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Cronk
join:2005-07-16

3 edits

Cronk to Blackbird

Member

to Blackbird

Re: Open a pdf in browser vs in application

I'm referring to whether there is any added risk as a result of going through the browser. The inability to do multiple manual scans is not in the picture here since the users in question would not ever scan first anyway.

Blackbird touched on the risks I am asking about when he said:
said by Blackbird:

..using a plug-in (which in turn invokes the application program itself) within the browser add two more layers of potential security vulnerability ahead of the app alone.

although I can't say I understand the two layers he refers to. Does opening it in the browser create the possibility that the exploit will be able to poke for vulnerabilities in the browser, that would otherwise not have been exploitable if the pdf was opened in the application?

Blackbird
Built for Speed
Premium Member
join:2005-01-14
Fort Wayne, IN

1 recommendation

Blackbird

Premium Member

said by Cronk:

...

said by Blackbird:

..using a plug-in (which in turn invokes the application program itself) within the browser add two more layers of potential security vulnerability ahead of the app alone.

although I can't say I understand the two layers he refers to. Does opening it in the browser create the possibility that the exploit will be able to poke for vulnerabilities in the browser, that would otherwise not have been exploitable if the pdf was opened in the application?

The browser must communicate with the plug-in and the plug-in communicates with its related app which then ostensibly communicates with the target file. Those extra two layers of data exchange and interface with the OS (browser/plugin and plugin/app) establish at least the possibility for things like unchecked buffer overflows plus who-knows-what other possible hiccups that some creative hackers might discover. Even if the app itself is airtight, there are two added levels for mischief to occur when viewing through the browser... though that's not to say both added levels are equally vulnerable or are easy to code an exploit for. But they do stand as added code that can be messed with... and I prefer to keep all that to a minimum by simply downloading the file, scanning it several ways, and opening it directly with the app of choice.
Cronk
join:2005-07-16

Cronk

Member

OK thanks.
mysec
Premium Member
join:2005-11-29

mysec to Cronk

Premium Member

to Cronk
said by Cronk:

I'm referring to whether there is any added risk as a result of going through the browser. The inability to do multiple manual scans is not in the picture here since the users in question would not ever scan first anyway.

Does opening it in the browser create the possibility that the exploit will be able to poke for vulnerabilities in the browser, that would otherwise not have been exploitable if the pdf was opened in the application?


The current PDF exploits that are part of the Exploit Kits hosted on malware sites one may likely encounter via some type of redirection, aren't looking for vulnerabilities in the browser, rather, in the PDF application itself.

Therefore, whether the PDF file is opened automatically via a browser plug-in, or manually by a user, the exploit code will run, if the PDF Reader isn't patched for that particular vulnerability.

Here is some typical download code in a booby-trapped PDF file:







Again, if the PDF Reader is not patched against a particular vulnerability, then the download will occur automatically and the user potentially will be infected, barring some other security measure blocking the download.

The safety measure in having the PDF plug-in disabled, or whitelisted for certain sites, is that the exploit code on the malware site that triggers the download will cause the browser to alert the user:




If the user's policy is not to download anything that she/he hasn't gone looking for, the user will cancel the prompt and move on -- exploit fails.

----
rich

Lagz
Premium Member
join:2000-09-03
The Rock

Lagz

Premium Member

To focus on something Blackbird was saying in an earlier post about extra layers of vulnerability. In the recent Foxit plugin vulnerability, it was the plugin that was at fault and not Foxit reader directly.
»www.theregister.co.uk/20 ··· in_vuln/

But the bug is not triggered by a booby-trapped document, which is the usual way of infecting systems running insecure PDF readers. Instead, clicking on a link to any PDF that deliberately includes a very long query string after the filename causes a buffer overflow in the Foxit plugin.



Whether that's currently being exploited on a particular malware site currently or not shouldn't be at issue, but the fact that even the plugins themselves add potential vulnerability.
mysec
Premium Member
join:2005-11-29

1 recommendation

mysec

Premium Member

said by Lagz:

In the recent Foxit plugin vulnerability, it was the plugin that was at fault and not Foxit reader directly.


Thanks for that update! More reason to keep the plugin disabled.

Note, however, that there is a social engineering component to this exploit:

Italian security researcher Andrea Micalizzi discovered that the latest version of the software crashes if users are tricked into clicking on an overly long web link.

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rich

Lagz
Premium Member
join:2000-09-03
The Rock

1 recommendation

Lagz

Premium Member

said by mysec:

said by Lagz:

In the recent Foxit plugin vulnerability, it was the plugin that was at fault and not Foxit reader directly.


Thanks for that update! More reason to keep the plugin disabled.

Note, however, that there is a social engineering component to this exploit:

Italian security researcher Andrea Micalizzi discovered that the latest version of the software crashes if users are tricked into clicking on an overly long web link.

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rich

Yep. Sadly there is no fix or update for social engineering.
mysec
Premium Member
join:2005-11-29

1 recommendation

mysec

Premium Member

said by Lagz:

Yep. Sadly there is no fix or update for social engineering.


I'm going make a note of that!

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rich

Blackbird
Built for Speed
Premium Member
join:2005-01-14
Fort Wayne, IN

Blackbird to mysec

Premium Member

to mysec
said by mysec:

... Note, however, that there is a social engineering component to this exploit:

Italian security researcher Andrea Micalizzi discovered that the latest version of the software crashes if users are tricked into clicking on an overly long web link.

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rich

Much real-world digital maliciousness relies on multiple factors for success, just one of which is social engineering. This is one of the realities that complicates the analysis of a computer exploit event or the prevention of similar attacks against other computer owners. Your software can be fully patched, yet one oops in "safe hex" habits and trouble may loom. Likewise, you can be as "safe hex" careful as humanly possible, but leave some program on a system unpatched and trouble may loom. And so on... Watching posts in this forum over time, one becomes highly aware of just how many ways the various exploit factors interplay to both cause confusion and to make nearly impossible any simple, one-size-fits-all solution to preventing infections.