From: Vladimír Čunát <vladimir.cunat@nic.cz>
Date: Thu, 3 Aug 2017 12:59:48 +0000 (+0200)
Subject: kr_rand_uint: nitpicks
X-Git-Tag: v1.3.3~4^2
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=c2dbf7200727beb56ce3d1b250babb6c49781109;p=thirdparty%2Fknot-resolver.git

kr_rand_uint: nitpicks

- the returned value is up to max-1 and not max (tiny bias)
- improve efficiency slightly
- unsigned -> uint32_t, as that's the range it supports (mostly equal)
---

diff --git a/daemon/lua/kres-gen.lua b/daemon/lua/kres-gen.lua
index 9d35ef8fc..fbe4208d9 100644
--- a/daemon/lua/kres-gen.lua
+++ b/daemon/lua/kres-gen.lua
@@ -193,7 +193,7 @@ struct kr_query *kr_rplan_push(struct kr_rplan *, struct kr_query *, const knot_
 int kr_rplan_pop(struct kr_rplan *, struct kr_query *);
 struct kr_query *kr_rplan_resolved(struct kr_rplan *);
 int kr_nsrep_set(struct kr_query *, size_t, const struct sockaddr *);
-unsigned int kr_rand_uint(unsigned int);
+uint32_t kr_rand_uint(uint32_t);
 void kr_pkt_make_auth_header(knot_pkt_t *);
 int kr_pkt_put(knot_pkt_t *, const knot_dname_t *, uint32_t, uint16_t, uint16_t, const uint8_t *, uint16_t);
 int kr_pkt_recycle(knot_pkt_t *);
diff --git a/lib/layer/iterate.c b/lib/layer/iterate.c
index 0efccbb74..5c1017b81 100644
--- a/lib/layer/iterate.c
+++ b/lib/layer/iterate.c
@@ -823,7 +823,8 @@ int kr_make_query(struct kr_query *query, knot_pkt_t *pkt)
 	}
 
 	/* Query built, expect answer. */
-	query->id = kr_rand_uint(UINT16_MAX);
+	uint32_t rnd = kr_rand_uint(0);
+	query->id = rnd ^ (rnd >> 16); /* cheap way to strengthen unpredictability */
 	knot_wire_set_id(pkt->wire, query->id);
 	pkt->parsed = pkt->size;
 	WITH_VERBOSE {
diff --git a/lib/resolve.c b/lib/resolve.c
index c8701768d..2fdd47071 100644
--- a/lib/resolve.c
+++ b/lib/resolve.c
@@ -1413,7 +1413,7 @@ ns_election:
 
 	/* Randomize query case (if not in safemode or turned off) */
 	qry->secret = (qry->flags & (QUERY_SAFEMODE | QUERY_NO_0X20))
-			? 0 : kr_rand_uint(UINT32_MAX);
+			? 0 : kr_rand_uint(0);
 	knot_dname_t *qname_raw = (knot_dname_t *)knot_pkt_qname(packet);
 	randomized_qname_case(qname_raw, qry->secret);
 
diff --git a/lib/utils.c b/lib/utils.c
index bc177a92c..ab0189c1f 100644
--- a/lib/utils.c
+++ b/lib/utils.c
@@ -168,13 +168,15 @@ int kr_rand_reseed(void)
 	return kr_ok();
 }
 
-unsigned kr_rand_uint(unsigned max)
+uint32_t kr_rand_uint(uint32_t max)
 {
-	if (!isaac_seeded) {
+	if (unlikely(!isaac_seeded)) {
 		kr_rand_reseed();
 		isaac_seeded = true;
 	}
-	return isaac_next_uint(&ISAAC, max);
+	return max == 0
+		? isaac_next_uint32(&ISAAC)
+		: isaac_next_uint(&ISAAC, max);
 }
 
 int kr_memreserve(void *baton, char **mem, size_t elm_size, size_t want, size_t *have)
diff --git a/lib/utils.h b/lib/utils.h
index 3cbf989bd..3d6945ba3 100644
--- a/lib/utils.h
+++ b/lib/utils.h
@@ -149,9 +149,12 @@ char* kr_strcatdup(unsigned n, ...);
 /** Reseed CSPRNG context. */
 int kr_rand_reseed(void);
 
-/** Get pseudo-random value. */
+/** Get pseudo-random value between zero and max-1 (inclusive).
+ *
+ * Passing zero means that any uint32_t should be returned (it's also faster).
+ */
 KR_EXPORT
-unsigned kr_rand_uint(unsigned max);
+uint32_t kr_rand_uint(uint32_t max);
 
 /** Memory reservation routine for knot_mm_t */
 KR_EXPORT
diff --git a/modules/cookies/cookiemonster.c b/modules/cookies/cookiemonster.c
index 13f548959..bd838b7e8 100644
--- a/modules/cookies/cookiemonster.c
+++ b/modules/cookies/cookiemonster.c
@@ -414,7 +414,7 @@ int check_request(kr_layer_t *ctx)
 	};
 
 	struct kr_nonce_input nonce = {
-		.rand = kr_rand_uint(UINT32_MAX),
+		.rand = kr_rand_uint(0),
 		.time = req->current_query->timestamp.tv_sec
 	};