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https://github.com/msantos/hexlog
Hexdump stdin and/or stdout to stderr
https://github.com/msantos/hexlog
capsicum exec fork hexdump pledge seccomp setrlimit stdio
Last synced: 16 days ago
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Hexdump stdin and/or stdout to stderr
- Host: GitHub
- URL: https://github.com/msantos/hexlog
- Owner: msantos
- License: isc
- Created: 2020-09-27T11:12:24.000Z (about 4 years ago)
- Default Branch: master
- Last Pushed: 2024-01-02T13:24:42.000Z (11 months ago)
- Last Synced: 2024-01-02T15:28:17.352Z (11 months ago)
- Topics: capsicum, exec, fork, hexdump, pledge, seccomp, setrlimit, stdio
- Language: C
- Homepage:
- Size: 94.7 KB
- Stars: 1
- Watchers: 2
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE
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README
# SYNOPSIS
hexlog [r]**in**|[r]**out**|[r]**inout**|**none** *cmd* *...*
# DESCRIPTION
hexlog: hexdump stdin and/or stdout to stderr
hexlog streams a hexdump (or optionally the raw bytes) of the standard
I/O of a subprocess to standard error. Hexdumps can be enabled or disabled
by sending a signal (see *SIGNALS*).
The hexdump code originates from:
https://gist.github.com/ccbrown/9722406
# EXAMPLES
```
$ echo abc | hexlog inout cat -n
1 abc
61 62 63 0A |abc.| (0)
20 20 20 20 20 31 09 61 62 63 0A | 1.abc.| (1)
$ (echo test | HEXLOG_FD_STDIN=4 HEXLOG_FD_STDOUT=5 hexlog inout cat) 4>stdin 5>stdout
$ echo abc | hexlog rinout cat -n
1 abc
abc
1 abc
```
# Build
```
make
# selecting process restrictions
RESTRICT_PROCESS=seccomp make
#### using musl
RESTRICT_PROCESS=rlimit ./musl-make
## linux seccomp sandbox: requires kernel headers
# clone the kernel headers somewhere
export MUSL_INCLUDE=/tmp
git clone https://github.com/sabotage-linux/kernel-headers.git $MUSL_INCLUDE/kernel-headers
# then compile
MUSL_INCLUDE=/tmp ./musl-make clean all
```
# OPTIONS
None.
# ARGUMENTS
none
: do not dump stdio
in
: dump stdin
out
: dump stdout
inout
: dump stdin/stdout
Prefacing a stream with 'r' will dump the raw bytes: rnone, rin,
rout, rinout.
# ENVIRONMENT VARIABLES
HEXLOG_LABEL_STDIN=" (0)"
: Label attached to hexdump of the stdin stream.
HEXLOG_LABEL_STDOUT=" (1)"
: Label attached to hexdump of the stdout stream.
HEXLOG_FD_STDIN="2"
: File descriptor to write dump of the stdin stream.
HEXLOG_FD_STDOUT="2"
: File descriptor to write dump of the stdout stream.
HEXLOG_TIMEOUT="0"
: Dump any buffered data after HEXLOG_TIMEOUT seconds of inactivity
(0 to disable)
# SIGNALS
SIGUSR1
: stdin: activate or deactivate hexdump based on the initial settings
SIGUSR2
: stdout: activate or deactivate hexdump based on the initial settings
SIGHUP
: reset hexdump stdio to initial value
SIGALRM
: dump any buffered data
# ALTERNATIVES
## bash
The general problem is duplicating stdout to stderr which can be handled
using `tee(1)` and bash's process substitution:
```
tee >(cat 1>&2) | command | tee >(cat 1>&2)
```
This pipeline forks 6 processes including bash. To hexdump:
```
tee >(stdbuf -oL hexdump -C 1>&2) | command | tee >(stdbuf -oL hexdump -C 1>&2)
```
A real version would use a format string and include the direction
(stdin vs stdout).
And to wrap it in a script:
```
#!/bin/bash
set -o errexit
set -o nounset
set -o pipefail
tee >(stdbuf -oL hexdump -C 1>&2) | $@ | tee >(stdbuf -oL hexdump -C 1>&2)
```
For example:
```
./hexlog nc -l -k 9090
```
Note: hexdump doesn't exit and flush the buffer when stdin is closed. It
will wait for the next full write.
## socat
```
socat -xv - EXEC:"command arg1",pty
```