dockerized-ffmpeg-drop-in.sh

#!/bin/bash
#
# dockerized-ffmpeg-drop-in
# version 0.3
# https://gist.github.com/ergosteur
# ** Partially AI-generated code via ChatGPT
#

#
# This is a shell script to use dockerized ffmpeg (linuxserver/ffmpeg) as a drop-in replacement for the 'ffmpeg' command
# Place the script somewhere in your PATH (e.g. ~/.local/bin) and rename it 'ffmpeg'
# Tested on Synology DSM 7.2.1 and Ubuntu 22.04/Docker CE 25.0.3
# Check https://github.com/linuxserver/docker-ffmpeg for usage information, ffmpeg version, and options for hardware acceleration.
#
# This script will pull the latest linuxserver/ffmpeg docker image upon first run if it is not found locally,
# however it will not automatically update the image, as per default docker behaviour.
#
# To update the image manually so it can be used by this script, run `docker pull linuxserver/ffmpeg`.
#

# ALLOWED_PATH_PREFIX variable:
# Set this to the base directory you want to allow for absolute paths.
# SECURITY WARNING: the path specified here will be mounted into the Docker container. The container will have full access to all files in the path.
#
# Note: On Synology, you must also allow Docker read/write access to the desired Shared Folders in the DSM Control Panel
#
ALLOWED_PATH_PREFIX="/volume1"

# Function to check if the path is valid
check_path() {
    # Check for absolute paths not starting with the allowed prefix
    if [ "${1#$ALLOWED_PATH_PREFIX}" = "$1" ] && [ "${1#/}" != "$1" ]; then
        echo "Invalid path: $1. Absolute paths must start with $ALLOWED_PATH_PREFIX."
        exit 1
    fi
    # Check for relative paths starting with ..
    if [ "${1#..}" != "$1" ]; then
        echo "Invalid path: $1. Relative paths must not start with '..'."
        exit 1
    fi
}

# Loop through all arguments to check for invalid paths
for arg in "$@"; do
    if [ "$arg" = "-i" ]; then
        next_is_file=true
    elif [ "$next_is_file" = true ]; then
        check_path "$arg"
        next_is_file=false
    else
        check_path "$arg"
    fi
done

# Determine whether to mount the current working directory or the allowed absolute path
if [ "${1#/}" = "$1" ]; then
    MOUNT_PATH="$(pwd)"
else
    MOUNT_PATH=$ALLOWED_PATH_PREFIX
fi

# Print Mount path used
echo "Mounting $MOUNT_PATH in Docker container..."
# Execute the Dockerized ffmpeg command
docker run --rm -e LANG=C.UTF-8 -v "$MOUNT_PATH:$MOUNT_PATH" -w "$MOUNT_PATH" linuxserver/ffmpeg "$@"