Fix OpenSSL::SSL::Context::Client#alpn_protocol=

spec/std/openssl/ssl/socket_spec.cr

@@ -93,6 +93,26 @@ describe OpenSSL::SSL::Socket do
     )
   end
 
+  it "returns selected alpn protocol" do
+    tcp_server = TCPServer.new("127.0.0.1", 0)
+    server_context, client_context = ssl_context_pair
+
+    server_context.alpn_protocol = "h2"
+    client_context.alpn_protocol = "h2"
+
+    OpenSSL::SSL::Server.open(tcp_server, server_context) do |server|
+      spawn do
+        Client.open(TCPSocket.new(tcp_server.local_address.address, tcp_server.local_address.port), client_context, hostname: "example.com") do |socket|
+          socket.alpn_protocol.should eq("h2")
+        end
+      end
+
+      client = server.accept
+      client.alpn_protocol.should eq("h2")
+      client.close
+    end
+  end
+
   it "accepts clients that only write then close the connection" do
     tcp_server = TCPServer.new("127.0.0.1", 0)
     server_context, client_context = ssl_context_pair

src/openssl/lib_ssl.cr

@@ -261,6 +261,7 @@ lib LibSSL
 
     fun ssl_get0_alpn_selected = SSL_get0_alpn_selected(handle : SSL, data : Char**, len : LibC::UInt*) : Void
     fun ssl_ctx_set_alpn_select_cb = SSL_CTX_set_alpn_select_cb(ctx : SSLContext, cb : ALPNCallback, arg : Void*) : Void
+    fun ssl_ctx_set_alpn_protos = SSL_CTX_set_alpn_protos(ctx : SSLContext, protos : Char*, protos_len : Int) : Int
   {% end %}
 
   {% if compare_versions(OPENSSL_VERSION, "1.0.2") >= 0 %}

src/openssl/ssl/context.cr

@@ -98,6 +98,14 @@ abstract class OpenSSL::SSL::Context
         end
       }, hostname.as(Void*))
     end
+
+    private def alpn_protocol=(protocol : Bytes)
+      {% if LibSSL.has_method?(:ssl_ctx_set_alpn_protos) %}
+        LibSSL.ssl_ctx_set_alpn_protos(@handle, protocol, protocol.size)
+      {% else %}
+        raise NotImplementedError.new("LibSSL.ssl_ctx_set_alpn_protos")
+      {% end %}
+    end
   end
 
   class Server < Context
@@ -173,6 +181,24 @@ abstract class OpenSSL::SSL::Context
         raise OpenSSL::Error.new("SSL_CTX_set_num_tickets") if ret != 1
       {% end %}
     end
+
+    private def alpn_protocol=(protocol : Bytes)
+      {% if LibSSL.has_method?(:ssl_ctx_set_alpn_select_cb) %}
+        alpn_cb = ->(ssl : LibSSL::SSL, o : LibC::Char**, olen : LibC::Char*, i : LibC::Char*, ilen : LibC::Int, data : Void*) {
+          proto = Box(Bytes).unbox(data)
+          ret = LibSSL.ssl_select_next_proto(o, olen, proto, 2, i, ilen)
+          if ret != LibSSL::OPENSSL_NPN_NEGOTIATED
+            LibSSL::SSL_TLSEXT_ERR_NOACK
+          else
+            LibSSL::SSL_TLSEXT_ERR_OK
+          end
+        }
+        @alpn_protocol = alpn_protocol = Box.box(protocol)
+        LibSSL.ssl_ctx_set_alpn_select_cb(@handle, alpn_cb, alpn_protocol)
+      {% else %}
+        raise NotImplementedError.new("LibSSL.ssl_ctx_set_alpn_select_cb")
+      {% end %}
+    end
   end
 
   protected def initialize(method : LibSSL::SSLMethod)
@@ -429,24 +455,6 @@ abstract class OpenSSL::SSL::Context
     self.alpn_protocol = proto
   end
 
-  private def alpn_protocol=(protocol : Bytes)
-    {% if LibSSL.has_method?(:ssl_ctx_set_alpn_select_cb) %}
-      alpn_cb = ->(ssl : LibSSL::SSL, o : LibC::Char**, olen : LibC::Char*, i : LibC::Char*, ilen : LibC::Int, data : Void*) {
-        proto = Box(Bytes).unbox(data)
-        ret = LibSSL.ssl_select_next_proto(o, olen, proto, 2, i, ilen)
-        if ret != LibSSL::OPENSSL_NPN_NEGOTIATED
-          LibSSL::SSL_TLSEXT_ERR_NOACK
-        else
-          LibSSL::SSL_TLSEXT_ERR_OK
-        end
-      }
-      @alpn_protocol = alpn_protocol = Box.box(protocol)
-      LibSSL.ssl_ctx_set_alpn_select_cb(@handle, alpn_cb, alpn_protocol)
-    {% else %}
-      raise NotImplementedError.new("LibSSL.ssl_ctx_set_alpn_select_cb")
-    {% end %}
-  end
-
   # Sets this context verify param to the default one of the given name.
   #
   # Depending on the OpenSSL version, the available defaults are