restoring db file blanks file if set to not restore, allow reusing the db

Author: paul-szczepanek-arm

features/FEATURE_BLE/ble/generic/FileSecurityDb.h

@@ -126,6 +126,13 @@ class FileSecurityDb : public SecurityDb {
     virtual SecurityEntryKeys_t* read_in_entry_local_keys(entry_handle_t db_handle);
     virtual SecurityEntrySigning_t* read_in_entry_peer_signing(entry_handle_t db_handle);
 
+    /**
+     * Zero the db file.
+     * @param db_file filehandle for file to erase
+     * @return filehandle when successful, otherwise NULL
+     */
+    static FILE* erase_db_file(FILE* db_file);
+
 private:
     entry_t _entries[MAX_ENTRIES];
     FILE *_db_file;

features/FEATURE_BLE/source/generic/FileSecurityDb.cpp

@@ -75,16 +75,6 @@ typedef SecurityDb::entry_handle_t entry_handle_t;
 FileSecurityDb::FileSecurityDb(FILE *db_file)
     : SecurityDb(),
       _db_file(db_file) {
-    fseek(_db_file, DB_OFFSET_RESTORE, SEEK_SET);
-
-    /* restore if requested */
-    bool restore_toggle;
-    if (fread(&restore_toggle, sizeof(bool), 1, _db_file) == 1) {
-        if (restore_toggle) {
-            restore();
-        }
-    }
-
     /* init the offset in entries so they point to file positions */
     for (size_t i = 0; i < get_entry_count(); i++) {
         _entries[i].file_offset = DB_OFFSET_STORES + i * DB_SIZE_STORE;
@@ -126,24 +116,30 @@ FILE* FileSecurityDb::open_db_file(const char *db_path) {
     }
 
     if (init) {
-        fseek(db_file, 0, SEEK_SET);
-
-        /* zero the file */
-        const uint32_t zero = 0;
-        size_t count = DB_SIZE / 4;
-        while (count--) {
-            if (fwrite(&zero, sizeof(zero), 1, db_file) != 1) {
-                fclose(db_file);
-                return NULL;
-            }
-        }
+        return erase_db_file(db_file);
+    }
+
+    return db_file;
+}
+
+FILE* FileSecurityDb::erase_db_file(FILE* db_file) {
+    fseek(db_file, 0, SEEK_SET);
 
-        if (fflush(db_file)) {
+    /* zero the file */
+    const uint32_t zero = 0;
+    size_t count = DB_SIZE / 4;
+    while (count--) {
+        if (fwrite(&zero, sizeof(zero), 1, db_file) != 1) {
             fclose(db_file);
             return NULL;
         }
     }
 
+    if (fflush(db_file)) {
+        fclose(db_file);
+        return NULL;
+    }
+
     return db_file;
 }
 
@@ -282,6 +278,18 @@ void FileSecurityDb::set_entry_peer_sign_counter(
 /* saving and loading from nvm */
 
 void FileSecurityDb::restore() {
+
+    fseek(_db_file, DB_OFFSET_RESTORE, SEEK_SET);
+
+    /* restore if requested */
+    bool restore_toggle;
+    if (fread(&restore_toggle, sizeof(bool), 1, _db_file) == 1) {
+        if (!restore_toggle) {
+            erase_db_file(_db_file);
+            return;
+        }
+    }
+
     fseek(_db_file, DB_OFFSET_LOCAL_IDENTITY, SEEK_SET);
     fread(&_local_identity, sizeof(_local_identity), 1, _db_file);
 

features/FEATURE_BLE/source/generic/GenericSecurityManager.cpp

@@ -42,20 +42,19 @@ ble_error_t GenericSecurityManager::init(
     bool signing,
     const char* db_path
 ) {
-    if (_db) {
-        return BLE_ERROR_OPERATION_NOT_PERMITTED;
-    }
 
     ble_error_t err = _pal.initialize();
     if (err) {
     	return err;
     }
 
-    FILE* db_file = FileSecurityDb::open_db_file(db_path);
-    if (db_file) {
-        _db = new (std::nothrow) FileSecurityDb(db_file);
-    } else {
-        _db = new (std::nothrow) MemorySecurityDb();
+    if (!_db) {
+        FILE* db_file = FileSecurityDb::open_db_file(db_path);
+        if (db_file) {
+            _db = new (std::nothrow) FileSecurityDb(db_file);
+        } else {
+            _db = new (std::nothrow) MemorySecurityDb();
+        }
     }
 
     _db->restore();