From 96209481ad9b1879e1736294a9c9b5c6d853631b Mon Sep 17 00:00:00 2001
From: Raimo Niskanen <raimo@erlang.org>
Date: Thu, 24 Jan 2019 14:01:16 +0100
Subject: Cache strong_random_bytes for IV

---
 lib/ssl/src/ssl_cipher.erl | 20 ++++++++++++--------
 1 file changed, 12 insertions(+), 8 deletions(-)

(limited to 'lib/ssl')

diff --git a/lib/ssl/src/ssl_cipher.erl b/lib/ssl/src/ssl_cipher.erl
index ab82b487b9..da2be0e50f 100644
--- a/lib/ssl/src/ssl_cipher.erl
+++ b/lib/ssl/src/ssl_cipher.erl
@@ -97,7 +97,8 @@ cipher_init(?AES_GCM, IV, Key) ->
 cipher_init(?CHACHA20_POLY1305, IV, Key) ->
     #cipher_state{iv = IV, key = Key, tag_len = 16};
 cipher_init(_BCA, IV, Key) ->
-    #cipher_state{iv = IV, key = Key}.
+    %% Initialize random IV cache, not used for aead ciphers
+    #cipher_state{iv = IV, key = Key, state = <<>>}.
 
 nonce_seed(Seed, CipherState) ->
     CipherState#cipher_state{nonce = Seed}.
@@ -156,14 +157,21 @@ block_cipher(Fun, BlockSz, #cipher_state{key=Key, iv=IV} = CS0,
     NextIV = next_iv(T, IV),
     {T, CS0#cipher_state{iv=NextIV}};
 
-block_cipher(Fun, BlockSz, #cipher_state{key=Key, iv=IV} = CS0,
+block_cipher(Fun, BlockSz, #cipher_state{key=Key, iv=IV, state = IV_Cache0} = CS0,
 	     Mac, Fragment, {3, N})
   when N == 2; N == 3 ->
-    NextIV = random_iv(IV),
+    IV_Size = byte_size(IV),
+    <<NextIV:IV_Size/binary, IV_Cache/binary>> =
+        case IV_Cache0 of
+            <<>> ->
+                random_bytes(IV_Size bsl 5); % 32 IVs
+            _ ->
+                IV_Cache0
+        end,
     L0 = build_cipher_block(BlockSz, Mac, Fragment),
     L = [NextIV|L0],
     T = Fun(Key, IV, L),
-    {T, CS0#cipher_state{iv=NextIV}}.
+    {T, CS0#cipher_state{iv=NextIV, state = IV_Cache}}.
 
 %%--------------------------------------------------------------------
 -spec decipher(cipher_enum(), integer(), #cipher_state{}, binary(), 
@@ -930,10 +938,6 @@ padding_with_len(TextLen, BlockSize) ->
             binary:copy(<<PadLen>>, PadLen + 1)
     end.
 
-random_iv(IV) ->
-    IVSz = byte_size(IV),
-    random_bytes(IVSz).
-
 next_iv(Bin, IV) ->
     BinSz = byte_size(Bin),
     IVSz = byte_size(IV),
-- 
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