execute_program.c

   1 /*
   2  * This file is part of ltrace.
   3  * Copyright (C) 2011,2012 Petr Machata, Red Hat Inc.
   4  * Copyright (C) 2010 Joe Damato
   5  * Copyright (C) 1998,1999,2003,2008,2009 Juan Cespedes
   6  * Copyright (C) 2006 Ian Wienand
   7  *
   8  * This program is free software; you can redistribute it and/or
   9  * modify it under the terms of the GNU General Public License as
  10  * published by the Free Software Foundation; either version 2 of the
  11  * License, or (at your option) any later version.
  12  *
  13  * This program is distributed in the hope that it will be useful, but
  14  * WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  16  * General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU General Public License
  19  * along with this program; if not, write to the Free Software
  20  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
  21  * 02110-1301 USA
  22  */
  23 #include "config.h"
  24
  25 #if defined(HAVE_LIBUNWIND)
  26 #include <libunwind-ptrace.h>
  27 #endif /* defined(HAVE_LIBUNWIND) */
  28
  29 #include <stdio.h>
  30 #include <stdlib.h>
  31 #include <sys/types.h>
  32 #include <sys/stat.h>
  33 #include <unistd.h>
  34 #include <errno.h>
  35 #include <string.h>
  36 #include <pwd.h>
  37 #include <grp.h>
  38
  39 #include "backend.h"
  40 #include "options.h"
  41 #include "debug.h"
  42
  43 static void
  44 change_uid(const char * command)
  45 {
  46         uid_t run_uid, run_euid;
  47         gid_t run_gid, run_egid;
  48
  49         if (options.user) {
  50                 struct passwd *pent;
  51
  52                 if (getuid() != 0 || geteuid() != 0) {
  53                         fprintf(stderr,
  54                                 "you must be root to use the -u option\n");
  55                         exit(1);
  56                 }
  57                 if ((pent = getpwnam(options.user)) == NULL) {
  58                         fprintf(stderr, "cannot find user `%s'\n", options.user);
  59                         exit(1);
  60                 }
  61                 run_uid = pent->pw_uid;
  62                 run_gid = pent->pw_gid;
  63
  64                 if (initgroups(options.user, run_gid) < 0) {
  65                         perror("ltrace: initgroups");
  66                         exit(1);
  67                 }
  68         } else {
  69                 run_uid = getuid();
  70                 run_gid = getgid();
  71         }
  72         if (options.user || !geteuid()) {
  73                 struct stat statbuf;
  74                 run_euid = run_uid;
  75                 run_egid = run_gid;
  76
  77                 if (!stat(command, &statbuf)) {
  78                         if (statbuf.st_mode & S_ISUID) {
  79                                 run_euid = statbuf.st_uid;
  80                         }
  81                         if (statbuf.st_mode & S_ISGID) {
  82                                 run_egid = statbuf.st_gid;
  83                         }
  84                 }
  85                 if (setregid(run_gid, run_egid) < 0) {
  86                         perror("ltrace: setregid");
  87                         exit(1);
  88                 }
  89                 if (setreuid(run_uid, run_euid) < 0) {
  90                         perror("ltrace: setreuid");
  91                         exit(1);
  92                 }
  93         }
  94 }
  95
  96 pid_t
  97 execute_program(const char * command, char **argv)
  98 {
  99         pid_t pid;
 100
 101         debug(1, "Executing `%s'...", command);
 102
 103         pid = fork();
 104         if (pid < 0) {
 105         fail:
 106                 perror("ltrace: fork");
 107                 exit(1);
 108         } else if (!pid) {      /* child */
 109                 change_uid(command);
 110                 trace_me();
 111                 execvp(command, argv);
 112                 fprintf(stderr, "Can't execute `%s': %s\n", command,
 113                         strerror(errno));
 114                 _exit(1);
 115         }
 116
 117         if (wait_for_proc(pid) < 0)
 118                 goto fail;
 119
 120         debug(1, "PID=%d", pid);
 121         return pid;
 122 }