openssh unix dev - Oct 2021 - Disable tracing on FreeBSD using procctl. (OpenSSH Portable 8.8)

On Fri, 15 Oct 2021 at 10:48, mike tancsa <mike at sentex.net>
wrote:
>      With the commit below, OpenSSH portable 8.8 doesnt seem to work
> with sftp on FreeBSD with RELENG_12 and RELENG_13.  sftp errors out with
>
> sftp-server[89445]: fatal: unable to make the process untraceable
As a data point,our github CI tests on FreeBSD 12 & 13 VMs and our
test suite passes on them.  I have confirmed that both set
HAVE_PROCCTL and that the code is being compiled in and just run a
manual test on 13 which worked.

FreeBSD fbsd12 12.2-RELEASE-p3 FreeBSD 12.2-RELEASE-p3 GENERIC  amd64

FreeBSD fbsd13 13.0-RELEASE FreeBSD 13.0-RELEASE #0
releng/13.0-n244733-ea31abc261f: Fri Apr  9 04:24:09 UTC 2021
root at releng1.nyi.freebsd.org:/usr/obj/usr/src/amd64.amd64/sys/GENERIC
amd64

-- 
Darren Tucker (dtucker at dtucker.net)
GPG key 11EAA6FA / A86E 3E07 5B19 5880 E860  37F4 9357 ECEF 11EA A6FA (new)
    Good judgement comes with experience. Unfortunately, the experience
usually comes from bad judgement.

On Fri, 15 Oct 2021 at 11:44, Darren Tucker <dtucker at dtucker.net>
wrote:
[...]
> As a data point,our github CI tests on FreeBSD 12 & 13 VMs and our
> test suite passes on them.  I have confirmed that both set
> HAVE_PROCCTL and that the code is being compiled in and just run a
> manual test on 13 which worked.
I just patched the VM images (usually the VMs are ephemeral) and it
also passed on those:

FreeBSD fbsd12 12.2-RELEASE-p7 FreeBSD 12.2-RELEASE-p7 GENERIC  amd64

FreeBSD fbsd13 13.0-RELEASE-p4 FreeBSD 13.0-RELEASE-p4 #0: Tue Aug 24
07:33:27 UTC 2021
root at amd64-builder.daemonology.net:/usr/obj/usr/src/amd64.amd64/sys/GENERIC
 amd64

-- 
Darren Tucker (dtucker at dtucker.net)
GPG key 11EAA6FA / A86E 3E07 5B19 5880 E860  37F4 9357 ECEF 11EA A6FA (new)
    Good judgement comes with experience. Unfortunately, the experience
usually comes from bad judgement.

On 10/14/2021 8:44 PM, Darren Tucker wrote:
> On Fri, 15 Oct 2021 at 10:48, mike tancsa <mike at sentex.net> wrote:
>>       With the commit below, OpenSSH portable 8.8 doesnt seem to work
>> with sftp on FreeBSD with RELENG_12 and RELENG_13.  sftp errors out
with
>>
>> sftp-server[89445]: fatal: unable to make the process untraceable
> As a data point,our github CI tests on FreeBSD 12 & 13 VMs and our
> test suite passes on them.  I have confirmed that both set
> HAVE_PROCCTL and that the code is being compiled in and just run a
> manual test on 13 which worked.
>
Thanks, I am not sure why its failing on these particular instances. I 
tried just now on a separate box that has not had a previous version 
installed and it doesnt show the same behaviour. I will keep looking to 
see whats going on.

 ??? ---Mike

On 10/14/2021 5:44 PM, Darren Tucker wrote:
> On Fri, 15 Oct 2021 at 10:48, mike tancsa <mike at sentex.net> wrote:
>>       With the commit below, OpenSSH portable 8.8 doesnt seem to work
>> with sftp on FreeBSD with RELENG_12 and RELENG_13.  sftp errors out
with
>>
>> sftp-server[89445]: fatal: unable to make the process untraceable
> 
> As a data point,our github CI tests on FreeBSD 12 & 13 VMs and our
> test suite passes on them.  I have confirmed that both set
> HAVE_PROCCTL and that the code is being compiled in and just run a
> manual test on 13 which worked.
> 
> FreeBSD fbsd12 12.2-RELEASE-p3 FreeBSD 12.2-RELEASE-p3 GENERIC  amd64
> 
> FreeBSD fbsd13 13.0-RELEASE FreeBSD 13.0-RELEASE #0
> releng/13.0-n244733-ea31abc261f: Fri Apr  9 04:24:09 UTC 2021
> root at releng1.nyi.freebsd.org:/usr/obj/usr/src/amd64.amd64/sys/GENERIC
> amd64
> 
I think the tests may need to be improved as pid==0 represents a pseudo 
kernel process.
> #include <sys/procctl.h>                                             
> #include <err.h>                                                     
> #include <unistd.h>                                                  
>                                                                      
> int                                                                  
> main(void)                                                           
> {                                                                    
>         int disable_trace = PROC_TRACE_CTL_DISABLE;                  
>                                                                      
>         if (procctl(P_PID, getpid(), PROC_TRACE_CTL, &disable_trace))
>             err(1, "procctl");
>                                                                      
>         return 0;                                                    
> }                                                                    
With 0 it runs through truss fine. (Which I don't think it should but 
I'll take that up with FreeBSD)
> procctl(P_PID,0,PROC_TRACE_CTL,0x7fffffffe478)   = 0 (0x0)

With getpid() truss gives an error since the process is already traced.
> getpid()                                         = 77976 (0x13098)     
> procctl(P_PID,77976,PROC_TRACE_CTL,0x7fffffffe478) ERR#16 'Device
busy'


-- 
Bryan Drewery
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