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    Subject[PATCH v8 04/23] net/tcp: Prevent TCP-MD5 with TCP-AO being set
    Date
    Be as conservative as possible: if there is TCP-MD5 key for a given peer
    regardless of L3 interface - don't allow setting TCP-AO key for the same
    peer. According to RFC5925, TCP-AO is supposed to replace TCP-MD5 and
    there can't be any switch between both on any connected tuple.
    Later it can be relaxed, if there's a use, but in the beginning restrict
    any intersection.

    Note: it's still should be possible to set both TCP-MD5 and TCP-AO keys
    on a listening socket for *different* peers.

    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.h | 43 +++++++++++++++++++++++++++++++++++++--
    include/net/tcp_ao.h | 15 ++++++++++++++
    net/ipv4/tcp_ao.c | 40 ++++++++++++++++++++++++++++++++++++
    net/ipv4/tcp_ipv4.c | 14 ++++++++++---
    net/ipv4/tcp_output.c | 47 +++++++++++++++++++++++++++++++++++++++++++
    net/ipv6/tcp_ao.c | 17 ++++++++++++++++
    net/ipv6/tcp_ipv6.c | 26 ++++++++++++++++++++----
    7 files changed, 193 insertions(+), 9 deletions(-)

    diff --git a/include/net/tcp.h b/include/net/tcp.h
    index 9697a4596158..73e886ca4532 100644
    --- a/include/net/tcp.h
    +++ b/include/net/tcp.h
    @@ -1702,6 +1702,7 @@ int tcp_md5_key_copy(struct sock *sk, const union tcp_md5_addr *addr,

    int tcp_md5_do_del(struct sock *sk, const union tcp_md5_addr *addr,
    int family, u8 prefixlen, int l3index, u8 flags);
    +void tcp_clear_md5_list(struct sock *sk);
    struct tcp_md5sig_key *tcp_v4_md5_lookup(const struct sock *sk,
    const struct sock *addr_sk);

    @@ -1710,14 +1711,23 @@ struct tcp_md5sig_key *tcp_v4_md5_lookup(const struct sock *sk,
    extern struct static_key_false_deferred tcp_md5_needed;
    struct tcp_md5sig_key *__tcp_md5_do_lookup(const struct sock *sk, int l3index,
    const union tcp_md5_addr *addr,
    - int family);
    + int family, bool any_l3index);
    static inline struct tcp_md5sig_key *
    tcp_md5_do_lookup(const struct sock *sk, int l3index,
    const union tcp_md5_addr *addr, int family)
    {
    if (!static_branch_unlikely(&tcp_md5_needed.key))
    return NULL;
    - return __tcp_md5_do_lookup(sk, l3index, addr, family);
    + return __tcp_md5_do_lookup(sk, l3index, addr, family, false);
    +}
    +
    +static inline struct tcp_md5sig_key *
    +tcp_md5_do_lookup_any_l3index(const struct sock *sk,
    + const union tcp_md5_addr *addr, int family)
    +{
    + if (!static_branch_unlikely(&tcp_md5_needed.key))
    + return NULL;
    + return __tcp_md5_do_lookup(sk, 0, addr, family, true);
    }

    enum skb_drop_reason
    @@ -1735,6 +1745,13 @@ tcp_md5_do_lookup(const struct sock *sk, int l3index,
    return NULL;
    }

    +static inline struct tcp_md5sig_key *
    +tcp_md5_do_lookup_any_l3index(const struct sock *sk,
    + const union tcp_md5_addr *addr, int family)
    +{
    + return NULL;
    +}
    +
    static inline enum skb_drop_reason
    tcp_inbound_md5_hash(const struct sock *sk, const struct sk_buff *skb,
    const void *saddr, const void *daddr,
    @@ -2096,6 +2113,9 @@ struct tcp_sock_af_ops {
    int optname,
    sockptr_t optval,
    int optlen);
    + struct tcp_ao_key *(*ao_lookup)(const struct sock *sk,
    + struct sock *addr_sk,
    + int sndid, int rcvid);
    #endif
    };

    @@ -2508,4 +2528,23 @@ static inline u64 tcp_transmit_time(const struct sock *sk)
    return 0;
    }

    +static inline bool tcp_ao_required(struct sock *sk, const void *saddr,
    + int family)
    +{
    +#ifdef CONFIG_TCP_AO
    + struct tcp_ao_info *ao_info;
    + struct tcp_ao_key *ao_key;
    +
    + ao_info = rcu_dereference_check(tcp_sk(sk)->ao_info,
    + lockdep_sock_is_held(sk));
    + if (!ao_info)
    + return false;
    +
    + ao_key = tcp_ao_do_lookup(sk, saddr, family, -1, -1, 0);
    + if (ao_info->ao_required || ao_key)
    + return true;
    +#endif
    + return false;
    +}
    +
    #endif /* _TCP_H */
    diff --git a/include/net/tcp_ao.h b/include/net/tcp_ao.h
    index 1739116c6902..1c24b586c876 100644
    --- a/include/net/tcp_ao.h
    +++ b/include/net/tcp_ao.h
    @@ -93,12 +93,27 @@ struct tcp_ao_info {
    int tcp_parse_ao(struct sock *sk, int cmd, unsigned short int family,
    sockptr_t optval, int optlen);
    void tcp_ao_destroy_sock(struct sock *sk);
    +struct tcp_ao_key *tcp_ao_do_lookup(const struct sock *sk,
    + const union tcp_ao_addr *addr,
    + int family, int sndid, int rcvid, u16 port);
    /* ipv4 specific functions */
    int tcp_v4_parse_ao(struct sock *sk, int optname, sockptr_t optval, int optlen);
    +struct tcp_ao_key *tcp_v4_ao_lookup(const struct sock *sk, struct sock *addr_sk,
    + int sndid, int rcvid);
    /* ipv6 specific functions */
    +struct tcp_ao_key *tcp_v6_ao_lookup(const struct sock *sk,
    + struct sock *addr_sk,
    + int sndid, int rcvid);
    int tcp_v6_parse_ao(struct sock *sk, int cmd,
    sockptr_t optval, int optlen);
    #else
    +static inline struct tcp_ao_key *tcp_ao_do_lookup(const struct sock *sk,
    + const union tcp_ao_addr *addr,
    + int family, int sndid, int rcvid, u16 port)
    +{
    + return NULL;
    +}
    +
    static inline void tcp_ao_destroy_sock(struct sock *sk)
    {
    }
    diff --git a/net/ipv4/tcp_ao.c b/net/ipv4/tcp_ao.c
    index 2b2696e24dcc..c2be72beab70 100644
    --- a/net/ipv4/tcp_ao.c
    +++ b/net/ipv4/tcp_ao.c
    @@ -171,6 +171,14 @@ void tcp_ao_destroy_sock(struct sock *sk)
    kfree_rcu(ao, rcu);
    }

    +struct tcp_ao_key *tcp_v4_ao_lookup(const struct sock *sk, struct sock *addr_sk,
    + int sndid, int rcvid)
    +{
    + union tcp_ao_addr *addr = (union tcp_ao_addr *)&addr_sk->sk_daddr;
    +
    + return tcp_ao_do_lookup(sk, addr, AF_INET, sndid, rcvid, 0);
    +}
    +
    static bool tcp_ao_can_set_current_rnext(struct sock *sk)
    {
    /* There aren't current/rnext keys on TCP_LISTEN sockets */
    @@ -521,6 +529,10 @@ static int tcp_ao_add_cmd(struct sock *sk, unsigned short int family,
    return -EINVAL;
    }

    + /* Don't allow keys for peers that have a matching TCP-MD5 key */
    + if (tcp_md5_do_lookup_any_l3index(sk, addr, family))
    + return -EKEYREJECTED;
    +
    ao_info = setsockopt_ao_info(sk);
    if (IS_ERR(ao_info))
    return PTR_ERR(ao_info);
    @@ -720,6 +732,31 @@ static int tcp_ao_del_cmd(struct sock *sk, unsigned short int family,
    return -ENOENT;
    }

    +/* cmd.ao_required makes a socket TCP-AO only.
    + * Don't allow any md5 keys for any l3intf on the socket together with it.
    + * Restricting it early in setsockopt() removes a check for
    + * ao_info->ao_required on inbound tcp segment fast-path.
    + */
    +static inline int tcp_ao_required_verify(struct sock *sk)
    +{
    +#ifdef CONFIG_TCP_MD5SIG
    + const struct tcp_md5sig_info *md5sig;
    +
    + if (!static_branch_unlikely(&tcp_md5_needed.key))
    + return 0;
    +
    + md5sig = rcu_dereference_check(tcp_sk(sk)->md5sig_info,
    + lockdep_sock_is_held(sk));
    + if (!md5sig)
    + return 0;
    +
    + if (rcu_dereference_check(hlist_first_rcu(&md5sig->head),
    + lockdep_sock_is_held(sk)))
    + return 1;
    +#endif
    + return 0;
    +}
    +
    static int tcp_ao_info_cmd(struct sock *sk, unsigned short int family,
    sockptr_t optval, int optlen)
    {
    @@ -754,6 +791,9 @@ static int tcp_ao_info_cmd(struct sock *sk, unsigned short int family,
    first = true;
    }

    + if (cmd.ao_required && tcp_ao_required_verify(sk))
    + return -EKEYREJECTED;
    +
    /* For sockets in TCP_CLOSED it's possible set keys that aren't
    * matching the future peer (address/port/VRF/etc),
    * tcp_ao_connect_init() will choose a correct matching MKT
    diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
    index f8eb472b4b67..5a4bca4ea69f 100644
    --- a/net/ipv4/tcp_ipv4.c
    +++ b/net/ipv4/tcp_ipv4.c
    @@ -1078,7 +1078,7 @@ static bool better_md5_match(struct tcp_md5sig_key *old, struct tcp_md5sig_key *
    /* Find the Key structure for an address. */
    struct tcp_md5sig_key *__tcp_md5_do_lookup(const struct sock *sk, int l3index,
    const union tcp_md5_addr *addr,
    - int family)
    + int family, bool any_l3index)
    {
    const struct tcp_sock *tp = tcp_sk(sk);
    struct tcp_md5sig_key *key;
    @@ -1097,7 +1097,8 @@ struct tcp_md5sig_key *__tcp_md5_do_lookup(const struct sock *sk, int l3index,
    lockdep_sock_is_held(sk)) {
    if (key->family != family)
    continue;
    - if (key->flags & TCP_MD5SIG_FLAG_IFINDEX && key->l3index != l3index)
    + if (!any_l3index && key->flags & TCP_MD5SIG_FLAG_IFINDEX &&
    + key->l3index != l3index)
    continue;
    if (family == AF_INET) {
    mask = inet_make_mask(key->prefixlen);
    @@ -1309,7 +1310,7 @@ int tcp_md5_do_del(struct sock *sk, const union tcp_md5_addr *addr, int family,
    }
    EXPORT_SYMBOL(tcp_md5_do_del);

    -static void tcp_clear_md5_list(struct sock *sk)
    +void tcp_clear_md5_list(struct sock *sk)
    {
    struct tcp_sock *tp = tcp_sk(sk);
    struct tcp_md5sig_key *key;
    @@ -1379,6 +1380,12 @@ static int tcp_v4_parse_md5_keys(struct sock *sk, int optname,
    if (cmd.tcpm_keylen > TCP_MD5SIG_MAXKEYLEN)
    return -EINVAL;

    + /* Don't allow keys for peers that have a matching TCP-AO key.
    + * See the comment in tcp_ao_add_cmd()
    + */
    + if (tcp_ao_required(sk, addr, AF_INET))
    + return -EKEYREJECTED;
    +
    return tcp_md5_do_add(sk, addr, AF_INET, prefixlen, l3index, flags,
    cmd.tcpm_key, cmd.tcpm_keylen);
    }
    @@ -2274,6 +2281,7 @@ static const struct tcp_sock_af_ops tcp_sock_ipv4_specific = {
    .md5_parse = tcp_v4_parse_md5_keys,
    #endif
    #ifdef CONFIG_TCP_AO
    + .ao_lookup = tcp_v4_ao_lookup,
    .ao_parse = tcp_v4_parse_ao,
    #endif
    };
    diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
    index 2cb39b6dad02..d99246dbb88d 100644
    --- a/net/ipv4/tcp_output.c
    +++ b/net/ipv4/tcp_output.c
    @@ -3928,6 +3928,53 @@ int tcp_connect(struct sock *sk)

    tcp_call_bpf(sk, BPF_SOCK_OPS_TCP_CONNECT_CB, 0, NULL);

    +#if defined(CONFIG_TCP_MD5SIG) && defined(CONFIG_TCP_AO)
    + /* Has to be checked late, after setting daddr/saddr/ops.
    + * Return error if the peer has both a md5 and a tcp-ao key
    + * configured as this is ambiguous.
    + */
    + if (unlikely(rcu_dereference_protected(tp->md5sig_info,
    + lockdep_sock_is_held(sk)))) {
    + bool needs_md5 = !!tp->af_specific->md5_lookup(sk, sk);
    + bool needs_ao = !!tp->af_specific->ao_lookup(sk, sk, -1, -1);
    + struct tcp_ao_info *ao_info;
    +
    + ao_info = rcu_dereference_check(tp->ao_info,
    + lockdep_sock_is_held(sk));
    + if (ao_info) {
    + /* This is an extra check: tcp_ao_required() in
    + * tcp_v{4,6}_parse_md5_keys() should prevent adding
    + * md5 keys on ao_required socket.
    + */
    + needs_ao |= ao_info->ao_required;
    + WARN_ON_ONCE(ao_info->ao_required && needs_md5);
    + }
    + if (needs_md5 && needs_ao)
    + return -EKEYREJECTED;
    +
    + /* If we have a matching md5 key and no matching tcp-ao key
    + * then free up ao_info if allocated.
    + */
    + if (needs_md5) {
    + tcp_ao_destroy_sock(sk);
    + } else if (needs_ao) {
    + tcp_clear_md5_list(sk);
    + kfree(rcu_replace_pointer(tp->md5sig_info, NULL,
    + lockdep_sock_is_held(sk)));
    + }
    + }
    +#endif
    +#ifdef CONFIG_TCP_AO
    + if (unlikely(rcu_dereference_protected(tp->ao_info,
    + lockdep_sock_is_held(sk)))) {
    + /* Don't allow connecting if ao is configured but no
    + * matching key is found.
    + */
    + if (!tp->af_specific->ao_lookup(sk, sk, -1, -1))
    + return -EKEYREJECTED;
    + }
    +#endif
    +
    if (inet_csk(sk)->icsk_af_ops->rebuild_header(sk))
    return -EHOSTUNREACH; /* Routing failure or similar. */

    diff --git a/net/ipv6/tcp_ao.c b/net/ipv6/tcp_ao.c
    index 049ddbabe049..a56ab0a9cf55 100644
    --- a/net/ipv6/tcp_ao.c
    +++ b/net/ipv6/tcp_ao.c
    @@ -12,6 +12,23 @@
    #include <net/tcp.h>
    #include <net/ipv6.h>

    +struct tcp_ao_key *tcp_v6_ao_do_lookup(const struct sock *sk,
    + const struct in6_addr *addr,
    + int sndid, int rcvid)
    +{
    + return tcp_ao_do_lookup(sk, (union tcp_ao_addr *)addr, AF_INET6,
    + sndid, rcvid, 0);
    +}
    +
    +struct tcp_ao_key *tcp_v6_ao_lookup(const struct sock *sk,
    + struct sock *addr_sk,
    + int sndid, int rcvid)
    +{
    + struct in6_addr *addr = &addr_sk->sk_v6_daddr;
    +
    + return tcp_v6_ao_do_lookup(sk, addr, sndid, rcvid);
    +}
    +
    int tcp_v6_parse_ao(struct sock *sk, int cmd,
    sockptr_t optval, int optlen)
    {
    diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
    index 79c6673f707d..0ebeb16440e2 100644
    --- a/net/ipv6/tcp_ipv6.c
    +++ b/net/ipv6/tcp_ipv6.c
    @@ -599,6 +599,7 @@ static int tcp_v6_parse_md5_keys(struct sock *sk, int optname,
    {
    struct tcp_md5sig cmd;
    struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *)&cmd.tcpm_addr;
    + union tcp_ao_addr *addr;
    int l3index = 0;
    u8 prefixlen;
    u8 flags;
    @@ -653,13 +654,28 @@ static int tcp_v6_parse_md5_keys(struct sock *sk, int optname,
    if (cmd.tcpm_keylen > TCP_MD5SIG_MAXKEYLEN)
    return -EINVAL;

    - if (ipv6_addr_v4mapped(&sin6->sin6_addr))
    - return tcp_md5_do_add(sk, (union tcp_md5_addr *)&sin6->sin6_addr.s6_addr32[3],
    + if (ipv6_addr_v4mapped(&sin6->sin6_addr)) {
    + addr = (union tcp_md5_addr *)&sin6->sin6_addr.s6_addr32[3];
    +
    + /* Don't allow keys for peers that have a matching TCP-AO key.
    + * See the comment in tcp_ao_add_cmd()
    + */
    + if (tcp_ao_required(sk, addr, AF_INET))
    + return -EKEYREJECTED;
    + return tcp_md5_do_add(sk, addr,
    AF_INET, prefixlen, l3index, flags,
    cmd.tcpm_key, cmd.tcpm_keylen);
    + }

    - return tcp_md5_do_add(sk, (union tcp_md5_addr *)&sin6->sin6_addr,
    - AF_INET6, prefixlen, l3index, flags,
    + addr = (union tcp_md5_addr *)&sin6->sin6_addr;
    +
    + /* Don't allow keys for peers that have a matching TCP-AO key.
    + * See the comment in tcp_ao_add_cmd()
    + */
    + if (tcp_ao_required(sk, addr, AF_INET6))
    + return -EKEYREJECTED;
    +
    + return tcp_md5_do_add(sk, addr, AF_INET6, prefixlen, l3index, flags,
    cmd.tcpm_key, cmd.tcpm_keylen);
    }

    @@ -1899,6 +1915,7 @@ static const struct tcp_sock_af_ops tcp_sock_ipv6_specific = {
    .md5_parse = tcp_v6_parse_md5_keys,
    #endif
    #ifdef CONFIG_TCP_AO
    + .ao_lookup = tcp_v6_ao_lookup,
    .ao_parse = tcp_v6_parse_ao,
    #endif
    };
    @@ -1930,6 +1947,7 @@ static const struct tcp_sock_af_ops tcp_sock_ipv6_mapped_specific = {
    .md5_parse = tcp_v6_parse_md5_keys,
    #endif
    #ifdef CONFIG_TCP_AO
    + .ao_lookup = tcp_v6_ao_lookup,
    .ao_parse = tcp_v6_parse_ao,
    #endif
    };
    --
    2.41.0
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