deslogind.c

非常经典的加密算法

/*
 * Copyright 1994 David A. Barrett.
 *
 * Remote login deaemon with authentication and data encryption of channel
 *
 * Revision History:
 *
 *    12-May-94:  Fixed two malloc bugs in gendeskd.c and deslogind.c.
 *    14-Jun-94:  
 *        deslogind.c:	Added -w option for login wrapper feature
 *                      -w option busted on HP-UX; wait for help.
 *                      Added RHOSTNAME environment variable.
 *        utmp.c:	added update of wtmp to writeut
 *        log.c:	ifdef'd return result from openlog
 *        socket.c:	errno.h inside #undef posix for ENOTSOCK (BSD/386)
 *        tty.c:	added control terminal setting for BSD/386
 *        changed "psignal" to "posignal" to avoid BSD name conflict
 *        added changes for BSDI BSD/386 
 *        changed include <ctype.h> before <stdlib.h> for BSD/386
 *        Thanks to Tom Markson <[e-mail]> for BSD/386 changes.
 *        
 * Still to do:
 *   Make the -w option work for HP-UX
 *   Add '.' notation to hostname stuff on socket.c to allow IP addr to be used
 *   figure out a way to run commands and pipelines:
 *      it requires a way to make sure the pipes are flushed before exit
 *      it may require detection of EOF across network
 *   Add ip address to utmp entry for system V. fix in socket.c.
 *   On hpux, can't reuse port numbers for a short while after exit.  Why?
 *   Check permissions on deslogin.users, and deslogin.log; issue warning.
 *   Encrypt the log files too.
 *   Catch all Coredump signals to prevent hostile user from signaling
 *      us and examining the carcass for keys (deslogind, deslogingw).
 *   How do you prevent a debugger from doing a ptrace(PT_ATTACH)? (cant!)
 *   Compression (tricky because you must not impose delays)
 *   Allow socket to be connected directly to resulting process 
 *       (won't happen because the parent is needed to encipher the data stream)
 *   Figure out a way to improve protection from local users:
 *      X11 server DISPLAY variable:
 *         :0 still doesn't help because that creates a unix-domain socket:
 *         named /usr/spool/sockets/X11/0 
 *
 *   Deslogin:
 *      Make sure that getPassphrase is not reading from unsecure device:
 *         check $DISPLAY envt for 'local:' or ':' as prefix
 *         check utmp to make sure not rlogin from somewhere else
 *         permissions on Ctermid?  Trojan Ctermid?
 *      Protect against trojan of deslogin itself.
 *
 * Enhancements:
 *     See rshd man page for internet socket login protocol.  
 *        Secondary socket for stderr ASCII port # '\0' terminated 0=none
 *        upto 16 character server user name '\0' terminated
 *        upto 16 character client user name '\0' terminated
 *        command to execute limited by system's argument list
 *        Server authenticates channel and sends a null byte to stderr sock
 *           errors are sent with a '\1' as leading byte with mesage.
 *     Notice that hpux rlogind man page describes a different protocol also.
 *     Add passphrase command
 *
 * Inetd notes:
 *    Umask and uid inherited from init and envt
 *    Socket is available as stdin and stdout
 *
 * Notes:
 *    I have set posignal so that SIGSTOP will not cause SIGCHLD.  This allows
 *    you to STOP a potential intruder in his tracks by sending SIGSTOP to
 *    the process and then attach a debugger to it and examine what is going
 *    on.
 *
 * Comments which Give a Section number and line number correspond to
 * quotes from IEEE Std 1003.1-1990 (ISO/IEC 9945-1: 1990).  
 * (E.g. Sect5:10-12 means Section 5 lines 10 through 12 inclusive)
 */
#define _POSIX_SOURCE
#include <sys/types.h>	/* gid_t pid_t uid_t clock_t */
#include <sys/times.h>	/* struct tms */
			/* mips fails to define prototype for times() unless */
			/* __POSIX is defined.  Strange.  */
#include <unistd.h> 	/* chdir close dup execve fork */
			/* getlogin getpid getppid getpgrp */
			/* setsid setgid setpgid setuid */
			/* _SC_NGROUPS_MAX */
#include <limits.h>	/* NGROUPS_MAX */
#include <ctype.h>	/* must be before stdlib.h for BSDI's BSD 386 */
#include <stdlib.h>	/* atexit exit free malloc */
#include <stdio.h>	/* (fopen fclose fgets scanf printf etc.); ctermid */
#include <string.h>	/* memcmp memcpy memset */
#include <errno.h>
#include <sys/stat.h>	/* umask flags */
#include <fcntl.h>
#include <termios.h>
#include <signal.h>
#include <pwd.h>
#include <time.h>	/* time asctime */
#include <sys/wait.h>	/* WNOHANG */
#include "pty.h"
#include "tty.h"
#include "auth.h"
#include "txfr.h"
#include "socket.h"
#include "log.h"
#include "deslogin.h"
#include "posignal.h"
#include "utmp.h"		/* setlogin */
#include "group.h"		/* getLoginGroups */

#ifdef sun
#define BSD
#endif
#ifdef mips
#define BSD
#endif

/*
 * Begin customizable area
 */
#ifndef DEFAULT_UMASK	/* login user mask */
#define DEFAULT_UMASK	S_IWGRP|S_IWOTH
#endif
#ifndef TTY_MODE	/* login permissions for controlling terminal */
#define TTY_MODE   	(S_IRUSR|S_IWUSR|S_IWGRP|S_IWOTH)
#endif

#define TTY_RWANY   	(S_IRUSR|S_IWUSR|S_IRGRP|S_IWGRP|S_IROTH|S_IWOTH)

/*
 * These environment variables may be overwridden in the makefile
 */
#ifdef BSD		/* sun dec mips */
#ifndef USERPATH
#define USERPATH	":/usr/ucb:/bin:/usr/bin"
#endif
#ifndef SYSTEMPATH
#define SYSTEMPATH	"/etc:/usr/ucb:/bin:/usr/bin"
#endif
#endif
#ifdef hpux		/* hpux only */
#define DEFAULT_MAIL	"/usr/mail/"
#endif

#ifndef USER_ENV	/* Additional envt variable to store userName */
#define USER_ENV	"USER"		/* BSD (sun dec mips) xdm (not hpux) */
#endif
#ifndef USERPATH
#define USERPATH	":/bin:/usr/bin"
#endif
#ifndef SYSTEMPATH
#define SYSTEMPATH	"/etc:/bin:/usr/bin"
#endif
#ifndef DEFAULT_TERM
#define DEFAULT_TERM	"network"
#endif

#ifndef USER_FILE
#define USER_FILE	"/usr/local/etc/deslogind.users"
#endif

#ifndef NOLOGIN_FILE
#define NOLOGIN_FILE	"/etc/nologin"
#endif
#ifndef LOG_FILE
#define LOG_FILE	"/usr/adm/deslogind.log"
#endif

/*
 * End of customizable area
 */
#define PROGNAME_SIZE	255
#define USERNAME_SIZE	17	/* assumption based on rshd man page */

#define MAX_HOSTNAME	255

extern int optind;
extern char *optarg;

#if defined(__STDC__) || defined(__cplusplus)
extern int askTty(char *, char *, unsigned, int);
#else
extern int askTty();
#endif

extern unsigned long defaultKey[64];

static char ident[] = 
" @(#) deslogind.c  version 1.10 16-Jun-94 Copyright 1994 by Dave Barrett([e-mail])\n";
static char RCSid[] = 
" @(#) deslogind.c  $Revision: 1.10 $ $Date: 94/06/14 12:17:58 $\n";

char mainProgName[PROGNAME_SIZE];

char *progName, *argcName;
int  debug   = 0;
int  verbose = 0;

unsigned long inBytes  = 0;	/* for txfr */
unsigned long outBytes = 0;

struct termios oldmodes;

char *defaultShell = "/bin/ksh";

char *defaultArgv[] = {
   (char *) 0,			/* substituted with arg0 variable later */
   (char *) 0,			/* if -w, then substitudet with loginArg1 */
   (char *) 0,			/* if -w, then remote host name */
   (char *) 0
};

/*
 * Static data for -w option 
 */
char loginArg1[] = "-h";
char loginProg[] = LOGIN_PROG;
char loginCwd[]  = "/";

void setProgName() {
   pid_t pid = getpid();				/* can't fail */
   sprintf(mainProgName, "%s[%lu]", argcName, (unsigned long) pid);
   progName = mainProgName;
}

void sigHandler(sig)
   int sig;
{
   switch (sig) {
   case SIGHUP:
   case SIGTERM:
   case SIGINT:
      log("%s: Terminated by signal %d\n", progName, sig);
      exit(1);			/* make sure cleanup occurs on interrupt */
      break;
   case SIGCHLD: 			/* child died */
      if (debug) {
	 log("%s: (main) SIGCHLD\n", progName);
      }
      break;
   default:
      break;
   }
}

char sname[PTY_NAMESIZE];   /* slave pty opened for shell control terminal */

/*
 * Registered with atexit
 */
void eraselogin()
{
   int res;

   res = setlogin(sname, (char *) 0, (char *) 0);
   if (res < 0) {
      log("%s: WARNING--eraselogin \"%s\" failed--%s\n", 
	 progName, sname, ERRMSG);
   }
   res = chmod(sname, TTY_RWANY);
   if (res < 0) {
      log("%s: WARNING--chmod \"%s\" to %o failed--%s\n",
	 progName, sname, TTY_RWANY, ERRMSG);
   }
}


/*
 * Duplicate the given file descriptor to the given mode with error check.
 */
int dupFd(fd, name, mode)
   int fd;
   char *name;
   mode_t mode;
{
   int newfd, res;

   newfd = dup(fd);
   if (newfd < 0) {
      log("%s: dup of fd %d (\"%s\") failed--%s\n",
	 progName, fd, name, ERRMSG);
      exit(1);
   }
   res = fcntl(newfd, F_SETFL, mode);
   if (res < 0) {
      log("%s: fcntl of fd %d (\"%s\") failed--%s\n", 
	 progName, newfd, name, ERRMSG);
      exit(1);
   }
   return newfd;
}

/*
 * Memory allocation with error check and abort
 */
void *allocate(size)
   register unsigned size;
{
   register void *res = (void *) malloc(size);

   if (res == (void *) 0) {
      log("%s: allocate of %u bytes failed\n", progName, size);
      exit(1);
   }
   return res;
}

/*
 * Create a copy of the input string. (0 if out of memory)
 */
char *newString(chp)
   register char *chp;
{
   register unsigned len = 0;
   register char *res;

   if (chp != (char *) 0) {
      len = strlen(chp);
   }

   res = (char *) allocate(len+1);
   if (res != (char *) 0) {
      memcpy(res, chp, len);
      res[len] = '\0';
   }
   return res;
}

void showEnv(prefix, envp)
   char *prefix;
   register char **envp;
{
   while (*envp != (char *) 0) {
      log("%s%s\n", prefix, *envp++);
   }
   log("\n");
}

/*
 * Add a new entry to the given environment.  Return the new environment.
 * Set input ep to NULL to create initial invironment
 * Frees the old environment.
 *
 * If out of memory occurs, 0 is returned
 */
char **updateEnv(ep, key, value)
   char **ep;
   char *key;
   char *value;
{
   register char **chpp = ep, **dstp = (char **) 0, **res;
   char *newEntry = (char *) 0;
   unsigned int envsize = 0, keylen = 0, vallen = 0;

   if (key != (char *) 0) {
      keylen = strlen(key);
   }
   if (ep != (char **) 0) {
      while (*chpp != (char *) 0) {
	 if (keylen != 0 && strncmp(key, *chpp, keylen) == 0) {
	    dstp = chpp;
	 }
	 chpp++;
      }
      envsize = chpp - ep;
   }

   if (keylen != 0 && value != (char *) 0) {
      vallen = strlen(value);
      newEntry = (char *) allocate(keylen+vallen+2);
      if (newEntry == (char *) 0) {
	 return (char **) 0;
      }
      memcpy(newEntry, key, keylen);
      memcpy(newEntry + keylen, "=", 1);
      memcpy(newEntry + keylen + 1, value, vallen);
      newEntry[keylen + vallen + 1] = '\0';
   }

   if (dstp != (char **) 0) {
      if (newEntry != (char *) 0) {	/* replace the entry */
	 free(dstp);
	 *dstp = newEntry;
	 return ep;
      } else {				/* delete the entry */
	 *dstp = ep[envsize-1];
	 free(ep[envsize-1]);		/* could cause problems */
	 ep[envsize-1] = (char *) 0;
	 return ep;
      }
   }

   if (newEntry != (char *) 0) {
      envsize++;
   }