Il Server Perfetto - CentOS 5.6 x86_64 [ISPConfig 2] - Pagina 5

11 Postfix Con SMTP-AUTH E TLS

Ora installiamo Postfix e Dovecot (Dovecot sarà il nostro server POP3/IMAP):

yum install cyrus-sasl cyrus-sasl-devel cyrus-sasl-gssapi cyrus-sasl-md5 cyrus-sasl-plain postfix dovecot

Successivamente configuriamo SMTP-AUTH e TLS:

postconf -e ‘smtpd_sasl_local_domain =’ postconf -e ‘smtpd_sasl_auth_enable = yes’ postconf -e ‘smtpd_sasl_security_options = noanonymous’ postconf -e ‘broken_sasl_auth_clients = yes’ postconf -e ‘smtpd_sasl_authenticated_header = yes’ postconf -e ‘smtpd_recipient_restrictions = permit_sasl_authenticated,permit_mynetworks,reject_unauth_destination’ postconf -e ‘inet_interfaces = all’ postconf -e ‘mynetworks = 127.0.0.0/8’

Dobbiamo modificare /usr/lib64/sasl2/smtpd.conf in modo che Postfix consenta accessi PLAIN e LOGIN. Su un Centos 5.6 a 32 bit devi modificare il file /usr/lib/sasl2/smtpd.conf invece. Dovrebbe apparire così:

vi /usr/lib64/sasl2/smtpd.conf

| pwcheck_method: saslauthd mech_list: plain login |

Dopo creiamo i certificati per TLS:

mkdir /etc/postfix/ssl
cd /etc/postfix/ssl/
openssl genrsa -des3 -rand /etc/hosts -out smtpd.key 1024

chmod 600 smtpd.key
openssl req -new -key smtpd.key -out smtpd.csr

openssl x509 -req -days 3650 -in smtpd.csr -signkey smtpd.key -out smtpd.crt

openssl rsa -in smtpd.key -out smtpd.key.unencrypted

mv -f smtpd.key.unencrypted smtpd.key
openssl req -new -x509 -extensions v3_ca -keyout cakey.pem -out cacert.pem -days 3650

Successivamente configuriamo Postfix per TLS:

postconf -e ‘smtpd_tls_auth_only = no’ postconf -e ‘smtp_use_tls = yes’ postconf -e ‘smtpd_use_tls = yes’ postconf -e ‘smtp_tls_note_starttls_offer = yes’ postconf -e ‘smtpd_tls_key_file = /etc/postfix/ssl/smtpd.key’ postconf -e ‘smtpd_tls_cert_file = /etc/postfix/ssl/smtpd.crt’ postconf -e ‘smtpd_tls_CAfile = /etc/postfix/ssl/cacert.pem’ postconf -e ‘smtpd_tls_loglevel = 1’ postconf -e ‘smtpd_tls_received_header = yes’ postconf -e ‘smtpd_tls_session_cache_timeout = 3600s’ postconf -e ‘tls_random_source = dev:/dev/urandom’

Poi impostiamo il nome host nella nostra installazione di Postfix (assicurati di sostituire server1.example.com con il tuo nome host):

postconf -e 'myhostname = server1.example.com'

Dopo questi passaggi di configurazione dovresti avere un /etc/postfix/main.cf che appare così (ho rimosso tutti i commenti):

cat /etc/postfix/main.cf

| queue_directory = /var/spool/postfix command_directory = /usr/sbin daemon_directory = /usr/libexec/postfix mail_owner = postfix inet_interfaces = all mydestination = $myhostname, localhost.$mydomain, localhost unknown_local_recipient_reject_code = 550 alias_maps = hash:/etc/aliases alias_database = hash:/etc/aliases debug_peer_level = 2 debugger_command = PATH=/bin:/usr/bin:/usr/local/bin:/usr/X11R6/bin xxgdb $daemon_directory/$process_name $process_id & sleep 5 sendmail_path = /usr/sbin/sendmail.postfix newaliases_path = /usr/bin/newaliases.postfix mailq_path = /usr/bin/mailq.postfix setgid_group = postdrop html_directory = no manpage_directory = /usr/share/man sample_directory = /usr/share/doc/postfix-2.3.3/samples readme_directory = /usr/share/doc/postfix-2.3.3/README_FILES smtpd_sasl_local_domain = smtpd_sasl_auth_enable = yes smtpd_sasl_security_options = noanonymous broken_sasl_auth_clients = yes smtpd_sasl_authenticated_header = yes smtpd_recipient_restrictions = permit_sasl_authenticated,permit_mynetworks,reject_unauth_destination mynetworks = 127.0.0.0/8 smtpd_tls_auth_only = no smtp_use_tls = yes smtpd_use_tls = yes smtp_tls_note_starttls_offer = yes smtpd_tls_key_file = /etc/postfix/ssl/smtpd.key smtpd_tls_cert_file = /etc/postfix/ssl/smtpd.crt smtpd_tls_CAfile = /etc/postfix/ssl/cacert.pem smtpd_tls_loglevel = 1 smtpd_tls_received_header = yes smtpd_tls_session_cache_timeout = 3600s tls_random_source = dev:/dev/urandom myhostname = server1.example.com |

Per impostazione predefinita, il demone Dovecot di CentOS fornisce solo servizi IMAP e IMAPs. Poiché vogliamo anche POP3 e POP3s, dobbiamo configurare Dovecot per farlo. Modifichiamo /etc/dovecot.conf e abilitiamo la riga protocols = imap imaps pop3 pop3s:

vi /etc/dovecot.conf

| [...] # Protocols we want to be serving: imap imaps pop3 pop3s # If you only want to use dovecot-auth, you can set this to "none". protocols = imap imaps pop3 pop3s [...] |

Ora avvia Postfix, saslauthd e Dovecot:

chkconfig –levels 235 sendmail off
chkconfig –levels 235 postfix on
chkconfig –levels 235 saslauthd on
chkconfig –levels 235 dovecot on
/etc/init.d/sendmail stop
/etc/init.d/postfix start
/etc/init.d/saslauthd start
/etc/init.d/dovecot start

Per vedere se SMTP-AUTH e TLS funzionano correttamente, esegui il seguente comando:

telnet localhost 25 

Dopo aver stabilito la connessione al tuo server di posta Postfix, digita

ehlo localhost 

Se vedi le righe

250-STARTTLS 

e

250-AUTH LOGIN PLAIN 

tutto va bene.

[root@server1 ssl]# telnet localhost 25
Trying 127.0.0.1…
Connected to localhost.localdomain (127.0.0.1).
Escape character is ‘^]’.
220 server1.example.com ESMTP Postfix
ehlo localhost
250-server1.example.com
250-PIPELINING
250-SIZE 10240000
250-VRFY
250-ETRN
250-STARTTLS
250-AUTH LOGIN PLAIN
250-AUTH=LOGIN PLAIN
250-ENHANCEDSTATUSCODES
250-8BITMIME
250 DSN
quit
221 2.0.0 Bye
Connection closed by foreign host.
[root@server1 ssl]#

Digita

quit 

per tornare alla shell del sistema.

11.1 Maildir

Dovecot utilizza il formato Maildir (non mbox), quindi se installi ISPConfig sul server, assicurati di abilitare Maildir sotto Gestione -> Server -> Impostazioni -> Email. ISPConfig eseguirà quindi la configurazione necessaria.

Se non vuoi installare ISPConfig, allora devi configurare Postfix per consegnare le email nella Maildir di un utente (puoi anche farlo se usi ISPConfig - non fa male ;-)):

postconf -e ‘home_mailbox = Maildir/‘
postconf -e ‘mailbox_command =’
/etc/init.d/postfix restart