[PATCH v2 net-next 0/4] Introduce The SipHash PRF

[PATCH v2 net-next 0/4] Introduce The SipHash PRF

[Jason A. Donenfeld]

This patch series introduces SipHash into the kernel. SipHash is a
cryptographically secure PRF, which serves a variety of functions, and is
introduced in patch #1. The following patch #2 introduces HalfSipHash,
an optimization suitable for hash tables only. Finally, the last two patches
in this series show two usages of the introduced siphash function family.
It is expected that after this initial introductin, other usages will follow.

Please read the extensive descriptions in patch #1 and patch #2 of what these
functions do and the various levels of assurances. They're products of intense
cryptographic research, and I believe they're suitable for the uses outlined
herein.

The use of SipHash is not limited to the networking subsystem -- indeed I
would like to use it in other places too in the kernel. But after discussing
with a few on this list and at Linus' suggestion, the initial import of these
functions is coming through the networking tree. After these are merged, it
will then be easier to expand use elsewhere.

Changes v1->v2:
  - len in the macro is now (len).
  - siphash_key_t is now a struct, so that passing by reference is more
    obvious and clear. This required changing all the call sites.
  - Rather than calling le32_to_cpu(data[0]), where data is a u64, we now
    do the safer thing and call le32_to_cpup((const __le32 *)data).
  - The alignment in the tests is now more explicit.
  - Sparse no longer complains, after fixing up a few endian casts.
  - White space fixups.
  - Word wrapping fixes.
  - The valid suggestions from checkpatch.

Jason A. Donenfeld (4):
  siphash: add cryptographically secure PRF
  siphash: implement HalfSipHash1-3 for hash tables
  secure_seq: use SipHash in place of MD5
  syncookies: use SipHash in place of SHA1

 Documentation/siphash.txt | 154 +++++++++++++
 MAINTAINERS               |   7 +
 include/linux/siphash.h   | 145 ++++++++++++
 lib/Kconfig.debug         |   6 +-
 lib/Makefile              |   5 +-
 lib/siphash.c             | 551 ++++++++++++++++++++++++++++++++++++++++++++++
 lib/test_siphash.c        | 223 +++++++++++++++++++
 net/core/secure_seq.c     | 145 ++++++------
 net/ipv4/syncookies.c     |  21 +-
 net/ipv6/syncookies.c     |  41 ++--
 10 files changed, 1173 insertions(+), 125 deletions(-)
 create mode 100644 Documentation/siphash.txt
 create mode 100644 include/linux/siphash.h
 create mode 100644 lib/siphash.c
 create mode 100644 lib/test_siphash.c

-- 
2.11.0

[PATCH v2 net-next 1/4] siphash: add cryptographically secure PRF

[Jason A. Donenfeld]

SipHash is a 64-bit keyed hash function that is actually a
cryptographically secure PRF, like HMAC. Except SipHash is super fast,
and is meant to be used as a hashtable keyed lookup function, or as a
general PRF for short input use cases, such as sequence numbers or RNG
chaining.

For the first usage:

There are a variety of attacks known as "hashtable poisoning" in which an
attacker forms some data such that the hash of that data will be the
same, and then preceeds to fill up all entries of a hashbucket. This is
a realistic and well-known denial-of-service vector. Currently
hashtables use jhash, which is fast but not secure, and some kind of
rotating key scheme (or none at all, which isn't good). SipHash is meant
as a replacement for jhash in these cases.

There are a modicum of places in the kernel that are vulnerable to
hashtable poisoning attacks, either via userspace vectors or network
vectors, and there's not a reliable mechanism inside the kernel at the
moment to fix it. The first step toward fixing these issues is actually
getting a secure primitive into the kernel for developers to use. Then
we can, bit by bit, port things over to it as deemed appropriate.

While SipHash is extremely fast for a cryptographically secure function,
it is likely a bit slower than the insecure jhash, and so replacements
will be evaluated on a case-by-case basis based on whether or not the
difference in speed is negligible and whether or not the current jhash usage
poses a real security risk.

For the second usage:

A few places in the kernel are using MD5 or SHA1 for creating secure
sequence numbers, syn cookies, port numbers, or fast random numbers.
SipHash is a faster and more fitting, and more secure replacement for MD5
in those situations. Replacing MD5 and SHA1 with SipHash for these uses is
obvious and straight-forward, and so is submitted along with this patch
series. There shouldn't be much of a debate over its efficacy.

Dozens of languages are already using this internally for their hash
tables and PRFs. Some of the BSDs already use this in their kernels.
SipHash is a widely known high-speed solution to a widely known set of
problems, and it's time we catch-up.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Reviewed-by: Jean-Philippe Aumasson <jeanphilippe.aumasson@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Eric Biggers <ebiggers3@gmail.com>
Cc: David Laight <David.Laight@aculab.com>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
---
 Documentation/siphash.txt |  79 ++++++++++++++++
 MAINTAINERS               |   7 ++
 include/linux/siphash.h   |  85 +++++++++++++++++
 lib/Kconfig.debug         |   6 +-
 lib/Makefile              |   5 +-
 lib/siphash.c             | 232 ++++++++++++++++++++++++++++++++++++++++++++++
 lib/test_siphash.c        | 131 ++++++++++++++++++++++++++
 7 files changed, 540 insertions(+), 5 deletions(-)
 create mode 100644 Documentation/siphash.txt
 create mode 100644 include/linux/siphash.h
 create mode 100644 lib/siphash.c
 create mode 100644 lib/test_siphash.c

diff --git a/Documentation/siphash.txt b/Documentation/siphash.txt
new file mode 100644
index 000000000000..e540ab14eb8f
--- /dev/null
+++ b/Documentation/siphash.txt
@@ -0,0 +1,79 @@
+         SipHash - a short input PRF
+-----------------------------------------------
+Written by Jason A. Donenfeld <jason@zx2c4.com>
+
+SipHash is a cryptographically secure PRF -- a keyed hash function -- that
+performs very well for short inputs, hence the name. It was designed by
+cryptographers Daniel J. Bernstein and Jean-Philippe Aumasson. It is intended
+as a replacement for some uses of: `jhash`, `md5_transform`, `sha_transform`,
+and so forth.
+
+SipHash takes a secret key filled with randomly generated numbers and either
+an input buffer or several input integers. It spits out an integer that is
+indistinguishable from random. You may then use that integer as part of secure
+sequence numbers, secure cookies, or mask it off for use in a hash table.
+
+1. Generating a key
+
+Keys should always be generated from a cryptographically secure source of
+random numbers, either using get_random_bytes or get_random_once:
+
+siphash_key_t key;
+get_random_bytes(&key, sizeof(key));
+
+If you're not deriving your key from here, you're doing it wrong.
+
+2. Using the functions
+
+There are two variants of the function, one that takes a list of integers, and
+one that takes a buffer:
+
+u64 siphash(const void *data, size_t len, const siphash_key_t *key);
+
+And:
+
+u64 siphash_1u64(u64, const siphash_key_t *key);
+u64 siphash_2u64(u64, u64, const siphash_key_t *key);
+u64 siphash_3u64(u64, u64, u64, const siphash_key_t *key);
+u64 siphash_4u64(u64, u64, u64, u64, const siphash_key_t *key);
+u64 siphash_1u32(u32, const siphash_key_t *key);
+u64 siphash_2u32(u32, u32, const siphash_key_t *key);
+u64 siphash_3u32(u32, u32, u32, const siphash_key_t *key);
+u64 siphash_4u32(u32, u32, u32, u32, const siphash_key_t *key);
+
+If you pass the generic siphash function something of a constant length, it
+will constant fold at compile-time and automatically choose one of the
+optimized functions.
+
+3. Hashtable key function usage:
+
+struct some_hashtable {
+	DECLARE_HASHTABLE(hashtable, 8);
+	siphash_key_t key;
+};
+
+void init_hashtable(struct some_hashtable *table)
+{
+	get_random_bytes(&table->key, sizeof(table->key));
+}
+
+static inline hlist_head *some_hashtable_bucket(struct some_hashtable *table, struct interesting_input *input)
+{
+	return &table->hashtable[siphash(input, sizeof(*input), &table->key) & (HASH_SIZE(table->hashtable) - 1)];
+}
+
+You may then iterate like usual over the returned hash bucket.
+
+4. Security
+
+SipHash has a very high security margin, with its 128-bit key. So long as the
+key is kept secret, it is impossible for an attacker to guess the outputs of
+the function, even if being able to observe many outputs, since 2^128 outputs
+is significant.
+
+Linux implements the "2-4" variant of SipHash.
+
+5. Resources
+
+Read the SipHash paper if you're interested in learning more:
+https://131002.net/siphash/siphash.pdf
diff --git a/MAINTAINERS b/MAINTAINERS
index a136dfbb8eea..50afa1118112 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -11299,6 +11299,13 @@ F:	arch/arm/mach-s3c24xx/mach-bast.c
 F:	arch/arm/mach-s3c24xx/bast-ide.c
 F:	arch/arm/mach-s3c24xx/bast-irq.c
 
+SIPHASH PRF ROUTINES
+M:	Jason A. Donenfeld <Jason@zx2c4.com>
+S:	Maintained
+F:	lib/siphash.c
+F:	lib/test_siphash.c
+F:	include/linux/siphash.h
+
 TI DAVINCI MACHINE SUPPORT
 M:	Sekhar Nori <nsekhar@ti.com>
 M:	Kevin Hilman <khilman@kernel.org>
diff --git a/include/linux/siphash.h b/include/linux/siphash.h
new file mode 100644
index 000000000000..feeb29cd113e
--- /dev/null
+++ b/include/linux/siphash.h
@@ -0,0 +1,85 @@
+/* Copyright (C) 2016 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
+ *
+ * This file is provided under a dual BSD/GPLv2 license.
+ *
+ * SipHash: a fast short-input PRF
+ * https://131002.net/siphash/
+ *
+ * This implementation is specifically for SipHash2-4.
+ */
+
+#ifndef _LINUX_SIPHASH_H
+#define _LINUX_SIPHASH_H
+
+#include <linux/types.h>
+#include <linux/kernel.h>
+
+#define SIPHASH_ALIGNMENT __alignof__(u64)
+typedef struct {
+	u64 key[2];
+} siphash_key_t;
+
+u64 __siphash_aligned(const void *data, size_t len, const siphash_key_t *key);
+#ifndef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
+u64 __siphash_unaligned(const void *data, size_t len, const siphash_key_t *key);
+#endif
+
+u64 siphash_1u64(const u64 a, const siphash_key_t *key);
+u64 siphash_2u64(const u64 a, const u64 b, const siphash_key_t *key);
+u64 siphash_3u64(const u64 a, const u64 b, const u64 c,
+		 const siphash_key_t *key);
+u64 siphash_4u64(const u64 a, const u64 b, const u64 c, const u64 d,
+		 const siphash_key_t *key);
+u64 siphash_1u32(const u32 a, const siphash_key_t *key);
+u64 siphash_3u32(const u32 a, const u32 b, const u32 c,
+		 const siphash_key_t *key);
+
+static inline u64 siphash_2u32(const u32 a, const u32 b,
+			       const siphash_key_t *key)
+{
+	return siphash_1u64((u64)b << 32 | a, key);
+}
+static inline u64 siphash_4u32(const u32 a, const u32 b, const u32 c,
+			       const u32 d, const siphash_key_t *key)
+{
+	return siphash_2u64((u64)b << 32 | a, (u64)d << 32 | c, key);
+}
+
+
+static inline u64 ___siphash_aligned(const __le64 *data, size_t len,
+				     const siphash_key_t *key)
+{
+	if (__builtin_constant_p(len) && len == 4)
+		return siphash_1u32(le32_to_cpup((const __le32 *)data), key);
+	if (__builtin_constant_p(len) && len == 8)
+		return siphash_1u64(le64_to_cpu(data[0]), key);
+	if (__builtin_constant_p(len) && len == 16)
+		return siphash_2u64(le64_to_cpu(data[0]), le64_to_cpu(data[1]),
+				    key);
+	if (__builtin_constant_p(len) && len == 24)
+		return siphash_3u64(le64_to_cpu(data[0]), le64_to_cpu(data[1]),
+				    le64_to_cpu(data[2]), key);
+	if (__builtin_constant_p(len) && len == 32)
+		return siphash_4u64(le64_to_cpu(data[0]), le64_to_cpu(data[1]),
+				    le64_to_cpu(data[2]), le64_to_cpu(data[3]),
+				    key);
+	return __siphash_aligned(data, len, key);
+}
+
+/**
+ * siphash - compute 64-bit siphash PRF value
+ * @data: buffer to hash
+ * @size: size of @data
+ * @key: the siphash key
+ */
+static inline u64 siphash(const void *data, size_t len,
+			  const siphash_key_t *key)
+{
+#ifndef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
+	if (!IS_ALIGNED((unsigned long)data, SIPHASH_ALIGNMENT))
+		return __siphash_unaligned(data, len, key);
+#endif
+	return ___siphash_aligned(data, len, key);
+}
+
+#endif /* _LINUX_SIPHASH_H */
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index b06848a104e6..3d2515a770c3 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1819,9 +1819,9 @@ config TEST_HASH
 	tristate "Perform selftest on hash functions"
 	default n
 	help
-	  Enable this option to test the kernel's integer (<linux/hash,h>)
-	  and string (<linux/stringhash.h>) hash functions on boot
-	  (or module load).
+	  Enable this option to test the kernel's integer (<linux/hash.h>),
+	  string (<linux/stringhash.h>), and siphash (<linux/siphash.h>)
+	  hash functions on boot (or module load).
 
 	  This is intended to help people writing architecture-specific
 	  optimized versions.  If unsure, say N.
diff --git a/lib/Makefile b/lib/Makefile
index bc4073a8cd08..7b3008d58600 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -22,7 +22,8 @@ lib-y := ctype.o string.o vsprintf.o cmdline.o \
 	 sha1.o chacha20.o md5.o irq_regs.o argv_split.o \
 	 flex_proportions.o ratelimit.o show_mem.o \
 	 is_single_threaded.o plist.o decompress.o kobject_uevent.o \
-	 earlycpio.o seq_buf.o nmi_backtrace.o nodemask.o win_minmax.o
+	 earlycpio.o seq_buf.o siphash.o \
+	 nmi_backtrace.o nodemask.o win_minmax.o
 
 lib-$(CONFIG_MMU) += ioremap.o
 lib-$(CONFIG_SMP) += cpumask.o
@@ -44,7 +45,7 @@ obj-$(CONFIG_TEST_HEXDUMP) += test_hexdump.o
 obj-y += kstrtox.o
 obj-$(CONFIG_TEST_BPF) += test_bpf.o
 obj-$(CONFIG_TEST_FIRMWARE) += test_firmware.o
-obj-$(CONFIG_TEST_HASH) += test_hash.o
+obj-$(CONFIG_TEST_HASH) += test_hash.o test_siphash.o
 obj-$(CONFIG_TEST_KASAN) += test_kasan.o
 obj-$(CONFIG_TEST_KSTRTOX) += test-kstrtox.o
 obj-$(CONFIG_TEST_LKM) += test_module.o
diff --git a/lib/siphash.c b/lib/siphash.c
new file mode 100644
index 000000000000..c43cf406e71b
--- /dev/null
+++ b/lib/siphash.c
@@ -0,0 +1,232 @@
+/* Copyright (C) 2016 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
+ *
+ * This file is provided under a dual BSD/GPLv2 license.
+ *
+ * SipHash: a fast short-input PRF
+ * https://131002.net/siphash/
+ *
+ * This implementation is specifically for SipHash2-4.
+ */
+
+#include <linux/siphash.h>
+#include <asm/unaligned.h>
+
+#if defined(CONFIG_DCACHE_WORD_ACCESS) && BITS_PER_LONG == 64
+#include <linux/dcache.h>
+#include <asm/word-at-a-time.h>
+#endif
+
+#define SIPROUND \
+	do { \
+	v0 += v1; v1 = rol64(v1, 13); v1 ^= v0; v0 = rol64(v0, 32); \
+	v2 += v3; v3 = rol64(v3, 16); v3 ^= v2; \
+	v0 += v3; v3 = rol64(v3, 21); v3 ^= v0; \
+	v2 += v1; v1 = rol64(v1, 17); v1 ^= v2; v2 = rol64(v2, 32); \
+	} while (0)
+
+#define PREAMBLE(len) \
+	u64 v0 = 0x736f6d6570736575ULL; \
+	u64 v1 = 0x646f72616e646f6dULL; \
+	u64 v2 = 0x6c7967656e657261ULL; \
+	u64 v3 = 0x7465646279746573ULL; \
+	u64 b = ((u64)(len)) << 56; \
+	v3 ^= key->key[1]; \
+	v2 ^= key->key[0]; \
+	v1 ^= key->key[1]; \
+	v0 ^= key->key[0];
+
+#define POSTAMBLE \
+	v3 ^= b; \
+	SIPROUND; \
+	SIPROUND; \
+	v0 ^= b; \
+	v2 ^= 0xff; \
+	SIPROUND; \
+	SIPROUND; \
+	SIPROUND; \
+	SIPROUND; \
+	return (v0 ^ v1) ^ (v2 ^ v3);
+
+u64 __siphash_aligned(const void *data, size_t len, const siphash_key_t *key)
+{
+	const u8 *end = data + len - (len % sizeof(u64));
+	const u8 left = len & (sizeof(u64) - 1);
+	u64 m;
+	PREAMBLE(len)
+	for (; data != end; data += sizeof(u64)) {
+		m = le64_to_cpup(data);
+		v3 ^= m;
+		SIPROUND;
+		SIPROUND;
+		v0 ^= m;
+	}
+#if defined(CONFIG_DCACHE_WORD_ACCESS) && BITS_PER_LONG == 64
+	if (left)
+		b |= le64_to_cpu((__force __le64)(load_unaligned_zeropad(data) &
+						  bytemask_from_count(left)));
+#else
+	switch (left) {
+	case 7: b |= ((u64)end[6]) << 48;
+	case 6: b |= ((u64)end[5]) << 40;
+	case 5: b |= ((u64)end[4]) << 32;
+	case 4: b |= le32_to_cpup(data); break;
+	case 3: b |= ((u64)end[2]) << 16;
+	case 2: b |= le16_to_cpup(data); break;
+	case 1: b |= end[0];
+	}
+#endif
+	POSTAMBLE
+}
+EXPORT_SYMBOL(__siphash_aligned);
+
+#ifndef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
+u64 __siphash_unaligned(const void *data, size_t len, const siphash_key_t *key)
+{
+	const u8 *end = data + len - (len % sizeof(u64));
+	const u8 left = len & (sizeof(u64) - 1);
+	u64 m;
+	PREAMBLE(len)
+	for (; data != end; data += sizeof(u64)) {
+		m = get_unaligned_le64(data);
+		v3 ^= m;
+		SIPROUND;
+		SIPROUND;
+		v0 ^= m;
+	}
+#if defined(CONFIG_DCACHE_WORD_ACCESS) && BITS_PER_LONG == 64
+	if (left)
+		b |= le64_to_cpu((__force __le64)(load_unaligned_zeropad(data) &
+						  bytemask_from_count(left)));
+#else
+	switch (left) {
+	case 7: b |= ((u64)end[6]) << 48;
+	case 6: b |= ((u64)end[5]) << 40;
+	case 5: b |= ((u64)end[4]) << 32;
+	case 4: b |= get_unaligned_le32(end); break;
+	case 3: b |= ((u64)end[2]) << 16;
+	case 2: b |= get_unaligned_le16(end); break;
+	case 1: b |= end[0];
+	}
+#endif
+	POSTAMBLE
+}
+EXPORT_SYMBOL(__siphash_unaligned);
+#endif
+
+/**
+ * siphash_1u64 - compute 64-bit siphash PRF value of a u64
+ * @first: first u64
+ * @key: the siphash key
+ */
+u64 siphash_1u64(const u64 first, const siphash_key_t *key)
+{
+	PREAMBLE(8)
+	v3 ^= first;
+	SIPROUND;
+	SIPROUND;
+	v0 ^= first;
+	POSTAMBLE
+}
+EXPORT_SYMBOL(siphash_1u64);
+
+/**
+ * siphash_2u64 - compute 64-bit siphash PRF value of 2 u64
+ * @first: first u64
+ * @second: second u64
+ * @key: the siphash key
+ */
+u64 siphash_2u64(const u64 first, const u64 second, const siphash_key_t *key)
+{
+	PREAMBLE(16)
+	v3 ^= first;
+	SIPROUND;
+	SIPROUND;
+	v0 ^= first;
+	v3 ^= second;
+	SIPROUND;
+	SIPROUND;
+	v0 ^= second;
+	POSTAMBLE
+}
+EXPORT_SYMBOL(siphash_2u64);
+
+/**
+ * siphash_3u64 - compute 64-bit siphash PRF value of 3 u64
+ * @first: first u64
+ * @second: second u64
+ * @third: third u64
+ * @key: the siphash key
+ */
+u64 siphash_3u64(const u64 first, const u64 second, const u64 third,
+		 const siphash_key_t *key)
+{
+	PREAMBLE(24)
+	v3 ^= first;
+	SIPROUND;
+	SIPROUND;
+	v0 ^= first;
+	v3 ^= second;
+	SIPROUND;
+	SIPROUND;
+	v0 ^= second;
+	v3 ^= third;
+	SIPROUND;
+	SIPROUND;
+	v0 ^= third;
+	POSTAMBLE
+}
+EXPORT_SYMBOL(siphash_3u64);
+
+/**
+ * siphash_4u64 - compute 64-bit siphash PRF value of 4 u64
+ * @first: first u64
+ * @second: second u64
+ * @third: third u64
+ * @forth: forth u64
+ * @key: the siphash key
+ */
+u64 siphash_4u64(const u64 first, const u64 second, const u64 third,
+		 const u64 forth, const siphash_key_t *key)
+{
+	PREAMBLE(32)
+	v3 ^= first;
+	SIPROUND;
+	SIPROUND;
+	v0 ^= first;
+	v3 ^= second;
+	SIPROUND;
+	SIPROUND;
+	v0 ^= second;
+	v3 ^= third;
+	SIPROUND;
+	SIPROUND;
+	v0 ^= third;
+	v3 ^= forth;
+	SIPROUND;
+	SIPROUND;
+	v0 ^= forth;
+	POSTAMBLE
+}
+EXPORT_SYMBOL(siphash_4u64);
+
+u64 siphash_1u32(const u32 first, const siphash_key_t *key)
+{
+	PREAMBLE(4)
+	b |= first;
+	POSTAMBLE
+}
+EXPORT_SYMBOL(siphash_1u32);
+
+u64 siphash_3u32(const u32 first, const u32 second, const u32 third,
+		 const siphash_key_t *key)
+{
+	u64 combined = (u64)second << 32 | first;
+	PREAMBLE(12)
+	v3 ^= combined;
+	SIPROUND;
+	SIPROUND;
+	v0 ^= combined;
+	b |= third;
+	POSTAMBLE
+}
+EXPORT_SYMBOL(siphash_3u32);
diff --git a/lib/test_siphash.c b/lib/test_siphash.c
new file mode 100644
index 000000000000..d972acfc15e4
--- /dev/null
+++ b/lib/test_siphash.c
@@ -0,0 +1,131 @@
+/* Test cases for siphash.c
+ *
+ * Copyright (C) 2016 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
+ *
+ * This file is provided under a dual BSD/GPLv2 license.
+ *
+ * SipHash: a fast short-input PRF
+ * https://131002.net/siphash/
+ *
+ * This implementation is specifically for SipHash2-4.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/siphash.h>
+#include <linux/kernel.h>
+#include <linux/string.h>
+#include <linux/errno.h>
+#include <linux/module.h>
+
+/* Test vectors taken from official reference source available at:
+ *     https://131002.net/siphash/siphash24.c
+ */
+
+static const siphash_key_t test_key_siphash =
+	{{ 0x0706050403020100ULL, 0x0f0e0d0c0b0a0908ULL }};
+
+static const u64 test_vectors_siphash[64] = {
+	0x726fdb47dd0e0e31ULL, 0x74f839c593dc67fdULL, 0x0d6c8009d9a94f5aULL,
+	0x85676696d7fb7e2dULL, 0xcf2794e0277187b7ULL, 0x18765564cd99a68dULL,
+	0xcbc9466e58fee3ceULL, 0xab0200f58b01d137ULL, 0x93f5f5799a932462ULL,
+	0x9e0082df0ba9e4b0ULL, 0x7a5dbbc594ddb9f3ULL, 0xf4b32f46226bada7ULL,
+	0x751e8fbc860ee5fbULL, 0x14ea5627c0843d90ULL, 0xf723ca908e7af2eeULL,
+	0xa129ca6149be45e5ULL, 0x3f2acc7f57c29bdbULL, 0x699ae9f52cbe4794ULL,
+	0x4bc1b3f0968dd39cULL, 0xbb6dc91da77961bdULL, 0xbed65cf21aa2ee98ULL,
+	0xd0f2cbb02e3b67c7ULL, 0x93536795e3a33e88ULL, 0xa80c038ccd5ccec8ULL,
+	0xb8ad50c6f649af94ULL, 0xbce192de8a85b8eaULL, 0x17d835b85bbb15f3ULL,
+	0x2f2e6163076bcfadULL, 0xde4daaaca71dc9a5ULL, 0xa6a2506687956571ULL,
+	0xad87a3535c49ef28ULL, 0x32d892fad841c342ULL, 0x7127512f72f27cceULL,
+	0xa7f32346f95978e3ULL, 0x12e0b01abb051238ULL, 0x15e034d40fa197aeULL,
+	0x314dffbe0815a3b4ULL, 0x027990f029623981ULL, 0xcadcd4e59ef40c4dULL,
+	0x9abfd8766a33735cULL, 0x0e3ea96b5304a7d0ULL, 0xad0c42d6fc585992ULL,
+	0x187306c89bc215a9ULL, 0xd4a60abcf3792b95ULL, 0xf935451de4f21df2ULL,
+	0xa9538f0419755787ULL, 0xdb9acddff56ca510ULL, 0xd06c98cd5c0975ebULL,
+	0xe612a3cb9ecba951ULL, 0xc766e62cfcadaf96ULL, 0xee64435a9752fe72ULL,
+	0xa192d576b245165aULL, 0x0a8787bf8ecb74b2ULL, 0x81b3e73d20b49b6fULL,
+	0x7fa8220ba3b2eceaULL, 0x245731c13ca42499ULL, 0xb78dbfaf3a8d83bdULL,
+	0xea1ad565322a1a0bULL, 0x60e61c23a3795013ULL, 0x6606d7e446282b93ULL,
+	0x6ca4ecb15c5f91e1ULL, 0x9f626da15c9625f3ULL, 0xe51b38608ef25f57ULL,
+	0x958a324ceb064572ULL
+};
+
+static int __init siphash_test_init(void)
+{
+	u8 in[64] __aligned(SIPHASH_ALIGNMENT);
+	u8 in_unaligned[65] __aligned(SIPHASH_ALIGNMENT);
+	u8 i;
+	int ret = 0;
+
+	for (i = 0; i < 64; ++i) {
+		in[i] = i;
+		in_unaligned[i + 1] = i;
+		if (siphash(in, i, &test_key_siphash) !=
+						test_vectors_siphash[i]) {
+			pr_info("siphash self-test aligned %u: FAIL\n", i + 1);
+			ret = -EINVAL;
+		}
+		if (siphash(in_unaligned + 1, i, &test_key_siphash) !=
+						test_vectors_siphash[i]) {
+			pr_info("siphash self-test unaligned %u: FAIL\n", i + 1);
+			ret = -EINVAL;
+		}
+	}
+	if (siphash_1u64(0x0706050403020100ULL, &test_key_siphash) !=
+						test_vectors_siphash[8]) {
+		pr_info("siphash self-test 1u64: FAIL\n");
+		ret = -EINVAL;
+	}
+	if (siphash_2u64(0x0706050403020100ULL, 0x0f0e0d0c0b0a0908ULL,
+			 &test_key_siphash) != test_vectors_siphash[16]) {
+		pr_info("siphash self-test 2u64: FAIL\n");
+		ret = -EINVAL;
+	}
+	if (siphash_3u64(0x0706050403020100ULL, 0x0f0e0d0c0b0a0908ULL,
+			 0x1716151413121110ULL, &test_key_siphash) !=
+						test_vectors_siphash[24]) {
+		pr_info("siphash self-test 3u64: FAIL\n");
+		ret = -EINVAL;
+	}
+	if (siphash_4u64(0x0706050403020100ULL, 0x0f0e0d0c0b0a0908ULL,
+			 0x1716151413121110ULL, 0x1f1e1d1c1b1a1918ULL,
+			 &test_key_siphash) != test_vectors_siphash[32]) {
+		pr_info("siphash self-test 4u64: FAIL\n");
+		ret = -EINVAL;
+	}
+	if (siphash_1u32(0x03020100U, &test_key_siphash) !=
+						test_vectors_siphash[4]) {
+		pr_info("siphash self-test 1u32: FAIL\n");
+		ret = -EINVAL;
+	}
+	if (siphash_2u32(0x03020100U, 0x07060504U, &test_key_siphash) !=
+						test_vectors_siphash[8]) {
+		pr_info("siphash self-test 2u32: FAIL\n");
+		ret = -EINVAL;
+	}
+	if (siphash_3u32(0x03020100U, 0x07060504U,
+			 0x0b0a0908U, &test_key_siphash) !=
+						test_vectors_siphash[12]) {
+		pr_info("siphash self-test 3u32: FAIL\n");
+		ret = -EINVAL;
+	}
+	if (siphash_4u32(0x03020100U, 0x07060504U,
+			 0x0b0a0908U, 0x0f0e0d0cU, &test_key_siphash) !=
+						test_vectors_siphash[16]) {
+		pr_info("siphash self-test 4u32: FAIL\n");
+		ret = -EINVAL;
+	}
+	if (!ret)
+		pr_info("self-tests: pass\n");
+	return ret;
+}
+
+static void __exit siphash_test_exit(void)
+{
+}
+
+module_init(siphash_test_init);
+module_exit(siphash_test_exit);
+
+MODULE_AUTHOR("Jason A. Donenfeld <Jason@zx2c4.com>");
+MODULE_LICENSE("Dual BSD/GPL");
-- 
2.11.0

[PATCH v2 net-next 2/4] siphash: implement HalfSipHash1-3 for hash tables

[Jason A. Donenfeld]

HalfSipHash, or hsiphash, is a shortened version of SipHash, which
generates 32-bit outputs using a weaker 64-bit key. It has *much* lower
security margins, and shouldn't be used for anything too sensitive, but
it could be used as a hashtable key function replacement, if the output
is never exposed, and if the security requirement is not too high.

The goal is to make this something that performance-critical jhash users
would be willing to use.

On 64-bit machines, HalfSipHash1-3 is slower than SipHash1-3, so we alias
SipHash1-3 to HalfSipHash1-3 on those systems.

64-bit x86_64:
[    0.509409] test_siphash:     SipHash2-4 cycles: 4049181
[    0.510650] test_siphash:     SipHash1-3 cycles: 2512884
[    0.512205] test_siphash: HalfSipHash1-3 cycles: 3429920
[    0.512904] test_siphash:    JenkinsHash cycles:  978267
So, we map hsiphash() -> SipHash1-3

32-bit x86:
[    0.509868] test_siphash:     SipHash2-4 cycles: 14812892
[    0.513601] test_siphash:     SipHash1-3 cycles:  9510710
[    0.515263] test_siphash: HalfSipHash1-3 cycles:  3856157
[    0.515952] test_siphash:    JenkinsHash cycles:  1148567
So, we map hsiphash() -> HalfSipHash1-3

hsiphash() is roughly 3 times slower than jhash(), but comes with a
considerable security improvement.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Reviewed-by: Jean-Philippe Aumasson <jeanphilippe.aumasson@gmail.com>
---
 Documentation/siphash.txt |  75 +++++++++++
 include/linux/siphash.h   |  62 ++++++++-
 lib/siphash.c             | 321 +++++++++++++++++++++++++++++++++++++++++++++-
 lib/test_siphash.c        |  98 +++++++++++++-
 4 files changed, 551 insertions(+), 5 deletions(-)

diff --git a/Documentation/siphash.txt b/Documentation/siphash.txt
index e540ab14eb8f..4a229a1f53e5 100644
--- a/Documentation/siphash.txt
+++ b/Documentation/siphash.txt
@@ -77,3 +77,78 @@ Linux implements the "2-4" variant of SipHash.
 
 Read the SipHash paper if you're interested in learning more:
 https://131002.net/siphash/siphash.pdf
+
+
+~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=~
+
+HalfSipHash - SipHash's insecure younger cousin
+-----------------------------------------------
+Written by Jason A. Donenfeld <jason@zx2c4.com>
+
+On the off-chance that SipHash is not fast enough for your needs, you might be
+able to justify using HalfSipHash, a terrifying but potentially useful
+possibility. HalfSipHash cuts SipHash's rounds down from "2-4" to "1-3" and,
+even scarier, uses an easily brute-forcable 64-bit key (with a 32-bit output)
+instead of SipHash's 128-bit key. However, this may appeal to some
+high-performance `jhash` users.
+
+Danger!
+
+Do not ever use HalfSipHash except for as a hashtable key function, and only
+then when you can be absolutely certain that the outputs will never be
+transmitted out of the kernel. This is only remotely useful over `jhash` as a
+means of mitigating hashtable flooding denial of service attacks.
+
+1. Generating a key
+
+Keys should always be generated from a cryptographically secure source of
+random numbers, either using get_random_bytes or get_random_once:
+
+hsiphash_key_t key;
+get_random_bytes(&key, sizeof(key));
+
+If you're not deriving your key from here, you're doing it wrong.
+
+2. Using the functions
+
+There are two variants of the function, one that takes a list of integers, and
+one that takes a buffer:
+
+u32 hsiphash(const void *data, size_t len, const siphash_key_t *key);
+
+And:
+
+u32 hsiphash_1u32(u32, const hsiphash_key_t *key);
+u32 hsiphash_2u32(u32, u32, const hsiphash_key_t *key);
+u32 hsiphash_3u32(u32, u32, u32, const hsiphash_key_t *key);
+u32 hsiphash_4u32(u32, u32, u32, u32, const hsiphash_key_t *key);
+
+If you pass the generic hsiphash function something of a constant length, it
+will constant fold at compile-time and automatically choose one of the
+optimized functions.
+
+3. Hashtable key function usage:
+
+struct some_hashtable {
+	DECLARE_HASHTABLE(hashtable, 8);
+	hsiphash_key_t key;
+};
+
+void init_hashtable(struct some_hashtable *table)
+{
+	get_random_bytes(&table->key, sizeof(table->key));
+}
+
+static inline hlist_head *some_hashtable_bucket(struct some_hashtable *table, struct interesting_input *input)
+{
+	return &table->hashtable[hsiphash(input, sizeof(*input), &table->key) & (HASH_SIZE(table->hashtable) - 1)];
+}
+
+You may then iterate like usual over the returned hash bucket.
+
+4. Performance
+
+HalfSipHash is roughly 3 times slower than JenkinsHash. For many replacements,
+this will not be a problem, as the hashtable lookup isn't the bottleneck. And
+in general, this is probably a good sacrifice to make for the security and DoS
+resistance of HalfSipHash.
diff --git a/include/linux/siphash.h b/include/linux/siphash.h
index feeb29cd113e..59dccdaff4f5 100644
--- a/include/linux/siphash.h
+++ b/include/linux/siphash.h
@@ -5,7 +5,9 @@
  * SipHash: a fast short-input PRF
  * https://131002.net/siphash/
  *
- * This implementation is specifically for SipHash2-4.
+ * This implementation is specifically for SipHash2-4 for a secure PRF
+ * and HalfSipHash1-3/SipHash1-3 for an insecure PRF only suitable for
+ * hashtables.
  */
 
 #ifndef _LINUX_SIPHASH_H
@@ -82,4 +84,62 @@ static inline u64 siphash(const void *data, size_t len,
 	return ___siphash_aligned(data, len, key);
 }
 
+#if BITS_PER_LONG == 64
+typedef siphash_key_t hsiphash_key_t;
+#define HSIPHASH_ALIGNMENT SIPHASH_ALIGNMENT
+#else
+typedef struct {
+	u32 key[2];
+} hsiphash_key_t;
+#define HSIPHASH_ALIGNMENT __alignof__(u32)
+#endif
+
+u32 __hsiphash_aligned(const void *data, size_t len,
+		       const hsiphash_key_t *key);
+#ifndef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
+u32 __hsiphash_unaligned(const void *data, size_t len,
+			 const hsiphash_key_t *key);
+#endif
+
+u32 hsiphash_1u32(const u32 a, const hsiphash_key_t *key);
+u32 hsiphash_2u32(const u32 a, const u32 b, const hsiphash_key_t *key);
+u32 hsiphash_3u32(const u32 a, const u32 b, const u32 c,
+		  const hsiphash_key_t *key);
+u32 hsiphash_4u32(const u32 a, const u32 b, const u32 c, const u32 d,
+		  const hsiphash_key_t *key);
+
+static inline u32 ___hsiphash_aligned(const __le32 *data, size_t len,
+				      const hsiphash_key_t *key)
+{
+	if (__builtin_constant_p(len) && len == 4)
+		return hsiphash_1u32(le32_to_cpu(data[0]), key);
+	if (__builtin_constant_p(len) && len == 8)
+		return hsiphash_2u32(le32_to_cpu(data[0]), le32_to_cpu(data[1]),
+				     key);
+	if (__builtin_constant_p(len) && len == 12)
+		return hsiphash_3u32(le32_to_cpu(data[0]), le32_to_cpu(data[1]),
+				     le32_to_cpu(data[2]), key);
+	if (__builtin_constant_p(len) && len == 16)
+		return hsiphash_4u32(le32_to_cpu(data[0]), le32_to_cpu(data[1]),
+				     le32_to_cpu(data[2]), le32_to_cpu(data[3]),
+				     key);
+	return __hsiphash_aligned(data, len, key);
+}
+
+/**
+ * hsiphash - compute 32-bit hsiphash PRF value
+ * @data: buffer to hash
+ * @size: size of @data
+ * @key: the hsiphash key
+ */
+static inline u32 hsiphash(const void *data, size_t len,
+			   const hsiphash_key_t *key)
+{
+#ifndef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
+	if (!IS_ALIGNED((unsigned long)data, HSIPHASH_ALIGNMENT))
+		return __hsiphash_unaligned(data, len, key);
+#endif
+	return ___hsiphash_aligned(data, len, key);
+}
+
 #endif /* _LINUX_SIPHASH_H */
diff --git a/lib/siphash.c b/lib/siphash.c
index c43cf406e71b..3ae58b4edad6 100644
--- a/lib/siphash.c
+++ b/lib/siphash.c
@@ -5,7 +5,9 @@
  * SipHash: a fast short-input PRF
  * https://131002.net/siphash/
  *
- * This implementation is specifically for SipHash2-4.
+ * This implementation is specifically for SipHash2-4 for a secure PRF
+ * and HalfSipHash1-3/SipHash1-3 for an insecure PRF only suitable for
+ * hashtables.
  */
 
 #include <linux/siphash.h>
@@ -230,3 +232,320 @@ u64 siphash_3u32(const u32 first, const u32 second, const u32 third,
 	POSTAMBLE
 }
 EXPORT_SYMBOL(siphash_3u32);
+
+#if BITS_PER_LONG == 64
+/* Note that on 64-bit, we make HalfSipHash1-3 actually be SipHash1-3, for
+ * performance reasons. On 32-bit, below, we actually implement HalfSipHash1-3.
+ */
+
+#define HSIPROUND SIPROUND
+#define HPREAMBLE(len) PREAMBLE(len)
+#define HPOSTAMBLE \
+	v3 ^= b; \
+	HSIPROUND; \
+	v0 ^= b; \
+	v2 ^= 0xff; \
+	HSIPROUND; \
+	HSIPROUND; \
+	HSIPROUND; \
+	return (v0 ^ v1) ^ (v2 ^ v3);
+
+u32 __hsiphash_aligned(const void *data, size_t len, const hsiphash_key_t *key)
+{
+	const u8 *end = data + len - (len % sizeof(u64));
+	const u8 left = len & (sizeof(u64) - 1);
+	u64 m;
+	HPREAMBLE(len)
+	for (; data != end; data += sizeof(u64)) {
+		m = le64_to_cpup(data);
+		v3 ^= m;
+		HSIPROUND;
+		v0 ^= m;
+	}
+#if defined(CONFIG_DCACHE_WORD_ACCESS) && BITS_PER_LONG == 64
+	if (left)
+		b |= le64_to_cpu((__force __le64)(load_unaligned_zeropad(data) &
+						  bytemask_from_count(left)));
+#else
+	switch (left) {
+	case 7: b |= ((u64)end[6]) << 48;
+	case 6: b |= ((u64)end[5]) << 40;
+	case 5: b |= ((u64)end[4]) << 32;
+	case 4: b |= le32_to_cpup(data); break;
+	case 3: b |= ((u64)end[2]) << 16;
+	case 2: b |= le16_to_cpup(data); break;
+	case 1: b |= end[0];
+	}
+#endif
+	HPOSTAMBLE
+}
+EXPORT_SYMBOL(__hsiphash_aligned);
+
+#ifndef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
+u32 __hsiphash_unaligned(const void *data, size_t len,
+			 const hsiphash_key_t *key)
+{
+	const u8 *end = data + len - (len % sizeof(u64));
+	const u8 left = len & (sizeof(u64) - 1);
+	u64 m;
+	HPREAMBLE(len)
+	for (; data != end; data += sizeof(u64)) {
+		m = get_unaligned_le64(data);
+		v3 ^= m;
+		HSIPROUND;
+		v0 ^= m;
+	}
+#if defined(CONFIG_DCACHE_WORD_ACCESS) && BITS_PER_LONG == 64
+	if (left)
+		b |= le64_to_cpu((__force __le64)(load_unaligned_zeropad(data) &
+						  bytemask_from_count(left)));
+#else
+	switch (left) {
+	case 7: b |= ((u64)end[6]) << 48;
+	case 6: b |= ((u64)end[5]) << 40;
+	case 5: b |= ((u64)end[4]) << 32;
+	case 4: b |= get_unaligned_le32(end); break;
+	case 3: b |= ((u64)end[2]) << 16;
+	case 2: b |= get_unaligned_le16(end); break;
+	case 1: b |= end[0];
+	}
+#endif
+	HPOSTAMBLE
+}
+EXPORT_SYMBOL(__hsiphash_unaligned);
+#endif
+
+/**
+ * hsiphash_1u32 - compute 64-bit hsiphash PRF value of a u32
+ * @first: first u32
+ * @key: the hsiphash key
+ */
+u32 hsiphash_1u32(const u32 first, const hsiphash_key_t *key)
+{
+	HPREAMBLE(4)
+	b |= first;
+	HPOSTAMBLE
+}
+EXPORT_SYMBOL(hsiphash_1u32);
+
+/**
+ * hsiphash_2u32 - compute 32-bit hsiphash PRF value of 2 u32
+ * @first: first u32
+ * @second: second u32
+ * @key: the hsiphash key
+ */
+u32 hsiphash_2u32(const u32 first, const u32 second, const hsiphash_key_t *key)
+{
+	u64 combined = (u64)second << 32 | first;
+	HPREAMBLE(8)
+	v3 ^= combined;
+	HSIPROUND;
+	v0 ^= combined;
+	HPOSTAMBLE
+}
+EXPORT_SYMBOL(hsiphash_2u32);
+
+/**
+ * hsiphash_3u32 - compute 32-bit hsiphash PRF value of 3 u32
+ * @first: first u32
+ * @second: second u32
+ * @third: third u32
+ * @key: the hsiphash key
+ */
+u32 hsiphash_3u32(const u32 first, const u32 second, const u32 third,
+		  const hsiphash_key_t *key)
+{
+	u64 combined = (u64)second << 32 | first;
+	HPREAMBLE(12)
+	v3 ^= combined;
+	HSIPROUND;
+	v0 ^= combined;
+	b |= third;
+	HPOSTAMBLE
+}
+EXPORT_SYMBOL(hsiphash_3u32);
+
+/**
+ * hsiphash_4u32 - compute 32-bit hsiphash PRF value of 4 u32
+ * @first: first u32
+ * @second: second u32
+ * @third: third u32
+ * @forth: forth u32
+ * @key: the hsiphash key
+ */
+u32 hsiphash_4u32(const u32 first, const u32 second, const u32 third,
+		  const u32 forth, const hsiphash_key_t *key)
+{
+	u64 combined = (u64)second << 32 | first;
+	HPREAMBLE(16)
+	v3 ^= combined;
+	HSIPROUND;
+	v0 ^= combined;
+	combined = (u64)forth << 32 | third;
+	v3 ^= combined;
+	HSIPROUND;
+	v0 ^= combined;
+	HPOSTAMBLE
+}
+EXPORT_SYMBOL(hsiphash_4u32);
+#else
+#define HSIPROUND \
+	do { \
+	v0 += v1; v1 = rol32(v1, 5); v1 ^= v0; v0 = rol32(v0, 16); \
+	v2 += v3; v3 = rol32(v3, 8); v3 ^= v2; \
+	v0 += v3; v3 = rol32(v3, 7); v3 ^= v0; \
+	v2 += v1; v1 = rol32(v1, 13); v1 ^= v2; v2 = rol32(v2, 16); \
+	} while (0)
+
+#define HPREAMBLE(len) \
+	u32 v0 = 0; \
+	u32 v1 = 0; \
+	u32 v2 = 0x6c796765U; \
+	u32 v3 = 0x74656462U; \
+	u32 b = ((u32)(len)) << 24; \
+	v3 ^= key->key[1]; \
+	v2 ^= key->key[0]; \
+	v1 ^= key->key[1]; \
+	v0 ^= key->key[0];
+
+#define HPOSTAMBLE \
+	v3 ^= b; \
+	HSIPROUND; \
+	v0 ^= b; \
+	v2 ^= 0xff; \
+	HSIPROUND; \
+	HSIPROUND; \
+	HSIPROUND; \
+	return v1 ^ v3;
+
+u32 __hsiphash_aligned(const void *data, size_t len, const hsiphash_key_t *key)
+{
+	const u8 *end = data + len - (len % sizeof(u32));
+	const u8 left = len & (sizeof(u32) - 1);
+	u32 m;
+	HPREAMBLE(len)
+	for (; data != end; data += sizeof(u32)) {
+		m = le32_to_cpup(data);
+		v3 ^= m;
+		HSIPROUND;
+		v0 ^= m;
+	}
+	switch (left) {
+	case 3: b |= ((u32)end[2]) << 16;
+	case 2: b |= le16_to_cpup(data); break;
+	case 1: b |= end[0];
+	}
+	HPOSTAMBLE
+}
+EXPORT_SYMBOL(__hsiphash_aligned);
+
+#ifndef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
+u32 __hsiphash_unaligned(const void *data, size_t len,
+			 const hsiphash_key_t *key)
+{
+	const u8 *end = data + len - (len % sizeof(u32));
+	const u8 left = len & (sizeof(u32) - 1);
+	u32 m;
+	HPREAMBLE(len)
+	for (; data != end; data += sizeof(u32)) {
+		m = get_unaligned_le32(data);
+		v3 ^= m;
+		HSIPROUND;
+		v0 ^= m;
+	}
+	switch (left) {
+	case 3: b |= ((u32)end[2]) << 16;
+	case 2: b |= get_unaligned_le16(end); break;
+	case 1: b |= end[0];
+	}
+	HPOSTAMBLE
+}
+EXPORT_SYMBOL(__hsiphash_unaligned);
+#endif
+
+/**
+ * hsiphash_1u32 - compute 32-bit hsiphash PRF value of a u32
+ * @first: first u32
+ * @key: the hsiphash key
+ */
+u32 hsiphash_1u32(const u32 first, const hsiphash_key_t *key)
+{
+	HPREAMBLE(4)
+	v3 ^= first;
+	HSIPROUND;
+	v0 ^= first;
+	HPOSTAMBLE
+}
+EXPORT_SYMBOL(hsiphash_1u32);
+
+/**
+ * hsiphash_2u32 - compute 32-bit hsiphash PRF value of 2 u32
+ * @first: first u32
+ * @second: second u32
+ * @key: the hsiphash key
+ */
+u32 hsiphash_2u32(const u32 first, const u32 second, const hsiphash_key_t *key)
+{
+	HPREAMBLE(8)
+	v3 ^= first;
+	HSIPROUND;
+	v0 ^= first;
+	v3 ^= second;
+	HSIPROUND;
+	v0 ^= second;
+	HPOSTAMBLE
+}
+EXPORT_SYMBOL(hsiphash_2u32);
+
+/**
+ * hsiphash_3u32 - compute 32-bit hsiphash PRF value of 3 u32
+ * @first: first u32
+ * @second: second u32
+ * @third: third u32
+ * @key: the hsiphash key
+ */
+u32 hsiphash_3u32(const u32 first, const u32 second, const u32 third,
+		  const hsiphash_key_t *key)
+{
+	HPREAMBLE(12)
+	v3 ^= first;
+	HSIPROUND;
+	v0 ^= first;
+	v3 ^= second;
+	HSIPROUND;
+	v0 ^= second;
+	v3 ^= third;
+	HSIPROUND;
+	v0 ^= third;
+	HPOSTAMBLE
+}
+EXPORT_SYMBOL(hsiphash_3u32);
+
+/**
+ * hsiphash_4u32 - compute 32-bit hsiphash PRF value of 4 u32
+ * @first: first u32
+ * @second: second u32
+ * @third: third u32
+ * @forth: forth u32
+ * @key: the hsiphash key
+ */
+u32 hsiphash_4u32(const u32 first, const u32 second, const u32 third,
+		  const u32 forth, const hsiphash_key_t *key)
+{
+	HPREAMBLE(16)
+	v3 ^= first;
+	HSIPROUND;
+	v0 ^= first;
+	v3 ^= second;
+	HSIPROUND;
+	v0 ^= second;
+	v3 ^= third;
+	HSIPROUND;
+	v0 ^= third;
+	v3 ^= forth;
+	HSIPROUND;
+	v0 ^= forth;
+	HPOSTAMBLE
+}
+EXPORT_SYMBOL(hsiphash_4u32);
+#endif
diff --git a/lib/test_siphash.c b/lib/test_siphash.c
index d972acfc15e4..a6d854d933bf 100644
--- a/lib/test_siphash.c
+++ b/lib/test_siphash.c
@@ -7,7 +7,9 @@
  * SipHash: a fast short-input PRF
  * https://131002.net/siphash/
  *
- * This implementation is specifically for SipHash2-4.
+ * This implementation is specifically for SipHash2-4 for a secure PRF
+ * and HalfSipHash1-3/SipHash1-3 for an insecure PRF only suitable for
+ * hashtables.
  */
 
 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
@@ -18,8 +20,8 @@
 #include <linux/errno.h>
 #include <linux/module.h>
 
-/* Test vectors taken from official reference source available at:
- *     https://131002.net/siphash/siphash24.c
+/* Test vectors taken from reference source available at:
+ *     https://github.com/veorq/SipHash
  */
 
 static const siphash_key_t test_key_siphash =
@@ -50,6 +52,64 @@ static const u64 test_vectors_siphash[64] = {
 	0x958a324ceb064572ULL
 };
 
+#if BITS_PER_LONG == 64
+static const hsiphash_key_t test_key_hsiphash =
+	{{ 0x0706050403020100ULL, 0x0f0e0d0c0b0a0908ULL }};
+
+static const u32 test_vectors_hsiphash[64] = {
+	0x050fc4dcU, 0x7d57ca93U, 0x4dc7d44dU,
+	0xe7ddf7fbU, 0x88d38328U, 0x49533b67U,
+	0xc59f22a7U, 0x9bb11140U, 0x8d299a8eU,
+	0x6c063de4U, 0x92ff097fU, 0xf94dc352U,
+	0x57b4d9a2U, 0x1229ffa7U, 0xc0f95d34U,
+	0x2a519956U, 0x7d908b66U, 0x63dbd80cU,
+	0xb473e63eU, 0x8d297d1cU, 0xa6cce040U,
+	0x2b45f844U, 0xa320872eU, 0xdae6c123U,
+	0x67349c8cU, 0x705b0979U, 0xca9913a5U,
+	0x4ade3b35U, 0xef6cd00dU, 0x4ab1e1f4U,
+	0x43c5e663U, 0x8c21d1bcU, 0x16a7b60dU,
+	0x7a8ff9bfU, 0x1f2a753eU, 0xbf186b91U,
+	0xada26206U, 0xa3c33057U, 0xae3a36a1U,
+	0x7b108392U, 0x99e41531U, 0x3f1ad944U,
+	0xc8138825U, 0xc28949a6U, 0xfaf8876bU,
+	0x9f042196U, 0x68b1d623U, 0x8b5114fdU,
+	0xdf074c46U, 0x12cc86b3U, 0x0a52098fU,
+	0x9d292f9aU, 0xa2f41f12U, 0x43a71ed0U,
+	0x73f0bce6U, 0x70a7e980U, 0x243c6d75U,
+	0xfdb71513U, 0xa67d8a08U, 0xb7e8f148U,
+	0xf7a644eeU, 0x0f1837f2U, 0x4b6694e0U,
+	0xb7bbb3a8U
+};
+#else
+static const hsiphash_key_t test_key_hsiphash =
+	{{ 0x03020100U, 0x07060504U }};
+
+static const u32 test_vectors_hsiphash[64] = {
+	0x5814c896U, 0xe7e864caU, 0xbc4b0e30U,
+	0x01539939U, 0x7e059ea6U, 0x88e3d89bU,
+	0xa0080b65U, 0x9d38d9d6U, 0x577999b1U,
+	0xc839caedU, 0xe4fa32cfU, 0x959246eeU,
+	0x6b28096cU, 0x66dd9cd6U, 0x16658a7cU,
+	0xd0257b04U, 0x8b31d501U, 0x2b1cd04bU,
+	0x06712339U, 0x522aca67U, 0x911bb605U,
+	0x90a65f0eU, 0xf826ef7bU, 0x62512debU,
+	0x57150ad7U, 0x5d473507U, 0x1ec47442U,
+	0xab64afd3U, 0x0a4100d0U, 0x6d2ce652U,
+	0x2331b6a3U, 0x08d8791aU, 0xbc6dda8dU,
+	0xe0f6c934U, 0xb0652033U, 0x9b9851ccU,
+	0x7c46fb7fU, 0x732ba8cbU, 0xf142997aU,
+	0xfcc9aa1bU, 0x05327eb2U, 0xe110131cU,
+	0xf9e5e7c0U, 0xa7d708a6U, 0x11795ab1U,
+	0x65671619U, 0x9f5fff91U, 0xd89c5267U,
+	0x007783ebU, 0x95766243U, 0xab639262U,
+	0x9c7e1390U, 0xc368dda6U, 0x38ddc455U,
+	0xfa13d379U, 0x979ea4e8U, 0x53ecd77eU,
+	0x2ee80657U, 0x33dbb66aU, 0xae3f0577U,
+	0x88b4c4ccU, 0x3e7f480bU, 0x74c1ebf8U,
+	0x87178304U
+};
+#endif
+
 static int __init siphash_test_init(void)
 {
 	u8 in[64] __aligned(SIPHASH_ALIGNMENT);
@@ -70,6 +130,16 @@ static int __init siphash_test_init(void)
 			pr_info("siphash self-test unaligned %u: FAIL\n", i + 1);
 			ret = -EINVAL;
 		}
+		if (hsiphash(in, i, &test_key_hsiphash) !=
+						test_vectors_hsiphash[i]) {
+			pr_info("hsiphash self-test aligned %u: FAIL\n", i + 1);
+			ret = -EINVAL;
+		}
+		if (hsiphash(in_unaligned + 1, i, &test_key_hsiphash) !=
+						test_vectors_hsiphash[i]) {
+			pr_info("hsiphash self-test unaligned %u: FAIL\n", i + 1);
+			ret = -EINVAL;
+		}
 	}
 	if (siphash_1u64(0x0706050403020100ULL, &test_key_siphash) !=
 						test_vectors_siphash[8]) {
@@ -115,6 +185,28 @@ static int __init siphash_test_init(void)
 		pr_info("siphash self-test 4u32: FAIL\n");
 		ret = -EINVAL;
 	}
+	if (hsiphash_1u32(0x03020100U, &test_key_hsiphash) !=
+						test_vectors_hsiphash[4]) {
+		pr_info("hsiphash self-test 1u32: FAIL\n");
+		ret = -EINVAL;
+	}
+	if (hsiphash_2u32(0x03020100U, 0x07060504U, &test_key_hsiphash) !=
+						test_vectors_hsiphash[8]) {
+		pr_info("hsiphash self-test 2u32: FAIL\n");
+		ret = -EINVAL;
+	}
+	if (hsiphash_3u32(0x03020100U, 0x07060504U,
+			  0x0b0a0908U, &test_key_hsiphash) !=
+						test_vectors_hsiphash[12]) {
+		pr_info("hsiphash self-test 3u32: FAIL\n");
+		ret = -EINVAL;
+	}
+	if (hsiphash_4u32(0x03020100U, 0x07060504U,
+			  0x0b0a0908U, 0x0f0e0d0cU, &test_key_hsiphash) !=
+						test_vectors_hsiphash[16]) {
+		pr_info("hsiphash self-test 4u32: FAIL\n");
+		ret = -EINVAL;
+	}
 	if (!ret)
 		pr_info("self-tests: pass\n");
 	return ret;
-- 
2.11.0

[PATCH v2 net-next 3/4] secure_seq: use SipHash in place of MD5

[Jason A. Donenfeld]

This gives a clear speed and security improvement. Siphash is both
faster and is more solid crypto than the aging MD5.

Rather than manually filling MD5 buffers, for IPv6, we simply create
a layout by a simple anonymous struct, for which gcc generates
rather efficient code. For IPv4, we pass the values directly to the
short input convenience functions.

64-bit x86_64:
[    1.683628] secure_tcpv6_sequence_number_md5# cycles: 99563527
[    1.717350] secure_tcp_sequence_number_md5# cycles: 92890502
[    1.741968] secure_tcpv6_sequence_number_siphash# cycles: 67825362
[    1.762048] secure_tcp_sequence_number_siphash# cycles: 67485526

32-bit x86:
[    1.600012] secure_tcpv6_sequence_number_md5# cycles: 103227892
[    1.634219] secure_tcp_sequence_number_md5# cycles: 94732544
[    1.669102] secure_tcpv6_sequence_number_siphash# cycles: 96299384
[    1.700165] secure_tcp_sequence_number_siphash# cycles: 86015473

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: David Miller <davem@davemloft.net>
Cc: David Laight <David.Laight@aculab.com>
Cc: Tom Herbert <tom@herbertland.com>
Cc: Hannes Frederic Sowa <hannes@stressinduktion.org>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
---
 net/core/secure_seq.c | 145 ++++++++++++++++++++++----------------------------
 1 file changed, 63 insertions(+), 82 deletions(-)

diff --git a/net/core/secure_seq.c b/net/core/secure_seq.c
index 88a8e429fc3e..119e3ebe2f30 100644
--- a/net/core/secure_seq.c
+++ b/net/core/secure_seq.c
@@ -1,3 +1,7 @@
+/*
+ * Copyright (C) 2016 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
+ */
+
 #include <linux/kernel.h>
 #include <linux/init.h>
 #include <linux/cryptohash.h>
@@ -8,18 +12,18 @@
 #include <linux/ktime.h>
 #include <linux/string.h>
 #include <linux/net.h>
-
+#include <linux/siphash.h>
 #include <net/secure_seq.h>
 
 #if IS_ENABLED(CONFIG_IPV6) || IS_ENABLED(CONFIG_INET)
+#include <linux/in6.h>
 #include <net/tcp.h>
-#define NET_SECRET_SIZE (MD5_MESSAGE_BYTES / 4)
 
-static u32 net_secret[NET_SECRET_SIZE] ____cacheline_aligned;
+static siphash_key_t net_secret;
 
 static __always_inline void net_secret_init(void)
 {
-	net_get_random_once(net_secret, sizeof(net_secret));
+	net_get_random_once(&net_secret, sizeof(net_secret));
 }
 #endif
 
@@ -44,80 +48,70 @@ static u32 seq_scale(u32 seq)
 u32 secure_tcpv6_sequence_number(const __be32 *saddr, const __be32 *daddr,
 				 __be16 sport, __be16 dport, u32 *tsoff)
 {
-	u32 secret[MD5_MESSAGE_BYTES / 4];
-	u32 hash[MD5_DIGEST_WORDS];
-	u32 i;
-
+	const struct {
+		struct in6_addr saddr;
+		struct in6_addr daddr;
+		__be16 sport;
+		__be16 dport;
+	} __aligned(SIPHASH_ALIGNMENT) combined = {
+		.saddr = *(struct in6_addr *)saddr,
+		.daddr = *(struct in6_addr *)daddr,
+		.sport = sport,
+		.dport = dport
+	};
+	u64 hash;
 	net_secret_init();
-	memcpy(hash, saddr, 16);
-	for (i = 0; i < 4; i++)
-		secret[i] = net_secret[i] + (__force u32)daddr[i];
-	secret[4] = net_secret[4] +
-		(((__force u16)sport << 16) + (__force u16)dport);
-	for (i = 5; i < MD5_MESSAGE_BYTES / 4; i++)
-		secret[i] = net_secret[i];
-
-	md5_transform(hash, secret);
-
-	*tsoff = sysctl_tcp_timestamps == 1 ? hash[1] : 0;
-	return seq_scale(hash[0]);
+	hash = siphash(&combined, offsetofend(typeof(combined), dport),
+		       &net_secret);
+	*tsoff = sysctl_tcp_timestamps == 1 ? (hash >> 32) : 0;
+	return seq_scale(hash);
 }
 EXPORT_SYMBOL(secure_tcpv6_sequence_number);
 
 u32 secure_ipv6_port_ephemeral(const __be32 *saddr, const __be32 *daddr,
 			       __be16 dport)
 {
-	u32 secret[MD5_MESSAGE_BYTES / 4];
-	u32 hash[MD5_DIGEST_WORDS];
-	u32 i;
-
+	const struct {
+		struct in6_addr saddr;
+		struct in6_addr daddr;
+		__be16 dport;
+	} __aligned(SIPHASH_ALIGNMENT) combined = {
+		.saddr = *(struct in6_addr *)saddr,
+		.daddr = *(struct in6_addr *)daddr,
+		.dport = dport
+	};
 	net_secret_init();
-	memcpy(hash, saddr, 16);
-	for (i = 0; i < 4; i++)
-		secret[i] = net_secret[i] + (__force u32) daddr[i];
-	secret[4] = net_secret[4] + (__force u32)dport;
-	for (i = 5; i < MD5_MESSAGE_BYTES / 4; i++)
-		secret[i] = net_secret[i];
-
-	md5_transform(hash, secret);
-
-	return hash[0];
+	return siphash(&combined, offsetofend(typeof(combined), dport),
+		       &net_secret);
 }
 EXPORT_SYMBOL(secure_ipv6_port_ephemeral);
 #endif
 
 #ifdef CONFIG_INET
 
+/* secure_tcp_sequence_number(a, b, 0, d) == secure_ipv4_port_ephemeral(a, b, d),
+ * but fortunately, `sport' cannot be 0 in any circumstances. If this changes,
+ * it would be easy enough to have the former function use siphash_4u32, passing
+ * the arguments as separate u32.
+ */
+
 u32 secure_tcp_sequence_number(__be32 saddr, __be32 daddr,
 			       __be16 sport, __be16 dport, u32 *tsoff)
 {
-	u32 hash[MD5_DIGEST_WORDS];
-
+	u64 hash;
 	net_secret_init();
-	hash[0] = (__force u32)saddr;
-	hash[1] = (__force u32)daddr;
-	hash[2] = ((__force u16)sport << 16) + (__force u16)dport;
-	hash[3] = net_secret[15];
-
-	md5_transform(hash, net_secret);
-
-	*tsoff = sysctl_tcp_timestamps == 1 ? hash[1] : 0;
-	return seq_scale(hash[0]);
+	hash = siphash_3u32((__force u32)saddr, (__force u32)daddr,
+			    (__force u32)sport << 16 | (__force u32)dport,
+			    &net_secret);
+	*tsoff = sysctl_tcp_timestamps == 1 ? (hash >> 32) : 0;
+	return seq_scale(hash);
 }
 
 u32 secure_ipv4_port_ephemeral(__be32 saddr, __be32 daddr, __be16 dport)
 {
-	u32 hash[MD5_DIGEST_WORDS];
-
 	net_secret_init();
-	hash[0] = (__force u32)saddr;
-	hash[1] = (__force u32)daddr;
-	hash[2] = (__force u32)dport ^ net_secret[14];
-	hash[3] = net_secret[15];
-
-	md5_transform(hash, net_secret);
-
-	return hash[0];
+	return siphash_3u32((__force u32)saddr, (__force u32)daddr,
+			    (__force u16)dport, &net_secret);
 }
 EXPORT_SYMBOL_GPL(secure_ipv4_port_ephemeral);
 #endif
@@ -126,21 +120,11 @@ EXPORT_SYMBOL_GPL(secure_ipv4_port_ephemeral);
 u64 secure_dccp_sequence_number(__be32 saddr, __be32 daddr,
 				__be16 sport, __be16 dport)
 {
-	u32 hash[MD5_DIGEST_WORDS];
 	u64 seq;
-
 	net_secret_init();
-	hash[0] = (__force u32)saddr;
-	hash[1] = (__force u32)daddr;
-	hash[2] = ((__force u16)sport << 16) + (__force u16)dport;
-	hash[3] = net_secret[15];
-
-	md5_transform(hash, net_secret);
-
-	seq = hash[0] | (((u64)hash[1]) << 32);
+	seq = siphash_3u32(saddr, daddr, (u32)sport << 16 | dport, &net_secret);
 	seq += ktime_get_real_ns();
 	seq &= (1ull << 48) - 1;
-
 	return seq;
 }
 EXPORT_SYMBOL(secure_dccp_sequence_number);
@@ -149,26 +133,23 @@ EXPORT_SYMBOL(secure_dccp_sequence_number);
 u64 secure_dccpv6_sequence_number(__be32 *saddr, __be32 *daddr,
 				  __be16 sport, __be16 dport)
 {
-	u32 secret[MD5_MESSAGE_BYTES / 4];
-	u32 hash[MD5_DIGEST_WORDS];
+	const struct {
+		struct in6_addr saddr;
+		struct in6_addr daddr;
+		__be16 sport;
+		__be16 dport;
+	} __aligned(SIPHASH_ALIGNMENT) combined = {
+		.saddr = *(struct in6_addr *)saddr,
+		.daddr = *(struct in6_addr *)daddr,
+		.sport = sport,
+		.dport = dport
+	};
 	u64 seq;
-	u32 i;
-
 	net_secret_init();
-	memcpy(hash, saddr, 16);
-	for (i = 0; i < 4; i++)
-		secret[i] = net_secret[i] + (__force u32)daddr[i];
-	secret[4] = net_secret[4] +
-		(((__force u16)sport << 16) + (__force u16)dport);
-	for (i = 5; i < MD5_MESSAGE_BYTES / 4; i++)
-		secret[i] = net_secret[i];
-
-	md5_transform(hash, secret);
-
-	seq = hash[0] | (((u64)hash[1]) << 32);
+	seq = siphash(&combined, offsetofend(typeof(combined), dport),
+		      &net_secret);
 	seq += ktime_get_real_ns();
 	seq &= (1ull << 48) - 1;
-
 	return seq;
 }
 EXPORT_SYMBOL(secure_dccpv6_sequence_number);
-- 
2.11.0

[PATCH v2 net-next 4/4] syncookies: use SipHash in place of SHA1

[Jason A. Donenfeld]

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.

The speedup should be similar -- and even more impressive -- to the
speedup from the sequence number fix in this series.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Cc: David Miller <davem@davemloft.net>
---
 net/ipv4/syncookies.c | 21 +++++----------------
 net/ipv6/syncookies.c | 41 +++++++++++++++++++----------------------
 2 files changed, 24 insertions(+), 38 deletions(-)

diff --git a/net/ipv4/syncookies.c b/net/ipv4/syncookies.c
index 3e88467d70ee..496b97e17aaf 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 +48,13 @@ 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((__force u32)saddr, (__force u32)daddr,
+			    (__force u32)sport << 16 | (__force u32)dport,
+			    count, &syncookie_secret[c]);
 }
 
 
diff --git a/net/ipv6/syncookies.c b/net/ipv6/syncookies.c
index a4d49760bf43..895ff650db43 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 +41,27 @@ 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,
+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;
+		__be16 sport;
+		__be16 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, offsetofend(typeof(combined), dport),
+		       &syncookie6_secret[c]);
 }
 
 static __u32 secure_tcp_syn_cookie(const struct in6_addr *saddr,
-- 
2.11.0

Re: [PATCH v2 net-next 0/4] Introduce The SipHash PRF

[Eric Biggers]

On Sat, Jan 07, 2017 at 03:40:53PM +0100, Jason A. Donenfeld wrote:
> This patch series introduces SipHash into the kernel. SipHash is a
> cryptographically secure PRF, which serves a variety of functions, and is
> introduced in patch #1. The following patch #2 introduces HalfSipHash,
> an optimization suitable for hash tables only. Finally, the last two patches
> in this series show two usages of the introduced siphash function family.
> It is expected that after this initial introductin, other usages will follow.
...
> The use of SipHash is not limited to the networking subsystem -- indeed I
> would like to use it in other places too in the kernel. But after discussing
> with a few on this list and at Linus' suggestion, the initial import of these
> functions is coming through the networking tree. After these are merged, it
> will then be easier to expand use elsewhere.
> 
> Changes v1->v2:
>   - len in the macro is now (len).
>   - siphash_key_t is now a struct, so that passing by reference is more
>     obvious and clear. This required changing all the call sites.
>   - Rather than calling le32_to_cpu(data[0]), where data is a u64, we now
>     do the safer thing and call le32_to_cpup((const __le32 *)data).
>   - The alignment in the tests is now more explicit.
>   - Sparse no longer complains, after fixing up a few endian casts.
>   - White space fixups.
>   - Word wrapping fixes.
>   - The valid suggestions from checkpatch.

Hi Jason, thanks for doing this!  Yes, I had gotten a little lost in the earlier
discussions about the 'random' driver and other potential users of SipHash.  I
agree with the approach to just introduce the two uses in net/ to start with,
and introduce more users later.  The changes from v1 to v2 look good too.

Now that the HalfSipHash patch is Cc'ed to me too I do have one other small
suggestion which is that this:

	#if BITS_PER_LONG == 64
	typedef siphash_key_t hsiphash_key_t;
	#define HSIPHASH_ALIGNMENT SIPHASH_ALIGNMENT
	#else
	typedef struct {
		u32 key[2];
	} hsiphash_key_t;
	#define HSIPHASH_ALIGNMENT __alignof__(u32)
	#endif

could cause confusion if someone accidentally uses 'siphash_key_t' instead of
'hsiphash_key_t', as their code would compile fine on a 64-bit platform but
would fail to compile on a 32-bit platform.  I think there should just always be
a hsiphash_key_t struct defined, and it can use unsigned long (no need for an
#ifdef):

	#define HSIPHASH_ALIGNMENT __alignof__(unsigned long)
	typedef struct {
		unsigned long key[2];
	} hsiphash_key_t;

There's also a small error in Documentation/siphash.txt: hsiphash() is shown as
taking siphash_key_t instead of hsiphash_key_t.

The uses in net look good too.  Something to watch out for is accidentally
defining the structs in a way that leaves internal padding bytes, which could
theoretically take on any value and cause the same input to produce different
hashes.  But AFAICS, in the proposed patch all the structs are laid out
properly, so that won't happen.

'net_secret' could also be marked as __read_mostly, like the keys in
syncookies.c, I suppose; it may not matter much.

Thanks!

Eric

Re: [PATCH v2 net-next 3/4] secure_seq: use SipHash in place of MD5

[David Miller]

From: "Jason A. Donenfeld" <Jason@zx2c4.com>
Date: Sat,  7 Jan 2017 15:40:56 +0100

> This gives a clear speed and security improvement. Siphash is both
> faster and is more solid crypto than the aging MD5.
> 
> Rather than manually filling MD5 buffers, for IPv6, we simply create
> a layout by a simple anonymous struct, for which gcc generates
> rather efficient code. For IPv4, we pass the values directly to the
> short input convenience functions.
> 
> 64-bit x86_64:
> [    1.683628] secure_tcpv6_sequence_number_md5# cycles: 99563527
> [    1.717350] secure_tcp_sequence_number_md5# cycles: 92890502
> [    1.741968] secure_tcpv6_sequence_number_siphash# cycles: 67825362
> [    1.762048] secure_tcp_sequence_number_siphash# cycles: 67485526
> 
> 32-bit x86:
> [    1.600012] secure_tcpv6_sequence_number_md5# cycles: 103227892
> [    1.634219] secure_tcp_sequence_number_md5# cycles: 94732544
> [    1.669102] secure_tcpv6_sequence_number_siphash# cycles: 96299384
> [    1.700165] secure_tcp_sequence_number_siphash# cycles: 86015473
> 
> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

This and the next patch are a real shame, performance wise, on cpus
that have single-instruction SHA1 and MD5 implementations.  Sparc64
has both, and I believe x86_64 can do SHA1 these days.

It took so long to get those instructions into real silicon, and then
have software implemented to make use of them as well.

Who knows when we'll see SipHash widely deployed in any instruction
set, if at all, right?  And by that time we'll possibly find out that
"Oh shit, this SipHash thing has flaws!" and we'll need
DIPPY_DO_DA_HASH and thus be forced back to a software implementation
again.

I understand the reasons why these patches are being proposed, I just
thought I'd mention the issue of cpus that implement secure hash
algorithm instructions.

Re: [PATCH v2 net-next 3/4] secure_seq: use SipHash in place of MD5

[Eric Biggers]

Hi David,

On Sat, Jan 07, 2017 at 04:37:36PM -0500, David Miller wrote:
> From: "Jason A. Donenfeld" <Jason@zx2c4.com>
> Date: Sat,  7 Jan 2017 15:40:56 +0100
> 
> > This gives a clear speed and security improvement. Siphash is both
> > faster and is more solid crypto than the aging MD5.
[snip]
> 
> This and the next patch are a real shame, performance wise, on cpus
> that have single-instruction SHA1 and MD5 implementations.  Sparc64
> has both, and I believe x86_64 can do SHA1 these days.
> 
> It took so long to get those instructions into real silicon, and then
> have software implemented to make use of them as well.
> 
> Who knows when we'll see SipHash widely deployed in any instruction
> set, if at all, right?  And by that time we'll possibly find out that
> "Oh shit, this SipHash thing has flaws!" and we'll need
> DIPPY_DO_DA_HASH and thus be forced back to a software implementation
> again.
> 
> I understand the reasons why these patches are being proposed, I just
> thought I'd mention the issue of cpus that implement secure hash
> algorithm instructions.

Well, except those instructions aren't actually used in these places.  Although
x86_64 SHA1-NI accelerated SHA-1 is available in the Linux crypto API, it seems
that in kernel code it remains impractical to use these instructions on small
amounts of data because they use XMM registers, which means the overhead of
kernel_fpu_begin()/kernel_fpu_end() must be incurred.  Furthermore,
kernel_fpu_begin() is not allowed in all contexts so there has to be a fallback.

Out of curiosity, is this actually a solvable problem, e.g. by making the code
using the XMM registers responsible for saving and restoring the ones clobbered,
or by optimizing kernel_fpu_begin()/kernel_fpu_end()?  Or does it in fact remain
impractical for such instructions to be used for applications like this one?

Eric

Re: [PATCH v2 net-next 3/4] secure_seq: use SipHash in place of MD5

[David Miller]

From: Eric Biggers <ebiggers3@gmail.com>
Date: Sat, 7 Jan 2017 14:09:11 -0800

> Well, except those instructions aren't actually used in these
> places.  Although x86_64 SHA1-NI accelerated SHA-1 is available in
> the Linux crypto API, it seems that in kernel code it remains
> impractical to use these instructions on small amounts of data
> because they use XMM registers, which means the overhead of
> kernel_fpu_begin()/kernel_fpu_end() must be incurred.  Furthermore,
> kernel_fpu_begin() is not allowed in all contexts so there has to be
> a fallback.
> 
> Out of curiosity, is this actually a solvable problem, e.g. by
> making the code using the XMM registers responsible for saving and
> restoring the ones clobbered, or by optimizing
> kernel_fpu_begin()/kernel_fpu_end()?  Or does it in fact remain
> impractical for such instructions to be used for applications like
> this one?

On x86 making the FPU save more tractible in situations like this is
really hard and will make the code significantly more complex.

It's simpler and cheaper on sparc64, and unlike on x86 there aren't
any fundament restrictions on where FPU stuff can be used.  This is
because we don't have "save all the FPU state" instructions and have
to do it all by hand anyways.

However I will note that just like x86, sparc64 doesn't override the
md5_transform() in lib/md5.c like it should.

Re: [PATCH v2 net-next 3/4] secure_seq: use SipHash in place of MD5

[Jason A. Donenfeld]

Hi David,

On Sat, Jan 7, 2017 at 10:37 PM, David Miller <davem@davemloft.net> wrote:
> This and the next patch are a real shame, performance wise, on cpus
> that have single-instruction SHA1 and MD5 implementations.  Sparc64
> has both, and I believe x86_64 can do SHA1 these days.
>
> It took so long to get those instructions into real silicon, and then
> have software implemented to make use of them as well.

Actually, from a performance perspective, these patches are strictly
better than what was already there, since nothing actually used the
special instructions. They're also better security wise, because the
prior use of these functions was quite dubious. On x86, using the FPU
isn't really an option in these situations, as you well know. On
Sparc64, sure, I guess it's a bummer that silicon is lagging
cryptography. If after merging these improvements, you want to start
thinking about a special construction just for Sparc64 that would be
faster and have a matching security level, this would of course be
great. But so far, nobody even bothered to do this for the old
insecure slow code that this is replacing.

> Who knows when we'll see SipHash widely deployed in any instruction
> set, if at all, right?  And by that time we'll possibly find out that
> "Oh shit, this SipHash thing has flaws!" and we'll need
> DIPPY_DO_DA_HASH and thus be forced back to a software implementation
> again.

The literature and cryptanalyses on SipHash have been quite positive.
And as I mentioned earlier in patchset messages, SipHash is really
_not_ some newfangled hipster thing, but rather something that's been
around a while, pretty extensively studied, and considered quite
venerable. I think if you're going to bet on something SipHash is one
of the more safe bets to be made.

> I understand the reasons why these patches are being proposed, I just
> thought I'd mention the issue of cpus that implement secure hash
> algorithm instructions.

Yea, agreed, it's a bummer. Hopefully silicon will catch up someday,
and we'll all be happy. In the meantime, at least these patches
improve the situation on Linux.

I interpret your letter's omission of any substantive comments on the
code itself to be an indication that things are mostly sane. I'll
follow up with Eric's suggestions to produce a v3, and then hopefully
we can get this merged.

Regards,
Jason

Re: [PATCH v2 net-next 0/4] Introduce The SipHash PRF

[Jason A. Donenfeld]

Hi Eric,

Thanks for round two. I'll address these. Comments are inline below.

On Sat, Jan 7, 2017 at 8:54 PM, Eric Biggers <ebiggers3@gmail.com> wrote:
> Hi Jason, thanks for doing this!  Yes, I had gotten a little lost in the earlier
> discussions about the 'random' driver and other potential users of SipHash.  I
> agree with the approach to just introduce the two uses in net/ to start with,
> and introduce more users later.  The changes from v1 to v2 look good too.

Indeed the initial patchset was _insane_ and the discussion became
sprawling and impossible. Everybody suggested I do baby steps, so
voila, there's this more manageable patchset now.

> Now that the HalfSipHash patch is Cc'ed to me too I do have one other small
> suggestion which is that this:
>
>         #if BITS_PER_LONG == 64
>         typedef siphash_key_t hsiphash_key_t;
>         #define HSIPHASH_ALIGNMENT SIPHASH_ALIGNMENT
>         #else
>         typedef struct {
>                 u32 key[2];
>         } hsiphash_key_t;
>         #define HSIPHASH_ALIGNMENT __alignof__(u32)
>         #endif
>
> could cause confusion if someone accidentally uses 'siphash_key_t' instead of
> 'hsiphash_key_t', as their code would compile fine on a 64-bit platform but
> would fail to compile on a 32-bit platform.  I think there should just always be
> a hsiphash_key_t struct defined, and it can use unsigned long (no need for an
> #ifdef):
>
>         #define HSIPHASH_ALIGNMENT __alignof__(unsigned long)
>         typedef struct {
>                 unsigned long key[2];
>         } hsiphash_key_t;

Good idea. Will adjust. That makes things a lot simpler.

> There's also a small error in Documentation/siphash.txt: hsiphash() is shown as
> taking siphash_key_t instead of hsiphash_key_t.

Arg, nice catch, fixing.

> The uses in net look good too.  Something to watch out for is accidentally
> defining the structs in a way that leaves internal padding bytes, which could
> theoretically take on any value and cause the same input to produce different
> hashes.  But AFAICS, in the proposed patch all the structs are laid out
> properly, so that won't happen.

Indeed that's something closely examined. In fact, originally, just to
be careful, I was using __packed, but David pointed out that using
__packed makes gcc resort to byte-by-byte assignment, even if the
alignment would otherwise be natural. So, instead I just made sure to
list the members in descending order of size, and made sure to use
offsetendof instead of sizeof. I'll be sure to document this
precaution in the Documentation/siphash.txt file for the next version,
alongside a simple example.

> 'net_secret' could also be marked as __read_mostly, like the keys in
> syncookies.c, I suppose; it may not matter much.

Good point. Fixing.

New version coming your way soon.

Thanks again,
Jason

RE: [PATCH v2 net-next 3/4] secure_seq: use SipHash in place of MD5

[David Laight]

From: Eric Biggers
> Sent: 07 January 2017 22:09
..
> Out of curiosity, is this actually a solvable problem, e.g. by making the code
> using the XMM registers responsible for saving and restoring the ones clobbered,
> or by optimizing kernel_fpu_begin()/kernel_fpu_end()?  Or does it in fact remain
> impractical for such instructions to be used for applications like this one?

I think it should be possible to fast-save a couple of FP registers
by telling the IPI save code where to save them from (to load
into a different cpu).
But there might be issues with other parts of the FP state.
This might be ok provided the kernel doesn't actually use FP instructions.

(I thought about this when adding AVX support to NetBSD.)

	David