droping privileges without chroot is now possible

5 files changed, 113 insertions, 54 deletions

diff --git a/doc/uanytun.8.txt b/doc/uanytun.8.txt
index 3364294..319a206 100644
--- a/doc/uanytun.8.txt
+++ b/doc/uanytun.8.txt
@@ -11,9 +11,9 @@ SYNOPSIS
 *uanytun*
 [ *-h|--help* ]
 [ *-D|--nodaemonize* ]
-[ *-C|--chroot* ]
 [ *-u|--username* <username> ]
-[ *-H|--chroot-dir* <directory> ]
+[ *-g|--groupname* <groupname> ]
+[ *-C|--chroot* <path> ]
 [ *-P|--write-pid* <filename> ]
 [ *-i|--interface* <ip-address> ]
 [ *-p|--port* <port> ]
@@ -56,30 +56,32 @@ passed to the daemon:
 -D|--nodaemonize
 ~~~~~~~~~~~~~~~~
 
-This option instructs *uAnytun* to run in the foreground
+This option instructs *uAnytun* to run in foreground
 instead of becoming a daemon which is the default.
 
--C|--chroot
-~~~~~~~~~~~
-
-Instruct *uAnytun* to run in a chroot chail and drop privileges. The 
-default is not to run in chroot.
-
 -u|--username <username>
 ~~~~~~~~~~~~~~~~~~~~~~~~
 
-if chroot change to this user. default: nobody
+run as this user. If no group is specified (*-g*) the default group of 
+the user is used. The default is to not drop privileges.
 
--H|--chroot-dir <directory>
-~~~~~~~~~~~~~~~~~~~~~~~~~~~
+-g|--groupname <groupname>
+~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+run as this group. If no username is specified (*-u*) this gets ignored.
+The default is to not drop privileges.
+
+-C|--chroot <path>
+~~~~~~~~~~~~~~~~~~
 
-chroot to this directory. default: /var/run/uanytun
+Instruct *uAnytun* to run in a chroot jail. The default is 
+to not run in chroot.
 
 -P|--write-pid <filename>
 ~~~~~~~~~~~~~~~~~~~~~~~~~
 
 Instruct *uAnytun* to write it's pid to this file. The default is 
-not to create a pid file.
+to not create a pid file.
 
 -i|--interface <ip address>
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~
diff --git a/src/daemon.h b/src/daemon.h
index 085f563..4ebc8cd 100644
--- a/src/daemon.h
+++ b/src/daemon.h
@@ -43,38 +43,83 @@
 #include <sys/stat.h>
 #include <unistd.h>
 
-void chrootAndDrop(const char* chrootdir, const char* username)
+struct priv_info_struct {
+  struct passwd* pw_;
+  struct group* gr_;
+};
+typedef struct priv_info_struct priv_info_t;
+
+int priv_init(priv_info_t* priv, const char* username, const char* groupname)
 {
-  if (getuid() != 0)
-  {
-    fprintf(stderr, "this programm has to be run as root in order to run in a chroot\n");
-    exit(-1);
-  }
+  if(!priv)
+    return -1;
 
-  struct passwd *pw = getpwnam(username);
-  if(pw) {
-    if(chroot(chrootdir))
-    {
-      fprintf(stderr, "can't chroot to %s\n", chrootdir);
-      exit(-1);
-    }
-    log_printf(NOTICE, "we are in chroot jail (%s) now\n", chrootdir);
-    if(chdir("/"))
-    {
-      fprintf(stderr, "can't change to /\n");
-      exit(-1);
-    }
-    if (initgroups(pw->pw_name, pw->pw_gid) || setgid(pw->pw_gid) || setuid(pw->pw_uid))
-    {
-      fprintf(stderr, "can't drop to user %s %d:%d\n", username, pw->pw_uid, pw->pw_gid);
-      exit(-1);
-    }
-    log_printf(NOTICE, "dropped user to %s %d:%d\n", username, pw->pw_uid, pw->pw_gid);
+  priv->pw_ = NULL;
+  priv->gr_ = NULL;
+
+  priv->pw_ = getpwnam(username);
+  if(!priv->pw_) {
+    log_printf(ERR, "unkown user %s", username);
+    return -1;
   }
+
+  if(groupname)
+    priv->gr_ = getgrnam(groupname);
   else
-  {
-    fprintf(stderr, "unknown user %s\n", username);
-    exit(-1);
+    priv->gr_ = getgrgid(priv->pw_->pw_gid);
+
+  if(!priv->gr_) {
+    log_printf(ERR, "unkown group %s", groupname);
+    return -1;
+  }
+
+  return 0;
+}
+
+int priv_drop(priv_info_t* priv)
+{
+  if(!priv || !priv->pw_ || !priv->gr_) {
+    log_printf(ERR, "privileges not initialized properly");
+    return -1;
+  }
+
+  if(setgid(priv->gr_->gr_gid))  {
+    log_printf(ERR, "setgid('%s') failed: %m", priv->gr_->gr_name);
+    return -1;
+  }
+
+  gid_t gr_list[1];
+	gr_list[0] = priv->gr_->gr_gid;
+	if(setgroups (1, gr_list)) {
+    log_printf(ERR, "setgroups(['%s']) failed: %m", priv->gr_->gr_name);
+    return -1;
+  }
+
+  if(setuid(priv->pw_->pw_uid)) {
+    log_printf(ERR, "setuid('%s') failed: %m", priv->pw_->pw_name);
+    return -1;
+  }
+
+  log_printf(NOTICE, "dropped privileges to %s:%s", priv->pw_->pw_name, priv->gr_->gr_name);
+  return 0;
+}
+
+
+int do_chroot(const char* chrootdir)
+{
+  if(getuid() != 0) {
+    log_printf(ERR, "this programm has to be run as root in order to run in a chroot");
+    return -1;
+  }
+
+  if(chroot(chrootdir)) {
+    log_printf(ERR, "can't chroot to %s: %m", chrootdir);
+    return -1;
+  }
+  log_printf(NOTICE, "we are in chroot jail (%s) now", chrootdir);
+  if(chdir("/")) {
+    log_printf(ERR, "can't change to /: %m");
+    return -1;
   }
 }
 
diff --git a/src/options.c b/src/options.c
index 9931c51..843cd4a 100644
--- a/src/options.c
+++ b/src/options.c
@@ -180,9 +180,9 @@ int options_parse(options_t* opt, int argc, char* argv[])
     if(!strcmp(str,"-h") || !strcmp(str,"--help"))
       return -1;
     PARSE_INVERSE_BOOL_PARAM("-D","--nodaemonize", opt->daemonize_)
-    PARSE_BOOL_PARAM("-C","--chroot", opt->chroot_)
     PARSE_STRING_PARAM("-u","--username", opt->username_)
-    PARSE_STRING_PARAM("-H","--chroot-dir", opt->chroot_dir_)
+    PARSE_STRING_PARAM("-g","--groupname", opt->groupname_)
+    PARSE_STRING_PARAM("-C","--chroot", opt->chroot_dir_)
     PARSE_STRING_PARAM("-P","--write-pid", opt->pid_file_)
     PARSE_STRING_PARAM("-i","--interface", opt->local_addr_)
     PARSE_STRING_PARAM("-p","--port", opt->local_port_)
@@ -236,9 +236,9 @@ void options_default(options_t* opt)
 
   opt->progname_ = strdup("uanytun");
   opt->daemonize_ = 1;
-  opt->chroot_ = 0;
-  opt->username_ = strdup("nobody");
-  opt->chroot_dir_ = strdup("/var/run/uanytun");
+  opt->username_ = NULL;
+  opt->groupname_ = NULL;
+  opt->chroot_dir_ = NULL;
   opt->pid_file_ = NULL;
   opt->local_addr_ = NULL;
   opt->local_port_ = strdup("4444");
@@ -276,6 +276,8 @@ void options_clear(options_t* opt)
     free(opt->progname_);
   if(opt->username_)
     free(opt->username_);
+  if(opt->groupname_)
+    free(opt->groupname_);
   if(opt->chroot_dir_)
     free(opt->chroot_dir_);
   if(opt->pid_file_)
@@ -319,9 +321,9 @@ void options_print_usage()
   printf("USAGE:\n");
   printf("uanytun [-h|--help]                         prints this...\n");
   printf("        [-D|--nodaemonize]                  don't run in background\n");
-  printf("        [-C|--chroot]                       chroot and drop privileges\n");
-  printf("        [-u|--username] <username>          if chroot change to this user\n");
-  printf("        [-H|--chroot-dir] <path>            chroot to this directory\n");
+  printf("        [-u|--username] <username>          change to this user\n");
+  printf("        [-g|--groupname] <groupname>        change to this group\n");
+  printf("        [-C|--chroot] <path>                chroot to this directory\n");
   printf("        [-P|--write-pid] <path>             write pid to this file\n");
   printf("        [-i|--interface] <ip-address>       local ip address to bind to\n");
   printf("        [-p|--port] <port>                  local port to bind to\n");
@@ -352,8 +354,8 @@ void options_print(options_t* opt)
 {
   printf("progname: '%s'\n", opt->progname_);
   printf("daemonize: %d\n", opt->daemonize_);
-  printf("chroot: %d\n", opt->chroot_);
   printf("username: '%s'\n", opt->username_);
+  printf("groupname: '%s'\n", opt->groupname_);
   printf("chroot_dir: '%s'\n", opt->chroot_dir_);
   printf("pid_file: '%s'\n", opt->pid_file_);
   printf("local_addr: '%s'\n", opt->local_addr_);
diff --git a/src/options.h b/src/options.h
index b1695a8..4186055 100644
--- a/src/options.h
+++ b/src/options.h
@@ -38,8 +38,8 @@
 struct options_struct {
   char* progname_;
   int daemonize_;
-  int chroot_;
   char* username_;
+  char* groupname_;
   char* chroot_dir_;
   char* pid_file_;
   char* local_addr_;
diff --git a/src/uanytun.c b/src/uanytun.c
index d1919d6..48cc020 100644
--- a/src/uanytun.c
+++ b/src/uanytun.c
@@ -341,6 +341,11 @@ int main(int argc, char* argv[])
     exit(ret);
   }
 
+  priv_info_t priv;
+  if(opt.username_)
+    if(priv_init(&priv, opt.username_, opt.groupname_))
+      exit(-1);
+
 #ifndef NO_CRYPT
 #ifndef USE_SSL_CRYPTO
   ret = init_libgcrypt();
@@ -395,8 +400,13 @@ int main(int argc, char* argv[])
     }
   }
 
-  if(opt.chroot_)
-    chrootAndDrop("/var/run/", "nobody");
+  if(opt.chroot_dir_)
+    if(do_chroot(opt.chroot_dir_))
+      exit(-1);
+  if(opt.username_)
+    if(priv_drop(&priv))
+      exit(-1);
+  
   if(opt.daemonize_) {
     pid_t oldpid = getpid();
     daemonize();