From c20d745028dcf2c772c581ae2cae2f88df565679 Mon Sep 17 00:00:00 2001
From: Badlop <badlop@process-one.net>
Date: Tue, 17 Jun 2025 17:31:49 +0200
Subject: [PATCH] New option hosts_alias and function resolve_host_alias/1
 (4400)

---
 src/ejabberd_config.erl      | 40 ++++++++++++++++++++++++++++++++++++
 src/ejabberd_http.erl        |  2 +-
 src/ejabberd_option.erl      |  5 +++++
 src/ejabberd_options.erl     |  9 ++++++++
 src/ejabberd_options_doc.erl | 17 +++++++++++++++
 5 files changed, 72 insertions(+), 1 deletion(-)

diff --git a/src/ejabberd_config.erl b/src/ejabberd_config.erl
index 3a556d7f6..3344a3f15 100644
--- a/src/ejabberd_config.erl
+++ b/src/ejabberd_config.erl
@@ -39,6 +39,7 @@
 -export([callback_modules/1]).
 -export([set_option/2]).
 -export([get_defined_keywords/1, get_predefined_keywords/1, replace_keywords/2, replace_keywords/3]).
+-export([resolve_host_alias/1]).
 
 %% Deprecated functions
 -export([get_option/2]).
@@ -510,6 +511,45 @@ get_predefined_keywords(Host) ->
         {<<"VERSION">>,
          misc:semver_to_xxyy(
              ejabberd_option:version())}].
+
+resolve_host_alias(Host) ->
+    case lists:member(Host, ejabberd_option:hosts()) of
+        true ->
+            Host;
+        false ->
+            resolve_host_alias2(Host)
+    end.
+
+resolve_host_alias2(Host) ->
+    Result =
+        lists:filter(fun({Alias1, _Vhost}) -> is_glob_match(Host, Alias1) end,
+                     ejabberd_option:hosts_alias()),
+    case Result of
+        [{_, Vhost} | _] when is_binary(Vhost) ->
+            ?DEBUG("(~p) Alias host '~s' resolved into vhost '~s'", [self(), Host, Vhost]),
+            Vhost;
+        [] ->
+            ?DEBUG("(~p) Request sent to host '~s', which isn't a vhost or an alias",
+                   [self(), Host]),
+            Host
+    end.
+
+%% Copied from ejabberd-2.0.0/src/acl.erl
+is_regexp_match(String, RegExp) ->
+    case ejabberd_regexp:run(String, RegExp) of
+        nomatch ->
+            false;
+        match ->
+            true;
+        {error, ErrDesc} ->
+            io:format("Wrong regexp ~p in ACL: ~p", [RegExp, ErrDesc]),
+            false
+    end.
+
+is_glob_match(String, <<"!", Glob/binary>>) ->
+    not is_regexp_match(String, ejabberd_regexp:sh_to_awk(Glob));
+is_glob_match(String, Glob) ->
+    is_regexp_match(String, ejabberd_regexp:sh_to_awk(Glob)).
 %% @format-end
 
 %%%===================================================================
diff --git a/src/ejabberd_http.erl b/src/ejabberd_http.erl
index 0e09c26c9..0ca7d3ff0 100644
--- a/src/ejabberd_http.erl
+++ b/src/ejabberd_http.erl
@@ -273,7 +273,7 @@ process_header(State, Data) ->
 		      request_headers = add_header(Name, Langs, State)};
       {ok, {http_header, _, 'Host' = Name, _, Value}} ->
 	  {Host, Port, TP} = get_transfer_protocol(State#state.addr_re, SockMod, Value),
-	  State#state{request_host = Host,
+	  State#state{request_host = ejabberd_config:resolve_host_alias(Host),
 		      request_port = Port,
 		      request_tp = TP,
 		      request_headers = add_header(Name, Value, State)};
diff --git a/src/ejabberd_option.erl b/src/ejabberd_option.erl
index d9ded9bdf..3a69da867 100644
--- a/src/ejabberd_option.erl
+++ b/src/ejabberd_option.erl
@@ -55,6 +55,7 @@
 -export([hide_sensitive_log_data/0, hide_sensitive_log_data/1]).
 -export([host_config/0]).
 -export([hosts/0]).
+-export([hosts_alias/0]).
 -export([include_config_file/0, include_config_file/1]).
 -export([install_contrib_modules/0]).
 -export([jwt_auth_only_rule/0, jwt_auth_only_rule/1]).
@@ -479,6 +480,10 @@ host_config() ->
 hosts() ->
     ejabberd_config:get_option({hosts, global}).
 
+-spec hosts_alias() -> [{binary(),binary()}].
+hosts_alias() ->
+    ejabberd_config:get_option({hosts_alias, global}).
+
 -spec include_config_file() -> any().
 include_config_file() ->
     include_config_file(global).
diff --git a/src/ejabberd_options.erl b/src/ejabberd_options.erl
index 489320840..521687aa2 100644
--- a/src/ejabberd_options.erl
+++ b/src/ejabberd_options.erl
@@ -182,6 +182,13 @@ opt_type(host_config) ->
         [unique]));
 opt_type(hosts) ->
     econf:non_empty(econf:list(econf:domain(), [unique]));
+opt_type(hosts_alias) ->
+    econf:and_then(
+      econf:map(econf:domain(), econf:domain(), [unique]),
+      econf:map(
+        econf:domain(),
+        econf:enum(ejabberd_config:get_option(hosts)),
+        [unique]));
 opt_type(include_config_file) ->
     econf:any();
 opt_type(install_contrib_modules) ->
@@ -587,6 +594,7 @@ options() ->
      {extauth_program, undefined},
      {fqdn, fun fqdn/1},
      {hide_sensitive_log_data, false},
+     {hosts_alias, []},
      {host_config, []},
      {include_config_file, []},
      {language, <<"en">>},
@@ -766,6 +774,7 @@ globals() ->
      ext_api_path_oauth,
      fqdn,
      hosts,
+     hosts_alias,
      host_config,
      install_contrib_modules,
      listen,
diff --git a/src/ejabberd_options_doc.erl b/src/ejabberd_options_doc.erl
index cbbc4be9f..375de0ca2 100644
--- a/src/ejabberd_options_doc.erl
+++ b/src/ejabberd_options_doc.erl
@@ -712,6 +712,23 @@ doc() ->
              "  domain.tld:",
              "    auth_method:",
              "      - ldap"]}},
+     {hosts_alias,
+      #{value => "{Alias: Host}",
+        desc =>
+            ?T("Define aliases for existing vhosts managed by ejabberd. "
+               "An alias may be a regexp expression. "
+               "This option is only consulted by the 'ejabberd_http' listener."),
+        note => "added in 25.xx",
+        example =>
+            ["hosts:",
+             "  - domain.tld",
+             "  - example.org",
+             "",
+             "hosts_alias:",
+             "  xmpp.domain.tld: domain.tld",
+             "  jabber.domain.tld: domain.tld",
+             "  mytest.net: example.org",
+             "  \"exa*\": example.org"]}},
      {include_config_file,
       #{value => "[Filename, ...\\] | {Filename: Options}",
         desc =>