email: validate addresses following the HTML specs

If we are going to try and validate email addresses, at least do it by
following some existing specification and document it.

It remains on app developpers to:
 * make sure their addresses are ASCII-only, by converting international
   labels to Punycode
 * remove anything but the addresses, `Some Name <[email protected]>` is
   not accepted

[smcv: Fix merge conflicts in tests/test_email.py]
Co-authored-by: Simon McVittie <[email protected]>

data/org.freedesktop.portal.Email.xml

@@ -64,13 +64,15 @@
           <varlistentry>
             <term>address s</term>
             <listitem><para>
-              The email address to send to.
+              The email address to send to. Must conform to the HTML5 definition of
+              <ulink url="https://html.spec.whatwg.org/multipage/input.html#valid-e-mail-address">valid email address</ulink>.
             </para></listitem>
           </varlistentry>
           <varlistentry>
             <term>addresses as</term>
             <listitem><para>
-              Email addresses to send to. This will be used in addition to address.
+              Email addresses to send to. This will be used in addition to address and must
+              pass the same validation.
             </para><para>
               This option was added in version 3.
             </para></listitem>

src/email.c

@@ -118,7 +118,11 @@ compose_email_done (GObject *source,
 static gboolean
 is_valid_email (const char *string)
 {
-  return g_regex_match_simple ("^\\w+([-+.]\\w+)*@\\w+([-.]\\w+)*\\.\\w+([-.]\\w+)*$", string, 0, 0);
+  // Regex proposed by the W3C at https://html.spec.whatwg.org/multipage/input.html#valid-e-mail-address
+  return g_regex_match_simple ("^[a-zA-Z0-9.!#$%&'*+/=?^_`{|}~-]+"
+                               "@[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?"
+                               "(?:\\.[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?)*$",
+                               string, 0, 0);
 }
 
 static gboolean

tests/email.c

@@ -130,6 +130,48 @@ test_email_address (void)
     g_main_context_iteration (NULL, TRUE);
 }
 
+/* test that punycode-encoded email addresses pass validation
+ */
+void
+test_email_punycode_address (void)
+{
+  g_autoptr(XdpPortal) portal = NULL;
+  g_autoptr(GKeyFile) keyfile = NULL;
+  g_autoptr(GError) error = NULL;
+  g_autofree char *path = NULL;
+  const char *addresses[2] = { "[email protected]", NULL };
+
+  keyfile = g_key_file_new ();
+
+  g_key_file_set_string (keyfile, "input", "address", "[email protected]");
+  g_key_file_set_string (keyfile, "input", "subject", "Re: portal tests");
+  g_key_file_set_string (keyfile, "input", "body", "To ASCII and beyond");
+
+  g_key_file_set_integer (keyfile, "backend", "delay", 0);
+  g_key_file_set_integer (keyfile, "backend", "response", 0);
+  g_key_file_set_integer (keyfile, "result", "response", 0);
+
+  path = g_build_filename (outdir, "email", NULL);
+  g_key_file_save_to_file (keyfile, path, &error);
+  g_assert_no_error (error);
+
+  portal = xdp_portal_new ();
+
+  got_info = 0;
+  xdp_portal_compose_email (portal, NULL,
+                            addresses, NULL, NULL,
+                            "Re: portal tests",
+                            "To ASCII and beyond",
+                            NULL,
+                            0,
+                            NULL,
+                            email_cb,
+                            keyfile);
+
+  while (!got_info)
+    g_main_context_iteration (NULL, TRUE);
+}
+
 /* test that an invalid subject triggers an error
  */
 void

tests/email.h

@@ -2,6 +2,7 @@
 
 void test_email_basic (void);
 void test_email_address (void);
+void test_email_punycode_address (void);
 void test_email_subject (void);
 void test_email_delay (void);
 void test_email_cancel (void);

tests/test-portals.c

@@ -483,6 +483,7 @@ main (int argc, char **argv)
   g_test_add_func ("/portal/email/cancel", test_email_cancel);
   g_test_add_func ("/portal/email/close", test_email_close);
   g_test_add_func ("/portal/email/address", test_email_address);
+  g_test_add_func ("/portal/email/punycode_address", test_email_punycode_address);
   g_test_add_func ("/portal/email/subject", test_email_subject);
   g_test_add_func ("/portal/email/parallel", test_email_parallel);
 

tests/test_email.py

@@ -74,6 +74,34 @@ def test_email_address(self, portal_mock):
         method_calls = portal_mock.mock_interface.GetMethodCalls("ComposeEmail")
         assert len(method_calls) == 0
 
+    def test_email_punycode_address(self, portal_mock):
+        addresses = ["[email protected]"]
+        subject = "Re: portal tests"
+        body = "To ASCII and beyond"
+
+        request = portal_mock.create_request()
+        options = {
+            "addresses": addresses,
+            "subject": subject,
+            "body": body,
+        }
+        response = request.call(
+            "ComposeEmail",
+            parent_window="",
+            options=options,
+        )
+
+        assert response.response == 0
+
+        # Check the impl portal was called with the right args
+        method_calls = portal_mock.mock_interface.GetMethodCalls("ComposeEmail")
+        assert len(method_calls) > 0
+        _, args = method_calls[-1]
+        assert args[2] == ""  # parent window
+        assert args[3]["addresses"] == addresses
+        assert args[3]["subject"] == subject
+        assert args[3]["body"] == body
+
     def test_email_subject_multiline(self, portal_mock):
         """test that an multiline subject triggers an error"""