feat: allocate real pty

_examples/ssh-ptystart/main.go

@@ -0,0 +1,59 @@
+package main
+
+import (
+	"fmt"
+	"io"
+	"log"
+	"os"
+	"os/exec"
+	"runtime"
+	"time"
+
+	"github.com/charmbracelet/ssh"
+)
+
+func main() {
+	ssh.Handle(func(s ssh.Session) {
+		log.Printf("connected %s %s %q", s.User(), s.RemoteAddr(), s.RawCommand())
+		defer log.Printf("disconnected %s %s", s.User(), s.RemoteAddr())
+
+		pty, _, ok := s.Pty()
+		if !ok {
+			io.WriteString(s, "No PTY requested.\n")
+			s.Exit(1)
+			return
+		}
+
+		name := "bash"
+		if runtime.GOOS == "windows" {
+			name = "powershell.exe"
+		}
+		cmd := exec.Command(name)
+		cmd.Env = append(os.Environ(), "SSH_TTY="+pty.Name(), fmt.Sprintf("TERM=%s", pty.Term))
+		if err := pty.Start(cmd); err != nil {
+			fmt.Fprintln(s, err.Error())
+			s.Exit(1)
+			return
+		}
+
+		if runtime.GOOS == "windows" {
+			// ProcessState gets populated by pty.Start waiting on the process
+			// to exit.
+			for cmd.ProcessState == nil {
+				time.Sleep(100 * time.Millisecond)
+			}
+
+			s.Exit(cmd.ProcessState.ExitCode())
+		} else {
+			if err := cmd.Wait(); err != nil {
+				fmt.Fprintln(s, err)
+				s.Exit(cmd.ProcessState.ExitCode())
+			}
+		}
+	})
+
+	log.Println("starting ssh server on port 2222...")
+	if err := ssh.ListenAndServe(":2222", nil, ssh.AllocatePty()); err != nil && err != ssh.ErrServerClosed {
+		log.Fatal(err)
+	}
+}

context.go

@@ -55,6 +55,10 @@ var (
 	// ContextKeyPublicKey is a context key for use with Contexts in this package.
 	// The associated value will be of type PublicKey.
 	ContextKeyPublicKey = &contextKey{"public-key"}
+
+	// ContextKeySession is a context key for use with Contexts in this package.
+	// The associated value will be of type Session.
+	ContextKeySession = &contextKey{"session"}
 )
 
 // Context is a package specific context interface. It exposes connection

go.mod

@@ -1,10 +1,16 @@
 module github.com/charmbracelet/ssh
 
-go 1.17
+go 1.21
+
+toolchain go1.21.5
 
 require (
 	github.com/anmitsu/go-shlex v0.0.0-20200514113438-38f4b401e2be
+	github.com/creack/pty v1.1.21
+	github.com/u-root/u-root v0.11.0
 	golang.org/x/crypto v0.17.0
 )
 
-require golang.org/x/sys v0.15.0 // indirect
+require golang.org/x/sys v0.16.0
+
+require github.com/charmbracelet/x/term v0.0.0-20240109162103-b354873f6f2c

go.sum

@@ -1,43 +1,16 @@
 github.com/anmitsu/go-shlex v0.0.0-20200514113438-38f4b401e2be h1:9AeTilPcZAjCFIImctFaOjnTIavg87rW78vTPkQqLI8=
 github.com/anmitsu/go-shlex v0.0.0-20200514113438-38f4b401e2be/go.mod h1:ySMOLuWl6zY27l47sB3qLNK6tF2fkHG55UZxx8oIVo4=
-github.com/yuin/goldmark v1.4.13/go.mod h1:6yULJ656Px+3vBD8DxQVa3kxgyrAnzto9xy5taEt/CY=
-golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
-golang.org/x/crypto v0.0.0-20210921155107-089bfa567519/go.mod h1:GvvjBRRGRdwPK5ydBHafDWAxML/pGHZbMvKqRZ5+Abc=
+github.com/charmbracelet/x/term v0.0.0-20240109162103-b354873f6f2c h1:pm2npO09x7mp7OES8BmqqEuVCEXyhj1XEjrJlKJpN1A=
+github.com/charmbracelet/x/term v0.0.0-20240109162103-b354873f6f2c/go.mod h1:viW49uh1UJ6F1f2UglwW4tZo7eJn5wZXEq4PKt3873Q=
+github.com/creack/pty v1.1.21 h1:1/QdRyBaHHJP61QkWMXlOIBfsgdDeeKfK8SYVUWJKf0=
+github.com/creack/pty v1.1.21/go.mod h1:MOBLtS5ELjhRRrroQr9kyvTxUAFNvYEK993ew/Vr4O4=
+github.com/u-root/gobusybox/src v0.0.0-20221229083637-46b2883a7f90 h1:zTk5683I9K62wtZ6eUa6vu6IWwVHXPnoKK5n2unAwv0=
+github.com/u-root/gobusybox/src v0.0.0-20221229083637-46b2883a7f90/go.mod h1:lYt+LVfZBBwDZ3+PHk4k/c/TnKOkjJXiJO73E32Mmpc=
+github.com/u-root/u-root v0.11.0 h1:6gCZLOeRyevw7gbTwMj3fKxnr9+yHFlgF3N7udUVNO8=
+github.com/u-root/u-root v0.11.0/go.mod h1:DBkDtiZyONk9hzVEdB/PWI9B4TxDkElWlVTHseglrZY=
 golang.org/x/crypto v0.17.0 h1:r8bRNjWL3GshPW3gkd+RpvzWrZAwPS49OmTGZ/uhM4k=
 golang.org/x/crypto v0.17.0/go.mod h1:gCAAfMLgwOJRpTjQ2zCCt2OcSfYMTeZVSRtQlPC7Nq4=
-golang.org/x/mod v0.6.0-dev.0.20220419223038-86c51ed26bb4/go.mod h1:jJ57K6gSWd91VN4djpZkiMVwK6gcyfeH4XE8wZrZaV4=
-golang.org/x/mod v0.8.0/go.mod h1:iBbtSCu2XBx23ZKBPSOrRkjjQPZFPuis4dIYUhu/chs=
-golang.org/x/net v0.0.0-20190620200207-3b0461eec859/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
-golang.org/x/net v0.0.0-20210226172049-e18ecbb05110/go.mod h1:m0MpNAwzfU5UDzcl9v0D8zg8gWTRqZa9RBIspLL5mdg=
-golang.org/x/net v0.0.0-20220722155237-a158d28d115b/go.mod h1:XRhObCWvk6IyKnWLug+ECip1KBveYUHfp+8e9klMJ9c=
-golang.org/x/net v0.6.0/go.mod h1:2Tu9+aMcznHK/AK1HMvgo6xiTLG5rD5rZLDS+rp2Bjs=
-golang.org/x/net v0.10.0/go.mod h1:0qNGK6F8kojg2nk9dLZ2mShWaEBan6FAoqfSigmmuDg=
-golang.org/x/sync v0.0.0-20190423024810-112230192c58/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
-golang.org/x/sync v0.0.0-20220722155255-886fb9371eb4/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
-golang.org/x/sync v0.1.0/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
-golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
-golang.org/x/sys v0.0.0-20201119102817-f84b799fce68/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
-golang.org/x/sys v0.0.0-20210615035016-665e8c7367d1/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
-golang.org/x/sys v0.0.0-20220520151302-bc2c85ada10a/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
-golang.org/x/sys v0.0.0-20220722155257-8c9f86f7a55f/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
-golang.org/x/sys v0.5.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
-golang.org/x/sys v0.8.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
-golang.org/x/sys v0.15.0 h1:h48lPFYpsTvQJZF4EKyI4aLHaev3CxivZmv7yZig9pc=
-golang.org/x/sys v0.15.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
-golang.org/x/term v0.0.0-20201126162022-7de9c90e9dd1/go.mod h1:bj7SfCRtBDWHUb9snDiAeCFNEtKQo2Wmx5Cou7ajbmo=
-golang.org/x/term v0.0.0-20210927222741-03fcf44c2211/go.mod h1:jbD1KX2456YbFQfuXm/mYQcufACuNUgVhRMnK/tPxf8=
-golang.org/x/term v0.5.0/go.mod h1:jMB1sMXY+tzblOD4FWmEbocvup2/aLOaQEp7JmGp78k=
-golang.org/x/term v0.8.0/go.mod h1:xPskH00ivmX89bAKVGSKKtLOWNx2+17Eiy94tnKShWo=
+golang.org/x/sys v0.16.0 h1:xWw16ngr6ZMtmxDyKyIgsE93KNKz5HKmMa3b8ALHidU=
+golang.org/x/sys v0.16.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
 golang.org/x/term v0.15.0 h1:y/Oo/a/q3IXu26lQgl04j/gjuBDOBlx7X6Om1j2CPW4=
 golang.org/x/term v0.15.0/go.mod h1:BDl952bC7+uMoWR75FIrCDx79TPU9oHkTZ9yRbYOrX0=
-golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
-golang.org/x/text v0.3.3/go.mod h1:5Zoc/QRtKVWzQhOtBMvqHzDpF6irO9z98xDceosuGiQ=
-golang.org/x/text v0.3.7/go.mod h1:u+2+/6zg+i71rQMx5EYifcz6MCKuco9NR6JIITiCfzQ=
-golang.org/x/text v0.7.0/go.mod h1:mrYo+phRRbMaCq/xk9113O4dZlRixOauAjOtrjsXDZ8=
-golang.org/x/text v0.9.0/go.mod h1:e1OnstbJyHTd6l/uOt8jFFHp6TRDWZR/bV3emEE/zU8=
-golang.org/x/text v0.14.0/go.mod h1:18ZOQIKpY8NJVqYksKHtTdi31H5itFRjB5/qKTNYzSU=
-golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
-golang.org/x/tools v0.0.0-20191119224855-298f0cb1881e/go.mod h1:b+2E5dAYhXwXZwtnZ6UAqBI28+e2cm9otk0dWdXHAEo=
-golang.org/x/tools v0.1.12/go.mod h1:hNGJHUnrk76NpqgfD5Aqm5Crs+Hm0VOH/i9J2+nxYbc=
-golang.org/x/tools v0.6.0/go.mod h1:Xwgl3UAJ/d3gWutnCtw505GrjyAbvKui8lOU390QaIU=
-golang.org/x/xerrors v0.0.0-20190717185122-a985d3407aa7/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=

options.go

@@ -68,7 +68,7 @@ func HostKeyPEM(bytes []byte) Option {
 // denying PTY requests.
 func NoPty() Option {
 	return func(srv *Server) error {
-		srv.PtyCallback = func(ctx Context, pty Pty) bool {
+		srv.PtyCallback = func(Context, Pty) bool {
 			return false
 		}
 		return nil
@@ -82,3 +82,31 @@ func WrapConn(fn ConnCallback) Option {
 		return nil
 	}
 }
+
+var contextKeyEmulatePty = &contextKey{"emulate-pty"}
+
+func emulatePtyHandler(ctx Context, _ Session, _ Pty) (func() error, error) {
+	ctx.SetValue(contextKeyEmulatePty, true)
+	return func() error { return nil }, nil
+}
+
+// EmulatePty returns a functional option that fakes a PTY. It uses PtyWriter
+// underneath.
+func EmulatePty() Option {
+	return func(s *Server) error {
+		s.PtyHandler = emulatePtyHandler
+		return nil
+	}
+}
+
+// AllocatePty returns a functional option that allocates a PTY. Implementers
+// who wish to use an actual PTY should use this along with the platform
+// specific PTY implementation defined in pty_*.go.
+func AllocatePty() Option {
+	return func(s *Server) error {
+		s.PtyHandler = func(_ Context, s Session, pty Pty) (func() error, error) {
+			return s.(*session).ptyAllocate(pty.Term, pty.Window, pty.Modes)
+		}
+		return nil
+	}
+}

pty.go

@@ -2,9 +2,14 @@ package ssh
 
 import (
 	"bytes"
+	"errors"
 	"io"
+	"os/exec"
 )
 
+// ErrUnsupported is returned when the platform does not support PTY.
+var ErrUnsupported = errors.New("pty unsupported")
+
 // NewPtyWriter creates a writer that handles when the session has a active
 // PTY, replacing the \n with \r\n.
 func NewPtyWriter(w io.Writer) io.Writer {
@@ -55,3 +60,12 @@ func (rw readWriterDelegate) Read(p []byte) (n int, err error) {
 func (rw readWriterDelegate) Write(p []byte) (n int, err error) {
 	return rw.w.Write(p)
 }
+
+// Start starts a *exec.Cmd attached to the Session. If a PTY is allocated,
+// it will use that for I/O.
+// On Windows, the process execution lifecycle is not managed by Go and has to
+// be managed manually. This means that c.Wait() won't work.
+// See https://github.com/charmbracelet/x/blob/main/term/conpty/conpty_windows.go#L155
+func (p *Pty) Start(c *exec.Cmd) error {
+	return p.start(c)
+}

pty_other.go

@@ -0,0 +1,44 @@
+//go:build !linux && !darwin && !freebsd && !dragonfly && !netbsd && !openbsd && !solaris && !windows
+// +build !linux,!darwin,!freebsd,!dragonfly,!netbsd,!openbsd,!solaris,!windows
+
+package ssh
+
+import (
+	"os/exec"
+
+	"golang.org/x/crypto/ssh"
+)
+
+type impl struct{}
+
+func (i *impl) IsZero() bool {
+	return true
+}
+
+func (i *impl) Name() string {
+	return ""
+}
+
+func (i *impl) Read(p []byte) (n int, err error) {
+	return 0, ErrUnsupported
+}
+
+func (i *impl) Write(p []byte) (n int, err error) {
+	return 0, ErrUnsupported
+}
+
+func (i *impl) Resize(w int, h int) error {
+	return ErrUnsupported
+}
+
+func (i *impl) Close() error {
+	return nil
+}
+
+func (*impl) start(*exec.Cmd) error {
+	return ErrUnsupported
+}
+
+func newPty(Context, string, Window, ssh.TerminalModes) (impl, error) {
+	return impl{}, ErrUnsupported
+}