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Software Development Security

Why you should use STDIN to read your program arguments

Improve application security by reading sensitive program arguments from STDIN

STDIN is more secure than environment variables or command-line arguments

When you pass command-line arguments to a program, they are visible to anyone who can run the ps command. Allowing others to read arguments is a security risk if the arguments contain sensitive information like passwords or API keys.

Environment variables are also visible to anyone who can run the ps command. They are also globally visible to the program, so any arbitrary code in your application can extract the environment variables.

To get the environment variables of a process, run ps eww <PID>. For example:

$ ps eww 1710
    PID TTY      STAT   TIME COMMAND
   1710 pts/0    Ss+    0:00 bash SYSTEMD_EXEC_PID=1209 SSH_AUTH_SOCK=/run/user/1000/keyring/ssh SESSION_MANAGER=local/victor-ubuntu:@/tmp/.ICE-unix/1176,unix/victor-ubuntu:/tmp/.ICE-unix/1176 GNOME_TERMINAL_SCREEN=/org/gnome/Terminal/screen/ab0b9d6a_a699_4bc5_bb53_628be016afa5 LANG=en_US.UTF-8 XDG_CURRENT_DESKTOP=ubuntu:GNOME PWD=/home/victor WAYLAND_DISPLAY=wayland-0 DISPLAY=:0 QT_IM_MODULE=ibus USER=victor DESKTOP_SESSION=ubuntu XDG_MENU_PREFIX=gnome- HOME=/home/victor DBUS_SESSION_BUS_ADDRESS=unix:path=/run/user/1000/bus SSH_AGENT_LAUNCHER=gnome-keyring _=/usr/bin/gnome-session XDG_CONFIG_DIRS=/etc/xdg/xdg-ubuntu:/etc/xdg VTE_VERSION=6800 XDG_SESSION_DESKTOP=ubuntu QT_ACCESSIBILITY=1 GNOME_DESKTOP_SESSION_ID=this-is-deprecated GNOME_SETUP_DISPLAY=:1 GTK_MODULES=gail:atk-bridge LOGNAME=victor GNOME_TERMINAL_SERVICE=:1.83 GNOME_SHELL_SESSION_MODE=ubuntu XDG_RUNTIME_DIR=/run/user/1000 XMODIFIERS=@im=ibus SHELL=/bin/bash XDG_SESSION_TYPE=wayland PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/snap/bin:/snap/bin USERNAME=victor COLORTERM=truecolor XAUTHORITY=/run/user/1000/.mutter-Xwaylandauth.R816R2 XDG_DATA_DIRS=/usr/share/ubuntu:/usr/local/share/:/usr/share/:/var/lib/snapd/desktop IM_CONFIG_PHASE=1 TERM=xterm-256color GDMSESSION=ubuntu XDG_SESSION_CLASS=user

STDIN is more secure because it is not visible to the ps command and is not globally visible to the program. Thus, only the parts of the program that explicitly read from STDIN can access this data.

How to read program arguments from STDIN with Go

In the code example below, we check if any data is being piped in from STDIN with os.ModeNamedPipe. Then, we wait to read all the data from STDIN with ioutil.ReadAll. Finally, we parse the STDIN data just like a shell would using the github.com/kballard/go-shellquote library and append it to any existing command-line arguments.

How to integrate with a secret manager

One way to securely pass sensitive information to a program is to store it in a secret manager like 1Password. Then, you can read the secret from the secret manager and pass it to the program via STDIN. For example:

echo --secret $(op read op://employee/example_server/secret) | go run read-args-from-stdin.go

Further reading

Recently, we discussed how to unmarshal JSON payloads with null, set, and missing keys using Go.

Previously, we wrote how we catch missed authorization checks in our Go application.

Watch how to read program arguments from STDIN

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