Rely on /dev/urandom

This removes quite a bit of code. All reasonable systems have /dev/urandom
these days. Linux, Solaris and the BSDs do.  In case we find a system
without /dev/urandom, we will have to go hunting in other libraries.

The main reason for this is speed: On Ubuntu 14.04 doing direct reads from
/dev/urandom is 2-3 times faster than our md4 based code. On virtualized
FreeBSD 10 the difference is even larger.

My first approach was to use fopen/fread. It was even faster, but less
than twice as fast. So I thought we could save the additional complexity
when having to deal with throwing away buffers when forking and the
additional memory footprint per process.

With this simple generate_random_buffer it will be easier to adapt new
syscalls to get randomness.

Signed-off-by: Volker Lendecke <vl@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>

Autobuild-User(master): Jeremy Allison <jra@samba.org>
Autobuild-Date(master): Tue Oct 13 04:25:39 CEST 2015 on sn-devel-104

4 files changed, 0 insertions, 73 deletions

diff --git a/source4/param/secrets.c b/source4/param/secrets.c
index 92e338a6bab..987408829ea 100644
--- a/source4/param/secrets.c
+++ b/source4/param/secrets.c
@@ -33,59 +33,6 @@
 #include "dsdb/samdb/samdb.h"
 
 /**
- * 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(struct tdb_wrap *secretsdb, int *new_seed) 
-{
-	*new_seed = getpid();
-	if (secretsdb != NULL) {
-		tdb_change_int32_atomic(secretsdb->tdb, "INFO/random_seed", new_seed, 1);
-	}
-}
-
-/**
- * open up the randseed database and set the random number generator callback
- */
-bool randseed_init(TALLOC_CTX *mem_ctx, struct loadparm_context *lp_ctx)
-{
-	char *fname;
-	uint8_t dummy;
-	struct tdb_wrap *tdb;
-
-	fname = lpcfg_private_path(mem_ctx, lp_ctx, "randseed.tdb");
-
-	tdb = tdb_wrap_open(mem_ctx, fname,
-			    lpcfg_tdb_hash_size(lp_ctx, fname),
-			    lpcfg_tdb_flags(lp_ctx, TDB_DEFAULT),
-			    O_RDWR|O_CREAT, 0600);
-
-	if (!tdb) {
-		DEBUG(0,("Failed to open %s\n", fname));
-		talloc_free(fname);
-		return false;
-	}
-	talloc_free(fname);
-
-	/**
-	 * 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((void (*) (void *, int *))get_rand_seed, tdb);
-
-	/* Ensure that the reseed is done now, while we are root, etc */
-	generate_random_buffer(&dummy, sizeof(dummy));
-
-	return true;
-}
-
-/**
   connect to the secrets ldb
 */
 struct ldb_context *secrets_db_connect(TALLOC_CTX *mem_ctx,
diff --git a/source4/param/secrets.h b/source4/param/secrets.h
index 1e7849f9788..015ea120041 100644
--- a/source4/param/secrets.h
+++ b/source4/param/secrets.h
@@ -28,14 +28,6 @@
 #define SECRETS_PRINCIPAL_SEARCH "(&(|(realm=%s)(flatname=%s))(servicePrincipalName=%s))"
 #define SECRETS_LDAP_FILTER "(&(objectclass=ldapSecret)(cn=SAMDB Credentials))"
 
-/**
- * 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.
- */
 struct loadparm_context;
 struct tevent_context;
 struct ldb_message;
diff --git a/source4/smbd/process_standard.c b/source4/smbd/process_standard.c
index b55a1a7f309..d223776d0e9 100644
--- a/source4/smbd/process_standard.c
+++ b/source4/smbd/process_standard.c
@@ -277,9 +277,6 @@ static void standard_accept_connection(struct tevent_context *ev,
 		child_pipe[1] = -1;
 	}
 
-	/* Ensure that the forked children do not expose identical random streams */
-	set_need_random_reseed();
-
 	/* setup the process title */
 	c = socket_get_peer_addr(sock2, ev);
 	s = socket_get_my_addr(sock2, ev);
@@ -356,9 +353,6 @@ static void standard_new_task(struct tevent_context *ev,
 		child_pipe[1] = -1;
 	}
 
-	/* Ensure that the forked children do not expose identical random streams */
-	set_need_random_reseed();
-
 	setproctitle("task %s server_id[%d]", service_name, (int)pid);
 
 	/* setup this new task.  Cluster ID is PID based for this process model */
diff --git a/source4/smbd/server.c b/source4/smbd/server.c
index b0f67c97f07..cb1a20b4ecc 100644
--- a/source4/smbd/server.c
+++ b/source4/smbd/server.c
@@ -392,12 +392,6 @@ static int binary_smbd_main(const char *binary_name, int argc, const char *argv[
 
 	pidfile_create(lpcfg_pid_directory(cmdline_lp_ctx), binary_name);
 
-	/* Set up a database to hold a random seed, in case we don't
-	 * have /dev/urandom */
-	if (!randseed_init(talloc_autofree_context(), cmdline_lp_ctx)) {
-		return 1;
-	}
-
 	if (lpcfg_server_role(cmdline_lp_ctx) == ROLE_ACTIVE_DIRECTORY_DC) {
 		if (!open_schannel_session_store(talloc_autofree_context(), cmdline_lp_ctx)) {
 			exit_daemon("Samba cannot open schannel store for secured NETLOGON operations.", EACCES);