bug#71969: [PATCH] Support interactive D-Bus authentication

[Steven Allen via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>]

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When invoking D-Bus methods, let the user enable interactive
authorization by passing an :authenticate t parameter.  This makes it
possible to D-Bus methods that require polkit authorization.

Alternatively, we could allow interactive authorization unconditionally,
but I'd prefer to leave it up to the caller.


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From fa996a3363e9bcefb547c2a587d55b279d44c5dd Mon Sep 17 00:00:00 2001
From: Steven Allen <steven@stebalien.com>
Date: Thu, 4 Jul 2024 20:45:07 +0200
Subject: [PATCH] Support interactive D-Bus authentication

When invoking D-Bus methods, let the user enable interactive
authorization by passing an :authenticate t parameter.  This makes it
possible to D-Bus methods that require polkit authorization.

* src/dbusbind.c (dbus-message-internal): Allow interactive
authorization by passing :authenticate t.
* lisp/net/dbus.el (dbus-call-method-asynchronously): Document the new
parameter.
* doc/misc/dbus.texi (Synchronous Methods, Asynchronous Methods):
Document the new parameter.
---
 doc/misc/dbus.texi | 12 ++++++++++--
 etc/NEWS           |  6 ++++++
 lisp/net/dbus.el   |  8 ++++++++
 src/dbusbind.c     | 26 ++++++++++++++++++++------
 4 files changed, 44 insertions(+), 8 deletions(-)

diff --git a/doc/misc/dbus.texi b/doc/misc/dbus.texi
index e5d867acd40..9bde8cbc76b 100644
--- a/doc/misc/dbus.texi
+++ b/doc/misc/dbus.texi
@@ -1208,7 +1208,7 @@ Synchronous Methods
 be called, and a reply message returning the resulting output
 parameters from the object.
 
-@defun dbus-call-method bus service path interface method &optional :timeout timeout &rest args
+@defun dbus-call-method bus service path interface method &optional :timeout timeout :authenticate auth &rest args
 @anchor{dbus-call-method}
 This function calls @var{method} on the D-Bus @var{bus}.  @var{bus} is
 either the keyword @code{:system} or the keyword @code{:session}.
@@ -1223,6 +1223,10 @@ Synchronous Methods
 call doesn't return in time, a D-Bus error is raised (@pxref{Errors
 and Events}).
 
+If the parameter @code{:authenticate} is given and the following
+@var{auth} is non-nil, the invoked method may interactively prompt the
+user for authorization.  The default is @code{nil}.
+
 The remaining arguments @var{args} are passed to @var{method} as
 arguments.  They are converted into D-Bus types as described in
 @ref{Type Conversion}.
@@ -1302,7 +1306,7 @@ Asynchronous Methods
 @cindex method calls, asynchronous
 @cindex asynchronous method calls
 
-@defun dbus-call-method-asynchronously bus service path interface method handler &optional :timeout timeout &rest args
+@defun dbus-call-method-asynchronously bus service path interface method handler &optional :timeout timeout :authenticate auth &rest args
 This function calls @var{method} on the D-Bus @var{bus}
 asynchronously.  @var{bus} is either the keyword @code{:system} or the
 keyword @code{:session}.
@@ -1321,6 +1325,10 @@ Asynchronous Methods
 no reply message in time, a D-Bus error is raised (@pxref{Errors and
 Events}).
 
+If the parameter @code{:authenticate} is given and the following
+@var{auth} is non-nil, the invoked method may interactively prompt the
+user for authorization.  The default is @code{nil}.
+
 The remaining arguments @var{args} are passed to @var{method} as
 arguments.  They are converted into D-Bus types as described in
 @ref{Type Conversion}.
diff --git a/etc/NEWS b/etc/NEWS
index 3d2b86cfb6a..fd6e3737eb8 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -79,6 +79,12 @@ levels that SHR cycles through when calling 'shr-zoom-image'.
 \f
 * Lisp Changes in Emacs 31.1
 
++++
+*** Support interactive D-Bus authentication
+A new ':authenticate t' parameter has been added to 'dbus-call-method'
+and 'dbus-call-method-asynchronously' to allow the invoked D-Bus method
+to interactively authenticate the user (e.g., via polkit).
+
 \f
 * Changes in Emacs 31.1 on Non-Free Operating Systems
 
diff --git a/lisp/net/dbus.el b/lisp/net/dbus.el
index dd5f0e88859..749a12b5368 100644
--- a/lisp/net/dbus.el
+++ b/lisp/net/dbus.el
@@ -297,6 +297,10 @@ dbus-call-method
 method call must return.  The default value is 25,000.  If the
 method call doesn't return in time, a D-Bus error is raised.
 
+If the parameter `:authenticate' is given and the following AUTH
+is non-nil, the invoked method may interactively prompt the user
+for authorization.  The default is nil.
+
 All other arguments ARGS are passed to METHOD as arguments.  They are
 converted into D-Bus types via the following rules:
 
@@ -427,6 +431,10 @@ dbus-call-method-asynchronously
 method call must return.  The default value is 25,000.  If the
 method call doesn't return in time, a D-Bus error is raised.
 
+If the parameter `:authenticate' is given and the following AUTH
+is non-nil, the invoked method may interactively prompt the user
+for authorization.  The default is nil.
+
 All other arguments ARGS are passed to METHOD as arguments.  They are
 converted into D-Bus types via the following rules:
 
diff --git a/src/dbusbind.c b/src/dbusbind.c
index 35ce03c7911..6037112cfe7 100644
--- a/src/dbusbind.c
+++ b/src/dbusbind.c
@@ -1314,7 +1314,7 @@ DEFUN ("dbus-message-internal", Fdbus_message_internal, Sdbus_message_internal,
 `dbus-call-method', `dbus-call-method-asynchronously':
   (dbus-message-internal
     dbus-message-type-method-call BUS SERVICE PATH INTERFACE METHOD HANDLER
-    &optional :timeout TIMEOUT &rest ARGS)
+    &optional :timeout TIMEOUT :authenticate AUTH &rest ARGS)
 
 `dbus-send-signal':
   (dbus-message-internal
@@ -1512,12 +1512,23 @@ DEFUN ("dbus-message-internal", Fdbus_message_internal, Sdbus_message_internal,
 	XD_SIGNAL1 (build_string ("Unable to create an error message"));
     }
 
-  /* Check for timeout parameter.  */
-  if ((count + 2 <= nargs) && EQ (args[count], QCtimeout))
+  while ((count + 2 <= nargs))
     {
-      CHECK_FIXNAT (args[count+1]);
-      timeout = min (XFIXNAT (args[count+1]), INT_MAX);
-      count = count+2;
+      /* Check for timeout parameter.  */
+      if (EQ (args[count], QCtimeout))
+        {
+          CHECK_FIXNAT (args[count+1]);
+          timeout = min (XFIXNAT (args[count+1]), INT_MAX);
+          count = count+2;
+	}
+      /* Check for authenticate parameter.  */
+      else if (EQ (args[count], QCauthenticate))
+        {
+	  dbus_message_set_allow_interactive_authorization
+	  (dmessage, NILP (args[count+1]) ? FALSE : TRUE);
+          count = count+2;
+	}
+      else break;
     }
 
   /* Initialize parameter list of message.  */
@@ -1895,6 +1906,9 @@ syms_of_dbusbind (void)
   /* Lisp symbol for method call timeout.  */
   DEFSYM (QCtimeout, ":timeout");
 
+  /* Lisp symbol for method interactive authentication.  */
+  DEFSYM (QCauthenticate, ":authenticate");
+
   /* Lisp symbols of D-Bus types.  */
   DEFSYM (QCbyte, ":byte");
   DEFSYM (QCboolean, ":boolean");
-- 
2.45.2