bird/proto/ospf/packet.c
Ondrej Zajicek (work) 4727d1db9d OSPF: Support of authentication trailer for OSPFv3
Implement RFC 7166, crypthographic authentication for OSPFv3
analogous to authentication used for OSPFv2.
2018-04-25 15:54:53 +02:00

667 lines
18 KiB
C

/*
* BIRD -- OSPF
*
* (c) 1999--2005 Ondrej Filip <feela@network.cz>
* (c) 2009--2014 Ondrej Zajicek <santiago@crfreenet.org>
* (c) 2009--2014 CZ.NIC z.s.p.o.
*
* Can be freely distributed and used under the terms of the GNU GPL.
*/
#include "ospf.h"
#include "nest/password.h"
#include "lib/md5.h"
#include "lib/mac.h"
#include "lib/socket.h"
void
ospf_pkt_fill_hdr(struct ospf_iface *ifa, void *buf, u8 h_type)
{
struct ospf_proto *p = ifa->oa->po;
struct ospf_packet *pkt;
pkt = (struct ospf_packet *) buf;
pkt->version = ospf_get_version(p);
pkt->type = h_type;
pkt->length = htons(ospf_pkt_maxsize(ifa));
pkt->routerid = htonl(p->router_id);
pkt->areaid = htonl(ifa->oa->areaid);
pkt->checksum = 0;
pkt->instance_id = ifa->instance_id;
pkt->autype = ospf_is_v2(p) ? ifa->autype : 0;
}
/* We assume OSPFv2 in ospf_pkt_finalize() */
static void
ospf_pkt_finalize2(struct ospf_iface *ifa, struct ospf_packet *pkt, uint *plen)
{
struct ospf_proto *p = ifa->oa->po;
struct password_item *pass = NULL;
union ospf_auth2 *auth = (void *) (pkt + 1);
memset(auth, 0, sizeof(union ospf_auth2));
/* Compatibility note: auth may contain anything if autype is
none, but nonzero values do not work with Mikrotik OSPF */
pkt->checksum = 0;
pkt->autype = ifa->autype;
switch (ifa->autype)
{
case OSPF_AUTH_SIMPLE:
pass = password_find(ifa->passwords, 1);
if (!pass)
{
log(L_ERR "No suitable password found for authentication");
return;
}
strncpy(auth->password, pass->password, sizeof(auth->password));
case OSPF_AUTH_NONE:
{
void *body = (void *) (auth + 1);
uint blen = *plen - sizeof(struct ospf_packet) - sizeof(union ospf_auth2);
pkt->checksum = ipsum_calculate(pkt, sizeof(struct ospf_packet), body, blen, NULL);
}
break;
case OSPF_AUTH_CRYPT:
pass = password_find(ifa->passwords, 0);
if (!pass)
{
log(L_ERR "%s: No suitable password found for authentication", p->p.name);
return;
}
/* Perhaps use random value to prevent replay attacks after
reboot when system does not have independent RTC? */
if (!ifa->csn)
{
ifa->csn = (u32) (current_real_time() TO_S);
ifa->csn_use = current_time();
}
/* We must have sufficient delay between sending a packet and increasing
CSN to prevent reordering of packets (in a network) with different CSNs */
if ((current_time() - ifa->csn_use) > 1 S)
ifa->csn++;
ifa->csn_use = current_time();
uint auth_len = mac_type_length(pass->alg);
byte *auth_tail = ((byte *) pkt + *plen);
*plen += auth_len;
ASSERT(*plen < ifa->sk->tbsize);
auth->c32.zero = 0;
auth->c32.keyid = pass->id;
auth->c32.len = auth_len;
auth->c32.csn = htonl(ifa->csn);
/* Append key for keyed hash, append padding for HMAC (RFC 5709 3.3) */
if (pass->alg < ALG_HMAC)
strncpy(auth_tail, pass->password, auth_len);
else
memset32(auth_tail, HMAC_MAGIC, auth_len / 4);
mac_fill(pass->alg, pass->password, pass->length, (byte *) pkt, *plen, auth_tail);
break;
default:
bug("Unknown authentication type");
}
}
/*
* Return an extra packet size that should be added to a final packet size
*/
static void
ospf_pkt_finalize3(struct ospf_iface *ifa, struct ospf_packet *pkt, uint *plen, ip_addr src)
{
struct ospf_proto *p = ifa->oa->po;
struct ospf_auth3 *auth = (void *) ((byte *) pkt + *plen);
pkt->checksum = 0;
pkt->autype = 0;
if (ifa->autype != OSPF_AUTH_CRYPT)
return;
struct password_item *pass = password_find(ifa->passwords, 0);
if (!pass)
{
log(L_ERR "%s: No suitable password found for authentication", p->p.name);
return;
}
/* FIXME: Ensure persistence */
p->csn64++;
uint mac_len = mac_type_length(pass->alg);
uint auth_len = sizeof(struct ospf_auth3) + mac_len;
*plen += auth_len;
ASSERT(*plen < ifa->sk->tbsize);
memset(auth, 0, sizeof(struct ospf_auth3));
auth->type = htons(OSPF3_AUTH_HMAC);
auth->length = htons(auth_len);
auth->reserved = 0;
auth->sa_id = htons(pass->id);
put_u64(&auth->csn, p->csn64);
/* Initialize with src IP address padded with HMAC_MAGIC */
put_ip6(auth->data, ipa_to_ip6(src));
memset32(auth->data + 16, HMAC_MAGIC, (mac_len - 16) / 4);
/* Attach OSPFv3 Cryptographic Protocol ID to the key */
uint pass_len = pass->length + 2;
byte *pass_key = alloca(pass_len);
memcpy(pass_key, pass->password, pass->length);
put_u16(pass_key + pass->length, OSPF3_CRYPTO_ID);
mac_fill(pass->alg, pass_key, pass_len, (byte *) pkt, *plen, auth->data);
}
static int
ospf_pkt_checkauth2(struct ospf_neighbor *n, struct ospf_iface *ifa, struct ospf_packet *pkt, uint len)
{
struct ospf_proto *p = ifa->oa->po;
union ospf_auth2 *auth = (void *) (pkt + 1);
struct password_item *pass = NULL;
const char *err_dsc = NULL;
uint err_val = 0;
uint plen = ntohs(pkt->length);
u8 autype = pkt->autype;
if (autype != ifa->autype)
DROP("authentication method mismatch", autype);
switch (autype)
{
case OSPF_AUTH_NONE:
return 1;
case OSPF_AUTH_SIMPLE:
pass = password_find(ifa->passwords, 1);
if (!pass)
DROP1("no password found");
if (!password_verify(pass, auth->password, sizeof(auth->password)))
DROP("wrong password", pass->id);
return 1;
case OSPF_AUTH_CRYPT:
pass = password_find_by_id(ifa->passwords, auth->c32.keyid);
if (!pass)
DROP("no suitable password found", auth->c32.keyid);
uint auth_len = mac_type_length(pass->alg);
if (plen + auth->c32.len > len)
DROP("packet length mismatch", len);
if (auth->c32.len != auth_len)
DROP("wrong authentication length", auth->c32.len);
u32 rcv_csn = ntohl(auth->c32.csn);
if (n && (rcv_csn < n->csn))
// DROP("lower sequence number", rcv_csn);
{
/* We want to report both new and old CSN */
LOG_PKT_AUTH("Authentication failed for nbr %R on %s - "
"lower sequence number (rcv %u, old %u)",
n->rid, ifa->ifname, rcv_csn, n->csn);
return 0;
}
byte *auth_tail = ((byte *) pkt) + plen;
byte *auth_data = alloca(auth_len);
memcpy(auth_data, auth_tail, auth_len);
/* Append key for keyed hash, append padding for HMAC (RFC 5709 3.3) */
if (pass->alg < ALG_HMAC)
strncpy(auth_tail, pass->password, auth_len);
else
memset32(auth_tail, HMAC_MAGIC, auth_len / 4);
if (!mac_verify(pass->alg, pass->password, pass->length,
(byte *) pkt, plen + auth_len, auth_data))
DROP("wrong authentication code", pass->id);
if (n)
n->csn = rcv_csn;
return 1;
default:
bug("Unknown authentication type");
}
drop:
LOG_PKT_AUTH("Authentication failed for nbr %R on %s - %s (%u)",
(n ? n->rid : ntohl(pkt->routerid)), ifa->ifname, err_dsc, err_val);
return 0;
}
static int
ospf_pkt_checkauth3(struct ospf_neighbor *n, struct ospf_iface *ifa, struct ospf_packet *pkt, uint len, ip_addr src)
{
struct ospf_proto *p = ifa->oa->po;
const char *err_dsc = NULL;
uint err_val = 0;
uint plen = ntohs(pkt->length);
uint opts, lls_present, auth_present;
/*
* When autentication is not enabled, ignore the trailer. This is different
* from OSPFv2, but it is necessary in order to support migration modes. Note
* that regular authenticated packets do not have valid checksum and will be
* dropped by OS on non-authenticated ifaces.
*/
if (ifa->autype != OSPF_AUTH_CRYPT)
return 1;
switch(pkt->type)
{
case HELLO_P:
opts = ospf_hello3_options(pkt);
lls_present = opts & OPT_L_V3;
auth_present = opts & OPT_AT;
break;
case DBDES_P:
opts = ospf_dbdes3_options(pkt);
lls_present = opts & OPT_L_V3;
auth_present = opts & OPT_AT;
break;
default:
lls_present = 0;
auth_present = n->options & OPT_AT;
}
if (!auth_present)
DROP1("missing authentication trailer");
if (lls_present)
{
if ((plen + sizeof(struct ospf_lls)) > len)
DROP("packet length mismatch", len);
struct ospf_lls *lls = (void *) ((byte *) pkt + plen);
plen += ntohs(lls->length);
}
if ((plen + sizeof(struct ospf_auth3)) > len)
DROP("packet length mismatch", len);
struct ospf_auth3 *auth = (void *) ((byte *) pkt + plen);
uint rcv_auth_type = ntohs(auth->type);
if (rcv_auth_type != OSPF3_AUTH_HMAC)
DROP("authentication method mismatch", rcv_auth_type);
uint rcv_auth_len = ntohs(auth->length);
if (plen + rcv_auth_len > len)
DROP("packet length mismatch", len);
uint rcv_key_id = ntohs(auth->sa_id);
struct password_item *pass = password_find_by_id(ifa->passwords, rcv_key_id);
if (!pass)
DROP("no suitable password found", rcv_key_id);
uint mac_len = mac_type_length(pass->alg);
if (rcv_auth_len != (sizeof(struct ospf_auth3) + mac_len))
DROP("wrong authentication length", rcv_auth_len);
uint pt = pkt->type - 1;
u64 rcv_csn = get_u64(&auth->csn);
if (n && (rcv_csn <= n->csn64[pt]))
{
/* We want to report both new and old CSN */
LOG_PKT_AUTH("Authentication failed for nbr %R on %s - "
"lower sequence number (rcv %u, old %u)",
n->rid, ifa->ifname, (uint) rcv_csn, (uint) n->csn64[pt]);
return 0;
}
/* Save the received authentication data */
byte *auth_data = alloca(mac_len);
memcpy(auth_data, auth->data, mac_len);
/* Initialize with src IP address padded with HMAC_MAGIC */
put_ip6(auth->data, ipa_to_ip6(src));
memset32(auth->data + 16, HMAC_MAGIC, (mac_len - 16) / 4);
/* Attach OSPFv3 Cryptographic Protocol ID to the key */
uint pass_len = pass->length + 2;
byte *pass_key = alloca(pass_len);
memcpy(pass_key, pass->password, pass->length);
put_u16(pass_key + pass->length, OSPF3_CRYPTO_ID);
if (!mac_verify(pass->alg, pass_key, pass_len,
(byte *) pkt, plen + rcv_auth_len, auth_data))
DROP("wrong authentication code", pass->id);
if (n)
n->csn64[pt] = rcv_csn;
return 1;
drop:
LOG_PKT_AUTH("Authentication failed for nbr %R on %s - %s (%u)",
(n ? n->rid : ntohl(pkt->routerid)), ifa->ifname, err_dsc, err_val);
return 0;
}
/**
* ospf_rx_hook
* @sk: socket we received the packet.
* @len: length of the packet
*
* This is the entry point for messages from neighbors. Many checks (like
* authentication, checksums, size) are done before the packet is passed to
* non generic functions.
*/
int
ospf_rx_hook(sock *sk, uint len)
{
/* We want just packets from sk->iface. Unfortunately, on BSD we cannot filter
out other packets at kernel level and we receive all packets on all sockets */
if (sk->lifindex != sk->iface->index)
return 1;
DBG("OSPF: RX hook called (iface %s, src %I, dst %I)\n",
sk->iface->name, sk->faddr, sk->laddr);
/* Initially, the packet is associated with the 'master' iface */
struct ospf_iface *ifa = sk->data;
struct ospf_proto *p = ifa->oa->po;
const char *err_dsc = NULL;
uint err_val = 0;
/* Should not happen */
if (ifa->state <= OSPF_IS_LOOP)
return 1;
int src_local, dst_local, dst_mcast;
src_local = ipa_in_netX(sk->faddr, &ifa->addr->prefix);
dst_local = ipa_equal(sk->laddr, ifa->addr->ip);
dst_mcast = ipa_equal(sk->laddr, ifa->all_routers) || ipa_equal(sk->laddr, ifa->des_routers);
if (ospf_is_v2(p))
{
/* First, we eliminate packets with strange address combinations.
* In OSPFv2, they might be for other ospf_ifaces (with different IP
* prefix) on the same real iface, so we don't log it. We enforce
* that (src_local || dst_local), therefore we are eliminating all
* such cases.
*/
if (dst_mcast && !src_local)
return 1;
if (!dst_mcast && !dst_local)
return 1;
/* Ignore my own broadcast packets */
if (ifa->cf->real_bcast && ipa_equal(sk->faddr, ifa->addr->ip))
return 1;
}
else
{
/* In OSPFv3, src_local and dst_local mean link-local.
* RFC 5340 says that local (non-vlink) packets use
* link-local src address, but does not enforce it. Strange.
*/
if (dst_mcast && !src_local)
LOG_PKT_WARN("Multicast packet received from non-link-local %I via %s",
sk->faddr, ifa->ifname);
}
/* Second, we check packet length, checksum, and the protocol version */
struct ospf_packet *pkt = (void *) sk_rx_buffer(sk, &len);
if (pkt == NULL)
DROP("bad IP header", len);
if (len < sizeof(struct ospf_packet))
DROP("too short", len);
if (pkt->version != ospf_get_version(p))
DROP("version mismatch", pkt->version);
uint plen = ntohs(pkt->length);
if ((plen < sizeof(struct ospf_packet)) || ((plen % 4) != 0))
DROP("invalid length", plen);
if (sk->flags & SKF_TRUNCATED)
{
/* If we have dynamic buffers and received truncated message, we expand RX buffer */
uint bs = plen + 256;
bs = BIRD_ALIGN(bs, 1024);
if (!ifa->cf->rx_buffer && (bs > sk->rbsize))
sk_set_rbsize(sk, bs);
DROP("truncated", plen);
}
if (plen > len)
DROP("length mismatch", plen);
if (ospf_is_v2(p) && (pkt->autype != OSPF_AUTH_CRYPT))
{
uint hlen = sizeof(struct ospf_packet) + sizeof(union ospf_auth2);
uint blen = plen - hlen;
void *body = ((void *) pkt) + hlen;
if (!ipsum_verify(pkt, sizeof(struct ospf_packet), body, blen, NULL))
DROP("invalid checksum", ntohs(pkt->checksum));
}
/* Third, we resolve associated iface and handle vlinks. */
u32 areaid = ntohl(pkt->areaid);
u32 rid = ntohl(pkt->routerid);
u8 instance_id = pkt->instance_id;
if (areaid == ifa->oa->areaid)
{
/* Matching area ID */
if (instance_id != ifa->instance_id)
return 1;
/* It is real iface, source should be local (in OSPFv2) */
if (ospf_is_v2(p) && !src_local)
DROP1("strange source address");
goto found;
}
else if ((areaid == 0) && !dst_mcast)
{
/* Backbone area ID and possible vlink packet */
if ((p->areano == 1) || !oa_is_ext(ifa->oa))
return 1;
struct ospf_iface *iff = NULL;
WALK_LIST(iff, p->iface_list)
{
if ((iff->type == OSPF_IT_VLINK) &&
(iff->voa == ifa->oa) &&
(iff->instance_id == instance_id) &&
(iff->vid == rid))
{
/* Vlink should be UP */
if (iff->state != OSPF_IS_PTP)
return 1;
ifa = iff;
goto found;
}
}
/*
* Cannot find matching vlink. It is either misconfigured vlink; NBMA or
* PtMP with misconfigured area ID, or packet for some other instance (that
* is possible even if instance_id == ifa->instance_id, because it may be
* also vlink packet in the other instance, which is different namespace).
*/
return 1;
}
else
{
/* Non-matching area ID but cannot be vlink packet */
if (instance_id != ifa->instance_id)
return 1;
DROP("area mismatch", areaid);
}
found:
if (ifa->stub) /* This shouldn't happen */
return 1;
if (ipa_equal(sk->laddr, ifa->des_routers) && (ifa->sk_dr == 0))
return 1;
/* TTL check must be done after instance dispatch */
if (ifa->check_ttl && (sk->rcv_ttl < 255))
DROP("wrong TTL", sk->rcv_ttl);
if (rid == p->router_id)
DROP1("my own router ID");
if (rid == 0)
DROP1("zero router ID");
/* In OSPFv2, neighbors are identified by either IP or Router ID, based on network type */
uint t = ifa->type;
struct ospf_neighbor *n;
if (ospf_is_v2(p) && ((t == OSPF_IT_BCAST) || (t == OSPF_IT_NBMA) || (t == OSPF_IT_PTMP)))
n = find_neigh_by_ip(ifa, sk->faddr);
else
n = find_neigh(ifa, rid);
if (!n && (pkt->type != HELLO_P))
{
OSPF_TRACE(D_PACKETS, "Non-HELLO packet received from unknown nbr %R on %s, src %I",
rid, ifa->ifname, sk->faddr);
return 1;
}
/* Check packet type here, ospf_pkt_checkauth3() expects valid values */
if (pkt->type < HELLO_P || pkt->type > LSACK_P)
DROP("invalid packet type", pkt->type);
/* ospf_pkt_checkauth() has its own error logging */
if ((ospf_is_v2(p) ?
!ospf_pkt_checkauth2(n, ifa, pkt, len) :
!ospf_pkt_checkauth3(n, ifa, pkt, len, sk->faddr)))
return 1;
switch (pkt->type)
{
case HELLO_P:
ospf_receive_hello(pkt, ifa, n, sk->faddr);
break;
case DBDES_P:
ospf_receive_dbdes(pkt, ifa, n);
break;
case LSREQ_P:
ospf_receive_lsreq(pkt, ifa, n);
break;
case LSUPD_P:
ospf_receive_lsupd(pkt, ifa, n);
break;
case LSACK_P:
ospf_receive_lsack(pkt, ifa, n);
break;
};
return 1;
drop:
LOG_PKT("Bad packet from %I via %s - %s (%u)",
sk->faddr, ifa->ifname, err_dsc, err_val);
return 1;
}
/*
void
ospf_tx_hook(sock * sk)
{
struct ospf_iface *ifa= (struct ospf_iface *) (sk->data);
// struct proto *p = (struct proto *) (ifa->oa->p);
log(L_ERR "OSPF: TX hook called on %s", ifa->ifname);
}
*/
void
ospf_err_hook(sock * sk, int err)
{
struct ospf_iface *ifa = (struct ospf_iface *) (sk->data);
struct ospf_proto *p = ifa->oa->po;
log(L_ERR "%s: Socket error on %s: %M", p->p.name, ifa->ifname, err);
}
void
ospf_verr_hook(sock *sk, int err)
{
struct ospf_proto *p = (struct ospf_proto *) (sk->data);
log(L_ERR "%s: Vlink socket error: %M", p->p.name, err);
}
void
ospf_send_to(struct ospf_iface *ifa, ip_addr dst)
{
sock *sk = ifa->sk;
struct ospf_packet *pkt = (struct ospf_packet *) sk->tbuf;
uint plen = ntohs(pkt->length);
if (ospf_is_v2(ifa->oa->po))
ospf_pkt_finalize2(ifa, pkt, &plen);
else
ospf_pkt_finalize3(ifa, pkt, &plen, sk->saddr);
int done = sk_send_to(sk, plen, dst, 0);
if (!done)
log(L_WARN "OSPF: TX queue full on %s", ifa->ifname);
}
void
ospf_send_to_agt(struct ospf_iface *ifa, u8 state)
{
struct ospf_neighbor *n;
WALK_LIST(n, ifa->neigh_list)
if (n->state >= state)
ospf_send_to(ifa, n->ip);
}
void
ospf_send_to_bdr(struct ospf_iface *ifa)
{
if (ipa_nonzero2(ifa->drip))
ospf_send_to(ifa, ifa->drip);
if (ipa_nonzero2(ifa->bdrip))
ospf_send_to(ifa, ifa->bdrip);
}