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bw447
bw447
New Member
July 5, 2016
Question

Encryption Using an Obsolete Cipher Suite, After CA cert and strong-crypto enable

  • July 5, 2016
  • 4 replies
  • 11914 views

I have DPi setup and running on one Policy on our cluster (2 3700D v5.2.4,build688).  The rule is only for my laptop.  After following the Cookbook steps on importing the Fortigate CA onto my laptop everything appears to be working very well. Safe search is working and I haven't ran into any other major problems except Skype on 365, but I believe it might be tied into the current situation I'm trying to solve.  On Chrome (again everything works well) I click on the SSL link in the URL and it shows me that Chrome verified the FortiGate CA.....  Then it says:

 

"Your connection to www.netflix.com is encrypted using an obsolete cipher suite.  The connection is encrypted using AEA_128_CBC, with HMAC-SHA1 for message authetnication and ECDHE_RSA as the key exchange mechanism.

 

 

 

If I lookup the same thing on my desktop (which doesn't hit a Policy that uses DPI) I don't get the obsolete cipher error.  I did connect to the CLI and ran the: "set strong-crypto enable" , but I still get the error.  Do I need to configure the Fortigate more?  

 

Any help would be appreciated!

 

Thanks in advance!

 

B

4 replies

kallbrandt
kallbrandt
New Member
July 5, 2016

Chrome is very rigid when it comes to certificates, and that is actually a good thing.

 

The solution is to not use the built-in certificates. They use old "easier" ciphers, for compliance reasons (I guess), and are there for test reasons only (imo). Since the Fortigate does a man-in-the-middle - That is: terminates the session from your laptop and open a new one to the webserver, bakes a new certificate for the site you are visiting and signs it with the Fortigate CA cert, you will not get a better cipher in the certificate then the Fortigate root one, no matter what settings you use. Hence the warning in Chrome.

 

If you have a PKI infrastructure running, use that. Import the CA certificate, and issue and import a sub-CA certificate to the Fortigate (NOT a plain SSL-certificate!). Or create your own CA and make sure all clients trust it. Anyway works. The important part to remember is that the certificate used for SLL-termination in the Fortigate need to have issuer rights (It needs to have the right to issue new certificates), wich makes the Fortigate a sub-CA/Issuer in the PKI infrastructure.

emnoc
emnoc
New Member
July 6, 2016

If you dump your ssl hellos you will see that negotiated cipher between you and the fortigate was  AEA_128_CBC, with HMAC-SHA1, chrome is just being ....."Chrome"

 

I bet you if you use a different  browser of set  Chrome to not Negotiated  that cipher than you would be okay. I'm also betting in your FortiOS the FortiGate  cert is a sha1 cert. I believe the  certificate pubkeysize was change to 2048bits in 5.2.6 irrc ( some one correct me I'm too lazy to find the release notes ;)

 

So if you craft  2k bit CSR have it sign by a external CA or a internal CA and report that into the fortigate  than you would be golden and reduce the obsolete  ciphers from the client to include any RC4 ciphers ( sha or md5 )

 

 

i would start by looking at your client browser

 

https://www.ssllabs.com/ssltest/viewMyClient.htmll

 

And by running test ssl against the  netfix site to learn more

https://testssl.sh/

 

 

pcraponi
pcraponi
New Member
July 6, 2016

Like said emnoc, try upgrade to 5.2.8. Versions after 5.2.5 has new ciphers.

 

regards,

Paulo R.

 

emnoc Expert Member  Total Posts : 3584Scores: 190Reward points: 0Joined: 3/20/2008Status: offline[/ul] Re: Encryption Using an Obsolete Cipher Suite, After CA cert and strong-crypto enable 10 hours ago (permalink)     0 If you dump your ssl hellos you will see that negotiated cipher between you and the fortigate was  AEA_128_CBC, with HMAC-SHA1, chrome is just being ....."Chrome"    I bet you if you use a different  browser of set  Chrome to not Negotiated  that cipher than you would be okay. I'm also betting in your FortiOS the FortiGate  cert is a sha1 cert. I believe the  certificate pubkeysize was change to 2048bits in 5.2.6 irrc ( some one correct me I'm too lazy to find the release notes ;)   So if you craft  2k bit CSR have it sign by a external CA or a internal CA and report that into the fortigate  than you would be golden and reduce the obsolete  ciphers from the client to include any RC4 ciphers ( sha or md5 )     i would start by looking at your client browser   https://www.ssllabs.com/ssltest/viewMyClient.htmll   And by running test ssl against the  netfix site to learn more https://testssl.sh/       PCNSE6,CCNP,FCNSP,FCESP,Linux+,CEH,ECSA,SCSA,SCNA,CISCA email/web Helpful Report AbuseForward  Quote   #3   pcraponi Quick Reply: (Open Full Version)        Paragraph Font Family Font Size                  Path: p   Preview    Submit Post     Home Â» All Forums Â» [link=https://forum.fortinet.com/tt.aspx?forumid=120][FortiGate / FortiOS UTM features][/link] Â» Web Filtering Â» Encryption Using an Obsolete Cipher Suite, After CA cert and strong-crypto enable Jump to:  Jump to - - - - - - - - - -  [FortiGate / FortiOS UTM features] - - - - AntiVirus - - - - Application Control - - - - Data Leak Prevention (DLP) - - - - Email filtering (AntiSPAM) - - - - Former Content Management Forum - - - - Intrusion Detection & Prevention - - - - Web Filtering [Fortinet Beta Programs] - - - - Beta Message Board - - - - FortiOS 5.4 Beta - - - - FortiClient 5.4 Beta - - - - FortiAnalyzer 5.4 Beta [Fortinet Services] - - - - FortiCloud IOC [Other FortiGate and FortiOS Topics] - - - - Firewall  - - - - Log & Report - - - - Miscellaneous -- FortiOS and FortiGate - - - - New Features -- FortiOS - - - - Routing and Transparent Mode - - - - System settings - - - - User and Authentication - - - - VPN [Other Fortinet Products] - - - - AscenLink - - - - Coyote Point - - - - FortiADC - - - - FortiAnalyzer - - - - FortiAP - - - - FortiAuthenticator - - - - FortiBalancer - - - - FortiBridge - - - - FortiCache - - - - FortiCamera & FortiRecorder - - - - FortiCarrier  - - - - FortiClient - - - - FortiConverter - - - - FortiCore - - - - FortiDB - - - - FortiDDOS - - - - FortiDirector - - - - FortiDNS - - - - FortiExplorer - - - - FortiGuard - - - - FortiMail - - - - FortiManager - - - - FortiPlanner - - - - FortiSandbox - - - - FortiScan - - - - FortiSwitch - - - - FortiToken - - - - FortiVoice - - - - FortiWeb - - - - FortiWiFi - - - - Meru (Wireless Infrastructure) [Forum Information & Miscellaneous Topics] - - - - Forum News - - - - Ideas for Forum Site - - - - Fortinet Cookbook - - - - Knowledge Base - - - - Technical -- non-FortiOS - - - - Miscellaneous -- non-technical      © 2016 APG vNext Commercial Version 5.5   Latest Posts    Re: FortiClient 5.4 on Windows 10 Connects but does not route Traffic over SSL VPN Re: How to configure EMAIL filter with external Exchange server Re: When is 5.4.1 going to drop? Re: Unable to establish vpn Re: run fortigate in vmware Re: run fortigate in vmware Automatic VPN if Off NET using Windows Credentials Re: Backup over SCP Re: run fortigate in vmware Re: New firewalls vs old [/ul] Active Posts    FortiClient 5.4 on Windows 10 Connects but does not route Traffic over SSL VPN How to configure EMAIL filter with external Exchange server When is 5.4.1 going to drop? Unable to establish vpn run fortigate in vmware Backup over SCP New firewalls vs old Encryption Using an Obsolete Cipher Suite, After CA cert and strong-crypto enable View Release Notes -> Document not found SSL Certificate Inspection, CA certificate and www.amazon.com [/ul] All FAQs    GUI Poll #1 [/ul] emnoc
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