RE: [Pound Mailing List] OpenSSL SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS patch

It looks to me like you’ve done the patch correctly.  Not sure why it wouldn’t be working for you.

Are you using SSL labs to test?



Joe

From: Scott McKeown [mailto:scott-Oteo70RhwZ77w/[email protected]]
Sent: Monday, February 18, 2013 6:07 AM
To: [email protected]
Subject: [Pound Mailing List] OpenSSL SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS patch

Hi Guys,

I've been trying to add a new option to Pound that will allow you to set a 'SSLNoFragment' option in your pound.cfg file that when set to '1' will enable the OpenSSL 'SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS' option.

A copy of my attempt is below. However, with this added to my pound.cfg file and all rebuilt using Pound 2.6 and my new option enabled like this:

User            "nobody"
Group           "nobody"
LogLevel        0
Client          30
Timeout         60

ListenHTTPS
        # Label: pound_vip
        Address 192.168.82.199
        Port    443
        Cert    "/etc/pound/certs/pound_vip.pem"
        SSLHonorCipherOrder     1
        SSLAllowClientRenegotiation     0
        DisableSSLv2
        ReWriteLocation 1
        Ciphers "RC4:HIGH:!MD5:!DSS:!aNULL"
        SSLNoCompression 1
        SSLNoFragment 1
        Service
                BackEnd
                        Address 172.16.0.5
                        Port    80
                End
        End
End

It seems to accept the value. However, if I run a scan on the Real IP Address (the above addresses have been changed to protect the innocent) I still get a warning stating:

A vulnerability exists in SSL 3.0 and TLS 1.0 that could allow information disclosure if an attacker intercepts encrypted traffic served from an affected system. TLS 1.1, TLS 1.2, and all cipher suites that do not use CBC mode are not affected. This script tries to establish an SSL/TLS remote connection using an affected SSL version and cipher suite, and then solicits return data. If returned application data is not fragmented with an empty or one-byte record, it is likely vulnerable. OpenSSL uses empty fragments as a countermeasure unless the 'SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS' option is specified when OpenSSL is initialized. Microsoft implemented one-byte fragments as a countermeasure, and the setting can be controlled via the registry key HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\SecurityProviders\SCHANNEL\SendExtraRecord. Therefore, if multiple applications use the same SSL/TLS implementation, some may be vulnerable while others may not, depending on whether or not a countermeasure has been enabled. Note that this script detects the vulnerability in the SSLv3/TLSv1 protocol implemented in the server. It does not detect the BEAST attack where it exploits the vulnerability at HTTPS client-side (i.e., Internet browser). The detection at server-side does not necessarily means your server is vulnerable to the BEAST attack because the attack exploits the vulnerability at client-side, and both SSL/TLS clients and servers can independently employ the split record countermeasure.


My Pound Version details:

# pound -V
starting...
detect_tproxy(): tproxy is is detected
tproxy: available
Version 2.6
  Configuration switches:
    --enable-cert1l
    --with-maxbuf=8192
Exiting...


My attempted patch:

config.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletions(-)

diff --git a/config.c b/config.c

--- a/config.c  2013-02-15 11:38:19.634450776 +0000
+++ bconfig.c   2013-02-15 15:37:22.668452304 +0000
@@ -76,7 +76,7 @@
 static regex_t  Err414, Err500, Err501, Err503, MaxRequest, HeadRemove, RewriteLocation, RewriteDestination;
 static regex_t  Service, ServiceName, URL, HeadRequire, HeadDeny, BackEnd, Emergency, Priority, HAport, HAportAddr;
 static regex_t  Redirect, RedirectN, TimeOut, Session, Type, TTL, ID, DynScale;
-static regex_t  ClientCert, AddHeader, DisableSSLv2, SSLAllowClientRenegotiation, SSLHonorCipherOrder, SSLNoCompression, Ciphers;
+static regex_t  ClientCert, AddHeader, DisableSSLv2, SSLAllowClientRenegotiation, SSLHonorCipherOrder, SSLNoCompression, SSLNoFragment, Ciphers;
 static regex_t  CAlist, VerifyList, CRLlist, NoHTTPS11, Grace, Include, ConnTO, IgnoreCase, HTTPS, HTTPSCert;
 static regex_t  Disabled, Threads, CNName;

@@ -1082,6 +1082,14 @@
                 ssl_op_disable |= SSL_OP_NO_COMPRESSION;
                 ssl_op_enable &= ~SSL_OP_NO_COMPRESSION;
             }
+        } else if(!regexec(&SSLNoFragment, lin, 4, matches, 0)) {
+            if (atoi(lin + matches[1].rm_so)) {
+                ssl_op_enable |= SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS;
+                ssl_op_disable &= ~SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS;
+            } else {
+                ssl_op_disable |= SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS;
+                ssl_op_enable &= ~SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS;
+            }
         } else if(!regexec(&Ciphers, lin, 4, matches, 0)) {
             has_other = 1;
             if(res->ctx == NULL)
@@ -1376,6 +1384,7 @@
     || regcomp(&DisableSSLv2, "^[ \t]*DisableSSLv2[ \t]*$", REG_ICASE | REG_NEWLINE | REG_EXTENDED)
     || regcomp(&SSLHonorCipherOrder, "^[ \t]*SSLHonorCipherOrder[ \t]+([01])[ \t]*$", REG_ICASE | REG_NEWLINE | REG_EXTENDED)
     || regcomp(&SSLNoCompression, "^[ \t]*SSLNoCompression[ \t]+([01])[ \t]*$", REG_ICASE | REG_NEWLINE | REG_EXTENDED)
+    || regcomp(&SSLNoFragment, "^[ \t]*SSLNoFragment[ \t]+([01])[ \t]*$", REG_ICASE | REG_NEWLINE | REG_EXTENDED)
     || regcomp(&Ciphers, "^[ \t]*Ciphers[ \t]+\"(.+)\"[ \t]*$", REG_ICASE | REG_NEWLINE | REG_EXTENDED)
     || regcomp(&CAlist, "^[ \t]*CAlist[ \t]+\"(.+)\"[ \t]*$", REG_ICASE | REG_NEWLINE | REG_EXTENDED)
     || regcomp(&VerifyList, "^[ \t]*VerifyList[ \t]+\"(.+)\"[ \t]*$", REG_ICASE | REG_NEWLINE | REG_EXTENDED)
@@ -1541,6 +1550,7 @@
     regfree(&DisableSSLv2);
     regfree(&SSLHonorCipherOrder);
     regfree(&SSLNoCompression);
+    regfree(&SSLNoFragment);
     regfree(&Ciphers);
     regfree(&CAlist);
     regfree(&VerifyList);


Any help or advice would be most welcome.


--
With Kind Regards.

Scott McKeown
Loadbalancer.org
http://www.loadbalancer.org