[Oisf-devel] how to suricata alert when wrong ip length?

[Victor Julien]

We have a special (so far undocumented) directive called "decode-event".
It can match against "events" set by the decoder.

In this case the sig would probably be:

alert ip any any -> any any (msg:"WARNING: IP dgm len < IP Hdr len!";
decode-event:"ipv4.iplen_smaller_than_hlen"; sid:12345; rev:1;)

The full list of currently supported "decode events" is (see
detect-decode-event.h):

    { "ipv4.pkt_too_small", IPV4_PKT_TOO_SMALL, },
    { "ipv4.hlen_too_small", IPV4_HLEN_TOO_SMALL, },
    { "ipv4.iplen_smaller_than_hlen", IPV4_IPLEN_SMALLER_THAN_HLEN, },
    { "ipv4.trunc_pkt", IPV4_TRUNC_PKT, },
    { "ipv4.opt_invalid", IPV4_OPT_INVALID, },
    { "ipv4.opt_invalid_len", IPV4_OPT_INVALID_LEN, },
    { "ipv4.opt_malformed", IPV4_OPT_MALFORMED, },
    { "ipv4.opt_pad_required", IPV4_OPT_PAD_REQUIRED, },
    { "ipv4.opt_eol_required", IPV4_OPT_EOL_REQUIRED, },
    { "ipv4.opt_duplicate", IPV4_OPT_DUPLICATE, },
    { "ipv4.opt_unknown", IPV4_OPT_UNKNOWN, },
    { "ipv4.wrong_ip_version", IPV4_WRONG_IP_VER, },
    { "ipv6.pkt_too_small", IPV6_PKT_TOO_SMALL, },
    { "ipv6.trunc_pkt", IPV6_TRUNC_PKT, },
    { "ipv6.trunc_exthdr", IPV6_TRUNC_EXTHDR, },
    { "ipv6.exthdr_dupl_fh", IPV6_EXTHDR_DUPL_FH, },
    { "ipv6.exthdr_dupl_rh", IPV6_EXTHDR_DUPL_RH, },
    { "ipv6.exthdr_dupl_hh", IPV6_EXTHDR_DUPL_HH, },
    { "ipv6.exthdr_dupl_dh", IPV6_EXTHDR_DUPL_DH, },
    { "ipv6.exthdr_dupl_ah", IPV6_EXTHDR_DUPL_AH, },
    { "ipv6.exthdr_dupl_eh", IPV6_EXTHDR_DUPL_EH, },
    { "ipv6.exthdr_invalid_optlen", IPV6_EXTHDR_INVALID_OPTLEN, },
    { "ipv6.wrong_ip_version", IPV6_WRONG_IP_VER, },
    { "icmpv4.pkt_too_small", ICMPV4_PKT_TOO_SMALL, },
    { "icmpv4.unknown_type", ICMPV4_UNKNOWN_TYPE, },
    { "icmpv4.unknown_code", ICMPV4_UNKNOWN_CODE, },
    { "icmpv4.ipv4_trunc_pkt", ICMPV4_IPV4_TRUNC_PKT, },
    { "icmpv4.ipv4_unknown_ver", ICMPV4_IPV4_UNKNOWN_VER, },
    { "icmpv6.unknown_type", ICMPV6_UNKNOWN_TYPE,},
    { "icmpv6.unknown_code", ICMPV6_UNKNOWN_CODE,},
    { "icmpv6.pkt_too_small", ICMPV6_PKT_TOO_SMALL,},
    { "icmpv6.ipv6_unknown_version", ICMPV6_IPV6_UNKNOWN_VER,},
    { "icmpv6.ipv6_trunc_pkt", ICMPV6_IPV6_TRUNC_PKT,},
    { "tcp.pkt_too_small", TCP_PKT_TOO_SMALL, },
    { "tcp.hlen_too_small", TCP_HLEN_TOO_SMALL, },
    { "tcp.invalid_optlen", TCP_INVALID_OPTLEN, },
    { "tcp.opt_invalid_len", TCP_OPT_INVALID_LEN, },
    { "tcp.opt_duplicate", TCP_OPT_DUPLICATE, },
    { "udp.pkt_too_small", UDP_PKT_TOO_SMALL, },
    { "udp.hlen_too_small", UDP_HLEN_TOO_SMALL, },
    { "udp.hlen_invalid", UDP_HLEN_INVALID, },
    { "sll.pkt_too_small", SLL_PKT_TOO_SMALL, },
    { "ethernet.pkt_too_small", ETHERNET_PKT_TOO_SMALL, },
    { "ppp.pkt_too_small", PPP_PKT_TOO_SMALL, },
    { "ppp.vju_pkt_too_small", PPPVJU_PKT_TOO_SMALL, },
    { "ppp.ip4_pkt_too_small", PPPIPV4_PKT_TOO_SMALL, },
    { "ppp.ip6_pkt_too_small", PPPIPV6_PKT_TOO_SMALL, },
    { "ppp.wrong_type", PPP_WRONG_TYPE, }, /** unknown & invalid protocol */
    { "ppp.unsup_proto", PPP_UNSUP_PROTO, }, /** unsupported but valid
protocol */
    { "pppoe.pkt_too_small", PPPOE_PKT_TOO_SMALL, },
    { "pppoe.wrong_code", PPPOE_WRONG_CODE, },
    { "pppoe.malformed_tags", PPPOE_MALFORMED_TAGS, },
    { "gre.pkt_too_small", GRE_PKT_TOO_SMALL, },
    { "gre.wrong_version", GRE_WRONG_VERSION, },
    { "gre.version0_recur", GRE_VERSION0_RECUR, },
    { "gre.version0_flags", GRE_VERSION0_FLAGS, },
    { "gre.version0_hdr_too_big", GRE_VERSION0_HDR_TOO_BIG, },
    { "gre.version1_chksum", GRE_VERSION1_CHKSUM, },
    { "gre.version1_route", GRE_VERSION1_ROUTE, },
    { "gre.version1_ssr", GRE_VERSION1_SSR, },
    { "gre.version1_recur", GRE_VERSION1_RECUR, },
    { "gre.version1_flags", GRE_VERSION1_FLAGS, },
    { "gre.version1_no_key", GRE_VERSION1_NO_KEY, },
    { "gre.version1_wrong_protocol", GRE_VERSION1_WRONG_PROTOCOL, },
    { "gre.version1_malformed_sre_hdr", GRE_VERSION1_MALFORMED_SRE_HDR, },
    { "gre.version1_hdr_too_big", GRE_VERSION1_HDR_TOO_BIG, },
    { "ipraw.wrong_ip_version",IPRAW_INVALID_IPV, },
    { "vlan.hlen_too_small",VLAN_HEADER_TOO_SMALL, },
    { "vlan.unknown_type",VLAN_UNKNOWN_TYPE, },

Cheers,
Victor

rmkml wrote:
> Hi,
> No alert with joigned pcap file, how to detect wrong ip length with
> suricata please?
> Snort alert with:
>  06/04-10:18:28.332871  [**] [116:3:1] (snort_decoder) WARNING: IP dgm
> len < IP Hdr len! [**]
> If you want, Im open a ticket?
> Sorry if it's a stupid question!
> Regards
> Rmkml
> 
> 
> ------------------------------------------------------------------------
> 
> _______________________________________________
> Oisf-devel mailing list
> Oisf-devel at openinfosecfoundation.org
> http://lists.openinfosecfoundation.org/mailman/listinfo/oisf-devel


-- 
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Victor Julien
http://www.inliniac.net/
PGP: http://www.inliniac.net/victorjulien.asc
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