1 %%\subsection{Intercepting proxy solutions and reverse proxies}
3 Within enterprise networks and corporations with increased levels of paranoia or at least some defined security requirements it is common \textbf{not} to allow direct connections to the public internet.
5 For this reason proxy solutions are deployed on corporate networks to intercept and scan the traffic for potential threats within sessions.
7 For encrypted traffic there are four options:
10 \item Block the connection because it cannot be scanned for threats.
11 \item Bypass the threat-mitigation and pass the encrypted session to the client, which results in a situation where malicious content is transferred directly to the client without visibility to the security system.
12 \item Intercept (i.e. terminate) the session at the proxy, scan there and re-encrypt the session towards the client (effectively MITM).
13 \item Deploy special Certificate Authorities to enable Deep Packet Inspection on the wire.
16 While the latest solution might be the most "up to date", it arises a new front in the context of this paper, because the most secure part of a client's connection could only be within the corporate network, if the proxy-server handles the connection to the destination server in an insecure manner.
18 Conclusion: Don't forget to check your proxy solutions SSL-capabilities. Also do so for your reverse proxies!
20 %% ----------------------------------------------------------------------
22 As of squid-3.2.7 (01 Feb 2013) there is support for the OpenSSL NO\_Compression option within squid config (CRIME attack) and if you combine that in the config file, with an enforcement of the server cipher preferences (BEAST Attack) you are safe.
25 \paragraph*{squid.conf}
28 options=NO_SSLv2,NO_TLSv1,NO_Compression,CIPHER_SERVER_PREFERENCE
29 cipher=%*\cipherStringB*)
32 \paragraph*{squid.conf}
33 %% http://forum.pfsense.org/index.php?topic=63262.0
36 NO_SSLv2 Disallow the use of SSLv2
37 NO_SSLv3 Disallow the use of SSLv3
38 NO_TLSv1 Disallow the use of TLSv1.0
39 NO_TLSv1_1 Disallow the use of TLSv1.1
40 NO_TLSv1_2 Disallow the use of TLSv1.2
42 Always create a new key when using temporary/ephemeral
46 \todo{Patch here? Definitely working for 3.2.6!}
47 For squid Versions before 3.2.7 use this patch against a vanilla source-tree:
50 --- support.cc.ini 2013-01-09 02:41:51.000000000 +0100
51 +++ support.cc 2013-01-21 16:13:32.549383848 +0100
53 "NO_TLSv1_2", SSL_OP_NO_TLSv1_2
56 +#ifdef SSL_OP_NO_COMPRESSION
58 + "NO_Compression", SSL_OP_NO_COMPRESSION
67 %% ----------------------------------------------------------------------
68 \subsubsection{Bluecoat}
69 %% https://kb.bluecoat.com/index?page=content&id=KB5549
70 \subsubsection{Tested with Versions}
75 BlueCoat Proxy SG Appliances can be used as forward and reverse proxies. The reverse proxy feature is rather under-developed, and while it is possible and supported, there only seems to be limited use of this feature "in the wild" - nonetheless there are a few cipher suites to choose from, when enabling SSL features.
77 \paragraph*{Only allow TLS 1.0,1.1 and 1.2 protocols:}
81 $(config ssl)edit ssl-device-profile default
82 $(config device-profile default)protocol tlsv1 tlsv1.1 tlsv1.2
86 \paragraph*{Select your accepted cipher-suites:}
89 Enter configuration commands, one per line. End with CTRL-Z.
90 $(config)proxy-services
91 $(config proxy-services)edit ReverseProxyHighCipher
92 $(config ReverseProxyHighCipher)attribute cipher-suite
93 Cipher# Use Description Strength
94 ------- --- ----------------------- --------
95 1 yes AES128-SHA256 High
96 2 yes AES256-SHA256 High
97 3 yes AES128-SHA Medium
99 5 yes DHE-RSA-AES128-SHA High
100 6 yes DHE-RSA-AES256-SHA High
102 13 yes EXP-RC2-CBC-MD5 Export
104 Select cipher numbers to use, separated by commas: 2,5,6
108 The same protocols are available for forward proxy settings and should be adjusted accordingly:
109 In your local policy file add the following section:
112 DENY server.connection.negotiated_ssl_version=(SSLV2, SSLV3)
115 Disabling protocols and ciphers in a forward proxy environment could lead to unexpected results on certain (misconfigured?) webservers (i.e. ones accepting only SSLv2/3 protocol connections)
118 %% ----------------------------------------------------------------------
120 % See http://www.apsis.ch/pound
121 % See https://help.ubuntu.com/community/Pound
123 \subsubsection{Tested with Versions}
128 \subsubsection{Settings}
130 # HTTP Listener, redirects to HTTPS
135 Redirect "https://some.site.tld
142 AddHeader "Front-End-Https: on"
143 Cert "/path/to/your/cert.pem"
144 ## See 'man ciphers'.
145 Ciphers "TLSv1.2:TLSv1.1:!SSLv3:!SSLv2:%*\cipherStringB*)"