[PATCH v5 11/20] tcp: ipv4: Add AO signing for skb-less replies
From: Leonard Crestez
Date: Mon Jan 24 2022 - 07:15:15 EST
The code in tcp_v4_send_ack and tcp_v4_send_reset does not allocate a
full skb so special handling is required for tcp-authopt handling.
Signed-off-by: Leonard Crestez <cdleonard@xxxxxxxxx>
---
net/ipv4/tcp_authopt.c | 3 +-
net/ipv4/tcp_ipv4.c | 84 ++++++++++++++++++++++++++++++++++++++++--
2 files changed, 83 insertions(+), 4 deletions(-)
diff --git a/net/ipv4/tcp_authopt.c b/net/ipv4/tcp_authopt.c
index 7a2e15dd80ba..d924a73a17c1 100644
--- a/net/ipv4/tcp_authopt.c
+++ b/net/ipv4/tcp_authopt.c
@@ -955,10 +955,11 @@ static int tcp_v4_authopt_get_traffic_key_noskb(struct tcp_authopt_key_info *key
u8 *traffic_key)
{
int err;
struct tcp_authopt_alg_pool *pool;
struct tcp_v4_authopt_context_data data;
+ char traffic_key_context_header[7] = "\x01TCP-AO";
BUILD_BUG_ON(sizeof(data) != 22);
pool = tcp_authopt_get_kdf_pool(key);
if (IS_ERR(pool))
@@ -971,11 +972,11 @@ static int tcp_v4_authopt_get_traffic_key_noskb(struct tcp_authopt_key_info *key
if (err)
goto out;
// RFC5926 section 3.1.1.1
// Separate to keep alignment semi-sane
- err = crypto_ahash_buf(pool->req, "\x01TCP-AO", 7);
+ err = crypto_ahash_buf(pool->req, traffic_key_context_header, 7);
if (err)
return err;
data.saddr = saddr;
data.daddr = daddr;
data.sport = sport;
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 5a7fe973bc4e..e35463a378e7 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -644,10 +644,50 @@ void tcp_v4_send_check(struct sock *sk, struct sk_buff *skb)
__tcp_v4_send_check(skb, inet->inet_saddr, inet->inet_daddr);
}
EXPORT_SYMBOL(tcp_v4_send_check);
+#ifdef CONFIG_TCP_AUTHOPT
+/** tcp_v4_authopt_handle_reply - Insert TCPOPT_AUTHOPT if required
+ *
+ * returns number of bytes (always aligned to 4) or zero
+ */
+static int tcp_v4_authopt_handle_reply(const struct sock *sk,
+ struct sk_buff *skb,
+ __be32 *optptr,
+ struct tcphdr *th)
+{
+ struct tcp_authopt_info *info;
+ struct tcp_authopt_key_info *key_info;
+ u8 rnextkeyid;
+
+ if (sk->sk_state == TCP_TIME_WAIT)
+ info = tcp_twsk(sk)->tw_authopt_info;
+ else
+ info = rcu_dereference_check(tcp_sk(sk)->authopt_info, lockdep_sock_is_held(sk));
+ if (!info)
+ return 0;
+ key_info = __tcp_authopt_select_key(sk, info, sk, &rnextkeyid);
+ if (!key_info)
+ return 0;
+ *optptr = htonl((TCPOPT_AUTHOPT << 24) |
+ (TCPOLEN_AUTHOPT_OUTPUT << 16) |
+ (key_info->send_id << 8) |
+ (rnextkeyid));
+ /* must update doff before signature computation */
+ th->doff += TCPOLEN_AUTHOPT_OUTPUT / 4;
+ tcp_v4_authopt_hash_reply((char *)(optptr + 1),
+ info,
+ key_info,
+ ip_hdr(skb)->daddr,
+ ip_hdr(skb)->saddr,
+ th);
+
+ return TCPOLEN_AUTHOPT_OUTPUT;
+}
+#endif
+
/*
* This routine will send an RST to the other tcp.
*
* Someone asks: why I NEVER use socket parameters (TOS, TTL etc.)
* for reset.
@@ -659,10 +699,12 @@ EXPORT_SYMBOL(tcp_v4_send_check);
* Exception: precedence violation. We do not implement it in any case.
*/
#ifdef CONFIG_TCP_MD5SIG
#define OPTION_BYTES TCPOLEN_MD5SIG_ALIGNED
+#elif defined(OPTION_BYTES_TCP_AUTHOPT)
+#define OPTION_BYTES TCPOLEN_AUTHOPT_OUTPUT
#else
#define OPTION_BYTES sizeof(__be32)
#endif
static void tcp_v4_send_reset(const struct sock *sk, struct sk_buff *skb)
@@ -712,12 +754,29 @@ static void tcp_v4_send_reset(const struct sock *sk, struct sk_buff *skb)
memset(&arg, 0, sizeof(arg));
arg.iov[0].iov_base = (unsigned char *)&rep;
arg.iov[0].iov_len = sizeof(rep.th);
net = sk ? sock_net(sk) : dev_net(skb_dst(skb)->dev);
-#ifdef CONFIG_TCP_MD5SIG
+#if defined(CONFIG_TCP_MD5SIG) || defined(CONFIG_TCP_AUTHOPT)
rcu_read_lock();
+#endif
+#ifdef CONFIG_TCP_AUTHOPT
+ /* Unlike TCP-MD5 the signatures for TCP-AO depend on initial sequence
+ * numbers so we can only handle established and time-wait sockets.
+ */
+ if (tcp_authopt_needed && sk &&
+ sk->sk_state != TCP_NEW_SYN_RECV &&
+ sk->sk_state != TCP_LISTEN) {
+ int tcp_authopt_ret = tcp_v4_authopt_handle_reply(sk, skb, rep.opt, &rep.th);
+
+ if (tcp_authopt_ret) {
+ arg.iov[0].iov_len += tcp_authopt_ret;
+ goto skip_md5sig;
+ }
+ }
+#endif
+#ifdef CONFIG_TCP_MD5SIG
hash_location = tcp_parse_md5sig_option(th);
if (sk && sk_fullsock(sk)) {
const union tcp_md5_addr *addr;
int l3index;
@@ -755,11 +814,10 @@ static void tcp_v4_send_reset(const struct sock *sk, struct sk_buff *skb)
addr = (union tcp_md5_addr *)&ip_hdr(skb)->saddr;
key = tcp_md5_do_lookup(sk1, l3index, addr, AF_INET);
if (!key)
goto out;
-
genhash = tcp_v4_md5_hash_skb(newhash, key, NULL, skb);
if (genhash || memcmp(hash_location, newhash, 16) != 0)
goto out;
}
@@ -775,10 +833,13 @@ static void tcp_v4_send_reset(const struct sock *sk, struct sk_buff *skb)
tcp_v4_md5_hash_hdr((__u8 *) &rep.opt[1],
key, ip_hdr(skb)->saddr,
ip_hdr(skb)->daddr, &rep.th);
}
+#endif
+#ifdef CONFIG_TCP_AUTHOPT
+skip_md5sig:
#endif
/* Can't co-exist with TCPMD5, hence check rep.opt[0] */
if (rep.opt[0] == 0) {
__be32 mrst = mptcp_reset_option(skb);
@@ -828,12 +889,14 @@ static void tcp_v4_send_reset(const struct sock *sk, struct sk_buff *skb)
ctl_sk->sk_mark = 0;
__TCP_INC_STATS(net, TCP_MIB_OUTSEGS);
__TCP_INC_STATS(net, TCP_MIB_OUTRSTS);
local_bh_enable();
-#ifdef CONFIG_TCP_MD5SIG
+#if defined(CONFIG_TCP_MD5SIG)
out:
+#endif
+#if defined(CONFIG_TCP_MD5SIG) || defined(CONFIG_TCP_AUTHOPT)
rcu_read_unlock();
#endif
}
/* The code following below sending ACKs in SYN-RECV and TIME-WAIT states
@@ -850,10 +913,12 @@ static void tcp_v4_send_ack(const struct sock *sk,
struct {
struct tcphdr th;
__be32 opt[(TCPOLEN_TSTAMP_ALIGNED >> 2)
#ifdef CONFIG_TCP_MD5SIG
+ (TCPOLEN_MD5SIG_ALIGNED >> 2)
+#elif defined(CONFIG_TCP_AUTHOPT)
+ + (TCPOLEN_AUTHOPT_OUTPUT >> 2)
#endif
];
} rep;
struct net *net = sock_net(sk);
struct ip_reply_arg arg;
@@ -881,10 +946,23 @@ static void tcp_v4_send_ack(const struct sock *sk,
rep.th.seq = htonl(seq);
rep.th.ack_seq = htonl(ack);
rep.th.ack = 1;
rep.th.window = htons(win);
+#ifdef CONFIG_TCP_AUTHOPT
+ if (tcp_authopt_needed) {
+ int aoret, offset = (tsecr) ? 3 : 0;
+
+ aoret = tcp_v4_authopt_handle_reply(sk, skb, &rep.opt[offset], &rep.th);
+ if (aoret) {
+ arg.iov[0].iov_len += aoret;
+#ifdef CONFIG_TCP_MD5SIG
+ key = NULL;
+#endif
+ }
+ }
+#endif
#ifdef CONFIG_TCP_MD5SIG
if (key) {
int offset = (tsecr) ? 3 : 0;
rep.opt[offset++] = htonl((TCPOPT_NOP << 24) |
--
2.25.1