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When running PCI security scans on this server it fails on port 25 with:

SSL Server Supports Weak Encryption nCircle ID: 6174 Port: 25 CVSS Score: 5.8 Not Compliant Description The SSL (Secure Socket Layer) Server supports weak encryption keys, which are defined as encryption keys with lengths of less than 128 bits. Messages encrypted with weak encryption keys are relatively easy for an unauthorized user to decrypt.

I have tried modifying /etc/postfix/main.cf with various changes:

  • postconf -e smtpd_tls_mandatory_protocols="SSLv3,TLSv1"
  • postconf -e smtpd_tls_mandatory_ciphers="high"
  • postconf -e smtpd_tls_exclude_ciphers="SSLv2,aNULL,ADH,eNULL"

No luck. This is the only port which fails the scan. My web and IMAP pots are all fine.

Any suggestions appreciated.

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Did you restart or HUP the postfix SMTP process after your configuration changes? –  brent Sep 7 '10 at 16:16
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1 Answer

One document I found recommends the following settings for PCI compliance:

postconf -e smtpd_tls_ciphers=medium
postconf -e smtpd_tls_protocols=\!SSLv2
postconf -e smtpd_tls_mandatory_ciphers=high
postconf -e smtpd_tls_exclude_ciphers="aNULL, MD5, DES"

Then restart the postfix daemon for good measure.
The document is actually for an unrelated VMWare product, but postfix is postfix, right?

;-)

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