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14755
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Expressway Weak SSL/TLS Key Exchange Issue

fdharmawan
Level 4
Level 4

‎06-07-2022 09:10 PM - edited ‎06-07-2022 09:12 PM

Hi Team,

 

Recently I got a report from my security team, stating that there is Weak SSL/TLS Key Exchange on our expressway deployment. The report is generated from Qualys. The result said this:

PROTOCOL NAME   GROUP                     KEY-SIZE   FORWARD-SECRET   CLASSICAL-STRENGTH   QUANTUM-STRENGTH
TLSv1.2                   ECDHE secp192r1   192            yes                             96                                   low

 

On the solution tab of the report, it is stated that:

Change the SSL/TLS server configuration to only allow strong key exchanges.

 

On Maintenance -> Security -> Ciphers, here are the entry on the ciphers:

EECDH:EDH:HIGH:-AES256+SHA:!MEDIUM:!LOW:!3DES:!MD5:!PSK:!eNULL:!aNULL

 

Here are the output when I issue xconfiguration // ciphers command:

xconfiguration // ciphers
*c xConfiguration Ciphers ForwardProxyTLSCiphers Value: "EECDH:EDH:HIGH:-AES256+SHA:!MEDIUM:!LOW:!3DES:!MD5:!PSK:!eNULL:!aNULL"
*c xConfiguration Ciphers ForwardProxyTLSProtocol Value: "minTLSv1.2"
*c xConfiguration Ciphers HTTPSCiphers Value: "EECDH:EDH:HIGH:-AES256+SHA:!MEDIUM:!LOW:!3DES:!MD5:!PSK:!eNULL:!aNULL"
*c xConfiguration Ciphers HTTPSProtocol Value: "minTLSv1.2"
*c xConfiguration Ciphers RemoteSyslog1TLSCiphers Value: "ALL"
*c xConfiguration Ciphers RemoteSyslog1TLSProtocol Value: "minTLSv1.0"
*c xConfiguration Ciphers RemoteSyslog2TLSCiphers Value: "ALL"
*c xConfiguration Ciphers RemoteSyslog2TLSProtocol Value: "minTLSv1.0"
*c xConfiguration Ciphers RemoteSyslog3TLSCiphers Value: "ALL"
*c xConfiguration Ciphers RemoteSyslog3TLSProtocol Value: "minTLSv1.0"
*c xConfiguration Ciphers RemoteSyslog4TLSCiphers Value: "ALL"
*c xConfiguration Ciphers RemoteSyslog4TLSProtocol Value: "minTLSv1.0"
*c xConfiguration Ciphers ReverseProxyTLSCiphers Value: "EECDH:EDH:HIGH:-AES256+SHA:!MEDIUM:!LOW:!3DES:!MD5:!PSK:!eNULL:!aNULL"
*c xConfiguration Ciphers ReverseProxyTLSProtocol Value: "minTLSv1.2"
*c xConfiguration Ciphers SIPTLSCiphers Value: "EECDH:EDH:HIGH:-AES256+SHA:!MEDIUM:!LOW:!3DES:!MD5:!PSK:!eNULL:+ADH"
*c xConfiguration Ciphers UcClientTLSCiphers Value: "EECDH:EDH:HIGH:-AES256+SHA:!MEDIUM:!LOW:!3DES:!MD5:!PSK:!eNULL:!aNULL"
*c xConfiguration Ciphers UcClientTLSProtocol Value: "minTLSv1.2"
*c xConfiguration Ciphers XCPTLSCiphers Value: "EECDH:EDH:HIGH:-AES256+SHA:!MEDIUM:!LOW:!3DES:!MD5:!PSK:!eNULL:!aNULL"
*c xConfiguration Ciphers XCPTLSProtocol Value: "minTLSv1.2"
*c xConfiguration Ciphers sshd_ciphers Value: "aes256-gcm@openssh.com,aes128-gcm@openssh.com,aes256-ctr,aes192-ctr,aes128-ctr,aes256-cbc,aes192-cbc,aes128-cbc"
*c xConfiguration Ciphers sshd_kex Value: "ecdh-sha2-nistp521,ecdh-sha2-nistp384,ecdh-sha2-nistp256,diffie-hellman-group-exchange-sha256,diffie-hellman-group14-sha1"
*c xConfiguration Ciphers sshd_macs Value: "hmac-sha2-512,hmac-sha2-256,hmac-sha1"
*c xConfiguration Ciphers sshd_pfwd_ciphers Value: "aes256-ctr"
*c xConfiguration Ciphers sshd_pfwd_kexalgorithms Value: "ecdh-sha2-nistp384"
*c xConfiguration Ciphers sshd_pfwd_pubkeyalgorithms Value: "x509v3-sign-rsa"
*c xConfiguration Authentication ADS CipherSuite: "HIGH:MEDIUM:!ADH:!aNULL:!eNULL:-AES128-SHA256:@STRENGTH"

 

I am running 12.5.4 on the expressway. May I know how to resolve it? Thank you.

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35 Replies 35

Roger Kallberg
VIP
VIP

‎06-07-2022 10:32 PM

Not as such direct related to your question at hand, but I would strongly recommend you to upgrade your Expressways to 14.0.6 or even better 14.0.7 as there are a number of serious security defects that won’t be fixed in any other releases. Besides that the version that you are using is getting quite old at this point.



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fdharmawan
Level 4
Level 4
In response to Roger Kallberg

‎06-08-2022 01:14 AM

Hi Roger,

 

Thank you for the reply. Let me arrange an upgrade of the expressway and see how it goes. Thanks.

0 Helpful

Roger Kallberg
VIP
VIP
In response to fdharmawan

‎06-08-2022 01:42 AM - edited ‎06-08-2022 01:42 AM

FYI these are the settings that we have for ciphers on one of our Expw that is running 14.0.7.

image.png

From what I know we have not altered these, they all should be at their default.



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0 Helpful

Roger Kallberg
VIP
VIP
In response to fdharmawan

‎06-08-2022 01:46 AM

Same output from xconfig.

xconfiguration // ciphers
*c xConfiguration Ciphers HTTPSCiphers Value: "EECDH:EDH:HIGH:-AES256+SHA:!MEDIUM:!LOW:!3DES:!MD5:!PSK:!eNULL:!aNULL:!aDH"
*c xConfiguration Ciphers HTTPSProtocol Value: "minTLSv1.2"
*c xConfiguration Ciphers LDAPTLSCiphers Value: "EECDH:EDH:HIGH:-AES256+SHA:!MEDIUM:!LOW:!3DES:!MD5:!PSK:!eNULL:!aNULL:!aDH"
*c xConfiguration Ciphers LDAPTLSProtocol Value: "minTLSv1.2"
*c xConfiguration Ciphers RemoteSyslog1TLSCiphers Value: "ALL:!aDH"
*c xConfiguration Ciphers RemoteSyslog1TLSProtocol Value: "minTLSv1.0"
*c xConfiguration Ciphers RemoteSyslog2TLSCiphers Value: "ALL:!aDH"
*c xConfiguration Ciphers RemoteSyslog2TLSProtocol Value: "minTLSv1.0"
*c xConfiguration Ciphers RemoteSyslog3TLSCiphers Value: "ALL:!aDH"
*c xConfiguration Ciphers RemoteSyslog3TLSProtocol Value: "minTLSv1.0"
*c xConfiguration Ciphers RemoteSyslog4TLSCiphers Value: "ALL:!aDH"
*c xConfiguration Ciphers RemoteSyslog4TLSProtocol Value: "minTLSv1.0"
*c xConfiguration Ciphers ReverseProxyTLSCiphers Value: "EECDH:EDH:HIGH:-AES256+SHA:!MEDIUM:!LOW:!3DES:!MD5:!PSK:!eNULL:!aNULL:!aDH"
*c xConfiguration Ciphers ReverseProxyTLSProtocol Value: "minTLSv1.2"
*c xConfiguration Ciphers SIPTLSCiphers Value: "EECDH:EDH:HIGH:-AES256+SHA:!MEDIUM:!LOW:!3DES:!MD5:!PSK:!eNULL:+ADH"
*c xConfiguration Ciphers SMTPTLSCiphers Value: "EECDH:EDH:HIGH:-AES256+SHA:!MEDIUM:!LOW:!3DES:!MD5:!PSK:!eNULL:!aNULL:!aDH"
*c xConfiguration Ciphers SMTPTLSProtocol Value: "minTLSv1.2"
*c xConfiguration Ciphers TMSProvisioningTLSCiphers Value: "EECDH:EDH:HIGH:-AES256+SHA:!MEDIUM:!LOW:!3DES:!MD5:!PSK:!eNULL:!aNULL:!aDH"
*c xConfiguration Ciphers TMSProvisioningTLSProtocol Value: "minTLSv1.2"
*c xConfiguration Ciphers UcClientTLSCiphers Value: "EECDH:EDH:HIGH:-AES256+SHA:!MEDIUM:!LOW:!3DES:!MD5:!PSK:!eNULL:!aNULL:!aDH"
*c xConfiguration Ciphers UcClientTLSProtocol Value: "minTLSv1.2"
*c xConfiguration Ciphers XCPTLSCiphers Value: "EECDH:EDH:HIGH:-AES256+SHA:!MEDIUM:!LOW:!3DES:!MD5:!PSK:!eNULL:!aNULL:!aDH"
*c xConfiguration Ciphers XCPTLSProtocol Value: "minTLSv1.2"
*c xConfiguration Ciphers sshd_ciphers Value: "aes256-gcm@openssh.com,aes128-gcm@openssh.com,aes256-ctr,aes192-ctr,aes128-ctr"
*c xConfiguration Ciphers sshd_kex Value: "ecdh-sha2-nistp256,diffie-hellman-group14-sha256,diffie-hellman-group14-sha1"
*c xConfiguration Ciphers sshd_macs Value: "hmac-sha2-512,hmac-sha2-256,hmac-sha1"
*c xConfiguration Ciphers sshd_pfwd_ciphers Value: "aes256-ctr"
*c xConfiguration Ciphers sshd_pfwd_kexalgorithms Value: "ecdh-sha2-nistp384"
*c xConfiguration Ciphers sshd_pfwd_pubkeyalgorithms Value: "x509v3-sign-rsa"
*c xConfiguration Authentication ADS CipherSuite: "HIGH:MEDIUM:!ADH:!aNULL:!eNULL:-AES128-SHA256:@STRENGTH"

OK


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Vinod16
Level 1
Level 1

‎06-09-2022 04:21 AM

@fdharmawan 

 

To mitigate this, We have to manually change the SIP TLS Diffie-Hellman key size from the default 1024 bits, to at least 2048.

You can also refer below guide for the same at page 68 (Point 8):

https://www.cisco.com/c/en/us/td/docs/voice_ip_comm/expressway/admin_guide/X14-0/exwy_b_cisco-expressway-administrator-guide.pdf



For this you can login to CLI of concerned node as admin & run the command: “xconfiguration SIP Advanced SipTlsDhKeySize: 2048”

You can also refer below guide for the same at page 71
https://www.cisco.com/c/dam/en/us/td/docs/voice_ip_comm/expressway/admin_guide/Cisco-Expressway-Administrator-Guide-X12-6.pdf

For this you can login to CLI of concerned node as admin & run the command: xconfiguration SIP Advanced SipTlsDhKeySize: 2048

Hope this helps.

fdharmawan
Level 4
Level 4
In response to Vinod16

‎06-20-2022 07:29 AM

Hi Vinod,

 

Thank you for your reply. I tried to apply it, but somehow still got detected by the system. Even though the DH key is now 2048.

0 Helpful

fdharmawan
Level 4
Level 4

‎06-22-2022 08:52 AM

Update:

 

I found that secp192r1 is actually not a cipher, it is a key exchange.

Key Exchange.PNG
 
On web GUI, I found this setting.
SSH Key.PNG
 
Here is what I found on the CLI

xConfiguration Ciphers sshd_kex Value: "ecdh-sha2-nistp521,ecdh-sha2-nistp384,ecdh-sha2-nistp256,diffie-hellman-group-exchange-sha256,diffie-hellman-group14-sha1"

 

I did not find any secp192r1. May I know how to remove it? Thanks.

0 Helpful

Vinod16
Level 1
Level 1
In response to fdharmawan

‎06-26-2022 08:09 AM

I have already raised a case with cisco for the same, they are
investigating and checking with the bug owner for a solution.
0 Helpful

brunofsm21
Level 1
Level 1
In response to Vinod16

‎06-29-2022 02:57 AM

Hi,

 

any update on the case?

 

 

thanks.

0 Helpful

Vinod16
Level 1
Level 1
In response to brunofsm21

‎06-29-2022 03:06 AM

Cisco team working internally.

fdharmawan
Level 4
Level 4
In response to Vinod16

‎07-01-2022 12:28 AM

Hi Vinod,

 

Got any words back from TAC?

0 Helpful

Vinod16
Level 1
Level 1
In response to fdharmawan

‎07-01-2022 04:07 AM

No response yet, they are internally investing solution for this vul .
0 Helpful

Vinod16
Level 1
Level 1
In response to fdharmawan

‎07-03-2022 02:28 AM

Finally cisco release bug for this Vulnerability which is now publicly visible.

 

https://bst.cloudapps.cisco.com/bugsearch/bug/CSCwb96116

 

Now they are internally working to provide workaround/fixed release for this bug.

0 Helpful

brunofsm21
Level 1
Level 1

‎06-30-2022 01:22 AM

Hi,

 

"Current we have the following opened defect: https://bst.cloudapps.cisco.com/bugsearch/bug/CSCwb96116, which has been opened to address this issue but there is no workaround, so it is not possible to allow weak cypher use or make this change, and also Expressway upgrade will not solve the problem"

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