* refactor: on-demand getSharedSecret()

Author: Scott Powell

src/helpers/BaseChatMesh.cpp

@@ -146,8 +146,7 @@ int BaseChatMesh::searchPeersByHash(const uint8_t* hash) {
 void BaseChatMesh::getPeerSharedSecret(uint8_t* dest_secret, int peer_idx) {
   int i = matching_peer_indexes[peer_idx];
   if (i >= 0 && i < num_contacts) {
-    ensureSharedSecretIsValid(contacts[i]);
-    memcpy(dest_secret, contacts[i].shared_secret, PUB_KEY_SIZE);
+    memcpy(dest_secret, contacts[i].getSharedSecret(self_id), PUB_KEY_SIZE);
   } else {
     MESH_DEBUG_PRINTLN("getPeerSharedSecret: Invalid peer idx: %d", i);
   }
@@ -292,8 +291,7 @@ void BaseChatMesh::onAckRecv(mesh::Packet* packet, uint32_t ack_crc) {
 void BaseChatMesh::handleReturnPathRetry(const ContactInfo& contact, const uint8_t* path, uint8_t path_len) {
   // NOTE: simplest impl is just to re-send a reciprocal return path to sender (DIRECTLY)
   //        override this method in various firmwares, if there's a better strategy
-  ensureSharedSecretIsValid(contact);
-  mesh::Packet* rpath = createPathReturn(contact.id, contact.shared_secret, path, path_len, 0, NULL, 0);
+  mesh::Packet* rpath = createPathReturn(contact.id, contact.getSharedSecret(self_id), path, path_len, 0, NULL, 0);
   if (rpath) sendDirect(rpath, contact.out_path, contact.out_path_len, 3000);   // 3 second delay
 }
 
@@ -342,8 +340,7 @@ mesh::Packet* BaseChatMesh::composeMsgPacket(const ContactInfo& recipient, uint3
     temp[len++] = attempt;  // hide attempt number at tail end of payload
   }
 
-  ensureSharedSecretIsValid(recipient);
-  return createDatagram(PAYLOAD_TYPE_TXT_MSG, recipient.id, recipient.shared_secret, temp, len);
+  return createDatagram(PAYLOAD_TYPE_TXT_MSG, recipient.id, recipient.getSharedSecret(self_id), temp, len);
 }
 
 int  BaseChatMesh::sendMessage(const ContactInfo& recipient, uint32_t timestamp, uint8_t attempt, const char* text, uint32_t& expected_ack, uint32_t& est_timeout) {
@@ -374,8 +371,7 @@ int  BaseChatMesh::sendCommandData(const ContactInfo& recipient, uint32_t timest
   temp[4] = (attempt & 3) | (TXT_TYPE_CLI_DATA << 2);
   memcpy(&temp[5], text, text_len + 1);
 
-  ensureSharedSecretIsValid(recipient);
-  auto pkt = createDatagram(PAYLOAD_TYPE_TXT_MSG, recipient.id, recipient.shared_secret, temp, 5 + text_len);
+  auto pkt = createDatagram(PAYLOAD_TYPE_TXT_MSG, recipient.id, recipient.getSharedSecret(self_id), temp, 5 + text_len);
   if (pkt == NULL) return MSG_SEND_FAILED;
 
   uint32_t t = _radio->getEstAirtimeFor(pkt->getRawLength());
@@ -464,8 +460,7 @@ int BaseChatMesh::sendLogin(const ContactInfo& recipient, const char* password,
       tlen = 4 + len;
     }
 
-    ensureSharedSecretIsValid(recipient);
-    pkt = createAnonDatagram(PAYLOAD_TYPE_ANON_REQ, self_id, recipient.id, recipient.shared_secret, temp, tlen);
+    pkt = createAnonDatagram(PAYLOAD_TYPE_ANON_REQ, self_id, recipient.id, recipient.getSharedSecret(self_id), temp, tlen);
   }
   if (pkt) {
     uint32_t t = _radio->getEstAirtimeFor(pkt->getRawLength());
@@ -492,8 +487,7 @@ int  BaseChatMesh::sendRequest(const ContactInfo& recipient, const uint8_t* req_
     memcpy(temp, &tag, 4);   // mostly an extra blob to help make packet_hash unique
     memcpy(&temp[4], req_data, data_len);
 
-    ensureSharedSecretIsValid(recipient);
-    pkt = createDatagram(PAYLOAD_TYPE_REQ, recipient.id, recipient.shared_secret, temp, 4 + data_len);
+    pkt = createDatagram(PAYLOAD_TYPE_REQ, recipient.id, recipient.getSharedSecret(self_id), temp, 4 + data_len);
   }
   if (pkt) {
     uint32_t t = _radio->getEstAirtimeFor(pkt->getRawLength());
@@ -520,8 +514,7 @@ int  BaseChatMesh::sendRequest(const ContactInfo& recipient, uint8_t req_type, u
     memset(&temp[5], 0, 4);  // reserved (possibly for 'since' param)
     getRNG()->random(&temp[9], 4);   // random blob to help make packet-hash unique
 
-    ensureSharedSecretIsValid(recipient);
-    pkt = createDatagram(PAYLOAD_TYPE_REQ, recipient.id, recipient.shared_secret, temp, sizeof(temp));
+    pkt = createDatagram(PAYLOAD_TYPE_REQ, recipient.id, recipient.getSharedSecret(self_id), temp, sizeof(temp));
   }
   if (pkt) {
     uint32_t t = _radio->getEstAirtimeFor(pkt->getRawLength());
@@ -644,8 +637,7 @@ void BaseChatMesh::checkConnections() {
       // calc expected ACK reply
       mesh::Utils::sha256((uint8_t *)&connections[i].expected_ack, 4, data, 9, self_id.pub_key, PUB_KEY_SIZE);
 
-      ensureSharedSecretIsValid(*contact);
-      auto pkt = createDatagram(PAYLOAD_TYPE_REQ, contact->id, contact->shared_secret, data, 9);
+      auto pkt = createDatagram(PAYLOAD_TYPE_REQ, contact->id, contact->getSharedSecret(self_id), data, 9);
       if (pkt) {
         sendDirect(pkt, contact->out_path, contact->out_path_len);
       }
@@ -715,14 +707,6 @@ bool BaseChatMesh::addContact(const ContactInfo& contact) {
   return false;
 }
 
-void BaseChatMesh::ensureSharedSecretIsValid(const ContactInfo& contact) {
-  if (contact.shared_secret_valid) {
-    return; // already calculated
-  }
-  self_id.calcSharedSecret(contact.shared_secret, contact.id);
-  contact.shared_secret_valid = true;
-}
-
 bool BaseChatMesh::removeContact(ContactInfo& contact) {
   int idx = 0;
   while (idx < num_contacts && !contacts[idx].id.matches(contact.id)) {

src/helpers/BaseChatMesh.h

@@ -73,7 +73,6 @@ class BaseChatMesh : public mesh::Mesh {
 
   mesh::Packet* composeMsgPacket(const ContactInfo& recipient, uint32_t timestamp, uint8_t attempt, const char *text, uint32_t& expected_ack);
   void sendAckTo(const ContactInfo& dest, uint32_t ack_hash);
-  void ensureSharedSecretIsValid(const ContactInfo& contact);
 
 protected:
   BaseChatMesh(mesh::Radio& radio, mesh::MillisecondClock& ms, mesh::RNG& rng, mesh::RTCClock& rtc, mesh::PacketManager& mgr, mesh::MeshTables& tables)

src/helpers/ContactInfo.h

@@ -12,8 +12,18 @@ struct ContactInfo {
   mutable bool shared_secret_valid; // flag to indicate if shared_secret has been calculated
   uint8_t out_path[MAX_PATH_SIZE];
   uint32_t last_advert_timestamp;   // by THEIR clock
-  mutable uint8_t shared_secret[PUB_KEY_SIZE];
   uint32_t lastmod;  // by OUR clock
   int32_t gps_lat, gps_lon;    // 6 dec places
   uint32_t sync_since;
+
+  const uint8_t* getSharedSecret(const mesh::LocalIdentity& self_id) const {
+    if (!shared_secret_valid) {
+      self_id.calcSharedSecret(shared_secret, id.pub_key);
+      shared_secret_valid = true;
+    }
+    return shared_secret;
+  }
+
+private:
+  mutable uint8_t shared_secret[PUB_KEY_SIZE];
 };