sharing.sh

#/bin/sh

{
    err() {
        echo "$@" >&2
        exit 1
    }
    USAGE="Usage: @todo"

    generate() {
        PRIVATE_KEY_FILE=$(mktemp /tmp/private.XXXXXX)
        PUBLIC_KEY_FILE=$(mktemp /tmp/public.XXXXXX)

        openssl genrsa -out "$PRIVATE_KEY_FILE" 4096
        openssl rsa -in "$PRIVATE_KEY_FILE" -outform PEM -pubout -out "$PUBLIC_KEY_FILE"
        PUBLIC_KEY=$(<"$PUBLIC_KEY_FILE" base64 -w 0)

        echo "$0 encrypt $PRIVATE_KEY_FILE $PUBLIC_KEY"
    }

    encrypt() {
        PRIVATE_KEY_FILE="$1"
        PUBLIC_KEY="$2"
        if [ -z "$PRIVATE_KEY_FILE" ] || [ -z "$PUBLIC_KEY" ]
        then
            err "$USAGE"
        fi

        PUBLIC_KEY_FILE=$(mktemp /tmp/public.XXXXXX)
        ENCRYPTED_FILE=$(mktemp /tmp/enc.XXXXXX)

        <<<"$PUBLIC_KEY" base64 --decode > "$PUBLIC_KEY_FILE"
        echo -n "Input secret: "
        read -r SECRET
        <<<"$SECRET" openssl rsautl -encrypt -inkey $PUBLIC_KEY_FILE -pubin -in /dev/stdin -out "$ENCRYPTED_FILE"
        ENCRYPTED_SECRET=$(<"$ENCRYPTED_FILE" base64 -w 0)

        echo "$0 decrypt $PRIVATE_KEY_FILE $ENCRYPTED_SECRET"
    }

    decrypt() {
        PRIVATE_KEY_FILE="$1"
        ENCRYPTED_SECRET="$2"
        if [ -z "$PRIVATE_KEY_FILE" ] || [ -z "$ENCRYPTED_SECRET" ]
        then
            err "$USAGE"
        fi

        <<<"$ENCRYPTED_SECRET" base64 --decode | openssl rsautl -decrypt -in /dev/stdin -out /dev/stdout -inkey "$PRIVATE_KEY_FILE"
    }

    CMD="$1"
    shift
    if [ "$CMD" == "generate" ]
    then
        generate "$@"
    elif [ "$CMD" == "encrypt" ]
    then
        encrypt "$@"
    elif [ "$CMD" == "decrypt" ]
    then
        decrypt "$@"
    else
        err "$USAGE"
    fi
}