey 2006-03-12 18:07:14 +00:00
parent 8859b2feaf
commit 0563a600e9
2 changed files with 73 additions and 39 deletions
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92
doc/security.mdwn
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@ -52,10 +52,10 @@ attacker couldn't get ikiwiki to svn up while another instance was running.
If multiple people can write to the source directory ikiwiki is using, then
one can cause trouble for the other when they run ikiwiki through symlink
sttacks.
attacks.
So it's best if only one person can ever write to the checkout that ikiwiki
compiles the moo from.
compiles the wiki from.
## webserver symlink attacks
@ -63,6 +63,55 @@ If someone checks in a symlink to /etc/passwd, ikiwiki would publish that.
To aoid this, ikiwiki will need to avoid reading files that are symlinks.
TODO and note discussion of races above.
----
# Hopefully non-holes
(AKA, the assumptions that will be the root of most security holes...)
## exploting ikiwiki with bad content
Someone could add bad content to the wiki and hope to exploit ikiwiki.
Note that ikiwiki runs with perl taint checks on, so this is unlikely.
## publishing cgi scripts
ikiwiki does not allow cgi scripts to be published as part of the wiki. Or
rather, the script is published, but it's not marked executable (except in
the case of "destination directory file replacement" below), so hopefully
your web server will not run it.
## suid wrappers
ikiwiki --wrapper is intended to generate a wrapper program that
runs ikiwiki to update a given wiki. The wrapper can in turn be made suid,
for example to be used in a [[post-commit]] hook by people who cannot write
to the html pages, etc.
If the wrapper script is made suid, then any bugs in this wrapper would be
security holes. The wrapper is written as securely as I know how, is based
on code that has a history of security use long before ikiwiki, and there's
been no problem yet.
## shell exploits
ikiwiki does not expose untrusted data to the shell. In fact it doesn't use
system() at all, and the only use of backticks is on data supplied by the
wiki admin. And it runs with taint checks on of course..
## destination directory file replacement
Any file in the destination directory that is a valid page filename can be
replaced, even if it was not originally rendered from a page. For example,
ikiwiki.cgi could be edited in the wiki, and it would write out a
replacement. File permission is preseved. Yipes!
This was fixed by making ikiwiki check if the file it's writing to exists;
if it does then it has to be a file that it's aware of creating before, or
it will refuse to create it.
Still, this sort of attack is something to keep in mind.
## cgi data security
When ikiwiki runs as a cgi to edit a page, it is passed the name of the
@ -81,38 +130,7 @@ If you care, you can use https, I suppose.
## CGI::Session security
Is CGI::Session secure? Well, it writes the session files world-readable,
which could be used by a local attacker to take over someone's session.
I have no idea if CGI::Session writes session files securely to /tmp.
ikiwiki makes it write them to a directory it controls (but see "multiple
accessors of wiki source directory" above).
----
# Probable non-holes
## exploting ikiwiki with bad content
Someone could add bad content to the wiki and hope to exploit ikiwiki.
Note that ikiwiki runs with perl taint checks on, so this is unlikely.
## publishing cgi scripts
ikiwiki does not allow cgi scripts to be published as part of the wiki. Or
rather, the script is published, but it's not marked executable, so
hopefully your web server will not run it.
## suid wrappers
ikiwiki --wrapper is intended to generate a wrapper program that
runs ikiwiki to update a given wiki. The wrapper can in turn be made suid,
for example to be used in a [[post-commit]] hook by people who cannot write
to the html pages, etc.
If the wrapper script is made suid, then any bugs in this wrapper would be
security holes. The wrapper is written as securely as I know how, is based on code that has a history of security use long before ikiwiki, and there's been no problem yet.
## shell exploits
ikiwiki does not expose untrusted data to the shell. In fact it doesn't use system() at all, and the only use of backticks is on data supplied by the wiki admin. And it runs with taint checks on of course..
I've audited this module and it is massively insecure by default. ikiwiki
uses it in one of the few secure ways; by forcing it to write to a
directory it controls (and not /tmp) and by setting a umask that makes the
file not be world readable.

20
ikiwiki
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@ -306,6 +306,17 @@ sub finalize ($$) { #{{{
return $template->output;
} #}}}
# Important security check. Make sure to call this before saving any files
# to the source directory.
sub check_overwrite ($$) { #{{{
my $dest=shift;
my $src=shift;
if (! exists $renderedfiles{$src} && -e $dest) {
error("$dest exists and was not rendered from $src before, not overwriting");
}
} #}}}
sub render ($) { #{{{
my $file=shift;
@ -320,12 +331,14 @@ sub render ($) { #{{{
$content=htmlize($type, $content);
$content=finalize($content, $page);
check_overwrite("$destdir/".htmlpage($page), $page);
writefile("$destdir/".htmlpage($page), $content);
$oldpagemtime{$page}=time;
$renderedfiles{$page}=htmlpage($page);
}
else {
$links{$file}=[];
check_overwrite("$destdir/$file", $file);
writefile("$destdir/$file", $content);
$oldpagemtime{$file}=time;
$renderedfiles{$file}=$file;
@ -941,8 +954,11 @@ sub cgi () { #{{{
}
CGI::Session->name("ikiwiki_session");
my $session = CGI::Session->new(undef, $q,
{ Directory=> "$srcdir/.ikiwiki/sessions" });
my $oldmask=umask(077);
my $session = CGI::Session->new("driver:db_file", $q,
{ FileName => "$srcdir/.ikiwiki/sessions.db" });
umask($oldmask);
# Everything below this point needs the user to be signed in.
if ((! $anonok && ! defined $session->param("name")) || $do eq 'signin') {