From 81877287a99e55b47a7045efa76945f368e90917 Mon Sep 17 00:00:00 2001 From: Kristof Provost Date: Sat, 20 May 2023 19:43:49 +0200 Subject: [PATCH] if_ovpn: ensure we never re-use sequence numbers if_ovpn already notified userpsace when there was a risk of sequence number re-use, but it trusted userspace to actually rotate the key. Convert the internal sequence number counter to 64 bits so we can detect overflows and then refuse to send packets. Event: BSDCan 2023 Reviewed by: Leon Dang Sponsored by: Rubicon Communications, LLC ("Netgate") Differential Revision: https://reviews.freebsd.org/D40187 --- sys/net/if_ovpn.c | 22 ++++++++++++++++++---- 1 file changed, 18 insertions(+), 4 deletions(-) diff --git a/sys/net/if_ovpn.c b/sys/net/if_ovpn.c index 3aec073c052e..49c8c8e9677a 100644 --- a/sys/net/if_ovpn.c +++ b/sys/net/if_ovpn.c @@ -93,7 +93,7 @@ struct ovpn_kkey_dir { * strictly higher than this. */ uint32_t rx_seq; - uint32_t tx_seq; + uint64_t tx_seq; /* Seen packets, relative to rx_seq. bit(0) will always be 0. */ uint64_t rx_window; @@ -1830,6 +1830,7 @@ ovpn_transmit_to_peer(struct ifnet *ifp, struct mbuf *m, struct ovpn_softc *sc; struct cryptop *crp; uint32_t af, seq; + uint64_t seq64; size_t len, ovpn_hdr_len; int tunnel_len; int ret; @@ -1873,11 +1874,24 @@ ovpn_transmit_to_peer(struct ifnet *ifp, struct mbuf *m, ohdr->opcode |= key->peerid; ohdr->opcode = htonl(ohdr->opcode); - seq = atomic_fetchadd_32(&peer->keys[OVPN_KEY_SLOT_PRIMARY].encrypt->tx_seq, 1); - if (seq == OVPN_SEQ_ROTATE) + seq64 = atomic_fetchadd_64(&peer->keys[OVPN_KEY_SLOT_PRIMARY].encrypt->tx_seq, 1); + if (seq64 == OVPN_SEQ_ROTATE) { ovpn_notify_key_rotation(sc, peer); + } else if (seq64 > UINT32_MAX) { + /* We've wrapped, give up on this packet. */ + if (_ovpn_lock_trackerp != NULL) + OVPN_RUNLOCK(sc); + OVPN_COUNTER_ADD(sc, nomem_data_pkts_out, 1); - seq = htonl(seq); + /* Let's avoid (very unlikely, but still) wraparounds of the + * 64-bit counter taking us back to 0. */ + atomic_set_64(&peer->keys[OVPN_KEY_SLOT_PRIMARY].encrypt->tx_seq, + UINT32_MAX); + + return (ENOBUFS); + } + + seq = htonl(seq64 & UINT32_MAX); ohdr->seq = seq; OVPN_PEER_COUNTER_ADD(peer, pkt_out, 1);