forked from keybase/client
/
pgp_verify.go
271 lines (229 loc) · 6.55 KB
/
pgp_verify.go
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// Copyright 2015 Keybase, Inc. All rights reserved. Use of
// this source code is governed by the included BSD license.
package engine
import (
"bytes"
"errors"
"fmt"
"io"
"io/ioutil"
"github.com/keybase/client/go/libkb"
"github.com/keybase/client/go/protocol/keybase1"
"github.com/keybase/go-crypto/openpgp"
"github.com/keybase/go-crypto/openpgp/armor"
"github.com/keybase/go-crypto/openpgp/clearsign"
"github.com/keybase/go-crypto/openpgp/packet"
)
type PGPVerifyArg struct {
Source io.Reader
Signature []byte
SignedBy string
}
// PGPVerify is an engine.
type PGPVerify struct {
arg *PGPVerifyArg
source io.Reader
signStatus *libkb.SignatureStatus
signer *libkb.User
libkb.Contextified
}
// NewPGPVerify creates a PGPVerify engine.
func NewPGPVerify(arg *PGPVerifyArg, g *libkb.GlobalContext) *PGPVerify {
return &PGPVerify{
arg: arg,
Contextified: libkb.NewContextified(g),
}
}
// Name is the unique engine name.
func (e *PGPVerify) Name() string {
return "PGPVerify"
}
// GetPrereqs returns the engine prereqs.
func (e *PGPVerify) Prereqs() Prereqs {
return Prereqs{}
}
// RequiredUIs returns the required UIs.
func (e *PGPVerify) RequiredUIs() []libkb.UIKind {
return []libkb.UIKind{libkb.PgpUIKind}
}
// SubConsumers returns the other UI consumers for this engine.
func (e *PGPVerify) SubConsumers() []libkb.UIConsumer {
return []libkb.UIConsumer{
&PGPDecrypt{},
&ScanKeys{},
&ResolveThenIdentify2{},
}
}
// Run starts the engine.
func (e *PGPVerify) Run(ctx *Context) error {
var err error
defer e.G().Trace("PGPVerify::Run", func() error { return err })()
var sc libkb.StreamClassification
sc, e.source, err = libkb.ClassifyStream(e.arg.Source)
// For a Detached signature, we'll be expecting an UnknownStreamError
if err != nil {
if _, ok := err.(libkb.UnknownStreamError); !ok || len(e.arg.Signature) == 0 {
return err
}
}
if sc.Format == libkb.CryptoMessageFormatPGP && sc.Type == libkb.CryptoMessageTypeClearSignature {
err = e.runClearsign(ctx)
return err
}
if len(e.arg.Signature) == 0 {
err = e.runAttached(ctx)
return err
}
err = e.runDetached(ctx)
return err
}
func (e *PGPVerify) SignatureStatus() *libkb.SignatureStatus {
return e.signStatus
}
func (e *PGPVerify) Signer() *libkb.User {
return e.signer
}
// runAttached verifies an attached signature
func (e *PGPVerify) runAttached(ctx *Context) error {
arg := &PGPDecryptArg{
Source: e.source,
Sink: libkb.NopWriteCloser{W: ioutil.Discard},
AssertSigned: true,
SignedBy: e.arg.SignedBy,
}
eng := NewPGPDecrypt(arg, e.G())
if err := RunEngine(eng, ctx); err != nil {
return err
}
e.signStatus = eng.SignatureStatus()
e.signer = eng.Signer()
return nil
}
// runDetached verifies a detached signature
func (e *PGPVerify) runDetached(ctx *Context) error {
sk, err := NewScanKeys(ctx.SecretUI, e.G())
if err != nil {
return err
}
checkfn := openpgp.CheckDetachedSignature
if libkb.IsArmored(e.arg.Signature) {
checkfn = openpgp.CheckArmoredDetachedSignature
}
signer, err := checkfn(sk, e.source, bytes.NewReader(e.arg.Signature))
if err != nil {
return err
}
e.signer = sk.KeyOwnerByEntity(signer)
e.signStatus = &libkb.SignatureStatus{IsSigned: true}
if signer != nil {
if len(signer.UnverifiedRevocations) > 0 {
return libkb.BadSigError{
E: fmt.Sprintf("Key %x belonging to %q has been revoked by its designated revoker.", signer.PrimaryKey.KeyId, e.signer.GetName()),
}
}
e.signStatus.Verified = true
e.signStatus.Entity = signer
if err := e.checkSignedBy(ctx); err != nil {
return err
}
var r io.Reader = bytes.NewReader(e.arg.Signature)
if libkb.IsArmored(e.arg.Signature) {
block, err := armor.Decode(r)
if err != nil {
return err
}
r = block.Body
}
p, err := packet.Read(r)
if err != nil {
return err
}
if val, ok := p.(*packet.Signature); ok {
e.signStatus.SignatureTime = val.CreationTime
}
fingerprint := libkb.PGPFingerprint(signer.PrimaryKey.Fingerprint)
OutputSignatureSuccess(ctx, fingerprint, e.signer, e.signStatus.SignatureTime)
}
return nil
}
// runClearsign verifies a clearsign signature
func (e *PGPVerify) runClearsign(ctx *Context) error {
// clearsign decode only works with the whole data slice, not a reader
// so have to read it all here:
msg, err := ioutil.ReadAll(e.source)
if err != nil {
return err
}
b, _ := clearsign.Decode(msg)
if b == nil {
return errors.New("Unable to decode clearsigned message")
}
sigBody, err := ioutil.ReadAll(b.ArmoredSignature.Body)
if err != nil {
return err
}
sk, err := NewScanKeys(ctx.SecretUI, e.G())
if err != nil {
return err
}
signer, err := openpgp.CheckDetachedSignature(sk, bytes.NewReader(b.Bytes), bytes.NewReader(sigBody))
if err != nil {
return fmt.Errorf("Check sig error: %s", err)
}
e.signer = sk.KeyOwnerByEntity(signer)
e.signStatus = &libkb.SignatureStatus{IsSigned: true}
if signer != nil {
if len(signer.UnverifiedRevocations) > 0 {
return libkb.BadSigError{
E: fmt.Sprintf("Key %x belonging to %q has been revoked by its designated revoker.", signer.PrimaryKey.KeyId, e.signer.GetName()),
}
}
e.signStatus.Verified = true
e.signStatus.Entity = signer
if err := e.checkSignedBy(ctx); err != nil {
return err
}
p, err := packet.Read(bytes.NewReader(sigBody))
if err != nil {
return err
}
if val, ok := p.(*packet.Signature); ok {
e.signStatus.SignatureTime = val.CreationTime
}
fingerprint := libkb.PGPFingerprint(signer.PrimaryKey.Fingerprint)
OutputSignatureSuccess(ctx, fingerprint, e.signer, e.signStatus.SignatureTime)
}
return nil
}
func (e *PGPVerify) checkSignedBy(ctx *Context) error {
if len(e.arg.SignedBy) == 0 {
// no assertion necessary
return nil
}
if !e.signStatus.Verified || e.signStatus.Entity == nil || e.signer == nil {
// signature not valid, so no need to assert
return nil
}
// have: a valid signature, the signature's owner, and a user assertion to
// match against
e.G().Log.Debug("checking signed by assertion: %q", e.arg.SignedBy)
// load the user in SignedBy
arg := keybase1.Identify2Arg{
UserAssertion: e.arg.SignedBy,
AlwaysBlock: true,
NeedProofSet: true,
NoSkipSelf: true,
}
eng := NewResolveThenIdentify2(e.G(), &arg)
if err := RunEngine(eng, ctx); err != nil {
return err
}
signByUser := eng.Result().Upk
// check if it is equal to signature owner
if !e.signer.GetUID().Equal(signByUser.Uid) {
return libkb.BadSigError{
E: fmt.Sprintf("Signer %q did not match signed by assertion %q", e.signer.GetName(), e.arg.SignedBy),
}
}
return nil
}