On 25-10-19 13:09, Andreas Schneider wrote:
On Friday, 25 October 2019 11:11:32 CEST Alexander Bokovoy wrote:
> On pe, 25 loka 2019, Kees Bakker wrote:
>> On 24-10-19 16:12, Alexander Bokovoy wrote:
>>> On to, 24 loka 2019, Kees Bakker via FreeIPA-users wrote:
>>>> Hey,
>>>>
>>>> With x2go [1] you can start a remote desktop. Going from UNIX (client)
to
>>>> UNIX (server) it will use SSH behinds the scenes.
>>>>
>>>> However, on a IPA client the x2goclient command fails with a segfault
>>>> (somewhere in a ssh library). This is caused by the modified
>>>> /etc/ssh/ssh_config. More specifically this
>>>>
>>>> ProxyCommand /usr/bin/sss_ssh_knownhostsproxy -p %p %h
>>>>
>>>> When you disable this line the x2go connection succeeds.
>>>>
>>>> [1]
https://wiki.x2go.org/doku.php
>>> If you could install debug packages and generate a backtrace, that would
>>> be great as it would help to understand where it happens. Thanks in
>>> advance!
>> Hey Alexander,
>>
>> The segfault is in a library of the libssh-4 package. I don't know if that
>> is something you wanted to be involved with. Anyway, here is the stack
>> strace of the segfault.
> Thanks. So the crash is in ssh_poll_set_events(). Andreas, do you have
> any ideas?
Where is libssh installed from? It looks like this is libssh 0.8.0.
It's Ubuntu 18.04.3 and the libraries are from the normal
distribution source.
https://packages.ubuntu.com/search?keywords=libssh
# dpkg -l libssh\*|cat
Desired=Unknown/Install/Remove/Purge/Hold
| Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend
|/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
||/ Name Version Architecture Description
+++-=====================-==================================-============-===================================
ii libssh-4:amd64 0.8.0~20170825.94fa1e38-1ubuntu0.2 amd64 tiny C SSH library
(OpenSSL flavor)
ii libssh-4-dbgsym:amd64 0.8.0~20170825.94fa1e38-1ubuntu0.2 amd64 debug symbols
for libssh-4
un libssh-dbg <none> <none> (no description
available)
ii libssh-gcrypt-4:amd64 0.8.0~20170825.94fa1e38-1ubuntu0.2 amd64 tiny C SSH
library (gcrypt flavor)
ii libssh2-1:amd64 1.8.0-1 amd64 SSH2 client-side
library
# apt policy libssh-4
libssh-4:
Installed: 0.8.0~20170825.94fa1e38-1ubuntu0.2
Candidate: 0.8.0~20170825.94fa1e38-1ubuntu0.2
Version table:
*** 0.8.0~20170825.94fa1e38-1ubuntu0.2 500
500
http://nl.archive.ubuntu.com/ubuntu bionic-updates/main amd64 Packages
500
http://security.ubuntu.com/ubuntu bionic-security/main amd64 Packages
100 /var/lib/dpkg/status
0.8.0~20170825.94fa1e38-1build1 500
500
http://nl.archive.ubuntu.com/ubuntu bionic/main amd64 Packages
>> segfault at 4 ip 00007f6e7e0d5eeb sp 00007f6e64e6ea88 error 6 in
>> libssh.so.4.5.0
>>
>> After installing the dgbsym package and running from gdb I could get a
>> stack trace
>>
>> Thread 6 "SshMasterConnec" received signal SIGSEGV, Segmentation
fault.
>> [Switching to Thread 0x7fffdf1a0700 (LWP 14736)]
>> 0x00007ffff7b89eeb in ssh_poll_set_events (p=0x7fffd40076b0, events=4) at
>> ./src/poll.c:349 349 ./src/poll.c: No such file or directory.
>> (gdb) where
>> #0 0x00007ffff7b89eeb in ssh_poll_set_events (p=0x7fffd40076b0, events=4)
>> at ./src/poll.c:349 #1 0x00007ffff7b8d3c8 in ssh_socket_unbuffered_write
>> (len=<optimized out>, buffer=<optimized out>, s=0x7fffd4003850) at
>> ./src/socket.c:574
>> #2 ssh_socket_nonblocking_flush (s=s@entry=0x7fffd4003850) at
>> ./src/socket.c:667 #3 0x00007ffff7b8d4c4 in ssh_socket_write
>> (s=0x7fffd4003850, buffer=<optimized out>, len=len@entry=64) at
>> ./src/socket.c:628
>> #4 0x00007ffff7b846c3 in ssh_packet_write (session=0x7fffd4004bc0,
>> session=0x7fffd4004bc0) at ./src/packet.c:1316 #5 packet_send2
>> (session=session@entry=0x7fffd4004bc0) at ./src/packet.c:1386 #6
>> 0x00007ffff7b85315 in ssh_packet_send
>> (session=session@entry=0x7fffd4004bc0) at ./src/packet.c:1411 #7
>> 0x00007ffff7b72d69 in channel_write_common (channel=0x7fffd40112e0,
>> data=0x7fffdf11fce0, len=6, is_stderr=0) at ./src/channels.c:1357
>> #8 0x0000555555640cc3 in ?? ()
>> #9 0x0000555555644745 in ?? ()
>> #10 0x00007ffff581de3c in ?? () from
>> /usr/lib/x86_64-linux-gnu/libQtCore.so.4 #11 0x00007ffff558b6db in
>> start_thread (arg=0x7fffdf1a0700) at pthread_create.c:463 #12
>> 0x00007ffff4d1388f in clone () at
>> ../sysdeps/unix/sysv/linux/x86_64/clone.S:95