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path: root/verify.go
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package main

import (
	"flag"
	"fmt"
	"io/ioutil"
	"os"

	"dim13.org/signify/file"
	"dim13.org/signify/key"
)

// Usage: signify -V [-eqz] [-p pubkey] [-t keytype] [-x sigfile] -m message

func Verify() error {
	args := flag.NewFlagSet("verify", flag.ExitOnError)
	var (
		embedded = args.Bool("e", false, "Embed message")
		quiet    = args.Bool("q", false, "Quiet mode")
		zip      = args.Bool("z", false, "Verify gzip archive")
		pubFile  = args.String("p", "", "Public key file")
		keyType  = args.String("t", "", "Key type") // TODO
		sigFile  = args.String("x", "", "Signature file")
		msgFile  = args.String("m", "", "Message file (required)")
	)
	args.Parse(os.Args[2:])
	if *embedded && *zip {
		return ErrEZ
	}
	if *msgFile == "" {
		args.Usage()
		return nil
	}
	_, _, _ = embedded, keyType, sigFile

	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
	}
	if !*quiet {
		fmt.Println("Signature Verfied")
	}
	return nil
}

func OpenPub(fname string) (*key.Pub, error) {
	block, err := file.DecodeFile(fname)
	if err != nil {
		return nil, err
	}
	pubKey := new(key.Pub)
	if err := key.Unmarshal(block.Bytes, pubKey); err != nil {
		return nil, err
	}
	if err := pubKey.Check(); err != nil {
		return nil, err
	}
	return pubKey, nil
}

func OpenSig(fname string) (*key.Sig, []byte, error) {
	block, err := file.DecodeFile(fname + ".sig")
	if err != nil {
		return nil, nil, err
	}
	sig := new(key.Sig)
	if err := key.Unmarshal(block.Bytes, sig); err != nil {
		return nil, nil, err
	}
	if err := sig.Check(); err != nil {
		return nil, nil, err
	}
	if len(block.Message) > 0 {
		return sig, block.Message, nil
	}
	msg, err := ioutil.ReadFile(fname)
	if err != nil {
		return nil, nil, err
	}
	return sig, msg, nil
}