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OpenSSH: client bug CVE-2016-0777

undeadly.org

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131–140 of 226 posts

Re: OpenSSH: client bug CVE-2016-0777

#131

Post by rkeene2 »

devin wrote: post #116

Am I correct that YubiKey users are unaffected by this vulnerability? As I understand it, the private key never enters into memory.

Using any sort of hardware security module, such as a smartcard (which some YubiKey devices can operate as) will not allow your private key to be compromised because you have no access to your private key -- it's on a whole separate computer (the HSM) and your only access to it is by sending APDUs to that computer. For a typical smartcard the only thing you can ask it to do with your private key is to perform cryptographic operations on data with it. Many smartcard applets require that you authenticate yourself to the smartcard before they will even do that.

I use a smartcard with a NIST SP 800-73 applet on it for all my SSH (and TLS) sessions and do not have any other SSH keys.

Re: OpenSSH: client bug CVE-2016-0777

#132

Post by hackuser »

Skunkleton wrote: post #128
Corrado wrote: post #121

Just a note: the default AWS Linux AMI doesn't seem to have this problem on the server side. Connecting to one of my EC2 instances with verbose on I get the following message: debug1: Roaming not allowed by server Yeah! AWS Linux for the win. :)

OpenSSH server doesn't support roaming. This is a client only issue. The problem is that your connection could be MITM'd by someone looking to exploit this bug.

> your connection could be MITM'd

MITM isn't a risk, if I understand this statement in the undeadly.org announcement:

   The authentication of the server host key prevents exploitation
   by a man-in-the-middle, so this information leak is restricted
   to connections to malicious or compromised servers.

Re: OpenSSH: client bug CVE-2016-0777

#133

Post by semi-extrinsic »

aexaey wrote: post #130
semi-extrinsic wrote: post #125

Earlier quoted context omitted.

Does anyone know how this interacts with ProxyCommand? If I fix this in ~/.ssh/config on my laptop, and I ssh to hostB through hostA using Host hostB ... ProxyCommand ssh hostA -W %h:%p in the config on my laptop, do I also need to fix it on hostA?

CVE-2016-0777 doesn't interact with ProxyCommand in any special way. That said, after connecting to hostB with your example config above you will have 2 ssh sessions: 1) from your client to hostA 2) from your client to hostB So to answer your question - no, vulnerable client on hostA is not a problem (or at least not in this particular use-case).

> Vulnerable client on hostA is not a problem.

Ok, that's what I was wondering. Thanks.

Re: OpenSSH: client bug CVE-2016-0777

#136

Post by protomyth »

scardine wrote: post #98
protomyth wrote: post #78

Check me on this, so this is a client-side problem only, so ssh-ing into only know servers shouldn't be an issue and clients cannot cause problems for servers?

If an enemy takes control of just one of the hosts you ssh into, he will get your private key and can use it to ssh into any other box where you use RSAAuthentication.

I already added the mitigation, but I wondering if my servers can be patched on the weekend.

Re: OpenSSH: client bug CVE-2016-0777

#137

Post by merqurio »

DrRobinson wrote: post #23
merqurio wrote: post #17

Earlier quoted context omitted.

Is there any way to update openssh on my side, without waiting to apple ? Is this enough ? https://mochtu.de/2015/01/07/updating-openssh-on-mac-os-x-10...

You can patch it with: # echo 'UseRoaming no' >> /etc/ssh/ssh_config or $ echo "UseRoaming no" >> ~/.ssh/config

Thanks DrRobinson ! I added it to my .ssh/config

Re: OpenSSH: client bug CVE-2016-0777

#138

Post by tomku »

Corrado wrote: post #121

Just a note: the default AWS Linux AMI doesn't seem to have this problem on the server side. Connecting to one of my EC2 instances with verbose on I get the following message: debug1: Roaming not allowed by server Yeah! AWS Linux for the win. :)

That message actually means that your client has roaming enabled and is therefore vulnerable.

Re: OpenSSH: client bug CVE-2016-0777

#139

Post by merqurio »

rsync wrote: post #95
merqurio wrote: post #5

As far as I know, this will affect any OSX, am I right ?

It will affect any OSX that is new enough to have that code in it. Same is true with other OS. For instance, on an older, patched FreeBSD 7.2 system, we see this result: /root/.ssh/config: line 1: Bad configuration option: UseRoaming /root/.ssh/config: terminating, 1 bad configuration option ... which means that sshd predates the roaming code. I haven't tested, but I'll bet my snow leopard workstation also predates t…

Thanks !

Re: OpenSSH: client bug CVE-2016-0777

#140

Post by tomjen3 »

aexaey wrote: post #134

Does anybody else find this eerily reminiscent of heartbleed? Obscure broken feature that nobody uses (or needs) is enabled by default and allow private keys to leak.

It is OpenSSH, the clown car of bugs in obscure features nobody uses.

Does anybody know if LibraSSL has released an SSH client yet? I can't code well enough to make security code safe, so I won't be able to help them out on it, but it sounds more and more like OpenSSH can't either.

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