lkml.org 
[lkml]   [2023]   [Jul]   [21]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH v8.1 net-next 16/23] net/tcp: Ignore specific ICMPs for TCP-AO connections
    Date
    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>
    ---
    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 | 61 +++++++++++++++++++++++++++++++++++++++
    net/ipv4/tcp_ipv4.c | 5 ++++
    net/ipv6/tcp_ipv6.c | 4 +++
    7 files changed, 84 insertions(+), 2 deletions(-)

    diff --git a/include/net/tcp_ao.h b/include/net/tcp_ao.h
    index 801dca405df7..cb16af2a9f39 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 {
    @@ -93,7 +94,8 @@ 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,
    @@ -188,6 +190,7 @@ 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(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,
    @@ -266,6 +269,11 @@ static inline void tcp_ao_syncookie(struct sock *sk, const struct sk_buff *skb,
    {
    }

    +static inline bool tcp_ao_ignore_icmp(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 3fe0612ec59a..ca7ed18ce67b 100644
    --- a/include/uapi/linux/tcp.h
    +++ b/include/uapi/linux/tcp.h
    @@ -392,7 +392,8 @@ 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 */
    @@ -400,6 +401,7 @@ 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 9ee7fc9f6a76..4bde58ede63a 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 +45,63 @@ int tcp_ao_calc_traffic_key(struct tcp_ao_key *mkt, u8 *key, void *ctx,
    return 1;
    }

    +bool tcp_ao_ignore_icmp(struct sock *sk, int type, int code)
    +{
    + struct tcp_ao_info *ao;
    + bool ignore_icmp = false;
    +
    + /* 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 (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 (sk->sk_family == AF_INET6) {
    + if (type != ICMPV6_DEST_UNREACH)
    + return false;
    + if (code != ICMPV6_ADM_PROHIBITED && code != ICMPV6_PORT_UNREACH)
    + return false;
    + } else {
    + WARN_ON_ONCE(1);
    + 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/port/VRF/etc.
    @@ -1044,6 +1102,7 @@ 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;
    @@ -1764,9 +1823,11 @@ 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 37497dec5eb9..054897a13575 100644
    --- a/net/ipv4/tcp_ipv4.c
    +++ b/net/ipv4/tcp_ipv4.c
    @@ -494,6 +494,8 @@ 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;
    }
    @@ -508,6 +510,9 @@ int tcp_v4_err(struct sk_buff *skb, u32 info)
    }

    bh_lock_sock(sk);
    + if (tcp_ao_ignore_icmp(sk, type, code))
    + goto out;
    +
    /* If too many ICMPs get dropped on busy
    * servers this needs to be solved differently.
    * We do take care of PMTU discovery (RFC1191) special case :
    diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
    index 873ce0d72f34..9a427c0d48ab 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;
    }
    @@ -406,6 +408,8 @@ static int tcp_v6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
    }

    bh_lock_sock(sk);
    + if (tcp_ao_ignore_icmp(sk, type, code))
    + goto out;
    if (sock_owned_by_user(sk) && type != ICMPV6_PKT_TOOBIG)
    __NET_INC_STATS(net, LINUX_MIB_LOCKDROPPEDICMPS);

    --
    2.41.0
    \
     
     \ /
      Last update: 2023-07-21 18:24    [W:4.288 / U:0.028 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site