#include <stdlib.h>
#include <syslog.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>

extern const char **environ;


#define SETUID 554 /* "pserver" user  UID */
#define SETGID 554 /* "pserver" group GID */
#define PERMITTED_ENV_LIST "PWD"
#define EXEC_PATHNAME "/usr/bin/cvs"


#ifndef G_GNUC_NORETURN
#if     __GNUC__ > 2 || (__GNUC__ == 2 && __GNUC_MINOR__ > 4)
#define G_GNUC_NORETURN __attribute__((noreturn))
#else   /* !__GNUC__ */
#define G_GNUC_NORETURN
#endif  /* !__GNUC__ */
#endif  /* !G_GNUC_NORETURN */

#define EXITLOG(msg...) do {\
	openlog("pserverchroot",LOG_PID,LOG_DAEMON); \
	syslog(LOG_CRIT,msg); \
	closelog(); \
	exit(EXIT_FAILURE); \
	} while (0)

#define LENGTH(x) (sizeof((x))/sizeof(*(x)))

#define FUNCCHK(funcname,args...) do { \
	if (errno=0,funcname(args)) \
		funcfail( #funcname ); \
	} while (0)

static void funcfail(const char *funcname) G_GNUC_NORETURN;
static void funcfail(const char *funcname)
{
	EXITLOG("Unable to %s(2): %s",funcname,strerror(errno));
}

int main(int argc,char **argv)
{
int total=0;
const char *allowed[]={ PERMITTED_ENV_LIST };
const char **allp,**envp;
char *dup=NULL,*s;

retry:
	for (envp=environ;*envp;envp++) {
		if (dup) free(dup);
		dup=strdup(*envp);
		if ((s=strchr(dup,'='))) *s='\0';
		for (allp=allowed;allp<allowed+LENGTH(allowed);allp++)
			if (!strcmp(dup,*allp)) goto ok;
		if (total++>1000)
			EXITLOG("Unable to clean environment for CVS pserver: %s",*envp);
		unsetenv(dup);
		goto retry;
ok:;
		}
	FUNCCHK(setenv,"PATH","/usr/bin",1);
	FUNCCHK(chroot,"/home/short/pserver");
	FUNCCHK(chdir,"/");
	FUNCCHK(setgid,SETGID);
	FUNCCHK(setuid,SETUID);
	if (!getuid() || !geteuid() || !getgid() || !getegid())
		EXITLOG("Privileges NOT dropped!: uid=%d,euid=%d,gid=%d,egid=%d",
				getuid(),geteuid(),getgid(),getegid());
	errno=0,execv(EXEC_PATHNAME,argv);
	funcfail("execv");
}