[mosh-users] mosh-server fails to start on grsecurity kernel

[Deven Lahoti]

Well, it turns out that the git version of mosh works perfectly, so I have
no idea what would be causing the problem. If you'd like, I can modify the
1.2.5-r1 sources to get the coredump, but I don't think it'll be of much
use to any of us, since the problem is fixed on both ends.

Thanks,
Deven

On Tue, Jun 7, 2016 at 8:52 PM, John Hood <cgull at glup.org> wrote:

> Oops, I'm forgetting two rather important things, sorry.
>
> * The --local flag is only in mosh master, not yet in any release (though
> 1.2.6 is coming soon).  Available on GitHub near you.  If you don't want to
> mess with source you can run mosh-client and mosh-server manually as
> documented on <https://mosh.mit.edu/> <https://mosh.mit.edu/>.
>
> * mosh-server itself disables coredumps to protect its cryptographic
> secrets.  Disabling that requires editing source and rebuilding mosh-server.
>
> regards,
>
>   --jh
> On 06/07/2016 20:21, Deven Lahoti wrote:
>
> mosh --local just gives "unknown option", and I can't figure out how to
> enable coredumps for mosh-server - coredumps work for everything else, so
> I'm not sure why they're disabled here.
>
> On Tue, Jun 7, 2016 at 9:39 AM, John Hood <cgull at glup.org> wrote:
>
>> Try running
>>
>> strace -ffo trace mosh --local 127.0.0.1
>>
>> on that server after enabling coredumps. That's not exactly the same as
>> normal execution, since it doesn't use ssh, but it's useful for issues like
>> this one.
>>
>> regards,
>>
>>   --jh
>>
>> On Jun 7, 2016, at 12:56 AM, Deven Lahoti < <deywos at mit.edu>
>> deywos at mit.edu> wrote:
>>
>> Neither strace nor gdb will give me a backtrace, since they both lose
>> track of it when it forks, but the failure happens after forking. For some
>> reason, systemd says that coredumps are disabled for the process, so I
>> can't get one of those either.
>> On Jun 7, 2016 00:31, "Alex Chernyakhovsky" < <achernya at mit.edu>
>> achernya at mit.edu> wrote:
>>
>>> Unfortunately, that's not much to go on. Could you grab the core file
>>> and get a backtrace? I'm assuming some syscall (probably malloc?)
>>> failed.
>>>
>>> Sincerely,
>>> -Alex
>>>
>>> On Tue, Jun 7, 2016 at 12:18 AM, Deven Lahoti <deywos at mit.edu> wrote:
>>> > I don't think that's the problem, since it's now giving me:
>>> > mosh-server[21489]: segfault at 0 ip           (null) sp
>>> 00007fffffffcbd8
>>> > error 14 in mosh-server[555555554000+60000]
>>> >
>>> > On Mon, Jun 6, 2016 at 11:42 PM, Alex Chernyakhovsky <achernya at mit.edu
>>> >
>>> > wrote:
>>> >>
>>> >> I think the offending line is
>>> >>
>>> >> Jun 06 22:32:19 <hostname> kernel: PAX: From 18.X.X.X: execution
>>> >> attempt in: (null), 00000000-00000000 00000000
>>> >> Jun 06 22:32:19 <hostname> kernel: PAX: terminating task:
>>> >> /usr/bin/mosh-server(mosh-server):12505, uid/euid: XXXX/XXXX, PC:
>>> >>       (nil), SP: 000003844385a508
>>> >>
>>> >> mosh-server needs to fork and exec to start subprocesses, and your
>>> >> kernel/configuration doesn't consider mosh-server to be in the
>>> >> whitelist.
>>> >>
>>> >> Sincerely,
>>> >> -Alex
>>> >>
>>> >>
>>> >> On Mon, Jun 6, 2016 at 11:30 PM, Deven Lahoti <deywos at mit.edu> wrote:
>>> >> > Hi, when trying to connect to my machine running Gentoo Hardened on
>>> >> > kernel
>>> >> > 4.4.8, mosh-server fails to start. Here are the logs (modified to
>>> remove
>>> >> > personal info) [ <http://web.mit.edu/deywos/www/mosh.log>
>>> http://web.mit.edu/deywos/www/mosh.log]. I'm not really
>>> >> > sure
>>> >> > what the problem is, and I don't know much about how mosh works, so
>>> I
>>> >> > was
>>> >> > hoping someone here could help me out.
>>> >> >
>>> >> > Thanks,
>>> >> > Deven
>>> >> >
>>> >> > _______________________________________________
>>> >> > mosh-users mailing list
>>> >> > mosh-users at mit.edu
>>> >> > http://mailman.mit.edu/mailman/listinfo/mosh-users
>>> >> >
>>> >
>>> >
>>>
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>
>
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