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 hsiphash_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.
* 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
return ___siphash_aligned(data, len, key);
}
+#define HSIPHASH_ALIGNMENT __alignof__(unsigned long)
+typedef struct {
+ unsigned long key[2];
+} hsiphash_key_t;
+
+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 */
* 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>
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
* 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
#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 =
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);
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]) {
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;
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