Abusing Symbolic Links Like It's 1999

An anonymous reader writes with this snippet from James Forshaw's recent post at Google's Project Zero, which begins For the past couple of years I've been researching Windows elevation of privilege attacks. This might be escaping sandboxing or gaining system privileges. One of the techniques I've used multiple times is abusing the symbolic link facilities of the Windows operating system to redirect privileged code to create files or registry keys to escape the restrictive execution context. Symbolic links in themselves are not vulnerabilities, instead they're useful primitives for exploiting different classes of vulnerabilities such as resource planting or time-of-check time-of-use. Click through that link to see examples of this abuse in action, but also information about how the underlying risks have been (or can be) mitigated.

Comments

we can fix this

[Gravis Zero]

it seems to me that we can stop shit commercial software from being published if governments set up a mandatory bug bounty systems. it's simple, you demo the exploit and get money based on the severity and the company making the software must pay it and has X days to fix it before paying the fine again. this would result in either better education on how to find exploits, better Q/A mechanism or companies going under. frankly, i don't care which happens as long as commercial software is held accountable for bad code.

Re:we can fix this

[Anonymous Coward]

Your ideas are just like the ideas for fixing spam. I am sure my fellow slashdoters can help fix up the list...

Your post advocates a

( ) technical ( ) legislative ( ) market-based ( ) vigilante

approach to fighting spam. Your idea will not work. Here is why it wonâ(TM)t work.
(One or more of the following may apply to your particular idea, and it may
have other flaws which used to vary from state to state before a bad federal
law was passed.)

( ) Spammers can easily use it to harvest email addresses
( ) Mailing lists and other legitimate email uses would be affected
( ) No one will be able to find the guy or collect the money
( ) It is defenseless against brute force attacks
( ) It will stop spam for two weeks and then weâ(TM)ll be stuck with it
( ) Users of email will not put up with it
( ) Microsoft will not put up with it
( ) The police will not put up with it
( ) Requires too much cooperation from spammers
( ) Requires immediate total cooperation from everybody at once
( ) Many email users cannot afford to lose business or alienate potential employers
( ) Spammers donâ(TM)t care about invalid addresses in their lists
( ) Anyone could anonymously destroy anyone elseâ(TM)s career or business

Specifically, your plan fails to account for

( ) Laws expressly prohibiting it
( ) Lack of centrally controlling authority for email
( ) Open relays in foreign countries
( ) Ease of searching tiny alphanumeric address space of all email addresses
( ) Asshats
( ) Jurisdictional problems
( ) Unpopularity of weird new taxes
( ) Public reluctance to accept weird new forms of money
( ) Huge existing software investment in SMTP
( ) Susceptibility of protocols other than SMTP to attack
( ) Willingness of users to install OS patches received by email
( ) Armies of worm riddled broadband-connected Windows boxes
( ) Eternal arms race involved in all filtering approaches
( ) Extreme profitability of spam
( ) Joe jobs and/or identity theft
( ) Technically illiterate politicians
( ) Extreme stupidity on the part of people who do business with spammers
( ) Dishonesty on the part of spammers themselves
( ) Bandwidth costs that are unaffected by client filtering
( ) Outlook

and the following philosophical objections may also apply:

( ) Ideas similar to yours are easy to come up with, yet none have ever
been shown practical
( ) Any scheme based on opt-out is unacceptable
( ) SMTP headers should not be the subject of legislation
( ) Blacklists suck
( ) Whitelists suck
( ) We should be able to talk about Viagra without being censored
( ) Countermeasures should not involve wire fraud or credit card fraud
( ) Countermeasures should not involve sabotage of public networks
( ) Countermeasures must work if phased in gradually
( ) Sending email should be free
( ) Why should we have to trust you and your servers?
( ) Incompatiblity with open source or open source licenses
( ) Feel-good measures do nothing to solve the problem
( ) Temporary/one-time email addresses are cumbersome
( ) I donâ(TM)t want the government reading my email
( ) Killing them that way is not slow and painful enough

Furthermore, this is what I think about you:

( ) Sorry dude, but I donâ(TM)t think it would work.
( ) This is a stupid idea, and youâ(TM)re a stupid person for suggesting it.
( ) Nice try, assh0le! Iâ(TM)m going to find out where you live and burn your house down!

Re:we can fix this

[RabidReindeer]

Hey! Our product line is created, maintained and supported by the finest professionals $1.75/hour can buy!

You want me to what now?

[Daetrin]

[This person is an expert at hacking systems using links!]

"Click through that link to see examples of this abuse in action"

o_O

(And yes, i'm aware that URL links are not the same as symbolic links, but the phrasing is still amusing.)

.

Re:As the old saying goes...

[lucm]

On proper time systemd has added symlinks, a (somehow) worthwhile command line, non-graphic environment, the ability to remotely manage, declarative-based configuration management...

It's only they are reinventing all these things on their own, forgetting about how did they came to be and, of course, not caring about the way those facilities have been used and abused in the past.

I think it was Henry Spencer the one that said "Those who do not understand Unix are condemned to reinvent it, poorly."

Hehe