Update docs

- Improve security by removing support for modp1024 (DH group 2),
  which is less secure and no longer enabled in Libreswan by default.
- The native VPN client on Android devices uses modp1024 for the
  IPsec/L2TP and IPsec/XAuth ("Cisco IPsec") modes. After this change,
  Android users should instead connect using IKEv2 mode (recommended).

docs/clients-xauth-zh.md

@@ -74,7 +74,13 @@ VPN 连接成功后，你会在 VPN Connect 状态窗口中看到 **tunnel enabl
 
 ## Android
 
-> 你也可以使用 [IKEv2](ikev2-howto-zh.md)（推荐）或者 [IPsec/L2TP](clients-zh.md) 模式连接。Android 12 仅支持 [IKEv2](ikev2-howto-zh.md) 模式。
+**重要：** Android 用户应该使用更安全的 [IKEv2 模式](ikev2-howto-zh.md) 连接（推荐）。Android 12+ 仅支持 IKEv2 模式。Android 系统自带的 VPN 客户端对 IPsec/L2TP 和 IPsec/XAuth ("Cisco IPsec") 模式使用安全性较低的 `modp1024` (DH group 2)。
+
+如果你仍然想用 IPsec/XAuth 模式连接，你必须首先编辑 VPN 服务器上的 `/etc/ipsec.conf` 并在 `ike=...` 一行的末尾加上 `,aes256-sha2;modp1024,aes128-sha1;modp1024` 字样。保存文件并运行 `sudo service ipsec restart`。
+
+Docker 用户：在 [你的 env 文件](https://github.com/hwdsl2/docker-ipsec-vpn-server/blob/master/README-zh.md#如何使用本镜像) 中添加 `VPN_ENABLE_MODP1024=yes`，然后重新创建 Docker 容器。
+
+然后在你的 Android 设备上进行以下步骤：
 
 1. 启动 **设置** 应用程序。
 1. 单击 **网络和互联网**。或者，如果你使用 Android 7 或更早版本，在 **无线和网络** 部分单击 **更多...**。

docs/clients-xauth.md

@@ -74,7 +74,13 @@ If you get an error when trying to connect, see [Troubleshooting](clients.md#tro
 
 ## Android
 
-> You may also connect using [IKEv2](ikev2-howto.md) (recommended) or [IPsec/L2TP](clients.md) mode. Android 12 only supports [IKEv2](ikev2-howto.md) mode.
+**Important:** Android users should instead connect using [IKEv2 mode](ikev2-howto.md) (recommended), which is more secure. Android 12+ only supports IKEv2 mode. The native VPN client in Android uses the less secure `modp1024` (DH group 2) for the IPsec/L2TP and IPsec/XAuth ("Cisco IPsec") modes.
+
+If you still want to connect using IPsec/XAuth mode, you must first edit `/etc/ipsec.conf` on the VPN server. Find the line `ike=...` and append `,aes256-sha2;modp1024,aes128-sha1;modp1024` at the end. Save the file and run `sudo service ipsec restart`.
+
+Docker users: Add `VPN_ENABLE_MODP1024=yes` to [your env file](https://github.com/hwdsl2/docker-ipsec-vpn-server#how-to-use-this-image), then re-create the Docker container.
+
+After that, follow the steps below on your Android device:
 
 1. Launch the **Settings** application.
 1. Tap "Network & internet". Or, if using Android 7 or earlier, tap **More...** in the **Wireless & networks** section.

docs/clients-zh.md

@@ -145,7 +145,13 @@ Add-VpnConnection -Name 'My IPsec VPN' -ServerAddress '你的 VPN 服务器 IP'
 
 ## Android
 
-> 你也可以使用 [IKEv2](ikev2-howto-zh.md)（推荐）或者 [IPsec/XAuth](clients-xauth-zh.md) 模式连接。Android 12 仅支持 [IKEv2](ikev2-howto-zh.md) 模式。
+**重要：** Android 用户应该使用更安全的 [IKEv2 模式](ikev2-howto-zh.md) 连接（推荐）。Android 12+ 仅支持 IKEv2 模式。Android 系统自带的 VPN 客户端对 IPsec/L2TP 和 IPsec/XAuth ("Cisco IPsec") 模式使用安全性较低的 `modp1024` (DH group 2)。
+
+如果你仍然想用 IPsec/L2TP 模式连接，你必须首先编辑 VPN 服务器上的 `/etc/ipsec.conf` 并在 `ike=...` 一行的末尾加上 `,aes256-sha2;modp1024,aes128-sha1;modp1024` 字样。保存文件并运行 `sudo service ipsec restart`。
+
+Docker 用户：在 [你的 env 文件](https://github.com/hwdsl2/docker-ipsec-vpn-server/blob/master/README-zh.md#如何使用本镜像) 中添加 `VPN_ENABLE_MODP1024=yes`，然后重新创建 Docker 容器。
+
+然后在你的 Android 设备上进行以下步骤：
 
 1. 启动 **设置** 应用程序。
 1. 单击 **网络和互联网**。或者，如果你使用 Android 7 或更早版本，在 **无线和网络** 部分单击 **更多...**。

docs/clients.md

@@ -144,7 +144,13 @@ If you get an error when trying to connect, see [Troubleshooting](#troubleshooti
 
 ## Android
 
-> You may also connect using [IKEv2](ikev2-howto.md) (recommended) or [IPsec/XAuth](clients-xauth.md) mode. Android 12 only supports [IKEv2](ikev2-howto.md) mode.
+**Important:** Android users should instead connect using [IKEv2 mode](ikev2-howto.md) (recommended), which is more secure. Android 12+ only supports IKEv2 mode. The native VPN client in Android uses the less secure `modp1024` (DH group 2) for the IPsec/L2TP and IPsec/XAuth ("Cisco IPsec") modes.
+
+If you still want to connect using IPsec/L2TP mode, you must first edit `/etc/ipsec.conf` on the VPN server. Find the line `ike=...` and append `,aes256-sha2;modp1024,aes128-sha1;modp1024` at the end. Save the file and run `sudo service ipsec restart`.
+
+Docker users: Add `VPN_ENABLE_MODP1024=yes` to [your env file](https://github.com/hwdsl2/docker-ipsec-vpn-server#how-to-use-this-image), then re-create the Docker container.
+
+After that, follow the steps below on your Android device:
 
 1. Launch the **Settings** application.
 1. Tap "Network & internet". Or, if using Android 7 or earlier, tap **More...** in the **Wireless & networks** section.

extras/vpnupgrade_alpine.sh

@@ -209,7 +209,7 @@ update_ikev2_script() {
 
 update_config() {
   bigecho "Updating VPN configuration..."
-  IKE_NEW="  ike=aes256-sha2,aes128-sha2,aes256-sha1,aes128-sha1,aes256-sha2;modp1024,aes128-sha1;modp1024"
+  IKE_NEW="  ike=aes256-sha2,aes128-sha2,aes256-sha1,aes128-sha1"
   PHASE2_NEW="  phase2alg=aes_gcm-null,aes128-sha1,aes256-sha1,aes256-sha2_512,aes128-sha2,aes256-sha2"
   if uname -m | grep -qi '^arm'; then
     if ! modprobe -q sha512; then

extras/vpnupgrade_amzn.sh

@@ -203,7 +203,7 @@ update_ikev2_script() {
 
 update_config() {
   bigecho "Updating VPN configuration..."
-  IKE_NEW="  ike=aes256-sha2,aes128-sha2,aes256-sha1,aes128-sha1,aes256-sha2;modp1024,aes128-sha1;modp1024"
+  IKE_NEW="  ike=aes256-sha2,aes128-sha2,aes256-sha1,aes128-sha1"
   PHASE2_NEW="  phase2alg=aes_gcm-null,aes128-sha1,aes256-sha1,aes256-sha2_512,aes128-sha2,aes256-sha2"
   dns_state=0
   DNS_SRV1=$(grep "modecfgdns1=" /etc/ipsec.conf | head -n 1 | cut -d '=' -f 2)

extras/vpnupgrade_centos.sh

@@ -255,7 +255,7 @@ update_ikev2_script() {
 
 update_config() {
   bigecho "Updating VPN configuration..."
-  IKE_NEW="  ike=aes256-sha2,aes128-sha2,aes256-sha1,aes128-sha1,aes256-sha2;modp1024,aes128-sha1;modp1024"
+  IKE_NEW="  ike=aes256-sha2,aes128-sha2,aes256-sha1,aes128-sha1"
   PHASE2_NEW="  phase2alg=aes_gcm-null,aes128-sha1,aes256-sha1,aes256-sha2_512,aes128-sha2,aes256-sha2"
   dns_state=0
   DNS_SRV1=$(grep "modecfgdns1=" /etc/ipsec.conf | head -n 1 | cut -d '=' -f 2)

extras/vpnupgrade_ubuntu.sh

@@ -239,7 +239,7 @@ update_ikev2_script() {
 
 update_config() {
   bigecho "Updating VPN configuration..."
-  IKE_NEW="  ike=aes256-sha2,aes128-sha2,aes256-sha1,aes128-sha1,aes256-sha2;modp1024,aes128-sha1;modp1024"
+  IKE_NEW="  ike=aes256-sha2,aes128-sha2,aes256-sha1,aes128-sha1"
   PHASE2_NEW="  phase2alg=aes_gcm-null,aes128-sha1,aes256-sha1,aes256-sha2_512,aes128-sha2,aes256-sha2"
   if uname -m | grep -qi '^arm'; then
     if ! modprobe -q sha512; then

vpnsetup_alpine.sh

@@ -337,7 +337,7 @@ conn shared
   dpdtimeout=300
   dpdaction=clear
   ikev2=never
-  ike=aes256-sha2,aes128-sha2,aes256-sha1,aes128-sha1,aes256-sha2;modp1024,aes128-sha1;modp1024
+  ike=aes256-sha2,aes128-sha2,aes256-sha1,aes128-sha1
   phase2alg=aes_gcm-null,aes128-sha1,aes256-sha1,aes256-sha2_512,aes128-sha2,aes256-sha2
   ikelifetime=24h
   salifetime=24h

vpnsetup_amzn.sh

@@ -353,7 +353,7 @@ conn shared
   dpdtimeout=300
   dpdaction=clear
   ikev2=never
-  ike=aes256-sha2,aes128-sha2,aes256-sha1,aes128-sha1,aes256-sha2;modp1024,aes128-sha1;modp1024
+  ike=aes256-sha2,aes128-sha2,aes256-sha1,aes128-sha1
   phase2alg=aes_gcm-null,aes128-sha1,aes256-sha1,aes256-sha2_512,aes128-sha2,aes256-sha2
   ikelifetime=24h
   salifetime=24h

vpnsetup_centos.sh

@@ -453,7 +453,7 @@ conn shared
   dpdtimeout=300
   dpdaction=clear
   ikev2=never
-  ike=aes256-sha2,aes128-sha2,aes256-sha1,aes128-sha1,aes256-sha2;modp1024,aes128-sha1;modp1024
+  ike=aes256-sha2,aes128-sha2,aes256-sha1,aes128-sha1
   phase2alg=aes_gcm-null,aes128-sha1,aes256-sha1,aes256-sha2_512,aes128-sha2,aes256-sha2
   ikelifetime=24h
   salifetime=24h

vpnsetup_ubuntu.sh

@@ -398,7 +398,7 @@ conn shared
   dpdtimeout=300
   dpdaction=clear
   ikev2=never
-  ike=aes256-sha2,aes128-sha2,aes256-sha1,aes128-sha1,aes256-sha2;modp1024,aes128-sha1;modp1024
+  ike=aes256-sha2,aes128-sha2,aes256-sha1,aes128-sha1
   phase2alg=aes_gcm-null,aes128-sha1,aes256-sha1,aes256-sha2_512,aes128-sha2,aes256-sha2
   ikelifetime=24h
   salifetime=24h