ssl: Improve handling of signature algorithms

TLS 1.2 ClientHello caused handshake failure in the TLS 1.2 server
if the signature_algorithms_cert extension contained legacy algorithms.

Update TLS 1.2 server to properly handle legacy signature algorithms
in the signature_algorithms_cert extension.

Update TLS 1.3 client so that it can send legacy algorithms in its
signature_algorithms_cert extension.

3 files changed, 30 insertions, 7 deletions

diff --git a/lib/ssl/src/ssl_cipher.erl b/lib/ssl/src/ssl_cipher.erl
index 21db887bb5..4da50d2af8 100644
--- a/lib/ssl/src/ssl_cipher.erl
+++ b/lib/ssl/src/ssl_cipher.erl
@@ -923,6 +923,12 @@ signature_scheme(rsa_pss_pss_sha384) -> ?RSA_PSS_PSS_SHA384;
 signature_scheme(rsa_pss_pss_sha512) -> ?RSA_PSS_PSS_SHA512;
 signature_scheme(rsa_pkcs1_sha1) -> ?RSA_PKCS1_SHA1;
 signature_scheme(ecdsa_sha1) -> ?ECDSA_SHA1;
+%% Handling legacy signature algorithms
+signature_scheme({Hash0, Sign0}) ->
+    Hash = hash_algorithm(Hash0),
+    Sign = sign_algorithm(Sign0),
+    <<?UINT16(SigAlg)>> = <<?BYTE(Hash),?BYTE(Sign)>>,
+    SigAlg;
 signature_scheme(?RSA_PKCS1_SHA256) -> rsa_pkcs1_sha256;
 signature_scheme(?RSA_PKCS1_SHA384) -> rsa_pkcs1_sha384;
 signature_scheme(?RSA_PKCS1_SHA512) -> rsa_pkcs1_sha512;
@@ -962,7 +968,9 @@ scheme_to_components(rsa_pss_pss_sha256) -> {sha256, rsa_pss_pss, undefined};
 scheme_to_components(rsa_pss_pss_sha384) -> {sha384, rsa_pss_pss, undefined};
 scheme_to_components(rsa_pss_pss_sha512) -> {sha512, rsa_pss_pss, undefined};
 scheme_to_components(rsa_pkcs1_sha1) -> {sha1, rsa_pkcs1, undefined};
-scheme_to_components(ecdsa_sha1) -> {sha1, ecdsa, undefined}.
+scheme_to_components(ecdsa_sha1) -> {sha1, ecdsa, undefined};
+%% Handling legacy signature algorithms
+scheme_to_components({Hash,Sign}) -> {Hash, Sign, undefined}.
 
 
 %% TODO: Add support for EC and RSA-SSA signatures
diff --git a/lib/ssl/src/ssl_handshake.erl b/lib/ssl/src/ssl_handshake.erl
index f68d3e9b26..3d2abb714f 100644
--- a/lib/ssl/src/ssl_handshake.erl
+++ b/lib/ssl/src/ssl_handshake.erl
@@ -1186,10 +1186,7 @@ signature_algs_ext(undefined) ->
 signature_algs_ext(SignatureSchemes0) ->
     %% The SSL option signature_algs contains both hash-sign algorithms (tuples) and
     %% signature schemes (atoms) if TLS 1.3 is configured.
-    %% Filter out all hash-sign tuples when creating the signature_algs extension.
-    %% (TLS 1.3 specific record type)
-    SignatureSchemes = lists:filter(fun is_atom/1, SignatureSchemes0),
-    #signature_algorithms{signature_scheme_list = SignatureSchemes}.
+    #signature_algorithms{signature_scheme_list = SignatureSchemes0}.
 
 signature_algs_cert(undefined) ->
     undefined;
diff --git a/lib/ssl/src/tls_v1.erl b/lib/ssl/src/tls_v1.erl
index 27cd5765e5..f7c8c770ae 100644
--- a/lib/ssl/src/tls_v1.erl
+++ b/lib/ssl/src/tls_v1.erl
@@ -606,8 +606,26 @@ signature_schemes(Version, SignatureSchemes) when is_tuple(Version)
                           Acc
                   end;
               %% Special clause for filtering out the legacy hash-sign tuples.
-              (_ , Acc) ->
-                  Acc
+              ({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,
     Supported = lists:foldl(Fun, [], SignatureSchemes),
     lists:reverse(Supported);