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Merge pull request #2054 from tendermint/dev/secret_connection 

secret connection update
This commit is contained in:
Alexander Simmerl 2018-07-26 00:29:36 +02:00 committed by GitHub
parent 66fe5b7bae 7bf28af590
commit bdab37a626
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
4 changed files with 104 additions and 112 deletions
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1
CHANGELOG_PENDING.md
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@ -5,6 +5,7 @@ BREAKING CHANGES:
- breaks serialization/signing of all messages with a timestamp
- [abci] Removed Fee from ResponseDeliverTx and ResponseCheckTx
- [tools] Removed `make ensure_deps` in favor of `make get_vendor_deps`
- [p2p] Remove salsa and ripemd primitives, in favor of using chacha as a stream cipher, and hkdf
FEATURES:
- [tools] Added `make check_dep`

2
Gopkg.lock generated
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@ -143,6 +143,7 @@
".",
"hcl/ast",
"hcl/parser",
"hcl/printer",
"hcl/scanner",
"hcl/strconv",
"hcl/token",
@ -538,6 +539,7 @@
"github.com/tendermint/go-amino",
"golang.org/x/crypto/bcrypt",
"golang.org/x/crypto/chacha20poly1305",
"golang.org/x/crypto/curve25519",
"golang.org/x/crypto/hkdf",
"golang.org/x/crypto/nacl/box",
"golang.org/x/crypto/nacl/secretbox",

29
docs/spec/p2p/peer.md
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@ -27,27 +27,24 @@ Both handshakes have configurable timeouts (they should complete quickly).
### Authenticated Encryption Handshake
Tendermint implements the Station-to-Station protocol
using ED25519 keys for Diffie-Helman key-exchange and NACL SecretBox for encryption.
using X25519 keys for Diffie-Helman key-exchange and chacha20poly1305 for encryption.
It goes as follows:
- generate an emphemeral ED25519 keypair
- generate an ephemeral X25519 keypair
- send the ephemeral public key to the peer
- wait to receive the peer's ephemeral public key
- compute the Diffie-Hellman shared secret using the peers ephemeral public key and our ephemeral private key
- generate two nonces to use for encryption (sending and receiving) as follows:
- sort the ephemeral public keys in ascending order and concatenate them
- RIPEMD160 the result
- append 4 empty bytes (extending the hash to 24-bytes)
- the result is nonce1
- flip the last bit of nonce1 to get nonce2
- if we had the smaller ephemeral pubkey, use nonce1 for receiving, nonce2 for sending;
else the opposite
- all communications from now on are encrypted using the shared secret and the nonces, where each nonce
increments by 2 every time it is used
- generate two keys to use for encryption (sending and receiving) and a challenge for authentication as follows:
- create a hkdf-sha256 instance with the key being the diffie hellman shared secret, and info parameter as
`TENDERMINT_SECRET_CONNECTION_KEY_AND_CHALLENGE_GEN`
- get 96 bytes of output from hkdf-sha256
- if we had the smaller ephemeral pubkey, use the first 32 bytes for the key for receiving, the second 32 bytes for sending; else the opposite
- use the last 32 bytes of output for the challenge
- use a seperate nonce for receiving and sending. Both nonces start at 0, and should support the full 96 bit nonce range
- all communications from now on are encrypted in 1024 byte frames,
using the respective secret and nonce. Each nonce is incremented by one after each use.
- we now have an encrypted channel, but still need to authenticate
- generate a common challenge to sign:
- SHA256 of the sorted (lowest first) and concatenated ephemeral pub keys
- sign the common challenge with our persistent private key
- send the go-wire encoded persistent pubkey and signature to the peer
- sign the common challenge obtained from the hkdf with our persistent private key
- send the amino encoded persistent pubkey and signature to the peer
- wait to receive the persistent public key and signature from the peer
- verify the signature on the challenge using the peer's persistent public key

184
p2p/conn/secret_connection.go
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@ -1,9 +1,3 @@
// Uses nacl's secret_box to encrypt a net.Conn.
// It is (meant to be) an implementation of the STS protocol.
// Note we do not (yet) assume that a remote peer's pubkey
// is known ahead of time, and thus we are technically
// still vulnerable to MITM. (TODO!)
// See docs/sts-final.pdf for more info
package conn
import (
@ -16,36 +10,45 @@ import (
"net"
"time"
"golang.org/x/crypto/chacha20poly1305"
"golang.org/x/crypto/curve25519"
"golang.org/x/crypto/nacl/box"
"golang.org/x/crypto/nacl/secretbox"
"golang.org/x/crypto/ripemd160"
"github.com/tendermint/tendermint/crypto"
cmn "github.com/tendermint/tendermint/libs/common"
"golang.org/x/crypto/hkdf"
)
// 4 + 1024 == 1028 total frame size
const dataLenSize = 4
const dataMaxSize = 1024
const totalFrameSize = dataMaxSize + dataLenSize
const sealedFrameSize = totalFrameSize + secretbox.Overhead
const aeadSizeOverhead = 16 // overhead of poly 1305 authentication tag
const aeadKeySize = chacha20poly1305.KeySize
const aeadNonceSize = chacha20poly1305.NonceSize
// Implements net.Conn
// SecretConnection implements net.conn.
// It is an implementation of the STS protocol.
// Note we do not (yet) assume that a remote peer's pubkey
// is known ahead of time, and thus we are technically
// still vulnerable to MITM. (TODO!)
// See docs/sts-final.pdf for more info
type SecretConnection struct {
conn io.ReadWriteCloser
recvBuffer []byte
recvNonce *[24]byte
sendNonce *[24]byte
recvNonce *[aeadNonceSize]byte
sendNonce *[aeadNonceSize]byte
recvSecret *[aeadKeySize]byte
sendSecret *[aeadKeySize]byte
remPubKey crypto.PubKey
shrSecret *[32]byte // shared secret
}
// Performs handshake and returns a new authenticated SecretConnection.
// Returns nil if error in handshake.
// MakeSecretConnection performs handshake and returns a new authenticated
// SecretConnection.
// Returns nil if there is an error in handshake.
// Caller should call conn.Close()
// See docs/sts-final.pdf for more information.
func MakeSecretConnection(conn io.ReadWriteCloser, locPrivKey crypto.PrivKey) (*SecretConnection, error) {
locPubKey := locPrivKey.PubKey()
// Generate ephemeral keys for perfect forward secrecy.
@ -59,29 +62,27 @@ func MakeSecretConnection(conn io.ReadWriteCloser, locPrivKey crypto.PrivKey) (*
return nil, err
}
// Compute common shared secret.
shrSecret := computeSharedSecret(remEphPub, locEphPriv)
// Sort by lexical order.
loEphPub, hiEphPub := sort32(locEphPub, remEphPub)
loEphPub, _ := sort32(locEphPub, remEphPub)
// Check if the local ephemeral public key
// was the least, lexicographically sorted.
locIsLeast := bytes.Equal(locEphPub[:], loEphPub[:])
// Generate nonces to use for secretbox.
recvNonce, sendNonce := genNonces(loEphPub, hiEphPub, locIsLeast)
// Compute common diffie hellman secret using X25519.
dhSecret := computeDHSecret(remEphPub, locEphPriv)
// Generate common challenge to sign.
challenge := genChallenge(loEphPub, hiEphPub)
// generate the secret used for receiving, sending, challenge via hkdf-sha2 on dhSecret
recvSecret, sendSecret, challenge := deriveSecretAndChallenge(dhSecret, locIsLeast)
// Construct SecretConnection.
sc := &SecretConnection{
conn: conn,
recvBuffer: nil,
recvNonce: recvNonce,
sendNonce: sendNonce,
shrSecret: shrSecret,
recvNonce: new([aeadNonceSize]byte),
sendNonce: new([aeadNonceSize]byte),
recvSecret: recvSecret,
sendSecret: sendSecret,
}
// Sign the challenge bytes for authentication.
@ -92,6 +93,7 @@ func MakeSecretConnection(conn io.ReadWriteCloser, locPrivKey crypto.PrivKey) (*
if err != nil {
return nil, err
}
remPubKey, remSignature := authSigMsg.Key, authSigMsg.Sig
if !remPubKey.VerifyBytes(challenge[:], remSignature) {
return nil, errors.New("Challenge verification failed")
@ -102,7 +104,7 @@ func MakeSecretConnection(conn io.ReadWriteCloser, locPrivKey crypto.PrivKey) (*
return sc, nil
}
// Returns authenticated remote pubkey
// RemotePubKey returns authenticated remote pubkey
func (sc *SecretConnection) RemotePubKey() crypto.PubKey {
return sc.remPubKey
}
@ -124,14 +126,17 @@ func (sc *SecretConnection) Write(data []byte) (n int, err error) {
binary.BigEndian.PutUint32(frame, uint32(chunkLength))
copy(frame[dataLenSize:], chunk)
aead, err := chacha20poly1305.New(sc.sendSecret[:])
if err != nil {
return n, errors.New("Invalid SecretConnection Key")
}
// encrypt the frame
var sealedFrame = make([]byte, sealedFrameSize)
secretbox.Seal(sealedFrame[:0], frame, sc.sendNonce, sc.shrSecret)
// fmt.Printf("secretbox.Seal(sealed:%X,sendNonce:%X,shrSecret:%X\n", sealedFrame, sc.sendNonce, sc.shrSecret)
incr2Nonce(sc.sendNonce)
var sealedFrame = make([]byte, aeadSizeOverhead+totalFrameSize)
aead.Seal(sealedFrame[:0], sc.sendNonce[:], frame, nil)
incrNonce(sc.sendNonce)
// end encryption
_, err := sc.conn.Write(sealedFrame)
_, err = sc.conn.Write(sealedFrame)
if err != nil {
return n, err
}
@ -148,7 +153,11 @@ func (sc *SecretConnection) Read(data []byte) (n int, err error) {
return
}
sealedFrame := make([]byte, sealedFrameSize)
aead, err := chacha20poly1305.New(sc.recvSecret[:])
if err != nil {
return n, errors.New("Invalid SecretConnection Key")
}
sealedFrame := make([]byte, totalFrameSize+aeadSizeOverhead)
_, err = io.ReadFull(sc.conn, sealedFrame)
if err != nil {
return
@ -156,12 +165,11 @@ func (sc *SecretConnection) Read(data []byte) (n int, err error) {
// decrypt the frame
var frame = make([]byte, totalFrameSize)
// fmt.Printf("secretbox.Open(sealed:%X,recvNonce:%X,shrSecret:%X\n", sealedFrame, sc.recvNonce, sc.shrSecret)
_, ok := secretbox.Open(frame[:0], sealedFrame, sc.recvNonce, sc.shrSecret)
if !ok {
_, err = aead.Open(frame[:0], sc.recvNonce[:], sealedFrame, nil)
if err != nil {
return n, errors.New("Failed to decrypt SecretConnection")
}
incr2Nonce(sc.recvNonce)
incrNonce(sc.recvNonce)
// end decryption
var chunkLength = binary.BigEndian.Uint32(frame) // read the first two bytes
@ -176,6 +184,7 @@ func (sc *SecretConnection) Read(data []byte) (n int, err error) {
}
// Implements net.Conn
// nolint
func (sc *SecretConnection) Close() error { return sc.conn.Close() }
func (sc *SecretConnection) LocalAddr() net.Addr { return sc.conn.(net.Conn).LocalAddr() }
func (sc *SecretConnection) RemoteAddr() net.Addr { return sc.conn.(net.Conn).RemoteAddr() }
@ -204,18 +213,16 @@ func shareEphPubKey(conn io.ReadWriteCloser, locEphPub *[32]byte) (remEphPub *[3
var _, err1 = cdc.MarshalBinaryWriter(conn, locEphPub)
if err1 != nil {
return nil, err1, true // abort
} else {
return nil, nil, false
}
return nil, nil, false
},
func(_ int) (val interface{}, err error, abort bool) {
var _remEphPub [32]byte
var _, err2 = cdc.UnmarshalBinaryReader(conn, &_remEphPub, 1024*1024) // TODO
if err2 != nil {
return nil, err2, true // abort
} else {
return _remEphPub, nil, false
}
return _remEphPub, nil, false
},
)
@ -230,9 +237,40 @@ func shareEphPubKey(conn io.ReadWriteCloser, locEphPub *[32]byte) (remEphPub *[3
return &_remEphPub, nil
}
func computeSharedSecret(remPubKey, locPrivKey *[32]byte) (shrSecret *[32]byte) {
shrSecret = new([32]byte)
box.Precompute(shrSecret, remPubKey, locPrivKey)
func deriveSecretAndChallenge(dhSecret *[32]byte, locIsLeast bool) (recvSecret, sendSecret *[aeadKeySize]byte, challenge *[32]byte) {
hash := sha256.New
hkdf := hkdf.New(hash, dhSecret[:], nil, []byte("TENDERMINT_SECRET_CONNECTION_KEY_AND_CHALLENGE_GEN"))
// get enough data for 2 aead keys, and a 32 byte challenge
res := new([2*aeadKeySize + 32]byte)
_, err := io.ReadFull(hkdf, res[:])
if err != nil {
panic(err)
}
challenge = new([32]byte)
recvSecret = new([aeadKeySize]byte)
sendSecret = new([aeadKeySize]byte)
// Use the last 32 bytes as the challenge
copy(challenge[:], res[2*aeadKeySize:2*aeadKeySize+32])
// bytes 0 through aeadKeySize - 1 are one aead key.
// bytes aeadKeySize through 2*aeadKeySize -1 are another aead key.
// which key corresponds to sending and receiving key depends on whether
// the local key is less than the remote key.
if locIsLeast {
copy(recvSecret[:], res[0:aeadKeySize])
copy(sendSecret[:], res[aeadKeySize:aeadKeySize*2])
} else {
copy(sendSecret[:], res[0:aeadKeySize])
copy(recvSecret[:], res[aeadKeySize:aeadKeySize*2])
}
return
}
func computeDHSecret(remPubKey, locPrivKey *[32]byte) (shrKey *[32]byte) {
shrKey = new([32]byte)
curve25519.ScalarMult(shrKey, locPrivKey, remPubKey)
return
}
@ -247,25 +285,6 @@ func sort32(foo, bar *[32]byte) (lo, hi *[32]byte) {
return
}
func genNonces(loPubKey, hiPubKey *[32]byte, locIsLo bool) (recvNonce, sendNonce *[24]byte) {
nonce1 := hash24(append(loPubKey[:], hiPubKey[:]...))
nonce2 := new([24]byte)
copy(nonce2[:], nonce1[:])
nonce2[len(nonce2)-1] ^= 0x01
if locIsLo {
recvNonce = nonce1
sendNonce = nonce2
} else {
recvNonce = nonce2
sendNonce = nonce1
}
return
}
func genChallenge(loPubKey, hiPubKey *[32]byte) (challenge *[32]byte) {
return hash32(append(loPubKey[:], hiPubKey[:]...))
}
func signChallenge(challenge *[32]byte, locPrivKey crypto.PrivKey) (signature crypto.Signature) {
signature, err := locPrivKey.Sign(challenge[:])
// TODO(ismail): let signChallenge return an error instead
@ -288,18 +307,16 @@ func shareAuthSignature(sc *SecretConnection, pubKey crypto.PubKey, signature cr
var _, err1 = cdc.MarshalBinaryWriter(sc, authSigMessage{pubKey, signature})
if err1 != nil {
return nil, err1, true // abort
} else {
return nil, nil, false
}
return nil, nil, false
},
func(_ int) (val interface{}, err error, abort bool) {
var _recvMsg authSigMessage
var _, err2 = cdc.UnmarshalBinaryReader(sc, &_recvMsg, 1024*1024) // TODO
if err2 != nil {
return nil, err2, true // abort
} else {
return _recvMsg, nil, false
}
return _recvMsg, nil, false
},
)
@ -315,36 +332,11 @@ func shareAuthSignature(sc *SecretConnection, pubKey crypto.PubKey, signature cr
//--------------------------------------------------------------------------------
// sha256
func hash32(input []byte) (res *[32]byte) {
hasher := sha256.New()
hasher.Write(input) // nolint: errcheck, gas
resSlice := hasher.Sum(nil)
res = new([32]byte)
copy(res[:], resSlice)
return
}
// We only fill in the first 20 bytes with ripemd160
func hash24(input []byte) (res *[24]byte) {
hasher := ripemd160.New()
hasher.Write(input) // nolint: errcheck, gas
resSlice := hasher.Sum(nil)
res = new([24]byte)
copy(res[:], resSlice)
return
}
// increment nonce big-endian by 2 with wraparound.
func incr2Nonce(nonce *[24]byte) {
incrNonce(nonce)
incrNonce(nonce)
}
// increment nonce big-endian by 1 with wraparound.
func incrNonce(nonce *[24]byte) {
for i := 23; 0 <= i; i-- {
func incrNonce(nonce *[aeadNonceSize]byte) {
for i := aeadNonceSize - 1; 0 <= i; i-- {
nonce[i]++
// if this byte wrapped around to zero, we need to increment the next byte
if nonce[i] != 0 {
return
}