PPP: When un-escaping, don't allocate a too-large buffer.tizen_8.0_m2_releasetizen_7.0_m2_releasetizen_6.5.m2_releasesubmit/tizen_6.5/20211028.163901submit/tizen/20210106.042955submit/tizen/20201218.054408accepted/tizen/unified/20210107.123455accepted/tizen/8.0/unified/20231005.095602accepted/tizen/7.0/unified/hotfix/20221116.111453accepted/tizen/7.0/unified/20221110.061409accepted/tizen/6.5/unified/20211029.015054tizen_8.0tizen_7.0_hotfixtizen_7.0tizen_6.5accepted/tizen_unifiedaccepted/tizen_8.0_unifiedaccepted/tizen_7.0_unified_hotfixaccepted/tizen_7.0_unifiedaccepted/tizen_6.5_unified

The buffer should be big enough to hold the captured data, but it
doesn't need to be big enough to hold the entire on-the-network packet,
if we haven't captured all of it.

(backported from commit e4add0b010ed6f2180dcb05a13026242ed935334)

CVE-2020-8037

Change-Id: Ic28093fcb75e2c597aa8486bf81427fa244694a2

1 files changed, 14 insertions, 4 deletions

diff --git a/print-ppp.c b/print-ppp.c
index 8917617..33fb034 100644
--- a/print-ppp.c
+++ b/print-ppp.c
@@ -1367,19 +1367,29 @@ trunc:
 	return 0;
 }
 
+/*
+ * Un-escape RFC 1662 PPP in HDLC-like framing, with octet escapes.
+ * The length argument is the on-the-wire length, not the captured
+ * length; we can only un-escape the captured part.
+ */
 static void
 ppp_hdlc(netdissect_options *ndo,
          const u_char *p, int length)
 {
+	u_int caplen = ndo->ndo_snapend - p;
 	u_char *b, *t, c;
 	const u_char *s;
-	int i, proto;
+	u_int i;
+	int proto;
 	const void *se;
 
+	if (caplen == 0)
+		return;
+
         if (length <= 0)
                 return;
 
-	b = (u_char *)malloc(length);
+	b = (u_char *)malloc(caplen);
 	if (b == NULL)
 		return;
 
@@ -1388,10 +1398,10 @@ ppp_hdlc(netdissect_options *ndo,
 	 * Do this so that we dont overwrite the original packet
 	 * contents.
 	 */
-	for (s = p, t = b, i = length; i > 0 && ND_TTEST(*s); i--) {
+	for (s = p, t = b, i = caplen; i != 0; i--) {
 		c = *s++;
 		if (c == 0x7d) {
-			if (i <= 1 || !ND_TTEST(*s))
+			if (i <= 1)
 				break;
 			i--;
 			c = *s++ ^ 0x20;