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Changes handling of AS_PATH_CONFED_* segments in AS_PATH.
Although standard says that if we receive AS_PATH_CONFED_* (and we are not a part of a confederation) segment, we should drop session, nobody does that and it is unwise to do that. Now we drop session just in case that peer ASN is in AS_PATH_CONFED_* segment (to detect peer that considers BIRD as a part of its confederation).
This commit is contained in:
Ondrej Zajicek
parent
4323099da9
commit
29c430f856
@ -55,25 +55,97 @@ bgp_format_origin(eattr *a, byte *buf, int buflen)
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}
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static int
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bgp_check_path(byte *a, int len, int bs, int errcode)
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path_segment_contains(byte *p, int bs, u32 asn)
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{
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while (len)
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int i;
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int len = p[1];
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p += 2;
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for(i=0; i<len; i++)
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{
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DBG("Path segment %02x %02x\n", a[0], a[1]);
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if (len < 2 ||
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(a[0] != AS_PATH_SET && a[0] != AS_PATH_SEQUENCE) ||
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bs * a[1] + 2 > len)
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return errcode;
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len -= bs * a[1] + 2;
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a += bs * a[1] + 2;
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u32 asn2 = (bs == 4) ? get_u32(p) : get_u16(p);
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if (asn2 == asn)
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return 1;
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p += bs;
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}
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return 0;
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}
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/* Validates path attribute, removes AS_CONFED_* segments, and also returns path length */
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static int
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bgp_check_as_path(struct bgp_proto *p, byte *a, int len)
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validate_path(struct bgp_proto *p, int as_path, int bs, byte *idata, unsigned int *ilength)
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{
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return bgp_check_path(a, len, p->as4_session ? 4 : 2, 11);
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int res = 0;
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u8 *a, *dst;
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int len, plen, copy;
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dst = a = idata;
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len = *ilength;
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while (len)
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{
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if (len < 2)
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return -1;
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plen = 2 + bs * a[1];
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if (len < plen)
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return -1;
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switch (a[0])
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{
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case AS_PATH_SET:
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copy = 1;
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res++;
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break;
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case AS_PATH_SEQUENCE:
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copy = 1;
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res += a[1];
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break;
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case AS_PATH_CONFED_SEQUENCE:
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case AS_PATH_CONFED_SET:
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if (as_path && path_segment_contains(a, bs, p->remote_as))
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{
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log(L_WARN "%s: AS_CONFED_* segment with peer ASN found, misconfigured confederation?", p->p.name);
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return -1;
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}
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log(L_WARN "%s: %s_PATH attribute contains AS_CONFED_* segment, skipping segment",
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p->p.name, as_path ? "AS" : "AS4");
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copy = 0;
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break;
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default:
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return -1;
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}
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if (copy)
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{
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if (dst != a)
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memmove(dst, a, plen);
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dst += plen;
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}
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len -= plen;
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a += plen;
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}
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*ilength = dst - idata;
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return res;
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}
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static inline int
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validate_as_path(struct bgp_proto *p, byte *a, int *len)
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{
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return validate_path(p, 1, p->as4_session ? 4 : 2, a, len);
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}
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static inline int
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validate_as4_path(struct bgp_proto *p, struct adata *path)
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{
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return validate_path(p, 0, 4, path->data, &path->length);
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}
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static int
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@ -160,7 +232,7 @@ static struct attr_desc bgp_attr_table[] = {
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{ "origin", 1, BAF_TRANSITIVE, EAF_TYPE_INT, 1, /* BA_ORIGIN */
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bgp_check_origin, bgp_format_origin },
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{ "as_path", -1, BAF_TRANSITIVE, EAF_TYPE_AS_PATH, 1, /* BA_AS_PATH */
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bgp_check_as_path, NULL },
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NULL, NULL }, /* is checked by validate_as_path() as a special case */
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{ "next_hop", 4, BAF_TRANSITIVE, EAF_TYPE_IP_ADDRESS, 1, /* BA_NEXT_HOP */
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bgp_check_next_hop, NULL },
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{ "med", 4, BAF_OPTIONAL, EAF_TYPE_INT, 1, /* BA_MULTI_EXIT_DISC */
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@ -1061,73 +1133,6 @@ as4_aggregator_valid(struct adata *aggr)
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return 0;
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}
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static int
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as4_path_sanitize_and_get_length(struct adata *path)
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{
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int res = 0;
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u8 *p, *dst;
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int len, plen, copy;
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dst = p = path->data;
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len = path->length;
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while (len)
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{
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if (len <= 2) /* We do not allow empty segments */
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goto inconsistent_path;
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switch (p[0])
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{
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case AS_PATH_SET:
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plen = 2 + 4 * p[1];
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copy = 1;
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res++;
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break;
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case AS_PATH_SEQUENCE:
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plen = 2 + 4 * p[1];
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copy = 1;
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res += p[1];
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break;
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case AS_PATH_CONFED_SEQUENCE:
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case AS_PATH_CONFED_SET:
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log(L_WARN "BGP: AS4_PATH attribute contains AS_CONFED_* segment, skipping segment");
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plen = 2 + 4 * p[1];
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copy = 0;
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break;
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default:
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goto unknown_segment;
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}
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if (len < plen)
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goto inconsistent_path;
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if (copy)
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{
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if (dst != p)
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memmove(dst, p, plen);
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dst += plen;
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}
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len -= plen;
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p += plen;
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}
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path->length = dst - path->data;
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return res;
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inconsistent_path:
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log(L_WARN "BGP: AS4_PATH attribute is inconsistent, skipping attribute");
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return -1;
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unknown_segment:
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log(L_WARN "BGP: AS4_PATH attribute contains unknown segment, skipping attribute");
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return -1;
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}
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/* Reconstruct 4B AS_PATH and AGGREGATOR according to RFC 4893 4.2.3 */
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static void
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@ -1141,7 +1146,7 @@ bgp_reconstruct_4b_atts(struct bgp_proto *p, rta *a, struct linpool *pool)
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if (a4 && !as4_aggregator_valid(a4->u.ptr))
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{
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log(L_WARN "BGP: AS4_AGGREGATOR attribute is invalid, skipping attribute");
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log(L_WARN "%s: AS4_AGGREGATOR attribute is invalid, skipping attribute", p->p.name);
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a4 = NULL;
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a4_removed = 1;
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}
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@ -1177,15 +1182,18 @@ bgp_reconstruct_4b_atts(struct bgp_proto *p, rta *a, struct linpool *pool)
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a2->u.ptr = bgp_aggregator_convert_to_new(a2->u.ptr, pool);
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if ((a2_as == AS_TRANS) && !a4_removed)
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log(L_WARN "BGP: AGGREGATOR attribute contain AS_TRANS, but AS4_AGGREGATOR is missing");
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log(L_WARN "%s: AGGREGATOR attribute contain AS_TRANS, but AS4_AGGREGATOR is missing", p->p.name);
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}
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}
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else
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if (a4)
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log(L_WARN "BGP: AS4_AGGREGATOR attribute received, but AGGREGATOR attribute is missing");
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log(L_WARN "%s: AS4_AGGREGATOR attribute received, but AGGREGATOR attribute is missing", p->p.name);
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int p2_len = as_path_getlen(p2->u.ptr);
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int p4_len = p4 ? as4_path_sanitize_and_get_length(p4->u.ptr) : -1;
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int p4_len = p4 ? validate_as4_path(p, p4->u.ptr) : -1;
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if (p4 && (p4_len < 0))
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log(L_WARN "%s: AS4_PATH attribute is malformed, skipping attribute", p->p.name);
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if ((p4_len <= 0) || (p2_len < p4_len))
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p2->u.ptr = bgp_merge_as_paths(p2->u.ptr, NULL, AS_PATH_MAXLEN, pool);
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@ -1200,7 +1208,7 @@ bgp_remove_as4_attrs(struct bgp_proto *p, rta *a)
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unsigned id2 = EA_CODE(EAP_BGP, BA_AS4_AGGREGATOR);
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ea_list **el = &(a->eattrs);
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/* We know that ea_lists constructed in bgp_decode_attrs have one attribute per ea_list struct */
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/* We know that ea_lists constructed in bgp_decode attrs have one attribute per ea_list struct */
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while (*el != NULL)
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{
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unsigned fid = (*el)->attrs[0].id;
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@ -1302,6 +1310,12 @@ bgp_decode_attrs(struct bgp_conn *conn, byte *attr, unsigned int len, struct lin
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if (errcode < 0)
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continue;
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}
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else if (code == BA_AS_PATH)
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{
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/* Special case as it might also trim the attribute */
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if (validate_as_path(bgp, z, &l) < 0)
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{ errcode = 11; goto err; }
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}
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type = desc->type;
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}
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else /* Unknown attribute */
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@ -1310,6 +1324,11 @@ bgp_decode_attrs(struct bgp_conn *conn, byte *attr, unsigned int len, struct lin
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{ errcode = 2; goto err; }
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type = EAF_TYPE_OPAQUE;
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}
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// Only OPTIONAL and TRANSITIVE attributes may have non-zero PARTIAL flag
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// if (!((flags & BAF_OPTIONAL) && (flags & BAF_TRANSITIVE)) && (flags & BAF_PARTIAL))
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// { errcode = 4; goto err; }
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seen[code/8] |= (1 << (code%8));
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ea = lp_alloc(pool, sizeof(ea_list) + sizeof(eattr));
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ea->next = a->eattrs;
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