Add return code redirects to Nginx URL rewriting pages

This PR adds a "Redirect all requests" option to the server block and location URL Re-Writing pages in the Nginx Webserver module, backed by the Nginx return directive with a choice of 301, 302, 303, 307 or 308.

The existing rewrite table only offers the redirect and permanent flags, which map to 302 and 301. The other codes requested on the forum are not supported by rewrite at all, so they can only be provided through return.

The new option only manages return directives that are redirects. A bare URL form such as return https://example.com/; is shown as a 302, while non-redirect uses like return 404; are hidden from the page and never modified or removed.

Example of the resulting config for a server block:

return 308 "https://example.com$request_uri";

Fixes https://forum.virtualmin.com/t/137940

CHANGELOG.md

@@ -5,6 +5,7 @@
 * Add webserver logging controls to Usermin Configuration module
 * Add option to rotate Webmin and Usermin webserver logs using `logrotate` instead of periodically clearing them [#2821](https://github.com/webmin/webmin/pull/2821)
 * Add DNF 4 and 5 package hold management to the Software Package Updates module
+* Add `return` based redirects with 301, 302, 303, 307 and 308 codes to the URL Re-Writing pages in the Nginx Webserver module [forum.virtualmin.com/t/137940](https://forum.virtualmin.com/t/137940)
 * Fix DNF update confirmations by previewing packages and dependencies that will be installed or updated
 * Fix PostgreSQL initialization on EL systems to use SCRAM-SHA-256 authentication by default
 * Fix IPsec host key generation with modern Libreswan [#2132](https://github.com/webmin/webmin/issues/2132)

nginx/edit_lrewrite.cgi

@@ -23,6 +23,8 @@ print &ui_table_start($text{'rewrite_header'}, undef, 2);
 
 print &nginx_rewrite_input("rewrite", $location);
 
+print &nginx_return_input("return", $location);
+
 print &nginx_onoff_input("rewrite_log", $location);
 
 print &ui_table_end();

nginx/edit_srewrite.cgi

@@ -19,6 +19,8 @@ print &ui_table_start($text{'rewrite_header'}, undef, 2);
 
 print &nginx_rewrite_input("rewrite", $server);
 
+print &nginx_return_input("return", $server);
+
 print &nginx_onoff_input("rewrite_log", $server);
 
 print &ui_table_end();

nginx/lang/en

@@ -324,6 +324,16 @@ rewrite_redirect=Return 302 redirect
 rewrite_permanent=Return 301 redirect
 rewrite_efrom=Source path $1 contains spaces
 rewrite_eto=Destination URL $1 is missing or contains spaces
+opt_return=Redirect all requests
+rewrite_return_none=No redirect
+rewrite_return_to=to URL
+rewrite_return_301=301 (Moved permanently)
+rewrite_return_302=302 (Found)
+rewrite_return_303=303 (See other)
+rewrite_return_307=307 (Temporary redirect)
+rewrite_return_308=308 (Permanent redirect)
+rewrite_ereturn=Redirect URL is missing or contains spaces
+rewrite_ereturncode=Invalid redirect HTTP code
 
 location_create=Create Location
 location_edit=Edit Location

nginx/nginx-lib.pl

@@ -1462,6 +1462,73 @@ for(my $i=0; defined(my $from = $in->{$name."_from_".$i}); $i++) {
 &save_directive($parent, $name, \@obj);
 }
 
+# list_return_redirect_codes()
+# Returns the HTTP codes that the return directive accepts with a URL
+sub list_return_redirect_codes
+{
+return ( 301, 302, 303, 307, 308 );
+}
+
+# get_return_redirect(&object)
+# Returns the code and URL of a return directive if it is a redirect, or an
+# empty list for other uses such as return 404
+sub get_return_redirect
+{
+my ($obj) = @_;
+my @w = @{$obj->{'words'}};
+if (@w == 2 && &indexof($w[0], &list_return_redirect_codes()) >= 0) {
+	return @w;
+	}
+elsif (@w == 1 && $w[0] =~ /^(https?:\/\/|\$scheme)/) {
+	# Single URL form defaults to a 302 redirect
+	return ( 302, $w[0] );
+	}
+return ( );
+}
+
+# nginx_return_input(name, &parent)
+# Returns HTML for a redirect via the return directive
+sub nginx_return_input
+{
+my ($name, $parent) = @_;
+return undef if (!&supported_directive($name, $parent));
+my $obj = &find($name, $parent);
+my ($code, $url) = $obj ? &get_return_redirect($obj) : ( );
+# Leave a return directive that is not a redirect alone
+return undef if ($obj && !$code);
+my $sel = &ui_select($name."_code", $code || 301,
+		     [ map { [ $_, $text{'rewrite_return_'.$_} ] }
+			   &list_return_redirect_codes() ]);
+return &ui_table_row($text{'opt_'.$name},
+	&ui_opt_textbox($name, $url, 50, $text{'rewrite_return_none'},
+			$sel." ".$text{'rewrite_return_to'}." ", 0,
+			[ $name."_code" ]), 3);
+}
+
+# nginx_return_parse(name, &parent, &in)
+# Updates the config with input from nginx_return_input
+sub nginx_return_parse
+{
+my ($name, $parent, $in) = @_;
+return undef if (!&supported_directive($name, $parent));
+$in ||= \%in;
+my $obj = &find($name, $parent);
+# Never touch a return directive that was not shown in the form
+return undef if ($obj && !&get_return_redirect($obj));
+if ($in->{$name."_def"}) {
+	&save_directive($parent, $name, [ ]);
+	}
+else {
+	my $code = $in->{$name."_code"};
+	&indexof($code, &list_return_redirect_codes()) >= 0 ||
+		&error($text{'rewrite_ereturncode'});
+	my $url = $in->{$name};
+	$url =~ /^\S+$/ || &error($text{'rewrite_ereturn'});
+	&save_directive($parent, $name, [ { 'name' => $name,
+					    'words' => [ $code, $url ] } ]);
+	}
+}
+
 # list_log_formats([&server])
 # Returns a list of all log format names
 sub list_log_formats

nginx/save_lrewrite.cgi

@@ -16,6 +16,8 @@ $location || &error($text{'location_egone'});
 
 &nginx_rewrite_parse("rewrite", $location);
 
+&nginx_return_parse("return", $location);
+
 &nginx_onoff_parse("rewrite_log", $location);
 
 &flush_config_file_lines();

nginx/save_srewrite.cgi

@@ -14,6 +14,8 @@ $server || &error($text{'server_egone'});
 
 &nginx_rewrite_parse("rewrite", $server);
 
+&nginx_return_parse("return", $server);
+
 &nginx_onoff_parse("rewrite_log", $server);
 
 &flush_config_file_lines();