git-sig/siglog

#! /usr/bin/env bash
set -e

die() {
	echo "$@" >&2
	exit 1
}

gpg_env(){
	GNUPGHOME=$(mktemp -d -p /dev/shm/); export GNUPGHOME
	killall gpg-agent 2> /dev/null
	gpg-agent --daemon --extra-socket "$GNUPGHOME/S.gpg-agent" 2> /dev/null
	echo "export PATH=$GNUPGHOME:$PATH \
		  export GNUPGHOME=$GNUPGHOME; \
		  export GPG_AGENT_INFO=$GNUPGHOME/S.gpg-agent"
}

gpg_cleanup(){
	gpgconf --kill gpg-agent
	rm -rf "$GNUPGHOME"
}

verify_file() {
	filename="${1?}"
	sig_count=0
	seen_fingerprints=""
	for sig_filename in "${filename%.*}".*.asc; do
		gpg --verify "${sig_filename}" "${filename}" >/dev/null 2>&1 || {
			echo "Invalid signature: ${sig_filename}";
			exit 1;
		}
		fingerprint=$( \
			gpg --list-packets "${sig_filename}" \
			| grep keyid \
			| sed 's/.*keyid //g'
		)
		signer=$( \
			gpg \
				--list-keys \
				--with-colons "${fingerprint}" 2>&1 \
			| awk -F: '$1 == "uid" {print $10}' \
			| head -n1 \
		)
		[[ "${seen_fingerprints}" == *"${fingerprint}"* ]] && {
			echo "Duplicate signature: ${sig_filename}";
			exit 1;
		}
		echo "Verified signature by \"${signer}\""
		seen_fingerprints="${seen_fingerprints} ${fingerprint}"
		((sig_count=sig_count+1))
	done
	[[ "$sig_count" -ge "$threshold" ]] || {
		echo "Minimum number of signatures not met: ${sig_count}/${threshold}";
		exit 1;
	}
}

cmd_manifest() {
	mkdir -p .siglog
	find . \
	    -type f \
		-not -path "./.git/*" \
		-not -path "./.siglog/*" \
	    -exec openssl sha256 -r {} \; \
	| sed 's/ \*/ /g' \
	| LC_ALL=C sort -k2 \
	> .siglog/manifest.txt
}

cmd_detach-verify() {
	[ $# -lt 3 ] || die \
		"Usage: detach-verify <threshold> <pubkey_dir> <file> (, <file, ...)"

	threshold="${1}"
	pubkey_dir="${2}"
	target_files="${*:3}"

	eval "$(gpg_env)"
	gpg --import "${pubkey_dir}"/*.asc 2>/dev/null
	for target_file in ${target_files}; do
		verify_file "${target_file}"
	done

	gpg_cleanup
}

cmd_verify() {
	cmd_manifest
	for file in .siglog/*.asc; do
	  gpg --verify "$file" signatures/manifest.txt
	done
}

cmd_version() {
	cat <<-_EOF
	============================================
	=  siglog: simple multisig trust toolchain =
	=                                          =
	=                  v0.0.1                  =
	=                                          =
	=     https://gitlab.com/pchq/siglog       =
	============================================
	_EOF
}

cmd_usage() {
	cmd_version
	echo
	cat <<-_EOF
	Usage:
	    $PROGRAM detach-verify [<threshold> <pubkey_dir> <file> (, <file, ...)
	        Verify detached signatures of the provided file by m-of-n keys
	    $PROGRAM verify
	        Verify all signing policies for this directory are met
	    $PROGRAM manifest
	        Generate hash manifest for this directory
	    $PROGRAM sign
	        Add signature to manifest for this directory
	    $PROGRAM help
	        Show this text.
	    $PROGRAM version
	        Show version information.
	_EOF
}

checktools(){
	for cmd in "$@"; do
		if ! command -v "$1" >/dev/null; then
			printf "not found!\n";
			return 1;
		fi
	done
}

PROGRAM="${0##*/}"
COMMAND="$1"

checktools gpg openssl

case "$1" in
	detach-verify) shift;       cmd_detach-verify "$@" ;;
	verify) shift;              cmd_verify "$@" ;;
	manifest) shift;            cmd_manifest "$@" ;;
	sign) shift;                cmd_sign "$@" ;;
	version|--version) shift;   cmd_version "$@" ;;
	help|--help) shift;         cmd_usage "$@" ;;
	*)                          cmd_usage "$@" ;;
esac
exit 0