ProxyPass modifies 304 status to 200 and adds content-type

Question

The probelm

I am running a node server (sqlpad) through an Apache2 reverse proxy.

On some requests, the node server returns a 304 status code with no Content-Type when accessed directly. However, when accessed via the reverse proxy, the status code is changed to 200 and the Content-Type is added with a value of text/html. The addition of the Content-Type is causing the app to not load JS and CSS because X-Content-Type-Options: nosniff is in the header.

I really do not want to make changes to the node server since it is not my project. I would like to fix this with the reverse proxy configuration.

How can I configure Apache2 ProxyPass to forward the original 304 response, or at the very least, to not fill in the missing Content-Type with the default?

Here are my specifics:

Configuration

# /etc/apache2/sites-enabled/xxxx.conf
...
<Location "/sqlpad">
  ProxyPass http://x.x.x.x:xxxx # IP address of Node server
  ProxyPassReverse http://x.x.x.x:xxxx # IP address of Node server
</Location>


# /etc/apache2/apache2.conf (comments removed)

ServerName xxxxx.com
DefaultRuntimeDir ${APACHE_RUN_DIR}
PidFile ${APACHE_PID_FILE}
Timeout 600
KeepAlive On
MaxKeepAliveRequests 100
KeepAliveTimeout 5
User ${APACHE_RUN_USER}
Group ${APACHE_RUN_GROUP}
HostnameLookups Off
ErrorLog ${APACHE_LOG_DIR}/error.log
LogLevel warn
IncludeOptional mods-enabled/*.load
IncludeOptional mods-enabled/*.conf
Include ports.conf
<Directory />
    Options FollowSymLinks
    AllowOverride None
    Require all denied
</Directory>
<Directory /usr/share>
    AllowOverride None
    Require all granted
</Directory>
<Directory /var/www/>
    Options Indexes FollowSymLinks
    AllowOverride None
    Require all granted
</Directory>
AccessFileName .htaccess
<FilesMatch "^\.ht">
    Require all denied
</FilesMatch>
LogFormat "%v:%p %h %l %u %t \"%r\" %>s %O \"%{Referer}i\" \"%{User-Agent}i\"" vhost_combined
LogFormat "%h %l %u %t \"%r\" %>s %O \"%{Referer}i\" \"%{User-Agent}i\"" combined
LogFormat "%h %l %u %t \"%r\" %>s %O" common
LogFormat "%{Referer}i -> %U" referer
LogFormat "%{User-agent}i" agent
IncludeOptional conf-enabled/*.conf
IncludeOptional sites-enabled/*.conf

Headers

Original request/response (no proxy):

Request Url: http://xxxx/sqlpad/static/js/main.266789c5.js
Request Method: Get
Status: 304 Not Modified

Response Headers:

HTTP/1.1 304 Not Modified
X-DNS-Prefetch-Control: off
Strict-Transport-Security: max-age=15552000; includeSubDomains
X-Download-Options: noopen
X-Content-Type-Options: nosniff
X-XSS-Protection: 1; mode=block
Referrer-Policy: same-origin
Accept-Ranges: bytes
Cache-Control: public, max-age=0
Last-Modified: Sat, 26 Oct 1985 08:15:00 GMT
ETag: W/"1d86fc-7438674ba0"
Date: Wed, 13 Jun 2018 15:04:20 GMT
Connection: keep-alive

Request Headers:

GET /sqlpad/static/js/main.266789c5.js HTTP/1.1
Host: xxxx
Connection: keep-alive
If-None-Match: W/"1d86fc-7438674ba0"
If-Modified-Since: Sat, 26 Oct 1985 08:15:00 GMT
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_13_5) 
AppleWebKit/537.36 (KHTML, like Gecko) Chrome/67.0.3396.87 Safari/537.36
Accept: */*
Referer: http://localhost:56173/sqlpad/signin
Accept-Encoding: gzip, deflate, br
Accept-Language: en-US,en;q=0.9

Proxied request/response:

Request Url: http://xxxx/sqlpad/static/js/main.266789c5.js
Request Method: Get
Status: 200 OK

Response Headers:

Connection: Keep-Alive
Content-Encoding: gzip
Content-Length: 496
Content-Type: text/html; charset=utf-8
Date: Wed, 13 Jun 2018 15:18:29 GMT
ETag: W/"320-Lp3a/E+wIigPW+CnI/Elyd7OYoA-gzip"
Keep-Alive: timeout=5, max=98
Referrer-Policy: same-origin
Server: Apache/2.4.33 (Ubuntu)
Strict-Transport-Security: max-age=15552000; includeSubDomains
Vary: Accept-Encoding
X-Content-Type-Options: nosniff
X-DNS-Prefetch-Control: off
X-Download-Options: noopen
X-XSS-Protection: 1; mode=block

Request Headers:

GET /sqlpad/static/js/main.266789c5.js HTTP/1.1
Host: xxxx
Connection: keep-alive
If-None-Match: W/"320-Lp3a/E+wIigPW+CnI/Elyd7OYoA-gzip"
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_13_5) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/67.0.3396.87 Safari/537.36
Accept: */*
Referer: http://xxxx/sqlpad
Accept-Encoding: gzip, deflate
Accept-Language: en-US,en;q=0.9
Cookie: __zlcmid=xxxx; PHPSESSID=xxxx

I am using Apache/2.4.33 on Ubuntu 16.04.4

Answer 1

Consider setting DefaultContentType for the cases when Content type cannot be determined in mod_proxy.

This directive has been disabled. For backwards compatibility of configuration files, it may be specified with the value none, meaning no default media type. For example:

DefaultType None

resource: Apache Core Features