SHA1 is slower and less secure than SipHash, and so replacing syncookie
generation with SipHash makes natural sense. Some BSDs have been doing
this for several years in fact.
Signed-off-by: Jason A. Donenfeld <ja...@zx2c4.com>
---
net/ipv4/syncookies.c | 20 ++++----------------
net/ipv6/syncookies.c | 37 ++++++++++++++++---------------------
2 files changed, 20 insertions(+), 37 deletions(-)
diff --git a/net/ipv4/syncookies.c b/net/ipv4/syncookies.c
index 3e88467d70ee..03bb068f8888 100644
--- a/net/ipv4/syncookies.c
+++ b/net/ipv4/syncookies.c
@@ -13,13 +13,13 @@
#include <linux/tcp.h>
#include <linux/slab.h>
#include <linux/random.h>
-#include <linux/cryptohash.h>
+#include <linux/siphash.h>
#include <linux/kernel.h>
#include <linux/export.h>
#include <net/tcp.h>
#include <net/route.h>
-static u32 syncookie_secret[2][16-4+SHA_DIGEST_WORDS] __read_mostly;
+static siphash_key_t syncookie_secret[2] __read_mostly;
#define COOKIEBITS 24 /* Upper bits store count */
#define COOKIEMASK (((__u32)1 << COOKIEBITS) - 1)
@@ -48,24 +48,12 @@ static u32 syncookie_secret[2][16-4+SHA_DIGEST_WORDS]
__read_mostly;
#define TSBITS 6
#define TSMASK (((__u32)1 << TSBITS) - 1)
-static DEFINE_PER_CPU(__u32 [16 + 5 + SHA_WORKSPACE_WORDS],
ipv4_cookie_scratch);
-
static u32 cookie_hash(__be32 saddr, __be32 daddr, __be16 sport, __be16 dport,
u32 count, int c)
{
- __u32 *tmp;
-
net_get_random_once(syncookie_secret, sizeof(syncookie_secret));
-
- tmp = this_cpu_ptr(ipv4_cookie_scratch);
- memcpy(tmp + 4, syncookie_secret[c], sizeof(syncookie_secret[c]));
- tmp[0] = (__force u32)saddr;
- tmp[1] = (__force u32)daddr;
- tmp[2] = ((__force u32)sport << 16) + (__force u32)dport;
- tmp[3] = count;
- sha_transform(tmp + 16, (__u8 *)tmp, tmp + 16 + 5);
-
- return tmp[17];
+ return siphash_4u32(saddr, daddr, (u32)sport << 16 | dport, count,
+ syncookie_secret[c]);
}
diff --git a/net/ipv6/syncookies.c b/net/ipv6/syncookies.c
index a4d49760bf43..04d19e89a3e0 100644
--- a/net/ipv6/syncookies.c
+++ b/net/ipv6/syncookies.c
@@ -16,7 +16,7 @@
#include <linux/tcp.h>
#include <linux/random.h>
-#include <linux/cryptohash.h>
+#include <linux/siphash.h>
#include <linux/kernel.h>
#include <net/ipv6.h>
#include <net/tcp.h>
@@ -24,7 +24,7 @@
#define COOKIEBITS 24 /* Upper bits store count */
#define COOKIEMASK (((__u32)1 << COOKIEBITS) - 1)
-static u32 syncookie6_secret[2][16-4+SHA_DIGEST_WORDS] __read_mostly;
+static siphash_key_t syncookie6_secret[2] __read_mostly;
/* RFC 2460, Section 8.3:
* [ipv6 tcp] MSS must be computed as the maximum packet size minus 60 [..]
@@ -41,30 +41,25 @@ static __u16 const msstab[] = {
9000 - 60,
};
-static DEFINE_PER_CPU(__u32 [16 + 5 + SHA_WORKSPACE_WORDS],
ipv6_cookie_scratch);
-
static u32 cookie_hash(const struct in6_addr *saddr, const struct in6_addr
*daddr,
__be16 sport, __be16 dport, u32 count, int c)
{
- __u32 *tmp;
+ const struct {
+ struct in6_addr saddr;
+ struct in6_addr daddr;
+ u32 count;
+ u16 sport;
+ u16 dport;
+ } __aligned(SIPHASH_ALIGNMENT) combined = {
+ .saddr = *saddr,
+ .daddr = *daddr,
+ .count = count,
+ .sport = sport,
+ .dport = dport
+ };
net_get_random_once(syncookie6_secret, sizeof(syncookie6_secret));
-
- tmp = this_cpu_ptr(ipv6_cookie_scratch);
-
- /*
- * we have 320 bits of information to hash, copy in the remaining
- * 192 bits required for sha_transform, from the syncookie6_secret
- * and overwrite the digest with the secret
- */
- memcpy(tmp + 10, syncookie6_secret[c], 44);
- memcpy(tmp, saddr, 16);
- memcpy(tmp + 4, daddr, 16);
- tmp[8] = ((__force u32)sport << 16) + (__force u32)dport;
- tmp[9] = count;
- sha_transform(tmp + 16, (__u8 *)tmp, tmp + 16 + 5);
-
- return tmp[17];
+ return siphash(&combined, sizeof(combined), syncookie6_secret[c]);
}
static __u32 secure_tcp_syn_cookie(const struct in6_addr *saddr,
--
2.11.0
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