diff options
Diffstat (limited to 'shared/nm-glib-aux/nm-hash-utils.c')
| -rw-r--r-- | shared/nm-glib-aux/nm-hash-utils.c | 112 |
1 files changed, 69 insertions, 43 deletions
diff --git a/shared/nm-glib-aux/nm-hash-utils.c b/shared/nm-glib-aux/nm-hash-utils.c index cd51bbaf..0a701d06 100644 --- a/shared/nm-glib-aux/nm-hash-utils.c +++ b/shared/nm-glib-aux/nm-hash-utils.c @@ -24,7 +24,6 @@ static const guint8 *volatile global_seed = NULL; static const guint8 * _get_hash_key_init (void) { - static gsize g_lock; /* the returned hash is aligned to guin64, hence, it is safe * to use it as guint* or guint64* pointer. */ static union { @@ -34,50 +33,49 @@ _get_hash_key_init (void) guint64 _align_as_uint64; } g_arr; const guint8 *g; - union { - guint8 v8[HASH_KEY_SIZE]; - guint vuint; - } t_arr; again: g = g_atomic_pointer_get (&global_seed); - if (G_LIKELY (g != NULL)) { - nm_assert (g == g_arr.v8); - return g; - } - - { - CSipHash siph_state; + if (!G_UNLIKELY (g)) { + static gsize g_lock; uint64_t h; - - /* initialize a random key in t_arr. */ + union { + guint vuint; + guint8 v8[HASH_KEY_SIZE]; + guint8 _extra_entropy[3 * HASH_KEY_SIZE]; + } t_arr; nm_utils_random_bytes (&t_arr, sizeof (t_arr)); - /* use siphash() of the key-size, to mangle the first guint. Otherwise, - * the first guint has only the entropy that nm_utils_random_bytes() - * generated for the first 4 bytes and relies on a good random generator. + /* We only initialize one random hash key. So we can spend some effort + * of getting this right. For one, we collect more random bytes than + * necessary. * - * The first int is especially interesting for nm_hash_static() below, and we - * want to have it all the entropy of t_arr. */ - c_siphash_init (&siph_state, t_arr.v8); - c_siphash_append (&siph_state, (const guint8 *) &t_arr, sizeof (t_arr)); - h = c_siphash_finalize (&siph_state); - if (sizeof (guint) < sizeof (h)) - t_arr.vuint = t_arr.vuint ^ ((guint) (h & 0xFFFFFFFFu)) ^ ((guint) (h >> 32)); + * Then, the first guint of the seed should have all the entropy that we could + * obtain in sizeof(t_arr). For that, siphash(t_arr) and xor the first guint + * with hash. + * The first guint is especially interesting for nm_hash_static() below that + * doesn't use siphash itself. */ + h = c_siphash_hash (t_arr.v8, + (const guint8 *) &t_arr, + sizeof (t_arr)); + if (sizeof (h) > sizeof (guint)) + t_arr.vuint = t_arr.vuint ^ ((guint) (h & G_MAXUINT)) ^ ((guint) (h >> 32)); else - t_arr.vuint = t_arr.vuint ^ ((guint) (h & 0xFFFFFFFFu)); - } + t_arr.vuint = t_arr.vuint ^ ((guint) (h & G_MAXUINT)); - if (!g_once_init_enter (&g_lock)) { - /* lost a race. The random key is already initialized. */ - goto again; + if (!g_once_init_enter (&g_lock)) { + /* lost a race. The random key is already initialized. */ + goto again; + } + + memcpy (g_arr.v8, t_arr.v8, HASH_KEY_SIZE); + g = g_arr.v8; + g_atomic_pointer_set (&global_seed, g); + g_once_init_leave (&g_lock, 1); } - memcpy (g_arr.v8, t_arr.v8, HASH_KEY_SIZE); - g = g_arr.v8; - g_atomic_pointer_set (&global_seed, g); - g_once_init_leave (&g_lock, 1); + nm_assert (g == g_arr.v8); return g; } @@ -94,18 +92,24 @@ again: guint nm_hash_static (guint static_seed) { - /* note that we only xor the static_seed with the key. - * We don't use siphash, which would mix the bits better. - * Note that this doesn't matter, because static_seed is not - * supposed to be a value that you are hashing (for that, use - * full siphash). - * Instead, different callers may set a different static_seed - * so that nm_hash_str(NULL) != nm_hash_ptr(NULL). + /* Note that we only xor the static_seed with the first guint of the key. + * + * We don't use siphash, which would mix the bits better with _get_hash_key(). + * Note that nm_hash_static() isn't used to hash the static_seed. Instead, it + * is used to get a unique hash value in a static context. That means, every + * caller is responsible to choose a static_seed that is sufficiently + * distinct from all other callers. In other words, static_seed should be a + * unique constant with good entropy. + * + * Note that _get_hash_key_init() already xored the first guint of the + * key with the siphash of the entire static key. That means, even if + * we got bad randomness for the first guint, the first guint is also + * mixed with the randomness of the entire random key. * - * Also, ensure that we don't return zero. + * Also, ensure that we don't return zero (like for nm_hash_complete()). */ - return ((*((const guint *) _get_hash_key ())) ^ static_seed) - ?: static_seed ?: 3679500967u; + return ((*((const guint *) _get_hash_key ())) ^ static_seed) + ?: 3679500967u; } void @@ -257,3 +261,25 @@ nm_ppdirect_equal (gconstpointer a, gconstpointer b) return **s1 == **s2; } + +/*****************************************************************************/ + +guint +nm_pgbytes_hash (gconstpointer p) +{ + GBytes *const*ptr = p; + gconstpointer arr; + gsize len; + + arr = g_bytes_get_data (*ptr, &len); + return nm_hash_mem (1470631313u, arr, len); +} + +gboolean +nm_pgbytes_equal (gconstpointer a, gconstpointer b) +{ + GBytes *const*ptr_a = a; + GBytes *const*ptr_b = b; + + return g_bytes_equal (*ptr_a, *ptr_b); +} |