From: Francois-Xavier Le Bail <devel.fx.lebail@orange.fr>
Date: Thu, 27 Apr 2023 11:19:34 +0000 (+0200)
Subject: PPP: Check if there is some data to hexdump
X-Git-Url: https://git.tcpdump.org/tcpdump/commitdiff_plain/ef2869ecb72f85fbb452094b45fa53743a23d086?ds=inline

PPP: Check if there is some data to hexdump

This may avoid this error:
Dissector error: print_unknown_data() called with pointer past end of
packet

Add a test file showing the problem.
---

diff --git a/print-ppp.c b/print-ppp.c
index aba243dd..38505355 100644
--- a/print-ppp.c
+++ b/print-ppp.c
@@ -1131,7 +1131,7 @@ print_ipcp_config_options(netdissect_options *ndo,
 			print_unknown_data(ndo, p + 2, "\n\t    ", len - 2);
 		break;
 	}
-	if (ndo->ndo_vflag > 1)
+	if (ndo->ndo_vflag > 1 && ND_TTEST_LEN(p + 2, len - 2))
 		print_unknown_data(ndo, p + 2, "\n\t    ", len - 2); /* exclude TLV header */
 	return len;
 
diff --git a/tests/TESTLIST b/tests/TESTLIST
index 00576f70..bc23b548 100644
--- a/tests/TESTLIST
+++ b/tests/TESTLIST
@@ -190,6 +190,9 @@ babel_pad1      babel_pad1.pcap        babel_pad1.out
 babel_rtt       babel_rtt.pcap         babel_rtt.out   -v
 babel_rfc6126bis  babel_rfc6126bis.pcap  babel_rfc6126bis.out     -v
 
+# PPP tests
+ppp_error_hexdump ppp_error_hexdump.pcap ppp_error_hexdump.out -vv
+
 # PPPoE tests
 pppoe           pppoe.pcap             pppoe.out
 pppoes          pppoes.pcap            pppoes.out
diff --git a/tests/ppp_error_hexdump.out b/tests/ppp_error_hexdump.out
new file mode 100644
index 00000000..b75a5642
--- /dev/null
+++ b/tests/ppp_error_hexdump.out
@@ -0,0 +1,19 @@
+    1  [Error converting time] unknown PPP protocol (0x7e80): IPCP, Conf-Request (0x01), id 0, length 48
+	encoded length 45 (=Option(s) length 41)
+	0x0000:  8021 0100 002d
+	  unknown Option (0x66), length 4
+	    0x0000:  006c
+	  unknown Option (0x72), length 8
+	    0x0000:  0055 00d4 c3b2
+	  unknown Option (0xa1), length 2
+	  IP-Comp Option (0x02), length 32: IP Header Compression (0x61):
+	    TCP Space 514, non-TCP Space 514, maxPeriod 514, maxTime 514, maxHdr 52702
+	      Suboptions, length 18
+		Enhanced RTP-Compression Suboption #2, length 1
+		RTP-Compression Suboption #1, length 1
+		RTP-Compression Suboption #1, length 1
+		RTP-Compression Suboption #1, length 1
+		RTP-Compression Suboption #1, length 1
+		RTP-Compression Suboption #1, length 1
+		RTP-Compression Suboption #1, length 1
+		RTP-Compression Suboption #1, length 10 [remaining options length 27 < 32] (invalid)
diff --git a/tests/ppp_error_hexdump.pcap b/tests/ppp_error_hexdump.pcap
new file mode 100644
index 00000000..3ad0a32b
Binary files /dev/null and b/tests/ppp_error_hexdump.pcap differ