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tailscale/tempfork/gliderlabs/ssh/ssh.go

153 lines
5.0 KiB
Go

package ssh
import (
"crypto/subtle"
"net"
gossh "github.com/tailscale/golang-x-crypto/ssh"
)
type Signal string
// POSIX signals as listed in RFC 4254 Section 6.10.
const (
SIGABRT Signal = "ABRT"
SIGALRM Signal = "ALRM"
SIGFPE Signal = "FPE"
SIGHUP Signal = "HUP"
SIGILL Signal = "ILL"
SIGINT Signal = "INT"
SIGKILL Signal = "KILL"
SIGPIPE Signal = "PIPE"
SIGQUIT Signal = "QUIT"
SIGSEGV Signal = "SEGV"
SIGTERM Signal = "TERM"
SIGUSR1 Signal = "USR1"
SIGUSR2 Signal = "USR2"
)
// DefaultHandler is the default Handler used by Serve.
var DefaultHandler Handler
// Option is a functional option handler for Server.
type Option func(*Server) error
// Handler is a callback for handling established SSH sessions.
type Handler func(Session)
// PublicKeyHandler is a callback for performing public key authentication.
type PublicKeyHandler func(ctx Context, key PublicKey) error
// PasswordHandler is a callback for performing password authentication.
type PasswordHandler func(ctx Context, password string) bool
// KeyboardInteractiveHandler is a callback for performing keyboard-interactive authentication.
type KeyboardInteractiveHandler func(ctx Context, challenger gossh.KeyboardInteractiveChallenge) bool
// PtyCallback is a hook for allowing PTY sessions.
type PtyCallback func(ctx Context, pty Pty) bool
// SessionRequestCallback is a callback for allowing or denying SSH sessions.
type SessionRequestCallback func(sess Session, requestType string) bool
// ConnCallback is a hook for new connections before handling.
// It allows wrapping for timeouts and limiting by returning
// the net.Conn that will be used as the underlying connection.
type ConnCallback func(ctx Context, conn net.Conn) net.Conn
// LocalPortForwardingCallback is a hook for allowing port forwarding
type LocalPortForwardingCallback func(ctx Context, destinationHost string, destinationPort uint32) bool
// ReversePortForwardingCallback is a hook for allowing reverse port forwarding
type ReversePortForwardingCallback func(ctx Context, bindHost string, bindPort uint32) bool
// ServerConfigCallback is a hook for creating custom default server configs
type ServerConfigCallback func(ctx Context) *gossh.ServerConfig
// ConnectionFailedCallback is a hook for reporting failed connections
// Please note: the net.Conn is likely to be closed at this point
type ConnectionFailedCallback func(conn net.Conn, err error)
// Window represents the size of a PTY window.
//
// See https://datatracker.ietf.org/doc/html/rfc4254#section-6.2
//
// Zero dimension parameters MUST be ignored. The character/row dimensions
// override the pixel dimensions (when nonzero). Pixel dimensions refer
// to the drawable area of the window.
type Window struct {
// Width is the number of columns.
// It overrides WidthPixels.
Width int
// Height is the number of rows.
// It overrides HeightPixels.
Height int
// WidthPixels is the drawable width of the window, in pixels.
WidthPixels int
// HeightPixels is the drawable height of the window, in pixels.
HeightPixels int
}
// Pty represents a PTY request and configuration.
type Pty struct {
// Term is the TERM environment variable value.
Term string
// Window is the Window sent as part of the pty-req.
Window Window
// Modes represent a mapping of Terminal Mode opcode to value as it was
// requested by the client as part of the pty-req. These are outlined as
// part of https://datatracker.ietf.org/doc/html/rfc4254#section-8.
//
// The opcodes are defined as constants in github.com/tailscale/golang-x-crypto/ssh (VINTR,VQUIT,etc.).
// Boolean opcodes have values 0 or 1.
Modes gossh.TerminalModes
}
// Serve accepts incoming SSH connections on the listener l, creating a new
// connection goroutine for each. The connection goroutines read requests and
// then calls handler to handle sessions. Handler is typically nil, in which
// case the DefaultHandler is used.
func Serve(l net.Listener, handler Handler, options ...Option) error {
srv := &Server{Handler: handler}
for _, option := range options {
if err := srv.SetOption(option); err != nil {
return err
}
}
return srv.Serve(l)
}
// ListenAndServe listens on the TCP network address addr and then calls Serve
// with handler to handle sessions on incoming connections. Handler is typically
// nil, in which case the DefaultHandler is used.
func ListenAndServe(addr string, handler Handler, options ...Option) error {
srv := &Server{Addr: addr, Handler: handler}
for _, option := range options {
if err := srv.SetOption(option); err != nil {
return err
}
}
return srv.ListenAndServe()
}
// Handle registers the handler as the DefaultHandler.
func Handle(handler Handler) {
DefaultHandler = handler
}
// KeysEqual is constant time compare of the keys to avoid timing attacks.
func KeysEqual(ak, bk PublicKey) bool {
//avoid panic if one of the keys is nil, return false instead
if ak == nil || bk == nil {
return false
}
a := ak.Marshal()
b := bk.Marshal()
return (len(a) == len(b) && subtle.ConstantTimeCompare(a, b) == 1)
}