Making sure SSLv2 is disabled in Apache (and Nginx)


Edit Jan 24, 2012: Deleted all the crap from this story and just left the recommended Apache and Nginx SSL cipher suites for maximum security without SSLv2 and without BEAST vulnerability (at least according to Qualys).

Apache httpd

SSLProtocol -ALL +SSLv3 +TLSv1
SSLCipherSuite ECDHE-RSA-AES256-SHA384:AES256-SHA256:RC4:HIGH:!MD5:!aNULL:!EDH:!AESGCM;
SSLHonorCipherOrder on

nginx

        ssl_protocols  SSLv3 TLSv1;
        ssl_ciphers     ECDHE-RSA-AES256-SHA384:AES256-SHA256:RC4:HIGH:!MD5:!aNULL:!EDH:!AESGCM;
        ssl_prefer_server_ciphers   on;

Source:

Go Daddy $12.99 SSL Sale!

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Relaying through Google Apps using Sendmail to bypass EC2 spam blockage

Update 3 May 2011: I’ve subsequently modified our EC2 systems to relay SMTP mail through Amazon’s SES which doesn’t have the 500 messages per day limit that Google Apps does.

A few months ago I moved a site into EC2. I didn’t want to move the existing IMAP server (ugh) so I moved the email to Google Apps. There are only about 10 mailboxes so we went with “Standard” edition (free). Once we completed the move to EC2 we discovered that emails from our webserver were bouncing due to our EC2 IP address being listed in a spam RBL. This sucked, so I looked into relaying the mail from the EC2 webserver through our Google Apps account. Fortunately this turned out to be pretty easy.

This wiki page on scalix.com has a procedure for setting up SMTP relaying in Ubuntu with TLS & auth. I’m not running Ubuntu so the paths were different but it was basically the same procedure:

  • Create the file /etc/mail/client-info with these contents: AuthInfo:smtp.gmail.com "U:bounces@example.com" "I:bounces@example.com" "P:superpassword", where “example.com” is your Google Apps domain, “bounces” is a valid account, and the password is the account’s password. Mail relayed with these credentials will show “bounces@example.com” in the From: field of the message.
  • In /etc/mail, run makemap hash client-info < client-info
  • Edit /etc/mail/sendmail.mc, adding or uncommenting these lines:
    define(`SMART_HOST', `smtp.gmail.com')dnl
    define(`confAUTH_MECHANISMS', `EXTERNAL GSSAPI DIGEST-MD5 CRAM-MD5 LOGIN PLAIN')dnl
    FEATURE(`authinfo', `hash /etc/mail/client-info')dnl
    
  • Recompile sendmail.cf: m4 sendmail.mc > sendmail.cf . I got this error: “/etc/mail/sendmail.mc:10: m4: Cannot open /usr/share/sendmail-cf/m4/cf.m4” when running the command, but I resolved it by doing yum install sendmail-cf
  • Restart sendmail.

Once this was done I sent myself a test message from the command line and received it; I checked the SMTP headers and sure enough it went through Google’s mail server. One nice side effect is that all the mail sent by the webserver appears in the “Sent” folder for the Google Apps username provided in the client-info file. Hopefully this will resolve the spam issues, since the mail is now coming from Google’s IP block.

Wasted time with Exchange 2010, SquirrelMail, and IMAP-SSL

I’m setting up SquirrelMail to point to my Exchange 2010 server via IMAP (don’t ask) and couldn’t get SM to talk to Exchange on port 993 (imaps). Even though the servers on the same subnet, any time passwords are being sent over the network I like to opt for SSL. I found a couple of sites suggesting that the problem was that there was no SSL certificate installed, but I knew for a fact there was a valid certificate because I could get to https://webmail.example.com/ for OWA.

Some of the errors SquirrelMail was reporting were “Error connecting to IMAP server xxxx Server error: (0)” and “Error connecting to IMAP server: tls://xxxx:993. 0: ”

Nothing would actually work on port 993. Telnet to 993 got this:

$ telnet 10.0.20.18 993
Trying 10.0.20.18...
Connected to 10.0.20.18.
Escape character is '^]'.
* BYE Connection is closed. 14
Connection closed by foreign host.

After too much poking, I decided to go down to a lower level and do a simple openssl certificate retrieval and see what came back:


$ openssl s_client -connect 10.0.20.18:993
CONNECTED(00000003)
140281653434184:error:140770FC:SSL routines:SSL23_GET_SERVER_HELLO:unknown protocol:s23_clnt.c:699:
---
no peer certificate available
---
No client certificate CA names sent
---
SSL handshake has read 7 bytes and written 113 bytes
---
New, (NONE), Cipher is (NONE)
Secure Renegotiation IS NOT supported
Compression: NONE
Expansion: NONE
---

That didn’t look right, so I ran it against the same server on port 443 and got back a real certificate. Same for port 995 (pop3s):

$ openssl s_client -connect 10.0.20.18:443
CONNECTED(00000003)
depth=3 L = ValiCert Validation Network, O = "ValiCert, Inc.", OU = ValiCert Class 2 Policy Validation Authority, CN = http://www.valicert.com/, emailAddress = info@valicert.com
verify return:1
depth=2 C = US, O = "The Go Daddy Group, Inc.", OU = Go Daddy Class 2 Certification Authority
verify return:1

(snip)

So there’s just something wrong with SSL on port 993. To make a long story short, I had to use the Enable-ExchangeCertificate to apply the SSL certificate to port 993. First, run “Get-ExchangeCertificate” to list the available certificates and retrieve the Thumbprint.

[PS] C:\Windows\system32>Get-ExchangeCertificate

Thumbprint                                Services   Subject
----------                                --------   -------
yyyyyyyyyyyyyyyyyyyyyyyyyyyyyyy  .P....     CN=exch2010fe1
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx  I..W..     CN=webmail.example.com, OU=Domain Control Validated, O=webmail.ex...

Copy & paste the thumbprint for whichever cert you want to use into Enable-ExchangeCertificate:

[PS] C:\Windows\system32>Enable-ExchangeCertificate -ThumbPrint xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx -Services IIS,P
OP,IMAP -DoNotRequireSSL
[PS] C:\Windows\system32>Get-ExchangeCertificate

Thumbprint                                Services   Subject
----------                                --------   -------
yyyyyyyyyyyyyyyyyyyyyyyyyyyyyyy  ......     CN=exch2010fe1
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx  IP.W..     CN=webmail.example.com, OU=Domain Control Validated, O=webmail.ex...

After running that, imaps on port 993 worked perfectly. I can connect to it with both SquirrelMail and Thunderbird.

The SquirrelMail config looks like this:

IMAP Settings
--------------
4.  IMAP Server            : webmail.example.com
5.  IMAP Port              : 993
6.  Authentication type    : login
7.  Secure IMAP (TLS)      : true
8.  Server software        : exchange
9.  Delimiter              : detect

Edit Feb 15, 2011: I just renewed the SSL cert and ran into a problem with a Ruby script that was suddenly unable to check a mailbox over IMAPS. The error received was:

/usr/lib/ruby/1.8/net/imap.rb:898:in `connect': unknown protocol (OpenSSL::SSL::SSLError)
        from /usr/lib/ruby/1.8/net/imap.rb:898:in `initialize'

After a few minutes, I remembered this blog post and ran Enable-ExchangeCertificate and it worked again. Glad I wrote it down.

CONNECTED(00000003) 26831:error:140790E5:SSL routines:SSL23_WRITE:ssl handshake failure:s23_lib.c:188: