fix(H7): disable USB BOOTSEL reset path + encrypt secrets at rest

CMakeLists.txt

@@ -123,4 +123,16 @@ target_link_libraries(hslock
 pico_enable_stdio_usb(hslock 1)
 pico_enable_stdio_uart(hslock 0)
 
+# H7 (part A): close the no-firmware-cooperation USB reset-to-BOOTSEL paths.
+# pico_stdio_usb otherwise lets a host drop the chip into the BOOTSEL mass-
+# storage bootloader with `stty ... 1200` or `picotool reboot -u` and then
+# `picotool save` the whole image (every seed + the WiFi password). Disabling
+# both reset interfaces means extraction now requires holding BOOTSEL / SWD,
+# not just the port. (BOOTSEL-on-power-up and SWD remain — see H7 part B for
+# at-rest encryption and the verify-on-hw note.)
+target_compile_definitions(hslock PRIVATE
+    PICO_STDIO_USB_ENABLE_RESET_VIA_BAUD_RATE=0
+    PICO_STDIO_USB_ENABLE_RESET_VIA_VENDOR_INTERFACE=0
+)
+
 pico_add_extra_outputs(hslock)

mbedtls_config.h

@@ -11,4 +11,10 @@
 #define MBEDTLS_SHA1_C
 #define MBEDTLS_MD_C
 
+// H7: at-rest encryption of secrets in storage (AES-256-GCM under a device-bound
+// KEK derived via HMAC-SHA256). GCM needs AES + the cipher layer.
+#define MBEDTLS_AES_C
+#define MBEDTLS_CIPHER_C
+#define MBEDTLS_GCM_C
+
 #endif

serial/commands_system.c

@@ -64,11 +64,13 @@ void cmd_status(int argc, char **argv) {
         printf("ntp:       not synced\r\n");
     }
 
-    // Keys (admin only: key inventory is target-selection data)
+    // Keys (admin only: key inventory is target-selection data). Declared at
+    // function scope so the scrub below always runs, even on the non-admin path
+    // where the array stays zero-initialised.
+    static key_record_t keys[BACKUP_MAX_KEYS];
     if (commands_is_admin()) {
-        static key_record_t keys[BACKUP_MAX_KEYS];
-        int                 count   = storage_key_list(keys, BACKUP_MAX_KEYS);
-        int                 enabled = 0, corrupt = 0;
+        int count   = storage_key_list(keys, BACKUP_MAX_KEYS);
+        int enabled = 0, corrupt = 0;
         for (int i = 0; i < count; i++) {
             if (!keys[i].is_checksum_valid)
                 corrupt++;