Server 4.x violates RFC 7465 by offering RC4 as cipher

Originator:pepi.zawodsky
Number:rdar://22761190 Date Originated:18-Sep-2015 08:33 PM
Status:Open Resolved:
Product:OS X Server Product Version:5.0.x
Classification:Security Reproducible:Always
 
Summary:
Server 5.0.x violates RFC 7465 by offering RC4 as cipher

Steps to Reproduce:
Configure any OS X Service with TLS. Test offered service suites, for example with nmap.

HTTPS: nmap --script ssl-cert,ssl-enum-ciphers -p 443 osx.example.com
But the same issue applies for ANY service that is offered by ANY OS X Server version. This includes XMPP, Web, Wiki, Email, Profile manager, anything. (Calendar and Contacts are currently completely broken due to a failure of Server.app to configure the Proxyservice but they would also be vulnerable if that wasn't the case.)

Expected Results:
TLS Handshake must fail.

Actual Results:
OS X happily offers insecure RC4 cipher suite which violates TLS standards 1.0, 1.1, 1.2.

Regression:
This should have been fixed in Server 4.0.x, 4.1.x already. It is still present in Server 5.0.x running on any of Yosemite or El Capitan.

Notes:
RFC 7465
https://tools.ietf.org/html/rfc7465

TLS clients MUST NOT include RC4 cipher suites in the ClientHello message.
TLS servers MUST NOT select an RC4 cipher suite when a TLS client sends such a cipher suite in the ClientHello message.

Comments


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