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Comments: 225 +- IT: Critical Flaw Discovered In DD-WRT on Friday July 24 2009, @08:58AM
Posted
by
kdawson
on Friday July 24 2009, @08:58AM
from the my-router-my-self dept.
from the my-router-my-self dept.
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MagicM writes "A critical flaw has been discovered in DD-WRT, a Linux based alternative open source firmware for WLAN routers such as the fan-favorite Linksys WRT54GL. The flaw can give an attacker instant root access to the router merely by embedding an image with a specially crafted URL in a Web page (CSRF attack)." The linked page notes that a fix is being rolled out (build 12533) and gives firewall rules to thwart the attack if the fix is not available yet for a particular device.
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This is a common stack in wifi APs (Score:2, Insightful)
Yes, there's a fix for this, but what is the likelihood of every person who owns a Wifi router fixing this flaw?
We talk about the dangers of homogeny, but this is exactly the type of thing that homogeny causes. All the routers with DD-WRT implemented to save costs, but in the end everyone is screwed.
Just because we love Linux doesn't mean that we should sacrifice the entire ecosystem to that love. We need to nurture other implementations to prevent this type of virus from wiping out our entire networking in
Mod Parent Up (Score:3, Interesting)
Re: (Score:3, Insightful)
If people just disabled remote admin (which you should do anyway) and used different router IPs (e.g. not 192.168.1.1 or the usual), then attackers either need to do additional stuff to figure out what your default gateway is (and thus presumably your router IP), or they need to have significant control of a PC attached to the internal network (and presumably able to access the router webpage).
Re: (Score:3, Informative)
>If people just disabled remote admin (which you should do anyway)
FYI, the exploit is Internet-ready even if you turn off remote management.
It's in the article, if you read it. Webpages (or flash, etc) can just craft a request to exploit this and in the process, turn remote shell ON.
Web-managed routers will always be LESS secure than router types managed via local telnet or ssh. Such designs are immune to browser and cross site attacks... but they're more difficult to manage for novice users, which is w
Re: (Score:3, Funny)
Re:This is a common stack in wifi APs (Score:5, Insightful)
1. If people not only updated the firmware on their router, but had to do hacks to get it on there, don't you think they're probably at least a tad more likely to keep the firmware up to date than Joe Blammo with the factory firmware installed?
2. Do you think DD-WRT was really all that much more susceptible to having a flaw than, say, something from Cisco? Or, by the same thought process, do you think open source Linux is inherently more vulnerable than Windows?
3. Homogeny? Huh?! Do you mean the homogeny that's defined has "a significant portion of huge nerds (though certainly not even close to a majority) uses this software" ? How many routers are being used in homes and small businesses around the world? You think enough of them are running DD-WRT to call it a homogeny? Name a router that you think has more instances of DD-WRT installed than the factory firmware.
Software bugs happen. You don't need to get all philosophical about it. And besides, this is no more dangerous than the much larger number of people probably still using the default password on their router, and probably only slightly more dangerous than the huge number of people who don't have any kind of security. Relax.
Parent
Re:This is a common stack in wifi APs (Score:5, Informative)
3. Homogeny? Huh?! Do you mean the homogeny that's defined has "a significant portion of huge nerds (though certainly not even close to a majority) uses this software" ? How many routers are being used in homes and small businesses around the world? You think enough of them are running DD-WRT to call it a homogeny? Name a router that you think has more instances of DD-WRT installed than the factory firmware.
WRT54GL
http://www.linksysbycisco.com/US/en/products/WRT54GL
Parent
Re: (Score:2)
Re:This is a common stack in wifi APs (Score:5, Insightful)
If you read the comments on NewEgg.com for that router model, not everyone mentions DD-WRT. Some use other 3rd party firmwares like Tomato or Open-WRT or custom builds. And believe it or not, some even write a positive review for the default factory firmware. The nice thing about that model ("L" version) is the extra memory headroom. Earlier models were stripped and crippled to run a really crappy default firmware from Linksys. BitTorrent crashes these small memory models often.
http://en.wikipedia.org/wiki/Linksys_WRT54G_series#Hardware_and_revisions [wikipedia.org]
Parent
Re:This is a common stack in wifi APs (Score:4, Informative)
So you agree that earlier models which were released shortly before the WRT54GL, were stripped and crippled. Except for the part where you said he was wrong you just agreed with everything the grandparent poster said.
Parent
Re: (Score:3, Interesting)
I hope the following tale satisfies your curiosity.
Back in the day, you had a company named Linksys. They made excellent home routers. I dare say the best you could get on the market. They release several versions of a certain wireless router, model WRT54G. People everywhere rejoice, because they can hack away at this machine to their heart's content. Modding the firmware, modding the hardware. You name it.
During this period, a certain, shall we say, rather shitty manufacturer of 'Enterprise' routers, named
Re:This is a common stack in wifi APs (Score:5, Interesting)
1. If people not only updated the firmware on their router, but had to do hacks to get it on there, don't you think they're probably at least a tad more likely to keep the firmware up to date than Joe Blammo with the factory firmware installed?
You're assuming that all these people that installed dd-wrt on their router installed it on their own routers only. Not their parents, friends etc, and forgot about it.
Do most open source projects have a mailing list in which ONLY important notifications like this go out? In comparison, two years ago I bought a coffee pot from Amazon, and the manufacturer issued a recall for the pot itself. Amazon notified me via email that there was a recall for the pot and provided instructions on how to get a new replacement glass pot. Trolling forums or slashdot isn't exactly my idea of customer service.
If I had bought a Cisco/linksys router and there was a similar problem would I have been notified after registering the product?
Parent
Re: (Score:3, Informative)
"You think enough of them are running DD-WRT to call it a homogeny? Name a router that you think has more instances of DD-WRT installed than the factory firmware. "
Buffalo WHR-HP-G54DD comes with it installed by default.
Re: (Score:3, Insightful)
Yes, there's a fix for this, but what is the likelihood of every person who owns a Wifi router fixing this flaw?
We talk about the dangers of homogeny, but this is exactly the type of thing that homogeny causes. All the routers with DD-WRT implemented to save costs, but in the end everyone is screwed.
Just because we love Linux doesn't mean that we should sacrifice the entire ecosystem to that love. We need to nurture other implementations to prevent this type of virus from wiping out our entire networking infrastructure.
What is the likelihood of any flaw on any system getting patched? I don't see how a vulnerability in DD-WRT is any different than if Cisco announced a major vulnerability in one of their systems. I bet just about the same percentage would be patched.
Re: (Score:2)
In reality I would wager less of the dd-wrt routers would get patched, but only because a lot of them were deployed by non-professionals who will likely not see the news.
Re:This is a common stack in wifi APs (Score:5, Insightful)
We talk about the dangers of homogeny, but this is exactly the type of thing that homogeny causes. All the routers with DD-WRT implemented to save costs, but in the end everyone is screwed.
As opposed to using the base software from Linksys/Cisco where you don't know where the flaws lie, and if someone figures it out, it rarely ever gets published on the web openly or gets fixed soon enough in a firmware update. How is that different ? At least if you use Linux, you have people who care, and only people who care about their networks or improved experience with their routers use DD-WRT/OpenWRT/Other in the first place. Most just use the default software on their routers, which remains unpatched for a large portion of its use if at all.
Parent
Re:This is a common stack in wifi APs (Score:5, Informative)
It's hardly an issue with every wireless router. For example, the Tomato firmware is not vulnerable to this. Furthermore, most routers with DD-WRT are custom flashed, they don't come stock with it.
Parent
Re: (Score:2, Insightful)
If you had a PIX, Sonicwall, Monowall, Linksys, Netgear etc.. router and it had a similar flaw, you would be equally screwed because you still have to fix it. I hope you don't think using those products is 100% risk free and that they never need patched/updated.
It doesn't matter if 1000 people are using [Router_X] or 100 million people are using it. This type of flaw on your equipment is not safer, better, worse, or any less of a flaw or risk to you and your network regardless of the overall penetration o
Re: (Score:3, Insightful)
What you're advocating, in a round about way, is security through obscurity.
Security through obscurity doesn't work.
All security through obscurity does is propagate a false sense of security that you're safe because you've not heard any major news headlines telling you that you're vulnerable... meanwhile, you've been rooted for 3 months.
Security through obscurity works. (Score:4, Interesting)
For example: in this case if you had already changed your router's IP address, it would be harder for the attackers to figure it out. For example if you use the 10.35.79.184, the same url that can exploit thousands of other dd-wrt routers (e.g. http://192.168.1.1/etcetc ), won't work on your router. So there has to be an attack specifically targeting you[1]. Which rarely happens unless you're famous or have made yourself infamous (or well-hated amongst hacker circles).
So you have more time to update your router or even have time to wait to see if the updates don't break other stuff first.
You're not as vulnerable to zero-day attacks as other people.
Same goes for putting running sshd servers on a different port. I could use port knocking or other other stuff, but so far running it on a different port works well enough for me.
I actually have my sshd server bound on an IP and port that's unreachable from outside, and my firewall has a rule to forward outside connections to it. This way if a mistake happens and my firewall rules get disabled/cleared, ssh and other crap from outside won't work.
[1] If a top hacker was targeting you specifically, they'd probably be able to pwn you.
For example:
1) I'm sure there are many zero-day browser/plugin exploits left (just look at how fast the pwn2own winners pwn stuff - they just sacrifice one of the zero-day exploits they have).
2) I doubt most ISPs have locked their BGP stuff down, so the attackers could use "BGP eavesdropping/prefix attacks" to hijack your connections.
With 1) and 2) you'd be merrily browsing your usual sites and pwned without noticing a thing- the hacker would just pass most of the traffic on, and just alter one or two connections to exploit the relevant browser bug.
Parent
Re: (Score:3)
For example: in this case if you had already changed your router's IP address, it would be harder for the attackers to figure it out. For example if you use the 10.35.79.184, the same url that can exploit thousands of other dd-wrt routers (e.g. http://192.168.1.1/etcetc [192.168.1.1] ), won't work on your router...So you have more time to update your router or even have time to wait to see if the updates don't break other stuff first.
However,...:
Same goes for putting running sshd servers on a different port...but so far running it on a different port works well enough for me.
Of course, all it would take for someone to discover that you were running sshd on an alternate port for them to run "nmap -sV -p1-65535" on your IP address. However, that is time consuming, and most hackers are after the low hanging fruit, so instead, they "nmap -sV -p22 1.2.3.0/24
Re:It's "homogeneity" (Score:4, Funny)
langs morf. get use 2 it.
Parent
Standard Practices (Score:4, Insightful)
I was wondering: How can this attack be carried out if the external web management is turned off? From the article:
Note: The exploit can only be used directly from outside your network over the internet if you have enabled remote Web GUI management in the Administration tab. As immediate action please disable the remote Web GUI management. But that limitation could be easily overridden by a Cross-Site Request Forgery (CSFR) where a malicious website could inject the exploit from inside the browser.
The Shashdot blurb does state "The linked page notes that a fix is being rolled out (build 12533) and gives firewall rules to thwart the attack if the fix is not available yet for a particular device." but that statement doesn't curb a lot of the "The Sky is FALLING!" reactions....
Basically, I would NEVER allow remote web management of a device if it's on the internet. I believe the default for DD-WRT is to disable it as well, so you'd have to go in and tell the device that you want to enable this feature. All in all, I think for most users, this issue is a non-issue.
Re:Standard Practices (Score:5, Informative)
Maybe I'm misunderstanding, but if the exploit is "injected from inside the browser" then won't the management of the device be coming from the local interface, not the internet side?
Parent
Re: (Score:3, Informative)
The easy way is to go directly in through the remote Web GUI.
slightly harder to go in through the browser running inside the network.
Re: (Score:3, Interesting)
Re: (Score:3, Interesting)
coming from the internet, but executed from YOUR browser. That's the danger they're talking about.
Re: (Score:2, Redundant)
Alright, I'm a n00b. I didn't read that second line fully before posting regarding the injection.
Re:Standard Practices (Score:5, Informative)
Basically, I would NEVER allow remote web management of a device if it's on the internet.
Good idea, but this is a critical exploit because hackers can make an img tag load the malformed URL. If they can trick you into viewing that image, then your router will be compromised from your computer on the network. Disabling the external management will prevent internet users from compromising your router, but it is still vulnerable to local threats, as executed through the CSRF method.
Parent
Re: (Score:2, Funny)
What about dentists? Can dentists make an img tag to load the malformed URL too, or just hackers?
Worse than that (Score:4, Informative)
It's worse than a specially crafted image - there's a code injection flaw in the httpd server so merely accessing a URL that looks like "http://routerIP/cgi-bin/;command_to_execute" will do the trick. That URL can be put in a malicious tag on an HTML page and the user most likely won't even notice it.
See the Register article [theregister.co.uk] on it from a couple of days ago.
Re: (Score:2)
disable http.
only use https for router config access.
All of a sudden the attack vector is useless.
Re: (Score:3, Interesting)
Did you bother even reading the article? The code is in httpd.c, which obviously handled both types of connections. I almost hate SSL sometimes because people equate it with security -- but not encryption or integrity, but that somehow it's a magical fix-all for whatever the security flaw is. I see this kind of thinking in IT people in charge of the enterprise and it scares me. Security is not about having a setting enabled, and it certainly requires much more analysis than a simple dismissive suggestion.
DD-WRT !GPL Compliant (or open source) (Score:5, Informative)
DD-WRT just isn't compliant with the GPL on so many levels.calling it an "open source" firmware is a lie and a disgrace to the open source community.
The open source parts are OpenWRT.
Re:DD-WRT !GPL Compliant (or open source) (Score:5, Informative)
DD-WRT is Harmful [bitsum.com] to open source
Parent
Please look at this picture ... (Score:5, Interesting)
... to add a firewall-rule fixing this issue.
How did this happen? (Score:5, Interesting)
The bug resides in DD-WRT's hyper text transfer protocol daemon, which runs as root.
Whhaaat??? And the command looks like:
http://routerIP/cgi-bin/;command_to_execute
Whhaaat???
This is a bug even Adobe would be ashamed to admit. An http server, running as root, accepts arbitrary commands, without authentication, embedded in a URL? That's not a bug thats... that's a design flaw... no... that's... unbelievable!
Is there a legitimate reason that the http daemon runs as root? (It is for embedded devices...) Or that commands are accepted over HTTP GET like that?
Re:How did this happen? (Score:4, Insightful)
It's one of the reasons I don't use DD-WRT. For an Internet-facing security device, the author seems to have little regard for security.
Also, the firmware isn't really open source and the author is a humongous hypocrite.
Use Tomato [polarcloud.com] or OpenWRT [openwrt.org].
Parent
NoScript! (Score:3, Informative)
NoScript actually mitigates this vulnerability. The ABE feature, in particular:
http://noscript.net/abe/ [noscript.net]
So although I added the firewall mitigation in dd-wrt, I was pleased to find that NoScript blocked the CSRF request before it even got to the router.
Re: (Score:3, Informative)
That might help some, but what about:
1. Places that have 40 computers, running 3 different browsers.
2. Your friend/relative that comes over with their laptop
3. Embedded browsers in applications (even if they use your FF/Gecko does it load NoScript for those?)
4. That time you disabled NoScript cause something was "all fucked up", and you may as well "test"
5. What if someone got to the NoScript update servers?
6. ???
7. Loss of profit!
Only for WAN facing routers? (Score:3, Interesting)
It would be nice to know if this affects DD-WRT boxes that are not WAN-facing and are not in router mode.
I have three DD-WRT's in client bridge mode so as to provide wired connections throughout the house. They hop over WiFi to the WAN-facing router which still runs stock VxWorks. So I'd be inclined to think that my boxes are safe.
As for DD-WRT releasing a patch, gee thanks. I have two different (and old) versions of DD-WRT among the three devices and haven't touched them since installing, because upgrading requires lots of personal time with each device to reinstall and reconfigure and god knows what else and I simply don't have the time -- the whole point of setting up client bridges was to make life easier, not some sort of time-consuming exercise in obscure geek cred.
Re: (Score:2)
Your statement is exactly analogous to this one:
What the hell is a linux? Can someone find a list of actual computers that are affected by this instead of speaking in geek terms?
If you had dd-wrt, you would know.
Re:wtf is a DD-WRT? (Score:5, Informative)
Parent
Re: (Score:2, Insightful)
Linux is somewhat secure, but a LOT of the security of linux is due to a limited (unfortunately) market share. If Linux owned 30% or more of the market space for end-user goods, we'd see a HUGE influx of hacks, malware, adware, etc.
Exactly - that's the same reason why there are so many malware authors targetting Apache!
Oh wait..
Sorry to see you go (Score:4, Funny)
Greetings, I am a Linksys customers service representative. While I'm sorry to hear that you'll be leaving us, I'd like to remind you that if you have to wait for your paycheck in order to purchase a piece of home networking equipment, perhaps navigating flash based websites is the least of your worries. Have you considered going back to school?
Parent
Re: (Score:3, Insightful)
Feel free to hate Linksys for any of the other reasons. I was royally pissed off for a long time by the relentless router reboots caused by poor interaction between the logging mechanism and BitTorrent; thankfully they released fixed firmware for that
Re:Linksys suck (Score:4, Informative)
Parent
Re: (Score:3, Insightful)
Re: (Score:3, Informative)
Re: (Score:3, Informative)
It can only be remotely exploited in that case. However, it can be exploited locally if you load any page that that has a tag of the form <img src="http://192.168.1.1/cgi-bin/;reboot"> replacing 192.168.1.1 with your router's actual IP, and the reboot command with whatever command is desired. So you visit any webpage in any browser and you don't have the browser set to not load images from another domain, and you can be exploited.