r1492: Rework our random number generation system.

On systems with /dev/urandom, this avoids a change to secrets.tdb for every fork().

For other systems, we now only re-seed after a fork, and on startup.
No need to do it per-operation.  This removes the 'need_reseed'
parameter from generate_random_buffer().

Andrew Bartlett
(This used to be commit 36741d3cf53a7bd17d361251f2bb50851cdb035f)

2 files changed, 30 insertions, 32 deletions

diff --git a/source3/passdb/machine_sid.c b/source3/passdb/machine_sid.c
index 47b9e2d487..ce1354ce81 100644
--- a/source3/passdb/machine_sid.c
+++ b/source3/passdb/machine_sid.c
@@ -67,7 +67,7 @@ static void generate_random_sid(DOM_SID *sid)
 	sid->num_auths = 0;
 	sid->sub_auths[sid->num_auths++] = 21;
 
-	generate_random_buffer(raw_sid_data, 12, True);
+	generate_random_buffer(raw_sid_data, 12);
 	for (i = 0; i < 3; i++)
 		sid->sub_auths[sid->num_auths++] = IVAL(raw_sid_data, i*4);
 }
diff --git a/source3/passdb/secrets.c b/source3/passdb/secrets.c
index 2b3175bed2..e7637f689d 100644
--- a/source3/passdb/secrets.c
+++ b/source3/passdb/secrets.c
@@ -30,10 +30,27 @@
 
 static TDB_CONTEXT *tdb;
 
+/**
+ * Use a TDB to store an incrementing random seed.
+ *
+ * Initialised to the current pid, the very first time Samba starts,
+ * and incremented by one each time it is needed.  
+ * 
+ * @note Not called by systems with a working /dev/urandom.
+ */
+static void get_rand_seed(int *new_seed) 
+{
+	*new_seed = sys_getpid();
+	if (tdb) {
+		tdb_change_int32_atomic(tdb, "INFO/random_seed", new_seed, 1);
+	}
+}
+
 /* open up the secrets database */
 BOOL secrets_init(void)
 {
 	pstring fname;
+	char dummy;
 
 	if (tdb)
 		return True;
@@ -47,6 +64,18 @@ BOOL secrets_init(void)
 		DEBUG(0,("Failed to open %s\n", fname));
 		return False;
 	}
+
+	/**
+	 * Set a reseed function for the crypto random generator 
+	 * 
+	 * This avoids a problem where systems without /dev/urandom
+	 * could send the same challenge to multiple clients
+	 */
+	set_rand_reseed_callback(get_rand_seed);
+
+	/* Ensure that the reseed is done now, while we are root, etc */
+	generate_random_buffer(&dummy, sizeof(dummy));
+
 	return True;
 }
 
@@ -504,37 +533,6 @@ BOOL trusted_domain_password_delete(const char *domain)
 }
 
 
-/*******************************************************************
- Reset the 'done' variables so after a client process is created
- from a fork call these calls will be re-done. This should be
- expanded if more variables need reseting.
- ******************************************************************/
-
-void reset_globals_after_fork(void)
-{
-	unsigned char dummy;
-
-	secrets_init();
-
-	/*
-	 * Increment the global seed value to ensure every smbd starts
-	 * with a new random seed.
-	 */
-
-	if (tdb) {
-		uint32 initial_val = sys_getpid();
-		tdb_change_int32_atomic(tdb, "INFO/random_seed", (int *)&initial_val, 1);
-		set_rand_reseed_data((unsigned char *)&initial_val, sizeof(initial_val));
-	}
-
-	/*
-	 * Re-seed the random crypto generator, so all smbd's
-	 * started from the same parent won't generate the same
-	 * sequence.
-	 */
-	generate_random_buffer( &dummy, 1, True);
-}
-
 BOOL secrets_store_ldap_pw(const char* dn, char* pw)
 {
 	char *key = NULL;