I have a site hosted with a shared hosting provider. It is an Apache with FPM/FastCGI and PHP 7.2
Being shared hosting, the only configuration I have access to is htaccess, but obviously not any of the Apache conf files.
I have a custom error page configured in my htaccess like this: ErrorDocument 404 /error404.php. Today I noticed that my custom error 404 page was not being displayed. Instead plain text File not found. is returned to the browser with the status code 404 in the header. Further investigation revealed that this only happens when the request is for a file. If you request a non-existent directory then you get the custom error page! For example, requesting mydomain.info/dummy.htm gives the error but requesting mydomain.info/dummy/ returns the custom error page.
The server is logging error AH01071 which is Primary script unknown for every File not found. error.
It appears that ModSecurity is enabled on the server because the logs record malicious requests being rejected, e.g. [client xxx.xxx.xxx.xxx] ModSecurity: Access denied with code 403 (phase 2). ... etc
Also, I recently changed to PHP 7.2 as recommended by the hosting provider. Changing back to 5.6 doesn't change the symptoms though.
Any ideas what is causing this? I have seen info that suggests perhaps a ProxyPass or ProxyErrorOverride might fix the problem, but I don't know where to set that up.
For the record, here is the complete htaccess, warts and all:
RewriteEngine on
# AddType TYPE/SUBTYPE EXTENSION
AddType audio/mpeg mp3
AddType video/mp4 mp4 m4v
# Add WWW
RewriteCond %{HTTP_HOST} ^mydomain\.info [NC]
RewriteRule ^(.*) https://www.mydomain.info/$1 [R=301,L,NE]
# Redirect for .COM
RewriteCond %{HTTP_HOST} mydomain\.com$ [NC]
RewriteRule ^/?(.*) https://www.mydomain.info/$1 [R=301,L,NE]
# Force HTTPS
RewriteEngine On
RewriteCond %{HTTPS} off
RewriteRule (.*) https://%{HTTP_HOST}%{REQUEST_URI} [R=301,L,NE]
# Home page canonicalization
RewriteCond %{THE_REQUEST} ^.*\/index\.htm\ HTTP/
RewriteRule ^(.*)index\.htm$ /$1 [R=301,L,NE]
# Removed page_missing.htm
Redirect 301 /page_missing.htm /new_page.htm#section_b
# Some content moved to sub-folder
Redirect 301 /extra_content.htm /extra/extra_content.htm
# Internally redirect all HTM & HTML URLs to PHP
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^(.*)\.(htm|html)$ /$1\.php
# Error 404 page
ErrorDocument 404 /error404.php
<IfModule mod_expires.c>
# Activate mod_expires for this directory
ExpiresActive on
# Default
ExpiresDefault "access plus 7 days"
# Default for actual documents
ExpiresByType text/html "access plus 15 minutes"
# cache CSS files for 7 days
ExpiresByType text/css "access plus 7 days"
# locally cache common resource types for 7 days
ExpiresByType image/jpg "access plus 7 days"
ExpiresByType image/jpeg "access plus 7 days"
ExpiresByType image/gif "access plus 7 days"
ExpiresByType image/png "access plus 7 days"
ExpiresByType application/pdf "access plus 7 days"
ExpiresByType audio/mpeg "access plus 7 days"
</IfModule>
