From: hannes Date: Tue, 12 Dec 2006 10:51:35 +0000 (+0000) Subject: rework on the ICMP MPLS extension code: X-Git-Tag: tcpdump-3.9.7~45 X-Git-Url: https://git.tcpdump.org/tcpdump/commitdiff_plain/b26ef9253b31c95de929e6fad21a3c5cdb98132f rework on the ICMP MPLS extension code: - preserve the snapend pointer as it may get overwritten by calling the IP printer - protect against infinite loops inside the MPLS extension printer. - detect present of an MPLS extension header by introducing a length field to the ICMP header as per draft-bonica-internet-icmp-08. --- diff --git a/print-icmp.c b/print-icmp.c index 8ac34d78..8ce59373 100644 --- a/print-icmp.c +++ b/print-icmp.c @@ -21,7 +21,7 @@ #ifndef lint static const char rcsid[] _U_ = - "@(#) $Header: /tcpdump/master/tcpdump/print-icmp.c,v 1.81.2.2 2005-07-01 16:13:37 hannes Exp $ (LBL)"; + "@(#) $Header: /tcpdump/master/tcpdump/print-icmp.c,v 1.81.2.3 2006-12-12 10:51:35 hannes Exp $ (LBL)"; #endif #ifdef HAVE_CONFIG_H @@ -62,20 +62,12 @@ struct icmp { u_int16_t icd_seq; } ih_idseq; u_int32_t ih_void; - - /* ICMP_UNREACH_NEEDFRAG -- Path MTU Discovery (RFC1191) */ - struct ih_pmtu { - u_int16_t ipm_void; - u_int16_t ipm_nextmtu; - } ih_pmtu; } icmp_hun; #define icmp_pptr icmp_hun.ih_pptr #define icmp_gwaddr icmp_hun.ih_gwaddr #define icmp_id icmp_hun.ih_idseq.icd_id #define icmp_seq icmp_hun.ih_idseq.icd_seq #define icmp_void icmp_hun.ih_void -#define icmp_pmvoid icmp_hun.ih_pmtu.ipm_void -#define icmp_nextmtu icmp_hun.ih_pmtu.ipm_nextmtu union { struct id_ts { u_int32_t its_otime; @@ -86,12 +78,6 @@ struct icmp { struct ip idi_ip; /* options and then 64 bits of data */ } id_ip; - struct mpls_ext { - u_int8_t legacy_header[128]; /* extension header starts 128 bytes after ICMP header */ - u_int8_t version_res[2]; - u_int8_t checksum[2]; - u_int8_t data[1]; - } mpls_ext; u_int32_t id_mask; u_int8_t id_data[1]; } icmp_dun; @@ -101,9 +87,6 @@ struct icmp { #define icmp_ip icmp_dun.id_ip.idi_ip #define icmp_mask icmp_dun.id_mask #define icmp_data icmp_dun.id_data -#define icmp_mpls_ext_version icmp_dun.mpls_ext.version_res -#define icmp_mpls_ext_checksum icmp_dun.mpls_ext.checksum -#define icmp_mpls_ext_data icmp_dun.mpls_ext.data }; #define ICMP_MPLS_EXT_EXTRACT_VERSION(x) (((x)&0xf0)>>4) @@ -118,7 +101,7 @@ struct icmp { * ip header length. */ #define ICMP_MINLEN 8 /* abs minimum */ -#define ICMP_EXTD_MINLEN (156 - sizeof (struct ip)) /* draft-bonica-icmp-mpls-02 */ +#define ICMP_EXTD_MINLEN (156 - sizeof (struct ip)) /* draft-bonica-internet-icmp-08 */ #define ICMP_TSLEN (8 + 3 * sizeof (u_int32_t)) /* timestamp */ #define ICMP_MASKLEN 12 /* address mask */ #define ICMP_ADVLENMIN (8 + sizeof (struct ip) + 8) /* min */ @@ -173,7 +156,9 @@ struct icmp { (type) == ICMP_IREQ || (type) == ICMP_IREQREPLY || \ (type) == ICMP_MASKREQ || (type) == ICMP_MASKREPLY) #define ICMP_MPLS_EXT_TYPE(type) \ - ((type) == ICMP_UNREACH || (type) == ICMP_TIMXCEED) + ((type) == ICMP_UNREACH || \ + (type) == ICMP_TIMXCEED || \ + (type) == ICMP_PARAMPROB) /* rfc1700 */ #ifndef ICMP_UNREACH_NET_UNKNOWN #define ICMP_UNREACH_NET_UNKNOWN 6 /* destination net unknown */ @@ -276,7 +261,48 @@ struct id_rdiscovery { u_int32_t ird_pref; }; -/* draft-bonica-icmp-mpls-02 */ +/* + * draft-bonica-internet-icmp-08 + * + * The Destination Unreachable, Time Exceeded + * and Parameter Problem messages are slighly changed as per + * the above draft. A new Length field gets added to give + * the caller an idea about the length of the piggypacked + * IP packet before the MPLS extension header starts. + * + * The Length field represents length of the padded "original datagram" + * field measured in 32-bit words. + * + * 0 1 2 3 + * 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 + * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + * | Type | Code | Checksum | + * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + * | unused | Length | unused | + * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + * | Internet Header + leading octets of original datagram | + * | | + * | // | + * | | + * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + */ + +struct icmp_ext_t { + u_int8_t icmp_type; + u_int8_t icmp_code; + u_int8_t icmp_checksum[2]; + u_int8_t icmp_reserved; + u_int8_t icmp_length; + u_int8_t icmp_reserved2[2]; + u_int8_t icmp_ext_legacy_header[128]; /* extension header starts 128 bytes after ICMP header */ + u_int8_t icmp_ext_version_res[2]; + u_int8_t icmp_ext_checksum[2]; + u_int8_t icmp_ext_data[1]; +}; + +struct icmp_mpls_ext_common_header_t { +}; + struct icmp_mpls_ext_object_header_t { u_int8_t length[2]; u_int8_t class_num; @@ -312,17 +338,20 @@ icmp_print(const u_char *bp, u_int plen, const u_char *bp2, int fragmented) { char *cp; const struct icmp *dp; + const struct icmp_ext_t *ext_dp; const struct ip *ip; const char *str, *fmt; const struct ip *oip; const struct udphdr *ouh; const u_int8_t *obj_tptr; u_int32_t raw_label; + const u_char *snapend_save; const struct icmp_mpls_ext_object_header_t *icmp_mpls_ext_object_header; u_int hlen, dport, mtu, obj_tlen, obj_class_num, obj_ctype; char buf[MAXHOSTNAMELEN + 100]; dp = (struct icmp *)bp; + ext_dp = (struct icmp_ext_t *)bp; ip = (struct ip *)bp2; str = buf; @@ -544,35 +573,48 @@ icmp_print(const u_char *bp, u_int plen, const u_char *bp2, int fragmented) } } } + + /* + * print the remnants of the IP packet. + * save the snaplength as this may get overidden in the IP printer. + */ if (vflag >= 1 && !ICMP_INFOTYPE(dp->icmp_type)) { bp += 8; (void)printf("\n\t"); ip = (struct ip *)bp; snaplen = snapend - bp; + snapend_save = snapend; ip_print(gndo, bp, EXTRACT_16BITS(&ip->ip_len)); + snapend = snapend_save; } - if (vflag >= 1 && plen > ICMP_EXTD_MINLEN && ICMP_MPLS_EXT_TYPE(dp->icmp_type)) { + /* + * Check if the extended ICMP header indicates that there is + * MPLS extension header present for the "interesting" ICMP types. + */ + if (vflag >= 1 && plen > ICMP_EXTD_MINLEN && + ext_dp->icmp_length && ICMP_MPLS_EXT_TYPE(dp->icmp_type)) { - TCHECK(*(dp->icmp_mpls_ext_version)); - printf("\n\tMPLS extension v%u",ICMP_MPLS_EXT_EXTRACT_VERSION(*(dp->icmp_mpls_ext_version))); + TCHECK(*ext_dp); + printf("\n\tMPLS extension v%u", + ICMP_MPLS_EXT_EXTRACT_VERSION(*(ext_dp->icmp_ext_version_res))); /* * Sanity checking of the header. */ - if (ICMP_MPLS_EXT_EXTRACT_VERSION(*(dp->icmp_mpls_ext_version)) != ICMP_MPLS_EXT_VERSION) { + if (ICMP_MPLS_EXT_EXTRACT_VERSION(*(ext_dp->icmp_ext_version_res)) != + ICMP_MPLS_EXT_VERSION) { printf(" packet not supported"); return; } hlen = plen - ICMP_EXTD_MINLEN; - TCHECK2(*(dp->icmp_mpls_ext_checksum), 2); printf(", checksum 0x%04x (unverified), length %u", /* FIXME */ - EXTRACT_16BITS(dp->icmp_mpls_ext_checksum), + EXTRACT_16BITS(ext_dp->icmp_ext_checksum), hlen); hlen -= 4; /* subtract common header size */ - obj_tptr = (u_int8_t *)dp->icmp_mpls_ext_data; + obj_tptr = (u_int8_t *)ext_dp->icmp_ext_data; while (hlen > sizeof(struct icmp_mpls_ext_object_header_t)) { @@ -590,8 +632,12 @@ icmp_print(const u_char *bp, u_int plen, const u_char *bp2, int fragmented) obj_tlen); hlen-=sizeof(struct icmp_mpls_ext_object_header_t); /* length field includes tlv header */ - if (obj_tlen < sizeof(struct icmp_mpls_ext_object_header_t)) - break; + + /* infinite loop protection */ + if ((obj_class_num == 0) || + (obj_tlen < sizeof(struct icmp_mpls_ext_object_header_t))) { + return; + } obj_tlen-=sizeof(struct icmp_mpls_ext_object_header_t); switch (obj_class_num) {