ModSecurity blocks access to the website: Failed to access DBM file

Symptoms

• ModSecurity blocks access to the file with the following errors in /var/log/modsecurity_audit.log:

  Message: collections_remove_stale: Failed to access DBM file "/var/cache/modsecurity/apache-global": Permission denied
  Message: collections_remove_stale: Failed to access DBM file "/var/cache/modsecurity/apache-ip": Permission denied

Cause

Content of the directory as follows:

# ls -la /var/cache/modsecurity/
drwxr-x— 2 root root 4096 May 4 15:12 .
drwx—— 10 root root 4096 Apr 15 10:52 …

Or entire directory is missing:

# ls -la /var/cache/modsecurity/
ls: cannot access /var/cache/modsecurity/: No such file or directory

Corrupted ModSecurity cache.

Resolution

1. Login server via SSH

2. Re-create directory if missing and set up proper permissions/ownership:

   # mkdir /var/cache/modsecurity/

   # chmod 750 /var/cache/modsecurity/

   # chown apache:root /var/cache/modsecurity/

3. Fix permissions and re-create files:

   # chown apache:root /var/cache/modsecurity/./

   # chmod 755 /var/cache/modsecurity/../

   # cd /var/cache/modsecurity/

   # touch apache-global.dir && chown apache:apache apache-global.dir && chmod 640 apache-global.dir

   # touch apache-global.pag && chown apache:apache apache-global.pag && chmod 640 apache-global.pag

   # touch apache-ip.dir && chown apache:apache apache-ip.dir && chmod 640 apache-ip.dir

   # touch apache-ip.pag && chown apache:apache apache-ip.pag && chmod 640 apache-ip.pag

4. (Additional step incase SELinux is in use)

   # chcon -R -t httpd_cache_t /var/cache/modsecurity