CVE-2014-0210: unvalidated length in _fs_recv_conn_setup() from…

CVE-2014-0210: unvalidated length in _fs_recv_conn_setup() from xorg/lib/libXfont commit 891e084b26837162b12f841060086a105edde86d The connection setup reply from the font server can include a list of alternate servers to contact if this font server stops working. The reply specifies a total size of all the font server names, and then provides a list of names. _fs_recv_conn_setup() allocated the specified total size for copying the names to, but didn't check to make sure it wasn't copying more data to that buffer than the size it had allocated. v2: use xfree() instead of free() for nx-libs 3.6.x (Mihai Moldovan)

CVE-2014-0210: unvalidated length in _fs_recv_conn_setup() from…
31322c2b · Mike DePaulo · Mihai Moldovan · c0d0e373 · 31322c2b
Commit 31322c2b authored Feb 08, 2015 by Mike DePaulo Committed by Mihai Moldovan Feb 16, 2015
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Showing with 18 additions and 3 deletions

fserve.c nx-X11/lib/font/fc/fserve.c +18 -3

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--- a/nx-X11/lib/font/fc/fserve.c
+++ b/nx-X11/lib/font/fc/fserve.c
@@ -2985,7 +2985,7 @@ _fs_recv_conn_setup (FSFpePtr conn)
    int			ret;
    fsConnSetup		*setup;
    FSFpeAltPtr		alts;
-    int			i, alt_len;
+    unsigned int	i, alt_len;
    int			setup_len;
    char		*alt_save, *alt_names;
    
@@ -3012,9 +3012,9 @@ _fs_recv_conn_setup (FSFpePtr conn)
 	}
 	if (setup->num_alternates)
 	{
+	    size_t alt_name_len = setup->alternate_len << 2;
 	    alts = (FSFpeAltPtr) xalloc (setup->num_alternates * 
-					 sizeof (FSFpeAltRec) +
-					 (setup->alternate_len << 2));
+					 sizeof (FSFpeAltRec) + alt_name_len);
 	    if (alts)
 	    {
 		alt_names = (char *) (setup + 1);
@@ -3023,10 +3023,25 @@ _fs_recv_conn_setup (FSFpePtr conn)
 		{
 		    alts[i].subset = alt_names[0];
 		    alt_len = alt_names[1];
+		    if (alt_len >= alt_name_len) {
+			/*
+			 * Length is longer than setup->alternate_len
+			 * told us to allocate room for, assume entire
+			 * alternate list is corrupted.
+			 */
+#ifdef DEBUG
+			fprintf (stderr,
+				 "invalid alt list (length %lx >= %lx)\n",
+				 (long) alt_len, (long) alt_name_len);
+#endif
+			xfree(alts);
+			return FSIO_ERROR;
+		    }
 		    alts[i].name = alt_save;
 		    memcpy (alt_save, alt_names + 2, alt_len);
 		    alt_save[alt_len] = '\0';
 		    alt_save += alt_len + 1;
+		    alt_name_len -= alt_len + 1;
 		    alt_names += _fs_pad_length (alt_len + 2);
 		}
 		conn->numAlts = setup->num_alternates;