From 83f9c5c032cc502df38b52d8a5b0389657b37801 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?P=C3=A9ter=20Dimitrov?= <peterdmv@erlang.org>
Date: Wed, 17 Jul 2019 16:40:04 +0200
Subject: ssl: Implement psk_key_exchange_modes extension

Implement encode/decode of psk_key_exchange_modes.
---
 lib/ssl/src/ssl_handshake.erl     | 40 +++++++++++++++++++++++++++++++++++++--
 lib/ssl/src/tls_handshake_1_3.hrl | 36 +++++++++++++++++++++++------------
 2 files changed, 62 insertions(+), 14 deletions(-)

(limited to 'lib')

diff --git a/lib/ssl/src/ssl_handshake.erl b/lib/ssl/src/ssl_handshake.erl
index 488e4bb72a..07c7f10f2b 100644
--- a/lib/ssl/src/ssl_handshake.erl
+++ b/lib/ssl/src/ssl_handshake.erl
@@ -709,7 +709,13 @@ encode_extensions([#key_share_server_hello{server_share = ServerShare0} | Rest],
 encode_extensions([#key_share_hello_retry_request{selected_group = Group0} | Rest], Acc) ->
     Group = tls_v1:group_to_enum(Group0),
     encode_extensions(Rest, <<?UINT16(?KEY_SHARE_EXT),
-                              ?UINT16(2), ?UINT16(Group), Acc/binary>>).
+                              ?UINT16(2), ?UINT16(Group), Acc/binary>>);
+encode_extensions([#psk_key_exchange_modes{ke_modes = KEModes0} | Rest], Acc) ->
+    KEModes = encode_psk_key_exchange_modes(KEModes0),
+    KEModesLen = byte_size(KEModes),
+    ExtLen = KEModesLen + 1,
+    encode_extensions(Rest, <<?UINT16(?PSK_KEY_EXCHANGE_MODES_EXT),
+                              ?UINT16(ExtLen), ?BYTE(KEModesLen), KEModes/binary, Acc/binary>>).
 
 
 encode_client_protocol_negotiation(undefined, _) ->
@@ -2093,6 +2099,17 @@ encode_key_share_entry(#key_share_entry{
     Len = byte_size(KeyExchange),
     <<?UINT16((tls_v1:group_to_enum(Group))),?UINT16(Len),KeyExchange/binary>>.
 
+encode_psk_key_exchange_modes(KEModes) ->
+    encode_psk_key_exchange_modes(lists:reverse(KEModes), <<>>).
+%%
+encode_psk_key_exchange_modes([], Acc) ->
+    Acc;
+encode_psk_key_exchange_modes([psk_ke|T], Acc) ->
+    encode_psk_key_exchange_modes(T, <<?BYTE(?PSK_KE),Acc/binary>>);
+encode_psk_key_exchange_modes([psk_dhe_ke|T], Acc) ->
+    encode_psk_key_exchange_modes(T, <<?BYTE(?PSK_DHE_KE),Acc/binary>>).
+
+
 hello_extensions_list(HelloExtensions) ->
     [Ext || {_, Ext} <- maps:to_list(HelloExtensions), Ext =/= undefined].
 
@@ -2445,6 +2462,13 @@ decode_extensions(<<?UINT16(?KEY_SHARE_EXT), ?UINT16(Len),
                                #key_share_hello_retry_request{
                                   selected_group = tls_v1:enum_to_group(Group)}});
 
+decode_extensions(<<?UINT16(?PSK_KEY_EXCHANGE_MODES_EXT), ?UINT16(Len),
+                       ExtData:Len/binary, Rest/binary>>, Version, MessageType, Acc) ->
+    <<?BYTE(PLen),KEModes:PLen/binary>> = ExtData,
+    decode_extensions(Rest, Version, MessageType,
+                      Acc#{psk_key_exchange_modes =>
+                               #psk_key_exchange_modes{
+                                  ke_modes = decode_psk_key_exchange_modes(KEModes)}});
 
 %% Ignore data following the ClientHello (i.e.,
 %% extensions) if not understood.
@@ -2504,6 +2528,18 @@ decode_protocols(<<?BYTE(Len), Protocol:Len/binary, Rest/binary>>, Acc) ->
 decode_protocols(_Bytes, _Acc) ->
     {error, invalid_protocols}.
 
+
+decode_psk_key_exchange_modes(KEModes) ->
+    decode_psk_key_exchange_modes(KEModes, []).
+%%
+decode_psk_key_exchange_modes(<<>>, Acc) ->
+    lists:reverse(Acc);
+decode_psk_key_exchange_modes(<<?BYTE(?PSK_KE), Rest/binary>>, Acc) ->
+    decode_psk_key_exchange_modes(Rest, [psk_ke|Acc]);
+decode_psk_key_exchange_modes(<<?BYTE(?PSK_DHE_KE), Rest/binary>>, Acc) ->
+    decode_psk_key_exchange_modes(Rest, [psk_dhe_ke|Acc]).
+
+
 %% encode/decode stream of certificate data to/from list of certificate data
 certs_to_list(ASN1Certs) ->
     certs_to_list(ASN1Certs, []).
@@ -3042,7 +3078,7 @@ empty_extensions({3,4}, client_hello) ->
       %% padding => undefined,
       key_share => undefined,
       pre_shared_key => undefined,
-      %% psk_key_exhange_modes => undefined,
+      psk_key_exchange_modes => undefined,
       %% early_data => undefined,
       %% cookie => undefined,
       client_hello_versions => undefined,
diff --git a/lib/ssl/src/tls_handshake_1_3.hrl b/lib/ssl/src/tls_handshake_1_3.hrl
index 7ae1b93e1c..78756c69db 100644
--- a/lib/ssl/src/tls_handshake_1_3.hrl
+++ b/lib/ssl/src/tls_handshake_1_3.hrl
@@ -74,29 +74,41 @@
           y                %     opaque Y[coordinate_length];
          }).
 
+%% RFC 8446 4.2.9.  Pre-Shared Key Exchange Modes
+
+%% enum { psk_ke(0), psk_dhe_ke(1), (255) } PskKeyExchangeMode;
 -define(PSK_KE, 0).
 -define(PSK_DHE_KE, 1).
 
--record(psk_keyexchange_modes, {
+-record(psk_key_exchange_modes, {
           ke_modes % ke_modes<1..255>
          }).
+
+%% RFC 8446 4.2.10.  Early Data Indication
 -record(empty, {
          }).
 -record(early_data_indication, {
           indication % uint32 max_early_data_size (new_session_ticket) | 
           %% #empty{} (client_hello, encrypted_extensions)
          }).
--record(psk_identity, {
-          identity, %     opaque identity<1..2^16-1>
-          obfuscated_ticket_age %  uint32
-         }).
--record(offered_psks, {
-          psk_identity,    %identities<7..2^16-1>;
-          psk_binder_entry %binders<33..2^16-1>,  opaque PskBinderEntry<32..255>
-         }).
--record(pre_shared_keyextension,{ 
-          extension %OfferedPsks (client_hello) | uint16 selected_identity (server_hello)
-         }).
+
+%% RFC 8446 4.2.11. Pre-Shared Key Extension
+-record(psk_identity,
+        {
+         identity,             % opaque identity<1..2^16-1>
+         obfuscated_ticket_age % uint32
+        }).
+
+-record(offered_psks,
+        {
+         identities,    % PskIdentity identities<7..2^16-1>;
+         binders        % PskBinderEntry binders<33..2^16-1>; opaque PskBinderEntry<32..255>
+        }).
+
+-record(pre_shared_key,
+        {
+         data          % OfferedPsks (client_hello) | uint16 selected_identity (server_hello)
+        }).
 
 %% RFC 8446 B.3.1.2.
 -record(cookie, {
-- 
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