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path: root/cmd_verify.go
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package main

import (
	"context"
	"flag"
	"fmt"
	"io/ioutil"
	"log"
	"strings"

	"dim13.org/signify/b64file"
	"dim13.org/signify/key"
	"dim13.org/signify/zsig"
	"github.com/google/subcommands"
)

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

type verifyCmd struct {
	embed   bool
	quiet   bool
	zip     bool
	pubFile string
	keyFile string
	sigFile string
	msgFile string
}

func (m *verifyCmd) Name() string     { return "verify" }
func (m *verifyCmd) Synopsis() string { return "verify signature" }
func (m *verifyCmd) Usage() string {
	return "verify [-eqz] [-p pubkey] [-t keytype] [-x sigfile] -m message\n"
}

func (m *verifyCmd) SetFlags(f *flag.FlagSet) {
	f.BoolVar(&m.embed, "e", false, "embed message")
	f.BoolVar(&m.quiet, "q", false, "quiet mode")
	f.BoolVar(&m.zip, "z", false, "verify gzip archive") // TODO
	f.StringVar(&m.pubFile, "p", "", "public key file")
	f.StringVar(&m.keyFile, "t", "", "key type") // TODO
	f.StringVar(&m.sigFile, "x", "", "signature file")
	f.StringVar(&m.msgFile, "m", "", "message file (required)")
}

func (m *verifyCmd) Execute(ctx context.Context, f *flag.FlagSet, args ...interface{}) subcommands.ExitStatus {
	if m.msgFile == "" {
		f.Usage()
		return subcommands.ExitUsageError
	}
	if m.sigFile == "" {
		m.sigFile = SigName(m.msgFile)
	}
	// TODO keyType

	var err error
	switch {
	case m.zip && m.embed:
		f.Usage()
		return subcommands.ExitUsageError
	case m.zip:
		err = m.zipped()
	case m.embed:
		err = m.embedded()
	default:
		err = m.plain()
	}
	if err != nil {
		log.Println(err)
		return subcommands.ExitFailure
	}
	if !m.quiet {
		fmt.Println("Signature Verified")
	}
	return subcommands.ExitSuccess
}

func (m *verifyCmd) plain() error {
	msg, err := ioutil.ReadFile(m.msgFile)
	if err != nil {
		return err
	}
	sig, _, verifyWith, err := openSig(m.sigFile)
	if err != nil {
		return err
	}
	if m.pubFile == "" {
		m.pubFile = verifyWith
	}
	pub, err := openPub(m.pubFile)
	if err != nil {
		return err
	}
	return sig.Verify(msg, pub)
}

func (m *verifyCmd) embedded() error {
	sig, msg, verifyWith, err := openSig(m.sigFile)
	if err != nil {
		return err
	}
	if m.pubFile == "" {
		m.pubFile = verifyWith
	}
	pub, err := openPub(m.pubFile)
	if err != nil {
		return err
	}
	return sig.Verify(msg, pub)
}

// TODO ugly work-in-progress
func (m *verifyCmd) zipped() error {
	fd, err := Open(m.sigFile)
	if err != nil {
		return err
	}
	defer fd.Close()
	z, err := zsig.NewReader(fd)
	if err != nil {
		return err
	}

	sig := new(key.Sig)
	_, msg, err := b64file.Decode(strings.NewReader(z.Comment), sig)
	if err != nil {
		return err
	}
	if err := sig.Validate(); err != nil {
		return err
	}

	pub, err := openPub(m.pubFile)
	if err != nil {
		return err
	}
	if err := sig.Verify(msg, pub); err != nil {
		return err
	}

	zhead, err := zsig.ParseBytes(msg)
	if err != nil {
		return err
	}

	return zhead.Verify(z)
}

func openPub(fname string) (*key.Pub, error) {
	pub := new(key.Pub)
	fd, err := Open(fname)
	if err != nil {
		return nil, err
	}
	defer fd.Close()
	if _, _, err := b64file.Decode(fd, pub); err != nil {
		return nil, err
	}
	if err := pub.Validate(); err != nil {
		return nil, err
	}
	return pub, nil
}

func openSig(fname string) (*key.Sig, []byte, string, error) {
	sig := new(key.Sig)
	fd, err := Open(fname)
	if err != nil {
		return nil, nil, "", err
	}
	defer fd.Close()
	comment, msg, err := b64file.Decode(fd, sig)
	if err != nil {
		return nil, nil, "", err
	}
	if err := sig.Validate(); err != nil {
		return nil, nil, "", err
	}
	pubKey := CommentPubFile(comment)
	return sig, msg, pubKey, nil
}