Getting Reverse Proxy to work

Question

I have a Django web app sharing external ports 80 and 443 with another server. localhost works fine without the reverse proxy, but when it is enabled, I run into all kinds of errors.

How to make reverse proxy work properly?

reverse-proxy.conf:

      # SSL Certificate and other SSL configurations
      SSLProxyEngine on
      ProxyRequests on
      SSLProxyVerify require 
      SSLProxyCheckPeerCN on
      SSLProxyCheckPeerName on
      SSLProxyCheckPeerExpire on
      ProxyPreserveHost on
      RequestHeader set X-Forwarded-Proto https

      # Reverse Proxy Configuration
      ProxyPass "/" "https://192.168.1.83/"
      ProxyPassReverse "/" "https://192.168.1.83/"

      # Additional SSL configurations if needed

I redirect all http to https and included the above proxy in my ssl-https conf file. The site runs normally without the inclusion (i.e. when Include .../reverse-proxy.conf is commented out). When reverse proxy is included, I get:

[Thu Jan 18 07:09:39.835368 2024] [ssl:error] [pid 46505:tid 133251102926528] [remote 192.168.1.83:443] AH02039: Certificate Verification: Error (20): unable to get local issuer certificate
[Thu Jan 18 07:09:39.835470 2024] [ssl:error] [pid 46505:tid 133251102926528] [remote 192.168.1.83:443] AH02040: Certificate Verification: Certificate Chain too long (chain has 2 certificates, but maximum allowed are only 1)
[Thu Jan 18 07:09:39.835773 2024] [proxy:error] [pid 46505:tid 133251102926528] (20014)Internal error (specific information not available): [client 119.74.38.81:51224] AH01084: pass request body failed to 192.168.1.83:443 (192.168.1.83), referer: https://acupunctureclassique.duckdns.org/
[Thu Jan 18 07:09:39.835832 2024] [proxy:error] [pid 46505:tid 133251102926528] [client 119.74.38.81:51224] AH00898: Error during SSL Handshake with remote server returned by /login/, referer: https://acupunctureclassique.duckdns.org/
[Thu Jan 18 07:09:39.835861 2024] [proxy_http:error] [pid 46505:tid 133251102926528] [client 119.74.38.81:51224] AH01097: pass request body failed to 192.168.1.83:443 (192.168.1.83) from 119.74.38.81 (), referer: https://acupunctureclassique.duckdns.org/

On the front end:

Proxy Error
The proxy server could not handle the request

Reason: Error during SSL Handshake with remote server

Apache/2.4.58 (Ubuntu) Server at acupunctureclassique.duckdns.org Port 443

---

Update:

apachectl -S

VirtualHost configuration:
*:443                  acupunctureclassique.duckdns.org (/etc/apache2/sites-enabled/acu-le-ssl.conf:2)
*:80                   acupunctureclassique.duckdns.org (/etc/apache2/sites-enabled/acu.conf:1)
ServerRoot: "/etc/apache2"
Main DocumentRoot: "/var/www/html"
Main ErrorLog: "/var/log/apache2/error.log"
Mutex ssl-stapling: using_defaults
Mutex proxy: using_defaults
Mutex ssl-cache: using_defaults
Mutex default: dir="/var/run/apache2/" mechanism=default 
Mutex watchdog-callback: using_defaults
Mutex rewrite-map: using_defaults
Mutex ssl-stapling-refresh: using_defaults
PidFile: "/var/run/apache2/apache2.pid"
Define: DUMP_VHOSTS
Define: DUMP_RUN_CFG
User: name="www-data" id=33 not_used
Group: name="www-data" id=33 not_used

Answer 1

The actual problem here turned out to be - after discussions in chat - that the user was using nginx to proxy traffic to the same nginx instance, creating a neat redirect loop, which eventually lead to a too large header-error message.

> ProxyPass "/" "https://192.168.1.83/"

You send your traffic to https://192.168.1.83. You claim this is a certificate issued by Let's encrypt, but LE will never issue a certificate for 192.168.1.83, nor will any public CA issue such a certificate. Remember that a valid certificate is not enough, it has to match the expected name - which in this case is 192.168.1.83. Your logs are pretty explicit about this as well.

You have a few alternatives:

1. Use HTTP
2. Use a self signed certificate and make Apache trust it using SSLProxyCACertificate directive.
3. Use a valid domain name and acquire a valid certificate for the domain name. The domain name may resolve to 192.168.1.83, or it may be added to /etc/hosts, but Apache will match hostname and Common Name (or SAN) in certificate.
4. Disable verification of name using SSLProxyCheckPeerName = off
5. Disable verification using SSLProxyVerify = none, effectively disabling verification. This is more or less equivalent with using http...

Answer 2

To reverse proxy you need to create an virtual host in /etc/apache2/sites-available. Here an example of such an VirtualHost configuration

<VirtualHost *:80>
    ServerName yourdomain.com
    ServerAlias www.yourdomain.com

    DocumentRoot /path/to/your/django/static/files

    Alias /static/ /path/to/your/django/static/files/
    <Directory /path/to/your/django/static/files>
        Require all granted
    </Directory>

    ProxyPass / http://localhost:8000/
    ProxyPassReverse / http://localhost:8000/

    ErrorLog ${APACHE_LOG_DIR}/error.log
    CustomLog ${APACHE_LOG_DIR}/access.log combined
</VirtualHost>

<VirtualHost *:443>
    ServerName yourdomain.com
    ServerAlias www.yourdomain.com

    DocumentRoot /path/to/your/django/static/files

    Alias /static/ /path/to/your/django/static/files/
    <Directory /path/to/your/django/static/files>
        Require all granted
    </Directory>

    SSLEngine on
    SSLCertificateFile /path/to/your/ssl/certificate.crt
    SSLCertificateKeyFile /path/to/your/ssl/private.key
    SSLCertificateChainFile /path/to/your/ssl/chainfile.pem

    ProxyPass / https://localhost:8000/
    ProxyPassReverse / https://localhost:8000/

    ErrorLog ${APACHE_LOG_DIR}/error.log
    CustomLog ${APACHE_LOG_DIR}/access.log combined
</VirtualHost>

The https part is optional you can leave that out if you don't need https