From 923ea90fb23ff65071b688fbee09c00b47afc272 Mon Sep 17 00:00:00 2001
From: Ingela Anderton Andin <ingela@erlang.org>
Date: Fri, 5 Feb 2016 17:39:04 +0100
Subject: ssl: Add option signature_algs

In TLS-1.2 The signature algorithm and the hash function algorithm
used to produce the digest that is used when creating the digital signature
may be negotiated through the signature algorithm extension RFC 5246.

We want to make these algorithm pairs configurable.
In connections using lower versions of TLS these algorithms are
implicit defined and can not be negotiated or configured.

DTLS is updated to not cause dialyzer errors, but needs to get a real
implementation later.
---
 lib/ssl/src/tls_v1.erl | 62 +++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 61 insertions(+), 1 deletion(-)

(limited to 'lib/ssl/src/tls_v1.erl')

diff --git a/lib/ssl/src/tls_v1.erl b/lib/ssl/src/tls_v1.erl
index 09e378cfeb..0cf6f88782 100644
--- a/lib/ssl/src/tls_v1.erl
+++ b/lib/ssl/src/tls_v1.erl
@@ -31,7 +31,8 @@
 
 -export([master_secret/4, finished/5, certificate_verify/3, mac_hash/7,
 	 setup_keys/8, suites/1, prf/5,
-	 ecc_curves/1, oid_to_enum/1, enum_to_oid/1]).
+	 ecc_curves/1, oid_to_enum/1, enum_to_oid/1, 
+	 default_signature_algs/1, signature_algs/2]).
 
 %%====================================================================
 %% Internal application API
@@ -256,6 +257,54 @@ suites(3) ->
     ] ++ suites(2).
 
 
+
+signature_algs({3, 3}, HashSigns) ->
+    CryptoSupports =  crypto:supports(),
+    Hashes = proplists:get_value(hashs, CryptoSupports),
+    PubKeys = proplists:get_value(public_keys, CryptoSupports),
+    Supported = lists:foldl(fun({Hash, dsa = Sign} = Alg, Acc) ->
+				    case proplists:get_bool(dss, PubKeys) 
+					andalso proplists:get_bool(Hash, Hashes)
+					andalso is_pair(Hash, Sign, Hashes)
+				    of
+					true ->
+					    [Alg | Acc];
+					false ->
+					    Acc
+				    end;
+			       ({Hash, Sign} = Alg, Acc) -> 
+				    case proplists:get_bool(Sign, PubKeys) 
+					andalso proplists:get_bool(Hash, Hashes) 
+					andalso is_pair(Hash, Sign, Hashes)
+				    of
+					true ->
+					    [Alg | Acc];
+					false ->
+					    Acc
+				    end
+			    end, [], HashSigns),
+    lists:reverse(Supported).
+
+default_signature_algs({3, 3} = Version) ->
+    Default = [%% SHA2
+	       {sha512, ecdsa},
+	       {sha512, rsa},
+	       {sha384, ecdsa},
+	       {sha384, rsa},
+	       {sha256, ecdsa},
+	       {sha256, rsa},
+	       {sha224, ecdsa},
+	       {sha224, rsa},
+	       %% SHA
+	       {sha, ecdsa},
+	       {sha, rsa},
+	       {sha, dsa},
+	       %% MD5
+	       {md5, rsa}],
+    signature_algs(Version, Default);
+default_signature_algs(_) ->
+    undefined.
+
 %%--------------------------------------------------------------------
 %%% Internal functions
 %%--------------------------------------------------------------------
@@ -340,6 +389,17 @@ finished_label(client) ->
 finished_label(server) ->
     <<"server finished">>.
 
+is_pair(sha, dsa, _) ->
+    true;
+is_pair(_, dsa, _) ->
+    false;
+is_pair(Hash, ecdsa, Hashs) ->
+    AtLeastSha = Hashs -- [md2,md4,md5],
+    lists:member(Hash, AtLeastSha);
+is_pair(Hash, rsa, Hashs) ->
+    AtLeastMd5 = Hashs -- [md2,md4],
+    lists:member(Hash, AtLeastMd5).
+
 %% list ECC curves in prefered order
 ecc_curves(_Minor) ->
     TLSCurves = [sect571r1,sect571k1,secp521r1,brainpoolP512r1,
-- 
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