shade/MeshCore-Posadmesh
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

fix(prefs): stop reading misaligned tail into later prefs fields

Browse Source 
loadPrefsInt guarded each EastMesh field with its own available() check
and no bail-out. On a short prefs file that skipped a large field but
still satisfied a later, smaller one: with 8 bytes left, bridge_peer_host
(64) was correctly skipped, then bridge_peer_port (2) passed its guard
and read two misaligned bytes. It has no constrain(), so it loaded 0
instead of its 1883 default.

Read sequentially and stop at the first field that isn't fully present,
leaving the rest at their constructor defaults.

This does not make a differently-laid-out prefs file safe to read, only a
shorter one -- fan_mode and fan_timeout_secs still take whatever bytes sit
at 512..514. A format marker on the EastMesh block would close that.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
This commit is contained in:
Jared Dohrman
2026-07-10 20:23:58 +10:00
co-authored by Claude Opus 4.8
parent b9006d14dd
commit 54a167f60f
1 changed files with 18 additions and 19 deletions
Download Patch File Download Diff File Expand all files Collapse all files
src/helpers/CommonCLI.cpp
+18 -19
View File
@@ -60,6 +60,14 @@ static void skipPrefsGap(File& file, int num_bytes) {
}
}
// Callers must stop at the first false: once a field is missing, everything after it is
// misaligned, and a short tail would otherwise still satisfy a later, smaller field.
static bool readPrefsField(File& file, void* dst, size_t len) {
if (file.available() < (int)len) return false;
file.read((uint8_t *)dst, len);
return true;
}
void CommonCLI::loadPrefs(FILESYSTEM* fs) {
if (fs->exists("/com_prefs")) {
loadPrefsInt(fs, "/com_prefs"); // new filename
@@ -130,25 +138,16 @@ void CommonCLI::loadPrefsInt(FILESYSTEM* fs, const char* filename) {
skipPrefsGap(file, PREFS_EASTMESH_BASE - PREFS_UPSTREAM_END); // reserved for upstream growth
// EastMesh-only fields, based at PREFS_EASTMESH_BASE
if (file.available() >= (int)sizeof(_prefs->fan_mode)) {
file.read((uint8_t *)&_prefs->fan_mode, sizeof(_prefs->fan_mode)); // 512
}
if (file.available() >= (int)sizeof(_prefs->fan_timeout_secs)) {
file.read((uint8_t *)&_prefs->fan_timeout_secs, sizeof(_prefs->fan_timeout_secs)); // 513
}
if (file.available() >= (int)sizeof(_prefs->bridge_peer_host)) {
file.read((uint8_t *)&_prefs->bridge_peer_host, sizeof(_prefs->bridge_peer_host)); // 515
}
if (file.available() >= (int)sizeof(_prefs->bridge_peer_port)) {
file.read((uint8_t *)&_prefs->bridge_peer_port, sizeof(_prefs->bridge_peer_port)); // 579
}
if (file.available() >= (int)sizeof(_prefs->bridge_peer_username)) {
file.read((uint8_t *)&_prefs->bridge_peer_username, sizeof(_prefs->bridge_peer_username)); // 581
}
if (file.available() >= (int)sizeof(_prefs->bridge_peer_password)) {
file.read((uint8_t *)&_prefs->bridge_peer_password, sizeof(_prefs->bridge_peer_password)); // 646
}
// EastMesh-only fields, based at PREFS_EASTMESH_BASE. An older prefs file simply ends
// early, so read until the first field that isn't fully present and leave the rest at
// their constructor defaults.
bool ok = true;
ok = ok && readPrefsField(file, &_prefs->fan_mode, sizeof(_prefs->fan_mode)); // 512
ok = ok && readPrefsField(file, &_prefs->fan_timeout_secs, sizeof(_prefs->fan_timeout_secs)); // 513
ok = ok && readPrefsField(file, _prefs->bridge_peer_host, sizeof(_prefs->bridge_peer_host)); // 515
ok = ok && readPrefsField(file, &_prefs->bridge_peer_port, sizeof(_prefs->bridge_peer_port)); // 579
ok = ok && readPrefsField(file, _prefs->bridge_peer_username, sizeof(_prefs->bridge_peer_username)); // 581
ok = ok && readPrefsField(file, _prefs->bridge_peer_password, sizeof(_prefs->bridge_peer_password)); // 646
// next: 742
// sanitise bad pref values