The hash table implementation uses `& (h->size - 1)` to truncate
generated hashes to the number of buckets. This operation is equal to
`% h->size` if and only if the size is a power of two (which seems to be
always the case). One property of the binary and with a power of two
(and probably a small one <=2048) is all higher bits are discarded.
Thus a hash function is needed with a good avalanche effect, which the
current one is not.
Signed-off-by: Christian Göttsche <cgzones@xxxxxxxxxxxxxx>
---
policycoreutils/newrole/newrole.c | 17 +++++++----------
1 file changed, 7 insertions(+), 10 deletions(-)
diff --git a/policycoreutils/newrole/newrole.c b/policycoreutils/newrole/newrole.c
index d9efa68a..5a1a1129 100644
--- a/policycoreutils/newrole/newrole.c
+++ b/policycoreutils/newrole/newrole.c
@@ -229,16 +229,13 @@ static int free_hashtab_entry(hashtab_key_t key, hashtab_datum_t d,
static unsigned int reqsymhash(hashtab_t h, const_hashtab_key_t key)
{
- const char *p;
- size_t size;
- unsigned int val;
-
- val = 0;
- size = strlen(key);
- for (p = key; ((size_t) (p - key)) < size; p++)
- val =
- (val << 4 | (val >> (8 * sizeof(unsigned int) - 4))) ^ (*p);
- return val & (h->size - 1);
+ unsigned int hash = 5381;
+ unsigned char c;
+
+ while ((c = *(unsigned const char *)key++))
+ hash = ((hash << 5) + hash) ^ c;
+
+ return hash & (h->size - 1);
}
static int reqsymcmp(hashtab_t h
--
2.40.1
