add ssh dialer

pkg/internal/util/ssh/conn.go

@@ -0,0 +1,24 @@
+package ssh
+
+import (
+	"net"
+
+	"golang.org/x/crypto/ssh"
+)
+
+// a dummy ssh client conn used by client connector
+type ClientConn struct {
+	net.Conn
+	client *ssh.Client
+}
+
+func NewClientConn(conn net.Conn, client *ssh.Client) net.Conn {
+	return &ClientConn{
+		Conn:   conn,
+		client: client,
+	}
+}
+
+func (c *ClientConn) Client() *ssh.Client {
+	return c.client
+}

pkg/internal/util/ssh/ssh.go

@@ -0,0 +1,46 @@
+package ssh
+
+import (
+	"fmt"
+
+	"github.com/go-gost/gost/pkg/auth"
+	"golang.org/x/crypto/ssh"
+)
+
+// PasswordCallbackFunc is a callback function used by SSH server.
+// It authenticates user using a password.
+type PasswordCallbackFunc func(conn ssh.ConnMetadata, password []byte) (*ssh.Permissions, error)
+
+func PasswordCallback(au auth.Authenticator) PasswordCallbackFunc {
+	if au == nil {
+		return nil
+	}
+	return func(conn ssh.ConnMetadata, password []byte) (*ssh.Permissions, error) {
+		if au.Authenticate(conn.User(), string(password)) {
+			return nil, nil
+		}
+		return nil, fmt.Errorf("password rejected for %s", conn.User())
+	}
+}
+
+// PublicKeyCallbackFunc is a callback function used by SSH server.
+// It offers a public key for authentication.
+type PublicKeyCallbackFunc func(c ssh.ConnMetadata, pubKey ssh.PublicKey) (*ssh.Permissions, error)
+
+func PublicKeyCallback(keys map[string]bool) PublicKeyCallbackFunc {
+	if len(keys) == 0 {
+		return nil
+	}
+
+	return func(c ssh.ConnMetadata, pubKey ssh.PublicKey) (*ssh.Permissions, error) {
+		if keys[string(pubKey.Marshal())] {
+			return &ssh.Permissions{
+				// Record the public key used for authentication.
+				Extensions: map[string]string{
+					"pubkey-fp": ssh.FingerprintSHA256(pubKey),
+				},
+			}, nil
+		}
+		return nil, fmt.Errorf("unknown public key for %q", c.User())
+	}
+}