mirror of
https://github.com/PrivSec-dev/privsec.dev
synced 2024-11-18 12:31:35 -05:00
96 lines
3.8 KiB
Markdown
96 lines
3.8 KiB
Markdown
---
|
|
title: "Slightly Improving Mailcow Security"
|
|
date: 2022-07-18
|
|
tags: ['Applications', 'Linux', 'Security']
|
|
author: Tommy
|
|
---
|
|
|
|
|
|
|
|
Mailcow is a fairly popular self-hosted mail server. If you use it, there are a few ways you can improve its security by following these steps.
|
|
|
|
## Postfix Configuration
|
|
|
|
Consider disabling weak ciphers and TLS versions below 1.2 in `data/conf/postfix/extra.cf`:
|
|
|
|
```
|
|
tls_high_cipherlist = ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305:ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256
|
|
tls_preempt_cipherlist = yes
|
|
|
|
smtp_tls_protocols = !SSLv2, !SSLv3, !TLSv1, !TLSv1.1
|
|
smtp_tls_ciphers = high
|
|
smtp_tls_mandatory_ciphers = high
|
|
|
|
smtpd_tls_protocols = !SSLv2, !SSLv3, !TLSv1, !TLSv1.1
|
|
smtpd_tls_ciphers = high
|
|
smtpd_tls_mandatory_ciphers = high
|
|
```
|
|
|
|
## NGINX Configuration
|
|
|
|
These security configurations can be added/modified in `data/conf/nginx/includes/site-defaults.conf`.
|
|
|
|
### SSL Ciphers
|
|
|
|
Consider only supporting ciphers matching that of TLSv1.3:
|
|
|
|
```
|
|
ssl_ciphers "ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-ECDSA-AES128-GCM-SHA256";
|
|
```
|
|
|
|
### HSTS
|
|
|
|
Consider adding `includeSubDomains;` and `preload;` to the HSTS configuration if all of your services are using HTTPS:
|
|
|
|
```
|
|
add_header Strict-Transport-Security "max-age=63072000; includeSubDomains; preload";
|
|
```
|
|
|
|
### X-XSS-Protection
|
|
|
|
We will setup Content Security, so this header is no longer needed. In fact, it may do [more harm than good](https://github.com/helmetjs/helmet/issues/230). Change the setting to `0`:
|
|
|
|
```
|
|
add_header X-XSS-Protection "0";
|
|
```
|
|
|
|
### Permission Policy
|
|
|
|
Mailcow does not need any special permissions to operate, except for USB which is needed to access your FIDO2 keys if you use them.
|
|
|
|
Add this header to deny other permissions:
|
|
|
|
```
|
|
add_header Permissions-Policy "accelerometer=(), ambient-light-sensor=(), autoplay=(), battery=(), camera=(), clipboard-read=(), display-capture=(), document-domain=(), encrypted-media=(), fullscreen=(), geolocation=(), gyroscope=(), hid=(), idle-detection=(), interest-cohort=(), magnetometer=(), microphone=(), midi=(), payment=(), picture-in-picture=(), screen-wake-lock=(), serial=(), usb=(), sync-xhr=(), xr-spatial-tracking=()";
|
|
```
|
|
|
|
### Content Security Policy
|
|
|
|
Use the following as your [Content Security Policy](https://developer.mozilla.org/en-US/docs/Web/HTTP/CSP#:~:text=Content%20Security%20Policy%20(CSP)%20is,site%20defacement%2C%20to%20malware%20distribution.):
|
|
|
|
#### If you use Gravatar with SOGo
|
|
|
|
```
|
|
add_header Content-Security-Policy "default-src 'none'; connect-src 'self' https://api.github.com; font-src 'self' https://fonts.gstatic.com; img-src 'self' data:; script-src 'self' 'unsafe-inline'; style-src 'self' 'unsafe-inline' https://fonts.googleapis.com; frame-ancestors 'none'; block-all-mixed-content; base-uri 'none'";
|
|
```
|
|
|
|
#### If you do not use Gravatar with SOGo
|
|
|
|
```
|
|
add_header Content-Security-Policy "default-src 'none'; connect-src 'self' https://api.github.com https://www.gravatar.com; font-src 'self' https://fonts.gstatic.com; img-src 'self' data: https://www.gravatar.com; script-src 'self' 'unsafe-inline'; style-src 'self' 'unsafe-inline' https://fonts.googleapis.com; frame-ancestors 'none'; block-all-mixed-content; base-uri 'none'";
|
|
```
|
|
|
|
### Cross-Origin Resource, Opener, and Embedder Policies
|
|
|
|
Mailcow does not use any cross site scripts, or documents. Thus, you should set CORP and COOP headers to their strictest configuration:
|
|
|
|
```
|
|
add_header Cross-Origin-Resource-Policy same-origin;
|
|
add_header Cross-Origin-Opener-Policy same-origin;
|
|
```
|
|
|
|
If you do not use Gravatar with SOGo, you can also set COEP to require-corp since image embedding will not be used either:
|
|
|
|
```
|
|
add_header Cross-Origin-Embedder-Policy require-corp;
|
|
``` |