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Re: SFTP question

On 12/26/2014 1:51 AM, Reco wrote:
>  Hi.
> On Thu, Dec 25, 2014 at 09:19:49PM -0500, Jerry Stuckle wrote:
>> On 12/25/2014 11:23 AM, Reco wrote:
>>>  Hi.
>>> On Thu, Dec 25, 2014 at 10:18:11AM -0500, Jerry Stuckle wrote:
>>>> On 12/25/2014 8:54 AM, Andre N Batista wrote:
>>>>> On Wed, Dec 24, 2014 at 11:18:36AM -0500, Jerry Stuckle wrote:
>>>>>> On 12/24/2014 2:01 AM, Danny wrote:
>>>>>>> Hi Bob,
>>>>>>> You were right, SFTP, FileZilla and Proftp confused the hell out of me ... lol
>>>>>>> ... I must add in my defense though that I was in a state of panic after syslog
>>>>>>> warned me of an attack by someone during the night via ssh ... So I frantically tried to
>>>>>>> make ssh and Proftp work together without reading the online guides properly ...
>>>>>>> Sometimes one does stupid things ... lol ...
>>>>>>> Thanks for everyone's input ...
>>>>>>> Danny
>>>>>> Danny,
>>>>>> As a side note - don't panic over SSH attacks.  Instead, use the right
>>>>>> tools and techniques to secure your systems and let them do their jobs.
>>>>>>  Monitor the server to ensure you didn't leave any holes.
>>>>>> For instance, Fail2ban blocked over 100 IP's from accessing one of my
>>>>>> servers on yesterday alone.  The attacks keep coming, but none have ever
>>>>>> succeeded.
>>>>> Not surprisingly, I mostly agree with the advice given here, we all
>>>>> learnt from the same sources.
>>>>> Nonetheless, since you claimed to be using puTTy for your ssh needs on
>>>>> windows, I should warn you that recently someone claimed to be able to
>>>>> use it as a means to compromise a ssh server:
>>>>> http://seclists.org/fulldisclosure/2014/Dec/42
>>>>> I have not put it's claims to test, but since the last stable version of
>>>>> putty dates back one year
>>>>> http://www.chiark.greenend.org.uk/~sgtatham/putty/changes.html
>>>>> and since there seems to be no mention of this bug on putty bug tracking
>>>>> system
>>>>> http://www.chiark.greenend.org.uk/~sgtatham/putty/wishlist/
>>>>> I guess you should deploy it at large, at least until it has been fixed.
>>>>> Good luck!
>>>> It's possible to corrupt ANY program if you replace a .dll or .so with
>>>> your own code.
>>> Indeed. But the program which can be tricked to use your own library
>>> instead of a system one - is called vulnerable usually. I don't mean
>>> LD_PRELOAD or LD_LIBRARY_PATH tricks but something akin to a braindead
>>> Windows behavior (which looks for libraries in a current dir first).
>>> Reco
>> ANY program is vulnerable if care isn't taken to ensure a download
>> contains the right files.  That's why there are checksums.
> Ok, I can agree with that.
>> So according to your definition, any program - including the kernel - is
>> vulnerable to such an attack, and should be classified as such.  This is
>> true for ANY operating system - not just Windows or Linux.
> I disagree with you. All one needs to do is to put one single RPATH
> entry into the compiled binary by mistake, and … then you have things
> like #754278.
> Putting a malicious library at known user-writable location is one
> thing, loading a kernel module as a root (I presume that's what you've
> meant with your kernel reference) is another thing.
> Reco

754278 has nothing to do with substituting a .so or .dll.  It only deals
with where a program looks for binaries.

And it is perfectly possible to corrupt the kernel by substituting a .so
the kernel uses in Linux.  Nothing to do with loading a new module.

The new library will take effect the next reboot.  In this way, Windows
is much more secure because, unlike in Linux, you cannot replace an
in-use library.  It requires a bunch of gyrations and the replacement is
done on restart.

And who said anything about user-writable?  Upgrades in Debian are
performed by root or someone with root privileges.


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