DBM: Live Database Migration

Note: This howto uses percona-xtrabackup and percona-tools which can be downloaded for free. I also recommend to take some backups in between the following steps in case you are missing something. Also, closely watch error logs.

When executed correctly, the following commands should result in only ~ 1 minute downtime of the productive database.

The current setup consists of a ~ 280GB MySQL 5.5 DB including a ~ 130GB ibdata file w/o any form of replication @ our original database host db0.

What we want to have in the end, is a ~ 150GB MySQL 5.7 DB @ the new productive hosts db1 as well as the replication slave for backup and analysis @ db2.

Before we start, we implement binary logging and enable master configuration @ the currently productive db0 by setting the following, then restarting the db:

[mysqld]
log-bin=mysql-bin
server-id=1

We begin w/ a  live backup of the running database @ db0 onto db1:

d1g@db0:~$ time sudo innobackupex --defaults-file=my.cnf --user root --password=xxx --host=127.0.0.1 --stream=tar ./ | gzip | ssh user@db1 "cd /DATA ; tar -izx"

Afterwards, at db1, note the values from the file xtrabackup_binlog_info then apply the logs to prepare the data for usage @ db1:

d1g@db1:/DATA$ innobackupex --apply-log /DATA

Alright, we can now do the upgrade from 5.5 to 5.6:

d1g@db1:/DATA$ sudo mysql_upgrade -u root -p -h 127.0.0.1

It is time to install MySQL 5.7 and do the Upgrade from 5.6 to 5.7:

d1g@db1:/DATA$ sudo mysql_upgrade -u root -p -h 127.0.0.1

Optionally and if we want to get rid of a large ibdata file, export the current users db:

d1g@db1:/DATA$ pt-show-grants -uroot -p > users.sql

Then backup the current DB and replace it by a fresh and empty data directory, manually create the needed db scheme and copy only the .ibd and .cfg files from the old datadir, then implement the previously saved users.sql:

d1g@db1:/DATA/db# for i in ibd cfg ; do time cp -vRp /home/d1g/DBB/db/*.$i . ; done
db1|mysql> source users.sql;

After some manual fixes and import, we can now start optimizing the DB:

d1g@db1:~$ time mysqlcheck -u root -p -o db

We have the data ready and consistent for MySQL 5.7, so let’s setup db1 as master of db2 and slave of db0 and also explictely take care that it writes the logs needed for later usage of db2 for slave replication:

[mysqld]
log-bin=mysql-bin
server-id=2
relay-log=relay.log
log-slave-updates

It is very crucial to set the GRANT permissions right for db1 to replicate all the data that was created in the meantime on db0:

db0|mysql> GRANT REPLICATION SLAVE ON *.* TO 'repl'@'IP_OF_db1' IDENTIFIED BY 'password';

After this is done, we tell db1 to change to the db0 as master using the correct values from the xtrabackup_binlog_info and start the slave:

db1|mysql> CHANGE MASTER TO MASTER_HOST='IP_OF_db0', MASTER_USER='repl', MASTER_PASSWORD='xxxx', MASTER_LOG_FILE='mysql-bin.000002', MASTER_LOG_POS=643929298;
db1|mysql> START SLAVE;

Alright, db1 should be a replication slave for db0 and we have reached the first major milestone. Nice!

So now for the fun part which can be done in less than a minute: Configure db1 to be the new productive master having db2 as its replication slave, which is really no big deal: First, be sure that no new data is written to db0 by stopping the server. Then take note of the last values that db1 has received and stop the slave configuration:

db1|mysql> show master status;
+------------------+-----------+--------------+------------------+-------------------+
| File | Position | Binlog_Do_DB | Binlog_Ignore_DB | Executed_Gtid_Set |
+------------------+-----------+--------------+------------------+-------------------+
| mysql-bin.000026 | 469687058 | | | |
+------------------+-----------+--------------+------------------+-------------------+
1 row in set (0.00 sec)

db1|mysql> STOP SLAVE;

We need to permit db2 to replicate from db1:

db1|mysql> GRANT REPLICATION SLAVE ON *.* TO 'repl'@'IP_OF_db2' IDENTIFIED BY 'password';

Also setup db2 to be ready for the slave setup:

[mysqld]
log-bin=mysql-bin
server-id=3

Now, as done before, use that last master information from db1 in db2 to become a slave  and start the replication on these values:

db2|mysql> CHANGE MASTER TO MASTER_HOST='x.x.x.x', MASTER_USER='repl', MASTER_PASSWORD='xxxx', MASTER_LOG_FILE='mysql-bin.000026', MASTER_LOG_POS=469687058;
db2|mysql> START SLAVE;

That’s it. Now adjust DNS or whichever settings for your frontend to use the new db1 instead of db0, and also be sure to remove the now obsolete master.info from db1 so it does no longer try to reach it.

L7 Hardening: Security Headers

There are quite some directives at hand that can be added to your webserver configuration to achieve hardening against many attacks. Most websites – even those that really should – do not care, and thus receive a grade F when being checked by schd.io.

It is pretty straightforward to change that completely. In nginx 1.6.2, just edit the site’s config file and insert:

add_header Strict-Transport-Security "max-age=31536000";
add_header X-Frame-Options "SAMEORIGIN";
add_header X-Xss-Protection "1; mode=block";
add_header X-Content-Type-Options "nosniff";

The equivalent in nginx 1.8+ would be:

add_header Strict-Transport-Security "max-age=31536000";
add_header X-Frame-Options "SAMEORIGIN" always;
add_header X-Xss-Protection "1; mode=block" always;
add_header X-Content-Type-Options "nosniff" always;

This already gives us a grade C, but there is another powerful mechanism: the content security policy (CSP) is restricting the abilities of the browser to those predefined by you, especially only allowing certain servers to serve certain elements of the site’s content in the first place.

So lets take a closer look into this basic rule:

add_header Content-Security-Policy "default-src 'self'; connect-src 'self'; img-src 'self'; script-src 'self' ; style-src 'self' 'unsafe-inline' ";

This is restrictive and works only on static websites not involving any other sources for images, scripts or fonts.

As in most if not all cases when dealing w/ security, all this also involves the well known, eternal conflict: security vs. usability.

For example, webmail applications and underlying plugins often include inline javascript and thus need a bit less of restrictions expressed by

add_header Content-Security-Policy "default-src 'self'; connect-src 'self'; img-src 'self'; script-src 'self' 'unsafe-inline' 'unsafe-eval'; style-src 'self' 'unsafe-inline' ";

WordPress for example would require restrictions similar to

add_header Content-Security-Policy "default-src 'self'; connect-src 'self'; img-src 'self'; script-src 'self' 'unsafe-inline' 'unsafe-eval'; style-src 'self' 'unsafe-inline' https://fonts.googleapis.com; font-src 'self' https://fonts.gstatic.com data:";

The most efficient way to implement a valid CSP for your website and/or application is to use the debugging shortcut F12 in the browser of your choice and check the console for relevant messages while at the same time creating parameters for your CSP that fit the actual operational needs.

AVSx: Hardening the SPAM Perimeter

In the course of a recent AVSx rollout, we had the opportunity to mitigate the serious SPAM problem of a customer. This included analyzing the specific situation, considering different approaches to eliminate or at least minimize known issues and also involved a detailed measurement of the spam statistics over time, ultimately leading to a short whitepaper which is yet to be published. One important element of our first approach is to not depend too much on external (or internal) servers at runtime, so that the solution is pretty much self-contained and thus working autonomously.

 

Pre-Rollout Situation

The customer receives thousands of spammails per day, many of which get forwarded to the internal mailserver. Since at that internal mailserver, no catchall account is defined (the sub-contractor says that this is not possible), it occurs that non-delivery-reports (NDR) are sent out. And lots of them. This has also led to the problem that the customer itself even got blacklisted in recent months by this well-known backscatter problem. Also, there was heavy usage of black- and whitelists, which may have influenced the overall situation in a negative way as well, since that badly interferes w/ bayes filtering and the overall learning process if not handled carefully.

 

Improvement v1: Static LDAP

There are multiple ways to reduce the amount of bad e-mail, but the most commonly used  overall practice is to make use of spamassassin and clamav. Having these tools at hand together w/ a good mailserver S/W like postfix, things are to be tuned in a very efficient way.

Postfix hardening already brings quite some mechanisms. Using block- and blacklists is another approach which should not be used from the start on, because the spamfilter might not get trained if nearly no mail reaches the server itself. Imagine a non-trained spamfilter if the blacklist is unreachable. In my eyes, it is crucial to closely survey the situation of spam occurence and scores as a basis to create statistics. This again serves as a base for the definitition of the SPAM tag- and kill-levels, which should normally be set to 4.5 and 16 respectively. When analyzing the score distribution, we can identify a peak which should ideally be not too far left of the kill-level, or in contrast, on a well trained system, even right of the kill level, which means that already most mails get discarded.

But what about all the NDRs? We can query the internal LDAP server to get the information we need. So, at first, installing ldapvi makes sense. Then, if we have valid credentials, we can simply do

ldapvi -b "ou=xxx, dc=xxx, dc=xx" -h v.w.x.y -D you@yourdomain > ALLDATA.ldap.txt

and then get a list of valid e-mail adresses out of this by doing

grep "yourdomain" ALLDATA.ldap.txt | grep mail | cut -d ":" -f 2 | cut -d " " -f 2 | tee -a /etc/postfix/relay_recipients

This list of emails is the base for the definition of a relay_recipients file, which will accept mails only if the corresponding adresses are also found in the LDAP directory.

This eliminates the complete problematic NDR situation previously found, b/c the internal mailserver normally never has to state that mail is sent to a user w/o a corresponding mail: entry in the LDAP directory dump. In a static LDAP scenario, if an account gets removed or the internal mailserver itself has problems, would produce a NDR. One could query the LDAP DB once a month and recreate the relay_recipients file from that, but in general I guess manually changing/adding/removing users in the file makes more sense, and again, we do not want to depend too heavy on other servers. 

To use the relay_recipients file, the following parameter should be set in the postfix config

d1g@isp:~$ sudo postconf relay_recipient_maps
relay_recipient_maps = hash:/etc/postfix/relay_recipients

The maintenance of the valid recpients – if needed at all – could optionally be done by the local admin if we have a (cron-)skript in place that rebuilds the DB regularly by doing e.g.

postmap -v /etc/postfix/relay_recipients
postmap: name_mask: all
postmap: inet_addr_local: configured 2 IPv4 addresses
postmap: inet_addr_local: configured 2 IPv6 addresses
postmap: set_eugid: euid 1000 egid 1000
postmap: open hash relay_recipients
postmap: Compiled against Berkeley DB: 5.3.28?
postmap: Run-time linked against Berkeley DB: 5.3.28?

In this static LDAP setup, the mailserver accepts mail only for previously defined valid users, and simply by this already rejects a very high percentage of all spam mails, especially all that produced the problematic NDRs.

Improvement v2: Dynamic Lookups

While solely relying on dynamic lookups might get you into trouble as described above, having dynamic lookups only in cases where the recipient is not found statically makes sense, and also brings any change made in the LDAP directory immediately to the outside world. In order to enable the dynamic lookup feature, we have to first install postfix-ldap, and then define

relay_recipient_maps = hash:/etc/postfix/relay_recipients, ldap:/etc/postfix/ldap-aliases.cf

The tricky part is the ldap-aliases.cf file itself, as in our case it had to contain

server_host = x.x.x.x
search_base = ou=xxx, dc=xxx, dc=xx
version = 3
timeout = 10
leaf_result_attribute = mail
bind_dn = user@domain
bind_pw = userpassword
query_filter = (mail=%s) 
result_attribute = mail, addressToForward

Afterwards, restart postfix, and/or optionally test the setup by doing

postmap -vq user@domain ldap:/etc/postfix/ldap-aliases.cf

So, we now have both a static and dynamic mechanism in place, which makes the system rather failsafe and ready for immediate LDAP directory change propagation.

Last but not least: Keep in mind – if a valid user is listed in LDAP, but the corresponding mailbox is not available for whatever reason on the local mailserver, non-delivery receipts (NDR) will be sent sent out!

S/W issues: Apache 2.4/mod_fcgid

During a recent hardening/maintenance session,  the httpd was upgraded to the 2.4 version, which initially produced lots of php segfaults, most probably  b/c content and configs were not sufficiently adjusted by the admin(s) beforehand.

After some config + content adjustments during a 2nd maintenance session, the setup ran quite well, but during periods of high load, lots of different error messages were shown. Different types that kept our attention were:

[Sun Mar 05 23:39:40.008981 2017] [fcgid:emerg] [pid 6608:tid 139850686646016] (35)Resource deadlock avoided: [client x.x.x.x:48916] mod_fcgid: can't get pipe mutex
[Sun Mar 05 23:43:43.343519 2017] [fcgid:warn] [pid 7829:tid 139850577540864] (104)Connection reset by peer: [client x.x.x.x:49693] mod_fcgid: ap_pass_brigade failed in handle_request_ipc function, referer: ....
[Mon Mar 06 00:03:53.432715 2017] [fcgid:emerg] [pid 8618:tid 139850669860608] (35)Resource deadlock avoided: [client x.x.x.x:47173] mod_fcgid: can't lock process table in pid 8618, referer: ....

Also, the server had at least 20 php zombie processes running which cannot get killed but exhaust ressources and pile up:

1745 ?        Z      0:06 [php-cgi] <defunct> 
1753 ?        Z      0:06 [php-cgi] <defunct> 
3340 ?        Z      0:09 [php-cgi] <defunct> 
3341 ?        Z      0:09 [php-cgi] <defunct> 
3509 ?        Z      0:02 [php-cgi] <defunct>

So,  it seemed to have something to do w/ the way mod_fcgi starts php and locks underlying processes.

After a little research here and there, a checkout of how the system is configured gave us:

user@host:/opt/apache2/conf# grep -i mutex */*
extra/httpd-ssl.conf:SSLMutex "file:/opt/httpd-2.2.29/logs/ssl_mutex"
extra/httpd-ssl-domain.conf:Mutex file:/opt/apache2/logs/ssl_mutex

Hmm. One config even points to the wrong directory, and both use the “file” fcntl locking mechanism which seems to initially cause the errors.

Possible solutions would be to use

Mutex flock:${APACHE_LOCK_DIR} default

or as recommended

Mutex sem
SSLMutex sem

instead. Also, if the “sem” config-switch produces new errors, it may be b/c the kernels semaphore arrays are limited and should be extended by

sysctl -w kernel.sem="250 32000 32 1024"

So, just to be on the safe side, let’s do both, wait for a good timeslot to maintain, and reload the new config by service apache reload or via init which uses apachectl anyways:

/etc/init.d/apache reload

Great, all php zombie processes also vanished:

www-data 16178 0.9 0.2 95092 21788 ? S 02:41 0:00 /opt/php5/bin/php-cgi -c /opt/apache2/conf
www-data 16505 1.8 0.2 95100 21628 ? S 02:41 0:01 /opt/php5/bin/php-cgi -c /opt/apache2/conf
www-data 16685 3.9 0.2 93856 20480 ? S 02:41 0:03 /opt/php5/bin/php-cgi -c /opt/apache2/conf
www-data 16819 3.7 0.2 95104 21448 ? S 02:41 0:03 /opt/php5/bin/php-cgi -c /opt/apache2/conf
www-data 16846 1.7 0.2 95364 21692 ? S 02:41 0:01 /opt/php5/bin/php-cgi -c /opt/apache2/conf

The rest now seems to work as well, no more error messages thrown so far! Wait – after a while, one error reoccurs, and this very last section should be pretty self-explanatory:

#soll wohl auf 500 stehen
# d1g 060317
#FcgidMaxRequestsPerProcess 500
FcgidMaxRequestsPerProcess 0

Ethernet Issues v2: Retransmits

A few days before the time of this writing, certain problems arose at a high traffic (2.5 TB/day) and high load (50-75%) site.

What were the symptoms? The original settings ultimately led to TCP Retransmits, slowed down the specific users requests by aproximately 67 seconds on MacOS X, tho only by a few seconds in windows which maybe made the problem so hard to spot in the first place.

However,  LTE connections and other locations home networks seemed to have been unaffected by the issue, and an older linux router which seemed to eventually have compensated the mentioned problem until recently again made it hard to spot.

Normally, it is the other way around, but this time, a skilled customer took a deeper look into the issue (thnx, alex!) and gave us a hint having identified the probable involvement of the tcp_tw_recycle setting which can be checked by e.g.

# cat /proc/sys/net/ipv4/tcp_tw_recycle
1

What it does:

“Enable fast recycling of sockets in TIME-WAIT status. The default value is 0 (disabled). It should not be changed without advice/request of technical experts.”

Having mentioned tw_recycle, two other relevant settings are tcp_tw_reuse  and tcp_max_tw_buckets  which seems to be set to 262144 on newer and to as low as 16384, 65536 or 131072 on older systems. So yes, again there could be a connection to a high traffic site having roughly 77k connection states for some while, correlating w/ symptom appearance.

So, just to be safe, I would recommend setting it to a high value by

echo 262144 > /proc/sys/net/ipv4/tcp_max_tw_buckets

One could think that lots of TIME-WAIT states only arise if you have many clients w/ (too) idle connections coming from one NATed network, and that under normal circumstances the fast recycling may make sense. However, with the connection tracking table max. entries set to let’s say 512k, most systems perhaps never need to recycle the WAIT-STATES.

In the end, lets not forget about the fact that if we find problems, some trouble may have already taken place, but this is also the base for fixing it in most if not all cases.

OpenPGP Key Recreation and Revocation

Despites nearly having forgotten to blog about it, time has come to get myself a stronger OpenPGP keypair. But what about the folks I already established a secure connection with using the old key 0x800e21f5 and what about the rest of the internet? It’s not as complic as one might think.

Note: The following Howto is meant for more advanced users and involves the shell. Novice users should just continue to use roundcube for all their PGP related things.

 

1. Key Creation

Key creation is very simple if you use GnuPG on Linux:

0x220b:~$ gpg --gen-key

You can leave the default options (RSA/RSA,  4096bit, never expires) until it comes to name, e-mail and comment, where you should fill in your personal data associated w/ the use of the key. In most cases, one e-mail address is not enough, but you can just add one like this:

0x220b:~$ gpg --edit-key 6C71D217
gpg> showpref
[uneingeschränkt] (1). Peter Ohm (NetworkSEC/NWSEC) <p.ohm@networksec.de>
 Verschlü.: AES256, AES192, AES, CAST5, 3DES
 Digest: SHA256, SHA1, SHA384, SHA512, SHA224
 Komprimierung: ZLIB, BZIP2, ZIP, nicht komprimiert
 Eigenschaften: MDC, Keyserver no-modify
gpg> adduid

Now enter the other e-mail addy and a relevant comment if you wish. So, we now got a fresh key – but what about the old one(s)? At first, we should use them to sign the new one:

0x220b:~$ gpg --default-key 800e21f5 --sign-key 6C71D217
0x220b:~$ gpg --default-key 7BB7A759 --sign-key 6C71D217

and then finally give everybody access to our new public key by:

0x220b:~$ gpg --keyserver pgp.mit.edu --send-key 6C71D217

 

2. Key Revocation

Okay, now everybody must be able to know that the old keys are not used any longer. This can easily be achieved by first creating a revocation certificate for each of them, then importing that into the own keyring and finally exporting the revoked keys to the internet. Lets do it w/ a small shell skript and gpg2:

#!/bin/bash
for i in 7bb7a759 800e21f5
do
 gpg2 --output revoke.asc --gen-revoke $i
 gpg2 --import revoke.asc 
 gpg2 --keyserver pgp.mit.edu --send-keys $i
done

 

3. More Key Distribution

I also recommend to send everybody you already set up an encrypted communications channel with your new public key as they will be the only ones possibly using the old key material (most OpenPGP clients refuse to use revoked keys for encryption) and as it’s especially them who would need to be informed about any changes.

So, even if anybody interested in establishing a secure communications channel did not yet get your new public key, all that remains to be done is:

gpg --keyserver pgp.mit.edu --recv-keys 6C71D217
gpg --keyserver pgp.mit.edu --refresh-keys

…and don’t forget to attach your own public key if its a first-time contact.

Roundcube: Enigma PGP v2

Meant as an easy guide for novice users, this post will describe how to quickly establish a fully encrypted mail communication between two parties.

 

I assume that the system is up and running and enigma works, which means you have already created your own keypair as described in the 1st part of this howto.

Now, in case you are being uncreative and lazy, here is a hint: What comes next is actually start using it:

  • e-mail Alice
  • sign the mail 
  • attach your public key

Alice can then add your public key from the attachment, attach her own public key and then send a already fully encrypted  reply to you w/o a chance for an eavesdropper to even capture Alice’s (probably unlisted) public key. All of the subsequent messaging will be secured after you import Alice’s key which completes the encryption setup for both sides.

Even if Alice is also a novice user, initially does not have any PGP keypair but is also using roundcubemail  + enigma (or eventually GnuPG, Thunderbird, Enigmail, …), she can just create herself one and attach it. Got the idea?

The argument of being unable to establish a fully encrypted e-mail communication is no longer a valid excuse (and never really has been) b/c it only takes 2 steps per participant: keypair creation, pubkey distribution and as a consequence the import of the other ppl’s pubkey.

A short personal message: Thank you Edward Snowden. You caused a significant growth in the topic of general security awareness which resulted in the empowerment of EFF driven projects like letsencrypt and the rise of (hopefully) secure messengers amongst lots of other things: The so called Snowden-Effect. Be assured: As a final consequence, your statement has been clearly heard and at least partly understood (or turned into a business model) by the masses. Also, let’s not forget about WikiLeaksRapNews,  Phineas Fisher, Equation Group or Shadow Brokers who basically act into the same direction.

TLS Hardening v2: Postfix

So, hows it w/ postfix? Straightforward, but too many options to list them all 🙂 At first, we want to be able to look at some TLS details, in the logs as well as in the header, so we set

smtpd_tls_received_header = yes
smtpd_tls_loglevel = 1
smtp_tls_loglevel = 1

in /etc/postfix/main.cf. Furthermore, if not already set

smtpd_use_tls = yes
smtp_use_tls = yes
smtpd_tls_security_level = may
lmtp_tls_mandatory_ciphers = high
smtp_tls_mandatory_ciphers = high
smtpd_tls_mandatory_ciphers = high
smtp_tls_security_level = may
smtpd_tls_mandatory_exclude_ciphers = MD5, DES, ADH, RC4, PSD, SRP, 3DES, eNULL
smtpd_tls_exclude_ciphers = MD5, DES, ADH, RC4, PSD, SRP, 3DES, eNULL
smtpd_tls_mandatory_protocols = !SSLv2, !SSLv3
smtpd_tls_protocols = !SSLv2, !SSLv3

also makes sense, but still gives us a C+ rating. Folks at Qualys recommend

tls_export_cipherlist = aNULL:-aNULL:ALL:+RC4:@STRENGTH
tls_high_cipherlist = aNULL:-aNULL:ALL:!EXPORT:!LOW:!MEDIUM:+RC4:@STRENGTH
tls_legacy_public_key_fingerprints = no
tls_low_cipherlist = aNULL:-aNULL:ALL:!EXPORT:+RC4:@STRENGTH
tls_medium_cipherlist = aNULL:-aNULL:ALL:!EXPORT:!LOW:+RC4:@STRENGTH
tls_null_cipherlist = eNULL:!aNULL

but this also gives us C+. Doing more research, we finally get a B – still w/ a self-signed cert – by using

tls_export_cipherlist = EECDH+ECDSA+AESGCM:EECDH+aRSA+AESGCM:EECDH+ECDSA+SHA384:EECDH+ECDSA+SHA256:EECDH+aRSA+SHA384:EECDH+aRSA+SHA256:EECDH+aRSA+RC4:EECDH:EDH+aRSA:RC4:!aNULL:!eNULL:!LOW:!MEDIUM:!3DES:!MD5:!EXP:!PSK:!SRP:!DSS:!RC4
tls_high_cipherlist = EECDH+ECDSA+AESGCM:EECDH+aRSA+AESGCM:EECDH+ECDSA+SHA384:EECDH+ECDSA+SHA256:EECDH+aRSA+SHA384:EECDH+aRSA+SHA256:EECDH+aRSA+RC4:EECDH:EDH+aRSA:RC4:!aNULL:!eNULL:!LOW:!MEDIUM:!3DES:!MD5:!EXP:!PSK:!SRP:!DSS:!RC4
tls_legacy_public_key_fingerprints = no
tls_low_cipherlist = EECDH+ECDSA+AESGCM:EECDH+aRSA+AESGCM:EECDH+ECDSA+SHA384:EECDH+ECDSA+SHA256:EECDH+aRSA+SHA384:EECDH+aRSA+SHA256:EECDH+aRSA+RC4:EECDH:EDH+aRSA:RC4:!aNULL:!eNULL:!LOW:!MEDIUM:!3DES:!MD5:!EXP:!PSK:!SRP:!DSS:!RC4
tls_medium_cipherlist = EECDH+ECDSA+AESGCM:EECDH+aRSA+AESGCM:EECDH+ECDSA+SHA384:EECDH+ECDSA+SHA256:EECDH+aRSA+SHA384:EECDH+aRSA+SHA256:EECDH+aRSA+RC4:EECDH:EDH+aRSA:RC4:!aNULL:!eNULL:!LOW:!MEDIUM:!3DES:!MD5:!EXP:!PSK:!SRP:!DSS:!RC4
tls_null_cipherlist = eNULL:!aNULL

Together w/ a letsencrypt cert, we finally receive an A grade and full PCI-DSS compliance. Mission accomplished!

P.S.: If you are interested in a complete TLSv1.2 cipherlist, just issue

openssl ciphers TLSv1.2

Addendum: If you are on the lookout for governments deploying weak encryption, then this is for you:

May 5 01:44:08 isp postfix/smtpd[24611]: connect from correo.palmira.gov.co[190.144.251.105]
 May 5 01:44:09 isp postfix/smtpd[24611]: SSL_accept error from correo.palmira.gov.co[190.144.251.105]: -1
 May 5 01:44:09 isp postfix/smtpd[24611]: warning: TLS library problem: error:1408A0C1:SSL routines:SSL3_GET_CLIENT_HELLO:no shared cipher:s3_srvr.c:1440:
 May 5 01:44:09 isp postfix/smtpd[24611]: lost connection after STARTTLS from correo.palmira.gov.co[190.144.251.105]
 May 5 01:44:09 isp postfix/smtpd[24611]: disconnect from correo.palmira.gov.co[190.144.251.105]

A small snippet to look for more of that kind:

#!/bin/bash
#
# See which clients try to connect w/ old and insecure SSL
#
grep "accept error" $1 | cut -d ":" -f 4 | sort | uniq
exit 0

TLS Hardening v1: Qmail – fail

Recently, a friend notified me about the fact that his server was unable to send mail using PFS to one of my servers. Beginning to deal w/ this – your bet is right, during fullmoon – at first I checkout what i have and where i can tune it.

So for example, we want something like

TLSv1+HIGH:!SSLv2:!MD5

in /var/qmail/control/tls{server,client}ciphers. Afterwards, checking out the available TLSv1 cipher suites results in

Accepted TLSv1 256 bits AES256-SHA
Accepted TLSv1 256 bits CAMELLIA256-SHA
Accepted TLSv1 128 bits AES128-SHA
Accepted TLSv1 128 bits CAMELLIA128-SHA

for ports 25 and 465, which is far from best practice. So no DHE ciphers, b/c of no dh{1024,2048}.pem wich we can easily create by

openssl dhparam -out dh2048.pem 2048

and then set in the /service/qmail-smtpdssl/run file, we find

export KEYFILE=""
export DHFILE=""

which explains why no DHE ciphers were previously available. After having set the values to use our actual key material, we enabled them, thus getting

Accepted TLSv1 256 bits DHE-RSA-AES256-SHA
Accepted TLSv1 256 bits DHE-RSA-CAMELLIA256-SHA
Accepted TLSv1 256 bits AES256-SHA
Accepted TLSv1 256 bits CAMELLIA256-SHA
Accepted TLSv1 128 bits DHE-RSA-AES128-SHA
Accepted TLSv1 128 bits DHE-RSA-SEED-SHA
Accepted TLSv1 128 bits DHE-RSA-CAMELLIA128-SHA
Accepted TLSv1 128 bits AES128-SHA
Accepted TLSv1 128 bits SEED-SHA
Accepted TLSv1 128 bits CAMELLIA128-SHA
Accepted TLSv1 128 bits RC4-SHA
Accepted TLSv1 128 bits RC4-MD5
Accepted TLSv1 112 bits EDH-RSA-DES-CBC3-SHA
Accepted TLSv1 112 bits DES-CBC3-SHA

for port 465 which also has

SSL=1

set in the run file. But, there is still RC4 in there, which we can rule out by adding

export CIPHERS="TLSv1+HIGH:!SSLv2:!MD5"

in the appropriate run file right under the other options mentioned above, resulting in

Accepted TLSv1 256 bits DHE-RSA-AES256-SHA
Accepted TLSv1 256 bits DHE-RSA-CAMELLIA256-SHA
Accepted TLSv1 256 bits ADH-AES256-SHA
Accepted TLSv1 256 bits ADH-CAMELLIA256-SHA
Accepted TLSv1 256 bits AES256-SHA
Accepted TLSv1 256 bits CAMELLIA256-SHA
Accepted TLSv1 128 bits DHE-RSA-AES128-SHA
Accepted TLSv1 128 bits DHE-RSA-CAMELLIA128-SHA
Accepted TLSv1 128 bits ADH-AES128-SHA
Accepted TLSv1 128 bits ADH-CAMELLIA128-SHA
Accepted TLSv1 128 bits AES128-SHA
Accepted TLSv1 128 bits CAMELLIA128-SHA

However, connections using STARTTLS seem to still use non-PFS ciphersuites. The problem lies in the qmail design: If a connection comes in as plaintext – even w/ STARTTLS later on – , the variable SSL=0 is needed in the run file. If it comes in encrypted, SSL=1 is set. It is simply  impossible to set the parameters KEYFILE and DHFILE for qmail-smtpd, so even after STARTTLS, they cannot be used. And if we set SSL=1, STARTTLS will no longer work as the server states that the connection is already encrypted even tho that is not the case ^o.O^

Finally, after two days of effort invested in trying to patch skripts or even source code, I say “goodbye qmail” ! After having used that 20yr old S/W for 12+ years, it is now time to completely switchover to postfix, which i was using on a majority of systems anyways since 8 years.

PHP 7.1

Quite curious about the freshest PHP version and surely inspired by the full moon, I roll out PHP 7.1 + zend op_cache + memcached @ all hosting VMs and integrate it into the ISPC 3.1 customer interface as nicely explained here. I created a skript for easier rollout:

#!/bin/bash
#
# Skript w/ commands taken from http://www.ispconfig.org/blog/install-php-7-1-php-fpm-fastcgi-ispconfig-3-1-debian-8-jessie/
# not fine grained yet as it needs sudo permissions :|
#
echo "Create directories..."
mkdir -p /opt/php-7.1
mkdir /usr/local/src/php7-build
cd /usr/local/src/php7-build
wget http://de1.php.net/get/php-7.1.0.tar.bz2/from/this/mirror -O php-7.1.0.tar.bz2
tar jxf php-7.1.0.tar.bz2
cd php-7.1.0/
apt-get install libfcgi-dev libfcgi0ldbl libjpeg62-turbo-dbg libmcrypt-dev libssl-dev libc-client2007e libc-client2007e-dev libxml2-dev libbz2-dev libcurl4-openssl-dev libjpeg-dev libpng12-dev libfreetype6-dev libkrb5-dev libpq-dev libxml2-dev libxslt1-dev -y
ln -s /usr/lib/libc-client.a /usr/lib/x86_64-linux-gnu/libc-client.a
time ./configure --prefix=/opt/php-7.1 --with-pdo-pgsql --with-zlib-dir --with-freetype-dir --enable-mbstring --with-libxml-dir=/usr --enable-soap --enable-calendar --with-curl --with-mcrypt --with-zlib --with-gd --with-pgsql --disable-rpath --enable-inline-optimization --with-bz2 --with-zlib --enable-sockets --enable-sysvsem --enable-sysvshm --enable-pcntl --enable-mbregex --enable-exif --enable-bcmath --with-mhash --enable-zip --with-pcre-regex --with-pdo-mysql --with-mysqli --with-mysql-sock=/var/run/mysqld/mysqld.sock --with-jpeg-dir=/usr --with-png-dir=/usr --enable-gd-native-ttf --with-openssl --with-fpm-user=www-data --with-fpm-group=www-data --with-libdir=/lib/x86_64-linux-gnu --enable-ftp --with-imap --with-imap-ssl --with-kerberos --with-gettext --with-xmlrpc --with-xsl --enable-opcache --enable-fpm
time make -j2
make install
cp /usr/local/src/php7-build/php-7.1.0/php.ini-production /opt/php-7.1/lib/php.ini
cp /opt/php-7.1/etc/php-fpm.conf.default /opt/php-7.1/etc/php-fpm.conf
cp /opt/php-7.1/etc/php-fpm.d/www.conf.default /opt/php-7.1/etc/php-fpm.d/www.conf

I already tested it w/ the blog you are reading right now running WP 4.6 and 4.7 w/o any issues. Testing w/ an old version of WP 4.1.x seems to not work w/ PHP 7.x as expected and b/c its code is using obsolete PHP 5.x syntax.

So, if you are dealing w/ a freshly installed WP 4.1.x instance, just upgrade first to 4.7, and then select the optional switch to PHP 7.1 for your site to make it work.

PHP 7.1.0 (cgi-fcgi) (built: Dec 13 2016 04:45:07)
Copyright (c) 1997-2016 The PHP Group
Zend Engine v3.1.0-dev, Copyright (c) 1998-2016 Zend Technologies
with Zend OPcache v7.1.0, Copyright (c) 1999-2016, by Zend Technologies

I get the impression that PHP7  really speeds things up, and would like to hear your comments on that subject as well. Happy testing 🙂