oa8signverify/oa8verify

#!/usr/bin/env sh
# vim: filetype=sh:tabstop=4:tw=80

set -e > /dev/null 2>&1
set -u > /dev/null 2>&1

me=oa8verify
vers=1.1.1

osl=openssl
a85=ascii85

# shellcheck disable=SC2097,SC2098
if ! PATH="$(command -p env -i \
	getconf PATH)" \
		command -p env -i TMPDIR="${TMPDIR:-}" PATH="${PATH:-}" \
			rm -f \
				"$(command -p env -i TMPDIR="${TMPDIR:-}" mktemp)"; then
					printf '%s\n' \
						"Error: Misbehaving shell or environment; aborting" >&2
					exit 1
fi

cleanup() {
	command -p env -i \
		rm -f \
			"${tmpfile:-}" ||
				true
}

filename=${1:-}
signature=${2:-}
publickey=${3:-}

exitstatus=""
if ! command -p env \
		"${osl:?}" version > /dev/null 2>&1; then
		printf '%s\n' \
			"Error: ${osl:?} could not be executed" >&2
		exit 1
fi

exitstatus=""
if ! command -p env \
		"${a85:?}" -h > /dev/null 2>&1; then
			exitstatus="${?:?Error: exitstatus undefined}"
			if [ "${exitstatus:-}" -eq 126 ]; then
				printf '%s\n' \
					"Error: ${a85:?} could not be executed" >&2
				exit 1
			elif [ "${exitstatus:-}" -eq 127 ]; then
				printf '%s\n' \
					"Error: ${a85:?} could not be found" >&2
				printf '\t%s\n' \
					'Suggestion: "gem install Ascii85"' >&2
				exit 1
			else
				printf '%s\n' \
					"Error: ${a85:?} failure ${exitstatus:-}" >&2
				exit 1
			fi
fi

if [ ${#} -lt 3 ]; then
	printf '%s\n' \
		"*** ${me:?Error: me undefined} (v${vers:?Error: vers undefined})"
	printf '\t%s\n' \
		"Usage: ${me:?} <file> <signature.oa8> <public.oa8>"
	exit 1
fi

tmpfile=""
tmpfile="$(command -p env -i TMPDIR="${TMPDIR:-}" \
	mktemp)" ||
		{
			printf '%s\n' \
				"Error: mktemp failure" >&2
			exit 1
		}

exitstatus=""
command -p env \
	"${a85:?}" -d \
		< "${signature:?Error: signature undefined}" \
			> "${tmpfile:?Error: tmpfile undefined}" ||
				{
					exitstatus="${?:?Error: exitstatus undefined}"
					if [ "${exitstatus:-}" -eq 126 ]; then
						printf '%s\n' \
							"Error: ${a85:?} could not be executed" >&2
						cleanup
						exit 1
					elif [ "${exitstatus:-}" -eq 127 ]; then
						printf '%s\n' \
							"Error: ${a85:?} could not be found" >&2
						printf '\t%s\n' \
							'Suggestion: "gem install Ascii85"' >&2
						cleanup
						exit 1
					else
						printf '%s\n' \
							"Error: signature parsing failure ${exitstatus:-}" \
								>&2
						cleanup
						exit 3
					fi
				}

exitstatus=""
command -p env \
	"${osl:?}" dgst -sha3-512 \
		-verify "${publickey:?Error: publickey undefined}" \
			-signature "${tmpfile:?Error: tmpfile undefined}" \
				"${filename:?Error filename undefined}" ||
					{
						exitstatus="${?:?Error: exitstatus undefined}"
						if [ "${exitstatus:-}" -eq 126 ]; then
							printf '%s\n' \
								"Error: ${osl:?} could not be executed" >&2
							cleanup
							exit 1
						elif [ "${exitstatus:-}" -eq 127 ]; then
							printf '%s\n' \
								"Error: ${osl:?} could not be found" >&2
							cleanup
							exit 1
						else
							printf '%s\n' \
								"Error: ${me:?} failure ${exitstatus:-}" \
									>&2
							cleanup
							exit 2
						fi
					}

cleanup

# Local Variables:
# mode: sh
# sh-shell: sh
# sh-indentation: 4
# sh-basic-offset: 4
# tab-width: 4
# End: