Store channel filter config in binary, drop the PSK string array

Keys are never displayed (filter list shows counts only), so persist the
decoded GroupChannel directly instead of the original PSK string. Removes
the 272-byte filter_channel_psk[] buffer and the base64/hex round-trip;
config file is now a versioned binary blob.

Co-Authored-By: Claude Opus 4.8 <[email protected]>

examples/simple_repeater/MyMesh.cpp

@@ -696,7 +696,6 @@ bool MyMesh::addFilterChannel(const char *psk) {
   if (len != 16 && len != 32) return false;
 
   mesh::Utils::sha256(ch->hash, sizeof(ch->hash), ch->secret, len);
-  StrHelper::strncpy(filter_channel_psk[num_filter_channels], psk, FILTER_PSK_LEN);
   num_filter_channels++;
   return true;
 }
@@ -781,32 +780,64 @@ void MyMesh::loadChannelFilter() {
 #endif
   if (!f) return;
 
-  char line[FILTER_PSK_LEN + 8];
-  while (f.available()) {
-    int n = f.readBytesUntil('\n', (uint8_t *)line, sizeof(line) - 1);
-    line[n] = 0;
-    while (n > 0 && (line[n - 1] == '\r' || line[n - 1] == ' ')) line[--n] = 0;
-    if (n < 3 || line[1] != ' ') continue;
-
-    const char *val = &line[2];
-    if (line[0] == 'C') {
-      addFilterChannel(val);
-    } else if (line[0] == 'K' && num_block_keywords < MAX_FILTER_TERMS) {
-      StrHelper::strncpy(block_keywords[num_block_keywords++], val, FILTER_TERM_LEN);
-    } else if (line[0] == 'S' && num_block_senders < MAX_FILTER_TERMS) {
-      StrHelper::strncpy(block_senders[num_block_senders++], val, FILTER_TERM_LEN);
-    }
+  if (f.read() != CHANNEL_FILTER_FMT) { f.close(); return; }  // unknown/legacy file -> start empty
+
+  int n = f.read();
+  if (n < 0 || n > MAX_FILTER_CHANNELS) { f.close(); return; }
+  for (int i = 0; i < n; i++) {
+    auto ch = &filter_channels[num_filter_channels];
+    if (f.readBytes((char *)ch->hash, sizeof(ch->hash)) != sizeof(ch->hash)) break;
+    if (f.readBytes((char *)ch->secret, sizeof(ch->secret)) != sizeof(ch->secret)) break;
+    num_filter_channels++;
+  }
+
+  n = f.read();
+  if (n < 0 || n > MAX_FILTER_TERMS) { f.close(); return; }
+  for (int i = 0; i < n; i++) {
+    int l = f.read();
+    if (l < 0 || l >= FILTER_TERM_LEN) break;
+    if (f.readBytes(block_keywords[num_block_keywords], l) != (size_t)l) break;
+    block_keywords[num_block_keywords][l] = 0;
+    num_block_keywords++;
+  }
+
+  n = f.read();
+  if (n < 0 || n > MAX_FILTER_TERMS) { f.close(); return; }
+  for (int i = 0; i < n; i++) {
+    int l = f.read();
+    if (l < 0 || l >= FILTER_TERM_LEN) break;
+    if (f.readBytes(block_senders[num_block_senders], l) != (size_t)l) break;
+    block_senders[num_block_senders][l] = 0;
+    num_block_senders++;
   }
   f.close();
 }
 
+// Binary layout: [fmt][n_chan]{hash[1] secret[32]}*  [n_kw]{len text}*  [n_snd]{len text}*
+// Channel keys are never displayed, so the decoded GroupChannel is stored directly
+// rather than the original PSK string.
 void MyMesh::saveChannelFilter() {
   _fs->remove(CHANNEL_FILTER_FILE);
   File f = openAppend(CHANNEL_FILTER_FILE);
   if (!f) return;
-  for (int i = 0; i < num_filter_channels; i++) f.printf("C %s\n", filter_channel_psk[i]);
-  for (int i = 0; i < num_block_keywords; i++) f.printf("K %s\n", block_keywords[i]);
-  for (int i = 0; i < num_block_senders; i++) f.printf("S %s\n", block_senders[i]);
+  f.write((uint8_t)CHANNEL_FILTER_FMT);
+  f.write((uint8_t)num_filter_channels);
+  for (int i = 0; i < num_filter_channels; i++) {
+    f.write(filter_channels[i].hash, sizeof(filter_channels[i].hash));
+    f.write(filter_channels[i].secret, sizeof(filter_channels[i].secret));
+  }
+  f.write((uint8_t)num_block_keywords);
+  for (int i = 0; i < num_block_keywords; i++) {
+    uint8_t l = strlen(block_keywords[i]);
+    f.write(l);
+    f.write((const uint8_t *)block_keywords[i], l);
+  }
+  f.write((uint8_t)num_block_senders);
+  for (int i = 0; i < num_block_senders; i++) {
+    uint8_t l = strlen(block_senders[i]);
+    f.write(l);
+    f.write((const uint8_t *)block_senders[i], l);
+  }
   f.close();
 }
 

examples/simple_repeater/MyMesh.h

@@ -90,7 +90,7 @@ struct NeighbourInfo {
   #define MAX_FILTER_TERMS  8
 #endif
 #define FILTER_TERM_LEN     24
-#define FILTER_PSK_LEN      68   // fits a 64-char hex key, a 44-char base64 PSK, or "public"
+#define CHANNEL_FILTER_FMT  1   // on-disk format version for CHANNEL_FILTER_FILE
 #endif
 
 class MyMesh : public mesh::Mesh, public CommonCLICallbacks {
@@ -129,7 +129,6 @@ class MyMesh : public mesh::Mesh, public CommonCLICallbacks {
 
 #ifdef WITH_CHANNEL_FILTER
   mesh::GroupChannel filter_channels[MAX_FILTER_CHANNELS];
-  char filter_channel_psk[MAX_FILTER_CHANNELS][FILTER_PSK_LEN];
   uint8_t num_filter_channels;
   char block_keywords[MAX_FILTER_TERMS][FILTER_TERM_LEN];
   uint8_t num_block_keywords;