From 6b8379668ac9ef4b0bdd8240f2539b5aa3056ad3 Mon Sep 17 00:00:00 2001
From: t3sserakt <t3ss@posteo.de>
Date: Wed, 22 Jan 2020 21:39:00 +0100
Subject: [PATCH] added signing of monotonic time

---
 src/cadet/gnunet-service-cadet_connection.c | 23 ++++++++++++++++++++
 src/cadet/gnunet-service-cadet_core.c       | 24 ++++++++++++++++++++-
 src/include/gnunet_signatures.h             |  4 ++++
 3 files changed, 50 insertions(+), 1 deletion(-)

diff --git a/src/cadet/gnunet-service-cadet_connection.c b/src/cadet/gnunet-service-cadet_connection.c
index a6c3e51d4..1e0f82579 100644
--- a/src/cadet/gnunet-service-cadet_connection.c
+++ b/src/cadet/gnunet-service-cadet_connection.c
@@ -78,6 +78,29 @@ enum CadetConnectionState
   CADET_CONNECTION_READY
 };
 
+struct CadetConnectionCreatePS
+{
+
+  /**
+   * Purpose is #GNUNET_SIGNATURE_PURPOSE_CADET_CONNECTION_INITIATOR
+   */
+  struct GNUNET_CRYPTO_EccSignaturePurpose purpose;
+
+  /**
+   * Time at the initiator when generating the signature.
+   *
+   * Note that the receiver MUST IGNORE the absolute time, and only interpret
+   * the value as a mononic time and reject "older" values than the last one
+   * observed.  This is necessary as we do not want to require synchronized
+   * clocks and may not have a bidirectional communication channel.
+   *
+   * Even with this, there is no real guarantee against replay achieved here,
+   * unless the latest timestamp is persisted.  Persistence should be
+   * provided via PEERSTORE if possible.
+   */
+  struct GNUNET_TIME_AbsoluteNBO monotonic_time;
+
+}
 
 /**
  * Low-level connection to a destination.
diff --git a/src/cadet/gnunet-service-cadet_core.c b/src/cadet/gnunet-service-cadet_core.c
index 7fc131114..4cc29782e 100644
--- a/src/cadet/gnunet-service-cadet_core.c
+++ b/src/cadet/gnunet-service-cadet_core.c
@@ -227,6 +227,28 @@ static unsigned long long cur_buffers;
  */
 static struct GNUNET_SCHEDULER_Task *timeout_task;
 
+static int
+check_monotime_sig (struc GNUNET_PeerIdentity *pid,
+                    const struct GNUNET_CADET_ConnectionCreateMessage *msg)
+{
+
+  struct CCCreatePS cp = { .purpose.purpose = htonl (
+                           GNUNET_SIGNATURE_PURPOSE_CADET_CONNECTION_INITIATOR),
+                         .purpose.size = htonl (sizeof(cp)),
+                         .monotonic_time = sender_monotonic_time};
+
+  if (
+    GNUNET_OK !=
+    GNUNET_CRYPTO_eddsa_verify (GNUNET_SIGNATURE_PURPOSE_CADET_CONNECTION_INITIATOR,
+                                &cp.purpose,
+                                msg->monotime_sig,
+                                &pid->public_key))
+  {
+    GNUNET_break_op (0);
+    return GNUNET_SYSERR;
+  }
+  return GNUNET_OK;
+}
 
 /**
  * Get the route corresponding to a hash.
@@ -826,7 +848,7 @@ handle_connection_create (
     t = GCP_get_tunnel (sender, GNUNET_YES);
 
     // Check for CADET state in case the other side has lost the tunnel (xrs,t3ss)
-    if ((NULL != msg->monotime) && check_monotime_sig(msg)
+    if ((NULL != msg->monotime) && GNUNET_OK == check_monotime_sig(origin->pid, &msg)
         (CADET_TUNNEL_KEY_OK == GCT_get_estate(t)))
     {
       GCT_change_estate (t, CADET_TUNNEL_KEY_UNINITIALIZED);
diff --git a/src/include/gnunet_signatures.h b/src/include/gnunet_signatures.h
index a00e0372d..503113770 100644
--- a/src/include/gnunet_signatures.h
+++ b/src/include/gnunet_signatures.h
@@ -241,6 +241,10 @@ extern "C"
  */
 #define GNUNET_SIGNATURE_PURPOSE_TRANSPORT_DV_INITIATOR 37
 
+/**
+ * Signature by a peer that like to create a connection.
+ */
+#define GNUNET_SIGNATURE_PURPOSE_CADET_CONNECTION_INITIATOR 38
 
 #if 0                           /* keep Emacsens' auto-indent happy */
 {
-- 
2.25.1