Merge remote-tracking branch 'go/release-branch.go1.26' into update-go1.26-rc2

Author: awly

VERSION

@@ -1,2 +1,2 @@
-go1.26rc2
-time 2026-01-08T21:54:29Z
+go1.26rc3
+time 2026-02-03T20:09:49Z

src/crypto/tls/common.go

@@ -22,6 +22,7 @@ import (
 	"internal/godebug"
 	"io"
 	"net"
+	"runtime"
 	"slices"
 	"strings"
 	"sync"
@@ -632,10 +633,13 @@ type Config struct {
 	// If GetConfigForClient is nil, the Config passed to Server() will be
 	// used for all connections.
 	//
-	// If SessionTicketKey was explicitly set on the returned Config, or if
-	// SetSessionTicketKeys was called on the returned Config, those keys will
+	// If SessionTicketKey is explicitly set on the returned Config, or if
+	// SetSessionTicketKeys is called on the returned Config, those keys will
 	// be used. Otherwise, the original Config keys will be used (and possibly
-	// rotated if they are automatically managed).
+	// rotated if they are automatically managed). WARNING: this allows session
+	// resumtion of connections originally established with the parent (or a
+	// sibling) Config, which may bypass the [Config.VerifyPeerCertificate]
+	// value of the returned Config.
 	GetConfigForClient func(*ClientHelloInfo) (*Config, error)
 
 	// VerifyPeerCertificate, if not nil, is called after normal
@@ -653,8 +657,10 @@ type Config struct {
 	// rawCerts may be empty on the server if ClientAuth is RequestClientCert or
 	// VerifyClientCertIfGiven.
 	//
-	// This callback is not invoked on resumed connections, as certificates are
-	// not re-verified on resumption.
+	// This callback is not invoked on resumed connections. WARNING: this
+	// includes connections resumed across Configs returned by [Config.Clone] or
+	// [Config.GetConfigForClient] and their parents. If that is not intended,
+	// use [Config.VerifyConnection] instead, or set [Config.SessionTicketsDisabled].
 	//
 	// verifiedChains and its contents should not be modified.
 	VerifyPeerCertificate func(rawCerts [][]byte, verifiedChains [][]*x509.Certificate) error
@@ -978,8 +984,15 @@ func (c *Config) ticketKeyFromBytes(b [32]byte) (key ticketKey) {
 // ticket, and the lifetime we set for all tickets we send.
 const maxSessionTicketLifetime = 7 * 24 * time.Hour
 
-// Clone returns a shallow clone of c or nil if c is nil. It is safe to clone a [Config] that is
-// being used concurrently by a TLS client or server.
+// Clone returns a shallow clone of c or nil if c is nil. It is safe to clone a
+// [Config] that is being used concurrently by a TLS client or server.
+//
+// The returned Config can share session ticket keys with the original Config,
+// which means connections could be resumed across the two Configs. WARNING:
+// [Config.VerifyPeerCertificate] does not get called on resumed connections,
+// including connections that were originally established on the parent Config.
+// If that is not intended, use [Config.VerifyConnection] instead, or set
+// [Config.SessionTicketsDisabled].
 func (c *Config) Clone() *Config {
 	if c == nil {
 		return nil
@@ -1861,15 +1874,27 @@ func anyValidVerifiedChain(verifiedChains [][]*x509.Certificate, opts x509.Verif
 		}) {
 			continue
 		}
-		// Since we already validated the chain, we only care that it is
-		// rooted in a CA in CAs, or in the system pool. On platforms where
-		// we control chain validation (e.g. not Windows or macOS) this is a
-		// simple lookup in the CertPool internal hash map. On other
-		// platforms, this may be more expensive, depending on how they
-		// implement verification of just root certificates.
-		root := chain[len(chain)-1]
-		if _, err := root.Verify(opts); err == nil {
-			return true
+		// Since we already validated the chain, we only care that it is rooted
+		// in a CA in opts.Roots. On platforms where we control chain validation
+		// (e.g. not Windows or macOS) this is a simple lookup in the CertPool
+		// internal hash map, which we can simulate by running Verify on the
+		// root. On other platforms, we have to do full verification again,
+		// because EKU handling might differ. We will want to replace this with
+		// CertPool.Contains if/once that is available. See go.dev/issue/77376.
+		if runtime.GOOS == "windows" || runtime.GOOS == "darwin" || runtime.GOOS == "ios" {
+			opts.Intermediates = x509.NewCertPool()
+			for _, cert := range chain[1:max(1, len(chain)-1)] {
+				opts.Intermediates.AddCert(cert)
+			}
+			leaf := chain[0]
+			if _, err := leaf.Verify(opts); err == nil {
+				return true
+			}
+		} else {
+			root := chain[len(chain)-1]
+			if _, err := root.Verify(opts); err == nil {
+				return true
+			}
 		}
 	}
 	return false

src/crypto/tls/handshake_server_test.go

@@ -2302,7 +2302,7 @@ func testHandshakeGetConfigForClientDifferentClientCAs(t *testing.T, version uin
 	if err != nil {
 		t.Fatalf("ParseCertificate: %v", err)
 	}
-	rootDER, err = x509.CreateCertificate(rand.Reader, tmpl, tmpl, &testECDSAPrivateKey.PublicKey, testECDSAPrivateKey)
+	rootDER, err = x509.CreateCertificate(rand.Reader, tmpl, tmpl, &testRSA2048PrivateKey.PublicKey, testRSA2048PrivateKey)
 	if err != nil {
 		t.Fatalf("CreateCertificate: %v", err)
 	}
@@ -2318,15 +2318,19 @@ func testHandshakeGetConfigForClientDifferentClientCAs(t *testing.T, version uin
 		NotAfter:  now.Add(time.Hour * 24),
 		KeyUsage:  x509.KeyUsageDigitalSignature,
 	}
-	certDER, err := x509.CreateCertificate(rand.Reader, tmpl, rootA, &testECDSAPrivateKey.PublicKey, testECDSAPrivateKey)
+	certA, err := x509.CreateCertificate(rand.Reader, tmpl, rootA, &testECDSAPrivateKey.PublicKey, testECDSAPrivateKey)
+	if err != nil {
+		t.Fatalf("CreateCertificate: %v", err)
+	}
+	certB, err := x509.CreateCertificate(rand.Reader, tmpl, rootB, &testECDSAPrivateKey.PublicKey, testRSA2048PrivateKey)
 	if err != nil {
 		t.Fatalf("CreateCertificate: %v", err)
 	}
 
 	serverConfig := testConfig.Clone()
 	serverConfig.MaxVersion = version
 	serverConfig.Certificates = []Certificate{{
-		Certificate: [][]byte{certDER},
+		Certificate: [][]byte{certA},
 		PrivateKey:  testECDSAPrivateKey,
 	}}
 	serverConfig.Time = func() time.Time {
@@ -2351,7 +2355,7 @@ func testHandshakeGetConfigForClientDifferentClientCAs(t *testing.T, version uin
 	clientConfig := testConfig.Clone()
 	clientConfig.MaxVersion = version
 	clientConfig.Certificates = []Certificate{{
-		Certificate: [][]byte{certDER},
+		Certificate: [][]byte{certA},
 		PrivateKey:  testECDSAPrivateKey,
 	}}
 	clientConfig.ClientSessionCache = NewLRUClientSessionCache(32)
@@ -2380,6 +2384,8 @@ func testHandshakeGetConfigForClientDifferentClientCAs(t *testing.T, version uin
 	testResume(t, serverConfig, clientConfig, false)
 	testResume(t, serverConfig, clientConfig, true)
 
+	clientConfig.Certificates[0].Certificate = [][]byte{certB}
+
 	// Cause GetConfigForClient to return a config cloned from the base config,
 	// but with a different ClientCAs pool. This should cause resumption to fail.
 	switchConfig = true
@@ -2414,7 +2420,7 @@ func testHandshakeChangeRootCAsResumption(t *testing.T, version uint16) {
 	if err != nil {
 		t.Fatalf("ParseCertificate: %v", err)
 	}
-	rootDER, err = x509.CreateCertificate(rand.Reader, tmpl, tmpl, &testECDSAPrivateKey.PublicKey, testECDSAPrivateKey)
+	rootDER, err = x509.CreateCertificate(rand.Reader, tmpl, tmpl, &testRSA2048PrivateKey.PublicKey, testRSA2048PrivateKey)
 	if err != nil {
 		t.Fatalf("CreateCertificate: %v", err)
 	}
@@ -2430,15 +2436,19 @@ func testHandshakeChangeRootCAsResumption(t *testing.T, version uint16) {
 		NotAfter:  now.Add(time.Hour * 24),
 		KeyUsage:  x509.KeyUsageDigitalSignature,
 	}
-	certDER, err := x509.CreateCertificate(rand.Reader, tmpl, rootA, &testECDSAPrivateKey.PublicKey, testECDSAPrivateKey)
+	certA, err := x509.CreateCertificate(rand.Reader, tmpl, rootA, &testECDSAPrivateKey.PublicKey, testECDSAPrivateKey)
+	if err != nil {
+		t.Fatalf("CreateCertificate: %v", err)
+	}
+	certB, err := x509.CreateCertificate(rand.Reader, tmpl, rootB, &testECDSAPrivateKey.PublicKey, testRSA2048PrivateKey)
 	if err != nil {
 		t.Fatalf("CreateCertificate: %v", err)
 	}
 
 	serverConfig := testConfig.Clone()
 	serverConfig.MaxVersion = version
 	serverConfig.Certificates = []Certificate{{
-		Certificate: [][]byte{certDER},
+		Certificate: [][]byte{certA},
 		PrivateKey:  testECDSAPrivateKey,
 	}}
 	serverConfig.Time = func() time.Time {
@@ -2453,7 +2463,7 @@ func testHandshakeChangeRootCAsResumption(t *testing.T, version uint16) {
 	clientConfig := testConfig.Clone()
 	clientConfig.MaxVersion = version
 	clientConfig.Certificates = []Certificate{{
-		Certificate: [][]byte{certDER},
+		Certificate: [][]byte{certA},
 		PrivateKey:  testECDSAPrivateKey,
 	}}
 	clientConfig.ClientSessionCache = NewLRUClientSessionCache(32)
@@ -2486,6 +2496,8 @@ func testHandshakeChangeRootCAsResumption(t *testing.T, version uint16) {
 	clientConfig.RootCAs = x509.NewCertPool()
 	clientConfig.RootCAs.AddCert(rootB)
 
+	serverConfig.Certificates[0].Certificate = [][]byte{certB}
+
 	testResume(t, serverConfig, clientConfig, false)
 	testResume(t, serverConfig, clientConfig, true)
 }

src/crypto/tls/tls_test.go

@@ -572,6 +572,41 @@ func TestVerifyHostname(t *testing.T) {
 	}
 }
 
+func TestRealResumption(t *testing.T) {
+	testenv.MustHaveExternalNetwork(t)
+
+	config := &Config{
+		ServerName:         "yahoo.com",
+		ClientSessionCache: NewLRUClientSessionCache(0),
+	}
+
+	for range 10 {
+		conn, err := Dial("tcp", "yahoo.com:443", config)
+		if err != nil {
+			t.Log("Dial error:", err)
+			continue
+		}
+		// Do a read to consume the NewSessionTicket messages.
+		fmt.Fprintf(conn, "GET / HTTP/1.1\r\nHost: yahoo.com\r\nConnection: close\r\n\r\n")
+		conn.Read(make([]byte, 4096))
+		conn.Close()
+
+		conn, err = Dial("tcp", "yahoo.com:443", config)
+		if err != nil {
+			t.Log("second Dial error:", err)
+			continue
+		}
+		state := conn.ConnectionState()
+		conn.Close()
+
+		if state.DidResume {
+			return
+		}
+	}
+
+	t.Fatal("no connection used session resumption")
+}
+
 func TestConnCloseBreakingWrite(t *testing.T) {
 	ln := newLocalListener(t)
 	defer ln.Close()

src/internal/poll/fd_mutex.go

@@ -265,7 +265,9 @@ func (fd *FD) readWriteLock() error {
 // is no remaining reference.
 func (fd *FD) readWriteUnlock() {
 	fd.fdmu.rwunlock(true)
-	fd.fdmu.rwunlock(false)
+	if fd.fdmu.rwunlock(false) {
+		fd.destroy()
+	}
 }
 
 // closing returns true if fd is closing.

src/os/os_test.go

@@ -3468,6 +3468,34 @@ func TestWriteStringAlloc(t *testing.T) {
 	}
 }
 
+// Test that it's OK to have parallel I/O and Close on a file.
+func TestFileIOCloseRace(t *testing.T) {
+	t.Parallel()
+	file, err := Create(filepath.Join(t.TempDir(), "test.txt"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	var wg sync.WaitGroup
+	wg.Go(func() {
+		var tmp [100]byte
+		if _, err := file.Write(tmp[:]); err != nil && !errors.Is(err, ErrClosed) {
+			t.Error(err)
+		}
+	})
+	wg.Go(func() {
+		var tmp [100]byte
+		if _, err := file.Read(tmp[:]); err != nil && err != io.EOF && !errors.Is(err, ErrClosed) {
+			t.Error(err)
+		}
+	})
+	wg.Go(func() {
+		if err := file.Close(); err != nil {
+			t.Error(err)
+		}
+	})
+	wg.Wait()
+}
+
 // Test that it's OK to have parallel I/O and Close on a pipe.
 func TestPipeIOCloseRace(t *testing.T) {
 	// Skip on wasm, which doesn't have pipes.