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listen.go
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listen.go
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package sshego
import (
"fmt"
"log"
"net"
"sync"
"time"
"github.com/glycerine/idem"
"golang.org/x/crypto/ssh"
)
// BasicServer configures a simple embedded sshd server
// that only expects RSA key (or other) based authentication,
// and doesn't expect TOTP or passphase. This makes
// it suitable for using with unattended systems / to
// replace a TLS server.
type BasicServer struct {
cfg *SshegoConfig
}
// NewBasicServer in
// listen.go provides net.Listen() compatibility
// for running an embedded sshd. It refactors
// server.go's Start() into Listen() and Accept().
func NewBasicServer(cfg *SshegoConfig) *BasicServer {
cfg.NewEsshd()
return &BasicServer{cfg: cfg}
}
// Close closes bind to the port that the server has.
func (b *BasicServer) Close() error {
// In case we haven't yet actually started, close Done too.
// Multiple Close() calls on an idem.Halter are fine.
b.cfg.Esshd.Halt.Done.Close()
return b.cfg.Esshd.Stop()
}
// Address satisfies the net.Addr interface, which
// BasicListener.Addr() returns.
type BasicAddress struct {
addr string
}
// Network returns the name of the network, "sshego"
func (a *BasicAddress) Network() string {
return "sshego"
}
// String returns the string form of the address.
func (a *BasicAddress) String() string {
return a.addr
}
// BasicListener satifies the net.Listener interface
type BasicListener struct {
bs *BasicServer
addr BasicAddress
esshd *Esshd
dom string
lsn net.Listener
attempt uint64
halt idem.Halter
mut sync.Mutex
}
// Addr returns the listener's network address.
func (b *BasicListener) Addr() net.Addr {
return &BasicAddress{
addr: b.bs.cfg.EmbeddedSSHd.Addr,
}
}
// Close closes the listener.
// Any blocked Accept operations will be unblocked and return errors.
func (b *BasicListener) Close() error {
// in case we haven't yet actually started, close the Done
// channel too.
// global shutdown: works but not what we want!
// b.bs.cfg.Esshd.Halt.Done.Close()
// return b.bs.cfg.Esshd.Stop()
b.halt.Done.Close()
b.halt.ReqStop.Close()
return nil
}
// Listen announces on the local network address laddr.
// The syntax of laddr is "host:port", like "127.0.0.1:2222".
// We listen on a TCP port.
func (bs *BasicServer) Listen(laddr string) (*BasicListener, error) {
bs.cfg.EmbeddedSSHd.Addr = laddr
err := bs.cfg.EmbeddedSSHd.ParseAddr()
if err != nil {
return nil, err
}
return bs.cfg.Esshd.Listen(bs)
}
// Essh add-on methods
// Listen and Accept support BasicServer functionality.
// Together, Listen() then Accept() replace Start().
func (e *Esshd) Listen(bs *BasicServer) (*BasicListener, error) {
log.Printf("Esshd.Listen() called. %s", SourceVersion())
p("about to listen on %v", e.cfg.EmbeddedSSHd.Addr)
// Once a ServerConfig has been configured, connections can be
// accepted.
domain := "tcp"
if e.cfg.EmbeddedSSHd.UnixDomainPath != "" {
domain = "unix"
}
p("info: Essh.Listen() in listen.go: listening on "+
"domain '%s', addr: '%s'", domain, e.cfg.EmbeddedSSHd.Addr)
listener, err := net.Listen(domain, e.cfg.EmbeddedSSHd.Addr)
if err != nil {
return nil, fmt.Errorf("failed to listen for connection on %v: %v",
e.cfg.EmbeddedSSHd.Addr, err)
}
return &BasicListener{
bs: bs,
esshd: e,
dom: domain,
lsn: listener,
halt: *idem.NewHalter(),
}, nil
}
// Accept and Listen support BasicServer functionality.
// Accept waits for and returns the next connection to the listener.
func (b *BasicListener) Accept() (net.Conn, error) {
p("Accept for BasicListener called.")
e := b.esshd
// most of the auth state is per user, so it has
// to wait until we have a login and a
// username at hand.
a := NewAuthState(nil)
// we copy the host key here to avoid a data race later.
e.cfg.HostDb.saveMut.Lock()
a.HostKey = e.cfg.HostDb.HostSshSigner
e.cfg.HostDb.saveMut.Unlock()
// don't Close()! We may want to re-use this listener
// for another Accept().
// defer b.halt.Done.Close()
for {
// TODO: fail2ban: notice bad login IPs and if too many, block the IP.
timeoutMillisec := 1000
err := b.lsn.(*net.TCPListener).
SetDeadline(time.Now().
Add(time.Duration(timeoutMillisec) * time.Millisecond))
panicOn(err)
nConn, err := b.lsn.Accept()
p("back from Accept, err = %v", err)
if err != nil {
// simple timeout, check if stop requested
// 'accept tcp 127.0.0.1:54796: i/o timeout'
// p("simple timeout err: '%v'", err)
select {
case <-e.Halt.ReqStop.Chan:
p("e.Halt.ReqStop detected")
return nil, fmt.Errorf("shutting down")
case <-b.halt.ReqStop.Chan:
p("b.halt.ReqStop detected")
return nil, fmt.Errorf("shutting down")
default:
// no stop request, keep looping
//p("not stop request, keep looping")
}
continue
}
p("info: Essh.Accept() in listen.go: accepted new connection on "+
"domain '%s', addr: '%s'", b.dom, e.cfg.EmbeddedSSHd.Addr)
attempt := NewPerAttempt(a, e.cfg)
attempt.SetupAuthRequirements()
// need to get the direct-tcp connection back directly.
ca := &ConnectionAlert{
PortOne: make(chan ssh.Channel),
ShutDown: b.esshd.Halt.ReqStop.Chan,
}
err = attempt.PerConnection(nConn, ca)
if err != nil {
return nil, err
}
select {
case <-b.halt.ReqStop.Chan:
return nil, fmt.Errorf("shutting down")
case <-b.esshd.Halt.ReqStop.Chan:
return nil, fmt.Errorf("shutting down")
case sshc := <-ca.PortOne:
return &withLocalAddr{sshc}, nil
}
} // end for
}
// withLocalAddr wraps an ssh.Channel to
// implements the net.Conn missing methods
type withLocalAddr struct {
ssh.Channel
}
func (w *withLocalAddr) LocalAddr() net.Addr {
panic("not implemented")
return &BasicAddress{}
}
func (w *withLocalAddr) RemoteAddr() net.Addr {
panic("not implemented")
return &BasicAddress{}
}
func (w *withLocalAddr) SetDeadline(t time.Time) error {
panic("not implemented")
return nil
}
func (w *withLocalAddr) SetReadDeadline(t time.Time) error {
panic("not implemented")
return nil
}
func (w *withLocalAddr) SetWriteDeadline(t time.Time) error {
panic("not implemented")
return nil
}