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Fix embedded null byte truncation in ATAK strings

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Fix bug where UIDs, callsigns, and messages containing embedded null
bytes (0x00) are truncated during compression/decompression. The issue
occurs because strlen() stops at the first null byte, but nanopb char
arrays can contain embedded nulls that are valid data.

This causes Android device UIDs like "ANDROID-e7e455b40002429d" to be
truncated to "ANDROID-e7e455b4" (16 chars instead of 24), breaking
direct messages and contact identification.

The fix adds a pb_string_length() helper that scans for the actual
string length by finding the last non-null character, rather than
stopping at the first null.

Added comprehensive unit tests to prevent regressions:
- Normal strings without embedded nulls
- Strings with embedded null bytes
- Empty strings and edge cases
- Android UID pattern testing
- Multiple embedded nulls scenarios

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>
This commit is contained in:
niccellular
2026-02-08 08:54:15 -05:00
co-authored by Claude Sonnet 4.5
parent 7cbab4838c
commit fa5631523e
2 changed files with 285 additions and 30 deletions
Download Patch File Download Diff File Expand all files Collapse all files
src/modules/AtakPluginModule.cpp
+55 -30
View File
@@ -10,6 +10,23 @@
AtakPluginModule *atakPluginModule;
/**
* Get actual string length for nanopb char array fields.
* Nanopb stores strings as fixed-size char arrays that may contain embedded nulls.
* strlen() would stop at the first null, but we need to find the last non-null character.
* This is critical for Android UIDs that can contain 0x00 bytes (e.g., ANDROID-e7e455b40002429d).
*/
static size_t pb_string_length(const char *str, size_t max_len)
{
size_t len = 0;
for (size_t i = 0; i < max_len; i++) {
if (str[i] != '\0') {
len = i + 1;
}
}
return len;
}
AtakPluginModule::AtakPluginModule()
: ProtobufModule("atak", meshtastic_PortNum_ATAK_PLUGIN, &meshtastic_TAKPacket_msg), concurrency::OSThread("AtakPlugin")
{
@@ -70,16 +87,17 @@ void AtakPluginModule::alterReceivedProtobuf(meshtastic_MeshPacket &mp, meshtast
auto compressed = cloneTAKPacketData(t);
compressed.is_compressed = true;
if (t->has_contact) {
auto length = unishox2_compress_lines(t->contact.callsign, strlen(t->contact.callsign), compressed.contact.callsign,
sizeof(compressed.contact.callsign) - 1, USX_PSET_DFLT, NULL);
auto length = unishox2_compress_lines(
t->contact.callsign, pb_string_length(t->contact.callsign, sizeof(t->contact.callsign)),
compressed.contact.callsign, sizeof(compressed.contact.callsign) - 1, USX_PSET_DFLT, NULL);
if (length < 0) {
LOG_WARN("Compress overflow contact.callsign. Revert to uncompressed packet");
return;
}
LOG_DEBUG("Compressed callsign: %d bytes", length);
length = unishox2_compress_lines(t->contact.device_callsign, strlen(t->contact.device_callsign),
compressed.contact.device_callsign, sizeof(compressed.contact.device_callsign) - 1,
USX_PSET_DFLT, NULL);
length = unishox2_compress_lines(
t->contact.device_callsign, pb_string_length(t->contact.device_callsign, sizeof(t->contact.device_callsign)),
compressed.contact.device_callsign, sizeof(compressed.contact.device_callsign) - 1, USX_PSET_DFLT, NULL);
if (length < 0) {
LOG_WARN("Compress overflow contact.device_callsign. Revert to uncompressed packet");
return;
@@ -87,9 +105,11 @@ void AtakPluginModule::alterReceivedProtobuf(meshtastic_MeshPacket &mp, meshtast
LOG_DEBUG("Compressed device_callsign: %d bytes", length);
}
if (t->which_payload_variant == meshtastic_TAKPacket_chat_tag) {
auto length = unishox2_compress_lines(t->payload_variant.chat.message, strlen(t->payload_variant.chat.message),
compressed.payload_variant.chat.message,
sizeof(compressed.payload_variant.chat.message) - 1, USX_PSET_DFLT, NULL);
auto length = unishox2_compress_lines(
t->payload_variant.chat.message,
pb_string_length(t->payload_variant.chat.message, sizeof(t->payload_variant.chat.message)),
compressed.payload_variant.chat.message, sizeof(compressed.payload_variant.chat.message) - 1, USX_PSET_DFLT,
NULL);
if (length < 0) {
LOG_WARN("Compress overflow chat.message. Revert to uncompressed packet");
return;
@@ -98,9 +118,9 @@ void AtakPluginModule::alterReceivedProtobuf(meshtastic_MeshPacket &mp, meshtast
if (t->payload_variant.chat.has_to) {
compressed.payload_variant.chat.has_to = true;
length = unishox2_compress_lines(t->payload_variant.chat.to, strlen(t->payload_variant.chat.to),
compressed.payload_variant.chat.to,
sizeof(compressed.payload_variant.chat.to) - 1, USX_PSET_DFLT, NULL);
length = unishox2_compress_lines(
t->payload_variant.chat.to, pb_string_length(t->payload_variant.chat.to, sizeof(t->payload_variant.chat.to)),
compressed.payload_variant.chat.to, sizeof(compressed.payload_variant.chat.to) - 1, USX_PSET_DFLT, NULL);
if (length < 0) {
LOG_WARN("Compress overflow chat.to. Revert to uncompressed packet");
return;
@@ -110,9 +130,11 @@ void AtakPluginModule::alterReceivedProtobuf(meshtastic_MeshPacket &mp, meshtast
if (t->payload_variant.chat.has_to_callsign) {
compressed.payload_variant.chat.has_to_callsign = true;
length = unishox2_compress_lines(t->payload_variant.chat.to_callsign, strlen(t->payload_variant.chat.to_callsign),
compressed.payload_variant.chat.to_callsign,
sizeof(compressed.payload_variant.chat.to_callsign) - 1, USX_PSET_DFLT, NULL);
length = unishox2_compress_lines(
t->payload_variant.chat.to_callsign,
pb_string_length(t->payload_variant.chat.to_callsign, sizeof(t->payload_variant.chat.to_callsign)),
compressed.payload_variant.chat.to_callsign, sizeof(compressed.payload_variant.chat.to_callsign) - 1,
USX_PSET_DFLT, NULL);
if (length < 0) {
LOG_WARN("Compress overflow chat.to_callsign. Revert to uncompressed packet");
return;
@@ -134,18 +156,18 @@ void AtakPluginModule::alterReceivedProtobuf(meshtastic_MeshPacket &mp, meshtast
auto uncompressed = cloneTAKPacketData(t);
uncompressed.is_compressed = false;
if (t->has_contact) {
auto length =
unishox2_decompress_lines(t->contact.callsign, strlen(t->contact.callsign), uncompressed.contact.callsign,
sizeof(uncompressed.contact.callsign) - 1, USX_PSET_DFLT, NULL);
auto length = unishox2_decompress_lines(
t->contact.callsign, pb_string_length(t->contact.callsign, sizeof(t->contact.callsign)),
uncompressed.contact.callsign, sizeof(uncompressed.contact.callsign) - 1, USX_PSET_DFLT, NULL);
if (length < 0) {
LOG_WARN("Decompress overflow contact.callsign. Bailing out");
return;
}
LOG_DEBUG("Decompressed callsign: %d bytes", length);
length = unishox2_decompress_lines(t->contact.device_callsign, strlen(t->contact.device_callsign),
uncompressed.contact.device_callsign,
sizeof(uncompressed.contact.device_callsign) - 1, USX_PSET_DFLT, NULL);
length = unishox2_decompress_lines(
t->contact.device_callsign, pb_string_length(t->contact.device_callsign, sizeof(t->contact.device_callsign)),
uncompressed.contact.device_callsign, sizeof(uncompressed.contact.device_callsign) - 1, USX_PSET_DFLT, NULL);
if (length < 0) {
LOG_WARN("Decompress overflow contact.device_callsign. Bailing out");
return;
@@ -153,9 +175,11 @@ void AtakPluginModule::alterReceivedProtobuf(meshtastic_MeshPacket &mp, meshtast
LOG_DEBUG("Decompressed device_callsign: %d bytes", length);
}
if (uncompressed.which_payload_variant == meshtastic_TAKPacket_chat_tag) {
auto length = unishox2_decompress_lines(t->payload_variant.chat.message, strlen(t->payload_variant.chat.message),
uncompressed.payload_variant.chat.message,
sizeof(uncompressed.payload_variant.chat.message) - 1, USX_PSET_DFLT, NULL);
auto length = unishox2_decompress_lines(
t->payload_variant.chat.message,
pb_string_length(t->payload_variant.chat.message, sizeof(t->payload_variant.chat.message)),
uncompressed.payload_variant.chat.message, sizeof(uncompressed.payload_variant.chat.message) - 1, USX_PSET_DFLT,
NULL);
if (length < 0) {
LOG_WARN("Decompress overflow chat.message. Bailing out");
return;
@@ -164,9 +188,9 @@ void AtakPluginModule::alterReceivedProtobuf(meshtastic_MeshPacket &mp, meshtast
if (t->payload_variant.chat.has_to) {
uncompressed.payload_variant.chat.has_to = true;
length = unishox2_decompress_lines(t->payload_variant.chat.to, strlen(t->payload_variant.chat.to),
uncompressed.payload_variant.chat.to,
sizeof(uncompressed.payload_variant.chat.to) - 1, USX_PSET_DFLT, NULL);
length = unishox2_decompress_lines(
t->payload_variant.chat.to, pb_string_length(t->payload_variant.chat.to, sizeof(t->payload_variant.chat.to)),
uncompressed.payload_variant.chat.to, sizeof(uncompressed.payload_variant.chat.to) - 1, USX_PSET_DFLT, NULL);
if (length < 0) {
LOG_WARN("Decompress overflow chat.to. Bailing out");
return;
@@ -176,10 +200,11 @@ void AtakPluginModule::alterReceivedProtobuf(meshtastic_MeshPacket &mp, meshtast
if (t->payload_variant.chat.has_to_callsign) {
uncompressed.payload_variant.chat.has_to_callsign = true;
length =
unishox2_decompress_lines(t->payload_variant.chat.to_callsign, strlen(t->payload_variant.chat.to_callsign),
uncompressed.payload_variant.chat.to_callsign,
sizeof(uncompressed.payload_variant.chat.to_callsign) - 1, USX_PSET_DFLT, NULL);
length = unishox2_decompress_lines(
t->payload_variant.chat.to_callsign,
pb_string_length(t->payload_variant.chat.to_callsign, sizeof(t->payload_variant.chat.to_callsign)),
uncompressed.payload_variant.chat.to_callsign, sizeof(uncompressed.payload_variant.chat.to_callsign) - 1,
USX_PSET_DFLT, NULL);
if (length < 0) {
LOG_WARN("Decompress overflow chat.to_callsign. Bailing out");
return;