From b267e5c30589404047bc0871323c09757c9df692 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Marek=20Marczykowski-G=C3=B3recki?= Date: Sat, 5 Mar 2016 00:28:56 +0100 Subject: [PATCH] qrexec: write service stderr to both syslog and caller In case of some services it makes much sense for caller to receive also stderr in addition to stdout. For example: - qubes.VMShell (stderr required for salt-ssh over qrexec) - qubes.OpenInVM - especially when called to DispVM - otherwise diagnosing errors can be hard And generally all sort of error reporting (the purpose of stderr). It would ease debugging - instead of message "error occurred, check here and there for more details", it could be "error occurred: the reason". Fixes QubesOS/qubes-issues#1808 --- qrexec/qubes-rpc-multiplexer | 17 +++++++++++++---- 1 file changed, 13 insertions(+), 4 deletions(-) diff --git a/qrexec/qubes-rpc-multiplexer b/qrexec/qubes-rpc-multiplexer index e772d27..ecd9bc9 100755 --- a/qrexec/qubes-rpc-multiplexer +++ b/qrexec/qubes-rpc-multiplexer @@ -1,9 +1,18 @@ #!/bin/sh -mkfifo /tmp/qrexec-rpc-stderr.$$ -logger -t "$1-$2" -f /tmp/qrexec-rpc-stderr.$$ >/dev/null 2>&1 /tmp/qrexec-rpc-stderr.$$ -rm -f /tmp/qrexec-rpc-stderr.$$ +# write stderr to both calling party and local log; be very careful about +# closing file descriptors here - if either stdout or stderr will not be closed +# when service process does the same - service call will hang (waiting for EOF +# on stdout/stderr) +stderr_pipe=/tmp/qrexec-rpc-stderr.$$ +mkfifo $stderr_pipe +# tee can't write to file descriptor, nor /proc/self/fd/2 (EXIO on open) +return_stderr_pipe=/tmp/qrexec-rpc-stderr-return.$$ +mkfifo $return_stderr_pipe +{ cat <$return_stderr_pipe >&2 2>/dev/null; rm -f $return_stderr_pipe; } & +{ tee $return_stderr_pipe 2>/dev/null <$stderr_pipe |\ + logger -t "$1-$2" >/dev/null 2>&1; rm -f $stderr_pipe; } & +exec 2>$stderr_pipe QUBES_RPC=/etc/qubes-rpc LOCAL_QUBES_RPC=/usr/local/etc/qubes-rpc