[1/6] batctl: tcpdump: Fix missing sanity check for batman-adv header

Message ID 20240127-tcpdump_fuzzing-v1-1-fbc1e1d3fec1@narfation.org (mailing list archive)
State Accepted, archived
Delegated to: Simon Wunderlich
Series batctl: tcpdump: Fix problems detected during fuzzing |

Commit Message

Sven Eckelmann Jan. 27, 2024, 12:48 p.m. UTC
  parse_eth_hdr() is assuming that every ETH_P_BATMAN ethernet packet has a
valid, minimal batman-adv header (packet_type, version, ttl) attached. But
it doesn't actually check if the received buffer has enough bytes to access
the two bytes packet_type + version. So it is possible that it tries to
read outside of the received data.

Fixes: 3bdfc388e74b ("implement simple tcpdump, first only batman packets")
Signed-off-by: Sven Eckelmann <sven@narfation.org>
 tcpdump.c | 3 +++
 1 file changed, 3 insertions(+)


diff --git a/tcpdump.c b/tcpdump.c
index d340af9..d15c32e 100644
--- a/tcpdump.c
+++ b/tcpdump.c
@@ -1167,6 +1167,9 @@  static void parse_eth_hdr(unsigned char *packet_buff, ssize_t buff_len, int read
 			dump_vlan(packet_buff, buff_len, read_opt, time_printed);
 	case ETH_P_BATMAN:
+		/* check for batman-adv packet_type + version */
+		LEN_CHECK(buff_len, sizeof(*eth_hdr) + 2, "BAT HEADER")
 		batman_ogm_packet = (struct batadv_ogm_packet *)(packet_buff + ETH_HLEN);
 		if ((read_opt & COMPAT_FILTER) &&