Use the crypto random functions instead of `rand()`.

Presumably the uses of `rand()` were fine because they were not used in
security-sensitive places, but having to think about whether a crappy RNG
is acceptable in each situation requires effort that could better be
spent elsewhere.

Also, this means that once we have a custom deterministic RNG for
testing, that RNG is used everywhere, so all the code is deterministic.

It also allowed us to delete a system-specific function that wasn't used
anywhere except in a call to `srand()`.

1 files changed, 7 insertions, 6 deletions

diff --git a/toxcore/TCP_connection.c b/toxcore/TCP_connection.c
index 2d2dd470..6763328d 100644
--- a/toxcore/TCP_connection.c
+++ b/toxcore/TCP_connection.c
@@ -371,10 +371,10 @@ int send_packet_tcp_connection(TCP_Connections *tcp_c, int connections_number, c
  */
 int get_random_tcp_onion_conn_number(TCP_Connections *tcp_c)
 {
-    unsigned int i, r = rand();
+    const uint32_t r = random_u32();
 
-    for (i = 0; i < tcp_c->tcp_connections_length; ++i) {
-        unsigned int index = ((i + r) % tcp_c->tcp_connections_length);
+    for (uint32_t i = 0; i < tcp_c->tcp_connections_length; ++i) {
+        uint32_t index = ((i + r) % tcp_c->tcp_connections_length);
 
         if (tcp_c->tcp_connections[index].onion && tcp_c->tcp_connections[index].status == TCP_CONN_CONNECTED) {
             return index;
@@ -1283,11 +1283,12 @@ unsigned int tcp_connection_to_online_tcp_relays(TCP_Connections *tcp_c, int con
  * return number of relays copied to tcp_relays on success.
  * return 0 on failure.
  */
-unsigned int tcp_copy_connected_relays(TCP_Connections *tcp_c, Node_format *tcp_relays, uint16_t max_num)
+uint32_t tcp_copy_connected_relays(TCP_Connections *tcp_c, Node_format *tcp_relays, uint16_t max_num)
 {
-    unsigned int i, copied = 0, r = rand();
+    const uint32_t r = random_u32();
+    uint32_t copied = 0;
 
-    for (i = 0; (i < tcp_c->tcp_connections_length) && (copied < max_num); ++i) {
+    for (uint32_t i = 0; (i < tcp_c->tcp_connections_length) && (copied < max_num); ++i) {
         TCP_con *tcp_con = get_tcp_connection(tcp_c, (i + r) % tcp_c->tcp_connections_length);
 
         if (!tcp_con) {