decrypt_pgp.go

// usage: go run decrypt_pgp.go --keyfile private.key.asc file1.gz.pgp file.gz.pgp ...

package main

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

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

func main() {
	keyfilename := flag.String("keyfile", "", "file containing ascii-armored private key")
	flag.Parse()

	if *keyfilename == "" {
		log.Fatal("--keyfile is required")
	}

	keyfile, err := os.Open(*keyfilename)
	if err != nil {
		log.Fatal(err)
	}

	entities, err := openpgp.ReadArmoredKeyRing(keyfile)
	if err != nil {
		log.Fatal(err)
	}
	keyfile.Close()

	for _, infile := range flag.Args() {
		outfile := strings.TrimSuffix(infile, ".pgp")
		if outfile == infile {
			log.Printf("%s isn't a .pgp file", infile)
			continue
		}

		in, err := os.Open(infile)
		if err != nil {
			log.Printf("couldn't read %s: %s", infile, err)
			continue
		}

		message, err := openpgp.ReadMessage(in, entities, nil, nil)
		if err != nil {
			log.Printf("couldn't decrypt %s: %s", infile, err)
			continue
		}

		out, err := os.Create(outfile)
		if err != nil {
			log.Printf("couldn't create %s: %s", outfile, err)
			continue
		}

		if _, err = io.Copy(out, message.UnverifiedBody); err != nil {
			log.Printf("couldn't decrypt to %s: %s", outfile, err)
		}
		if err = out.Close(); err != nil {
			log.Printf("couldn't decrypt to %s: %s", outfile, err)
		}
		in.Close()
	}
}