Make overrideable variables.

The following environment variables are now available to override:

- SOCKET_PATH: defauts to /var/run/hermes.sock
- USER_TOKENS_PATH: defaults to /etc/hermes/ (the trailing slash is
  important)
- STORAGE_DEVICE_PREFIX: defaults to "sd"
- DEVICES_FOLDER: defaults to "/dev/" (the trailing slash is important)

daemon/hermes-daemon.lisp

@@ -2,6 +2,11 @@
 
 (defun main (&rest args)
   (declare (ignore args))
+  (make-overrideable-variables
+   (*socket-path* . "SOCKET_PATH")
+   (*user-tokens-path* . "USER_TOKENS_PATH")
+   (*storage-device-prefix* . "STORAGE_DEVICE_PREFIX")
+   (*devices-folder* . "DEVICES_FOLDER"))
   (loop-with-unix-socket (socket)
     (let ((user-buffer (make-array *max-username-length*
                                    :element-type '(unsigned-byte 8))))

daemon/macros.lisp

@@ -34,3 +34,10 @@
           ;; Don't sleep the last time, it's pointless
         do (unless (= ,i ,tries-max)
              (sleep ,delay-in-seconds)))))
+
+(defmacro make-overrideable-variables (&body alists)
+  `(progn
+     ,@(loop for pair in alists
+          collect (let ((var-name (cdr pair)))
+                    `(when (uiop:getenvp ,var-name)
+                       (setf ,(car pair) (uiop:getenv ,var-name)))))))

daemon/variables.lisp

@@ -8,7 +8,7 @@
 (defvar *user-tokens-path* #p"/etc/hermes/")
 (defvar *storage-device-prefix* "sd")
 (defvar *devices-folder* #p"/dev/")
-(defvar *safe-ott-device-offset* 133)
-(defvar *safe-ott-user-offset* 128)
-(defvar *safe-ott-device-offset* 133)
-(defvar *safe-ott-user-offset* 128)
+(defvar *safe-ott-device-offset* (+ *fingerprint-length* *token-length*))
+(defvar *safe-ott-user-offset* *token-length*)
+(defvar *safe-ott-device-offset* (+ *fingerprint-length* *token-length*))
+(defvar *safe-ott-user-offset* *token-length*)