1 files changed, 314 insertions, 0 deletions
diff --git a/libpod/oci_conmon_attach_linux.go b/libpod/oci_conmon_attach_linux.go
new file mode 100644
index 000000000..aa55aa6f5
--- /dev/null
+++ b/libpod/oci_conmon_attach_linux.go
@@ -0,0 +1,314 @@
+//go:build linux
+// +build linux
+
+package libpod
+
+import (
+	"errors"
+	"fmt"
+	"io"
+	"net"
+	"os"
+	"path/filepath"
+	"syscall"
+
+	"github.com/containers/common/pkg/config"
+	"github.com/containers/common/pkg/resize"
+	"github.com/containers/common/pkg/util"
+	"github.com/containers/podman/v4/libpod/define"
+	"github.com/containers/podman/v4/pkg/errorhandling"
+	"github.com/moby/term"
+	"github.com/sirupsen/logrus"
+	"golang.org/x/sys/unix"
+)
+
+/* Sync with stdpipe_t in conmon.c */
+const (
+	AttachPipeStdin  = 1
+	AttachPipeStdout = 2
+	AttachPipeStderr = 3
+)
+
+func openUnixSocket(path string) (*net.UnixConn, error) {
+	fd, err := unix.Open(path, unix.O_PATH, 0)
+	if err != nil {
+		return nil, err
+	}
+	defer unix.Close(fd)
+	return net.DialUnix("unixpacket", nil, &net.UnixAddr{Name: fmt.Sprintf("/proc/self/fd/%d", fd), Net: "unixpacket"})
+}
+
+// Attach to the given container.
+// Does not check if state is appropriate.
+// started is only required if startContainer is true.
+func (r *ConmonOCIRuntime) Attach(c *Container, params *AttachOptions) error {
+	passthrough := c.LogDriver() == define.PassthroughLogging
+
+	if params == nil || params.Streams == nil {
+		return fmt.Errorf("must provide parameters to Attach: %w", define.ErrInternal)
+	}
+
+	if !params.Streams.AttachOutput && !params.Streams.AttachError && !params.Streams.AttachInput && !passthrough {
+		return fmt.Errorf("must provide at least one stream to attach to: %w", define.ErrInvalidArg)
+	}
+	if params.Start && params.Started == nil {
+		return fmt.Errorf("started chan not passed when startContainer set: %w", define.ErrInternal)
+	}
+
+	keys := config.DefaultDetachKeys
+	if params.DetachKeys != nil {
+		keys = *params.DetachKeys
+	}
+
+	detachKeys, err := processDetachKeys(keys)
+	if err != nil {
+		return err
+	}
+
+	var conn *net.UnixConn
+	if !passthrough {
+		logrus.Debugf("Attaching to container %s", c.ID())
+
+		// If we have a resize, do it.
+		if params.InitialSize != nil {
+			if err := r.AttachResize(c, *params.InitialSize); err != nil {
+				return err
+			}
+		}
+
+		attachSock, err := c.AttachSocketPath()
+		if err != nil {
+			return err
+		}
+
+		conn, err = openUnixSocket(attachSock)
+		if err != nil {
+			return fmt.Errorf("failed to connect to container's attach socket: %v: %w", attachSock, err)
+		}
+		defer func() {
+			if err := conn.Close(); err != nil {
+				logrus.Errorf("unable to close socket: %q", err)
+			}
+		}()
+	}
+
+	// If starting was requested, start the container and notify when that's
+	// done.
+	if params.Start {
+		if err := c.start(); err != nil {
+			return err
+		}
+		params.Started <- true
+	}
+
+	if passthrough {
+		return nil
+	}
+
+	receiveStdoutError, stdinDone := setupStdioChannels(params.Streams, conn, detachKeys)
+	if params.AttachReady != nil {
+		params.AttachReady <- true
+	}
+	return readStdio(conn, params.Streams, receiveStdoutError, stdinDone)
+}
+
+// Attach to the given container's exec session
+// attachFd and startFd must be open file descriptors
+// attachFd must be the output side of the fd. attachFd is used for two things:
+//  conmon will first send a nonce value across the pipe indicating it has set up its side of the console socket
+//    this ensures attachToExec gets all of the output of the called process
+//  conmon will then send the exit code of the exec process, or an error in the exec session
+// startFd must be the input side of the fd.
+// newSize resizes the tty to this size before the process is started, must be nil if the exec session has no tty
+//   conmon will wait to start the exec session until the parent process has set up the console socket.
+//   Once attachToExec successfully attaches to the console socket, the child conmon process responsible for calling runtime exec
+//     will read from the output side of start fd, thus learning to start the child process.
+// Thus, the order goes as follow:
+// 1. conmon parent process sets up its console socket. sends on attachFd
+// 2. attachToExec attaches to the console socket after reading on attachFd and resizes the tty
+// 3. child waits on startFd for attachToExec to attach to said console socket
+// 4. attachToExec sends on startFd, signalling it has attached to the socket and child is ready to go
+// 5. child receives on startFd, runs the runtime exec command
+// attachToExec is responsible for closing startFd and attachFd
+func (c *Container) attachToExec(streams *define.AttachStreams, keys *string, sessionID string, startFd, attachFd *os.File, newSize *resize.TerminalSize) error {
+	if !streams.AttachOutput && !streams.AttachError && !streams.AttachInput {
+		return fmt.Errorf("must provide at least one stream to attach to: %w", define.ErrInvalidArg)
+	}
+	if startFd == nil || attachFd == nil {
+		return fmt.Errorf("start sync pipe and attach sync pipe must be defined for exec attach: %w", define.ErrInvalidArg)
+	}
+
+	defer errorhandling.CloseQuiet(startFd)
+	defer errorhandling.CloseQuiet(attachFd)
+
+	detachString := config.DefaultDetachKeys
+	if keys != nil {
+		detachString = *keys
+	}
+	detachKeys, err := processDetachKeys(detachString)
+	if err != nil {
+		return err
+	}
+
+	logrus.Debugf("Attaching to container %s exec session %s", c.ID(), sessionID)
+
+	// set up the socket path, such that it is the correct length and location for exec
+	sockPath, err := c.execAttachSocketPath(sessionID)
+	if err != nil {
+		return err
+	}
+
+	// 2: read from attachFd that the parent process has set up the console socket
+	if _, err := readConmonPipeData(c.ociRuntime.Name(), attachFd, ""); err != nil {
+		return err
+	}
+
+	// resize before we start the container process
+	if newSize != nil {
+		err = c.ociRuntime.ExecAttachResize(c, sessionID, *newSize)
+		if err != nil {
+			logrus.Warnf("Resize failed: %v", err)
+		}
+	}
+
+	// 2: then attach
+	conn, err := openUnixSocket(sockPath)
+	if err != nil {
+		return fmt.Errorf("failed to connect to container's attach socket: %v: %w", sockPath, err)
+	}
+	defer func() {
+		if err := conn.Close(); err != nil {
+			logrus.Errorf("Unable to close socket: %q", err)
+		}
+	}()
+
+	// start listening on stdio of the process
+	receiveStdoutError, stdinDone := setupStdioChannels(streams, conn, detachKeys)
+
+	// 4: send start message to child
+	if err := writeConmonPipeData(startFd); err != nil {
+		return err
+	}
+
+	return readStdio(conn, streams, receiveStdoutError, stdinDone)
+}
+
+func processDetachKeys(keys string) ([]byte, error) {
+	// Check the validity of the provided keys first
+	if len(keys) == 0 {
+		return []byte{}, nil
+	}
+	detachKeys, err := term.ToBytes(keys)
+	if err != nil {
+		return nil, fmt.Errorf("invalid detach keys: %w", err)
+	}
+	return detachKeys, nil
+}
+
+func registerResizeFunc(r <-chan resize.TerminalSize, bundlePath string) {
+	resize.HandleResizing(r, func(size resize.TerminalSize) {
+		controlPath := filepath.Join(bundlePath, "ctl")
+		controlFile, err := os.OpenFile(controlPath, unix.O_WRONLY, 0)
+		if err != nil {
+			logrus.Debugf("Could not open ctl file: %v", err)
+			return
+		}
+		defer controlFile.Close()
+
+		logrus.Debugf("Received a resize event: %+v", size)
+		if _, err = fmt.Fprintf(controlFile, "%d %d %d\n", 1, size.Height, size.Width); err != nil {
+			logrus.Warnf("Failed to write to control file to resize terminal: %v", err)
+		}
+	})
+}
+
+func setupStdioChannels(streams *define.AttachStreams, conn *net.UnixConn, detachKeys []byte) (chan error, chan error) {
+	receiveStdoutError := make(chan error)
+	go func() {
+		receiveStdoutError <- redirectResponseToOutputStreams(streams.OutputStream, streams.ErrorStream, streams.AttachOutput, streams.AttachError, conn)
+	}()
+
+	stdinDone := make(chan error)
+	go func() {
+		var err error
+		if streams.AttachInput {
+			_, err = util.CopyDetachable(conn, streams.InputStream, detachKeys)
+		}
+		stdinDone <- err
+	}()
+
+	return receiveStdoutError, stdinDone
+}
+
+func redirectResponseToOutputStreams(outputStream, errorStream io.Writer, writeOutput, writeError bool, conn io.Reader) error {
+	var err error
+	buf := make([]byte, 8192+1) /* Sync with conmon STDIO_BUF_SIZE */
+	for {
+		nr, er := conn.Read(buf)
+		if nr > 0 {
+			var dst io.Writer
+			var doWrite bool
+			switch buf[0] {
+			case AttachPipeStdout:
+				dst = outputStream
+				doWrite = writeOutput
+			case AttachPipeStderr:
+				dst = errorStream
+				doWrite = writeError
+			default:
+				logrus.Infof("Received unexpected attach type %+d", buf[0])
+			}
+			if dst == nil {
+				return errors.New("output destination cannot be nil")
+			}
+
+			if doWrite {
+				nw, ew := dst.Write(buf[1:nr])
+				if ew != nil {
+					err = ew
+					break
+				}
+				if nr != nw+1 {
+					err = io.ErrShortWrite
+					break
+				}
+			}
+		}
+		if errors.Is(er, io.EOF) || errors.Is(er, syscall.ECONNRESET) {
+			break
+		}
+		if er != nil {
+			err = er
+			break
+		}
+	}
+	return err
+}
+
+func readStdio(conn *net.UnixConn, streams *define.AttachStreams, receiveStdoutError, stdinDone chan error) error {
+	var err error
+	select {
+	case err = <-receiveStdoutError:
+		if err := conn.CloseWrite(); err != nil {
+			logrus.Errorf("Failed to close stdin: %v", err)
+		}
+		return err
+	case err = <-stdinDone:
+		if err == define.ErrDetach {
+			if err := conn.CloseWrite(); err != nil {
+				logrus.Errorf("Failed to close stdin: %v", err)
+			}
+			return err
+		}
+		if err == nil {
+			// copy stdin is done, close it
+			if connErr := conn.CloseWrite(); connErr != nil {
+				logrus.Errorf("Unable to close conn: %v", connErr)
+			}
+		}
+		if streams.AttachOutput || streams.AttachError {
+			return <-receiveStdoutError
+		}
+	}
+	return nil
+}