Save session data between TLS connecitons.

Save session data.diff

Author: Kasper Lund <kasper@toit.io>
Date:   Mon Jun 12 13:14:22 2023 +0200

    Store TLS session data in RTC memory (#715)

diff --git a/src/service/brokers/http/connection.toit b/src/service/brokers/http/connection.toit
index 35ad787..e5b9888 100644
--- a/src/service/brokers/http/connection.toit
+++ b/src/service/brokers/http/connection.toit
@@ -6,9 +6,9 @@ import http
 import net
 import net.x509
 import reader show Reader
+import system.storage
 import ....shared.server_config show ServerConfigHttp
 
-
 class HttpConnection_:
   client_/http.Client? := ?
   config_/ServerConfigHttp
@@ -17,8 +17,9 @@ class HttpConnection_:
     if config_.root_certificate_ders:
       root_certificates := config_.root_certificate_ders.map:
         x509.Certificate.parse it
-
-      client_ = http.Client.tls network --root_certificates=root_certificates
+      client_ = http.Client.tls network
+          --root_certificates=root_certificates
+          --security_store=HttpSecurityStore_
     else:
       client_ = http.Client network
 
@@ -60,3 +61,21 @@ class HttpConnection_:
       block.call body
     finally:
       catch: response.drain
+
+class HttpSecurityStore_ extends http.SecurityStore:
+  // We store the cached session data in RTC memory. This means that
+  // it survives deep sleeps, but that any loss of power or firmware
+  // update will clear it.
+  static bucket ::= storage.Bucket.open --ram "toit.io/artemis/tls"
+
+  store_session_data host/string port/int data/ByteArray -> none:
+    bucket[key_ host port] = data
+
+  delete_session_data host/string port/int -> none:
+    bucket.remove (key_ host port)
+
+  retrieve_session_data host/string port/int -> ByteArray?:
+    return bucket.get (key_ host port)
+
+  key_ host/string port/int -> string:
+    return "$host:$port"