From 37a183d3b7cdb873e7f5f9daef1ad6d8f7c95fb7 Mon Sep 17 00:00:00 2001 From: Eric Biggers Date: Tue, 14 Oct 2025 14:58:36 -0700 Subject: tcp: Convert tcp-md5 to use MD5 library instead of crypto_ahash Make tcp-md5 use the MD5 library API (added in 6.18) instead of the crypto_ahash API. This is much simpler and also more efficient: - The library API just operates on struct md5_ctx. Just allocate this struct on the stack instead of using a pool of pre-allocated crypto_ahash and ahash_request objects. - The library API accepts standard pointers and doesn't require scatterlists. So, for hashing the headers just use an on-stack buffer instead of a pool of pre-allocated kmalloc'ed scratch buffers. - The library API never fails. Therefore, checking for MD5 hashing errors is no longer necessary. Update tcp_v4_md5_hash_skb(), tcp_v6_md5_hash_skb(), tcp_v4_md5_hash_hdr(), tcp_v6_md5_hash_hdr(), tcp_md5_hash_key(), tcp_sock_af_ops::calc_md5_hash, and tcp_request_sock_ops::calc_md5_hash to return void instead of int. - The library API provides direct access to the MD5 code, eliminating unnecessary overhead such as indirect function calls and scatterlist management. Microbenchmarks of tcp_v4_md5_hash_skb() on x86_64 show a speedup from 7518 to 7041 cycles (6% fewer) with skb->len == 1440, or from 1020 to 678 cycles (33% fewer) with skb->len == 140. Since tcp_sigpool_hash_skb_data() can no longer be used, add a function tcp_md5_hash_skb_data() which is specialized to MD5. Of course, to the extent that this duplicates any code, it's well worth it. To preserve the existing behavior of TCP-MD5 support being disabled when the kernel is booted with "fips=1", make tcp_md5_do_add() check fips_enabled itself. Previously it relied on the error from crypto_alloc_ahash("md5") being bubbled up. I don't know for sure that this is actually needed, but this preserves the existing behavior. Tested with bidirectional TCP-MD5, both IPv4 and IPv6, between a kernel that includes this commit and a kernel that doesn't include this commit. (Side note: please don't use TCP-MD5! It's cryptographically weak. But as long as Linux supports it, it might as well be implemented properly.) Signed-off-by: Eric Biggers Link: https://patch.msgid.link/20251014215836.115616-1-ebiggers@kernel.org Signed-off-by: Jakub Kicinski --- include/net/tcp.h | 26 ++++++++------------------ 1 file changed, 8 insertions(+), 18 deletions(-) (limited to 'include') diff --git a/include/net/tcp.h b/include/net/tcp.h index 1e547138f4fb..67fdd2523d92 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -1898,13 +1898,6 @@ struct tcp6_pseudohdr { __be32 protocol; /* including padding */ }; -union tcp_md5sum_block { - struct tcp4_pseudohdr ip4; -#if IS_ENABLED(CONFIG_IPV6) - struct tcp6_pseudohdr ip6; -#endif -}; - /* * struct tcp_sigpool - per-CPU pool of ahash_requests * @scratch: per-CPU temporary area, that can be used between @@ -1939,8 +1932,8 @@ int tcp_sigpool_start(unsigned int id, struct tcp_sigpool *c); void tcp_sigpool_end(struct tcp_sigpool *c); size_t tcp_sigpool_algo(unsigned int id, char *buf, size_t buf_len); /* - functions */ -int tcp_v4_md5_hash_skb(char *md5_hash, const struct tcp_md5sig_key *key, - const struct sock *sk, const struct sk_buff *skb); +void tcp_v4_md5_hash_skb(char *md5_hash, const struct tcp_md5sig_key *key, + const struct sock *sk, const struct sk_buff *skb); int tcp_md5_do_add(struct sock *sk, const union tcp_md5_addr *addr, int family, u8 prefixlen, int l3index, u8 flags, const u8 *newkey, u8 newkeylen); @@ -1999,13 +1992,10 @@ static inline void tcp_md5_destruct_sock(struct sock *sk) } #endif -int tcp_md5_alloc_sigpool(void); -void tcp_md5_release_sigpool(void); -void tcp_md5_add_sigpool(void); -extern int tcp_md5_sigpool_id; - -int tcp_md5_hash_key(struct tcp_sigpool *hp, - const struct tcp_md5sig_key *key); +struct md5_ctx; +void tcp_md5_hash_skb_data(struct md5_ctx *ctx, const struct sk_buff *skb, + unsigned int header_len); +void tcp_md5_hash_key(struct md5_ctx *ctx, const struct tcp_md5sig_key *key); /* From tcp_fastopen.c */ void tcp_fastopen_cache_get(struct sock *sk, u16 *mss, @@ -2355,7 +2345,7 @@ struct tcp_sock_af_ops { #ifdef CONFIG_TCP_MD5SIG struct tcp_md5sig_key *(*md5_lookup) (const struct sock *sk, const struct sock *addr_sk); - int (*calc_md5_hash)(char *location, + void (*calc_md5_hash)(char *location, const struct tcp_md5sig_key *md5, const struct sock *sk, const struct sk_buff *skb); @@ -2383,7 +2373,7 @@ struct tcp_request_sock_ops { #ifdef CONFIG_TCP_MD5SIG struct tcp_md5sig_key *(*req_md5_lookup)(const struct sock *sk, const struct sock *addr_sk); - int (*calc_md5_hash) (char *location, + void (*calc_md5_hash) (char *location, const struct tcp_md5sig_key *md5, const struct sock *sk, const struct sk_buff *skb); -- cgit v1.2.3