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device: use atomic access for unlocked keypair.next

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Go's GC semantics might not always guarantee the safety of this, and the
race detector gets upset too, so instead we wrap this all in atomic
accessors.

Reported-by: David Anderson <danderson@tailscale.com>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
This commit is contained in:
Jason A. Donenfeld 2020-05-02 01:30:23 -06:00
parent fdba6c183a
commit 28c4d04304
4 changed files with 23 additions and 11 deletions
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10
device/keypair.go
View file

@ -8,7 +8,9 @@ package device
import (
"crypto/cipher"
"sync"
"sync/atomic"
"time"
"unsafe"
"golang.zx2c4.com/wireguard/replay"
)
@ -38,6 +40,14 @@ type Keypairs struct {
next *Keypair
}
func (kp *Keypairs) storeNext(next *Keypair) {
atomic.StorePointer((*unsafe.Pointer)((unsafe.Pointer)(&kp.next)), (unsafe.Pointer)(next))
}
func (kp *Keypairs) loadNext() *Keypair {
return (*Keypair)(atomic.LoadPointer((*unsafe.Pointer)((unsafe.Pointer)(&kp.next))))
}
func (kp *Keypairs) Current() *Keypair {
kp.RLock()
defer kp.RUnlock()

16
device/noise-protocol.go
View file

@ -14,6 +14,7 @@ import (
"golang.org/x/crypto/blake2s"
"golang.org/x/crypto/chacha20poly1305"
"golang.org/x/crypto/poly1305"
"golang.zx2c4.com/wireguard/tai64n"
)
@ -583,12 +584,12 @@ func (peer *Peer) BeginSymmetricSession() error {
defer keypairs.Unlock()
previous := keypairs.previous
next := keypairs.next
next := keypairs.loadNext()
current := keypairs.current
if isInitiator {
if next != nil {
keypairs.next = nil
keypairs.storeNext(nil)
keypairs.previous = next
device.DeleteKeypair(current)
} else {
@ -597,7 +598,7 @@ func (peer *Peer) BeginSymmetricSession() error {
device.DeleteKeypair(previous)
keypairs.current = keypair
} else {
keypairs.next = keypair
keypairs.storeNext(keypair)
device.DeleteKeypair(next)
keypairs.previous = nil
device.DeleteKeypair(previous)
@ -608,18 +609,19 @@ func (peer *Peer) BeginSymmetricSession() error {
func (peer *Peer) ReceivedWithKeypair(receivedKeypair *Keypair) bool {
keypairs := &peer.keypairs
if keypairs.next != receivedKeypair {
if keypairs.loadNext() != receivedKeypair {
return false
}
keypairs.Lock()
defer keypairs.Unlock()
if keypairs.next != receivedKeypair {
if keypairs.loadNext() != receivedKeypair {
return false
}
old := keypairs.previous
keypairs.previous = keypairs.current
peer.device.DeleteKeypair(old)
keypairs.current = keypairs.next
keypairs.next = nil
keypairs.current = keypairs.loadNext()
keypairs.storeNext(nil)
return true
}

2
device/noise_test.go
View file

@ -113,7 +113,7 @@ func TestNoiseHandshake(t *testing.T) {
t.Fatal("failed to derive keypair for peer 2", err)
}
key1 := peer1.keypairs.next
key1 := peer1.keypairs.loadNext()
key2 := peer2.keypairs.current
// encrypting / decryption test

6
device/peer.go
View file

@ -223,10 +223,10 @@ func (peer *Peer) ZeroAndFlushAll() {
keypairs.Lock()
device.DeleteKeypair(keypairs.previous)
device.DeleteKeypair(keypairs.current)
device.DeleteKeypair(keypairs.next)
device.DeleteKeypair(keypairs.loadNext())
keypairs.previous = nil
keypairs.current = nil
keypairs.next = nil
keypairs.storeNext(nil)
keypairs.Unlock()
// clear handshake state
@ -254,7 +254,7 @@ func (peer *Peer) ExpireCurrentKeypairs() {
keypairs.current.sendNonce = RejectAfterMessages
}
if keypairs.next != nil {
keypairs.next.sendNonce = RejectAfterMessages
keypairs.loadNext().sendNonce = RejectAfterMessages
}
keypairs.Unlock()
}