Sunday, January 14, 2018

Make 'bts' (devscripts) accept TLS connection to mail server with self signed certificate

My mail server runs with a self signed certificate. So bts, configured like this ...

BTS_SMTP_HOST=mail.wgdd.de:587
BTS_SMTP_AUTH_USERNAME='user'
BTS_SMTP_AUTH_PASSWORD='pass'

...lately refused to send mails with this error:

bts: failed to open SMTP connection to mail.wgdd.de:587
(SSL connect attempt failed error:1416F086:SSL routines:tls_process_server_certificate:certificate verify failed)

After searching a bit, I found a way to fix this locally without turning off the server certificate verification. The fix belongs into the send_mail() function. When calling the Net::SMTPS->new() constructor, it is possible to add the fingerprint of my self signed certificate like this (bold):

if (have_smtps) {
    $smtp = Net::SMTPS->new($host, Port => $port,
        Hello => $smtphelo, doSSL => 'starttls',
        SSL_fingerprint => 'sha1$hex-fingerprint')
        or die "$progname: failed to open SMTP connection to $smtphost\n($@)\n";
} else {
    $smtp = Net::SMTP->new($host, Port => $port, Hello => $smtphelo)
        or die "$progname: failed to open SMTP connection to $smtphost\n($@)\n";
}

Pretty happy to being able to use the bts command again.

2 comments:

  1. I solved the same issue by just making my MTA use Let’s Encrypt, and that’s something I recommend you do too ;)

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