#include <stdio.h>
#include <string.h>
#include <sys/stat.h>
#include <sys/param.h>
#include <unistd.h>
#include <errno.h>

#if defined (linux)
#define LOCAL_MAJOR 4
#endif
#if defined(__FreeBSD__) || defined(__OpenBSD__) || defined(__NetBSD__)
#define LOCAL_MAJOR 12
#endif

#define EXECNAME "/usr/bin/ssh"
#define MAXUSERNAME 20

int main() {
	char user[MAXUSERNAME+2];
	char* p;
	char *login;

	struct stat tty_stat;
	extern int errno;

	if( fstat( 0, &tty_stat ) < 0 ) {
		perror( "fstat()" );
		return 1;
	};
	if( ( tty_stat.st_mode & S_IFCHR ) == 0 ) {
		fprintf (stderr, "Running not from a character device!\n");
		return 1;
	};
	if((255 & (tty_stat.st_rdev >> 8)) != LOCAL_MAJOR ) {
		fprintf( stderr, "Only local forwarding allowed\n" );
		return 1;
	};
	if ((login=getlogin())==NULL) {
		fprintf(stderr, "getlogin() failed, bailing out\n");
		return 1;
	};
	printf( "login @ %s: ", login );
	fflush( stdout );
	if( fgets( user, sizeof user, stdin ) == NULL )
		return 1;
	if( ( p = strchr( user, '\n' ) ) == NULL ) {
		fprintf( stderr,
			"Name too long\n" );
		return 1;
	}
	*p = 0;
	fflush( NULL );
		(void) execlp(EXECNAME,EXECNAME,"-C","-cblowfish","-enone","-l",
			user,login,(char *) 0);
		perror("execlp()");
		_exit( 1 );
}