/
keys.go
374 lines (319 loc) · 11.4 KB
/
keys.go
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package teams
import (
"crypto/hmac"
"crypto/rand"
"crypto/sha512"
"encoding/base64"
"errors"
"fmt"
"github.com/keybase/client/go/libkb"
"github.com/keybase/client/go/protocol/keybase1"
"golang.org/x/crypto/nacl/box"
"golang.org/x/crypto/nacl/secretbox"
"golang.org/x/net/context"
)
// Get a PTK seed and verify against the sigchain that is the correct key.
func GetAndVerifyPerTeamKey(mctx libkb.MetaContext, teamData *keybase1.TeamData,
gen keybase1.PerTeamKeyGeneration) (ret keybase1.PerTeamKeySeedItem, err error) {
ret, ok := teamData.PerTeamKeySeedsUnverified[gen]
if !ok {
return ret, libkb.NotFoundError{
Msg: fmt.Sprintf("no team secret found at generation %v", gen)}
}
km, err := NewTeamKeyManagerWithSecret(ret.Seed, gen)
if err != nil {
return ret, err
}
chainKey, err := TeamSigChainState{inner: teamData.Chain}.GetPerTeamKeyAtGeneration(gen)
if err != nil {
return ret, err
}
// Takes roughly 280us on android (Honor 6X)
localSigKey, err := km.SigningKey()
if err != nil {
return ret, err
}
// Takes roughly 900us on android (Honor 6X)
localEncKey, err := km.EncryptionKey()
if err != nil {
return ret, err
}
if !chainKey.SigKID.SecureEqual(localSigKey.GetKID()) {
mctx.CDebugf("sig KID gen:%v (local) %v != %v (chain)", gen, localSigKey.GetKID(), chainKey.SigKID)
return ret, fmt.Errorf("wrong team key found at generation %v", gen)
}
if !chainKey.EncKID.SecureEqual(localEncKey.GetKID()) {
mctx.CDebugf("enc KID gen:%v (local) %v != %v (chain)", gen, localEncKey.GetKID(), chainKey.EncKID)
return ret, fmt.Errorf("wrong team key (enc) found at generation %v", gen)
}
return ret, nil
}
type PerTeamSharedSecretBoxes struct {
Generation keybase1.PerTeamKeyGeneration `json:"generation"`
EncryptingKid keybase1.KID `json:"encrypting_kid"`
Nonce string `json:"nonce"`
PrevKey *prevKeySealedEncoded `json:"prev"`
Boxes map[keybase1.UID]string `json:"boxes"`
}
type PerTeamSharedSecretBox struct {
_struct bool `codec:",toarray"`
Version uint
PerUserKeySeqno keybase1.Seqno
NonceCounter uint32
Ctext []byte
}
type TeamKeyManager struct {
sharedSecret keybase1.PerTeamKeySeed
generation keybase1.PerTeamKeyGeneration
encryptionKey *libkb.NaclDHKeyPair
signingKey *libkb.NaclSigningKeyPair
}
func NewTeamKeyManager(g *libkb.GlobalContext) (*TeamKeyManager, error) {
sharedSecret, err := newSharedSecret()
if err != nil {
return nil, err
}
return NewTeamKeyManagerWithSecret(sharedSecret, 1)
}
func NewTeamKeyManagerWithSecret(secret keybase1.PerTeamKeySeed, generation keybase1.PerTeamKeyGeneration) (*TeamKeyManager, error) {
return &TeamKeyManager{
sharedSecret: secret,
generation: generation,
}, nil
}
// SharedSecret returns the team's shared secret.
func (t *TeamKeyManager) SharedSecret() keybase1.PerTeamKeySeed {
return t.sharedSecret
}
// EncryptionKey returns the derived NaclSigningKeyPair from the team's shared secret.
func (t *TeamKeyManager) SigningKey() (libkb.NaclSigningKeyPair, error) {
if t.signingKey == nil {
key, err := libkb.MakeNaclSigningKeyPairFromSecretBytes(derivedSecret(t.sharedSecret, libkb.TeamEdDSADerivationString))
if err != nil {
return libkb.NaclSigningKeyPair{}, err
}
t.signingKey = &key
}
return *t.signingKey, nil
}
// EncryptionKey returns the derived NaclDHKeyPair from the team's shared secret.
func (t *TeamKeyManager) EncryptionKey() (libkb.NaclDHKeyPair, error) {
if t.encryptionKey == nil {
key, err := libkb.MakeNaclDHKeyPairFromSecretBytes(derivedSecret(t.sharedSecret, libkb.TeamDHDerivationString))
if err != nil {
return libkb.NaclDHKeyPair{}, err
}
t.encryptionKey = &key
}
return *t.encryptionKey, nil
}
// SharedSecretBoxes creates the PerTeamSharedSecretBoxes for recipients with the
// existing team shared secret.
func (t *TeamKeyManager) SharedSecretBoxes(mctx libkb.MetaContext, senderKey libkb.GenericKey, recipients map[keybase1.UserVersion]keybase1.PerUserKey) (boxes *PerTeamSharedSecretBoxes, err error) {
defer mctx.CTrace("SharedSecretBoxes", func() error { return err })()
// make the nonce prefix, skipping the zero counter
// (0 used for previous key encryption nonce)
n, err := newNonce24SkipZero()
if err != nil {
return nil, err
}
// make the recipient boxes with the new secret and the nonce prefix
return t.sharedBoxes(t.sharedSecret, t.generation, n, senderKey, recipients)
}
// RotateSharedSecretBoxes creates a new shared secret for the team and the
// required PerTeamKey section.
func (t *TeamKeyManager) RotateSharedSecretBoxes(mctx libkb.MetaContext, senderKey libkb.GenericKey, recipients map[keybase1.UserVersion]keybase1.PerUserKey) (boxes *PerTeamSharedSecretBoxes, keySection *SCPerTeamKey, err error) {
defer mctx.CTrace("RotateSharedSecretBoxes", func() error { return err })()
// make a new secret
nextSecret, err := newSharedSecret()
if err != nil {
return nil, nil, err
}
// derive new key from new secret for PrevKey
key := derivedSecret(nextSecret, libkb.TeamPrevKeySecretBoxDerivationString)
var keyb [32]byte
copy(keyb[:], key)
// encrypt existing secret with derived key and nonce counter 0
nonce, err := newNonce24()
if err != nil {
return nil, nil, err
}
nonceBytes, counter := nonce.Nonce()
if counter != 0 {
// this should never happen, but might as well make sure it is zero
return nil, nil, errors.New("nonce counter not 0 for first use")
}
sealed := secretbox.Seal(nil, t.sharedSecret.ToBytes(), &nonceBytes, &keyb)
// encode encrypted prev key
prevKeyEncoded, err := encodeSealedPrevKey(nonceBytes, sealed)
if err != nil {
return nil, nil, err
}
// make the recipient boxes with the new secret and the incrementing nonce24
t.setNextSharedSecret(mctx, nextSecret)
boxes, err = t.sharedBoxes(t.sharedSecret, t.generation, nonce, senderKey, recipients)
if err != nil {
return nil, nil, err
}
// insert encoded encrypted PrevKey
boxes.PrevKey = &prevKeyEncoded
// need a new PerTeamKey section since the key was rotated
keySection, err = t.perTeamKeySection()
if err != nil {
return nil, nil, err
}
return boxes, keySection, nil
}
func (t *TeamKeyManager) sharedBoxes(secret keybase1.PerTeamKeySeed, generation keybase1.PerTeamKeyGeneration, nonce *nonce24, senderKey libkb.GenericKey, recipients map[keybase1.UserVersion]keybase1.PerUserKey) (*PerTeamSharedSecretBoxes, error) {
senderNaclDHKey, ok := senderKey.(libkb.NaclDHKeyPair)
if !ok {
return nil, fmt.Errorf("got an unexpected key type for device encryption key: %T", senderKey)
}
boxes, err := t.recipientBoxes(secret, nonce, senderNaclDHKey, recipients)
if err != nil {
return nil, err
}
return &PerTeamSharedSecretBoxes{
Generation: generation,
EncryptingKid: senderNaclDHKey.GetKID(),
Nonce: nonce.PrefixEncoded(),
Boxes: boxes,
}, nil
}
func (t *TeamKeyManager) recipientBoxes(secret keybase1.PerTeamKeySeed, nonce *nonce24, senderKey libkb.NaclDHKeyPair, recipients map[keybase1.UserVersion]keybase1.PerUserKey) (map[keybase1.UID]string, error) {
boxes := make(map[keybase1.UID]string)
for uv, recipientPerUserKey := range recipients {
boxStruct, err := t.recipientBox(secret, nonce, senderKey, recipientPerUserKey)
if err != nil {
return nil, err
}
encodedArray, err := libkb.MsgpackEncode(boxStruct)
if err != nil {
return nil, err
}
boxes[uv.Uid] = base64.StdEncoding.EncodeToString(encodedArray)
}
return boxes, nil
}
func (t *TeamKeyManager) recipientBox(secret keybase1.PerTeamKeySeed, nonce *nonce24, senderKey libkb.NaclDHKeyPair, recipient keybase1.PerUserKey) (*PerTeamSharedSecretBox, error) {
recipientPerUserGenericKeypair, err := libkb.ImportKeypairFromKID(recipient.EncKID)
if err != nil {
return nil, err
}
recipientPerUserNaclKeypair, ok := recipientPerUserGenericKeypair.(libkb.NaclDHKeyPair)
if !ok {
return nil, fmt.Errorf("got an unexpected key type for recipient KID in sharedTeamKeyBox: %T", recipientPerUserGenericKeypair)
}
nonceBytes, nonceCounter := nonce.Nonce()
ctext := box.Seal(nil, secret[:], &nonceBytes, ((*[32]byte)(&recipientPerUserNaclKeypair.Public)), ((*[32]byte)(senderKey.Private)))
boxStruct := PerTeamSharedSecretBox{
Version: libkb.SharedTeamKeyBoxVersion1,
PerUserKeySeqno: recipient.Seqno,
NonceCounter: nonceCounter,
Ctext: ctext,
}
return &boxStruct, nil
}
func (t *TeamKeyManager) perTeamKeySection() (*SCPerTeamKey, error) {
sigKey, err := t.SigningKey()
if err != nil {
return nil, err
}
encKey, err := t.EncryptionKey()
if err != nil {
return nil, err
}
return &SCPerTeamKey{
Generation: keybase1.PerTeamKeyGeneration(t.generation),
SigKID: sigKey.GetKID(),
EncKID: encKey.GetKID(),
}, nil
}
func (t *TeamKeyManager) setNextSharedSecret(mctx libkb.MetaContext, secret keybase1.PerTeamKeySeed) {
t.sharedSecret = secret
// bump generation number
t.generation = t.generation + 1
// clear out derived keys
t.signingKey = nil
t.encryptionKey = nil
mctx.CDebugf("TeamKeyManager: set next shared secret, generation %d", t.generation)
}
type prevKeySealedDecoded struct {
_struct bool `codec:",toarray"`
Version int
Nonce [24]byte
Key []byte
}
type prevKeySealedEncoded string
func encodeSealedPrevKey(nonceBytes [24]byte, key []byte) (prevKeySealedEncoded, error) {
prevKey := prevKeySealedDecoded{
Version: 1,
Nonce: nonceBytes,
Key: key,
}
packed, err := libkb.MsgpackEncode(prevKey)
if err != nil {
return "", err
}
encoded := base64.StdEncoding.EncodeToString(packed)
return prevKeySealedEncoded(encoded), nil
}
func decodeSealedPrevKey(e prevKeySealedEncoded) (nonce [24]byte, ctext []byte, err error) {
decoded, err := base64.StdEncoding.DecodeString(string(e))
if err != nil {
return nonce, nil, err
}
var tmp prevKeySealedDecoded
err = libkb.MsgpackDecode(&tmp, decoded)
if err != nil {
return nonce, nil, err
}
if tmp.Version != 1 {
return nonce, nil, fmt.Errorf("can only handle V1 encrypted prevs")
}
return tmp.Nonce, tmp.Key, nil
}
func newSharedSecret() (ret keybase1.PerTeamKeySeed, err error) {
n, err := rand.Read(ret[:])
if err != nil {
return ret, err
}
if n != len(ret) {
return ret, errors.New("short random read in newSharedSecret")
}
return ret, nil
}
func derivedSecret(secret keybase1.PerTeamKeySeed, context string) []byte {
if secret.IsZero() {
panic("Should never be using a zero key in derivedSecret; something went terribly wrong")
}
digest := hmac.New(sha512.New, secret[:])
digest.Write([]byte(context))
return digest.Sum(nil)[:32]
}
// Decrypt a single prev secretbox.
// Takes a prev to decrypt and the seed of the successor generation.
// For example (prev[3], seed[4]) -> seed[3]
func decryptPrevSingle(ctx context.Context,
prevToDecrypt prevKeySealedEncoded, successor keybase1.PerTeamKeySeed) (*keybase1.PerTeamKeySeed, error) {
if successor.IsZero() {
return nil, fmt.Errorf("Got 0 key, which can't be right")
}
if len(prevToDecrypt) == 0 {
return nil, fmt.Errorf("zero-length encoded prev")
}
nonce, ctext, err := decodeSealedPrevKey(prevToDecrypt)
if err != nil {
return nil, err
}
var keyFixed [32]byte
// prev key to decrypt with
key := derivedSecret(successor, libkb.TeamPrevKeySecretBoxDerivationString)
copy(keyFixed[:], key)
opened, ok := secretbox.Open(nil, ctext, &nonce, &keyFixed)
if !ok {
return nil, fmt.Errorf("prev decryption failed")
}
ret, err := keybase1.PerTeamKeySeedFromBytes(opened)
return &ret, err
}