otsclear

#!/usr/bin/env bash
# requires: opentimestamps-client(ots), base64, sed, awk, coreutils(truncate,cat)

set -e

usage () {
    printf "usage: %s [OPTION] <file>\n" "$(basename $0)"
    printf "\nOPTIONS\n\n"
    printf "     --verify,-v   verify a cleartext ots timestamp\n"
    printf "     --encode,-e   encode an ots file as a cleartext ots timestamp\n\n"
    exit 1
}

if [ -z $1 ]; then
    usage
fi

ots_cleartext_msg () {
    awk '/^-----BEGIN OPENTIMESTAMPS MESSAGE-----/,/^$/{f=1;next};/^-----BEGIN OPENTIMESTAMPS PROOF-----/{f=0}f' \
        | sed 's,^- ,,'
}

ots_cleartext_verify() {
    txt="$(mktemp)".txt
    otsfile="$txt".ots
    orig="$txt".orig
    cat > "$orig"
    <"$orig" ots_cleartext_msg | tee "$txt"

    # chop off any line endings that were added by the previous commands
    truncate -s -1 "$txt"

    <"$orig" awk '/^-----BEGIN OPENTIMESTAMPS PROOF-----/,/^$/{f=1;next};/^-----END OPENTIMESTAMPS PROOF-----/{f=0}f' \
        | base64 -d > "$otsfile"
    ots verify "$otsfile"
    rm -f "$txt" "$otsfile" "$orig"
}

ots_cleartext_encode() {
    printf -- '-----BEGIN OPENTIMESTAMPS MESSAGE-----\n\n'
    sed 's,^-,- -,' "$1"
    printf -- '\n-----BEGIN OPENTIMESTAMPS PROOF-----\n\n'
    base64 "$1.ots"
    printf -- '-----END OPENTIMESTAMPS PROOF-----\n'
}

if [[ $1 == "-v" ]] || [[ $1 == "--verify" ]]; then
    if [ -n "$2" ]; then
        <$2 ots_cleartext_verify
    else
        ots_cleartext_verify
    fi

elif [[ $1 == "-e" ]] || [[ $1 == "--encode" ]]; then
    if [ ! -n "$2" ]; then
        printf "error: source filename required for otsclear --encode\n" >&2
        exit 2
    fi

    filename=$(basename -- "$2")
    extension="${filename##*.}"
    filename="${2%.*}"

    if [ "$extension" != "ots" ]; then
        printf "error: encode expected ots file, got '%s'\n" "$extension" >&2
        exit 3
    fi

    for file in $filename ${filename}.ots
    do
        if [ ! -e "$file" ]; then
            printf "error: could not find %s\n" "$file" >&2
            exit 3
        fi
    done

    ots_cleartext_encode "$filename"
else
    usage
fi