fix rootless port forwarding with network dis-/connect

The rootlessport forwarder requires a child IP to be set. This must be a
valid ip in the container network namespace. The problem is that after a
network disconnect and connect the eth0 ip changed. Therefore the
packages are dropped since the source ip does no longer exists in the
netns.
One solution is to set the child IP to 127.0.0.1, however this is a
security problem. [1]

To fix this we have to recreate the ports after network connect and
disconnect. To make this work the rootlessport process exposes a socket
where podman network connect/disconnect connect to and send to new child
IP to rootlessport. The rootlessport process will remove all ports and
recreate them with the new correct child IP.

Also bump rootlesskit to v0.14.3 to fix a race with RemovePort().

Fixes #10052

[1] https://nvd.nist.gov/vuln/detail/CVE-2021-20199

Signed-off-by: Paul Holzinger <pholzing@redhat.com>

2 files changed, 102 insertions, 24 deletions

diff --git a/libpod/networking_linux.go b/libpod/networking_linux.go
index 0f3e03e06..8e9b5997c 100644
--- a/libpod/networking_linux.go
+++ b/libpod/networking_linux.go
@@ -1214,7 +1214,29 @@ func (c *Container) NetworkDisconnect(nameOrID, netName string, force bool) erro
 		}
 	}
 	c.state.NetworkStatus = tmpNetworkStatus
-	return c.save()
+	err = c.save()
+	if err != nil {
+		return err
+	}
+
+	// OCICNI will set the loopback adpter down on teardown so we should set it up again
+	err = c.state.NetNS.Do(func(_ ns.NetNS) error {
+		link, err := netlink.LinkByName("lo")
+		if err != nil {
+			return err
+		}
+		err = netlink.LinkSetUp(link)
+		return err
+	})
+	if err != nil {
+		logrus.Warnf("failed to set loopback adpter up in the container: %v", err)
+	}
+	// Reload ports when there are still connected networks, maybe we removed the network interface with the child ip.
+	// Reloading without connected networks does not make sense, so we can skip this step.
+	if rootless.IsRootless() && len(tmpNetworkStatus) > 0 {
+		return c.reloadRootlessRLKPortMapping()
+	}
+	return nil
 }
 
 // ConnectNetwork connects a container to a given network
@@ -1306,7 +1328,16 @@ func (c *Container) NetworkConnect(nameOrID, netName string, aliases []string) e
 		networkStatus[index] = networkResults[0]
 		c.state.NetworkStatus = networkStatus
 	}
-	return c.save()
+	err = c.save()
+	if err != nil {
+		return err
+	}
+	// The first network needs a port reload to set the correct child ip for the rootlessport process.
+	// Adding a second network does not require a port reload because the child ip is still valid.
+	if rootless.IsRootless() && len(networks) == 0 {
+		return c.reloadRootlessRLKPortMapping()
+	}
+	return nil
 }
 
 // DisconnectContainerFromNetwork removes a container from its CNI network
diff --git a/libpod/networking_slirp4netns.go b/libpod/networking_slirp4netns.go
index 410b377ec..5858364ff 100644
--- a/libpod/networking_slirp4netns.go
+++ b/libpod/networking_slirp4netns.go
@@ -17,6 +17,7 @@ import (
 	"time"
 
 	"github.com/containers/podman/v3/pkg/errorhandling"
+	"github.com/containers/podman/v3/pkg/rootless"
 	"github.com/containers/podman/v3/pkg/rootlessport"
 	"github.com/containers/podman/v3/pkg/servicereaper"
 	"github.com/pkg/errors"
@@ -466,29 +467,16 @@ func (r *Runtime) setupRootlessPortMappingViaRLK(ctr *Container, netnsPath strin
 		}
 	}
 
-	slirp4netnsIP, err := GetSlirp4netnsIP(ctr.slirp4netnsSubnet)
-	if err != nil {
-		return errors.Wrapf(err, "failed to get slirp4ns ip")
-	}
-	childIP := slirp4netnsIP.String()
-outer:
-	for _, r := range ctr.state.NetworkStatus {
-		for _, i := range r.IPs {
-			ipv4 := i.Address.IP.To4()
-			if ipv4 != nil {
-				childIP = ipv4.String()
-				break outer
-			}
-		}
-	}
-
+	childIP := getRootlessPortChildIP(ctr)
 	cfg := rootlessport.Config{
-		Mappings:  ctr.config.PortMappings,
-		NetNSPath: netnsPath,
-		ExitFD:    3,
-		ReadyFD:   4,
-		TmpDir:    ctr.runtime.config.Engine.TmpDir,
-		ChildIP:   childIP,
+		Mappings:    ctr.config.PortMappings,
+		NetNSPath:   netnsPath,
+		ExitFD:      3,
+		ReadyFD:     4,
+		TmpDir:      ctr.runtime.config.Engine.TmpDir,
+		ChildIP:     childIP,
+		ContainerID: ctr.config.ID,
+		RootlessCNI: ctr.config.NetMode.IsBridge() && rootless.IsRootless(),
 	}
 	cfgJSON, err := json.Marshal(cfg)
 	if err != nil {
@@ -617,3 +605,62 @@ func (r *Runtime) setupRootlessPortMappingViaSlirp(ctr *Container, cmd *exec.Cmd
 	logrus.Debug("slirp4netns port-forwarding setup via add_hostfwd is ready")
 	return nil
 }
+
+func getRootlessPortChildIP(c *Container) string {
+	if c.config.NetMode.IsSlirp4netns() {
+		slirp4netnsIP, err := GetSlirp4netnsIP(c.slirp4netnsSubnet)
+		if err != nil {
+			return ""
+		}
+		return slirp4netnsIP.String()
+	}
+
+	for _, r := range c.state.NetworkStatus {
+		for _, i := range r.IPs {
+			ipv4 := i.Address.IP.To4()
+			if ipv4 != nil {
+				return ipv4.String()
+			}
+		}
+	}
+	return ""
+}
+
+// reloadRootlessRLKPortMapping will trigger a reload for the port mappings in the rootlessport process.
+// This should only be called by network connect/disconnect and only as rootless.
+func (c *Container) reloadRootlessRLKPortMapping() error {
+	childIP := getRootlessPortChildIP(c)
+	logrus.Debugf("reloading rootless ports for container %s, childIP is %s", c.config.ID, childIP)
+
+	var conn net.Conn
+	var err error
+	// try three times to connect to the socket, maybe it is not ready yet
+	for i := 0; i < 3; i++ {
+		conn, err = net.Dial("unix", filepath.Join(c.runtime.config.Engine.TmpDir, "rp", c.config.ID))
+		if err == nil {
+			break
+		}
+		time.Sleep(250 * time.Millisecond)
+	}
+	if err != nil {
+		// This is not a hard error for backwards compatibility. A container started
+		// with an old version did not created the rootlessport socket.
+		logrus.Warnf("Could not reload rootless port mappings, port forwarding may no longer work correctly: %v", err)
+		return nil
+	}
+	defer conn.Close()
+	enc := json.NewEncoder(conn)
+	err = enc.Encode(childIP)
+	if err != nil {
+		return errors.Wrap(err, "port reloading failed")
+	}
+	b, err := ioutil.ReadAll(conn)
+	if err != nil {
+		return errors.Wrap(err, "port reloading failed")
+	}
+	data := string(b)
+	if data != "OK" {
+		return errors.Errorf("port reloading failed: %s", data)
+	}
+	return nil
+}