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package main

import (
	"errors"
	"flag"
	"fmt"
	"io/ioutil"
	"log"
	"path/filepath"

	"dim13.org/signify/ask"
	"dim13.org/signify/signify"
)

/*
	signify -C [-q] -p pubkey -x sigfile [file ...]
	signify -G [-n] [-c comment] -p pubkey -s seckey
	signify -S [-ez] [-x sigfile] -s seckey -m message
	signify -V [-eqz] [-p pubkey] [-t keytype] [-x sigfile] -m message
*/

const safePath = "/etc/signify"

var (
	checksum = flag.Bool("C", false, "Verify a signed checksum list")
	generate = flag.Bool("G", false, "Generate a new key pair")
	sign     = flag.Bool("S", false, "Sign the specfied message")
	verify   = flag.Bool("V", false, "Verify the message")
	comment  = flag.String("c", "signify", "Comment")
	embed    = flag.Bool("e", false, "Embed the message")
	msg      = flag.String("m", "", "Message file")
	nopass   = flag.Bool("n", false, "No key passphrase")
	pub      = flag.String("p", "", "Public key file")
	quiet    = flag.Bool("q", false, "Quiet mode")
	sec      = flag.String("s", "", "Secret key file")
	sig      = flag.String("x", "", "Signature file")
	gzip     = flag.Bool("z", false, "Sign and verify gzip archives")
)

var (
	ErrNamingScheme = errors.New("please use naming scheme of keyname.pub and keyname.sec")
)

func main() {
	flag.Parse()

	switch {
	case *generate:
		if err := Generate(*pub, *sec, *comment, *nopass); err != nil {
			log.Fatal(err)
		}
	case *sign:
		if err := Sign(*msg, *sec, *embed); err != nil {
			log.Fatal(err)
		}
	case *verify:
		if err := Verify(*msg, *pub); err != nil {
			log.Fatal(err)
		}
	default:
		flag.Usage()
	}
}

func Generate(pubFile, secFile, comment string, nopass bool) error {
	if !NamingScheme(pubFile, secFile) {
		return ErrNamingScheme
	}

	pubKey, encKey, err := signify.NewKey()
	if err != nil {
		return err
	}

	if nopass {
		encKey.KDFRounds = 0
	}
	encKey.Kdf(ask.Confirmed)

	encRaw, err := signify.Marshal(encKey)
	if err != nil {
		return err
	}

	sfile := signify.File{
		Comment: fmt.Sprintf("%s secret key", comment),
		RawKey:  encRaw,
	}
	if err := sfile.WriteFile(secFile, signify.SecMode); err != nil {
		return err
	}

	pubRaw, err := signify.Marshal(pubKey)
	if err != nil {
		return err
	}
	pfile := signify.File{
		Comment: fmt.Sprintf("%s public key", comment),
		RawKey:  pubRaw,
	}
	if err := pfile.WriteFile(pubFile, signify.PubMode); err != nil {
		return err
	}

	return nil
}

func OpenEnc(fname string) (*signify.EncKey, error) {
	f, err := signify.ParseFile(fname)
	if err != nil {
		return nil, err
	}
	encKey := new(signify.EncKey)
	if err := signify.Unmarshal(f.RawKey, encKey); err != nil {
		return nil, err
	}
	encKey.Kdf(ask.Password)
	if err := encKey.Check(); err != nil {
		return nil, err
	}
	return encKey, nil
}

func OpenPub(fname string) (*signify.PubKey, error) {
	f, err := signify.ParseFile(fname)
	if err != nil {
		return nil, err
	}
	pubKey := new(signify.PubKey)
	if err := signify.Unmarshal(f.RawKey, pubKey); err != nil {
		return nil, err
	}
	if err := pubKey.Check(); err != nil {
		return nil, err
	}
	return pubKey, nil
}

func OpenSig(fname string) (*signify.Sig, []byte, error) {
	f, err := signify.ParseFile(fname + ".sig")
	if err != nil {
		return nil, nil, err
	}
	sig := new(signify.Sig)
	if err := signify.Unmarshal(f.RawKey, sig); err != nil {
		return nil, nil, err
	}
	if err := sig.Check(); err != nil {
		return nil, nil, err
	}
	if f.Embedded() {
		return sig, f.Message, nil
	}
	msg, err := ioutil.ReadFile(fname)
	if err != nil {
		return nil, nil, err
	}
	return sig, msg, nil
}

func Sign(msgFile, secFile string, embed bool) error {
	encKey, err := OpenEnc(secFile)
	if err != nil {
		return err
	}
	body, err := ioutil.ReadFile(msgFile)
	if err != nil {
		return err
	}
	sig := encKey.Sign(body)
	sigRaw, err := signify.Marshal(sig)
	if err != nil {
		return err
	}
	sigfile := signify.File{
		Comment: fmt.Sprintf("verify with %s", ToPub(secFile)), // TODO replace .sec with .pub
		RawKey:  sigRaw,
	}
	if embed {
		sigfile.Message = body
	}
	if err := sigfile.WriteFile(msgFile+".sig", signify.PubMode); err != nil {
		return err
	}
	return nil
}

func Verify(msgFile, pubFile string) error {
	pubKey, err := OpenPub(pubFile)
	if err != nil {
		return err
	}
	sig, body, err := OpenSig(msgFile)
	if err != nil {
		return err
	}
	if err := pubKey.Verify(body, sig); err != nil {
		return err
	}
	log.Println("Signature Verfied")
	return nil
}

func NamingScheme(pubFile, secFile string) bool {
	pubFile = filepath.Base(pubFile)
	secFile = filepath.Base(secFile)
	pubExt := filepath.Ext(pubFile)
	secExt := filepath.Ext(secFile)
	return pubExt == ".pub" && secExt == ".sec" && pubFile[:len(pubExt)-1] == secFile[:len(secExt)-1]
}

func ToPub(secFile string) string {
	ext := filepath.Ext(secFile)
	return filepath.Base(secFile[:len(ext)-1] + ".pub")
}