gptel-gh: Change how tokens are managed

Removed the file based persistent storage of the tokens, as they were
stored in clear text. They will only be stored in variables.

The initial value of the github-token can now be set by providing a
function that provides it. This enables this token to be securely
stored outside of Emacs.

Author: marcus-lundgren

gptel-gh.el

@@ -164,26 +164,17 @@
 (cl-defstruct (gptel--gh (:include gptel-openai)
                          (:copier nil)
                          (:constructor gptel--make-gh))
-  token github-token sessionid machineid)
-
-(defcustom gptel-gh-github-token-file (expand-file-name ".cache/copilot-chat/github-token"
-                                                        user-emacs-directory)
-  "File where the GitHub token is stored."
-  :type 'string
-  :group 'gptel)
-
-(defcustom gptel-gh-token-file (expand-file-name ".cache/copilot-chat/token"
-                                                 user-emacs-directory)
-  "File where the chat token is cached."
-  :type 'string
-  :group 'gptel)
+  sessionid machineid)
 
 (defconst gptel--gh-auth-common-headers
   `(("editor-plugin-version" . "gptel/*")
     ("editor-version" . ,(concat "emacs/" emacs-version))))
 
 (defconst gptel--gh-client-id "Iv1.b507a08c87ecfe98")
 
+(defvar gptel--gh-token nil)
+(defvar gptel--gh-github-token nil)
+
 ;; https://en.wikipedia.org/wiki/Universally_unique_identifier#Version_4_(random)
 (defun gptel--gh-uuid ()
   "Generate a UUID v4-1."
@@ -203,26 +194,10 @@
       (setq hex (nconc hex (list (aref hex-chars (random 16))))))
     (apply #'string hex)))
 
-(defun gptel--gh-restore (file)
-  "Restore saved object from FILE."
-  (when (file-exists-p file)
-    ;; We set the coding system to `utf-8-auto-dos' when reading so that
-    ;; files with CR EOL can still be read properly
-    (let ((coding-system-for-read 'utf-8-auto-dos))
-      (with-temp-buffer
-        (set-buffer-multibyte nil)
-        (insert-file-contents-literally file)
-        (goto-char (point-min))
-        (read (current-buffer))))))
-
-(defun gptel--gh-save (file obj)
+(defun gptel--gh-save (obj)
   "Save OBJ to FILE."
-  (let ((print-length nil)
-        (print-level nil)
-        (coding-system-for-write 'utf-8-unix))
-    (make-directory (file-name-directory file) t)
-    (write-region (prin1-to-string obj) nil file nil :silent)
-    obj))
+  (message "New GitHub token: %s" (prin1-to-string obj))
+  (setq gptel--gh-github-token obj))
 
 (defun gptel-gh-login ()
   "Login to GitHub Copilot API.
@@ -254,13 +229,11 @@ If your browser does not open automatically, browse to %s."
                   :device_code ,device_code
                   :grant_type "urn:ietf:params:oauth:grant-type:device_code"))
        :access_token)
-      (gptel--gh-save gptel-gh-github-token-file)
-      (setf (gptel--gh-github-token gptel-backend))))
-  (if (and (gptel--gh-github-token gptel-backend)
-           (not (string-empty-p
-                 (gptel--gh-github-token gptel-backend))))
-      (message "Successfully logged in to GitHub Copilot")
-    (user-error "Error: You might not have access to GitHub Copilot Chat!")))
+      (gptel--gh-save))
+    (if (and gptel--gh-github-token
+             (not (string-empty-p gptel--gh-github-token)))
+        (message "Successfully logged in to GitHub Copilot")
+      (user-error "Error: You might not have access to GitHub Copilot Chat!"))))
 
 (defun gptel--gh-renew-token ()
   "Renew session token."
@@ -269,34 +242,22 @@ If your browser does not open automatically, browse to %s."
              "https://api.github.com/copilot_internal/v2/token"
            :method 'get
            :headers `(("authorization"
-                       . ,(format "token %s" (gptel--gh-github-token gptel-backend)))
+                       . ,(format "token %s" gptel--gh-github-token))
                       ,@gptel--gh-auth-common-headers))))
     (if (not (plist-get token :token))
-        (progn
-          (setf (gptel--gh-github-token gptel-backend) nil)
-          (user-error "Error: You might not have access to GitHub Copilot Chat!"))
-      (thread-last
-        (gptel--gh-save gptel-gh-token-file token)
-        (setf (gptel--gh-token gptel-backend))))))
+        (user-error "Error: You might not have access to GitHub Copilot Chat!")
+      (setq gptel--gh-token token))))
 
 (defun gptel--gh-auth ()
   "Authenticate with GitHub Copilot API.
 
 We first need github authorization (github token).
 Then we need a session token."
-  (unless (gptel--gh-github-token gptel-backend)
-    (let ((token (gptel--gh-restore gptel-gh-github-token-file)))
-      (if token
-          (setf (gptel--gh-github-token gptel-backend) token)
-        (gptel-gh-login))))
-
-  (when (null (gptel--gh-token gptel-backend))
-    ;; try to load token from `gptel-gh-token-file'
-    (setf (gptel--gh-token gptel-backend)
-          (gptel--gh-restore gptel-gh-token-file)))
+  (unless gptel--gh-github-token
+    (gptel-gh-login))
 
   (pcase-let (((map :token :expires_at)
-               (gptel--gh-token gptel-backend)))
+               gptel--gh-token))
     (when (or (null token)
               (and expires_at
                    (> (round (float-time (current-time)))
@@ -309,8 +270,7 @@ Then we need a session token."
           (header (lambda ()
                     (gptel--gh-auth)
                     `(("openai-intent" . "conversation-panel")
-                      ("authorization" . ,(concat "Bearer "
-                                           (plist-get (gptel--gh-token gptel-backend) :token)))
+                      ("authorization" . ,(concat "Bearer " (plist-get gptel--gh-token :token)))
                       ("x-request-id" . ,(gptel--gh-uuid))
                       ("vscode-sessionid" . ,(or (gptel--gh-sessionid gptel-backend) ""))
                       ("vscode-machineid" . ,(or (gptel--gh-machineid gptel-backend) ""))
@@ -322,7 +282,8 @@ Then we need a session token."
           (protocol "https")
           (endpoint "/chat/completions")
           (stream t)
-          (models gptel--gh-models))
+          (models gptel--gh-models)
+          (github-token-init nil))
   "Register a Github Copilot chat backend for gptel with NAME.
 
 Keyword arguments:
@@ -374,6 +335,9 @@ parameters (as plist keys) and values supported by the API.  Use
 these to set parameters that gptel does not provide user options
 for."
   (declare (indent 1))
+  (if (and (not gptel--gh-github-token)
+           github-token-init)
+      (gptel--gh-save (funcall github-token-init)))
   (let ((backend (gptel--make-gh
                   :name name
                   :host host