Replace chunk_hash() with output from chunk_mac()

The quality is way better, the calculation is a bit slower though.

The key is statically initialized to zero, which will be changed later
to prevent hash flooding.

diff --git a/src/libstrongswan/utils/chunk.c b/src/libstrongswan/utils/chunk.c
index ca277da..9033cbd 100644 (file)
--- a/src/libstrongswan/utils/chunk.c
+++ b/src/libstrongswan/utils/chunk.c
@@ -24,16 +24,6 @@
 #include "chunk.h"
 #include "debug.h"
 
-/* required for chunk_hash */
-#undef get16bits
-#if (defined(__GNUC__) && defined(__i386__))
-#define get16bits(d) (*((const u_int16_t*)(d)))
-#endif
-#if !defined (get16bits)
-#define get16bits(d) ((((u_int32_t)(((const u_int8_t*)(d))[1])) << 8)\
-                      + (u_int32_t)(((const u_int8_t*)(d))[0]) )
-#endif
-
 /**
  * Empty chunk.
  */
@@ -659,11 +649,11 @@ static inline u_int64_t siplast(size_t len, u_char *pos)
 }
 
 /**
- * Described in header.
+ * Caculate SipHash-2-4 with an optional first block given as argument.
  */
-u_int64_t chunk_mac(chunk_t chunk, u_char *key)
+static u_int64_t chunk_mac_inc(chunk_t chunk, u_char *key, u_int64_t m)
 {
-       u_int64_t v0, v1, v2, v3, k0, k1, m;
+       u_int64_t v0, v1, v2, v3, k0, k1;
        size_t len = chunk.len;
        u_char *pos = chunk.ptr, *end;
 
@@ -677,6 +667,11 @@ u_int64_t chunk_mac(chunk_t chunk, u_char *key)
        v2 = k0 ^ 0x6c7967656e657261ULL;
        v3 = k1 ^ 0x7465646279746573ULL;
 
+       if (m)
+       {
+               sipcompress(&v0, &v1, &v2, &v3, m);
+       }
+
        /* compression with c = 2 */
        for (; pos != end; pos += 8)
        {
@@ -696,71 +691,24 @@ u_int64_t chunk_mac(chunk_t chunk, u_char *key)
 
 /**
  * Described in header.
- *
- * The implementation is based on Paul Hsieh's SuperFastHash:
- *      http://www.azillionmonkeys.com/qed/hash.html
  */
-u_int32_t chunk_hash_inc(chunk_t chunk, u_int32_t hash)
+u_int64_t chunk_mac(chunk_t chunk, u_char *key)
 {
-       u_char *data = chunk.ptr;
-       size_t len = chunk.len;
-       u_int32_t tmp;
-       int rem;
-
-       if (!len || data == NULL)
-       {
-               return 0;
-       }
-
-       rem = len & 3;
-       len >>= 2;
-
-       /* Main loop */
-       for (; len > 0; --len)
-       {
-               hash += get16bits(data);
-               tmp   = (get16bits(data + 2) << 11) ^ hash;
-               hash  = (hash << 16) ^ tmp;
-               data += 2 * sizeof(u_int16_t);
-               hash += hash >> 11;
-       }
-
-       /* Handle end cases */
-       switch (rem)
-       {
-               case 3:
-               {
-                       hash += get16bits(data);
-                       hash ^= hash << 16;
-                       hash ^= data[sizeof(u_int16_t)] << 18;
-                       hash += hash >> 11;
-                       break;
-               }
-               case 2:
-               {
-                       hash += get16bits(data);
-                       hash ^= hash << 11;
-                       hash += hash >> 17;
-                       break;
-               }
-               case 1:
-               {
-                       hash += *data;
-                       hash ^= hash << 10;
-                       hash += hash >> 1;
-                       break;
-               }
-       }
+       return chunk_mac_inc(chunk, key, 0);
+}
 
-       /* Force "avalanching" of final 127 bits */
-       hash ^= hash << 3;
-       hash += hash >> 5;
-       hash ^= hash << 4;
-       hash += hash >> 17;
-       hash ^= hash << 25;
-       hash += hash >> 6;
+/**
+ * Key used for chunk_hash.
+ */
+static u_char key[16];
 
-       return hash;
+/**
+ * Described in header.
+ */
+u_int32_t chunk_hash_inc(chunk_t chunk, u_int32_t hash)
+{
+       /* we could use a mac of the previous hash, but this is faster */
+       return chunk_mac_inc(chunk, key, ((u_int64_t)hash) << 32 | hash);
 }
 
 /**
@@ -768,7 +716,7 @@ u_int32_t chunk_hash_inc(chunk_t chunk, u_int32_t hash)
  */
 u_int32_t chunk_hash(chunk_t chunk)
 {
-       return chunk_hash_inc(chunk, chunk.len);
+       return chunk_mac(chunk, key);
 }
 
 /**

diff --git a/src/libstrongswan/utils/chunk.h b/src/libstrongswan/utils/chunk.h
index b28ff12..cfda6ee 100644 (file)
--- a/src/libstrongswan/utils/chunk.h
+++ b/src/libstrongswan/utils/chunk.h
@@ -301,12 +301,20 @@ bool chunk_printable(chunk_t chunk, chunk_t *sane, char replace);
 
 /**
  * Computes a 32 bit hash of the given chunk.
+ *
  * @note This hash is only intended for hash tables not for cryptographic purposes.
+ *
+ * @param chunk                        data to hash
+ * @return                             hash value
  */
 u_int32_t chunk_hash(chunk_t chunk);
 
 /**
  * Incremental version of chunk_hash. Use this to hash two or more chunks.
+ *
+ * @param chunk                        data to hash
+ * @param hash                 previous hash value
+ * @return                             hash value
  */
 u_int32_t chunk_hash_inc(chunk_t chunk, u_int32_t hash);