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Accepted
ethrbunny
Asked: 2013-11-05 05:07:39 +0800 CST

nagios: trouble using check_smtps command

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I'm trying to use this command to check on port 587 for my postfix server.

Using nmap -P0 mail.server.com I see this:

Starting Nmap 5.51 ( http://nmap.org ) at 2013-11-04 05:01 PST
Nmap scan report for mail.server.com (xx.xx.xx.xx)
Host is up (0.0016s latency).
rDNS record for xx.xx.xx.xx: another.server.com
Not shown: 990 closed ports
PORT     STATE SERVICE
22/tcp   open  ssh
25/tcp   open  smtp
110/tcp  open  pop3
111/tcp  open  rpcbind
143/tcp  open  imap
465/tcp  open  smtps
587/tcp  open  submission
993/tcp  open  imaps
995/tcp  open  pop3s
5666/tcp open  nrpe

So I know the relevant ports for smtps (465 or 587) are open.

When I use openssl s_client -connect mail.server.com:587 -starttls smtp I get a connection with all the various SSL info. (Same for port 465).

But when I try libexec/check_ssmtp -H mail.server.com -p587 I get:

CRITICAL - Cannot make SSL connection.
140200102082408:error:140770FC:SSL routines:SSL23_GET_SERVER_HELLO:unknown protocol:s23_clnt.c:699:

What am I doing wrong?

nagios

1 Answers

  1. Best Answer

    You need to use the -S flag with the check_smtp command, as MadHatter correctly states, the check_ssmtp plugin is for SSL enabled SMTP only.

    MadHatter adds (with NickW's kind permission):

    This is from tcpdump -n -n -X host www.teaparty.net on my NAGIOS server, whilst at the same time running /usr/lib64/nagios/plugins/check_smtp -H www.teaparty.net -p 25 -S. You'll note that TLS is clearly requested and initiated (I have cut out all the tedious certificate exchange that happened immediately afterwards).

    14:28:37.434337 IP 78.31.111.49.33974 > 178.18.123.145.25: Flags [P.], seq 27:37, ack 276, win 123, options [nop,nop,TS val 890100881 ecr 1034540785], length 10
    0x0000:  4500 003e e415 4000 4006 6bb0 4e1f 6f31  E..>..@[email protected]
    0x0010:  b212 7b91 84b6 0019 b7e2 38ba ce7c 896e  ..{.......8..|.n
    0x0020:  8018 007b eb24 0000 0101 080a 350d dc91  ...{.$......5...
    0x0030:  3da9 d6f1 5354 4152 5454 4c53 0d0a       =...STARTTLS..
14:28:37.438207 IP 178.18.123.145.25 > 78.31.111.49.33974: Flags [P.], seq 276:306, ack 37, win 114, options [nop,nop,TS val 1034540789 ecr 890100881], length 30
    0x0000:  4500 0052 5e89 4000 3906 f828 b212 7b91  E..R^[email protected]..(..{.
    0x0010:  4e1f 6f31 0019 84b6 ce7c 896e b7e2 38c4  N.o1.....|.n..8.
    0x0020:  8018 0072 806e 0000 0101 080a 3da9 d6f5  ...r.n......=...
    0x0030:  350d dc91 3232 3020 322e 302e 3020 5265  5...220.2.0.0.Re
    0x0040:  6164 7920 746f 2073 7461 7274 2054 4c53  ady.to.start.TLS
    0x0050:  0d0a                                     ..
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