better button

[git.ikiwiki.info.git] / doc / security.mdwn

diff --git a/doc/security.mdwn b/doc/security.mdwn
index 252239331d30731a5c0fc750bd874e04114ced0a..48d82db898c0f1a8c210ecafdcc97e90bf2f5c6a 100644 (file)
--- a/doc/security.mdwn
+++ b/doc/security.mdwn
@@ -30,38 +30,11 @@ If your web server does any parsing of special sorts of files (for example,
 server parsed html files), then if you let anyone else add files to the wiki,
 they can try to use this to exploit your web server.
 
 server parsed html files), then if you let anyone else add files to the wiki,
 they can try to use this to exploit your web server.
 

-## symlink attacks
-
-Could a committer trick ikiwiki into following a symlink and operating on
-some other tree that it shouldn't? svn supports symlinks, so one can get
-into the repo. ikiwiki uses File::Find to traverse the repo, and does not
-tell it to follow symlinks, but it might be possible to race replacing a
-directory with a symlink and trick it into following.
-
-It would certianly be possible to start out with a directory, let ikiwiki
-run and find a file in there, then replace it with a symlink, and ikiwiki
-would then go ahead and follow the symlink when it went to open that file
-to read it. If it was some private file and was running suid, that could be
-bad.
-
-TODO: seems that locking to prevent more than one ikiwiki run at a time
-would both fix this and is a good idea in general. With locking, an
-attacker couldn't get ikiwiki to svn up while another instance was running.
+## multiple accessors of wiki directory

 
 

-## multiple accessors of wiki source directory
+If multiple people can write to the source directory ikiwiki is using, or to the destination directory it writes files to, then one can cause trouble for the other when they run ikiwiki through symlink attacks.

 
 

-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
-attacks.
-
-So it's best if only one person can ever write to the checkout that ikiwiki
-compiles the wiki from.
-
-## webserver symlink attacks
-
-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.
+So it's best if only one person can ever write to those directories.

 
 ## setup files
 
 
 ## setup files
 


@@ -71,9 +44,20 @@ this wiki, BTW.
 
 ## svn commit logs
 
 
 ## svn commit logs
 

-Currently html is not escape in svn commit logs, this should probably be fixed.
+Anyone with svn commit access can forge "web commit from foo" and make it appear on [[RecentChanges]] like foo committed. One way to avoid this would be to limit web commits to those done by a certian user.
+
+It's actually possible to force a whole series of svn commits to appear to
+have come just before yours, by forging svn log output. This could be
+guarded against by using svn log --xml.

 
 

-Anyone with svn commit access can forge "web commit from foo" and make it appeat on [[RecentChanges]] like foo committed. One way to avoid this would be to limit web commits to those done by a certian user.
+ikiwiki escapes any html in svn commit logs to prevent other mischief.
+
+## page locking can be bypassed via direct svn commits
+
+A [[lock]]ed page can only be edited on the web by an admin, but
+anyone who is allowed to commit direct to svn can bypass this. This is by
+design, although a subversion pre-commit hook could be used to prevent
+editing of locked pages when using subversion, if you really need to.

 
 ----
 
 
 ----
 


@@ -109,7 +93,34 @@ been no problem yet.
 
 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
 
 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..
+wiki admin and untainted filenames. And it runs with taint checks on of course..
+
+## cgi data security
+
+When ikiwiki runs as a cgi to edit a page, it is passed the name of the
+page to edit. It has to make sure to sanitise this page, to prevent eg,
+editing of ../../../foo, or editing of files that are not part of the wiki,
+such as subversion dotfiles. This is done by sanitising the filename
+removing unallowed characters, then making sure it doesn't start with "/"
+or contain ".." or "/.svn/". Annoyingly ad-hoc, this kind of code is where
+security holes breed. It needs a test suite at the very least.
+
+## CGI::Session security
+
+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.
+
+## cgi password security
+
+Login to the wiki involves sending a password in cleartext over the net.
+Cracking the password only allows editing the wiki as that user though.
+If you care, you can use https, I suppose.
+
+# Fixed holes
+
+_(Unless otherwise noted, these were discovered and immediatey fixed by the ikiwiki developers.)_

 
 ## destination directory file replacement
 
 
 ## destination directory file replacement
 


@@ -124,25 +135,30 @@ it will refuse to create it.
 
 Still, this sort of attack is something to keep in mind.
 
 
 Still, this sort of attack is something to keep in mind.
 

-## cgi data security
+## symlink attacks

 
 

-When ikiwiki runs as a cgi to edit a page, it is passed the name of the
-page to edit. It has to make sure to sanitise this page, to prevent eg,
-editing of ../../../foo, or editing of files that are not part of the wiki,
-such as subversion dotfiles. This is done by sanitising the filename
-removing unallowed characters, then making sure it doesn't start with "/"
-or contain ".." or "/.svn/". Annoyingly ad-hoc, this kind of code is where
-security holes breed. It needs a test suite at the very least.
+Could a committer trick ikiwiki into following a symlink and operating on
+some other tree that it shouldn't? svn supports symlinks, so one can get
+into the repo. ikiwiki uses File::Find to traverse the repo, and does not
+tell it to follow symlinks, but it might be possible to race replacing a
+directory with a symlink and trick it into following the link.

 
 

-## cgi password security
+Also, if someone checks in a symlink to /etc/passwd, ikiwiki would read and
+publish that, which could be used to expose files a committer otherwise
+wouldn't see.

 
 

-Login to the wiki involves sending a password in cleartext over the net.
-Cracking the password only allows editing the moo as that user though.
-If you care, you can use https, I suppose.
+To avoid this, ikiwiki will skip over symlinks when scanning for pages, and
+uses locking to prevent more than one instance running at a time. The lock
+prevents one ikiwiki from running a svn up at the wrong time to race
+another ikiwiki. So only attackers who can write to the working copy on
+their own can race it.

 
 

-## CGI::Session security
+## symlink + cgi attacks

 
 

-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.
+Similarly, a svn commit of a symlink could be made, ikiwiki ignores it
+because of the above, but the symlink is still there, and then you edit the
+page from the web, which follows the symlink when reading the page, and
+again when saving the changed page.
+
+This was fixed by making ikiwiki refuse to read or write to files that are
+symlinks, combined with the above locking.