Fix escape-keys by preserving input if invalid

Currently, using a custom detach key with an invalid sequence, eats a
part of the sequence, making it weird and difficult to enter some key
sequence.

This fixes by keeping the input read when trying to see if it's the key
sequence or not, and "writing" then is the key sequence is not the right
one, preserving the initial input.

Signed-off-by: Vincent Demeester <vincent@sbr.pm>

container/container.go

@@ -484,7 +484,9 @@ func copyEscapable(dst io.Writer, src io.ReadCloser, keys []byte) (written int64
 		nr, er := src.Read(buf)
 		if nr > 0 {
 			// ---- Docker addition
+			preservBuf := []byte{}
 			for i, key := range keys {
+				preservBuf = append(preservBuf, buf[0:nr]...)
 				if nr != 1 || buf[0] != key {
 					break
 				}
@@ -496,8 +498,15 @@ func copyEscapable(dst io.Writer, src io.ReadCloser, keys []byte) (written int64
 				}
 				nr, er = src.Read(buf)
 			}
-			// ---- End of docker
-			nw, ew := dst.Write(buf[0:nr])
+			var nw int
+			var ew error
+			if len(preservBuf) > 0 {
+				nw, ew = dst.Write(preservBuf)
+				nr = len(preservBuf)
+			} else {
+				// ---- End of docker
+				nw, ew = dst.Write(buf[0:nr])
+			}
 			if nw > 0 {
 				written += int64(nw)
 			}

integration-cli/docker_cli_run_unix_test.go

@@ -396,6 +396,55 @@ func (s *DockerSuite) TestRunAttachDetachKeysOverrideConfig(c *check.C) {
 	c.Assert(running, checker.Equals, "true", check.Commentf("expected container to still be running"))
 }
 
+func (s *DockerSuite) TestRunAttachInvalidDetachKeySequencePreserved(c *check.C) {
+	name := "attach-detach"
+	keyA := []byte{97}
+	keyB := []byte{98}
+
+	dockerCmd(c, "run", "--name", name, "-itd", "busybox", "cat")
+
+	cmd := exec.Command(dockerBinary, "attach", "--detach-keys='a,b,c'", name)
+	stdout, err := cmd.StdoutPipe()
+	if err != nil {
+		c.Fatal(err)
+	}
+	cpty, tty, err := pty.Open()
+	if err != nil {
+		c.Fatal(err)
+	}
+	defer cpty.Close()
+	cmd.Stdin = tty
+	if err := cmd.Start(); err != nil {
+		c.Fatal(err)
+	}
+	c.Assert(waitRun(name), check.IsNil)
+
+	// Invalid escape sequence aba, should print aba in output
+	if _, err := cpty.Write(keyA); err != nil {
+		c.Fatal(err)
+	}
+	time.Sleep(100 * time.Millisecond)
+	if _, err := cpty.Write(keyB); err != nil {
+		c.Fatal(err)
+	}
+	time.Sleep(100 * time.Millisecond)
+	if _, err := cpty.Write(keyA); err != nil {
+		c.Fatal(err)
+	}
+	time.Sleep(100 * time.Millisecond)
+	if _, err := cpty.Write([]byte("\n")); err != nil {
+		c.Fatal(err)
+	}
+
+	out, err := bufio.NewReader(stdout).ReadString('\n')
+	if err != nil {
+		c.Fatal(err)
+	}
+	if strings.TrimSpace(out) != "aba" {
+		c.Fatalf("expected 'aba', got %q", out)
+	}
+}
+
 // "test" should be printed
 func (s *DockerSuite) TestRunWithCPUQuota(c *check.C) {
 	testRequires(c, cpuCfsQuota)