xs/hkexauth.go

172 lines
4.3 KiB
Go

// Authentication routines for the HKExSh
package herradurakex
import (
"bytes"
"encoding/csv"
"io"
"io/ioutil"
"log"
"runtime"
"github.com/jameskeane/bcrypt"
"golang.org/x/sys/unix"
)
func AuthUser(username string, auth string, fname string) (valid bool, allowedCmds string) {
b, e := ioutil.ReadFile(fname)
if e != nil {
valid = false
log.Println("ERROR: Cannot read hkexsh.passwd file!")
log.Fatal(e)
}
r := csv.NewReader(bytes.NewReader(b))
b = nil
runtime.GC() // Paranoia and prob. not effective; kill authFile in b[]
r.Comma = ':'
r.Comment = '#'
r.FieldsPerRecord = 4 // username:salt:authCookie:disallowedCmdList (a,b,...)
for {
record, err := r.Read()
if err == io.EOF {
break
}
if err != nil {
log.Fatal(err)
}
if username == record[0] {
tmp, _ := bcrypt.Hash(auth, record[1])
if tmp == record[2] {
valid = true
}
break
}
}
return
}
/* ------------- minimal terminal APIs brought in from ssh/terminal
* (they have no real business being there as they aren't specific to
* ssh, but as of v1.10, early 2018, core go stdlib hasn't yet done
* the planned terminal lib reorgs.)
* -------------
*/
// From github.com/golang/crypto/blob/master/ssh/terminal/util_linux.go
const ioctlReadTermios = unix.TCGETS
const ioctlWriteTermios = unix.TCSETS
// From github.com/golang/crypto/blob/master/ssh/terminal/util.go
// State contains the state of a terminal.
type State struct {
termios unix.Termios
}
// MakeRaw put the terminal connected to the given file descriptor into raw
// mode and returns the previous state of the terminal so that it can be
// restored.
func MakeRaw(fd int) (*State, error) {
termios, err := unix.IoctlGetTermios(fd, ioctlReadTermios)
if err != nil {
return nil, err
}
oldState := State{termios: *termios}
// This attempts to replicate the behaviour documented for cfmakeraw in
// the termios(3) manpage.
termios.Iflag &^= unix.IGNBRK | unix.BRKINT | unix.PARMRK | unix.ISTRIP | unix.INLCR | unix.IGNCR | unix.ICRNL | unix.IXON
termios.Oflag &^= unix.OPOST
termios.Lflag &^= unix.ECHO | unix.ECHONL | unix.ICANON | unix.ISIG | unix.IEXTEN
termios.Cflag &^= unix.CSIZE | unix.PARENB
termios.Cflag |= unix.CS8
termios.Cc[unix.VMIN] = 1
termios.Cc[unix.VTIME] = 0
if err := unix.IoctlSetTermios(fd, ioctlWriteTermios, termios); err != nil {
return nil, err
}
return &oldState, nil
}
// GetState returns the current state of a terminal which may be useful to
// restore the terminal after a signal.
func GetState(fd int) (*State, error) {
termios, err := unix.IoctlGetTermios(fd, ioctlReadTermios)
if err != nil {
return nil, err
}
return &State{termios: *termios}, nil
}
// Restore restores the terminal connected to the given file descriptor to a
// previous state.
func Restore(fd int, state *State) error {
return unix.IoctlSetTermios(fd, ioctlWriteTermios, &state.termios)
}
// ReadPassword reads a line of input from a terminal without local echo. This
// is commonly used for inputting passwords and other sensitive data. The slice
// returned does not include the \n.
func ReadPassword(fd int) ([]byte, error) {
termios, err := unix.IoctlGetTermios(fd, ioctlReadTermios)
if err != nil {
return nil, err
}
newState := *termios
newState.Lflag &^= unix.ECHO
newState.Lflag |= unix.ICANON | unix.ISIG
newState.Iflag |= unix.ICRNL
if err := unix.IoctlSetTermios(fd, ioctlWriteTermios, &newState); err != nil {
return nil, err
}
defer func() {
unix.IoctlSetTermios(fd, ioctlWriteTermios, termios)
}()
return readPasswordLine(passwordReader(fd))
}
// passwordReader is an io.Reader that reads from a specific file descriptor.
type passwordReader int
func (r passwordReader) Read(buf []byte) (int, error) {
return unix.Read(int(r), buf)
}
// readPasswordLine reads from reader until it finds \n or io.EOF.
// The slice returned does not include the \n.
// readPasswordLine also ignores any \r it finds.
func readPasswordLine(reader io.Reader) ([]byte, error) {
var buf [1]byte
var ret []byte
for {
n, err := reader.Read(buf[:])
if n > 0 {
switch buf[0] {
case '\n':
return ret, nil
case '\r':
// remove \r from passwords on Windows
default:
ret = append(ret, buf[0])
}
continue
}
if err != nil {
if err == io.EOF && len(ret) > 0 {
return ret, nil
}
return ret, err
}
}
}