integer overflow in ReadInFile() in Xrm.c [CVE-2013-1981 7/13]

Called from XrmGetFileDatabase() which gets called from InitDefaults()
which gets the filename from getenv ("XENVIRONMENT")

If file is exactly 0xffffffff bytes long (or longer and truncates to
0xffffffff, on implementations where off_t is larger than an int),
then size may be set to a value which overflows causing less memory
to be allocated than is written to by the following read() call.

size is left limited to an int, because if your Xresources file is
larger than 2gb, you're very definitely doing it wrong.

Reported-by: Ilja Van Sprundel <ivansprundel@ioactive.com>
Signed-off-by: Alan Coopersmith <alan.coopersmith@oracle.com>
Reviewed-by: Matthieu Herrb <matthieu.herrb@laas.fr>

1 files changed, 4 insertions, 2 deletions

diff --git a/src/Xrm.c b/src/Xrm.c
index d6899d97..3e29ab0f 100644
--- a/src/Xrm.c
+++ b/src/Xrm.c
@@ -62,6 +62,7 @@ from The Open Group.
 #endif
 #include	<X11/Xos.h>
 #include	<sys/stat.h>
+#include	<limits.h>
 #include "Xresinternal.h"
 #include "Xresource.h"
 
@@ -1594,11 +1595,12 @@ ReadInFile(_Xconst char *filename)
      */
     {
 	struct stat status_buffer;
-	if ( (fstat(fd, &status_buffer)) == -1 ) {
+	if ( ((fstat(fd, &status_buffer)) == -1 ) ||
+             (status_buffer.st_size >= INT_MAX) ) {
 	    close (fd);
 	    return (char *)NULL;
 	} else
-	    size = status_buffer.st_size;
+	    size = (int) status_buffer.st_size;
     }
 
     if (!(filebuf = Xmalloc(size + 1))) { /* leave room for '\0' */