how to disable weak SSL ciphers?

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how to disable weak SSL ciphers?

Robert Feldman -X (robfeldm - Protingent Staffing at Cisco)

I work for Cisco and have a quick openssl-0.9.8o question.

Does openssl-0.9.8o provide a option to disable weak SSL ciphers?

I am looking for a configuration option or a runtime tool/option.

If these are not available, is there a compilation option?

 

I found the following potentially useful define in ssl/ssl.h and include/openssl/ssl.h:

 

#define SSL_DEFAULT_CIPHER_LIST     "AES:ALL:!aNULL:!eNULL:+RC4:@STRENGTH" /* low priority for RC4 */

 

I would prefer not to have to modify the openssl code to take care of this.

 

Thanks,

Robert

 

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how to disable weak SSL ciphers?

Robert Feldman -X (robfeldm - Protingent Staffing at Cisco)

Nessus and " openssl ciphers -v 'ALL:eNULL'" detect the following weak SSL ciphers on my test server:

 

NULL-SHA                SSLv3 Kx=RSA      Au=RSA  Enc=None      Mac=SHA1

NULL-MD5                SSLv3 Kx=RSA      Au=RSA  Enc=None      Mac=MD5

 

What configure options do I specify to rebuild openssl to compile out these weak SSL ciphers?

Specifying no-md5 should disable required ciphers such as RC4-MD5, which I do not want to do.

Is there an openssl config file or runtime tool to disable all ciphers with Enc=None?

 

Your feedback would be greatly appreciated.

 

Thanks,

Robert

 

 

 

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Re: how to disable weak SSL ciphers?

Patrick Patterson-3
On July 30, 2010 10:21:06 pm Robert Feldman -X (robfeldm - Protingent Staffing
at Cisco) wrote:

> Nessus and " openssl ciphers -v 'ALL:eNULL'" detect the following weak
> SSL ciphers on my test server:
>
>
>
> NULL-SHA                SSLv3 Kx=RSA      Au=RSA  Enc=None      Mac=SHA1
>
> NULL-MD5                SSLv3 Kx=RSA      Au=RSA  Enc=None      Mac=MD5
>
>
>
> What configure options do I specify to rebuild openssl to compile out
> these weak SSL ciphers?
>
> Specifying no-md5 should disable required ciphers such as RC4-MD5, which
> I do not want to do.
>
> Is there an openssl config file or runtime tool to disable all ciphers
> with Enc=None?
>
Don't rebuild OpenSSL - configure your application to only use ciphers that
comply with whatever security requirements you have. If this is Apache, you
can do this fairly simply by using the SSLCipherSuite httpd.conf directive. If
you wrote the application, then prior to accepting any connections, use the  
SSL_CTX_set_cipher_list() function to set everything up the way you want.

Have fun!

--
Patrick Patterson
President and Chief PKI Architect,
Carillon Information Security Inc.
http://www.carillon.ca
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Re: how to disable weak SSL ciphers?

Kyle Hamilton
In reply to this post by Robert Feldman -X (robfeldm - Protingent Staffing at Cisco)
You need '!aNULL:!eNULL:!LOW:!SSLv2:!EXPORT:!EXPORT56:FIPS:MEDIUM:HIGH:@STRENGTH" as the argument to SSL_CTX_set_cipher_list().

You can't get rid of MD5, as *everything* requires it.  If you get rid of it, TLS v1.0 won't work, SSLv3 won't work, and I don't even know about the TLS v1.1 stuff that's going into (appropriately) OpenSSL v1.1 (and backported to v1.0.1).

(Can we get TLS v1.2 in v1.2, and then start numbering based on the version of the protocol it speaks? ;) )

-Kyle H

On Mon, Aug 2, 2010 at 11:52 AM, Patrick Patterson <[hidden email]> wrote:

> On July 30, 2010 10:21:06 pm Robert Feldman -X (robfeldm - Protingent Staffing
> at Cisco) wrote:
>> Nessus and " openssl ciphers -v 'ALL:eNULL'" detect the following weak
>> SSL ciphers on my test server:
>>
>>
>>
>> NULL-SHA                SSLv3 Kx=RSA      Au=RSA  Enc=None      Mac=SHA1
>>
>> NULL-MD5                SSLv3 Kx=RSA      Au=RSA  Enc=None      Mac=MD5
>>
>>
>>
>> What configure options do I specify to rebuild openssl to compile out
>> these weak SSL ciphers?
>>
>> Specifying no-md5 should disable required ciphers such as RC4-MD5, which
>> I do not want to do.
>>
>> Is there an openssl config file or runtime tool to disable all ciphers
>> with Enc=None?
>>
> Don't rebuild OpenSSL - configure your application to only use ciphers that
> comply with whatever security requirements you have. If this is Apache, you
> can do this fairly simply by using the SSLCipherSuite httpd.conf directive. If
> you wrote the application, then prior to accepting any connections, use the
> SSL_CTX_set_cipher_list() function to set everything up the way you want.
>
> Have fun!
>
> --
> Patrick Patterson
> President and Chief PKI Architect,
> Carillon Information Security Inc.
> http://www.carillon.ca
> ______________________________________________________________________
> OpenSSL Project                                 http://www.openssl.org
> Development Mailing List                       [hidden email]
> Automated List Manager                           [hidden email]
>


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RE: how to disable weak SSL ciphers?

Tim Cloud
In reply to this post by Patrick Patterson-3
So, I have a question for this group as well, but it's in regards to this same issue.
What if you didn't write the application, and using the SSLCipherSuite is not an option as it's not running Apache?
Can someone just compile the FIPS compliant version of OpenSSL which should only allow strong ciphers?


Timothy Cloud
MSPRC Database Manager
Chickasaw Nation Industries

-----Original Message-----
From: [hidden email] [mailto:[hidden email]] On Behalf Of Patrick Patterson
Sent: Monday, August 02, 2010 1:52 PM
To: [hidden email]
Subject: Re: how to disable weak SSL ciphers?

On July 30, 2010 10:21:06 pm Robert Feldman -X (robfeldm - Protingent Staffing
at Cisco) wrote:

> Nessus and " openssl ciphers -v 'ALL:eNULL'" detect the following weak
> SSL ciphers on my test server:
>
>
>
> NULL-SHA                SSLv3 Kx=RSA      Au=RSA  Enc=None      Mac=SHA1
>
> NULL-MD5                SSLv3 Kx=RSA      Au=RSA  Enc=None      Mac=MD5
>
>
>
> What configure options do I specify to rebuild openssl to compile out
> these weak SSL ciphers?
>
> Specifying no-md5 should disable required ciphers such as RC4-MD5, which
> I do not want to do.
>
> Is there an openssl config file or runtime tool to disable all ciphers
> with Enc=None?
>
Don't rebuild OpenSSL - configure your application to only use ciphers that
comply with whatever security requirements you have. If this is Apache, you
can do this fairly simply by using the SSLCipherSuite httpd.conf directive. If
you wrote the application, then prior to accepting any connections, use the  
SSL_CTX_set_cipher_list() function to set everything up the way you want.

Have fun!

--
Patrick Patterson
President and Chief PKI Architect,
Carillon Information Security Inc.
http://www.carillon.ca
______________________________________________________________________
OpenSSL Project                                 http://www.openssl.org
Development Mailing List                       [hidden email]
Automated List Manager                           [hidden email]


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