WebSphere Application Server & Liberty

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  • 1.  About "Weak SSL/TLS Key Exchange"

    Posted Fri March 31, 2023 02:00 AM

    I operate some systems built using WebSphere Application Server and IBM HTTP Server.
    When I tested these systems with security scans (For example , Qualys Scan etc..), I sometimes received indications like "Weak SSL/TLS Key Exchange port xxxx/tcp over SSL". In fact, I do not operate such a key exchange, but it seems that the system settings allow communication using weak encryption.
    In order to avoid receiving these indications, I think it is necessary to add or change the setting values of WAS , IHS or both of them. 

    I have a question here.
    Specifically, what part of WAS or HTTP should I change?  Applying fix Pack? Changing parameters? (Which config file?)
    I would like to improve the result of security scan test  without affecting existing operations as much as possible. WAS , IHS versions are 8.5.5 - 9.0.5 .

    Please teach me .


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    Ken Iida
    Ken.Iida@kyndryl.com
    NagoyaJapan
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  • 2.  RE: About "Weak SSL/TLS Key Exchange"

    Posted Fri March 31, 2023 08:27 AM

    If you're scanning IHS, it's most likely complaining about RSA key exchange.

    If you have relatively recent fix packs, you can disable RSA key exchange pretty easily in IHS by updating httpd.conf:

    1.Remove SSLCipherSpec directives that explicitly enable RSA key exchange ciphers (Ciphers that begin with TLS_RSA)
    2. In fix packs 8.5.5.19-8.5.5.23 and 9.0.5.7-9.0.5.14 add SSLCipherSpec -RSA to each virtual host with SSLEnable

    If you are scanning WAS directly, it may be more complicated, as the weak key exchange could additionally refer to things like small DHE key sizes (which are dynamically generated).  It is probably best to open a support case if it's a WAS scan result.



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    Eric Covener
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  • 3.  RE: About "Weak SSL/TLS Key Exchange"

    Posted Sun April 02, 2023 09:39 PM

    Specifically, should I write the following and sequentially exclude the ciphers that I do not want to use?

    SSLCipherSpec ALL -SSL_RSA_WITH_RC4_128_MD5
    SSLCipherSpec ALL -SSL_RSA_WITH_RC4_128_SHA
    ・・・・・



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    Ken Iida
    Ken.Iida@kyndryl.com
    NagoyaJapan
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  • 4.  RE: About "Weak SSL/TLS Key Exchange"

    Posted Sun April 02, 2023 09:47 PM

    Assuming you have 8.5.5.19-8.5.5.23 or 9.0.5.7-9.0.5.14, I suggest removing any RSA ciphers you already have explicitly listed in httpd.conf, then setting "SSLCipherSpec -RSA" to remove the ones enabled by default.  In 8.5.5.25/9.0.5.15 and later, there are no default RSA ciphers enabled anymore (except in some special case on zOS where cannot be sure ECDHE will work)

    If your IHS is older than 8.5.5.19 or 9.0.5.7, there are more and more RSA ciphers that might be enabled by default the farther back you go.
    You can see them all with apachectl -t -DDUMP_SSL_CONFIG and remove them individually. with the syntax you showed.  

     



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    Eric Covener
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  • 5.  RE: About "Weak SSL/TLS Key Exchange"

    Posted Sun April 02, 2023 10:10 PM

    Thanks. I understand.



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    Ken Iida
    Ken.Iida@kyndryl.com
    NagoyaJapan
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  • 6.  RE: About "Weak SSL/TLS Key Exchange"

    Posted Wed April 05, 2023 12:16 AM

    Please tell me one more thing.

    In 8.5.5.25/9.0.5.15 and later RSA ciphers are disabled by default.
    By what method is it ? Is it written like that in the default httpd.conf?



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    Ken Iida
    Ken.Iida@kyndryl.com
    NagoyaJapan
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  • 7.  RE: About "Weak SSL/TLS Key Exchange"

    Posted Wed April 05, 2023 08:30 AM

    No, it is not via any configuration file change.

    It is always the case that prior to processing any SSLCipherSpec directives, there is a default set of ciphers enabled. It is a subset of the ciphers supported by the GSKit security library.

    In 8.5.5.24/9.0.5.15 (typo before) no RSA ciphers will be present in that initial default list. If the config happens to have explicit SSLCipherSpec directives that enable RSA KEX ciphers. they will continue to be used. See PH51473 (https://www.ibm.com/support/pages/apar/PH51473)  for more detail including issues unique to IHS on zOS.



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    Eric Covener
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  • 8.  RE: About "Weak SSL/TLS Key Exchange"

    Posted Thu April 06, 2023 12:50 PM

    For WebSphere Application Server, this too has a default set of Strong ciphers (in the Security > SSL Certificate and Key Management > SSL Configurations > CONFIG_NAME > Quality of Protection (QoP) Settings), and yes this might include some of the ciphers that use RSA (or possibly Diffie Hellman (DH)) ciphers that are flagged by the scanner.  In fact if you read the scan report, it likely shows which ciphers failed the test and what keysizes were returned with those tests (but it might be for either RSA or DH key sizes), and states that multiple tests against RSA, DH, and EC (Elliptical Curve) ciphers were likely run.

    But yes you could also disable the ciphers manually via the admin console if you don't want to use them.  You could also try to set the jdk.tls.disabledAlgorithms accordingly to use only the larger key sizes for RSA and DH (as well as setting the ephemeral key size settings -- https://www.ibm.com/docs/en/sdk-java-technology/8?topic=customization-customizing-size-ephemeral-diffie-hellman-keys ), but you'd have to decide what path you want to take as disabling the ciphers will also likely work similarly. 

    For a list of default ciphers in the IBM SDK, see here:  https://www.ibm.com/docs/en/sdk-java-technology/8?topic=suites-cipher
    For a technote on setting the ephemeral key size setting and the disabledAlgorithms settings: https://www.ibm.com/support/pages/node/6857359



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    MICHAEL SCHNEIDER
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