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bird/proto/ospf/packet.c
Ondrej Zajicek 024c310b53 Fixes broken cryptographic authentication in OSPF 
Cryptographic authentication in OSPF is defective by
design - there might be several packets independently
sent to the network (for example HELLO, LSUPD and LSACK)
where they might be reordered and that causes crypt.
sequence number error.

That can be workarounded by not incresing sequence number
too often. Now we update it only when last packet was sent
before at least one second. This can constitute a risk of
replay attacks, but RFC supposes something similar (like time
in seconds used as CSN).
2009-04-08 20:15:01 +02:00

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/*
* BIRD -- OSPF
*
* (c) 1999--2005 Ondrej Filip <feela@network.cz>
*
* Can be freely distributed and used under the terms of the GNU GPL.
*/
#include "ospf.h"
#include "nest/password.h"
#include "lib/md5.h"
void
ospf_pkt_fill_hdr(struct ospf_iface *ifa, void *buf, u8 h_type)
{
struct ospf_packet *pkt;
struct proto *p = (struct proto *) (ifa->oa->po);
pkt = (struct ospf_packet *) buf;
pkt->version = OSPF_VERSION;
pkt->type = h_type;
pkt->routerid = htonl(p->cf->global->router_id);
pkt->areaid = htonl(ifa->oa->areaid);
pkt->autype = htons(ifa->autype);
pkt->checksum = 0;
}
unsigned
ospf_pkt_maxsize(struct ospf_iface *ifa)
{
unsigned mtu = (ifa->type == OSPF_IT_VLINK) ? OSPF_VLINK_MTU : ifa->iface->mtu;
/* Can be mtu < 576? */
return ((mtu <= ifa->iface->mtu) ? mtu : ifa->iface->mtu) -
SIZE_OF_IP_HEADER - ((ifa->autype == OSPF_AUTH_CRYPT) ? OSPF_AUTH_CRYPT_SIZE : 0);
/* For virtual links use mtu=576 */
}
void
ospf_pkt_finalize(struct ospf_iface *ifa, struct ospf_packet *pkt)
{
struct password_item *passwd = NULL;
void *tail;
struct MD5Context ctxt;
char password[OSPF_AUTH_CRYPT_SIZE];
pkt->autype = htons(ifa->autype);
switch(ifa->autype)
{
case OSPF_AUTH_SIMPLE:
bzero(&pkt->u, sizeof(union ospf_auth));
passwd = password_find(ifa->passwords, 1);
if (!passwd)
{
log( L_ERR "No suitable password found for authentication" );
return;
}
password_cpy(pkt->u.password, passwd->password, sizeof(union ospf_auth));
case OSPF_AUTH_NONE:
pkt->checksum = ipsum_calculate(pkt, sizeof(struct ospf_packet) -
sizeof(union ospf_auth), (pkt + 1),
ntohs(pkt->length) -
sizeof(struct ospf_packet), NULL);
break;
case OSPF_AUTH_CRYPT:
passwd = password_find(ifa->passwords, 0);
if (!passwd)
{
log( L_ERR "No suitable password found for authentication" );
return;
}
pkt->checksum = 0;
/* Perhaps use random value to prevent replay attacks after
reboot when system does not have independent RTC? */
if (!ifa->csn)
{
ifa->csn = (u32) now;
ifa->csn_use = now;
}
/* We must have sufficient delay between sending a packet and increasing
CSN to prevent reordering of packets (in a network) with different CSNs */
if ((now - ifa->csn_use) > 1)
ifa->csn++;
ifa->csn_use = now;
pkt->u.md5.keyid = passwd->id;
pkt->u.md5.len = OSPF_AUTH_CRYPT_SIZE;
pkt->u.md5.zero = 0;
pkt->u.md5.csn = htonl(ifa->csn);
tail = ((void *)pkt) + ntohs(pkt->length);
MD5Init(&ctxt);
MD5Update(&ctxt, (char *) pkt, ntohs(pkt->length));
password_cpy(password, passwd->password, OSPF_AUTH_CRYPT_SIZE);
MD5Update(&ctxt, password, OSPF_AUTH_CRYPT_SIZE);
MD5Final(tail, &ctxt);
break;
default:
bug("Unknown authentication type");
}
}
static int
ospf_pkt_checkauth(struct ospf_neighbor *n, struct ospf_iface *ifa, struct ospf_packet *pkt, int size)
{
struct proto_ospf *po = ifa->oa->po;
struct proto *p = &po->proto;
struct password_item *pass = NULL, *ptmp;
void *tail;
char md5sum[OSPF_AUTH_CRYPT_SIZE];
char password[OSPF_AUTH_CRYPT_SIZE];
struct MD5Context ctxt;
if (pkt->autype != htons(ifa->autype))
{
OSPF_TRACE(D_PACKETS, "OSPF_auth: Method differs (%d)", ntohs(pkt->autype));
return 0;
}
if (n && (ifa != n->ifa))
{
OSPF_TRACE(D_PACKETS, "OSPF_auth: received packet from strange interface (%s/%s)",
ifa->iface->name, n->ifa->iface->name);
return 0;
}
switch(ifa->autype)
{
case OSPF_AUTH_NONE:
return 1;
break;
case OSPF_AUTH_SIMPLE:
pass = password_find(ifa->passwords, 1);
if (!pass)
{
OSPF_TRACE(D_PACKETS, "OSPF_auth: no password found");
return 0;
}
password_cpy(password, pass->password, sizeof(union ospf_auth));
if (memcmp(pkt->u.password, password, sizeof(union ospf_auth)))
{
char ppass[sizeof(union ospf_auth) + 1];
bzero(ppass, (sizeof(union ospf_auth) + 1));
memcpy(ppass, pkt->u.password, sizeof(union ospf_auth));
OSPF_TRACE(D_PACKETS, "OSPF_auth: different passwords (%s)", ppass);
return 0;
}
return 1;
break;
case OSPF_AUTH_CRYPT:
if (pkt->u.md5.len != OSPF_AUTH_CRYPT_SIZE)
{
OSPF_TRACE(D_PACKETS, "OSPF_auth: wrong size of md5 digest");
return 0;
}
if (ntohs(pkt->length) + OSPF_AUTH_CRYPT_SIZE != size)
{
OSPF_TRACE(D_PACKETS, "OSPF_auth: size mismatch (%d vs %d)",
ntohs(pkt->length) + OSPF_AUTH_CRYPT_SIZE, size);
return 0;
}
if (pkt->u.md5.zero)
{
OSPF_TRACE(D_PACKETS, "OSPF_auth: \"zero\" area is non-zero");
return 0;
}
tail = ((void *)pkt) + ntohs(pkt->length);
if (ifa->passwords)
{
WALK_LIST(ptmp, *(ifa->passwords))
{
if (pkt->u.md5.keyid != ptmp->id) continue;
if ((ptmp->accfrom > now_real) || (ptmp->accto < now_real)) continue;
pass = ptmp;
break;
}
}
if (!pass)
{
OSPF_TRACE(D_PACKETS, "OSPF_auth: no suitable md5 password found");
return 0;
}
if (n)
{
u32 rcv_csn = ntohl(pkt->u.md5.csn);
if(rcv_csn < n->csn)
{
OSPF_TRACE(D_PACKETS, "OSPF_auth: lower sequence number (rcv %d, old %d)", rcv_csn, n->csn);
return 0;
}
n->csn = rcv_csn;
}
MD5Init(&ctxt);
MD5Update(&ctxt, (char *) pkt, ntohs(pkt->length));
password_cpy(password, pass->password, OSPF_AUTH_CRYPT_SIZE);
MD5Update(&ctxt, password, OSPF_AUTH_CRYPT_SIZE);
MD5Final(md5sum, &ctxt);
if (memcmp(md5sum, tail, OSPF_AUTH_CRYPT_SIZE))
{
OSPF_TRACE(D_PACKETS, "OSPF_auth: wrong md5 digest");
return 0;
}
return 1;
break;
default:
OSPF_TRACE(D_PACKETS, "OSPF_auth: unknown auth type");
return 0;
}
}
/**
* ospf_rx_hook
* @sk: socket we received the packet. Its ignored.
* @size: size 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, int size)
{
struct ospf_packet *ps;
struct ospf_iface *ifa = (struct ospf_iface *) (sk->data);
struct proto_ospf *po = ifa->oa->po;
struct proto *p = &po->proto;
struct ospf_neighbor *n;
int osize;
char *mesg = "Bad OSPF packet from ";
struct ospf_iface *iff;
if (ifa->stub)
return (1);
ps = (struct ospf_packet *) ipv4_skip_header(sk->rbuf, &size);
if (ps == NULL)
{
log(L_ERR "%s%I - bad IP header", mesg, sk->faddr);
return 1;
}
if ((ifa->oa->areaid != 0) && (ntohl(ps->areaid) == 0))
{
WALK_LIST(iff, po->iface_list)
{
if ((iff->type == OSPF_IT_VLINK) && (iff->iface == ifa->iface) &&
(iff->voa = ifa->oa) && ipa_equal(sk->faddr, iff->vip))
{
return 1; /* Packet is for VLINK */
}
}
}
DBG("%s: RX_Hook called on interface %s.\n", p->name, sk->iface->name);
osize = ntohs(ps->length);
if ((unsigned) size < sizeof(struct ospf_packet))
{
log(L_ERR "%s%I - too short (%u bytes)", mesg, sk->faddr, size);
return 1;
}
if ((osize > size) || (osize != (4 * (osize / 4))))
{
log(L_ERR "%s%I - size field does not match (%d/%d)", mesg, sk->faddr, ntohs(ps->length), size );
return 1;
}
if (ps->version != OSPF_VERSION)
{
log(L_ERR "%s%I - version %u", mesg, sk->faddr, ps->version);
return 1;
}
if ((ps->autype != htons(OSPF_AUTH_CRYPT)) &&
(!ipsum_verify(ps, 16, (void *) ps + sizeof(struct ospf_packet),
ntohs(ps->length) - sizeof(struct ospf_packet), NULL)))
{
log(L_ERR "%s%I - bad checksum", mesg, sk->faddr);
return 1;
}
if (ntohl(ps->areaid) != ifa->oa->areaid)
{
log(L_ERR "%s%I - different area %ld", mesg, sk->faddr, ntohl(ps->areaid));
return 1;
}
if (ntohl(ps->routerid) == p->cf->global->router_id)
{
log(L_ERR "%s%I - received my own router ID!", mesg, sk->faddr);
return 1;
}
if (ntohl(ps->routerid) == 0)
{
log(L_ERR "%s%I - router id = 0.0.0.0", mesg, sk->faddr);
return 1;
}
if (((unsigned) size > sk->rbsize) || (ntohs(ps->length) > sk->rbsize))
{
log(L_ERR "%s%I - packet is too large (%d-%d vs %d)",
mesg, sk->faddr, size, ntohs(ps->length), sk->rbsize);
return 1;
}
n = find_neigh(ifa, ntohl(((struct ospf_packet *) ps)->routerid));
if(!n && (ps->type != HELLO_P))
{
OSPF_TRACE(D_PACKETS, "Received non-hello packet from uknown neighbor (%I)", sk->faddr);
return 1;
}
if (!ospf_pkt_checkauth(n, ifa, ps, size))
{
log(L_ERR "%s%I - authentification failed", mesg, sk->faddr);
return 1;
}
/* Dump packet
pu8=(u8 *)(sk->rbuf+5*4);
for(i=0;i<ntohs(ps->length);i+=4)
DBG("%s: received %u,%u,%u,%u\n",p->name, pu8[i+0], pu8[i+1], pu8[i+2],
pu8[i+3]);
DBG("%s: received size: %u\n",p->name,size);
*/
switch (ps->type)
{
case HELLO_P:
DBG("%s: Hello received.\n", p->name);
ospf_hello_receive((struct ospf_hello_packet *) ps, ifa, n, sk->faddr);
break;
case DBDES_P:
DBG("%s: Database description received.\n", p->name);
ospf_dbdes_receive((struct ospf_dbdes_packet *) ps, ifa, n);
break;
case LSREQ_P:
DBG("%s: Link state request received.\n", p->name);
ospf_lsreq_receive((struct ospf_lsreq_packet *) ps, ifa, n);
break;
case LSUPD_P:
DBG("%s: Link state update received.\n", p->name);
ospf_lsupd_receive((struct ospf_lsupd_packet *) ps, ifa, n);
break;
case LSACK_P:
DBG("%s: Link state ack received.\n", p->name);
ospf_lsack_receive((struct ospf_lsack_packet *) ps, ifa, n);
break;
default:
log(L_ERR "%s%I - wrong type %u", mesg, sk->faddr, ps->type);
return 1;
};
return 1;
}
void
ospf_tx_hook(sock * sk)
{
struct ospf_iface *ifa= (struct ospf_iface *) (sk->data);
struct proto *p = (struct proto *) (ifa->oa->po);
log(L_ERR "%s: TX_Hook called on interface %s\n", p->name, sk->iface->name);
}
void
ospf_err_hook(sock * sk, int err)
{
struct ospf_iface *ifa= (struct ospf_iface *) (sk->data);
struct proto *p = (struct proto *) (ifa->oa->po);
log(L_ERR "%s: Err_Hook called on interface %s with err=%d\n",
p->name, sk->iface->name, err);
}
void
ospf_send_to_agt(sock * sk, struct ospf_iface *ifa, u8 state)
{
struct ospf_neighbor *n;
WALK_LIST(n, ifa->neigh_list) if (n->state >= state)
ospf_send_to(sk, n->ip, ifa);
}
void
ospf_send_to_bdr(sock * sk, struct ospf_iface *ifa)
{
if (!ipa_equal(ifa->drip, IPA_NONE))
ospf_send_to(sk, ifa->drip, ifa);
if (!ipa_equal(ifa->bdrip, IPA_NONE))
ospf_send_to(sk, ifa->bdrip, ifa);
}
void
ospf_send_to(sock *sk, ip_addr ip, struct ospf_iface *ifa)
{
struct ospf_packet *pkt = (struct ospf_packet *) sk->tbuf;
int len = ntohs(pkt->length) + ((ifa->autype == OSPF_AUTH_CRYPT) ? OSPF_AUTH_CRYPT_SIZE : 0);
ospf_pkt_finalize(ifa, pkt);
if (sk->tbuf != sk->tpos)
log(L_ERR "Aiee, old packet was overwritted in TX buffer");
if (ipa_equal(ip, IPA_NONE))
sk_send(sk, len);
else
sk_send_to(sk, len, ip, OSPF_PROTO);
}
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