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()`.

8 files changed, 30 insertions, 56 deletions

diff --git a/toxcore/DHT.c b/toxcore/DHT.c
index 543ee191..37dd9385 100644
--- a/toxcore/DHT.c
+++ b/toxcore/DHT.c
@@ -1740,10 +1740,10 @@ static uint8_t do_ping_and_sendnode_requests(DHT *dht, uint64_t *lastgetnode, co
     }
 
     if ((num_nodes != 0) && (is_timeout(*lastgetnode, GET_NODE_INTERVAL) || *bootstrap_times < MAX_BOOTSTRAP_TIMES)) {
-        uint32_t rand_node = rand() % num_nodes;
+        uint32_t rand_node = random_u32() % num_nodes;
 
         if ((num_nodes - 1) != rand_node) {
-            rand_node += rand() % (num_nodes - (rand_node + 1));
+            rand_node += random_u32() % (num_nodes - (rand_node + 1));
         }
 
         getnodes(dht, assoc_list[rand_node]->ip_port, client_list[rand_node]->public_key, public_key, nullptr);
@@ -2050,7 +2050,7 @@ static int routeone_tofriend(DHT *dht, const uint8_t *friend_id, const uint8_t *
         return 0;
     }
 
-    const int retval = sendpacket(dht->net, ip_list[rand() % n], packet, length);
+    const int retval = sendpacket(dht->net, ip_list[random_u32() % n], packet, length);
 
     if ((unsigned int)retval == length) {
         return 1;
@@ -2492,7 +2492,7 @@ static Node_format random_node(DHT *dht, Family sa_family)
     uint8_t id[CRYPTO_PUBLIC_KEY_SIZE];
 
     for (uint32_t i = 0; i < CRYPTO_PUBLIC_KEY_SIZE / 4; ++i) { /* populate the id with pseudorandom bytes.*/
-        const uint32_t t = rand();
+        const uint32_t t = random_u32();
         memcpy(id + i * sizeof(t), &t, sizeof(t));
     }
 
@@ -2504,7 +2504,7 @@ static Node_format random_node(DHT *dht, Family sa_family)
         return nodes_list[0];
     }
 
-    return nodes_list[rand() % num_nodes];
+    return nodes_list[random_u32() % num_nodes];
 }
 #endif
 
@@ -2530,7 +2530,7 @@ static uint16_t list_nodes(Client_data *list, size_t length, Node_format *nodes,
         if (!is_timeout(list[i - 1].assoc6.timestamp, BAD_NODE_TIMEOUT)) {
             if (assoc == nullptr) {
                 assoc = &list[i - 1].assoc6;
-            } else if (rand() % 2) {
+            } else if (random_u08() % 2) {
                 assoc = &list[i - 1].assoc6;
             }
         }
@@ -2560,7 +2560,7 @@ uint16_t randfriends_nodes(DHT *dht, Node_format *nodes, uint16_t max_num)
     }
 
     uint16_t count = 0;
-    const unsigned int r = rand();
+    const uint32_t r = random_u32();
 
     for (size_t i = 0; i < DHT_FAKE_FRIEND_NUMBER; ++i) {
         count += list_nodes(dht->friends_list[(i + r) % DHT_FAKE_FRIEND_NUMBER].client_list, MAX_FRIEND_CLIENTS, nodes + count,
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) {
diff --git a/toxcore/TCP_connection.h b/toxcore/TCP_connection.h
index 658ee1f4..2d99e122 100644
--- a/toxcore/TCP_connection.h
+++ b/toxcore/TCP_connection.h
@@ -210,7 +210,7 @@ int add_tcp_relay_global(TCP_Connections *tcp_c, IP_Port ip_port, const uint8_t
  * 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);
 
 /* Returns a new TCP_Connections object associated with the secret_key.
  *
diff --git a/toxcore/group.c b/toxcore/group.c
index 317b885f..f62684ed 100644
--- a/toxcore/group.c
+++ b/toxcore/group.c
@@ -1490,12 +1490,12 @@ static void handle_friend_invite_packet(Messenger *m, uint32_t friendnumber, con
 
             /* TODO(irungentoo): what if two people enter the group at the same time and
                are given the same peer_number by different nodes? */
-            uint16_t peer_number = rand();
+            uint16_t peer_number = random_u16();
 
             unsigned int tries = 0;
 
             while (get_peer_index(g, peer_number) != -1) {
-                peer_number = rand();
+                peer_number = random_u16();
                 ++tries;
 
                 if (tries > 32) {
diff --git a/toxcore/mono_time.c b/toxcore/mono_time.c
index 415981d9..0beb7254 100644
--- a/toxcore/mono_time.c
+++ b/toxcore/mono_time.c
@@ -90,29 +90,6 @@ int is_timeout(uint64_t timestamp, uint64_t timeout)
 }
 
 
-
-/* return current UNIX time in microseconds (us). */
-uint64_t current_time_actual(void)
-{
-    uint64_t time;
-#ifdef OS_WIN32
-    /* This probably works fine */
-    FILETIME ft;
-    GetSystemTimeAsFileTime(&ft);
-    time = ft.dwHighDateTime;
-    time <<= 32;
-    time |= ft.dwLowDateTime;
-    time -= 116444736000000000ULL;
-    return time / 10;
-#else
-    struct timeval a;
-    gettimeofday(&a, nullptr);
-    time = 1000000ULL * a.tv_sec + a.tv_usec;
-    return time;
-#endif
-}
-
-
 //!TOKSTYLE-
 // No global mutable state in Tokstyle.
 #ifdef OS_WIN32
diff --git a/toxcore/mono_time.h b/toxcore/mono_time.h
index 63e0f49d..97759560 100644
--- a/toxcore/mono_time.h
+++ b/toxcore/mono_time.h
@@ -22,9 +22,6 @@ void unix_time_update(void);
 uint64_t unix_time(void);
 int is_timeout(uint64_t timestamp, uint64_t timeout);
 
-/* return current UNIX time in microseconds (us). */
-uint64_t current_time_actual(void);
-
 /* return current monotonic time in milliseconds (ms). */
 uint64_t current_time_monotonic(void);
 
diff --git a/toxcore/network.c b/toxcore/network.c
index 1c1459db..68ca43e5 100644
--- a/toxcore/network.c
+++ b/toxcore/network.c
@@ -698,7 +698,6 @@ int networking_at_startup(void)
     }
 
 #endif
-    srand((uint32_t)current_time_actual());
     at_startup_ran = 1;
     return 0;
 }
diff --git a/toxcore/onion_client.c b/toxcore/onion_client.c
index 9c59343d..819bd23f 100644
--- a/toxcore/onion_client.c
+++ b/toxcore/onion_client.c
@@ -267,7 +267,7 @@ static uint16_t random_nodes_path_onion(const Onion_Client *onion_c, Node_format
         return 0;
     }
 
-    unsigned int num_nodes = (onion_c->path_nodes_index < MAX_PATH_NODES) ? onion_c->path_nodes_index : MAX_PATH_NODES;
+    const uint32_t num_nodes = (onion_c->path_nodes_index < MAX_PATH_NODES) ? onion_c->path_nodes_index : MAX_PATH_NODES;
 
     // if (dht_non_lan_connected(onion_c->dht)) {
     if (dht_isconnected(onion_c->dht)) {
@@ -276,7 +276,7 @@ static uint16_t random_nodes_path_onion(const Onion_Client *onion_c, Node_format
         }
 
         for (i = 0; i < max_num; ++i) {
-            nodes[i] = onion_c->path_nodes[rand() % num_nodes];
+            nodes[i] = onion_c->path_nodes[random_u32() % num_nodes];
         }
     } else {
         int random_tcp = get_random_tcp_con_number(onion_c->c);
@@ -290,7 +290,7 @@ static uint16_t random_nodes_path_onion(const Onion_Client *onion_c, Node_format
             nodes[0].ip_port.ip.ip.v4.uint32 = random_tcp;
 
             for (i = 1; i < max_num; ++i) {
-                nodes[i] = onion_c->path_nodes[rand() % num_nodes];
+                nodes[i] = onion_c->path_nodes[random_u32() % num_nodes];
             }
         } else {
             unsigned int num_nodes_bs = (onion_c->path_nodes_index_bs < MAX_PATH_NODES) ? onion_c->path_nodes_index_bs :
@@ -304,7 +304,7 @@ static uint16_t random_nodes_path_onion(const Onion_Client *onion_c, Node_format
             nodes[0].ip_port.ip.ip.v4.uint32 = random_tcp;
 
             for (i = 1; i < max_num; ++i) {
-                nodes[i] = onion_c->path_nodes_bs[rand() % num_nodes_bs];
+                nodes[i] = onion_c->path_nodes_bs[random_u32() % num_nodes_bs];
             }
         }
     }
@@ -371,7 +371,7 @@ static bool onion_node_timed_out(const Onion_Node *node)
 static int random_path(const Onion_Client *onion_c, Onion_Client_Paths *onion_paths, uint32_t pathnum, Onion_Path *path)
 {
     if (pathnum == UINT32_MAX) {
-        pathnum = rand() % NUMBER_ONION_PATHS;
+        pathnum = random_u32() % NUMBER_ONION_PATHS;
     } else {
         pathnum = pathnum % NUMBER_ONION_PATHS;
     }
@@ -394,7 +394,7 @@ static int random_path(const Onion_Client *onion_c, Onion_Client_Paths *onion_pa
             onion_paths->last_path_success[pathnum] = onion_paths->path_creation_time[pathnum];
             onion_paths->last_path_used_times[pathnum] = ONION_PATH_MAX_NO_RESPONSE_USES / 2;
 
-            uint32_t path_num = rand();
+            uint32_t path_num = random_u32();
             path_num /= NUMBER_ONION_PATHS;
             path_num *= NUMBER_ONION_PATHS;
             path_num += pathnum;
@@ -1597,7 +1597,7 @@ static void do_friend(Onion_Client *onion_c, uint16_t friendnum)
             }
 
             if (is_timeout(list_nodes[i].last_pinged, interval)
-                    || (ping_random && rand() % (MAX_ONION_CLIENTS - i) == 0)) {
+                    || (ping_random && random_u32() % (MAX_ONION_CLIENTS - i) == 0)) {
                 if (client_send_announce_request(onion_c, friendnum + 1, list_nodes[i].ip_port,
                                                  list_nodes[i].public_key, nullptr, ~0) == 0) {
                     list_nodes[i].last_pinged = unix_time();
@@ -1616,12 +1616,12 @@ static void do_friend(Onion_Client *onion_c, uint16_t friendnum)
                 n = (MAX_ONION_CLIENTS / 2);
             }
 
-            if (count <= (uint32_t)rand() % MAX_ONION_CLIENTS) {
+            if (count <= random_u32() % MAX_ONION_CLIENTS) {
                 if (num_nodes != 0) {
                     unsigned int j;
 
                     for (j = 0; j < n; ++j) {
-                        unsigned int num = rand() % num_nodes;
+                        const uint32_t num = random_u32() % num_nodes;
                         client_send_announce_request(onion_c, friendnum + 1, onion_c->path_nodes[num].ip_port,
                                                      onion_c->path_nodes[num].public_key, nullptr, ~0);
                     }
@@ -1708,7 +1708,7 @@ static void do_announce(Onion_Client *onion_c)
 
         if (is_timeout(list_nodes[i].last_pinged, interval)
                 || (is_timeout(onion_c->last_announce, ONION_NODE_PING_INTERVAL)
-                    && rand() % (MAX_ONION_CLIENTS_ANNOUNCE - i) == 0)) {
+                    && random_u32() % (MAX_ONION_CLIENTS_ANNOUNCE - i) == 0)) {
             uint32_t path_to_use = list_nodes[i].path_used;
 
             if (list_nodes[i].unsuccessful_pings == ONION_NODE_MAX_PINGS - 1
@@ -1730,7 +1730,7 @@ static void do_announce(Onion_Client *onion_c)
         unsigned int num_nodes;
         Node_format *path_nodes;
 
-        if (rand() % 2 == 0 || onion_c->path_nodes_index == 0) {
+        if (random_u08() % 2 == 0 || onion_c->path_nodes_index == 0) {
             num_nodes = (onion_c->path_nodes_index_bs < MAX_PATH_NODES) ? onion_c->path_nodes_index_bs : MAX_PATH_NODES;
             path_nodes = onion_c->path_nodes_bs;
         } else {
@@ -1738,10 +1738,10 @@ static void do_announce(Onion_Client *onion_c)
             path_nodes = onion_c->path_nodes;
         }
 
-        if (count <= (uint32_t)rand() % MAX_ONION_CLIENTS_ANNOUNCE) {
+        if (count <= random_u32() % MAX_ONION_CLIENTS_ANNOUNCE) {
             if (num_nodes != 0) {
                 for (i = 0; i < (MAX_ONION_CLIENTS_ANNOUNCE / 2); ++i) {
-                    unsigned int num = rand() % num_nodes;
+                    const uint32_t num = random_u32() % num_nodes;
                     client_send_announce_request(onion_c, 0, path_nodes[num].ip_port, path_nodes[num].public_key, nullptr, ~0);
                 }
             }