Ignore boring return codes properly.

[tripe] / server / privsep.c

/* -*-c-*-
 *
 * Privilege separation communication protocol
 *
 * (c) 2008 Straylight/Edgeware
 */

/*----- Licensing notice --------------------------------------------------*
 *
 * This file is part of Trivial IP Encryption (TrIPE).
 *
 * TrIPE is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * TrIPE is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with TrIPE; if not, write to the Free Software Foundation,
 * Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 */

/*----- Header files ------------------------------------------------------*/

#include "tripe.h"
#include "priv.h"

/*----- Static variables --------------------------------------------------*/

static pid_t kid = -1;
static sig sig_chld;

/*----- Fetching a tunnel file descriptor ---------------------------------*/

/* --- @ps_tunfd@ --- *
 *
 * Arguments:	@const tunnel_ops *tops@ = pointer to tunnel operations
 *		@char **ifn@ = where to put the interface name
 *
 * Returns:	The file descriptor, or @-1@ on error.
 *
 * Use:		Fetches a file descriptor for a tunnel driver.
 */

int ps_tunfd(const tunnel_ops *tops, char **ifn)
{
  unsigned code;
  ssize_t n;
  dstr d = DSTR_INIT;
  int fd;

  if (pc_fd == -1) {
    a_warn("PRIVSEP", "helper-died", A_END);
    return (-1);
  }
  T( trace(T_PRIVSEP,
	   "privsep: requesting descriptor for %s tunnel",
	   tops->name); )
  if (pc_putuint(PS_TUNRQ) || pc_putstring(tops->name)) {
    a_warn("PRIVSEP", "helper-write-error", "?ERRNO", A_END);
    goto lose;
  }
  for (;;) {
    n = fdpass_recv(pc_fd, &fd, &code, sizeof(code));
    if (n < 0) goto readlose;
    if (n < sizeof(code)) {
      a_warn("PRIVSEP", "helper-short-read", A_END);
      goto lose;
    }
    switch (code) {
      case PS_TUNFD:
	if (fd == -1) {
	  a_warn("PRIVSEP", "no-fd-from-helper", A_END);
	  goto lose;
	}
	if (pc_getstring(&d)) { close(fd); goto readlose; }
	*ifn = xstrdup(d.buf);
	T( trace(T_PRIVSEP,
		 "privsep: received winning descriptor for %s",
		 *ifn); )
	goto done;
      case PS_TUNERR:
	if (pc_geterr(&errno)) goto readlose;
	T( trace(T_PRIVSEP, "privsep: helper lost: %s", strerror(errno)); )
	fd = -1;
	goto done;
#ifndef NTRACE
      case PS_TRACE:
	if (pc_getuint(&code) || pc_getstring(&d)) goto readlose;
	trace(code, "%s", d.buf);
	DRESET(&d);
	break;
#endif
      case PS_WARN:
	if (pc_getstring(&d)) goto readlose;
	a_warn("*%s", d.buf, A_END);
	DRESET(&d);
	break;
      default:
	a_warn("PRIVSEP", "unknown-response-code", "%u", code, A_END);
	goto lose;
    }
  }
done:
  dstr_destroy(&d);
  return (fd);

readlose:
  a_warn("PRIVSEP", "helper-read-error", "?ERRNO", A_END);
lose:
  dstr_destroy(&d);
  close(pc_fd);
  pc_fd = -1;
  return (-1);
}

/*----- Main code ---------------------------------------------------------*/

/* --- @reap@ --- *
 *
 * Arguments:	@int sig@ = signal number (always @SIGCHLD@; ignored)
 *
 * Returns:	---
 *
 * Use:		Notices and reports child process death.
 */

static void reap(int sig, void *p)
{
  pid_t k;
  int st;

  for (;;) {
    k = waitpid(-1, &st, WNOHANG);
    if (k < 0) {
      switch (errno) {
	case EINTR:
	  break;
	default:
	  a_warn("SERVER", "waitpid-error", "?ERRNO", A_END);
	case ECHILD:
	  return;
      }
    }
    if (!k)
      return;
    if (k == kid) {
      if (WIFEXITED(st))
	a_warn("PRIVSEP", "child-exited", "%d", WEXITSTATUS(st), A_END);
      else if (WIFSIGNALED(st))
	a_warn("PRIVSEP", "child-killed", "%d", WTERMSIG(st), A_END);
      else
	a_warn("PRIVSEP", "child-died", "%d", st, A_END);
      kid = -1;
    }
  }
}

/* --- @ps_split@ --- *
 *
 * Arguments:	@int detachp@ = whether to detach the child from its terminal
 *
 * Returns:	---
 *
 * Use:		Separates off the privileged tunnel-opening service from the
 *		rest of the server.
 */

void ps_split(int detachp)
{
  pid_t kid;
  int fd[2];
  mdup_fd md[1];
  const char *helper;

  if (socketpair(PF_UNIX, SOCK_STREAM, 0, fd)) {
    die(EXIT_FAILURE,
	"failed to create socket pair for privilege separation: %s",
	strerror(errno));
  }
  helper = getenv("TRIPE_PRIVHELPER");
  if (!helper) helper = PRIVSEP_HELPER;
  fdflags(fd[0], 0, 0, FD_CLOEXEC, FD_CLOEXEC);
  fdflags(fd[1], 0, 0, FD_CLOEXEC, FD_CLOEXEC);
  sig_add(&sig_chld, SIGCHLD, reap, 0);
  kid = fork();
  if (kid == 0) {
    signal(SIGCHLD, SIG_DFL);
    if (detachp) detachtty();
    close(fd[1]);
    md[0].cur = fd[0]; md[0].want = STDIN_FILENO;
    if (mdup(md, 1)) goto lose;
    execl(helper, helper, (char *)0);
  lose:
    fprintf(stderr, "helper: failed to run helper: %s\n", strerror(errno));
    _exit(127);
  }
  T( trace(T_PRIVSEP, "privsep: forked child successfully"); )
  close(fd[0]);
  pc_fd = fd[1];
}

/* --- @ps_quit@ --- *
 *
 * Arguments:	---
 *
 * Returns:	---
 *
 * Use:		Detaches from the helper process.
 */

void ps_quit(void) { if (pc_fd != -1) close(pc_fd); }

/*----- That's all, folks -------------------------------------------------*/