CVE-2014-0210: unvalidated length fields in fs_read_query_info()

fs_read_query_info() parses a reply from the font server.  The reply
contains embedded length fields, none of which are validated.  This
can cause out of bound reads in either fs_read_query_info() or in
_fs_convert_props() which it calls to parse the fsPropInfo in the reply.

Reported-by: Ilja Van Sprundel <ivansprundel@ioactive.com>
Signed-off-by: Alan Coopersmith <alan.coopersmith@oracle.com>
Reviewed-by: Adam Jackson <ajax@redhat.com>
Reviewed-by: Matthieu Herrb <matthieu@herrb.eu>

2 files changed, 46 insertions, 0 deletions

diff --git a/src/fc/fsconvert.c b/src/fc/fsconvert.c
index 75b5372..dfa1317 100644
--- a/src/fc/fsconvert.c
+++ b/src/fc/fsconvert.c
@@ -118,6 +118,10 @@ _fs_convert_props(fsPropInfo *pi, fsPropOffset *po, pointer pd,
     for (i = 0; i < nprops; i++, dprop++, is_str++)
     {
 	memcpy(&local_off, off_adr, SIZEOF(fsPropOffset));
+	if ((local_off.name.position >= pi->data_len) ||
+		(local_off.name.length >
+		 (pi->data_len - local_off.name.position)))
+	    goto bail;
 	dprop->name = MakeAtom(&pdc[local_off.name.position],
 			       local_off.name.length, 1);
 	if (local_off.type != PropTypeString) {
@@ -125,10 +129,15 @@ _fs_convert_props(fsPropInfo *pi, fsPropOffset *po, pointer pd,
 	    dprop->value = local_off.value.position;
 	} else {
 	    *is_str = TRUE;
+	    if ((local_off.value.position >= pi->data_len) ||
+		(local_off.value.length >
+		 (pi->data_len - local_off.value.position)))
+		goto bail;
 	    dprop->value = (INT32) MakeAtom(&pdc[local_off.value.position],
 					    local_off.value.length, 1);
 	    if (dprop->value == BAD_RESOURCE)
 	    {
+	      bail:
 		free (pfi->props);
 		pfi->nprops = 0;
 		pfi->props = 0;
diff --git a/src/fc/fserve.c b/src/fc/fserve.c
index 3abbacf..ec5336e 100644
--- a/src/fc/fserve.c
+++ b/src/fc/fserve.c
@@ -854,6 +854,7 @@ fs_read_query_info(FontPathElementPtr fpe, FSBlockDataPtr blockrec)
     FSFpePtr		conn = (FSFpePtr) fpe->private;
     fsQueryXInfoReply	*rep;
     char		*buf;
+    long		bufleft; /* length of reply left to use */
     fsPropInfo		*pi;
     fsPropOffset	*po;
     pointer		pd;
@@ -885,6 +886,9 @@ fs_read_query_info(FontPathElementPtr fpe, FSBlockDataPtr blockrec)
     buf = (char *) rep;
     buf += SIZEOF(fsQueryXInfoReply);
 
+    bufleft = rep->length << 2;
+    bufleft -= SIZEOF(fsQueryXInfoReply);
+
     /* move the data over */
     fsUnpack_XFontInfoHeader(rep, pInfo);
 
@@ -892,17 +896,50 @@ fs_read_query_info(FontPathElementPtr fpe, FSBlockDataPtr blockrec)
     _fs_init_fontinfo(conn, pInfo);
 
     /* Compute offsets into the reply */
+    if (bufleft < SIZEOF(fsPropInfo))
+    {
+	ret = -1;
+#ifdef DEBUG
+	fprintf(stderr, "fsQueryXInfo: bufleft (%ld) < SIZEOF(fsPropInfo)\n",
+		bufleft);
+#endif
+	goto bail;
+    }
     pi = (fsPropInfo *) buf;
     buf += SIZEOF (fsPropInfo);
+    bufleft -= SIZEOF(fsPropInfo);
 
+    if ((bufleft / SIZEOF(fsPropOffset)) < pi->num_offsets)
+    {
+	ret = -1;
+#ifdef DEBUG
+	fprintf(stderr,
+		"fsQueryXInfo: bufleft (%ld) / SIZEOF(fsPropOffset) < %d\n",
+		bufleft, pi->num_offsets);
+#endif
+	goto bail;
+    }
     po = (fsPropOffset *) buf;
     buf += pi->num_offsets * SIZEOF(fsPropOffset);
+    bufleft -= pi->num_offsets * SIZEOF(fsPropOffset);
 
+    if (bufleft < pi->data_len)
+    {
+	ret = -1;
+#ifdef DEBUG
+	fprintf(stderr,
+		"fsQueryXInfo: bufleft (%ld) < data_len (%d)\n",
+		bufleft, pi->data_len);
+#endif
+	goto bail;
+    }
     pd = (pointer) buf;
     buf += pi->data_len;
+    bufleft -= pi->data_len;
 
     /* convert the properties and step over the reply */
     ret = _fs_convert_props(pi, po, pd, pInfo);
+  bail:
     _fs_done_read (conn, rep->length << 2);
 
     if (ret == -1)