add strequals and startswith macros + add drop_privileges macro that drops the group before the user

Signed-off-by: Mattias Andrée <maandree@operamail.com>

3 files changed, 44 insertions, 10 deletions

diff --git a/src/libmdsserver/macros.h b/src/libmdsserver/macros.h
index 0c2a2e2..bb4e1c3 100644
--- a/src/libmdsserver/macros.h
+++ b/src/libmdsserver/macros.h
@@ -23,6 +23,7 @@
 #include <stdio.h>
 #include <unistd.h>
 #include <pthread.h>
+#include <string.h>
 */
 
 
@@ -180,5 +181,39 @@
   buf_next(buffer, type, 1)
 
 
+/**
+ * Check whether two strings are equal
+ * 
+ * @param   a:char*  One of the strings
+ * @param   b:char*  The other of the strings
+ * @return  :int     Whether the strings are equal
+ */
+#define strequals(a, b)  \
+  (strcmp(a, b) == 0)
+
+
+/**
+ * Check whether a string starts with another string
+ * 
+ * @param   haystack:char*  The string to inspect
+ * @param   needle:char*    The string `haystack` should start with
+ * @return  :int            Whether `haystack` starts with `needle`
+ */
+#define startswith(haystack, needle)  \
+  (strstr(haystack, needle) == haystack)
+
+
+/**
+ * Set effective user and the effective group to the
+ * real user and the real group, respectively. If the
+ * group cannot be set, the user till not be set either.
+ * 
+ * @return  :int  Non-zero on error
+ */
+#define drop_privileges()                              \
+  ((getegid() == getgid() ? 0 : setegid(getgid())) ||  \
+   (geteuid() == getuid() ? 0 : seteuid(getuid())))
+
+
 #endif
 
diff --git a/src/mds-server.c b/src/mds-server.c
index 9f7d16b..20fc97e 100644
--- a/src/mds-server.c
+++ b/src/mds-server.c
@@ -123,8 +123,7 @@ int main(int argc_, char** argv_)
   
   
   /* Drop privileges like it's hot. */
-  if ((geteuid() == getuid() ? 0 : seteuid(getuid())) ||
-      (getegid() == getgid() ? 0 : setegid(getgid())))
+  if (drop_privileges())
     {
       perror(*argv);
       return 1;
@@ -143,7 +142,7 @@ int main(int argc_, char** argv_)
   for (i = 1; i < argc; i++)
     {
       char* arg = argv[i];
-      if (!strcmp(arg, "--initial-spawn")) /* Initial spawn? */
+      if (strequals(arg, "--initial-spawn")) /* Initial spawn? */
 	if (is_respawn == 1)
 	  {
 	    eprintf("conflicting arguments %s and %s cannot be combined.",
@@ -152,7 +151,7 @@ int main(int argc_, char** argv_)
 	  }
 	else
 	  is_respawn = 0;
-      else if (!strcmp(arg, "--respawn")) /* Respawning after crash? */
+      else if (strequals(arg, "--respawn")) /* Respawning after crash? */
 	if (is_respawn == 0)
 	  {
 	    eprintf("conflicting arguments %s and %s cannot be combined.",
@@ -161,7 +160,7 @@ int main(int argc_, char** argv_)
 	  }
 	else
 	  is_respawn = 1;
-      else if (strstr(arg, "--socket-fd=") == arg) /* Socket file descriptor. */
+      else if (startswith(arg, "--socket-fd=")) /* Socket file descriptor. */
 	{
 	  long int r;
 	  char* endptr;
@@ -173,15 +172,15 @@ int main(int argc_, char** argv_)
 	  arg += strlen("--socket-fd=");
 	  r = strtol(arg, &endptr, 10);
 	  if ((*argv == '\0') || isspace(*argv) ||
-	      (endptr - arg != (ssize_t)strlen(arg))
-	      || (r < 0) || (r > INT_MAX))
+	      (endptr - arg != (ssize_t)strlen(arg)) ||
+	      (r < 0) || (r > INT_MAX))
 	    {
 	      eprintf("invalid value for %s: %s.", "--socket-fd", arg);
 	      return 1;
 	    }
 	  socket_fd = (int)r;
 	}
-      else if (!strcmp(arg, "--re-exec")) /* Re-exec state-marshal. */
+      else if (strequals(arg, "--re-exec")) /* Re-exec state-marshal. */
 	reexec = 1;
       else
 	/* Not recognised, it is probably for another server. */
diff --git a/src/mds.c b/src/mds.c
index 82b5adb..df8fb31 100644
--- a/src/mds.c
+++ b/src/mds.c
@@ -88,7 +88,7 @@ int main(int argc_, char** argv_)
   for (j = 1; j < argc; j++)
     {
       char* arg = argv[j];
-      if (strstr(arg, "--master-server=") == arg) /* Master server. */
+      if (startswith(arg, "--master-server=")) /* Master server. */
 	{
 	  if (got_master_server)
 	    {
@@ -222,7 +222,7 @@ int main(int argc_, char** argv_)
   
   /* Drop privileges. They most not be propagated non-authorised components. */
   /* setgid should not be set, but just to be safe we are restoring both user and group. */
-  if ((seteuid(getuid()) < 0) || (setegid(getgid()) < 0))
+  if (drop_privileges())
     goto fail;
   
   /* Start master server and respawn it if it crashes. */