GODRIVER-3302 Handle malformatted message length properly.

x/mongo/driver/topology/connection.go

@@ -9,6 +9,7 @@ package topology
 import (
 	"context"
 	"crypto/tls"
+	"encoding/binary"
 	"errors"
 	"fmt"
 	"io"
@@ -79,9 +80,9 @@ type connection struct {
 	driverConnectionID uint64
 	generation         uint64
 
-	// awaitingResponse indicates that the server response was not completely
+	// awaitRemainingBytes indicates the size of server response that was not completely
 	// read before returning the connection to the pool.
-	awaitingResponse bool
+	awaitRemainingBytes *int32
 
 	// oidcTokenGenID is the monotonic generation ID for OIDC tokens, used to invalidate
 	// accessTokens in the OIDC authenticator cache.
@@ -115,12 +116,6 @@ func newConnection(addr address.Address, opts ...ConnectionOption) *connection {
 	return c
 }
 
-// DriverConnectionID returns the driver connection ID.
-// TODO(GODRIVER-2824): change return type to int64.
-func (c *connection) DriverConnectionID() uint64 {
-	return c.driverConnectionID
-}
-
 // setGenerationNumber sets the connection's generation number if a callback has been provided to do so in connection
 // configuration.
 func (c *connection) setGenerationNumber() {
@@ -142,6 +137,39 @@ func (c *connection) hasGenerationNumber() bool {
 	return c.desc.LoadBalanced()
 }
 
+func configureTLS(ctx context.Context,
+	tlsConnSource tlsConnectionSource,
+	nc net.Conn,
+	addr address.Address,
+	config *tls.Config,
+	ocspOpts *ocsp.VerifyOptions,
+) (net.Conn, error) {
+	// Ensure config.ServerName is always set for SNI.
+	if config.ServerName == "" {
+		hostname := addr.String()
+		colonPos := strings.LastIndex(hostname, ":")
+		if colonPos == -1 {
+			colonPos = len(hostname)
+		}
+
+		hostname = hostname[:colonPos]
+		config.ServerName = hostname
+	}
+
+	client := tlsConnSource.Client(nc, config)
+	if err := clientHandshake(ctx, client); err != nil {
+		return nil, err
+	}
+
+	// Only do OCSP verification if TLS verification is requested.
+	if !config.InsecureSkipVerify {
+		if ocspErr := ocsp.Verify(ctx, client.ConnectionState(), ocspOpts); ocspErr != nil {
+			return nil, ocspErr
+		}
+	}
+	return client, nil
+}
+
 // connect handles the I/O for a connection. It will dial, configure TLS, and perform initialization
 // handshakes. All errors returned by connect are considered "before the handshake completes" and
 // must be handled by calling the appropriate SDAM handshake error handler.
@@ -317,6 +345,10 @@ func (c *connection) closeConnectContext() {
 	}
 }
 
+func (c *connection) cancellationListenerCallback() {
+	_ = c.close()
+}
+
 func transformNetworkError(ctx context.Context, originalError error, contextDeadlineUsed bool) error {
 	if originalError == nil {
 		return nil
@@ -339,10 +371,6 @@ func transformNetworkError(ctx context.Context, originalError error, contextDead
 	return originalError
 }
 
-func (c *connection) cancellationListenerCallback() {
-	_ = c.close()
-}
-
 func (c *connection) writeWireMessage(ctx context.Context, wm []byte) error {
 	var err error
 	if atomic.LoadInt64(&c.state) != connConnected {
@@ -423,15 +451,10 @@ func (c *connection) readWireMessage(ctx context.Context) ([]byte, error) {
 
 	dst, errMsg, err := c.read(ctx)
 	if err != nil {
-		if nerr := net.Error(nil); errors.As(err, &nerr) && nerr.Timeout() && csot.IsTimeoutContext(ctx) {
-			// If the error was a timeout error and CSOT is enabled, instead of
-			// closing the connection mark it as awaiting response so the pool
-			// can read the response before making it available to other
-			// operations.
-			c.awaitingResponse = true
-		} else {
-			// Otherwise, use the pre-CSOT behavior and close the connection
-			// because we don't know if there are other bytes left to read.
+		if c.awaitRemainingBytes == nil {
+			// If the connection was not marked as awaiting response, use the
+			// pre-CSOT behavior and close the connection because we don't know
+			// if there are other bytes left to read.
 			c.close()
 		}
 		message := errMsg
@@ -448,6 +471,26 @@ func (c *connection) readWireMessage(ctx context.Context) ([]byte, error) {
 	return dst, nil
 }
 
+func (c *connection) parseWmSizeBytes(wmSizeBytes [4]byte) (int32, error) {
+	// read the length as an int32
+	size := int32(binary.LittleEndian.Uint32(wmSizeBytes[:]))
+
+	if size < 4 {
+		return 0, fmt.Errorf("malformed message length: %d", size)
+	}
+	// In the case of a hello response where MaxMessageSize has not yet been set, use the hard-coded
+	// defaultMaxMessageSize instead.
+	maxMessageSize := c.desc.MaxMessageSize
+	if maxMessageSize == 0 {
+		maxMessageSize = defaultMaxMessageSize
+	}
+	if uint32(size) > maxMessageSize {
+		return 0, errResponseTooLarge
+	}
+
+	return size, nil
+}
+
 func (c *connection) read(ctx context.Context) (bytesRead []byte, errMsg string, err error) {
 	go c.cancellationListener.Listen(ctx, c.cancellationListenerCallback)
 	defer func() {
@@ -461,36 +504,43 @@ func (c *connection) read(ctx context.Context) (bytesRead []byte, errMsg string,
 		}
 	}()
 
+	isCSOTTimeout := func(err error) bool {
+		// If the error was a timeout error and CSOT is enabled, instead of
+		// closing the connection mark it as awaiting response so the pool
+		// can read the response before making it available to other
+		// operations.
+		nerr := net.Error(nil)
+		return errors.As(err, &nerr) && nerr.Timeout() && csot.IsTimeoutContext(ctx)
+	}
+
 	// We use an array here because it only costs 4 bytes on the stack and means we'll only need to
 	// reslice dst once instead of twice.
 	var sizeBuf [4]byte
 
 	// We do a ReadFull into an array here instead of doing an opportunistic ReadAtLeast into dst
 	// because there might be more than one wire message waiting to be read, for example when
 	// reading messages from an exhaust cursor.
-	_, err = io.ReadFull(c.nc, sizeBuf[:])
+	n, err := io.ReadFull(c.nc, sizeBuf[:])
 	if err != nil {
+		if l := int32(n); l == 0 && isCSOTTimeout(err) {
+			c.awaitRemainingBytes = &l
+		}
 		return nil, "incomplete read of message header", err
 	}
-
-	// read the length as an int32
-	size := (int32(sizeBuf[0])) | (int32(sizeBuf[1]) << 8) | (int32(sizeBuf[2]) << 16) | (int32(sizeBuf[3]) << 24)
-
-	// In the case of a hello response where MaxMessageSize has not yet been set, use the hard-coded
-	// defaultMaxMessageSize instead.
-	maxMessageSize := c.desc.MaxMessageSize
-	if maxMessageSize == 0 {
-		maxMessageSize = defaultMaxMessageSize
-	}
-	if uint32(size) > maxMessageSize {
-		return nil, errResponseTooLarge.Error(), errResponseTooLarge
+	size, err := c.parseWmSizeBytes(sizeBuf)
+	if err != nil {
+		return nil, err.Error(), err
 	}
 
 	dst := make([]byte, size)
 	copy(dst, sizeBuf[:])
 
-	_, err = io.ReadFull(c.nc, dst[4:])
+	n, err = io.ReadFull(c.nc, dst[4:])
 	if err != nil {
+		remainingBytes := size - 4 - int32(n)
+		if remainingBytes > 0 && isCSOTTimeout(err) {
+			c.awaitRemainingBytes = &remainingBytes
+		}
 		return dst, "incomplete read of full message", err
 	}
 
@@ -537,10 +587,6 @@ func (c *connection) setCanStream(canStream bool) {
 	c.canStream = canStream
 }
 
-func (c initConnection) supportsStreaming() bool {
-	return c.canStream
-}
-
 func (c *connection) setStreaming(streaming bool) {
 	c.currentlyStreaming = streaming
 }
@@ -554,6 +600,12 @@ func (c *connection) setSocketTimeout(timeout time.Duration) {
 	c.writeTimeout = timeout
 }
 
+// DriverConnectionID returns the driver connection ID.
+// TODO(GODRIVER-2824): change return type to int64.
+func (c *connection) DriverConnectionID() uint64 {
+	return c.driverConnectionID
+}
+
 func (c *connection) ID() string {
 	return c.id
 }
@@ -562,6 +614,14 @@ func (c *connection) ServerConnectionID() *int64 {
 	return c.serverConnectionID
 }
 
+func (c *connection) OIDCTokenGenID() uint64 {
+	return c.oidcTokenGenID
+}
+
+func (c *connection) SetOIDCTokenGenID(genID uint64) {
+	c.oidcTokenGenID = genID
+}
+
 // initConnection is an adapter used during connection initialization. It has the minimum
 // functionality necessary to implement the driver.Connection interface, which is required to pass a
 // *connection to a Handshaker.
@@ -599,7 +659,7 @@ func (c initConnection) CurrentlyStreaming() bool {
 	return c.getCurrentlyStreaming()
 }
 func (c initConnection) SupportsStreaming() bool {
-	return c.supportsStreaming()
+	return c.canStream
 }
 
 // Connection implements the driver.Connection interface to allow reading and writing wire
@@ -833,39 +893,6 @@ func (c *Connection) DriverConnectionID() uint64 {
 	return c.connection.DriverConnectionID()
 }
 
-func configureTLS(ctx context.Context,
-	tlsConnSource tlsConnectionSource,
-	nc net.Conn,
-	addr address.Address,
-	config *tls.Config,
-	ocspOpts *ocsp.VerifyOptions,
-) (net.Conn, error) {
-	// Ensure config.ServerName is always set for SNI.
-	if config.ServerName == "" {
-		hostname := addr.String()
-		colonPos := strings.LastIndex(hostname, ":")
-		if colonPos == -1 {
-			colonPos = len(hostname)
-		}
-
-		hostname = hostname[:colonPos]
-		config.ServerName = hostname
-	}
-
-	client := tlsConnSource.Client(nc, config)
-	if err := clientHandshake(ctx, client); err != nil {
-		return nil, err
-	}
-
-	// Only do OCSP verification if TLS verification is requested.
-	if !config.InsecureSkipVerify {
-		if ocspErr := ocsp.Verify(ctx, client.ConnectionState(), ocspOpts); ocspErr != nil {
-			return nil, ocspErr
-		}
-	}
-	return client, nil
-}
-
 // OIDCTokenGenID returns the OIDC token generation ID.
 func (c *Connection) OIDCTokenGenID() uint64 {
 	return c.oidcTokenGenID
@@ -919,11 +946,3 @@ func (c *cancellListener) StopListening() bool {
 	c.done <- struct{}{}
 	return c.aborted
 }
-
-func (c *connection) OIDCTokenGenID() uint64 {
-	return c.oidcTokenGenID
-}
-
-func (c *connection) SetOIDCTokenGenID(genID uint64) {
-	c.oidcTokenGenID = genID
-}

x/mongo/driver/topology/connection_test.go

@@ -546,6 +546,23 @@ func TestConnection(t *testing.T) {
 					}
 					listener.assertCalledOnce(t)
 				})
+				t.Run("size too small errors", func(t *testing.T) {
+					err := errors.New("malformed message length: 3")
+					tnc := &testNetConn{readerr: err, buf: []byte{0x03, 0x00, 0x00, 0x00}}
+					conn := &connection{id: "foobar", nc: tnc, state: connConnected}
+					listener := newTestCancellationListener(false)
+					conn.cancellationListener = listener
+
+					want := ConnectionError{ConnectionID: "foobar", Wrapped: err, message: err.Error()}
+					_, got := conn.readWireMessage(context.Background())
+					if !cmp.Equal(got, want, cmp.Comparer(compareErrors)) {
+						t.Errorf("errors do not match. got %v; want %v", got, want)
+					}
+					if !tnc.closed {
+						t.Errorf("failed to closeConnection net.Conn after error writing bytes.")
+					}
+					listener.assertCalledOnce(t)
+				})
 				t.Run("full message read errors", func(t *testing.T) {
 					err := errors.New("Read error")
 					tnc := &testNetConn{readerr: err, buf: []byte{0x11, 0x00, 0x00, 0x00}}