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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 verifyCommand struct {
	embedded bool
	quiet    bool
	zip      bool
	pubFile  string
	keyFile  string
	sigFile  string
	msgFile  string
}

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

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

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

	switch {
	case v.zip && v.embedded:
		return subcommands.ExitUsageError
	case v.zip:
		if err := verifyGzip(v.pubFile, v.sigFile); err != nil {
			log.Println(err)
			return subcommands.ExitFailure
		}
	case v.embedded:
		if err := verifyEmbedded(v.pubFile, v.sigFile); err != nil {
			log.Println(err)
			return subcommands.ExitFailure
		}
	default:
		if err := verifyPlain(v.pubFile, v.sigFile, v.msgFile); err != nil {
			log.Println(err)
			return subcommands.ExitFailure
		}
	}
	if !v.quiet {
		fmt.Println("Signature Verified")
	}
	return subcommands.ExitSuccess
}

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

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

// TODO ugly work-in-progress
func verifyGzip(pubFile, sigFile string) error {
	fd, err := Open(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(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
}