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Fix PKC on portduino sim by working around region blocks keygen and packet length (#10730)

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* Fix PKC on portduino sim by working around region blocks keygen and packet length

* Reserve Compressed framing overhead in sim loopback capacity check

The sim loopback re-encodes the Compressed wrapper back into
decoded.payload.bytes (the same 233-byte field its data is copied from),
so the carried bytes must leave room for protobuf framing. Checking
against sizeof(c.data.bytes) (233) let near-max payloads overflow
pb_encode_to_bytes(), which returns 0 and silently sends an empty
loopback payload. Cap at sizeof(decoded.payload.bytes) minus the
worst-case Compressed framing (meshtastic_Compressed_size - data size)
for both the ciphertext and plaintext paths.

Addresses Copilot review feedback on #10730.

* Potential fix for pull request finding

Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

* Potential fix for pull request finding

Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

* Run trunk fmt

---------

Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>
This commit is contained in:
Ben Meadors
2026-06-17 13:34:29 -05:00
committed by GitHub
co-authored by GitHub Copilot Autofix powered by AI
parent 358e4e2fcd
commit 5ffd30c4a8
3 changed files with 71 additions and 20 deletions
Download Patch File Download Diff File Expand all files Collapse all files
src/mesh/NodeDB.cpp
+9 -2
View File
@@ -3051,8 +3051,15 @@ bool NodeDB::checkLowEntropyPublicKey(const meshtastic_Config_SecurityConfig_pub
bool NodeDB::generateCryptoKeyPair(const uint8_t *privateKey)
{
#if !(MESHTASTIC_EXCLUDE_PKI_KEYGEN || MESHTASTIC_EXCLUDE_PKI)
// Only generate keys for non-licensed users and if LoRa region is set
if (owner.is_licensed || config.lora.region == meshtastic_Config_LoRaConfig_RegionCode_UNSET) {
// Only generate keys for non-licensed users and if the LoRa region is set. The native simulator
// boots region-UNSET but still needs a keypair so PKI-encrypted DMs work between sim nodes, so
// allow keygen there regardless of region.
bool regionBlocksKeygen = config.lora.region == meshtastic_Config_LoRaConfig_RegionCode_UNSET;
#if ARCH_PORTDUINO
if (portduino_config.lora_module == use_simradio)
regionBlocksKeygen = false;
#endif
if (owner.is_licensed || regionBlocksKeygen) {
return false;
}
src/mesh/udp/UdpMulticastHandler.h
+3
View File
@@ -78,6 +78,9 @@ class UdpMulticastHandler final
return;
}
mp.transport_mechanism = meshtastic_MeshPacket_TransportMechanism_TRANSPORT_MULTICAST_UDP;
// Preserve the whole MeshPacket as received: while payload_variant is encrypted, `channel` is a hash (and is 0 for
// PKI DMs), so it must be copied verbatim for the router to attempt PKI/channel decryption. Keep
// pki_encrypted/public_key too so downstream auth/metadata can reflect PKI usage correctly.
UniquePacketPoolPacket p = packetPool.allocUniqueCopy(mp);
// Unset received SNR/RSSI
p->rx_snr = 0;
src/platform/portduino/SimRadio.cpp
+59 -18
View File
@@ -209,16 +209,51 @@ void SimRadio::startSend(meshtastic_MeshPacket *txp)
isReceiving = false;
size_t numbytes = beginSending(txp);
meshtastic_MeshPacket *p = packetPool.allocCopy(*txp);
perhapsDecode(p);
meshtastic_Compressed c = meshtastic_Compressed_init_default;
c.portnum = p->decoded.portnum;
// LOG_DEBUG("Send back to simulator with portNum %d", p->decoded.portnum);
if (p->decoded.payload.size <= sizeof(c.data.bytes)) {
memcpy(&c.data.bytes, p->decoded.payload.bytes, p->decoded.payload.size);
c.data.size = p->decoded.payload.size;
} else {
LOG_WARN("Payload size larger than compressed message allows! Send empty payload");
// A packet we originate that's encrypted for someone else (a PKI DM, channel == 0) can't be
// decrypted here. Attempting it only logs a spurious "no suitable channel" miss, and the
// ciphertext (up to MAX_LORA_PAYLOAD_LEN + MESHTASTIC_PKC_OVERHEAD) overflows the decoded
// loopback payload. Carry such packets as ciphertext instead so the receiving sim node can
// decrypt them as if they had arrived over the air (see unpackAndReceive()).
bool carryEncrypted = p->pki_encrypted;
if (!carryEncrypted) {
perhapsDecode(p);
// Channel packets we couldn't decrypt (e.g. relaying an unknown channel) are carried too.
carryEncrypted = (p->which_payload_variant == meshtastic_MeshPacket_encrypted_tag);
}
meshtastic_Compressed c = meshtastic_Compressed_init_default;
// The Compressed wrapper is re-encoded back into decoded.payload.bytes (the same 233-byte field
// its data is copied from), so the carried bytes must leave room for the protobuf framing or
// pb_encode_to_bytes() below overflows and silently drops the loopback payload. meshtastic_Compressed_size
// is the max encoded size for a full data field, so (meshtastic_Compressed_size - sizeof(c.data.bytes))
// is the worst-case framing overhead to reserve.
constexpr size_t loopbackCapacity = sizeof(p->decoded.payload.bytes) - (meshtastic_Compressed_size - sizeof(c.data.bytes));
if (carryEncrypted) {
// Sentinel portnum UNKNOWN_APP marks the payload as ciphertext for unpackAndReceive().
c.portnum = meshtastic_PortNum_UNKNOWN_APP;
if (p->encrypted.size <= loopbackCapacity) {
memcpy(&c.data.bytes, p->encrypted.bytes, p->encrypted.size);
c.data.size = p->encrypted.size;
} else {
LOG_WARN("Encrypted payload (%u) exceeds sim loopback capacity (%u)! Send empty payload", (unsigned)p->encrypted.size,
(unsigned)loopbackCapacity);
}
} else {
c.portnum = p->decoded.portnum;
// LOG_DEBUG("Send back to simulator with portNum %d", p->decoded.portnum);
if (p->decoded.payload.size <= loopbackCapacity) {
memcpy(&c.data.bytes, p->decoded.payload.bytes, p->decoded.payload.size);
c.data.size = p->decoded.payload.size;
} else {
LOG_WARN("Payload size larger than compressed message allows! Send empty payload");
}
}
// pb_encode_to_bytes writes into decoded.payload, which aliases `encrypted` in the union, so all
// reads of p->encrypted above must be complete before this point.
p->decoded = meshtastic_Data_init_zero;
p->which_payload_variant = meshtastic_MeshPacket_decoded_tag;
p->decoded.payload.size =
pb_encode_to_bytes(p->decoded.payload.bytes, sizeof(p->decoded.payload.bytes), &meshtastic_Compressed_msg, &c);
p->decoded.portnum = meshtastic_PortNum_SIMULATOR_APP;
@@ -233,17 +268,23 @@ void SimRadio::unpackAndReceive(meshtastic_MeshPacket &p)
{
// Simulator packet (=Compressed packet) is encapsulated in a MeshPacket, so need to unwrap first
meshtastic_Compressed scratch;
meshtastic_Compressed *decoded = NULL;
if (p.which_payload_variant == meshtastic_MeshPacket_decoded_tag) {
memset(&scratch, 0, sizeof(scratch));
p.decoded.payload.size =
pb_decode_from_bytes(p.decoded.payload.bytes, p.decoded.payload.size, &meshtastic_Compressed_msg, &scratch);
if (p.decoded.payload.size) {
decoded = &scratch;
// Extract the original payload and replace
memcpy(&p.decoded.payload, &decoded->data, sizeof(decoded->data));
// Switch the port from PortNum_SIMULATOR_APP back to the original PortNum
p.decoded.portnum = decoded->portnum;
if (pb_decode_from_bytes(p.decoded.payload.bytes, p.decoded.payload.size, &meshtastic_Compressed_msg, &scratch)) {
if (scratch.portnum == meshtastic_PortNum_UNKNOWN_APP) {
// The sender carried ciphertext verbatim (a packet it couldn't decrypt, e.g. a PKI DM,
// see startSend()). Restore it as an encrypted packet so the router decrypts it as if
// received over the air, instead of treating the ciphertext as a plaintext payload. The
// outer MeshPacket still carries from/to/id/channel/pki_encrypted, which decrypt needs.
p.which_payload_variant = meshtastic_MeshPacket_encrypted_tag;
memcpy(&p.encrypted.bytes, scratch.data.bytes, scratch.data.size);
p.encrypted.size = scratch.data.size;
} else {
// Extract the original payload and replace
memcpy(&p.decoded.payload, &scratch.data, sizeof(scratch.data));
// Switch the port from PortNum_SIMULATOR_APP back to the original PortNum
p.decoded.portnum = scratch.portnum;
}
} else
LOG_ERROR("Error decoding proto for simulator message!");
}