Extract client behaviour outside the main (#90)

The client's main function now only prepares the transport connection. It then instantiates and manipulates a Client object. This can be used to automatize behaviours and potentially lead to easy ProxyJump implementation (as asked by #44).

* separate QUIC transport logic and user-auth/conversation logic

* use  of options and canonicalize hosts format

* known hosts: design hosts by their canonical representation

* do not log a non-zero exit status as an error

client/options.go

@@ -0,0 +1,70 @@
+package client
+
+import (
+	"fmt"
+	"net"
+)
+
+type Options struct {
+	username    string
+	hostname    string
+	port        int
+	urlPath     string
+	authMethods []interface{}
+}
+
+func NewOptions(username string, hostname string, port int, urlPath string, authMethods []interface{}) (*Options, error) {
+	if len(urlPath) == 0 || urlPath[0] != '/' {
+		urlPath = "/" + urlPath
+	}
+	return &Options{
+		username:    username,
+		hostname:    hostname,
+		port:        port,
+		urlPath:     urlPath,
+		authMethods: authMethods,
+	}, nil
+}
+
+func (o *Options) Username() string {
+	return o.username
+}
+
+func (o *Options) Hostname() string {
+	return o.hostname
+}
+
+// Returns the pair hostname:port in a valid URL format.
+// This means that an IPv6 will be written inside square brackets [].
+// examples: "127.0.0.1:443", "example.org:1234", "[::1]:22""
+func (o *Options) URLHostnamePort() string {
+	hostnameIsAnIP := net.ParseIP(o.hostname) != nil
+	if hostnameIsAnIP {
+		ip := net.ParseIP(o.hostname)
+		if ip.To4() == nil && ip.To16() != nil {
+			// enforce the square-bracketed notation for ipv6 UDP addresses
+			return fmt.Sprintf("[%s]:%d", o.hostname, o.port)
+		}
+	}
+	return fmt.Sprintf("%s:%d", o.hostname, o.port)
+}
+
+func (o *Options) Port() int {
+	return o.port
+}
+func (o *Options) UrlPath() string {
+	return o.urlPath
+}
+
+// Returns the canonical host representation used by SSH3.
+// The format is <urlhostnameport><path>
+// <urlhostnameport> is the host:port pair in the format returned by
+// URLHostnamePort()
+// <path> is the URL path, it always starts with a "/", it is therefore never empty.
+func (o *Options) CanonicalHostFormat() string {
+	return fmt.Sprintf("%s:%d%s", o.hostname, o.port, o.urlPath)
+}
+
+func (o *Options) AuthMethods() []interface{} {
+	return o.authMethods
+}

client/winsize/winsize.go

@@ -0,0 +1,18 @@
+//go:build !windows
+
+package winsize
+
+import (
+	"os"
+	"syscall"
+	"unsafe"
+)
+
+func GetWinsize(tty *os.File) (ws WindowSize, err error) {
+	_, _, errno := syscall.Syscall(syscall.SYS_IOCTL, uintptr(tty.Fd()), uintptr(syscall.TIOCGWINSZ),
+		uintptr(unsafe.Pointer(&ws)))
+	if errno != 0 {
+		err = errno
+	}
+	return ws, err
+}

cmd/ssh3/winsize/winsize_windows.go → client/winsize/winsize_windows.go

@@ -2,13 +2,16 @@
 
 package winsize
 
-import "os"
-import "golang.org/x/term"
+import (
+	"os"
 
-func GetWinsize() (ws WindowSize, err error) {
+	"golang.org/x/term"
+)
+
+func GetWinsize(tty *os.File) (ws WindowSize, err error) {
 	// for Windows, it is a bit more complicated to get the window size in pixels, so on rely
 	// on window size expressed in columns
-	width, height, err := term.GetSize(int(os.Stdout.Fd()))
+	width, height, err := term.GetSize(int(tty.Fd()))
 	if err != nil {
 		return ws, err
 	}

client.go → client_auth.go

@@ -31,6 +31,10 @@ func (m *OidcAuthMethod) OIDCConfig() *auth.OIDCConfig {
 	return m.config
 }
 
+func (m *OidcAuthMethod) DoPKCE() bool {
+	return m.doPKCE
+}
+
 type PrivkeyFileAuthMethod struct {
 	filename string
 }

cmd/ssh3-server/main.go

@@ -578,7 +578,7 @@ func newDataReq(user *unix_util.User, channel ssh3.Channel, request ssh3Messages
 func handleAuthAgentSocketConn(conn net.Conn, conversation *ssh3.Conversation) {
 	channel, err := conversation.OpenChannel("agent-connection", 30000, 10)
 	if err != nil {
-		log.Error().Msgf("could not open channel: %s", err.Error())
+		log.Error().Msgf("could not open channel from server: %s", err.Error())
 		return
 	}
 	go func() {