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Support port forwarding for privileged ports (1-1023)
On macOS, listening on 127.0.0.1:80 requires root while 0.0.0.0:80 does not require root. For such ports, the hostagent launches "pseudoloopback" forwarder that listens on 0.0.0.0:80 but rejects connections from non-loopback src IP. Signed-off-by: Akihiro Suda <akihiro.suda.cz@hco.ntt.co.jp>
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,158 @@ | ||
| package hostagent | ||
|
|
||
| import ( | ||
| "context" | ||
| "fmt" | ||
| "net" | ||
| "os" | ||
| "path/filepath" | ||
| "strconv" | ||
| "sync" | ||
|
|
||
| "github.com/lima-vm/sshocker/pkg/ssh" | ||
| "github.com/norouter/norouter/pkg/agent/bicopy" | ||
| "github.com/sirupsen/logrus" | ||
| ) | ||
|
|
||
| func forwardTCP(ctx context.Context, sshConfig *ssh.SSHConfig, port int, local, remote string, cancel bool) error { | ||
| localIPStr, localPortStr, err := net.SplitHostPort(local) | ||
| if err != nil { | ||
| return err | ||
| } | ||
| localIP := net.ParseIP(localIPStr) | ||
| localPort, err := strconv.Atoi(localPortStr) | ||
| if err != nil { | ||
| return err | ||
| } | ||
|
|
||
| if !net.ParseIP("127.0.0.1").Equal(localIP) || localPort >= 1024 { | ||
| return forwardSSH(ctx, sshConfig, port, local, remote, cancel) | ||
| } | ||
|
|
||
| // on macOS, listening on 127.0.0.1:80 requires root while 0.0.0.0:80 does not require root. | ||
| // https://twitter.com/_AkihiroSuda_/status/1403403845842075648 | ||
| // | ||
| // We use "pseudoloopback" forwarder that listens on 0.0.0.0:80 but rejects connections from non-loopback src IP. | ||
| logrus.Debugf("using pseudoloopback port forwarder for %q", local) | ||
|
|
||
| if cancel { | ||
| pseudoLoopbackForwardersMu.Lock() | ||
| plf, ok := pseudoLoopbackForwarders[local] | ||
| pseudoLoopbackForwardersMu.Unlock() | ||
| if ok { | ||
| localUnix := plf.unixAddr.Name | ||
| _ = plf.Close() | ||
| pseudoLoopbackForwardersMu.Lock() | ||
| delete(pseudoLoopbackForwarders, local) | ||
| pseudoLoopbackForwardersMu.Unlock() | ||
| if err := forwardSSH(ctx, sshConfig, port, localUnix, remote, cancel); err != nil { | ||
| return err | ||
| } | ||
| } | ||
| return nil | ||
| } | ||
|
|
||
| localUnixDir, err := os.MkdirTemp("/tmp", fmt.Sprintf("lima-psl-%s-%d-", localIP, localPort)) | ||
| if err != nil { | ||
| return err | ||
| } | ||
| localUnix := filepath.Join(localUnixDir, "sock") | ||
| if err := forwardSSH(ctx, sshConfig, port, localUnix, remote, cancel); err != nil { | ||
| _ = os.RemoveAll(localUnixDir) | ||
| return err | ||
| } | ||
| plf, err := newPseudoLoopbackForwarder(localPort, localUnix) | ||
| if err != nil { | ||
| _ = os.RemoveAll(localUnixDir) | ||
| return err | ||
| } | ||
| plf.onClose = func() error { | ||
| return os.RemoveAll(localUnixDir) | ||
| } | ||
| pseudoLoopbackForwardersMu.Lock() | ||
| pseudoLoopbackForwarders[local] = plf | ||
| pseudoLoopbackForwardersMu.Unlock() | ||
| go func() { | ||
| if plfErr := plf.Serve(); plfErr != nil { | ||
| logrus.WithError(plfErr).Warning("pseudoloopback forwarder crashed") | ||
| } | ||
| }() | ||
| return nil | ||
| } | ||
|
|
||
| var ( | ||
| pseudoLoopbackForwarders = make(map[string]*pseudoLoopbackForwarder) | ||
| pseudoLoopbackForwardersMu sync.Mutex | ||
| ) | ||
|
|
||
| type pseudoLoopbackForwarder struct { | ||
| ln *net.TCPListener | ||
| unixAddr *net.UnixAddr | ||
| onClose func() error | ||
| } | ||
|
|
||
| func newPseudoLoopbackForwarder(localPort int, unixSock string) (*pseudoLoopbackForwarder, error) { | ||
| unixAddr, err := net.ResolveUnixAddr("unix", unixSock) | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
|
|
||
| lnAddr, err := net.ResolveTCPAddr("tcp4", fmt.Sprintf("0.0.0.0:%d", localPort)) | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
| ln, err := net.ListenTCP("tcp4", lnAddr) | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
|
|
||
| plf := &pseudoLoopbackForwarder{ | ||
| ln: ln, | ||
| unixAddr: unixAddr, | ||
| } | ||
|
|
||
| return plf, nil | ||
| } | ||
|
|
||
| func (plf *pseudoLoopbackForwarder) Serve() error { | ||
| defer plf.ln.Close() | ||
| for { | ||
| ac, err := plf.ln.AcceptTCP() | ||
| if err != nil { | ||
| return err | ||
| } | ||
| remoteAddr := ac.RemoteAddr().String() // ip:port | ||
| remoteAddrIP, _, err := net.SplitHostPort(remoteAddr) | ||
| if err != nil { | ||
| logrus.WithError(err).Debugf("pseudoloopback forwarder: rejecting non-loopback remoteAddr %q (unparsable)", remoteAddr) | ||
| ac.Close() | ||
| continue | ||
| } | ||
| if remoteAddrIP != "127.0.0.1" { | ||
| logrus.WithError(err).Debugf("pseudoloopback forwarder: rejecting non-loopback remoteAddr %q", remoteAddr) | ||
| ac.Close() | ||
| continue | ||
| } | ||
| go func(ac *net.TCPConn) { | ||
| if fErr := plf.forward(ac); fErr != nil { | ||
| logrus.Error(fErr) | ||
| } | ||
| }(ac) | ||
| } | ||
| } | ||
|
|
||
| func (plf *pseudoLoopbackForwarder) forward(ac *net.TCPConn) error { | ||
| defer ac.Close() | ||
| unixConn, err := net.DialUnix("unix", nil, plf.unixAddr) | ||
| if err != nil { | ||
| return err | ||
| } | ||
| defer unixConn.Close() | ||
| bicopy.Bicopy(ac, unixConn, nil) | ||
| return nil | ||
| } | ||
|
|
||
| func (plf *pseudoLoopbackForwarder) Close() error { | ||
| _ = plf.ln.Close() | ||
| return plf.onClose() | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,14 @@ | ||
| //go:build !darwin | ||
| // +build !darwin | ||
|
|
||
| package hostagent | ||
|
|
||
| import ( | ||
| "context" | ||
|
|
||
| "github.com/lima-vm/sshocker/pkg/ssh" | ||
| ) | ||
|
|
||
| func forwardTCP(ctx context.Context, sshConfig *ssh.SSHConfig, port int, local, remote string, cancel bool) error { | ||
| return forwardSSH(ctx, sshConfig, port, local, remote, cancel) | ||
| } |
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