net/tcp: Add TCP-AO sign to outgoing packets

Using precalculated traffic keys, sign TCP segments as prescribed by
RFC5925. Per RFC, TCP header options are included in sign calculation:
"The TCP header, by default including options, and where the TCP
checksum and TCP-AO MAC fields are set to zero, all in network-
byte order." (5.1.3)

tcp_ao_hash_header() has exclude_options parameter to optionally exclude
TCP header from hash calculation, as described in RFC5925 (9.1), this is
needed for interaction with middleboxes that may change "some TCP
options". This is wired up to AO key flags and setsockopt() later.

Similarly to TCP-MD5 hash TCP segment fragments.

From this moment a user can start sending TCP-AO signed segments with
one of crypto ahash algorithms from supported by Linux kernel. It can
have a user-specified MAC length, to either save TCP option header space
or provide higher protection using a longer signature.
The inbound segments are not yet verified, TCP-AO option is ignored and
they are accepted.

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>

1 files changed, 28 insertions, 0 deletions

diff --git a/net/ipv6/tcp_ao.c b/net/ipv6/tcp_ao.c
index 9ab594fadbd9..d08735b6f3c5 100644
--- a/net/ipv6/tcp_ao.c
+++ b/net/ipv6/tcp_ao.c
@@ -7,6 +7,7 @@
  *		Francesco Ruggeri <fruggeri@arista.com>
  *		Salam Noureddine <noureddine@arista.com>
  */
+#include <crypto/hash.h>
 #include <linux/tcp.h>
 
 #include <net/tcp.h>
@@ -79,6 +80,33 @@ struct tcp_ao_key *tcp_v6_ao_lookup(const struct sock *sk,
 	return tcp_v6_ao_do_lookup(sk, addr, sndid, rcvid);
 }
 
+int tcp_v6_ao_hash_pseudoheader(struct tcp_sigpool *hp,
+				const struct in6_addr *daddr,
+				const struct in6_addr *saddr, int nbytes)
+{
+	struct tcp6_pseudohdr *bp;
+	struct scatterlist sg;
+
+	bp = hp->scratch;
+	/* 1. TCP pseudo-header (RFC2460) */
+	bp->saddr = *saddr;
+	bp->daddr = *daddr;
+	bp->len = cpu_to_be32(nbytes);
+	bp->protocol = cpu_to_be32(IPPROTO_TCP);
+
+	sg_init_one(&sg, bp, sizeof(*bp));
+	ahash_request_set_crypt(hp->req, &sg, NULL, sizeof(*bp));
+	return crypto_ahash_update(hp->req);
+}
+
+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)
+{
+	return tcp_ao_hash_skb(AF_INET6, ao_hash, key, sk, skb, tkey,
+			hash_offset, sne);
+}
+
 int tcp_v6_parse_ao(struct sock *sk, int cmd,
 		    sockptr_t optval, int optlen)
 {