ssl: Add max value for CRL cache

Author: IngelaAndin

lib/ssl/doc/ssl_app.md

@@ -65,6 +65,53 @@ The environment parameters can be set on the command line, for example:
   might be configurable, by the SSL application. This option can be overridden
   by the version option to `ssl:connect/2,3` and `ssl:listen/2`.
 
+ - **`max_crl_cache = pos_integer() <optional>`** - Sets the
+  maximum number of entries  allowed in the default crl store. Defaults to 150. Size limit
+  is enforced by emptying cache when limit is reached.
+
+- **`ssl_pem_cache_clean = pos_integer() <optional>`** - Number of milliseconds
+  between PEM cache validations. Defaults to 2 minutes.
+
+  Note: The cache can be reloaded by calling `ssl:clear_pem_cache/0`.
+
+- **`bypass_pem_cache = boolean() <optional>`** - Introduced in ssl-8.0.2.
+  Disables the PEM-cache. Can be used as a workaround for the PEM-cache
+  bottleneck before ssl-8.1.1. Defaults to false.
+
+- **`internal_active_n = integer() <optional>`** - For TLS connections this
+  value is used to handle the internal socket. As the implementation was changed
+  from an active once to an active N behavior (N = 100), for performance
+  reasons, this option exist for possible tweaking or restoring of the old
+  behavior (internal_active_n = 1) in unforeseen scenarios. The option will not
+  affect erlang distribution over TLS that will always run in active N mode.
+  Added in ssl-9.1 (OTP-21.2).
+
+- **`server_session_tickets_amount = integer() <optional>`** - Number of session
+  tickets sent by the server. It must be greater than 0. Defaults to 3.
+
+- **`server_session_ticket_lifetime = integer() <optional>`** - Lifetime of
+  session tickets sent by the server. Servers must not use any value greater
+  than 604800 seconds (7 days). Expired tickets are automatically removed.
+  Defaults to 7200 seconds (2 hours).
+
+- **`server_session_ticket_store_size = integer() <optional>`** - Sets the
+  maximum size of the server session ticket store (stateful tickets). Defaults
+  to 1000. Size limit is enforced by dropping old tickets.
+
+- **`server_session_ticket_max_early_data = integer() <optional>`** - Sets the
+  maximum size of the early data that the server accepts and also configures its
+  NewSessionTicket messages to include this same size limit in their
+  early_data_indication extension. Defaults to 16384. Size limit is enforced by
+  both client and server.
+
+- **`client_session_ticket_lifetime = integer() <optional>`** - Lifetime of
+  session tickets in the client ticket store. Expired tickets are automatically
+  removed. Defaults to 7200 seconds (2 hours).
+
+- **`client_session_ticket_store_size = integer() <optional>`** - Sets the
+  maximum size of the client session ticket store. Defaults to 1000. Size limit
+  is enforced by dropping old tickets.
+
 - **`session_lifetime = integer() <optional>`** - Maximum lifetime of the
   session data in seconds. Defaults to 24 hours which is the maximum recommended
   lifetime by [RFC 5246](http://www.ietf.org/rfc/5246rfc.txt). However sessions
@@ -108,54 +155,11 @@ The environment parameters can be set on the command line, for example:
   entries will be invalidated regardless of their remaining lifetime. Defaults
   to 1000. Recommended ssl-8.2.1 or later for this option to work as intended.
 
-- **`ssl_pem_cache_clean = integer() <optional>`** - Number of milliseconds
-  between PEM cache validations. Defaults to 2 minutes.
-
-  Note: The cache can be reloaded by calling `ssl:clear_pem_cache/0`.
-
-- **`bypass_pem_cache = boolean() <optional>`** - Introduced in ssl-8.0.2.
-  Disables the PEM-cache. Can be used as a workaround for the PEM-cache
-  bottleneck before ssl-8.1.1. Defaults to false.
-
-- **`alert_timeout = integer() <optional>`** - Number of milliseconds between
+- **`alert_timeout = pos_integer() <optional>`** - Number of milliseconds between
   sending of a fatal alert and closing the connection. Waiting a little while
   improves the peers chances to properly receiving the alert so it may shutdown
   gracefully. Defaults to 5000 milliseconds.
 
-- **`internal_active_n = integer() <optional>`** - For TLS connections this
-  value is used to handle the internal socket. As the implementation was changed
-  from an active once to an active N behavior (N = 100), for performance
-  reasons, this option exist for possible tweaking or restoring of the old
-  behavior (internal_active_n = 1) in unforeseen scenarios. The option will not
-  affect erlang distribution over TLS that will always run in active N mode.
-  Added in ssl-9.1 (OTP-21.2).
-
-- **`server_session_tickets_amount = integer() <optional>`** - Number of session
-  tickets sent by the server. It must be greater than 0. Defaults to 3.
-
-- **`server_session_ticket_lifetime = integer() <optional>`** - Lifetime of
-  session tickets sent by the server. Servers must not use any value greater
-  than 604800 seconds (7 days). Expired tickets are automatically removed.
-  Defaults to 7200 seconds (2 hours).
-
-- **`server_session_ticket_store_size = integer() <optional>`** - Sets the
-  maximum size of the server session ticket store (stateful tickets). Defaults
-  to 1000. Size limit is enforced by dropping old tickets.
-
-- **`server_session_ticket_max_early_data = integer() <optional>`** - Sets the
-  maximum size of the early data that the server accepts and also configures its
-  NewSessionTicket messages to include this same size limit in their
-  early_data_indication extension. Defaults to 16384. Size limit is enforced by
-  both client and server.
-
-- **`client_session_ticket_lifetime = integer() <optional>`** - Lifetime of
-  session tickets in the client ticket store. Expired tickets are automatically
-  removed. Defaults to 7200 seconds (2 hours).
-
-- **`client_session_ticket_store_size = integer() <optional>`** - Sets the
-  maximum size of the client session ticket store. Defaults to 1000. Size limit
-  is enforced by dropping old tickets.
-
 ## Error Logger and Event Handlers
 
 The SSL application uses [OTP logger](`m:logger`). TLS/DTLS alerts are logged on

lib/ssl/src/ssl_config.erl

@@ -32,6 +32,8 @@
 -define(DEFAULT_MAX_SESSION_CACHE, 1000).
 -define(TWO_HOURS, 7200).
 -define(SEVEN_DAYS, 604800). 
+-define(DEFAULT_MAX_CRL_CACHE, 150).
+-define(INTERNAL_ACTIVE_N, 100).
 
 %% Connection parameter configuration
 -export([init/2,
@@ -44,6 +46,7 @@
 %% Application configuration
 -export([pre_1_3_session_opts/1,
          get_max_early_data_size/0,
+         get_max_crl_cache/0,
          get_ticket_lifetime/0,
          get_ticket_store_size/0,
          get_internal_active_n/0,
@@ -138,6 +141,14 @@ get_internal_active_n(true) ->
 get_internal_active_n(false) ->
     application_int(internal_active_n, ?INTERNAL_ACTIVE_N).
 
+get_max_crl_cache() ->
+    case application:get_env(ssl, max_crl_cache) of
+	{ok, Size} when is_integer(Size) ->
+	    Size;
+	_  ->
+	    ?DEFAULT_MAX_CRL_CACHE
+    end.
+
 %%====================================================================
 %% Internal functions 
 %%====================================================================	     
@@ -278,6 +289,9 @@ prio_dsa(DSA) ->
     end,
     lists:sort(Order, DSA).
 
+%%====================================================================
+%% Internal functions 
+%%====================================================================	     
 init_manager_name(false) ->
     put(ssl_manager, ssl_manager:name(normal)),
     put(ssl_pem_cache, ssl_pem_cache:name(normal));

lib/ssl/src/ssl_crl_cache.erl

@@ -234,10 +234,12 @@ cache_lookup(URL, {{Cache, _}, _}) ->
 
 handle_http(URI, Rest, {_,  [{http, Timeout}]} = CRLDbInfo) ->
     CRLs = http_lookup(URI, Rest, CRLDbInfo, Timeout),
-    %% Uncomment to improve performance, but need to 
-    %% implement cache limit and or cleaning to prevent 
-    %% DoS attack possibilities
-    %%insert(URI, {der, CRLs}),
+    case CRLs of
+        not_available ->
+            ok;
+        _ ->
+            insert(URI, {der, CRLs})
+    end,
     CRLs;
 handle_http(_, Rest, CRLDbInfo) ->
     get_crls(Rest, CRLDbInfo).

lib/ssl/src/ssl_manager.erl

@@ -68,7 +68,8 @@
 	  session_cache_client_max   :: integer(),
           session_client_invalidator :: undefined | pid(),
           options                    :: list(),
-          client_session_order       :: gb_trees:tree()
+          client_session_order       :: gb_trees:tree(),
+          max_crl_db_entries         :: pos_integer()
 	 }).
 
 -define(GEN_UNIQUE_ID_MAX_TRIES, 10).
@@ -268,7 +269,8 @@ init([ManagerName, PemCacheName, Opts]) ->
 		session_cache_client_max = ClientSessMax,
 		session_client_invalidator = undefined,
                 options = Opts,
-                client_session_order = gb_trees:empty()
+                client_session_order = gb_trees:empty(),
+                max_crl_db_entries = ssl_config:get_max_crl_cache()
 	       }}.
 
 %%--------------------------------------------------------------------
@@ -307,8 +309,9 @@ handle_call({{connection_init, Trustedcerts, Role, {CRLCb, UserCRLDb}}, Pid}, _F
     end;
 
 handle_call({{insert_crls, Path, CRLs}, _}, _From,   
-	    #state{certificate_db = Db} = State) ->
-    ssl_pkix_db:add_crls(Db, Path, CRLs),
+	    #state{certificate_db = Db,
+                   max_crl_db_entries = Max} = State) ->
+    ssl_pkix_db:add_crls(Db, Path, CRLs, Max),
     {reply, ok, State};
 
 handle_call({{delete_crls, CRLsOrPath}, _}, _From,   
@@ -345,8 +348,8 @@ handle_cast({invalidate_session, Host, Port,
 		   session_cache_client_cb = CacheCb} = State) ->
     invalidate_session(Cache, CacheCb, {{Host, Port}, ID}, Session, State);
 handle_cast({insert_crls, Path, CRLs},   
-	    #state{certificate_db = Db} = State) ->
-    ssl_pkix_db:add_crls(Db, Path, CRLs),
+	    #state{certificate_db = Db, max_crl_db_entries = Max} = State) ->
+    ssl_pkix_db:add_crls(Db, Path, CRLs, Max),
     {noreply, State};
 
 handle_cast({delete_crls, CRLsOrPath},   

lib/ssl/src/ssl_pkix_db.erl

@@ -32,14 +32,27 @@
 -include_lib("kernel/include/file.hrl").
 -include_lib("kernel/include/logger.hrl").
 
--export([create/1, create_pem_cache/1, 
-	 add_crls/3, remove_crls/2, remove/1, add_trusted_certs/3, 
+-export([create/1,
+         create_pem_cache/1,
+	 add_crls/4,
+         remove_crls/2,
+         remove/1,
+         add_trusted_certs/3,
          refresh_trusted_certs/2,
          refresh_trusted_certs/3,
 	 extract_trusted_certs/1,
-	 remove_trusted_certs/2, insert/3, remove/2, clear/1, db_size/1,
-	 ref_count/3, lookup_trusted_cert/4, foldl/3, select_certentries_by_ref/2,
-	 select_certs_by_ref/2, decode_pem_file/1, lookup/2]).
+	 remove_trusted_certs/2,
+         insert/3,
+         remove/2,
+         clear/1,
+         db_size/1,
+	 ref_count/3,
+         lookup_trusted_cert/4,
+         foldl/3,
+         select_certentries_by_ref/2,
+	 select_certs_by_ref/2,
+         decode_pem_file/1,
+         lookup/2]).
 
 %%====================================================================
 %% Internal application API
@@ -365,6 +378,15 @@ new_trusted_cert_entry(File, [CertsDb, RefsDb, _ | _]) ->
             Error
     end.
 
+add_crls([_,_,_, {Cache, _} | _]= DB, Path, CRLs, MaxSize) ->
+    case ets:info(Cache, size) + length(CRLs) > MaxSize of
+        true ->
+            ets:delete_all_objects(Cache),
+            add_crls(DB, Path, CRLs);
+        false ->
+            add_crls(DB, Path, CRLs)
+    end.
+
 add_crls([_,_,_, {_, Mapping} | _], ?NO_DIST_POINT, CRLs) ->
     [add_crls(CRL, Mapping) || CRL <- CRLs];
 add_crls([_,_,_, {Cache, Mapping} | _], Path, CRLs) ->