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fix: stop unexpected NodeNum regeneration from PKI key loss (#10808)

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* fix: stop unexpected NodeNum regeneration from PKI key loss

A node's NodeNum is derived from its PKI public key
(my_node_num == crc32(public_key)), so it changes only when the keypair is
regenerated -- which happens only when a keygen path runs while
config.security.private_key.size != 32. Two paths could trigger that without
the user intending a new identity:

1. Boot: loadFromDisk() collapsed every non-success loadProto() result for the
   config file into installDefaultConfig() (preserveKey=false), which memset()s
   config and wipes the private key. loadProto() distinguishes DECODE_FAILED
   (file present but undecodable/undecryptable) from OTHER_FAILURE (absent), so
   a transient/corrupt read silently minted a new identity. A new
   configDecodeFailed flag now gates the boot keygen and the boot config-save
   directly (not via region, so it survives the userprefs/region overrides that
   run later in loadFromDisk): identity is frozen, the unreadable file is left
   intact for a later clean boot to recover, and the node boots radio-silent
   (region UNSET, TX off). A genuinely-absent config still gets defaults + keygen.

2. AdminModule security SET: config.security = c.payload_variant.security
   wholesale-clobbered the keypair, then regenerated whenever the incoming
   private_key.size != 32. A client editing an unrelated security field without
   round-tripping the private key would re-mint identity. The existing keypair
   is now preserved when the incoming config omits it; first provisioning and
   key import are unchanged. Intentional reset goes through factory_reset.

Native PlatformIO unit suite (Docker): 499/499 test cases pass.

* test: cover security keypair preservation; clarify load-failure comment

Addresses PR review feedback:
- Add native unit tests (test_admin_radio) asserting handleSetConfig preserves the
  existing identity keypair when a security SET omits the private key, and applies a
  full supplied keypair (key import). Guards against reintroduced NodeNum/keypair
  regeneration. AdminModuleTestShim (now a friend) defers saves so the lightweight
  harness doesn't saveToDisk an uninitialized node database.
- Clarify the non-DECODE_FAILED config-load comment: OTHER_FAILURE / NO_FILESYSTEM
  cover an absent or unopenable file, not just first boot.
This commit is contained in:
Ben Meadors
2026-06-28 18:48:24 -05:00
committed by GitHub
co-authored by GitHub
parent 9cef69a9d3
commit 0488a46a3c
5 changed files with 114 additions and 18 deletions
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src/mesh/NodeDB.cpp
+30 -12
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@@ -480,8 +480,10 @@ NodeDB::NodeDB()
#if !(MESHTASTIC_EXCLUDE_PKI_KEYGEN || MESHTASTIC_EXCLUDE_PKI)
// Generate crypto keys if needed using consolidated function
// Set my node num uint32 value to bytes from the public key (if we have one)
// Generate identity and crypto keys if needed; this will create a new identity if one does not exist
generateCryptoKeyPair(nullptr);
// Generate identity and crypto keys if needed; this will create a new identity if one does not exist.
// Skip on a degraded boot: the keypair isn't in RAM, so minting one would change our NodeNum.
if (!configDecodeFailed)
generateCryptoKeyPair(nullptr);
#elif !(MESHTASTIC_EXCLUDE_PKI)
// Calculate Curve25519 public and private keys
if (config.security.private_key.size == 32 && config.security.public_key.size == 32) {
@@ -625,7 +627,9 @@ NodeDB::NodeDB()
saveWhat |= SEGMENT_DEVICESTATE;
if (nodeDatabaseCRC != crc32Buffer(&nodeDatabase, sizeof(nodeDatabase)))
saveWhat |= SEGMENT_NODEDATABASE;
if (configCRC != crc32Buffer(&config, sizeof(config)))
// Don't persist on a degraded boot: it would overwrite the unreadable-but-maybe-transient config file
// with no-key UNSET defaults. Runtime reconfiguration (admin set) still persists normally.
if (!configDecodeFailed && configCRC != crc32Buffer(&config, sizeof(config)))
saveWhat |= SEGMENT_CONFIG;
if (channelFileCRC != crc32Buffer(&channelFile, sizeof(channelFile)))
saveWhat |= SEGMENT_CHANNELS;
@@ -2120,6 +2124,7 @@ void NodeDB::loadFromDisk()
#endif
migrationSavePending = false;
configDecodeFailed = false;
meshtastic_Config_SecurityConfig backupSecurity = meshtastic_Config_SecurityConfig_init_zero;
@@ -2309,15 +2314,26 @@ void NodeDB::loadFromDisk()
state = loadProto(configFileName, meshtastic_LocalConfig_size, sizeof(meshtastic_LocalConfig), &meshtastic_LocalConfig_msg,
&config);
if (state != LoadFileResult::LOAD_SUCCESS) {
installDefaultConfig(); // Our in RAM copy might now be corrupt
if (state == LoadFileResult::DECODE_FAILED) {
// Config file present but undecodable this boot (corruption / torn write / transient decrypt fail).
// loadProto() already zeroed `config`, so the keypair is gone from RAM; minting a new one would change
// our NodeNum (== crc32(public_key)) and orphan us on the mesh. configDecodeFailed freezes identity and
// skips persisting (see ctor), so a transient failure self-heals on the next clean boot. A genuinely
// absent config returns OTHER_FAILURE, so this never fires on first boot. Boot degraded + radio-silent.
LOG_ERROR("Config decode failed - freezing identity, booting degraded (radio silent until restored)");
configDecodeFailed = true;
installDefaultConfig(true);
config.lora.region = meshtastic_Config_LoRaConfig_RegionCode_UNSET;
config.lora.tx_enabled = false;
} else if (state != LoadFileResult::LOAD_SUCCESS) {
// No decodable config to work with: the file is absent (first boot) or could not be opened (OTHER_FAILURE
// / NO_FILESYSTEM). Unlike DECODE_FAILED there are no usable contents to protect, so install defaults.
installDefaultConfig();
} else if (config.version < DEVICESTATE_MIN_VER) {
LOG_WARN("config %d is old, discard", config.version);
installDefaultConfig(true);
} else {
if (config.version < DEVICESTATE_MIN_VER) {
LOG_WARN("config %d is old, discard", config.version);
installDefaultConfig(true);
} else {
LOG_INFO("Loaded saved config version %d", config.version);
}
LOG_INFO("Loaded saved config version %d", config.version);
}
// Coerce LoRa config fields derived from presets while bootstrapping.
@@ -2334,7 +2350,9 @@ void NodeDB::loadFromDisk()
// take effect even when NVS already has a valid config (e.g. region-locked
// dev boards with no BLE/serial to set the region at runtime).
#ifdef USERPREFS_CONFIG_LORA_REGION
config.lora.region = USERPREFS_CONFIG_LORA_REGION;
// Skip on a degraded boot to keep the radio silent (identity is already protected by the keygen gate).
if (!configDecodeFailed)
config.lora.region = USERPREFS_CONFIG_LORA_REGION;
#endif
#ifdef USERPREFS_LORACONFIG_USE_PRESET