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Forum Discussion

goyogi's avatar
goyogi
Icon for Nimbostratus rankNimbostratus
Dec 08, 2017

Host header vulnerability

This interesting vulnerability was found with a simple redirect irule by injecting a bad actor site as a host header, the F5 will redirect based on the host header and not on the host within the URL ...
iRules
security
Stanislas_Piro2's avatar
Stanislas_Piro2
Icon for Cumulonimbus rankCumulonimbus
Dec 11, 2017

when you enter in the address bar the following URL :

 

https://foobar.com/mypath.php

the HTTP request is:

 

GET /mypath.php HTTP/1.1
Host: foobar.com
User-Agent: Mozilla .....
...

this is how HTTP works.

 

you can filter allowed host header values with this code:

 

when RULE_INIT {
    set static::allowed_hosts [list foobar.com www.foobar.com www.company.com]
}

when HTTP_REQUEST {
    if {[lsearch [string tolower [HTTP::host]] $static::allowed_hosts] != -1}
    HTTP::respond 301 Location "https://[HTTP::host][HTTP::uri]"
}