feat: allocate real pty

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 +1,36 @@
+//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) 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
+}

pty_unix.go

@@ -0,0 +1,190 @@
+//go:build darwin || dragonfly || freebsd || linux || netbsd || openbsd || solaris
+// +build darwin dragonfly freebsd linux netbsd openbsd solaris
+
+package ssh
+
+import (
+	"fmt"
+	"os"
+	"os/exec"
+	"syscall"
+
+	"github.com/creack/pty"
+	"github.com/u-root/u-root/pkg/termios"
+	"golang.org/x/crypto/ssh"
+	"golang.org/x/sys/unix"
+)
+
+type impl struct {
+	// Master is the master PTY file descriptor.
+	Master *os.File
+
+	// Slave is the slave PTY file descriptor.
+	Slave *os.File
+
+	// Name is the name of the slave PTY.
+	Name string
+}
+
+// Read implements ptyInterface.
+func (i *impl) Read(p []byte) (n int, err error) {
+	return i.Master.Read(p)
+}
+
+// Write implements ptyInterface.
+func (i *impl) Write(p []byte) (n int, err error) {
+	return i.Master.Write(p)
+}
+
+func (i *impl) Close() error {
+	if err := i.Master.Close(); err != nil {
+		return err
+	}
+	return i.Slave.Close()
+}
+
+func (i *impl) Resize(w int, h int) (rErr error) {
+	conn, err := i.Master.SyscallConn()
+	if err != nil {
+		return err
+	}
+
+	return conn.Control(func(fd uintptr) {
+		rErr = termios.SetWinSize(fd, &termios.Winsize{
+			Winsize: unix.Winsize{
+				Row: uint16(h),
+				Col: uint16(w),
+			},
+		})
+	})
+}
+
+func (i *impl) start(c *exec.Cmd) error {
+	c.Stdin, c.Stdout, c.Stderr := i.Slave, i.Slave, i.Slave
+	if c.SysProcAttr == nil {
+		c.SysProcAttr = &syscall.SysProcAttr{}
+	}
+}
+
+func newPty(_ Context, _ string, win Window, modes ssh.TerminalModes) (_ impl, rErr error) {
+	ptm, pts, err := pty.Open()
+	if err != nil {
+		return impl{}, err
+	}
+
+	conn, err := ptm.SyscallConn()
+	if err != nil {
+		return impl{}, err
+	}
+
+	if err := conn.Control(func(fd uintptr) {
+		rErr = applyTerminalModesToFd(fd, win.Width, win.Height, modes)
+	}); err != nil {
+		return impl{}, err
+	}
+
+	return impl{Master: ptm, Slave: pts, Name: pts.Name()}, rErr
+}
+
+func applyTerminalModesToFd(fd uintptr, width int, height int, modes ssh.TerminalModes) error {
+	// Get the current TTY configuration.
+	tios, err := termios.GTTY(int(fd))
+	if err != nil {
+		return fmt.Errorf("GTTY: %w", err)
+	}
+
+	// Apply the modes from the SSH request.
+	tios.Row = height
+	tios.Col = width
+
+	for c, v := range modes {
+		if c == ssh.TTY_OP_ISPEED {
+			tios.Ispeed = int(v)
+			continue
+		}
+		if c == ssh.TTY_OP_OSPEED {
+			tios.Ospeed = int(v)
+			continue
+		}
+		k, ok := terminalModeFlagNames[c]
+		if !ok {
+			continue
+		}
+		if _, ok := tios.CC[k]; ok {
+			tios.CC[k] = uint8(v)
+			continue
+		}
+		if _, ok := tios.Opts[k]; ok {
+			tios.Opts[k] = v > 0
+			continue
+		}
+	}
+
+	// Save the new TTY configuration.
+	if _, err := tios.STTY(int(fd)); err != nil {
+		return fmt.Errorf("STTY: %w", err)
+	}
+
+	return nil
+}
+
+// terminalModeFlagNames maps the SSH terminal mode flags to mnemonic
+// names used by the termios package.
+var terminalModeFlagNames = map[uint8]string{
+	ssh.VINTR:         "intr",
+	ssh.VQUIT:         "quit",
+	ssh.VERASE:        "erase",
+	ssh.VKILL:         "kill",
+	ssh.VEOF:          "eof",
+	ssh.VEOL:          "eol",
+	ssh.VEOL2:         "eol2",
+	ssh.VSTART:        "start",
+	ssh.VSTOP:         "stop",
+	ssh.VSUSP:         "susp",
+	ssh.VDSUSP:        "dsusp",
+	ssh.VREPRINT:      "rprnt",
+	ssh.VWERASE:       "werase",
+	ssh.VLNEXT:        "lnext",
+	ssh.VFLUSH:        "flush",
+	ssh.VSWTCH:        "swtch",
+	ssh.VSTATUS:       "status",
+	ssh.VDISCARD:      "discard",
+	ssh.IGNPAR:        "ignpar",
+	ssh.PARMRK:        "parmrk",
+	ssh.INPCK:         "inpck",
+	ssh.ISTRIP:        "istrip",
+	ssh.INLCR:         "inlcr",
+	ssh.IGNCR:         "igncr",
+	ssh.ICRNL:         "icrnl",
+	ssh.IUCLC:         "iuclc",
+	ssh.IXON:          "ixon",
+	ssh.IXANY:         "ixany",
+	ssh.IXOFF:         "ixoff",
+	ssh.IMAXBEL:       "imaxbel",
+	ssh.IUTF8:         "iutf8",
+	ssh.ISIG:          "isig",
+	ssh.ICANON:        "icanon",
+	ssh.XCASE:         "xcase",
+	ssh.ECHO:          "echo",
+	ssh.ECHOE:         "echoe",
+	ssh.ECHOK:         "echok",
+	ssh.ECHONL:        "echonl",
+	ssh.NOFLSH:        "noflsh",
+	ssh.TOSTOP:        "tostop",
+	ssh.IEXTEN:        "iexten",
+	ssh.ECHOCTL:       "echoctl",
+	ssh.ECHOKE:        "echoke",
+	ssh.PENDIN:        "pendin",
+	ssh.OPOST:         "opost",
+	ssh.OLCUC:         "olcuc",
+	ssh.ONLCR:         "onlcr",
+	ssh.OCRNL:         "ocrnl",
+	ssh.ONOCR:         "onocr",
+	ssh.ONLRET:        "onlret",
+	ssh.CS7:           "cs7",
+	ssh.CS8:           "cs8",
+	ssh.PARENB:        "parenb",
+	ssh.PARODD:        "parodd",
+	ssh.TTY_OP_ISPEED: "tty_op_ispeed",
+	ssh.TTY_OP_OSPEED: "tty_op_ospeed",
+}