From f4665e43e858a6695585fd0350ceebad150e57b6 Mon Sep 17 00:00:00 2001
From: Jonathan Almeida <git@jonalmeida.com>
Date: Wed, 24 May 2017 18:28:07 -0400
Subject: [PATCH] Add a backward compatible way of getting random bytes

---
 src/websocket_client.erl | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/src/websocket_client.erl b/src/websocket_client.erl
index 07489fc..2591993 100644
--- a/src/websocket_client.erl
+++ b/src/websocket_client.erl
@@ -241,7 +241,7 @@ error_info(Handler, Reason, State) ->
 -spec generate_ws_key() ->
                              binary().
 generate_ws_key() ->
-    base64:encode(crypto:strong_rand_bytes(16)).
+    base64:encode(rand_bytes(16)).
 
 %% @doc Validate handshake response challenge
 -spec validate_handshake(HandshakeResponse :: binary(), Key :: binary()) -> {ok, binary()} | {error, term()}.
@@ -430,7 +430,7 @@ encode_frame({Type, Payload}) ->
     Opcode = websocket_req:name_to_opcode(Type),
     Len = iolist_size(Payload),
     BinLen = payload_length_to_binary(Len),
-    MaskingKeyBin = crypto:strong_rand_bytes(4),
+    MaskingKeyBin = rand_bytes(4),
     << MaskingKey:32 >> = MaskingKeyBin,
     Header = << 1:1, 0:3, Opcode:4, 1:1, BinLen/bits, MaskingKeyBin/bits >>,
     MaskedPayload = mask_payload(MaskingKey, Payload),
@@ -482,3 +482,12 @@ set_continuation_if_empty(WSReq, Opcode) ->
         _ ->
             WSReq
     end.
+
+rand_bytes(N) ->
+  case has_crypto_strong_rand_bytes() of
+    true  -> crypto:strong_rand_bytes(N);
+    false -> (fun crypto:rand_bytes/1)(N)
+  end.
+
+has_crypto_strong_rand_bytes() ->
+  erlang:function_exported(crypto, strong_rand_bytes, 1).