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Sep
27
2017
Rspamd Fast, free and open-source spam filtering system

Fighting Spam

Fighting email spam in modern times most of the times looks like this:

1ab83c40625d102da1b3001438c0f03b.gif

Rspamd

Rspamd is a rapid spam filtering system. Written in C with Lua script engine extension seems to be really fast and a really good solution for SOHO environments.

In this blog post, I'’ll try to present you a quickstart guide on working with rspamd on a CentOS 6.9 machine running postfix.

DISCLAIMER: This blog post is from a very technical point of view!

Installation

We are going to install rspamd via know rpm repositories:

Epel Repository

We need to install epel repository first:

# yum -y install http://fedora-mirror01.rbc.ru/pub/epel/6/x86_64/epel-release-6-8.noarch.rpm

Rspamd Repository

Now it is time to setup the rspamd repository:

# curl https://rspamd.com/rpm-stable/centos-6/rspamd.repo -o /etc/yum.repos.d/rspamd.repo

Install the gpg key

# rpm --import http://rspamd.com/rpm-stable/gpg.key

and verify the repository with # yum repolist

repo id     repo name
base        CentOS-6 - Base
epel        Extra Packages for Enterprise Linux 6 - x86_64
extras      CentOS-6 - Extras
rspamd      Rspamd stable repository
updates     CentOS-6 - Updates

Rpm

Now it is time to install rspamd to our linux box:

# yum -y install rspamd


# yum info rspamd

Name        : rspamd
Arch        : x86_64
Version     : 1.6.3
Release     : 1
Size        : 8.7 M
Repo        : installed
From repo   : rspamd
Summary     : Rapid spam filtering system
URL         : https://rspamd.com
License     : BSD2c
Description : Rspamd is a rapid, modular and lightweight spam filter. It is designed to work
            : with big amount of mail and can be easily extended with own filters written in
            : lua.

Init File

We need to correct rspamd init file so that rspamd can find the correct configuration file:

# vim /etc/init.d/rspamd

# ebal, Wed, 06 Sep 2017 00:31:37 +0300
## RSPAMD_CONF_FILE="/etc/rspamd/rspamd.sysvinit.conf"
RSPAMD_CONF_FILE="/etc/rspamd/rspamd.conf"

Start Rspamd

We are now ready to start for the first time rspamd daemon:

# /etc/init.d/rspamd restart

syntax OK
Stopping rspamd:                                           [FAILED]
Starting rspamd:                                           [  OK  ]

verify that is running:

# ps -e fuwww | egrep -i rsp[a]md


root      1337  0.0  0.7 205564  7164 ?        Ss   20:19   0:00 rspamd: main process
_rspamd   1339  0.0  0.7 206004  8068 ?        S    20:19   0:00  _ rspamd: rspamd_proxy process
_rspamd   1340  0.2  1.2 209392 12584 ?        S    20:19   0:00  _ rspamd: controller process
_rspamd   1341  0.0  1.0 208436 11076 ?        S    20:19   0:00  _ rspamd: normal process   

perfect, now it is time to enable rspamd to run on boot:

# chkconfig rspamd on

# chkconfig --list | egrep rspamd
rspamd          0:off   1:off   2:on    3:on    4:on    5:on    6:off

Postfix

In a nutshell, postfix will pass through (filter) an email using the milter protocol to another application before queuing it to one of postfix’s mail queues. Think milter as a bridge that connects two different applications.

rspamd_milter_direct.png

Rspamd Proxy

In Rspamd 1.6 Rmilter is obsoleted but rspamd proxy worker supports milter protocol. That means we need to connect our postfix with rspamd_proxy via milter protocol.

Rspamd has a really nice documentation: https://rspamd.com/doc/index.html
On MTA integration you can find more info.

# netstat -ntlp | egrep -i rspamd

output:

tcp        0      0 0.0.0.0:11332               0.0.0.0:*                   LISTEN      1451/rspamd
tcp        0      0 0.0.0.0:11333               0.0.0.0:*                   LISTEN      1451/rspamd
tcp        0      0 127.0.0.1:11334             0.0.0.0:*                   LISTEN      1451/rspamd
tcp        0      0 :::11332                    :::*                        LISTEN      1451/rspamd
tcp        0      0 :::11333                    :::*                        LISTEN      1451/rspamd
tcp        0      0 ::1:11334                   :::*                        LISTEN      1451/rspamd  

# egrep -A1 proxy /etc/rspamd/rspamd.conf


worker "rspamd_proxy" {
    bind_socket = "*:11332";
    .include "$CONFDIR/worker-proxy.inc"
    .include(try=true; priority=1,duplicate=merge) "$LOCAL_CONFDIR/local.d/worker-proxy.inc"
    .include(try=true; priority=10) "$LOCAL_CONFDIR/override.d/worker-proxy.inc"
}

Milter

If you want to know all the possibly configuration parameter on postfix for milter setup:

# postconf | egrep -i milter

output:

milter_command_timeout = 30s
milter_connect_macros = j {daemon_name} v
milter_connect_timeout = 30s
milter_content_timeout = 300s
milter_data_macros = i
milter_default_action = tempfail
milter_end_of_data_macros = i
milter_end_of_header_macros = i
milter_helo_macros = {tls_version} {cipher} {cipher_bits} {cert_subject} {cert_issuer}
milter_macro_daemon_name = $myhostname
milter_macro_v = $mail_name $mail_version
milter_mail_macros = i {auth_type} {auth_authen} {auth_author} {mail_addr} {mail_host} {mail_mailer}
milter_protocol = 6
milter_rcpt_macros = i {rcpt_addr} {rcpt_host} {rcpt_mailer}
milter_unknown_command_macros =
non_smtpd_milters =
smtpd_milters = 

We are mostly interested in the last two, but it is best to follow rspamd documentation:

# vim /etc/postfix/main.cf

Adding the below configuration lines:

# ebal, Sat, 09 Sep 2017 18:56:02 +0300

## A list of Milter (mail filter) applications for new mail that does not arrive via the Postfix smtpd(8) server.
on_smtpd_milters = inet:127.0.0.1:11332

## A list of Milter (mail filter) applications for new mail that arrives via the Postfix smtpd(8) server.
smtpd_milters = inet:127.0.0.1:11332

## Send macros to mail filter applications
milter_mail_macros = i {auth_type} {auth_authen} {auth_author} {mail_addr} {client_addr} {client_name} {mail_host} {mail_mailer}

## skip mail without checks if something goes wrong, like rspamd is down !
milter_default_action = accept

Reload postfix

# postfix reload

postfix/postfix-script: refreshing the Postfix mail system

Testing

netcat

From a client:

$ nc 192.168.122.96 25

220 centos69.localdomain ESMTP Postfix
EHLO centos69
250-centos69.localdomain
250-PIPELINING
250-SIZE 10240000
250-VRFY
250-ETRN
250-ENHANCEDSTATUSCODES
250-8BITMIME
250 DSN
MAIL FROM: <root@example.org>
250 2.1.0 Ok
RCPT TO: <root@localhost>
250 2.1.5 Ok
DATA
354 End data with <CR><LF>.<CR><LF>
test
.
250 2.0.0 Ok: queued as 4233520144
^]

Logs

Looking through logs may be a difficult task for many, even so it is a task that you have to do.

MailLog

# egrep 4233520144 /var/log/maillog


Sep  9 19:08:01 localhost postfix/smtpd[1960]: 4233520144: client=unknown[192.168.122.1]
Sep  9 19:08:05 localhost postfix/cleanup[1963]: 4233520144: message-id=<>
Sep  9 19:08:05 localhost postfix/qmgr[1932]: 4233520144: from=<root@example.org>, size=217, nrcpt=1 (queue active)
Sep  9 19:08:05 localhost postfix/local[1964]: 4233520144: to=<root@localhost.localdomain>, orig_to=<root@localhost>, relay=local, delay=12, delays=12/0.01/0/0.01, dsn=2.0.0, status=sent (delivered to mailbox)
Sep  9 19:08:05 localhost postfix/qmgr[1932]: 4233520144: removed

Everything seems fine with postfix.

Rspamd Log

# egrep -i 4233520144 /var/log/rspamd/rspamd.log

2017-09-09 19:08:05 #1455(normal) <79a04e>; task; rspamd_message_parse: loaded message; id: <undef>; queue-id: <4233520144>; size: 6; checksum: <a6a8e3835061e53ed251c57ab4f22463>

2017-09-09 19:08:05 #1455(normal) <79a04e>; task; rspamd_task_write_log: id: <undef>, qid: <4233520144>, ip: 192.168.122.1, from: <root@example.org>, (default: F (add header): [9.40/15.00] [MISSING_MID(2.50){},MISSING_FROM(2.00){},MISSING_SUBJECT(2.00){},MISSING_TO(2.00){},MISSING_DATE(1.00){},MIME_GOOD(-0.10){text/plain;},ARC_NA(0.00){},FROM_NEQ_ENVFROM(0.00){;root@example.org;},RCVD_COUNT_ZERO(0.00){0;},RCVD_TLS_ALL(0.00){}]), len: 6, time: 87.992ms real, 4.723ms virtual, dns req: 0, digest: <a6a8e3835061e53ed251c57ab4f22463>, rcpts: <root@localhost>

It works !

Training

If you have already a spam or junk folder is really easy training the Bayesian classifier with rspamc.

I use Maildir, so for my setup the initial training is something like this:

 # cd /storage/vmails/balaskas.gr/evaggelos/.Spam/cur/ 

# find . -type f -exec rspamc learn_spam {} \;

Auto-Training

I’ve read a lot of tutorials that suggest real-time training via dovecot plugins or something similar. I personally think that approach adds complexity and for small companies or personal setup, I prefer using Cron daemon:


 @daily /bin/find /storage/vmails/balaskas.gr/evaggelos/.Spam/cur/ -type f -mtime -1 -exec rspamc learn_spam {} \;

That means every day, search for new emails in my spam folder and use them to train rspamd.

Training from mbox

First of all seriously ?

Split mbox

There is a nice and simply way to split a mbox to separated files for rspamc to use them.

# awk '/^From / {i++}{print > "msg"i}' Spam

and then feed rspamc:

# ls -1 msg* | xargs rspamc --verbose learn_spam

Stats

# rspamc stat


Results for command: stat (0.068 seconds)
Messages scanned: 2
Messages with action reject: 0, 0.00%
Messages with action soft reject: 0, 0.00%
Messages with action rewrite subject: 0, 0.00%
Messages with action add header: 2, 100.00%
Messages with action greylist: 0, 0.00%
Messages with action no action: 0, 0.00%
Messages treated as spam: 2, 100.00%
Messages treated as ham: 0, 0.00%
Messages learned: 1859
Connections count: 2
Control connections count: 2157
Pools allocated: 2191
Pools freed: 2170
Bytes allocated: 542k
Memory chunks allocated: 41
Shared chunks allocated: 10
Chunks freed: 0
Oversized chunks: 736
Fuzzy hashes in storage "rspamd.com": 659509399
Fuzzy hashes stored: 659509399
Statfile: BAYES_SPAM type: sqlite3; length: 32.66M; free blocks: 0; total blocks: 430.29k; free: 0.00%; learned: 1859; users: 1; languages: 4
Statfile: BAYES_HAM type: sqlite3; length: 9.22k; free blocks: 0; total blocks: 0; free: 0.00%; learned: 0; users: 1; languages: 1
Total learns: 1859

X-Spamd-Result

To view the spam score in every email, we need to enable extended reporting headers and to do that we need to edit our configuration:

# vim /etc/rspamd/modules.d/milter_headers.conf

and just above use add :

    # ebal, Wed, 06 Sep 2017 01:52:08 +0300
    extended_spam_headers = true;

   use = [];

then reload rspamd:

# /etc/init.d/rspamd reload

syntax OK
Reloading rspamd:                                          [  OK  ]

View Source

If your open the email in view-source then you will see something like this:


X-Rspamd-Queue-Id: D0A5728ABF
X-Rspamd-Server: centos69
X-Spamd-Result: default: False [3.40 / 15.00]

Web Server

Rspamd comes with their own web server. That is really useful if you dont have a web server in your mail server, but it is not recommended.

By-default, rspamd web server is only listening to local connections. We can see that from the below ss output

# ss -lp | egrep -i rspamd

LISTEN     0      128                    :::11332                   :::*        users:(("rspamd",7469,10),("rspamd",7471,10),("rspamd",7472,10),("rspamd",7473,10))
LISTEN     0      128                     *:11332                    *:*        users:(("rspamd",7469,9),("rspamd",7471,9),("rspamd",7472,9),("rspamd",7473,9))
LISTEN     0      128                    :::11333                   :::*        users:(("rspamd",7469,18),("rspamd",7473,18))
LISTEN     0      128                     *:11333                    *:*        users:(("rspamd",7469,16),("rspamd",7473,16))
LISTEN     0      128                   ::1:11334                   :::*        users:(("rspamd",7469,14),("rspamd",7472,14),("rspamd",7473,14))
LISTEN     0      128             127.0.0.1:11334                    *:*        users:(("rspamd",7469,12),("rspamd",7472,12),("rspamd",7473,12))

127.0.0.1:11334

So if you want to change that (dont) you have to edit the rspamd.conf (core file):

# vim +/11334 /etc/rspamd/rspamd.conf

and change this line:

bind_socket = "localhost:11334";

to something like this:

bind_socket = "YOUR_SERVER_IP:11334";

or use sed:

# sed -i -e 's/localhost:11334/YOUR_SERVER_IP/' /etc/rspamd/rspamd.conf

and then fire up your browser:

rspamd_worker.png

Web Password

It is a good tactic to change the default password of this web-gui to something else.

# vim /etc/rspamd/worker-controller.inc

  # password = "q1";
  password = "password";

always a good idea to restart rspamd.

Reverse Proxy

I dont like having exposed any web app without SSL or basic authentication, so I shall put rspamd web server under a reverse proxy (apache).

So on httpd-2.2 the configuration is something like this:

ProxyPreserveHost On

<Location /rspamd>
    AuthName "Rspamd Access"
    AuthType Basic
    AuthUserFile /etc/httpd/rspamd_htpasswd
    Require valid-user

    ProxyPass http://127.0.0.1:11334
    ProxyPassReverse http://127.0.0.1:11334 

    Order allow,deny
    Allow from all 

</Location>

Http Basic Authentication

You need to create the file that is going to be used to store usernames and password for basic authentication:

# htpasswd -csb /etc/httpd/rspamd_htpasswd rspamd rspamd_passwd
Adding password for user rspamd

restart your apache instance.

bind_socket

Of course for this to work, we need to change the bind socket on rspamd.conf
Dont forget this ;)

bind_socket = "127.0.0.1:11334";

Selinux

If there is a problem with selinux, then:

# setsebool -P httpd_can_network_connect=1

or

# setsebool httpd_can_network_connect_db on

Errors ?

If you see an error like this:
IO write error

when running rspamd, then you need explicit tell rspamd to use:

rspamc -h 127.0.0.1:11334

To prevent any future errors, I’ve created a shell wrapper:

/usr/local/bin/rspamc

#!/bin/sh
/usr/bin/rspamc -h 127.0.0.1:11334 $*

Final Thoughts

I am using rspamd for a while know and I am pretty happy with it.

I’ve setup a spamtrap email address to feed my spam folder and let the cron script to train rspamd.

So after a thousand emails:

rspamd1k.jpg

Jun
29
2017
STARTTLS with CRAM-MD5 on dovecot using LDAP

Prologue

I should have written this post like a decade ago, but laziness got the better of me.

I use TLS with IMAP and SMTP mail server. That means I encrypt the connection by protocol against the mail server and not by port (ssl Vs tls). Although I do not accept any authentication before STARTTLS command is being provided (that means no cleartext passwords in authentication), I was leaving the PLAIN TEXT authentication mechanism in the configuration. That’s not an actual problem unless you are already on the server and you are trying to connect on localhost but I can do better.

LDAP

I use OpenLDAP as my backend authentication database. Before all, the ldap attribute password must be changed from cleartext to CRAM-MD5

Typing the doveadm command from dovecot with the password method:

# doveadm pw

Enter new password:    test
Retype new password:   test
{CRAM-MD5}e02d374fde0dc75a17a557039a3a5338c7743304777dccd376f332bee68d2cf6

will return the CRAM-MD5 hash of our password (test)

Then we need to edit our DN (distinguished name) with ldapvi:

From:

uid=USERNAME,ou=People,dc=example,dc=org
userPassword: test

To:

uid=USERNAME,ou=People,dc=example,dc=org
userPassword: {CRAM-MD5}e02d374fde0dc75a17a557039a3a5338c7743304777dccd376f332bee68d2cf6

Dovecot

Dovecot is not only the imap server but also the “Simple Authentication and Security Layer” aka SASL service. That means that imap & smtp are speaking with dovecot for authentication and dovecot uses ldap as the backend. To change AUTH=PLAIN to cram-md5 we need to do the below change:

file: 10-auth.conf

From:

auth_mechanisms = plain

To:

auth_mechanisms = cram-md5

Before restarting dovecot, we need to make one more change. This step took me a couple hours to figure it out! On our dovecot-ldap.conf.ext configuration file, we need to tell dovecot NOT to bind to ldap for authentication but let dovecot to handle the authentication process itself:

From:

# Enable Authentication Binds
# auth_bind = yes

To:

# Enable Authentication Binds
auth_bind = no

To guarantee that the entire connection is protected by TLS encryption, change in 10-ssl.conf the below setting:

From:

ssl = yes

To:

ssl = required

SSL/TLS is always required, even if non-plaintext authentication mechanisms are used. Any attempt to authenticate before SSL/TLS is enabled will cause an authentication failure.

After that, restart your dovecot instance.

Testing

# telnet example.org imap

Trying 172.12.13.14 ...
Connected to example.org.
Escape character is '^]'.
* OK [CAPABILITY IMAP4rev1 LITERAL+ SASL-IR LOGIN-REFERRALS ID ENABLE IDLE STARTTLS AUTH=CRAM-MD5] Dovecot ready.

1 LOGIN USERNAME@example.org test

1 NO [ALERT] Unsupported authentication mechanism.
^]
telnet> clo

That meas no cleartext authentication is permitted

MUA

Now the hard part, the mail clients:

RainLoop

My default webmail client since v1.10.1.123 supports CRAM-MD5
To verify that, open your application.ini file under your data folder and search for something like that:

    imap_use_auth_plain = On
    imap_use_auth_cram_md5 = On
    smtp_use_auth_plain = On
    smtp_use_auth_cram_md5 = On

as a bonus, rainloop supports STARTTLS and authentication for imap & smtp, even when talking to 127.0.0.1

Thunderbird

thunderbird_cram_md5.png

K9

k9.png

Jun
04
2017
postfix TLS & ipv6

Postfix

smtp Vs smtpd

smtp.jpg

  • postfix/smtp
    • The SMTP daemon is for sending emails to the Internet (outgoing mail server).
  • postfix/smtpd
    • The SMTP daemon is for receiving emails from the Internet (incoming mail server).

TLS

Encryption on mail transport is what we call: opportunistic. If both parties (sender’s outgoing mail server & recipient’s incoming mail server) agree to exchange encryption keys, then a secure connection may be used. Otherwise a plain connection will be established. Plain as in non-encrypted aka cleartext over the wire.

SMTP - Outgoing Traffic

In the begging there where only three options in postfix:

  • none
  • may
  • encrypt

The default option on a Centos 6x is none:

# postconf -d | grep smtp_tls_security_level
smtp_tls_security_level =

Nowadays, postfix supports more options, like:

  • dane
  • verify
  • secure

Here is the basic setup, to enable TLS on your outgoing mail server:

smtp_tls_security_level = may
smtp_tls_loglevel = 1

From postfix v2.6 and later, can you disable weak encryption by selecting the cipher suite and protocols you prefer to use:

smtp_tls_ciphers = export
smtp_tls_protocols = !SSLv2, !SSLv3

You can also define where the file that holds all the root certificates on your linux server is, and thus to verify the certificate that provides an incoming mail server:

smtp_tls_CAfile = /etc/pki/tls/certs/ca-bundle.crt

I dont recommend to go higher with your setup, cause (unfortunately) not everyone is using TLS on their incoming mail server!

SMTPD - Incoming Traffic

To enable TLS in your incoming mail server, you need to provide some encryption keys aka certificates!

I use letsencrypt on my server and the below notes are based on that.

Let’s Encrypt

A quick explanation on what exists on your letsencrypt folder:

# ls -1 /etc/letsencrypt/live/example.com/

privkey.pem    ===>  You Private Key
cert.pem       ===>  Your Certificate
chain.pem      ===>  Your Intermediate
fullchain.pem  ===>  Your Certificate with Your Intermediate 

Postfix

Below you can find the most basic configuration setup you need for your incoming mail server.

smtpd_tls_ask_ccert = yes
smtpd_tls_security_level = may
smtpd_tls_loglevel = 1

Your mail server is asking for a certificate so that a trusted TLS connection can be established between outgoing and incoming mail server.
The servers must exchange certificates and of course, verify them!

Now, it’s time to present your own domain certificate to the world. Offering only your public certificate cert.pem isnt enough. You have to offer both your certificate and the intermediate’s certificate, so that the sender’s mail server can verify you, by checking the digital signatures on those certificates.

smtpd_tls_cert_file = /etc/letsencrypt/live/example.com/fullchain.pem
smtpd_tls_key_file = /etc/letsencrypt/live/example.com/privkey.pem

smtpd_tls_CAfile = /etc/pki/tls/certs/ca-bundle.crt
smtpd_tls_CApath = /etc/pki/tls/certs

CAfile & CApath helps postfix to verify the sender’s certificate by looking on your linux distribution file, that holds all the root certificates.

And you can also disable weak ciphers and protocols:


smtpd_tls_ciphers = high
smtpd_tls_exclude_ciphers = aNULL, MD5, EXPORT
smtpd_tls_protocols = !SSLv2, !SSLv3

Logs

Here is an example from gmail:

SMTPD - Incoming Mail from Gmail

You can see that there is a trusted TLS connection established From google:

Jun  4 11:52:07 kvm postfix/smtpd[14150]:
        connect from mail-oi0-x236.google.com[2607:f8b0:4003:c06::236]
Jun  4 11:52:08 kvm postfix/smtpd[14150]:
        Trusted TLS connection established from mail-oi0-x236.google.com[2607:f8b0:4003:c06::236]:
        TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)
Jun  4 11:52:09 kvm postfix/smtpd[14150]:
        4516420F32: client=mail-oi0-x236.google.com[2607:f8b0:4003:c06::236]
Jun  4 11:52:10 kvm postfix/smtpd[14150]:
        disconnect from mail-oi0-x236.google.com[2607:f8b0:4003:c06::236]

SMTP - Outgoing Mail from Gmail

And this is the response To gmail :

Jun  4 12:01:32 kvm postfix/smtpd[14808]:
        initializing the server-side TLS engine
Jun  4 12:01:32 kvm postfix/smtpd[14808]:
        connect from example.com[2a00:1838:20:1::XXXX:XXXX]
Jun  4 12:01:33 kvm postfix/smtpd[14808]:
        setting up TLS connection from example.com[2a00:1838:20:1::XXXX:XXXX]
Jun  4 12:01:33 kvm postfix/smtpd[14808]:
        example.com[2a00:1838:20:1::XXXX:XXXX]: TLS cipher list "aNULL:-aNULL:ALL:!EXPORT:!LOW:!MEDIUM:+RC4:@STRENGTH:!aNULL:!MD5:!EXPORT:!aNULL"
Jun  4 12:01:33 kvm postfix/smtpd[14808]:
        Anonymous TLS connection established from example.com[2a00:1838:20:1::XXXX:XXXX]:
        TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)
Jun  4 12:01:35 kvm postfix/smtpd[14808]:
        disconnect from example.com[2a00:1838:20:1::XXXX:XXXX]

As you can see -In both cases (sending/receiving)- the mail servers have established a trusted secure TLSv1.2 connection.
The preferred cipher (in both scenarios) is : ECDHE-RSA-AES128-GCM-SHA256

IPv6

Tell postfix to prefer ipv6 Vs ipv4 and use TLS if two mail servers support it !

#IPv6
smtp_address_preference = ipv6
Tag(s): postfix, tls, ipv6
May
02
2016
Use a different email address for every online account

Reading through “Smart Girl’s Guide to Privacy - Practical Tips for Staying Safe Online by Violet Blue” (totally recommend it), there is a great tip in the first few pages:

- Use different email addresses for different online accounts.

… but is it possible ?

Different Passwords

We already know that we need to use a different password for every site. So we use lastpass or password managers for keeping our different passwords safe. We are nowadays used to create/generate complex passwords for every site, but is it absolutely necessary to also have a different email address for every single one ?

Different Email Addresses

Let me be as clear as I can: There is no obvious answer.

If you value your online privacy and your security threat model is set really high, then Yes you also need a different email address.

But it depends entirely on you and how you use your online identity. Perhaps in social media sites (like facebook or twitter) you dont need to give your personal email address, but perhaps on linkedin you want to use your well-known email-identity. So again, it depends on your security thread model.

Another crucial tip: DO NOT cross-connect your online personas from different social medias.

Disposable Email Server

In this blog post, I will try to describe the simple steps you need to take, to create your own personal disposable email server. In simple words, that means that you can dynamically create and use a unique/specific-site-only email address that you can use for sign-up or register to a new site. Using a different email address & a different passwords for every site online, you are making it really difficult for someone to hack you.

Even if someone can get access to this specific website or -somehow- can retrieve your online account (sites are been hacked every day), you are sure that none of your other online accounts/identities can not be accessed too.

DOMAIN

To do that you will need a disposable domain. It does not have to be something clever or even useful. It needs to be something easy to write & remember. In my opinion, just get a cheap domain. If your registar support WHOIS Privacy, then even better. If dont, then try to find a registar that supports WHOIS Privacy but it isnt a blocking issue.

For this blog post I will use: example.org

Catch-All

In theory, we will create a “catch-all” domain/mail server, that will catch and forward all these emails to our current/primary email address.

DNS

So nice, you have a disposable domain. What next ?

You need to setup a new domain dns zone for your disposable domain.
And then add a MX record, like the notes below:



example.org.    86400   IN  MX  0 mail.example.org.
mail.example.org.   86400   IN  A   1.2.3.4

replace 1.2.3.4 with the server’s IP !!

Mail Server

Just install postfix !

My “notable” settings are these below:



# postconf -n

inet_interfaces = all
inet_protocols = all

message_size_limit = 35651584

smtp_address_preference = ipv6

smtpd_banner = The sky above the port was the color of television, tuned to a dead channel

virtual_alias_domains = example.org
virtual_alias_maps = hash:/etc/postfix/virtual

In my /etc/postfix/virtual I have these lines:


@example.org    my_email_address@example.net

(dont forget to postmap and reload)


# postmap /etc/postfix/virtual 

# postfix reload

…. and …. that is it, actually !!!

a. Be aware the my disposable email server is dual stack.

b. If you need to create an emailing list, try something like this:


list@example.org           my_email_address@example.net, my_other_email_address@gmail.com

dont forget to:


# postmap /etc/postfix/virtual

and reload postfix:


# postfix reload

How to use it

From now on, whenever you need to type an email address somewhere, just type a new (random or not) email address with this new disposable domain.

The catch-all setting will FWD any email to your primary email address.

I like to use the below specific pattern: When you need to sign-up to a new site, use the sites url as your new email address.


eg. twitter.com

twittercom@example.org

It’s now obvious that next time you get SPAM, you will know which one to blame (I am not suggesting that twitter is sending spam, it is just an example!).

You can also change your email address from all the sites that you have already subscribe (github, mailing lists, etc etc).

Hope this post has been helpful and easy enough for everyone.

Nov
25
2015
Sender Policy Framework

UPDATE Thu Nov 26 11:28:05 EET 2015

Does SPF break forwarding?
(like in mailing lists)

  • Yes, it does break forwarding.

So learn from my mistake and think this through.

Wednesday, 25 November 2015

There is a very simply way to add spf [check] support to your postfix setup.
Below are my notes on CentOS 6.7

Step One: install python policy daemon for spf


# yum -y install pypolicyd-spf

Step Two: Create a new postfix service, called spfcheck


# vim + /etc/postfix/master.cf

spfcheck     unix  -       n       n       -       -       spawn
    user=nobody argv=/usr/libexec/postfix/policyd-spf

Step Three: Add a new smtp daemon recipient restrictions


# vim +/^smtpd_recipient_restrictions /etc/postfix/main.cf
smtpd_recipient_restrictions =
    permit_mynetworks,
...
    check_policy_service unix:private/spfcheck
policy_time_limit = 3600

And that’s what we see in the end on a receiver’s source-view email:



Received-SPF: Pass (sender SPF authorized) identity=mailfrom; client-ip=xxx.xxx.xxx.xxx;
helo=server.mydomain.tld; envelope-from=user@mydomain.tld; receiver=username@example.com

where xxx.xxx.xxx.xxx is the IP of the sender mail server
server.mydomain.tld is the name of the sender mail server
user@mydomain.tld is the sender’s email address
and of-course
username@example.com is the receiver’s mail address

You can take a better look on postfix python SPF policy daemon by clicking here: python-postfix-policyd-spf

SPF Record Checker

Tag(s): postfix, spf
Jan
21
2015
greek spammers v3

Dec 1 2014 - Jan 21 2015

top five spammers:

1. adsgreece.com
2. mailendo.com
3. 4udeals.gr
4. eliamep.org
5. mailinglist.gr

Blocked via postfix:

/etc/postfix/header_checks


/massnews\.gr/                  REJECT  "Plz stop sending SPAM id= 1 "
/glc-emea\.com/                 REJECT  "Plz stop sending SPAM id= 2 "
/To:.*info@balaskas\.gr/        REJECT  "Plz stop sending SPAM id= 3 "
/Akis.Angelakis/i       REJECT  "Plz stop sending SPAM id= 4 "
/from.*mailendo.com/            REJECT  "Plz stop sending SPAM id= 5 "
/specisoft\.biz/                REJECT  "Plz stop sending SPAM id= 6 "
/advantech\.gr/                 REJECT  "Plz stop sending SPAM id= 7 "
/adsgreece\.com/                REJECT  "Plz stop sending SPAM id= 8 "
/2020web\.gr/                   REJECT  "Plz stop sending SPAM id= 9 "
/nfs\.gr/                       REJECT  "Plz stop sending SPAM id= 10 "
/polimonotiki/                  REJECT  "Plz stop sending SPAM id= 11 "
/eliamep\.org/                  REJECT  "Plz stop sending SPAM id= 12 "
/ellak\.gr/                     REJECT  "Plz stop sending SPAM id= 13 "
/seminaria\.gr/         REJECT  "Plz stop sending SPAM id= 14 "
/stock-house\.gr/       REJECT  "Plz stop sending SPAM id= 15 "
/Lesfemmes/i            REJECT  "Plz stop sending SPAM id= 16 "
/aldridge\.com/         REJECT  "Plz stop sending SPAM id= 17 "
/inter\.net/            REJECT  "Plz stop sending SPAM id= 18 "
/plexpr\.tk/            REJECT  "Plz stop sending SPAM id= 19 "
/industrydisruptors\.org/   REJECT  "Plz stop sending SPAM id= 20 "
/xinis\.com/            REJECT  "Plz stop sending SPAM id= 21 "
/globalgreece\.gr/      REJECT  "Plz stop sending SPAM id= 22 "
/hostzone\.gr/          REJECT  "Plz stop sending SPAM id= 23 "
/mailinglist\.gr/       REJECT  "Plz stop sending SPAM id= 24 "
/profitconsult\.gr/     REJECT  "Plz stop sending SPAM id= 25 "
/pedersenco\.com/       REJECT  "Plz stop sending SPAM id= 26 "
/diadima\.gr/           REJECT  "Plz stop sending SPAM id= 27 "
/helenco\.gr/           REJECT  "Plz stop sending SPAM id= 28 "
/adplus\.gr/            REJECT  "Plz stop sending SPAM id= 29 "
/entos\.gr/         REJECT  "Plz stop sending SPAM id= 30 "
/4udeals\.gr/           REJECT  "Plz stop sending SPAM id= 31 "
/oncseminars\.gr/       REJECT  "Plz stop sending SPAM id= 32 "
/enimerwsi\.gr/         REJECT  "Plz stop sending SPAM id= 33 "
/eliamep\.gr/           REJECT  "Plz stop sending SPAM id= 34 "
/ymlpsrv\.com/          REJECT  "Plz stop sending SPAM id= 35 "
/dailysoccertip\.com/       REJECT  "Plz stop sending SPAM id= 36 "
/bookbazaar\.gr/        REJECT  "Plz stop sending SPAM id= 37 "
/zizoo\.gr/         REJECT  "Plz stop sending SPAM id= 38 "
/anthemionflowers\.gr/      REJECT  "Plz stop sending SPAM id= 39 "
/kourkouta\.com/        REJECT  "Plz stop sending SPAM id= 40 "
/ipatata\.com/          REJECT  "Plz stop sending SPAM id= 41 "
/ephost\.info/          REJECT  "Plz stop sending SPAM id= 42 "
/kadoikonte\@gmail\.com/    REJECT  "Plz stop sending SPAM id= 43 "
/mandrillapp\.com/      REJECT  "Plz stop sending SPAM id= 44 "
/springer\.com/         REJECT  "Plz stop sending SPAM id= 45 "
/mailchimp\.com/        REJECT  "Plz stop sending SPAM id= 46 "
/altec\.gr/         REJECT  "Plz stop sending SPAM id= 47 "
/winizi\.net/           REJECT  "Plz stop sending SPAM id= 48 "
/sed\.gr/           REJECT  "Plz stop sending SPAM id= 49 "
/pournara\.com/         REJECT  "Plz stop sending SPAM id= 50 "
/emailmarketingnow\.gr/     REJECT  "Plz stop sending SPAM id= 51 "
/entypa\.net/           REJECT  "Plz stop sending SPAM id= 52 "
/4green\.gr/            REJECT  "Plz stop sending SPAM id= 53 "
/imagemail\.eu/         REJECT  "Plz stop sending SPAM id= 54 "
/cbr300r\.bike/         REJECT  "Plz stop sending SPAM id= 55 "
/PRINTEX\ DIGITAL/i        REJECT  "Plz stop sending SPAM id= 56 "
/drassi\.gr/            REJECT  "Plz stop sending SPAM id= 57 "
/mailstudio\.gr/        REJECT  "Plz stop sending SPAM id= 58 "
/extratips\.net/        REJECT  "Plz stop sending SPAM id= 59 "
/crmedia\.gr/           REJECT  "Plz stop sending SPAM id= 60 "
/venan\.gr/         REJECT  "Plz stop sending SPAM id= 61 "
/tonerflow\.info/       REJECT  "Plz stop sending SPAM id= 62 "
/epiteugma\.com/        REJECT  "Plz stop sending SPAM id= 63 "

Tag(s): Greek, spam, postfix
Dec
01
2014
greek spammers part two

Nov 2 2014 - Dec 1 2014

Top spammers:


1. adsgreece.com
2. globalgreece.gr
3. nfs.gr
4. specisoft.biz
5. aldridge.com

Blocked via postfix:

/etc/postfix/header_checks


/massnews\.gr/                  REJECT "Plz stop sending SPAM id=1"
/glc-emea\.com/                 REJECT "Plz stop sending SPAM id=2"
/To:.*info@balaskas\.gr/        REJECT "Plz stop sending SPAM id=3"
/Akis.Angelakis/        REJECT "Plz stop sending SPAM id=4"
/from.*mailendo.com/            REJECT "Plz stop sending SPAM id=5"
/specisoft\.biz/                REJECT "Plz stop sending SPAM id=6"
/advantech\.gr/                 REJECT "Plz stop sending SPAM id=7"
/adsgreece\.com/                REJECT "Plz stop sending SPAM id=8"
/2020web\.gr/                   REJECT "Plz stop sending SPAM id=9"
/nfs\.gr/                       REJECT "Plz stop sending SPAM id=10"
/polimonotiki/                  REJECT "Plz stop sending SPAM id=11"
/eliamep\.org/                  REJECT "Plz stop sending SPAM id=12"
/ellak\.gr/                     REJECT "Plz stop sending SPAM id=13"
/seminaria\.gr/         REJECT "Plz stop sending SPAM id=14"
/stock-house\.gr/       REJECT "Plz stop sending SPAM id=15"
/Lesfemmes/i            REJECT "Plz stop sending SPAM id=16"
/aldridge\.com/         REJECT "Plz stop sending SPAM id=17"
/inter\.net/            REJECT "Plz stop sending SPAM id=18"
/plexpr\.tk/            REJECT "Plz stop sending SPAM id=19"
/industrydisruptors\.org/   REJECT "Plz stop sending SPAM id=20"
/xinis\.com/            REJECT "Plz stop sending SPAM id=21"
/globalgreece\.gr/      REJECT "Plz stop sending SPAM id=22"
/hostzone\.gr/          REJECT "Plz stop sending SPAM id=23"
/mailinglist\.gr/       REJECT "Plz stop sending SPAM id=24"
/profitconsult\.gr/     REJECT "Plz stop sending SPAM id=25"
/pedersenco\.com/       REJECT "Plz stop sending SPAM id=26"
/diadima\.gr/           REJECT "Plz stop sending SPAM id=27"
/helenco\.gr/           REJECT "Plz stop sending SPAM id=28"
/adplus\.gr/            REJECT "Plz stop sending SPAM id=29"
/entos\.gr/         REJECT "Plz stop sending SPAM id=30"
/4udeals\.gr/           REJECT "Plz stop sending SPAM id=31"
/oncseminars\.gr/       REJECT "Plz stop sending SPAM id=32"
/enimerwsi\.gr/         REJECT "Plz stop sending SPAM id=33"

Tag(s): greek, spam, postfix
May
16
2014
postfix body and header checks

Postfix has the ability to DISCARD (or Reject) any email, by using simple regular expressions. This can be done on your incoming or outgoing mail farm and you can either check the header or body of an email.

For me header_checks is a more powerful tool but the main problem with phishing bots is that the headers arent always the same (different IPs, different Froms etc etc).

And on half of them scam situations there is an ugly url or email inside the body of the email.

Our abuse department informed us today for a scam bot that “WANTS YOU TO REPLY TO THEM WITH YOUR PASSWORDS” and we took the appropriate measures against it. None of our outgoing mail servers can be used to send a reply to the abuser mail address.

There is a debate in our team about future incoming of this specific scam bot. We could use body_check to silent DISCARD any new incoming mail but that also make it very difficult for us to communicate with each other.

The main problem is that i cant “report” to my manager about that OR the security/abuse department cant send me any email that has the “BAD email address” inside the body or our mails.

Tag(s): postfix
Aug
19
2011
postfix & dovecot LDA

Χρησιμοποιώ dovecot για imap και postfix για λήψη/αποστολή αλληλογραφίας.

Τους χρήστες της υποδομής τους έχω δημιουργήσει σε ένα dovecot userdb αρχείο.
Σε αυτό περιέχονται τα usernames, συνθηματικά πρόσβασης και πληροφορίες που σχετίζονται με το mail τους.
Ένα από αυτά είναι και ο τύπος του λογαριασμού κι ένα άλλο η τοποθεσία στην οποία αποθηκεύονται τα emails.

Στο αρχείο /etc/aliases έχω περασμένα τα FirstName.LastName aliases που δείχνουν στα username.

Το postfix ΔΕΝ έχει ιδέα για τους χρήστες - παρά μόνο για τα aliases.
Το postfix by default στέλνει reject στους Unknown users. Αφού λοιπόν μόνο ο dovecot ξέρει τους χρήστες, το postfix στέλνει reject για όλους.

Μία λύση είναι η δημιουργία ενός dovecot command στο master.cf κι αλλάζοντας το mail transport.
Αυτό όμως ΔΕΝ μου φάνηκε και πολύ καλή ιδέα.

Σε περίπτωση επίθεσης, το postfix θα αναλάβει να προωθήσει όλα τα emails στο dovecot.
Οπότε δεν θα περιορίσει κάτι, απλά θα μεταβιβάσει το πρόβλημα στο dovecot.
Το catch all options ήταν κάποτε (ίσως) λύση, μα πλέον είναι κατά την γνώμη μου λάθος να μπαίνει.

Σκέφτηκα να κάνω χρήση του dovecot-LDA, μα το postfix προσπαθεί να παραδώσει local τα emails επειδή βρήκε τα usernames & τα Ευάγγελος.Μπαλάσκας λογαριασμούς στο /etc/aliases. Έτσι δεν κάνει χρήση του mail_command γιατί χρησιμοποιεί το local.

Έτσι σκέφτηκα ότι η απλούστερη λύση είναι μονάχα η τροποποίηση του /etc/aliases, προσθέτοντας τα usernames με το αντίστοιχο dovecot-lda command

π.χ. “/etc/aliases”

Evaggelos.Balaskas: ebal
ebal: | “/usr/local/libexec/dovecot/deliver -d ebal”

Ακόμα και τώρα που το σκέφτομαι, θεωρώ ότι είναι η καλύτερη και απλούστερη λύση που μπορώ να σκεφτώ.

Μα τα προβλήματά μου, μόλις τώρα ξεκινάνε!!!
Κι όλα αυτά γιατί ο Wietse Venema θεώρησε καλό κάθε service να τρέχει με διαφορετικό χρήστη και να μην έχουν πρόσβαση στα ίδια πράγματα. Στα ίδια πρότυπα λειτουργεί και ο Timo Sirainen (dovecot).

Τώρα δεν φταίει αυτός - το αυτονόητο έκανε. Πρόσθεσε ασφάλεια!

Ο mail owner του postfix είναι ο postfix μα τα δικαιώματα που κληρονομούνται στις διεργασίες είναι του nobody.
Έτσι χθες κατέληξα στο πρόβλημα, πως ο nobody θα μιλήσει με τον dovecot που εκτελείτε ως postfix (για χάρη ευκολίας) . Μα o dovecot deliver πρέπει να μιλήσει στο auth-userdb για να πάρει το mail_location, το οποίο έχει και setuid κι όλα αυτά τρέχουν ως root.

Μα ακόμα κι εάν τα έφτιαξα όλα αυτά … έφτασα στο συμπέρασμα ότι οι virtual users, ανήκουν σε διαφορετικό uid/gid και δεν μπορεί να τα παραδώσει εν τέλη! Οπότε πρέπει να διορθώσω κι αυτό …

Αλλά μετά από όλα αυτά - έπαιξε !!!

Για κάθε αλλαγή στο dovecot userdb, θα πρέπει να κάνω μια παρόμοια αλλαγή στο /etc/aliases. ΑΛΛΑ δεν χρειάζεται να αλλάξω κάτι στην αρχιτεκτονική ή στα configuration files των δαιμόνων.

Tag(s): postfix, dovecot