| Message ID | 20231009230722.76268-17-dima@arista.com (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | [v14,net-next,01/23] net/tcp: Prepare tcp_md5sig_pool for TCP-AO | expand |
On Tue, Oct 10, 2023 at 1:07 AM Dmitry Safonov <dima@arista.com> wrote: > > Similarly to IPsec, RFC5925 prescribes: > ">> A TCP-AO implementation MUST default to ignore incoming ICMPv4 > messages of Type 3 (destination unreachable), Codes 2-4 (protocol > unreachable, port unreachable, and fragmentation needed -- ’hard > errors’), and ICMPv6 Type 1 (destination unreachable), Code 1 > (administratively prohibited) and Code 4 (port unreachable) intended > for connections in synchronized states (ESTABLISHED, FIN-WAIT-1, FIN- > WAIT-2, CLOSE-WAIT, CLOSING, LAST-ACK, TIME-WAIT) that match MKTs." > > A selftest (later in patch series) verifies that this attack is not > possible in this TCP-AO implementation. > > Co-developed-by: Francesco Ruggeri <fruggeri@arista.com> > Signed-off-by: Francesco Ruggeri <fruggeri@arista.com> > Co-developed-by: Salam Noureddine <noureddine@arista.com> > Signed-off-by: Salam Noureddine <noureddine@arista.com> > Signed-off-by: Dmitry Safonov <dima@arista.com> > Acked-by: David Ahern <dsahern@kernel.org> > --- > include/net/tcp_ao.h | 10 ++++++- > include/uapi/linux/snmp.h | 1 + > include/uapi/linux/tcp.h | 4 ++- > net/ipv4/proc.c | 1 + > net/ipv4/tcp_ao.c | 58 +++++++++++++++++++++++++++++++++++++++ > net/ipv4/tcp_ipv4.c | 7 +++++ > net/ipv6/tcp_ipv6.c | 7 +++++ > 7 files changed, 86 insertions(+), 2 deletions(-) > > diff --git a/include/net/tcp_ao.h b/include/net/tcp_ao.h > index 8c315c3f31da..eec38e9e6380 100644 > --- a/include/net/tcp_ao.h > +++ b/include/net/tcp_ao.h > @@ -24,6 +24,7 @@ struct tcp_ao_counters { > atomic64_t pkt_bad; > atomic64_t key_not_found; > atomic64_t ao_required; > + atomic64_t dropped_icmp; > }; > > struct tcp_ao_key { > @@ -92,7 +93,8 @@ struct tcp_ao_info { > struct tcp_ao_key *rnext_key; > struct tcp_ao_counters counters; > u32 ao_required :1, > - __unused :31; > + accept_icmps :1, > + __unused :30; > __be32 lisn; > __be32 risn; > /* Sequence Number Extension (SNE) are upper 4 bytes for SEQ, > @@ -191,6 +193,7 @@ int tcp_ao_calc_traffic_key(struct tcp_ao_key *mkt, u8 *key, void *ctx, > unsigned int len, struct tcp_sigpool *hp); > void tcp_ao_destroy_sock(struct sock *sk, bool twsk); > void tcp_ao_time_wait(struct tcp_timewait_sock *tcptw, struct tcp_sock *tp); > +bool tcp_ao_ignore_icmp(const struct sock *sk, int type, int code); > enum skb_drop_reason tcp_inbound_ao_hash(struct sock *sk, > const struct sk_buff *skb, unsigned short int family, > const struct request_sock *req, > @@ -274,6 +277,11 @@ static inline void tcp_ao_syncookie(struct sock *sk, const struct sk_buff *skb, > { > } > > +static inline bool tcp_ao_ignore_icmp(const struct sock *sk, int type, int code) > +{ > + return false; > +} > + > static inline enum skb_drop_reason tcp_inbound_ao_hash(struct sock *sk, > const struct sk_buff *skb, unsigned short int family, > const struct request_sock *req, const struct tcp_ao_hdr *aoh) > diff --git a/include/uapi/linux/snmp.h b/include/uapi/linux/snmp.h > index 06ddf4cd295c..47a6b47da66f 100644 > --- a/include/uapi/linux/snmp.h > +++ b/include/uapi/linux/snmp.h > @@ -300,6 +300,7 @@ enum > LINUX_MIB_TCPAOBAD, /* TCPAOBad */ > LINUX_MIB_TCPAOKEYNOTFOUND, /* TCPAOKeyNotFound */ > LINUX_MIB_TCPAOGOOD, /* TCPAOGood */ > + LINUX_MIB_TCPAODROPPEDICMPS, /* TCPAODroppedIcmps */ > __LINUX_MIB_MAX > }; > > diff --git a/include/uapi/linux/tcp.h b/include/uapi/linux/tcp.h > index 62543f7c5523..e4ddca6178ca 100644 > --- a/include/uapi/linux/tcp.h > +++ b/include/uapi/linux/tcp.h > @@ -404,7 +404,8 @@ struct tcp_ao_info_opt { /* setsockopt(TCP_AO_INFO) */ > set_rnext :1, /* corresponding ::rnext */ > ao_required :1, /* don't accept non-AO connects */ > set_counters :1, /* set/clear ::pkt_* counters */ > - reserved :28; /* must be 0 */ > + accept_icmps :1, /* accept incoming ICMPs */ > + reserved :27; /* must be 0 */ > __u16 reserved2; /* padding, must be 0 */ > __u8 current_key; /* KeyID to set as Current_key */ > __u8 rnext; /* KeyID to set as Rnext_key */ > @@ -412,6 +413,7 @@ struct tcp_ao_info_opt { /* setsockopt(TCP_AO_INFO) */ > __u64 pkt_bad; /* failed verification */ > __u64 pkt_key_not_found; /* could not find a key to verify */ > __u64 pkt_ao_required; /* segments missing TCP-AO sign */ > + __u64 pkt_dropped_icmp; /* ICMPs that were ignored */ > } __attribute__((aligned(8))); > > /* setsockopt(fd, IPPROTO_TCP, TCP_ZEROCOPY_RECEIVE, ...) */ > diff --git a/net/ipv4/proc.c b/net/ipv4/proc.c > index 3f643cd29cfe..5d3c9c96773e 100644 > --- a/net/ipv4/proc.c > +++ b/net/ipv4/proc.c > @@ -302,6 +302,7 @@ static const struct snmp_mib snmp4_net_list[] = { > SNMP_MIB_ITEM("TCPAOBad", LINUX_MIB_TCPAOBAD), > SNMP_MIB_ITEM("TCPAOKeyNotFound", LINUX_MIB_TCPAOKEYNOTFOUND), > SNMP_MIB_ITEM("TCPAOGood", LINUX_MIB_TCPAOGOOD), > + SNMP_MIB_ITEM("TCPAODroppedIcmps", LINUX_MIB_TCPAODROPPEDICMPS), > SNMP_MIB_SENTINEL > }; > > diff --git a/net/ipv4/tcp_ao.c b/net/ipv4/tcp_ao.c > index 801174c17853..168073cd1c89 100644 > --- a/net/ipv4/tcp_ao.c > +++ b/net/ipv4/tcp_ao.c > @@ -15,6 +15,7 @@ > > #include <net/tcp.h> > #include <net/ipv6.h> > +#include <net/icmp.h> > > int tcp_ao_calc_traffic_key(struct tcp_ao_key *mkt, u8 *key, void *ctx, > unsigned int len, struct tcp_sigpool *hp) > @@ -44,6 +45,60 @@ int tcp_ao_calc_traffic_key(struct tcp_ao_key *mkt, u8 *key, void *ctx, > return 1; > } > > +bool tcp_ao_ignore_icmp(const struct sock *sk, int type, int code) > +{ > + bool ignore_icmp = false; > + struct tcp_ao_info *ao; > + > + /* RFC5925, 7.8: > + * >> A TCP-AO implementation MUST default to ignore incoming ICMPv4 > + * messages of Type 3 (destination unreachable), Codes 2-4 (protocol > + * unreachable, port unreachable, and fragmentation needed -- ’hard > + * errors’), and ICMPv6 Type 1 (destination unreachable), Code 1 > + * (administratively prohibited) and Code 4 (port unreachable) intended > + * for connections in synchronized states (ESTABLISHED, FIN-WAIT-1, FIN- > + * WAIT-2, CLOSE-WAIT, CLOSING, LAST-ACK, TIME-WAIT) that match MKTs. > + */ > + if (READ_ONCE(sk->sk_family) == AF_INET) { You can not use sk->sk_family to make this decision. It could be AF_INET6 and yet the flow could be IPv4. (dual stack) Let the caller pass this information ? tcp_ao_ignore_icmp(sk, AF_INET, type, code); tcp_ao_ignore_icmp(sk, AF_INET6, type, code); > + if (type != ICMP_DEST_UNREACH) > + return false; > + if (code < ICMP_PROT_UNREACH || code > ICMP_FRAG_NEEDED) > + return false; > + } else { > + if (type != ICMPV6_DEST_UNREACH) > + return false; > + if (code != ICMPV6_ADM_PROHIBITED && code != ICMPV6_PORT_UNREACH) > + return false; > + } > + > + rcu_read_lock(); > + switch (sk->sk_state) { > + case TCP_TIME_WAIT: > + ao = rcu_dereference(tcp_twsk(sk)->ao_info); > + break; > + case TCP_SYN_SENT: > + case TCP_SYN_RECV: > + case TCP_LISTEN: > + case TCP_NEW_SYN_RECV: > + /* RFC5925 specifies to ignore ICMPs *only* on connections > + * in synchronized states. > + */ > + rcu_read_unlock(); > + return false; > + default: > + ao = rcu_dereference(tcp_sk(sk)->ao_info); > + } > + > + if (ao && !ao->accept_icmps) { > + ignore_icmp = true; > + __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPAODROPPEDICMPS); > + atomic64_inc(&ao->counters.dropped_icmp); > + } > + rcu_read_unlock(); > + > + return ignore_icmp; > +} >
Hi Eric, thanks once again for taking a look :) On 10/11/23 18:53, Eric Dumazet wrote: > On Tue, Oct 10, 2023 at 1:07 AM Dmitry Safonov <dima@arista.com> wrote: [..] >> +bool tcp_ao_ignore_icmp(const struct sock *sk, int type, int code) >> +{ >> + bool ignore_icmp = false; >> + struct tcp_ao_info *ao; >> + >> + /* RFC5925, 7.8: >> + * >> A TCP-AO implementation MUST default to ignore incoming ICMPv4 >> + * messages of Type 3 (destination unreachable), Codes 2-4 (protocol >> + * unreachable, port unreachable, and fragmentation needed -- ’hard >> + * errors’), and ICMPv6 Type 1 (destination unreachable), Code 1 >> + * (administratively prohibited) and Code 4 (port unreachable) intended >> + * for connections in synchronized states (ESTABLISHED, FIN-WAIT-1, FIN- >> + * WAIT-2, CLOSE-WAIT, CLOSING, LAST-ACK, TIME-WAIT) that match MKTs. >> + */ >> + if (READ_ONCE(sk->sk_family) == AF_INET) { > > You can not use sk->sk_family to make this decision. > > It could be AF_INET6 and yet the flow could be IPv4. (dual stack) > > Let the caller pass this information ? > > tcp_ao_ignore_icmp(sk, AF_INET, type, code); > > tcp_ao_ignore_icmp(sk, AF_INET6, type, code); Yes, I thought about it when added READ_ONCE(), but than probably got distracted over possible IPV6_ADDRFORM races, rather than on correctness. Looking at other places: tcp_ao_prepare_reset() seems to do a proper thing for dual stack, but I see it reads sk->sk_family twice, which needs to be addressed as well. tcp_ao_connect_init() seems to do the right thing as well, but that is hidden in tcp_ao_key_cmp(). Will fix in the next version. Thanks, Dmitry
diff --git a/include/net/tcp_ao.h b/include/net/tcp_ao.h index 8c315c3f31da..eec38e9e6380 100644 --- a/include/net/tcp_ao.h +++ b/include/net/tcp_ao.h @@ -24,6 +24,7 @@ struct tcp_ao_counters { atomic64_t pkt_bad; atomic64_t key_not_found; atomic64_t ao_required; + atomic64_t dropped_icmp; }; struct tcp_ao_key { @@ -92,7 +93,8 @@ struct tcp_ao_info { struct tcp_ao_key *rnext_key; struct tcp_ao_counters counters; u32 ao_required :1, - __unused :31; + accept_icmps :1, + __unused :30; __be32 lisn; __be32 risn; /* Sequence Number Extension (SNE) are upper 4 bytes for SEQ, @@ -191,6 +193,7 @@ int tcp_ao_calc_traffic_key(struct tcp_ao_key *mkt, u8 *key, void *ctx, unsigned int len, struct tcp_sigpool *hp); void tcp_ao_destroy_sock(struct sock *sk, bool twsk); void tcp_ao_time_wait(struct tcp_timewait_sock *tcptw, struct tcp_sock *tp); +bool tcp_ao_ignore_icmp(const struct sock *sk, int type, int code); enum skb_drop_reason tcp_inbound_ao_hash(struct sock *sk, const struct sk_buff *skb, unsigned short int family, const struct request_sock *req, @@ -274,6 +277,11 @@ static inline void tcp_ao_syncookie(struct sock *sk, const struct sk_buff *skb, { } +static inline bool tcp_ao_ignore_icmp(const struct sock *sk, int type, int code) +{ + return false; +} + static inline enum skb_drop_reason tcp_inbound_ao_hash(struct sock *sk, const struct sk_buff *skb, unsigned short int family, const struct request_sock *req, const struct tcp_ao_hdr *aoh) diff --git a/include/uapi/linux/snmp.h b/include/uapi/linux/snmp.h index 06ddf4cd295c..47a6b47da66f 100644 --- a/include/uapi/linux/snmp.h +++ b/include/uapi/linux/snmp.h @@ -300,6 +300,7 @@ enum LINUX_MIB_TCPAOBAD, /* TCPAOBad */ LINUX_MIB_TCPAOKEYNOTFOUND, /* TCPAOKeyNotFound */ LINUX_MIB_TCPAOGOOD, /* TCPAOGood */ + LINUX_MIB_TCPAODROPPEDICMPS, /* TCPAODroppedIcmps */ __LINUX_MIB_MAX }; diff --git a/include/uapi/linux/tcp.h b/include/uapi/linux/tcp.h index 62543f7c5523..e4ddca6178ca 100644 --- a/include/uapi/linux/tcp.h +++ b/include/uapi/linux/tcp.h @@ -404,7 +404,8 @@ struct tcp_ao_info_opt { /* setsockopt(TCP_AO_INFO) */ set_rnext :1, /* corresponding ::rnext */ ao_required :1, /* don't accept non-AO connects */ set_counters :1, /* set/clear ::pkt_* counters */ - reserved :28; /* must be 0 */ + accept_icmps :1, /* accept incoming ICMPs */ + reserved :27; /* must be 0 */ __u16 reserved2; /* padding, must be 0 */ __u8 current_key; /* KeyID to set as Current_key */ __u8 rnext; /* KeyID to set as Rnext_key */ @@ -412,6 +413,7 @@ struct tcp_ao_info_opt { /* setsockopt(TCP_AO_INFO) */ __u64 pkt_bad; /* failed verification */ __u64 pkt_key_not_found; /* could not find a key to verify */ __u64 pkt_ao_required; /* segments missing TCP-AO sign */ + __u64 pkt_dropped_icmp; /* ICMPs that were ignored */ } __attribute__((aligned(8))); /* setsockopt(fd, IPPROTO_TCP, TCP_ZEROCOPY_RECEIVE, ...) */ diff --git a/net/ipv4/proc.c b/net/ipv4/proc.c index 3f643cd29cfe..5d3c9c96773e 100644 --- a/net/ipv4/proc.c +++ b/net/ipv4/proc.c @@ -302,6 +302,7 @@ static const struct snmp_mib snmp4_net_list[] = { SNMP_MIB_ITEM("TCPAOBad", LINUX_MIB_TCPAOBAD), SNMP_MIB_ITEM("TCPAOKeyNotFound", LINUX_MIB_TCPAOKEYNOTFOUND), SNMP_MIB_ITEM("TCPAOGood", LINUX_MIB_TCPAOGOOD), + SNMP_MIB_ITEM("TCPAODroppedIcmps", LINUX_MIB_TCPAODROPPEDICMPS), SNMP_MIB_SENTINEL }; diff --git a/net/ipv4/tcp_ao.c b/net/ipv4/tcp_ao.c index 801174c17853..168073cd1c89 100644 --- a/net/ipv4/tcp_ao.c +++ b/net/ipv4/tcp_ao.c @@ -15,6 +15,7 @@ #include <net/tcp.h> #include <net/ipv6.h> +#include <net/icmp.h> int tcp_ao_calc_traffic_key(struct tcp_ao_key *mkt, u8 *key, void *ctx, unsigned int len, struct tcp_sigpool *hp) @@ -44,6 +45,60 @@ int tcp_ao_calc_traffic_key(struct tcp_ao_key *mkt, u8 *key, void *ctx, return 1; } +bool tcp_ao_ignore_icmp(const struct sock *sk, int type, int code) +{ + bool ignore_icmp = false; + struct tcp_ao_info *ao; + + /* RFC5925, 7.8: + * >> A TCP-AO implementation MUST default to ignore incoming ICMPv4 + * messages of Type 3 (destination unreachable), Codes 2-4 (protocol + * unreachable, port unreachable, and fragmentation needed -- ’hard + * errors’), and ICMPv6 Type 1 (destination unreachable), Code 1 + * (administratively prohibited) and Code 4 (port unreachable) intended + * for connections in synchronized states (ESTABLISHED, FIN-WAIT-1, FIN- + * WAIT-2, CLOSE-WAIT, CLOSING, LAST-ACK, TIME-WAIT) that match MKTs. + */ + if (READ_ONCE(sk->sk_family) == AF_INET) { + if (type != ICMP_DEST_UNREACH) + return false; + if (code < ICMP_PROT_UNREACH || code > ICMP_FRAG_NEEDED) + return false; + } else { + if (type != ICMPV6_DEST_UNREACH) + return false; + if (code != ICMPV6_ADM_PROHIBITED && code != ICMPV6_PORT_UNREACH) + return false; + } + + rcu_read_lock(); + switch (sk->sk_state) { + case TCP_TIME_WAIT: + ao = rcu_dereference(tcp_twsk(sk)->ao_info); + break; + case TCP_SYN_SENT: + case TCP_SYN_RECV: + case TCP_LISTEN: + case TCP_NEW_SYN_RECV: + /* RFC5925 specifies to ignore ICMPs *only* on connections + * in synchronized states. + */ + rcu_read_unlock(); + return false; + default: + ao = rcu_dereference(tcp_sk(sk)->ao_info); + } + + if (ao && !ao->accept_icmps) { + ignore_icmp = true; + __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPAODROPPEDICMPS); + atomic64_inc(&ao->counters.dropped_icmp); + } + rcu_read_unlock(); + + return ignore_icmp; +} + /* Optimized version of tcp_ao_do_lookup(): only for sockets for which * it's known that the keys in ao_info are matching peer's * family/address/VRF/etc. @@ -1083,6 +1138,7 @@ int tcp_ao_copy_all_matching(const struct sock *sk, struct sock *newsk, new_ao->lisn = htonl(tcp_rsk(req)->snt_isn); new_ao->risn = htonl(tcp_rsk(req)->rcv_isn); new_ao->ao_required = ao->ao_required; + new_ao->accept_icmps = ao->accept_icmps; if (family == AF_INET) { addr = (union tcp_ao_addr *)&newsk->sk_daddr; @@ -1789,9 +1845,11 @@ static int tcp_ao_info_cmd(struct sock *sk, unsigned short int family, atomic64_set(&ao_info->counters.pkt_bad, cmd.pkt_bad); atomic64_set(&ao_info->counters.key_not_found, cmd.pkt_key_not_found); atomic64_set(&ao_info->counters.ao_required, cmd.pkt_ao_required); + atomic64_set(&ao_info->counters.dropped_icmp, cmd.pkt_dropped_icmp); } ao_info->ao_required = cmd.ao_required; + ao_info->accept_icmps = cmd.accept_icmps; if (new_current) WRITE_ONCE(ao_info->current_key, new_current); if (new_rnext) diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c index 48fb81a8a712..772fc6347302 100644 --- a/net/ipv4/tcp_ipv4.c +++ b/net/ipv4/tcp_ipv4.c @@ -493,6 +493,8 @@ int tcp_v4_err(struct sk_buff *skb, u32 info) return -ENOENT; } if (sk->sk_state == TCP_TIME_WAIT) { + /* To increase the counter of ignored icmps for TCP-AO */ + tcp_ao_ignore_icmp(sk, type, code); inet_twsk_put(inet_twsk(sk)); return 0; } @@ -506,6 +508,11 @@ int tcp_v4_err(struct sk_buff *skb, u32 info) return 0; } + if (tcp_ao_ignore_icmp(sk, type, code)) { + sock_put(sk); + return 0; + } + bh_lock_sock(sk); /* If too many ICMPs get dropped on busy * servers this needs to be solved differently. diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c index 25911302d5e3..b604c870c493 100644 --- a/net/ipv6/tcp_ipv6.c +++ b/net/ipv6/tcp_ipv6.c @@ -395,6 +395,8 @@ static int tcp_v6_err(struct sk_buff *skb, struct inet6_skb_parm *opt, } if (sk->sk_state == TCP_TIME_WAIT) { + /* To increase the counter of ignored icmps for TCP-AO */ + tcp_ao_ignore_icmp(sk, type, code); inet_twsk_put(inet_twsk(sk)); return 0; } @@ -405,6 +407,11 @@ static int tcp_v6_err(struct sk_buff *skb, struct inet6_skb_parm *opt, return 0; } + if (tcp_ao_ignore_icmp(sk, type, code)) { + sock_put(sk); + return 0; + } + bh_lock_sock(sk); if (sock_owned_by_user(sk) && type != ICMPV6_PKT_TOOBIG) __NET_INC_STATS(net, LINUX_MIB_LOCKDROPPEDICMPS);