1 files changed, 107 insertions, 0 deletions
diff --git a/src/util/hash_fnv.c b/src/util/hash_fnv.c
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+/*++
+/* NAME
+/*	hash_fnv 3
+/* SUMMARY
+/*	Fowler/Noll/Vo hash function
+/* SYNOPSIS
+/*	#include <hash_fnv.h>
+/*
+/*	HASH_FNV_T hash_fnv(
+/*	const void *src,
+/*	size_t	len)
+/* DESCRIPTION
+/*	hash_fnv() implements a modified FNV type 1a hash function.
+/*
+/*	To thwart collision attacks, the hash function is seeded
+/*	once from /dev/urandom, and if that is unavailable, from
+/*	wallclock time, monotonic system clocks, and the process
+/*	ID. To disable seeding (typically, for regression tests),
+/*	specify the NORANDOMIZE environment variable; the value
+/*	does not matter.
+/*
+/*	This function implements a workaround for a "sticky state"
+/*	problem with FNV hash functions: when an input produces a
+/*	zero intermediate hash state, and the next input byte is
+/*	zero, then the operations "hash ^= 0" and "hash *= FNV_prime"
+/*	would not change the hash value. To avoid this, hash_fnv()
+/*	adds 1 to each input byte. Compile with -DSTRICT_FNV1A to
+/*	get the standard behavior.
+/*
+/*	The default HASH_FNV_T result type is uint64_t. When compiled
+/*	with -DUSE_FNV_32BIT, the result type is uint32_t. On ancient
+/*	systems without <stdint.h>, define HASH_FNV_T on the compiler
+/*	command line as an unsigned 32-bit or 64-bit integer type,
+/*	and specify -DUSE_FNV_32BIT when HASH_FNV_T is a 32-bit type.
+/* SEE ALSO
+/*	http://www.isthe.com/chongo/tech/comp/fnv/index.html
+/*	https://softwareengineering.stackexchange.com/questions/49550/
+/* LICENSE
+/* .ad
+/* .fi
+/*	The Secure Mailer license must be distributed with this software.
+/* AUTHOR(S)
+/*	Wietse Venema
+/*	Google, Inc.
+/*	111 8th Avenue
+/*	New York, NY 10011, USA
+/*--*/
+
+ /*
+  * System library
+  */
+#include <sys_defs.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+ /*
+  * Utility library.
+  */
+#include <msg.h>
+#include <ldseed.h>
+#include <hash_fnv.h>
+
+ /*
+  * Application-specific.
+  */
+#ifdef USE_FNV_32BIT
+#define FNV_prime 		0x01000193UL
+#define FNV_offset_basis	0x811c9dc5UL
+#else
+#define FNV_prime		0x00000100000001B3ULL
+#define FNV_offset_basis	0xcbf29ce484222325ULL
+#endif
+
+/* hash_fnv - modified FNV 1a hash */
+
+HASH_FNV_T hash_fnv(const void *src, size_t len)
+{
+    static HASH_FNV_T basis = FNV_offset_basis;
+    static int randomize = 1;
+    HASH_FNV_T hash;
+
+    /*
+     * Initialize.
+     */
+    if (randomize) {
+	if (!getenv("NORANDOMIZE")) {
+	    HASH_FNV_T seed;
+
+	    ldseed(&seed, sizeof(seed));
+	    basis ^= seed;
+	}
+	randomize = 0;
+    }
+
+#ifdef STRICT_FNV1A
+#define FNV_NEXT_BYTE(s) ((HASH_FNV_T) * (const unsigned char *) s++)
+#else
+#define FNV_NEXT_BYTE(s) (1 + (HASH_FNV_T) * (const unsigned char *) s++)
+#endif
+
+    hash = basis;
+    while (len-- > 0) {
+	hash ^= FNV_NEXT_BYTE(src);
+	hash *= FNV_prime;
+    }
+    return (hash);
+}