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net/tcp: Sign SYN-ACK segments with TCP-AO

Browse Source 
Similarly to RST segments, wire SYN-ACKs to TCP-AO.
tcp_rsk_used_ao() is handy here to check if the request socket used AO
and needs a signature on the outgoing segments.

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>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Dmitry Safonov 2023-10-23 20:22:03 +01:00 committed by David S. Miller
parent 06b22ef295
commit 9427c6aa3e
7 changed files with 111 additions and 16 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
include/net/tcp.h
View File

@ -2221,6 +2221,9 @@ struct tcp_request_sock_ops {
struct request_sock *req,
int sndid, int rcvid);
int (*ao_calc_key)(struct tcp_ao_key *mkt, u8 *key, struct request_sock *sk);
int (*ao_synack_hash)(char *ao_hash, struct tcp_ao_key *mkt,
struct request_sock *req, const struct sk_buff *skb,
int hash_offset, u32 sne);
#endif
#ifdef CONFIG_SYN_COOKIES
__u32 (*cookie_init_seq)(const struct sk_buff *skb,

6
include/net/tcp_ao.h
View File

@ -147,6 +147,9 @@ int tcp_ao_prepare_reset(const struct sock *sk, struct sk_buff *skb,
int tcp_v4_parse_ao(struct sock *sk, int cmd, 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);
int tcp_v4_ao_synack_hash(char *ao_hash, struct tcp_ao_key *mkt,
struct request_sock *req, const struct sk_buff *skb,
int hash_offset, u32 sne);
int tcp_v4_ao_calc_key_sk(struct tcp_ao_key *mkt, u8 *key,
const struct sock *sk,
__be32 sisn, __be32 disn, bool send);
@ -181,6 +184,9 @@ int tcp_v6_ao_hash_skb(char *ao_hash, struct tcp_ao_key *key,
const struct sock *sk, const struct sk_buff *skb,
const u8 *tkey, int hash_offset, u32 sne);
int tcp_v6_parse_ao(struct sock *sk, int cmd, sockptr_t optval, int optlen);
int tcp_v6_ao_synack_hash(char *ao_hash, struct tcp_ao_key *ao_key,
struct request_sock *req, const struct sk_buff *skb,
int hash_offset, u32 sne);
void tcp_ao_established(struct sock *sk);
void tcp_ao_finish_connect(struct sock *sk, struct sk_buff *skb);
void tcp_ao_connect_init(struct sock *sk);

22
net/ipv4/tcp_ao.c
View File

@ -568,6 +568,28 @@ int tcp_v4_ao_hash_skb(char *ao_hash, struct tcp_ao_key *key,
tkey, hash_offset, sne);
}
int tcp_v4_ao_synack_hash(char *ao_hash, struct tcp_ao_key *ao_key,
struct request_sock *req, const struct sk_buff *skb,
int hash_offset, u32 sne)
{
void *hash_buf = NULL;
int err;
hash_buf = kmalloc(tcp_ao_digest_size(ao_key), GFP_ATOMIC);
if (!hash_buf)
return -ENOMEM;
err = tcp_v4_ao_calc_key_rsk(ao_key, hash_buf, req);
if (err)
goto out;
err = tcp_ao_hash_skb(AF_INET, ao_hash, ao_key, req_to_sk(req), skb,
hash_buf, hash_offset, sne);
out:
kfree(hash_buf);
return err;
}
struct tcp_ao_key *tcp_v4_ao_lookup_rsk(const struct sock *sk,
struct request_sock *req,
int sndid, int rcvid)

1
net/ipv4/tcp_ipv4.c
View File

@ -1681,6 +1681,7 @@ const struct tcp_request_sock_ops tcp_request_sock_ipv4_ops = {
#ifdef CONFIG_TCP_AO
.ao_lookup = tcp_v4_ao_lookup_rsk,
.ao_calc_key = tcp_v4_ao_calc_key_rsk,
.ao_synack_hash = tcp_v4_ao_synack_hash,
#endif
#ifdef CONFIG_SYN_COOKIES
.cookie_init_seq = cookie_v4_init_sequence,

72
net/ipv4/tcp_output.c
View File

@ -886,7 +886,7 @@ static unsigned int tcp_synack_options(const struct sock *sk,
struct request_sock *req,
unsigned int mss, struct sk_buff *skb,
struct tcp_out_options *opts,
const struct tcp_md5sig_key *md5,
const struct tcp_key *key,
struct tcp_fastopen_cookie *foc,
enum tcp_synack_type synack_type,
struct sk_buff *syn_skb)
@ -894,8 +894,7 @@ static unsigned int tcp_synack_options(const struct sock *sk,
struct inet_request_sock *ireq = inet_rsk(req);
unsigned int remaining = MAX_TCP_OPTION_SPACE;
#ifdef CONFIG_TCP_MD5SIG
if (md5) {
if (tcp_key_is_md5(key)) {
opts->options |= OPTION_MD5;
remaining -= TCPOLEN_MD5SIG_ALIGNED;
@ -906,8 +905,11 @@ static unsigned int tcp_synack_options(const struct sock *sk,
*/
if (synack_type != TCP_SYNACK_COOKIE)
ireq->tstamp_ok &= !ireq->sack_ok;
} else if (tcp_key_is_ao(key)) {
opts->options |= OPTION_AO;
remaining -= tcp_ao_len(key->ao_key);
ireq->tstamp_ok &= !ireq->sack_ok;
}
#endif
/* We always send an MSS option. */
opts->mss = mss;
@ -3653,7 +3655,6 @@ struct sk_buff *tcp_make_synack(const struct sock *sk, struct dst_entry *dst,
{
struct inet_request_sock *ireq = inet_rsk(req);
const struct tcp_sock *tp = tcp_sk(sk);
struct tcp_md5sig_key *md5 = NULL;
struct tcp_out_options opts;
struct tcp_key key = {};
struct sk_buff *skb;
@ -3707,18 +3708,48 @@ struct sk_buff *tcp_make_synack(const struct sock *sk, struct dst_entry *dst,
tcp_rsk(req)->snt_synack = tcp_skb_timestamp_us(skb);
}
#ifdef CONFIG_TCP_MD5SIG
#if defined(CONFIG_TCP_MD5SIG) || defined(CONFIG_TCP_AO)
rcu_read_lock();
md5 = tcp_rsk(req)->af_specific->req_md5_lookup(sk, req_to_sk(req));
if (md5)
key.type = TCP_KEY_MD5;
#endif
if (tcp_rsk_used_ao(req)) {
#ifdef CONFIG_TCP_AO
struct tcp_ao_key *ao_key = NULL;
u8 maclen = tcp_rsk(req)->maclen;
u8 keyid = tcp_rsk(req)->ao_keyid;
ao_key = tcp_sk(sk)->af_specific->ao_lookup(sk, req_to_sk(req),
keyid, -1);
/* If there is no matching key - avoid sending anything,
* especially usigned segments. It could try harder and lookup
* for another peer-matching key, but the peer has requested
* ao_keyid (RFC5925 RNextKeyID), so let's keep it simple here.
*/
if (unlikely(!ao_key || tcp_ao_maclen(ao_key) != maclen)) {
u8 key_maclen = ao_key ? tcp_ao_maclen(ao_key) : 0;
rcu_read_unlock();
kfree_skb(skb);
net_warn_ratelimited("TCP-AO: the keyid %u with maclen %u|%u from SYN packet is not present - not sending SYNACK\n",
keyid, maclen, key_maclen);
return NULL;
}
key.ao_key = ao_key;
key.type = TCP_KEY_AO;
#endif
} else {
#ifdef CONFIG_TCP_MD5SIG
key.md5_key = tcp_rsk(req)->af_specific->req_md5_lookup(sk,
req_to_sk(req));
if (key.md5_key)
key.type = TCP_KEY_MD5;
#endif
}
skb_set_hash(skb, READ_ONCE(tcp_rsk(req)->txhash), PKT_HASH_TYPE_L4);
/* bpf program will be interested in the tcp_flags */
TCP_SKB_CB(skb)->tcp_flags = TCPHDR_SYN | TCPHDR_ACK;
tcp_header_size = tcp_synack_options(sk, req, mss, skb, &opts, md5,
foc, synack_type,
syn_skb) + sizeof(*th);
tcp_header_size = tcp_synack_options(sk, req, mss, skb, &opts,
&key, foc, synack_type, syn_skb)
+ sizeof(*th);
skb_push(skb, tcp_header_size);
skb_reset_transport_header(skb);
@ -3738,15 +3769,24 @@ struct sk_buff *tcp_make_synack(const struct sock *sk, struct dst_entry *dst,
/* RFC1323: The window in SYN & SYN/ACK segments is never scaled. */
th->window = htons(min(req->rsk_rcv_wnd, 65535U));
tcp_options_write(th, NULL, NULL, &opts, &key);
tcp_options_write(th, NULL, tcp_rsk(req), &opts, &key);
th->doff = (tcp_header_size >> 2);
TCP_INC_STATS(sock_net(sk), TCP_MIB_OUTSEGS);
#ifdef CONFIG_TCP_MD5SIG
/* Okay, we have all we need - do the md5 hash if needed */
if (md5)
if (tcp_key_is_md5(&key)) {
#ifdef CONFIG_TCP_MD5SIG
tcp_rsk(req)->af_specific->calc_md5_hash(opts.hash_location,
md5, req_to_sk(req), skb);
key.md5_key, req_to_sk(req), skb);
#endif
} else if (tcp_key_is_ao(&key)) {
#ifdef CONFIG_TCP_AO
tcp_rsk(req)->af_specific->ao_synack_hash(opts.hash_location,
key.ao_key, req, skb,
opts.hash_location - (u8 *)th, 0);
#endif
}
#if defined(CONFIG_TCP_MD5SIG) || defined(CONFIG_TCP_AO)
rcu_read_unlock();
#endif

22
net/ipv6/tcp_ao.c
View File

@ -144,3 +144,25 @@ int tcp_v6_parse_ao(struct sock *sk, int cmd,
{
return tcp_parse_ao(sk, cmd, AF_INET6, optval, optlen);
}
int tcp_v6_ao_synack_hash(char *ao_hash, struct tcp_ao_key *ao_key,
struct request_sock *req, const struct sk_buff *skb,
int hash_offset, u32 sne)
{
void *hash_buf = NULL;
int err;
hash_buf = kmalloc(tcp_ao_digest_size(ao_key), GFP_ATOMIC);
if (!hash_buf)
return -ENOMEM;
err = tcp_v6_ao_calc_key_rsk(ao_key, hash_buf, req);
if (err)
goto out;
err = tcp_ao_hash_skb(AF_INET6, ao_hash, ao_key, req_to_sk(req), skb,
hash_buf, hash_offset, sne);
out:
kfree(hash_buf);
return err;
}

1
net/ipv6/tcp_ipv6.c
View File

@ -839,6 +839,7 @@ const struct tcp_request_sock_ops tcp_request_sock_ipv6_ops = {
#ifdef CONFIG_TCP_AO
.ao_lookup = tcp_v6_ao_lookup_rsk,
.ao_calc_key = tcp_v6_ao_calc_key_rsk,
.ao_synack_hash = tcp_v6_ao_synack_hash,
#endif
#ifdef CONFIG_SYN_COOKIES
.cookie_init_seq = cookie_v6_init_sequence,