1 files changed, 89 insertions, 0 deletions
diff --git a/src/mds.c b/src/mds.c
new file mode 100644
index 0000000..07041fc
--- /dev/null
+++ b/src/mds.c
@@ -0,0 +1,89 @@
+/**
+ * mds — A micro-display server
+ * Copyright © 2014  Mattias Andrée (maandree@member.fsf.org)
+ * 
+ * This program 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 3 of the License, or
+ * (at your option) any later version.
+ * 
+ * This program 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 this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+#include "config.h"
+
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <errno.h>
+
+
+/**
+ * Entry point of the program
+ * 
+ * @param   argc  Number of elements in `argv`
+ * @param   argv  Command line arguments
+ * @return        Non-zero on error
+ */
+int main(int argc, const char** argv)
+{
+  struct stat attr;
+  
+  (void) argv;
+  
+  /* Sanity check the number of command line arguments. */
+  if (argc > 50)
+    {
+      fprintf(stderr,
+	      "%s: that number of arguments is ridiculous, I will not allow it.\n",
+	      *argv);
+      return 1;
+    }
+  
+  /* Stymied if the effective user is not root. */
+  if (geteuid() != ROOT_USER_UID)
+    {
+      fprintf(stderr,
+	      "%s: the effective user is not root, cannot continue.\n",
+	      *argv);
+      return 1;
+    }
+  
+  /* Create directory for socket files, PID files and such. */
+  if (stat(MDS_RUNTIME_ROOT_DIRECTORY, &attr) == 0)
+    {
+      /* Cannot create the directory, its pathname refers to an existing. */
+      if (S_ISDIR(attr.st_mode) == 0)
+	{
+	  /* But it is not a directory so we cannot continue. */
+	  fprintf(stderr,
+		  "%s: %s already exists but is not a directory.\n",
+		  MDS_RUNTIME_ROOT_DIRECTORY, *argv);
+	  return 1;
+	}
+    }
+  else
+    /* Directory is missing, create it. */
+    if (mkdir(MDS_RUNTIME_ROOT_DIRECTORY, 0755) < 0)
+      if (errno != EEXIST) /* Unlikely race condition. */
+	{
+	  perror(*argv);
+	  return 1;
+	}
+  
+  /* Drop privileges. They most not be propagated non-authorised components. */
+  if (seteuid(getuid()) < 0)
+    {
+      perror(*argv);
+      return 1;
+    }
+  
+  return 0;
+}
+