After removing CBC ciphers in the httpd-ssl.conf on the Access Gateway, some are still present
Article ID: 381051
Updated On:
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Issue/Introduction
After removing CBC ciphers in the httpd-ssl.conf on the Access Gateway, some are still present.
The default SSLCipherSuite
SSLCipherSuite ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305:ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:DHE-RSA-AES128-GCM-SHA256:DHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-AES128-SHA256:ECDHE-RSA-AES128-SHA256:ECDHE-ECDSA-AES128-SHA:ECDHE-RSA-AES256-SHA384:ECDHE-RSA-AES128-SHA:ECDHE-ECDSA-AES256-SHA384:ECDHE-ECDSA-AES256-SHA:ECDHE-RSA-AES256-SHA:DHE-RSA-AES128-SHA256:DHE-RSA-AES128-SHA:DHE-RSA-AES256-SHA256:DHE-RSA-AES256-SHA:ECDHE-ECDSA-DES-CBC3-SHA:ECDHE-RSA-DES-CBC3-SHA:EDH-RSA-DES-CBC3-SHA:AES128-GCM-SHA256:AES256-GCM-SHA384:AES128-SHA256:AES256-SHA256:AES128-SHA:AES256-SHA:DES-CBC3-SHA:!DSS:!3DES
After removing the CBC ciphers it looks like this:
SSLCipherSuite ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305:ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:DHE-RSA-AES128-GCM-SHA256:DHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-AES128-SHA256:ECDHE-RSA-AES128-SHA256:ECDHE-ECDSA-AES128-SHA:ECDHE-RSA-AES256-SHA384:ECDHE-RSA-AES128-SHA:ECDHE-ECDSA-AES256-SHA384:ECDHE-ECDSA-AES256-SHA:ECDHE-RSA-AES256-SHA:DHE-RSA-AES128-SHA256:DHE-RSA-AES128-SHA:DHE-RSA-AES256-SHA256:DHE-RSA-AES256-SHA:AES128-GCM-SHA256:AES256-GCM-SHA384:AES128-SHA256:AES256-SHA256:AES128-SHA:!DSS:!3DES
Environment
Applies to Access Gateway R12.8 Any
Any OS
Cause
Nmap is using standard cipher names in its return data.
The Access Gateway uses OpenSSL to apply its Cipher Suite. OpenSSL has its own cipher references that can differ from the standard cipher references.
For example:
nmap returns this name below, with CBC in it.
TLS_DHE_RSA_WITH_AES_128_CBC_SHA
But you don't see this name as part of the SSLCipherSuite.
Since OpenSSL actually refers to it as
DHE-RSA-AES128-SHA
As it has no "CBC" in the SSLCipherSuite list, it was not removed and nmap will still list out CBC ciphers.
Starting Nmap 6.40 ( http://nmap.org ) at 2024-10-31 20:15 UTC
Nmap scan report for server.domain.com (###.###.###.###)
Host is up (0.0010s latency).
rDNS record for ###.###.###.###: server.domain.com
PORT STATE SERVICE
443/tcp open https
| ssl-enum-ciphers:
| TLSv1.1:
| ciphers:
| TLS_DHE_RSA_WITH_AES_128_CBC_SHA - strong
| TLS_DHE_RSA_WITH_AES_256_CBC_SHA - strong
| TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA - strong
| TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA - strong
| TLS_RSA_WITH_AES_128_CBC_SHA - strong
| compressors:
| NULL
| TLSv1.2:
| ciphers:
| TLS_DHE_RSA_WITH_AES_128_CBC_SHA - strong
| TLS_DHE_RSA_WITH_AES_128_CBC_SHA256 - strong
| TLS_DHE_RSA_WITH_AES_128_GCM_SHA256 - strong
| TLS_DHE_RSA_WITH_AES_256_CBC_SHA - strong
| TLS_DHE_RSA_WITH_AES_256_CBC_SHA256 - strong
| TLS_DHE_RSA_WITH_AES_256_GCM_SHA384 - strong
| TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA - strong
| TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256 - strong
| TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 - strong
| TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA - strong
| TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384 - strong
| TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 - strong
| TLS_RSA_WITH_AES_128_CBC_SHA - strong
| TLS_RSA_WITH_AES_128_CBC_SHA256 - strong
| TLS_RSA_WITH_AES_128_GCM_SHA256 - strong
| TLS_RSA_WITH_AES_256_CBC_SHA256 - strong
| TLS_RSA_WITH_AES_256_GCM_SHA384 - strong
| compressors:
| NULL
|_ least strength: strong
Nmap done: 1 IP address (1 host up) scanned in 0.43 seconds
Resolution
In order to remove all the CBC references from the nmap results, please refer to the OpenSSL reference linked below to map the nmap name to the name used in the SSLCipherSuite so it can be removed.
https://docs.openssl.org/master/man1/openssl-ciphers/#cipher-suite-names
Using the previous example
nmap returns this name below, with CBC in it.
TLS_DHE_RSA_WITH_AES_128_CBC_SHA
But you don't see this name as part of the SSLCipherSuite since OpenSSL actually refers to it as
DHE-RSA-AES128-SHA
Removing DHE-RSA-AES128-SHA from the SSLCipherSuite will remove the TLS_DHE_RSA_WITH_AES_128_CBC_SHA from the nmap results.
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