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Re: Exploiting vulnerable php functions


From: Ryan Sears <rdsears () mtu edu>
Date: Wed, 11 Sep 2013 01:20:35 -0700

Literally the only way to leverage php to gain more access then a system()
call is if there were a buffer overflow in a php function or some other
vulnerability in a lower level of a function call, AND if most execution
functions (e.g. passthrough(), system(), exec(), shell_exec()) were
intentionally banned or "safe_mode" (and I use that term extremely loosely)
were on. Even if that were the case, you'd need to defeat a bunch of other
memory protections in place a la exploiting a regular buffer overflow.

I think what Bart may have been referencing is the fact that some object
oriented languages like  Python and Java return references to their
returned objects, which allows one to do stuff like "  blahblah
".trim().replace('blah','derp') and get "derpderp" returned.

This could in some languages (Java) lead to the same assortment of
vulnerabilities classified as "trusted method chaining" that allows one to
get a reference to a trusted function or object, but the security model of
java is completely different than all other object-oriented languages which
means all functions in non-java are "safe". Long story short, there's no
real way to "accidentally" include a file other then the known LFI vectors.

Sorry for the rambles, just throught I'd throw my .02$ in :)

Ryan
 On Sep 10, 2013 10:53 PM, "allison nixon" <elsakoo () gmail com> wrote:

By the way, if you did use file inclusion in order to abuse vulnerable php
functions, would it have gained you any more access than if you just file
included a shell?


On Tue, Sep 10, 2013 at 4:28 AM, Robin Wood <robin () digininja org> wrote:




On 8 September 2013 19:47, Dancing Dan <d4ncingd4n () gmail com> wrote:

I haven't looked at PHP internals but, some languages create functions
as extensions of other functions as a form of code reuse. This could lead
to unexpected file inclusion.

Does anybody know if PHP does that?


Do you mean one function internally calls another, for example a string
compare ignoring case will call the generic string compare but pass in the
ignore case flag?

I've no idea if PHP does this but would be interested to find out and if
it does to get a list of what calls what.

Robin


Bart
On Sep 8, 2013 1:39 PM, "Robin Wood" <robin () digininja org> wrote:


On 8 Sep 2013 19:01, "Jim Halfpenny" <jim.halfpenny () gmail com> wrote:

In short no. Take a look at file inclusion vulnerabilities.

http://en.m.wikipedia.org/wiki/File_inclusion_vulnerability

If you are suggesting include in a file which uses a vulnerable
function then your answer is actually yes.

Robin

Regards
Jim

On 8 Sep 2013 04:40, "Sean McCormick" <sean.m.mccormick () gmail com>
wrote:

If a website is running a version of php with vulnerable functions
does the function have to be used in a script in order to exploit the
vulnerability?


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