Factor out session ID into a standalone entity

libtransmission/CMakeLists.txt

@@ -46,6 +46,7 @@ set(${PROJECT_NAME}_SOURCES
     rpcimpl.c
     rpc-server.c
     session.c
+    session-id.c
     stats.c
     torrent.c
     torrent-ctor.c
@@ -105,6 +106,7 @@ set(${PROJECT_NAME}_PUBLIC_HEADERS
     makemeta.h
     quark.h
     rpcimpl.h
+    session-id.h
     tr-getopt.h
     transmission.h
     utils.h

libtransmission/rpc-server.c

@@ -30,6 +30,7 @@
 #include "rpcimpl.h"
 #include "rpc-server.h"
 #include "session.h"
+#include "session-id.h"
 #include "trevent.h"
 #include "utils.h"
 #include "variant.h"
@@ -63,9 +64,6 @@ struct tr_rpc_server
     char             * whitelistStr;
     tr_list          * whitelist;
 
-    char             * sessionId;
-    time_t             sessionIdExpiresAt;
-
     bool               isStreamInitialized;
     z_stream           stream;
 };
@@ -81,33 +79,12 @@ struct tr_rpc_server
 ****
 ***/
 
-static char*
+static const char *
 get_current_session_id (struct tr_rpc_server * server)
 {
-  const time_t now = tr_time ();
-
-  if (!server->sessionId || (now >= server->sessionIdExpiresAt))
-    {
-      int i;
-      const int n = 48;
-      const char * pool = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
-      const size_t pool_size = strlen (pool);
-      unsigned char * buf = tr_new (unsigned char, n+1);
-
-      tr_rand_buffer (buf, n);
-      for (i=0; i<n; ++i)
-        buf[i] = pool[ buf[i] % pool_size ];
-      buf[n] = '\0';
-
-      tr_free (server->sessionId);
-      server->sessionId = (char*) buf;
-      server->sessionIdExpiresAt = now + (60*60); /* expire in an hour */
-    }
-
-  return server->sessionId;
+  return tr_session_id_get_current (server->session->session_id);
 }
 
-
 /**
 ***
 **/
@@ -1004,7 +981,6 @@ closeServer (void * vserver)
   if (s->isStreamInitialized)
     deflateEnd (&s->stream);
   tr_free (s->url);
-  tr_free (s->sessionId);
   tr_free (s->whitelistStr);
   tr_free (s->username);
   tr_free (s->password);

libtransmission/session-id.c

@@ -0,0 +1,74 @@
+/*
+ * This file Copyright (C) 2016 Mnemosyne LLC
+ *
+ * It may be used under the GNU GPL versions 2 or 3
+ * or any future license endorsed by Mnemosyne LLC.
+ *
+ */
+
+#include <string.h>
+#include <time.h>
+
+#include "transmission.h"
+#include "crypto-utils.h"
+#include "session-id.h"
+#include "utils.h"
+
+#define SESSION_ID_SIZE         48
+#define SESSION_ID_DURATION_SEC (60 * 60) /* expire in an hour */
+
+struct tr_session_id
+{
+  char   * current_value;
+  char   * previous_value;
+  time_t   expires_at;
+};
+
+static char *
+generate_new_session_id_value (void)
+{
+  const char   pool[] = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
+  const size_t pool_size = sizeof (pool) - 1;
+
+  char * buf = tr_new (char, SESSION_ID_SIZE + 1);
+
+  tr_rand_buffer (buf, SESSION_ID_SIZE);
+  for (size_t i = 0; i < SESSION_ID_SIZE; ++i)
+    buf[i] = pool[(unsigned char) buf[i] % pool_size];
+  buf[SESSION_ID_SIZE] = '\0';
+
+  return buf;
+}
+
+tr_session_id_t
+tr_session_id_new (void)
+{
+  return tr_new0 (struct tr_session_id, 1);
+}
+
+void
+tr_session_id_free (tr_session_id_t session_id)
+{
+  if (session_id == NULL)
+    return;
+
+  tr_free (session_id->previous_value);
+  tr_free (session_id->current_value);
+  tr_free (session_id);
+}
+
+const char *
+tr_session_id_get_current (tr_session_id_t session_id)
+{
+  const time_t now = tr_time ();
+
+  if (session_id->current_value == NULL || now >= session_id->expires_at)
+    {
+      tr_free (session_id->previous_value);
+      session_id->previous_value = session_id->current_value;
+      session_id->current_value = generate_new_session_id_value ();
+      session_id->expires_at = now + SESSION_ID_DURATION_SEC;
+    }
+
+  return session_id->current_value;
+}

libtransmission/session-id.h

@@ -0,0 +1,43 @@
+/*
+ * This file Copyright (C) 2016 Mnemosyne LLC
+ *
+ * It may be used under the GNU GPL versions 2 or 3
+ * or any future license endorsed by Mnemosyne LLC.
+ *
+ */
+
+#pragma once
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+typedef struct tr_session_id * tr_session_id_t;
+
+/**
+ * Create new session identifier object.
+ *
+ * @return New session identifier object.
+ */
+tr_session_id_t tr_session_id_new (void);
+
+/**
+ * Free session identifier object.
+ *
+ * @param[in] session_id Session identifier object.
+ */
+void tr_session_id_free (tr_session_id_t session_id);
+
+/**
+ * Get current session identifier as string.
+ *
+ * @param[in] session_id Session identifier object.
+ *
+ * @return String representation of current session identifier.
+ */
+const char * tr_session_id_get_current (tr_session_id_t session_id);
+
+#ifdef __cplusplus
+}
+#endif
+

libtransmission/session.c

@@ -45,6 +45,7 @@
 #include "port-forwarding.h"
 #include "rpc-server.h"
 #include "session.h"
+#include "session-id.h"
 #include "stats.h"
 #include "torrent.h"
 #include "tr-dht.h" /* tr_dhtUpkeep () */
@@ -599,6 +600,7 @@ tr_sessionInit (const char * configDir,
   session->lock = tr_lockNew ();
   session->cache = tr_cacheNew (1024*1024*2);
   session->magicNumber = SESSION_MAGIC_NUMBER;
+  session->session_id = tr_session_id_new ();
   tr_bandwidthConstruct (&session->bandwidth, session, NULL);
   tr_variantInitList (&session->removedTorrents, 0);
 
@@ -1955,6 +1957,7 @@ tr_sessionClose (tr_session * session)
   tr_variantFree (&session->removedTorrents);
   tr_bandwidthDestruct (&session->bandwidth);
   tr_bitfieldDestruct (&session->turtle.minutes);
+  tr_session_id_free (session->session_id);
   tr_lockFree (session->lock);
   if (session->metainfoLookup)
     {

libtransmission/session.h

@@ -196,6 +196,7 @@ struct tr_session
 
     struct tr_web *              web;
 
+    struct tr_session_id       * session_id;
     struct tr_rpc_server *       rpcServer;
     tr_rpc_func                  rpc_func;
     void *                       rpc_func_user_data;