caddytls: Fix data race in test (close #1844)

The race was in the test only; not in the production code

caddytls/crypto.go

@@ -21,6 +21,7 @@ import (
 	"net"
 	"os"
 	"path/filepath"
+	"sync"
 	"time"
 
 	"golang.org/x/crypto/ocsp"
@@ -243,8 +244,9 @@ func RotateSessionTicketKeys(cfg *tls.Config) chan struct{} {
 
 // Functions that may be swapped out for testing
 var (
-	runTLSTicketKeyRotation      = standaloneTLSTicketKeyRotation
-	setSessionTicketKeysTestHook = func(keys [][32]byte) [][32]byte { return keys }
+	runTLSTicketKeyRotation        = standaloneTLSTicketKeyRotation
+	setSessionTicketKeysTestHook   = func(keys [][32]byte) [][32]byte { return keys }
+	setSessionTicketKeysTestHookMu sync.Mutex
 )
 
 // standaloneTLSTicketKeyRotation governs over the array of TLS ticket keys used to de/crypt TLS tickets.
@@ -271,7 +273,10 @@ func standaloneTLSTicketKeyRotation(c *tls.Config, ticker *time.Ticker, exitChan
 		c.SessionTicketsDisabled = true // bail if we don't have the entropy for the first one
 		return
 	}
-	c.SetSessionTicketKeys(setSessionTicketKeysTestHook(keys))
+	setSessionTicketKeysTestHookMu.Lock()
+	setSessionTicketKeysHook := setSessionTicketKeysTestHook
+	setSessionTicketKeysTestHookMu.Unlock()
+	c.SetSessionTicketKeys(setSessionTicketKeysHook(keys))
 
 	for {
 		select {
@@ -298,7 +303,7 @@ func standaloneTLSTicketKeyRotation(c *tls.Config, ticker *time.Ticker, exitChan
 				keys[0] = newTicketKey
 			}
 			// pushes the last key out, doesn't matter that we don't have a new one
-			c.SetSessionTicketKeys(setSessionTicketKeysTestHook(keys))
+			c.SetSessionTicketKeys(setSessionTicketKeysHook(keys))
 		}
 	}
 }

caddytls/crypto_test.go

@@ -86,17 +86,20 @@ func TestStandaloneTLSTicketKeyRotation(t *testing.T) {
 
 	tlsGovChan := make(chan struct{})
 	defer close(tlsGovChan)
-	callSync := make(chan *syncPkt, 1)
-	defer close(callSync)
+	callSync := make(chan syncPkt)
 
+	setSessionTicketKeysTestHookMu.Lock()
 	oldHook := setSessionTicketKeysTestHook
 	defer func() {
+		setSessionTicketKeysTestHookMu.Lock()
 		setSessionTicketKeysTestHook = oldHook
+		setSessionTicketKeysTestHookMu.Unlock()
 	}()
 	setSessionTicketKeysTestHook = func(keys [][32]byte) [][32]byte {
-		callSync <- &syncPkt{keys[0], len(keys)}
+		callSync <- syncPkt{keys[0], len(keys)}
 		return keys
 	}
+	setSessionTicketKeysTestHookMu.Unlock()
 
 	c := new(tls.Config)
 	timer := time.NewTicker(time.Millisecond * 1)