Hi Brian,
you actually hinted me at sth. : powershell.exe Start-Process bash
\"-c\",\"\'echo hello world \>`readlink /proc/$$/fd/1`\;sleep 10\'\"
works as well.
I verified this:
>echo hello >/proc/3235/fd/0
-bash: echo: write error: Bad file descriptor
>echo hello >`readlink /proc/3235/fd/0`
works!?
Am I missing sth about symlinks?
BR
Till
Till Riedel [TM] @ 20.06.2019 (21:49) :
Hi Brian,
thanks for the reply.
But proc/$$/fd/1 references the callers stdout and not the callees as
/dev/stdout or /proc/self/fd/2 if called from eg. from bash, because
it is expanded before the call.
What I was able to do is to inject messages into the callers stdout
and read from the callers stdin, which is when executing under
elevated priviledges (the behaviour you would want for a sudo).
As said echo >/proc/$$/fd/1 hello world is not the problem and works
fine as you said as well. (I probably should not have said strangely
in the first place, because it is a whole different deal...)
BR
Till
Brian Inglis @ 16.06.2019 (17:42) :
On 2019-06-15 12:27, Till Riedel wrote:
I have been using a very handy sudo hack, that broke lately (I
think) when
updating cygwin: https://github.com/imachug/win-sudo
The trick is to spawn an elevated process using powershell and hook
up the
calling file descripters. I now get "write error: Bad file descriptor"
To reproduce call:
powershell.exe Start-Process bash \"-c\",\"\'echo \>\>/proc/$$/fd/1
hello
world\;sleep 10\'\"
IMHO this used to work in former versions (print out hello world on
the calling
shell). Strangely
bash -c "echo >/proc/$$/fd/1 hello world"
works. So my initial guess is that is has to do with the decoupling
of Cygwin
PIDs from Windows PIDs, but there were also changes in the proc file
system...
Thanks a lot in advance for any help/thoughts!
Given:
$ bash -c 'ls -dglo /dev/std* /proc/self /proc/$$ /proc/self/fd/[012]'
lrwxrwxrwx 1 15 May 14 2013 /dev/stderr -> /proc/self/fd/2
lrwxrwxrwx 1 15 May 14 2013 /dev/stdin -> /proc/self/fd/0
lrwxrwxrwx 1 15 May 14 2013 /dev/stdout -> /proc/self/fd/1
dr-xr-xr-x 3 0 Jun 16 01:37 /proc/23846
lrwxrwxrwx 1 0 Jun 16 01:37 /proc/self -> 23846
lrwxrwxrwx 1 0 Jun 16 01:37 /proc/self/fd/0 -> /dev/pty0
lrwxrwxrwx 1 0 Jun 16 01:37 /proc/self/fd/1 -> /dev/pty0
lrwxrwxrwx 1 0 Jun 16 01:37 /proc/self/fd/2 -> /dev/pty0
the following seems to work as expected:
$ powershell Start-Process bash \"-c\",\"\'echo \>\>/dev/stdout hello
world\;sleep 10\'\"
--
KIT- Research University in the Helmholtz Association
Dr.-Ing. Till Riedel
Lab Leader TECO, SDSC-BW/SDIL (AR)
Karlsruhe Institute of Technology (KIT)
Institute of Telematics (TM)
Pervasive Computing Systems - Prof. Beigl
Bldg. 07.07., Room 211
Vincenz Prießnitz Str. 1, 76131 Karlsruhe
+49 (0)721 608 41706
www.teco.kit.edu/~riedel
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