Encrypt file using OpenPGP

gpg-encrypt.go

package main

import (
	"flag"
	"io"
	"log"
	"os"

	"github.com/artyom/autoflags"

	"golang.org/x/crypto/openpgp"
	"golang.org/x/crypto/openpgp/armor"
	"golang.org/x/crypto/openpgp/packet"
)

func main() {
	params := struct {
		Ours   string `flag:"ours,our pgp ascii-armored key"`
		Theirs string `flag:"theirs,theirs pgp ascii-armored public key"`
		File   string `flag:"f,file to encrypt"`
		SaveTo string `flag:"w,file to write encrypted content to"`
	}{}
	autoflags.Define(&params)
	flag.Parse()
	if params.Ours == "" || params.Theirs == "" || params.File == "" || params.SaveTo == "" {
		flag.Usage()
		os.Exit(1)
	}
	if err := run(params.Ours, params.Theirs, params.File, params.SaveTo); err != nil {
		log.Fatal(err)
	}
}

func run(ours, theirs, file, saveto string) error {
	f, err := os.Open(file)
	if err != nil {
		return err
	}
	defer f.Close()
	signer, err := readEntity(ours)
	if err != nil {
		return err
	}
	recipient, err := readEntity(theirs)
	if err != nil {
		return err
	}
	dst, err := os.Create(saveto)
	if err != nil {
		return err
	}
	defer dst.Close()
	return encrypt([]*openpgp.Entity{recipient}, signer, f, dst)
}

func encrypt(recip []*openpgp.Entity, signer *openpgp.Entity, r io.Reader, w io.Writer) error {
	wc, err := openpgp.Encrypt(w, recip, signer, &openpgp.FileHints{IsBinary: true}, nil)
	if err != nil {
		return err
	}
	if _, err := io.Copy(wc, r); err != nil {
		return err
	}
	return wc.Close()
}

func readEntity(name string) (*openpgp.Entity, error) {
	f, err := os.Open(name)
	if err != nil {
		return nil, err
	}
	defer f.Close()
	block, err := armor.Decode(f)
	if err != nil {
		return nil, err
	}
	return openpgp.ReadEntity(packet.NewReader(block.Body))
}