[PATCH net] mptcp: fix ADD_ADDR HMAC in case port is specified

[Davide Caratti]

Currently, Linux computes the HMAC contained in ADD_ADDR sub-option using
the Address Id and the IP Address, and hardcodes a destination port equal
to zero. This is not ok for ADD_ADDR with port: ensure to account for the
endpoint port when computing the HMAC, in compliance with RFC8684 §3.4.1.

Fixes: 22fb85ffaefb ("mptcp: add port support for ADD_ADDR suboption writing")
Reviewed-by: Mat Martineau <mathew.j.martin...@linux.intel.com>
Acked-by: Geliang Tang <geliangt...@gmail.com>
Signed-off-by: Davide Caratti <dcara...@redhat.com>
---
 net/mptcp/options.c | 24 ++++++++++++++----------
 1 file changed, 14 insertions(+), 10 deletions(-)

diff --git a/net/mptcp/options.c b/net/mptcp/options.c
index 5fabf3e9a38d..2b7eec93c9f5 100644
--- a/net/mptcp/options.c
+++ b/net/mptcp/options.c
@@ -571,15 +571,15 @@ static bool mptcp_established_options_dss(struct sock 
*sk, struct sk_buff *skb,
 }
 
 static u64 add_addr_generate_hmac(u64 key1, u64 key2, u8 addr_id,
-                                 struct in_addr *addr)
+                                 struct in_addr *addr, u16 port)
 {
        u8 hmac[SHA256_DIGEST_SIZE];
        u8 msg[7];
 
        msg[0] = addr_id;
        memcpy(&msg[1], &addr->s_addr, 4);
-       msg[5] = 0;
-       msg[6] = 0;
+       msg[5] = port >> 8;
+       msg[6] = port & 0xFF;
 
        mptcp_crypto_hmac_sha(key1, key2, msg, 7, hmac);
 
@@ -588,15 +588,15 @@ static u64 add_addr_generate_hmac(u64 key1, u64 key2, u8 
addr_id,
 
 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 static u64 add_addr6_generate_hmac(u64 key1, u64 key2, u8 addr_id,
-                                  struct in6_addr *addr)
+                                  struct in6_addr *addr, u16 port)
 {
        u8 hmac[SHA256_DIGEST_SIZE];
        u8 msg[19];
 
        msg[0] = addr_id;
        memcpy(&msg[1], &addr->s6_addr, 16);
-       msg[17] = 0;
-       msg[18] = 0;
+       msg[17] = port >> 8;
+       msg[18] = port & 0xFF;
 
        mptcp_crypto_hmac_sha(key1, key2, msg, 19, hmac);
 
@@ -650,7 +650,8 @@ static bool mptcp_established_options_add_addr(struct sock 
*sk, struct sk_buff *
                        opts->ahmac = add_addr_generate_hmac(msk->local_key,
                                                             msk->remote_key,
                                                             opts->addr_id,
-                                                            &opts->addr);
+                                                            &opts->addr,
+                                                            opts->port);
                }
        }
 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
@@ -661,7 +662,8 @@ static bool mptcp_established_options_add_addr(struct sock 
*sk, struct sk_buff *
                        opts->ahmac = add_addr6_generate_hmac(msk->local_key,
                                                              msk->remote_key,
                                                              opts->addr_id,
-                                                             &opts->addr6);
+                                                             &opts->addr6,
+                                                             opts->port);
                }
        }
 #endif
@@ -971,12 +973,14 @@ static bool add_addr_hmac_valid(struct mptcp_sock *msk,
        if (mp_opt->family == MPTCP_ADDR_IPVERSION_4)
                hmac = add_addr_generate_hmac(msk->remote_key,
                                              msk->local_key,
-                                             mp_opt->addr_id, &mp_opt->addr);
+                                             mp_opt->addr_id, &mp_opt->addr,
+                                             mp_opt->port);
 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
        else
                hmac = add_addr6_generate_hmac(msk->remote_key,
                                               msk->local_key,
-                                              mp_opt->addr_id, &mp_opt->addr6);
+                                              mp_opt->addr_id, &mp_opt->addr6,
+                                              mp_opt->port);
 #endif
 
        pr_debug("msk=%p, ahmac=%llu, mp_opt->ahmac=%llu\n",
-- 
2.29.2