Captive Portal redirection

[Zeihold_von_SSL]

Hello everybody, I have a question and hope you can help me. I have set up a captive portal and everythings works fine like I planned it. But there is one issue I ran into, that I didn' t plan with. If the traffic which triggers the captive portal is https traffic, then we get a certificate warning. Let me explain this: 1) I join the captive portal based wlan 2) I open a browser and surf to https://www.google.com 3) I get a certificate warning in the webbrowser 4) If I ignore this warning I' am redirected to the captive portal 5) If I authenticate myself with correct credentials I will be redirected to the original website. The thing is, that I want to get rid of the certificate warning. I found this little config switch wich allows me to choose the certificate I want to use: config user setting set auth-cert xxx end I tried it with our official thawte certificate but that didn' t help. So I tried some other certificates (but this will only help our employees and not other guests) but this didn' t work either. And then I found this page: http://kb.fortinet.com/kb/microsites/search.do?cmd=displayKC&docType=kc&externalId=FD30760&sliceId=1&docTypeID=DT_KCARTICLE_1_1&dialogID=38506158&stateId=0 This was nearly the situation that I have. So I tried this setting, because this could be a win win situation (it could solve my problem and could help to increase the security level of my guest wlan). config user setting set auth-secure-http enable end Sadly, I now get redirected to the gateway IP and STILL get a certificate warning (cause there is no matching certificate which includes the gateway ip). So I' am stuck here. Cause I can' t use this setting: config firewall policy edit <my_policy_ID> set auth-redirect-addr " my.fortigate.com" next end This is because we use address based policies and no identity based policies. So I' am searching for another way to get rid of the certificate warning for _all_ users. Is there anyone who might help me?

[Zeihold_von_SSL]

Okay, I have upgraded to OS 5.0.5 last night and it seems that Fortinet have implemented a (dirty) workaround. I have tried (with Google Chrome so far) to open https://www.google.de. I see an SSL error message but then a second browser tab pops up. In this tab the browser is trying to reach http://www.gstatic/<some_error_page> and shows the captive portal website. After I have authenticated myself using the captive portal both tabs are redirected to the original url. I have so test this with several other browsers and OS versions but for now it seems to work (for me).

[andrelhj]

Hello, I had a similar problem. I enabled secure authentication (HTTPS) through LDAP, to access a URL, for example: url.domain.com, the browser displays the alert invalid certificate. The problem was solved by buying a certificate for the sub-domain: url.domain.com. You can buy a wildcard certificate (* .domain.com) and can be installed on multiple servers. You will receive an SSL certificate and the intermediate certificate. You have up to seven days to test and return the money in case of failure. The steps were as follows: 1) System> Certificates> Local Certificates, I generate a new certificate. 2) Send the CSR generated certificate to the vendor. 3) It will return an SSL certificate and intermediate certificates. 4) Install the intermediate certificate in System> Certificates> CA Certificates. 5) Install the SSL certificate in System> Certificates> Local Certificates. 6) Use the options "auth-cert" and "auth-redirect-addr" in the firewall policy:

config firewall policy
    edit <policyID>
    set auth-cert CustomCert
    set auth-redirect-addr url.domain.com
end

It worked for my case and I hope it helps somebody else.

I'm using the FortiOS version 5.2.2. URL for reference:

[ul]

https://stuff.purdon.ca/?page_id=171

http://kb.fortinet.com/kb/microsites/search.do?cmd=displayKC&docType=kc&externalId=FD30760&sliceId=1...[/ul]

I can not tell what implications this type of configuration has security and what are the safe use of recommendations for certificates. Welcome to contribute.

Not knowing it was impossible He Dit It.

[Bernard_Pauwels]

Since HSTS this is not only a warning anymore but full blocking of the access. The workaround now is to first surf to a HTTP website, to avoid the HTTPS to be activated, where Chrome would detect that it is not the original certificate.

With Chrome on a Windows PC, just typing "badidea" stops the HSTS from blocking further action. However I could not start this "badidea" on a smartphone.

[dbert84]

I think we need a real solution to this, provided by Fortinet

No normal user will know to browse to a http site to bypass this issue without training, they will just come to us and say 'it doesn't work!'

Also its getting harder and hard to find a website that isn't redirected to https anyway, more than 50% of the web is HTTPS now - google is 77% https traffic

[Lucas_Piris]

I totally agree with dbert84, we need a solution provided by Fortinet, simply saying to access an HTTP site first is not solution. I have a case exactly like this and the engineer's recommendation was this.

[flex10 · Accepted solution]

Here's the solution provided by FortiNet-Support, successfully tested on my FGT 500D with FortiOS 5.4.4:

- set a publicly trusted SSL-certificate under "User & Device" -> "Authentication Settings" which includes the common-name you wish to use (for example: captive.domain.com)

- create a public DNS-entry "captive.domain.com" which points to the internal IP of your captive portal.

- go to the CLI and enter the commands below:

# config firewall auth-portal

# set portal-addr captive.domain.com

# end

Now users will be redirected to https://captive.domain.com:1003 without any ssl-errors 

[Baptiste]

Hi 

this works well with only one subnet/interface

I want to use captive portal and redirection for LAN & Wifi (mode tunnel) on differents subnets.

I tried this

config firewall policy edit set auth-cert CustomCert set auth-redirect-addr url.domain.com end

but I'm still redirect to the one set here :

config firewall auth-portal set portal-addr captive.domain.comend

Edit :

If I unset global auth portal :

config firewall auth-portal unset portal-addr

each subnet is redirect to FGT IP interface, not to FQDN.

Test on 100D running 5.2.10

[Baptiste]

I got an answer by TAC :

Please note that these are two different and separate authentication methods. Captive portal takes precedence over any other authentication, therefore captive portal authentication is done first. Captive portal has two "modes": - Internal captive portal (hosted directly on the FortiGate) - External captive portal (redirect to external website => external website gathers login details of users and sends them back to FortiGate to verify) The internal captive portal uses either the interface's IP (default), or the FQDN configured in "config firewall auth-portal". => This is why you see the user traffic being redirected to "captive.domain.com" or the interface IP. Authentication redirection in a policy is only triggered when traffic matches this policy and authentication is needed. At that point, redirection to the URL specified in "auth-redirect-addr" happens. I hope that clarifies the situation. I would recommend to keep either the interface-captive portal, or the policy authentication-redirect, and remove the other. (if you want the FortiGate to redirect to the URL specified in the policy, make sure to remove the captive portal from the interface)

So I remove captive portal mode from interface, set auth-redirect on each policy, create dns entry for each

it's working for both LAN & Wifi without any certificate warning (I bought a multi-domain certificate)

[Mazino]

Baptiste wrote:

I got an answer by TAC :

Please note that these are two different and separate authentication methods. Captive portal takes precedence over any other authentication, therefore captive portal authentication is done first. Captive portal has two "modes": - Internal captive portal (hosted directly on the FortiGate) - External captive portal (redirect to external website => external website gathers login details of users and sends them back to FortiGate to verify) The internal captive portal uses either the interface's IP (default), or the FQDN configured in "config firewall auth-portal". => This is why you see the user traffic being redirected to "captive.domain.com" or the interface IP. Authentication redirection in a policy is only triggered when traffic matches this policy and authentication is needed. At that point, redirection to the URL specified in "auth-redirect-addr" happens. I hope that clarifies the situation. I would recommend to keep either the interface-captive portal, or the policy authentication-redirect, and remove the other. (if you want the FortiGate to redirect to the URL specified in the policy, make sure to remove the captive portal from the interface)

So I remove captive portal mode from interface, set auth-redirect on each policy, create dns entry for each

it's working for both LAN & Wifi without any certificate warning (I bought a multi-domain certificate)

Hi Baptiste, When you said you test it using WiFi, is it using Mobile Browser or Laptop Browser? Because I'm having the same problem, but the certificate issue only occurs using Mobile browsers. When I tried to access the SSID with Captive Portal using Laptop, the certificate issue doesn't occurs and it redirects me straight to the Captive Portal. But when I tried to connect to the SSID using Mobile device, I got an certificate issue before I got into the Captive Portal. Any thought guys? Regards

[FortiBoris_FTNT]

flex10 wrote:

Here's the solution provided by FortiNet-Support, successfully tested on my FGT 500D with FortiOS 5.4.4:

- set a publicly trusted SSL-certificate under "User & Device" -> "Authentication Settings" which includes the common-name you wish to use (for example: captive.domain.com)

- create a public DNS-entry "captive.domain.com" which points to the internal IP of your captive portal.

- go to the CLI and enter the commands below:

# config firewall auth-portal

# set portal-addr captive.domain.com

# end

Now users will be redirected to https://captive.domain.com:1003 without any ssl-errors 

Hey there, thanks a lot that works really great!

I just wanted to add that you "don't" need to add a publicly resolvable DNS entry with your internal IP (i would say that this isn't security best practices and provide unneeded information outside) Here is what I've done in order to have only "internal" resolution on my portal FQDN mapped to a let's encrypt certificate:

config system dns-database edit "yourdomain.name" set domain "yourdomain.name" set authoritative disable set forwarder "internal DNS server or FortiGate or Forwarder" config dns-entry edit 1 set hostname "captive" set ip YOUR.INTERNAL.IP.ADDRESS (192.168.168.254 or whatever the captive portal is on) end

My certificate is mapped the captive.mydomain.name common name and is the certificate used in my user auth settings on the fortigate (as you've provided).

Thanks,

Kind regards,

Boris