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Merge pull request #1180 from oltaco/shared-secret-on-demand

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Companion: Faster startup by calculating shared_secret on demand
This commit is contained in:
ripplebiz
2025-12-06 18:59:19 +11:00
committed by GitHub
parent d7adcc136b 638f41d143
commit 46f6146df7
4 changed files with 22 additions and 8 deletions
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2
examples/companion_radio/MyMesh.cpp
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@@ -1238,7 +1238,7 @@ void MyMesh::handleCmdFrame(size_t len) {
if (_store->saveMainIdentity(identity)) {
self_id = identity;
writeOKFrame();
// re-load contacts, to recalc shared secrets
// re-load contacts, to invalidate ecdh shared_secrets
resetContacts();
_store->loadContacts(this);
} else {

24
src/helpers/BaseChatMesh.cpp
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@@ -113,8 +113,7 @@ void BaseChatMesh::onAdvertRecv(mesh::Packet* packet, const mesh::Identity& id,
from->gps_lon = 0;
from->sync_since = 0;
// only need to calculate the shared_secret once, for better performance
self_id.calcSharedSecret(from->shared_secret, id);
from->shared_secret_valid = false; // ecdh shared_secret will be calculated later on demand
} else {
MESH_DEBUG_PRINTLN("onAdvertRecv: contacts table is full!");
return;
@@ -147,7 +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) {
// lookup pre-calculated shared_secret
ensureSharedSecretIsValid(contacts[i]);
memcpy(dest_secret, contacts[i].shared_secret, PUB_KEY_SIZE);
} else {
MESH_DEBUG_PRINTLN("getPeerSharedSecret: Invalid peer idx: %d", i);
@@ -293,6 +292,7 @@ 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);
if (rpath) sendDirect(rpath, contact.out_path, contact.out_path_len, 3000); // 3 second delay
}
@@ -342,6 +342,7 @@ 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);
}
@@ -373,6 +374,7 @@ 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);
if (pkt == NULL) return MSG_SEND_FAILED;
@@ -462,6 +464,7 @@ 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);
}
if (pkt) {
@@ -489,6 +492,7 @@ 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);
}
if (pkt) {
@@ -516,6 +520,7 @@ 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));
}
if (pkt) {
@@ -639,6 +644,7 @@ 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);
if (pkt) {
sendDirect(pkt, contact->out_path, contact->out_path_len);
@@ -703,14 +709,20 @@ bool BaseChatMesh::addContact(const ContactInfo& contact) {
auto dest = &contacts[num_contacts++];
*dest = contact;
// calc the ECDH shared secret (just once for performance)
self_id.calcSharedSecret(dest->shared_secret, contact.id);
dest->shared_secret_valid = false; // mark shared_secret as needing calculation
return true; // success
}
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)) {

1
src/helpers/BaseChatMesh.h
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@@ -73,6 +73,7 @@ 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)

3
src/helpers/ContactInfo.h
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@@ -9,9 +9,10 @@ struct ContactInfo {
uint8_t type; // on of ADV_TYPE_*
uint8_t flags;
int8_t out_path_len;
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
uint8_t shared_secret[PUB_KEY_SIZE];
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;