Logger: combined key & cipher file

Use one single .ulge file to store both wrapped symmetric key and
encrypted ulog data instead of creating separate .ulgk/ulgc files

src/modules/logger/log_writer_file.cpp

@@ -149,38 +149,17 @@ bool LogWriterFile::init_logfile_encryption(const char *filename)
 	rsa_crypto.close();
 
 	// Write the encrypted key to the disk
-
-	// Allocate a buffer for filename
-	size_t fnlen = strlen(filename);
-	char *tmp_buf = (char *)malloc(fnlen + 1);
-
-	if (!tmp_buf) {
-		PX4_ERR("out of memory");
-		free(key);
-		return false;
-	}
-
-	// Copy the original logfile name, and append 'k' to the filename
-
-	memcpy(tmp_buf, filename, fnlen + 1);
-	tmp_buf[fnlen - 1] = 'k';
-	tmp_buf[fnlen] = 0;
-
-	int key_fd = ::open((const char *)tmp_buf, O_CREAT | O_WRONLY, PX4_O_MODE_666);
-
-	// The file name is no longer needed, free it
-	free(tmp_buf);
-	tmp_buf = nullptr;
+	int key_fd = ::open((const char *)filename, O_CREAT | O_WRONLY | O_DIRECT | O_SYNC, PX4_O_MODE_666);
 
 	if (key_fd < 0) {
 		PX4_ERR("Can't open key file, errno: %d", errno);
 		free(key);
 		return false;
 	}
 
-	// write the header to the key exchange file
+	// write the header to the combined key exchange & cipherdata file
 	struct ulog_key_header_s keyfile_header = {
-		.magic = {'U', 'L', 'o', 'g', 'K', 'e', 'y'},
+		.magic = {'U', 'L', 'o', 'g', 'E', 'n', 'c'},
 		.hdr_ver = 1,
 		.timestamp = hrt_absolute_time(),
 		.exchange_algorithm = CRYPTO_RSA_OAEP,
@@ -651,7 +630,11 @@ size_t LogWriterFile::LogFileBuffer::get_read_ptr(void **ptr, bool *is_part)
 
 bool LogWriterFile::LogFileBuffer::start_log(const char *filename)
 {
+#if defined(PX4_CRYPTO)
+	_fd = ::open(filename, O_APPEND | O_WRONLY, PX4_O_MODE_666);
+#else
 	_fd = ::open(filename, O_CREAT | O_WRONLY, PX4_O_MODE_666);
+#endif
 
 	if (_fd < 0) {
 		PX4_ERR("Can't open log file %s, errno: %d", filename, errno);

src/modules/logger/logger.cpp

@@ -1317,7 +1317,7 @@ int Logger::get_log_file_name(LogType type, char *file_name, size_t file_name_si
 #if defined(PX4_CRYPTO)
 
 	if (_param_sdlog_crypto_algorithm.get() != 0) {
-		crypto_suffix = "c";
+		crypto_suffix = "e";
 	}
 
 #endif