Hi,

we have a strange problem with newer stunnel versions (4.50 on windows), compared to older ones (known to work is version 4.35). The problem seems to be, that if a client sends a SSLv2 Helo message, the stunnel server simply resets the TCP connection, without trying to negotioate anything.

Setup: Stunnel is used top provide ssl/tls for imap, Hobbit is used to monitor service availability. The Hobbit module to monitor imaps seems to try SSLv2 first, but also supports newer versions (SSLv3 and TLSv1). The ssl connection never gets established, stunnel sends a tcp RST, hobbit never retries. We can force some hobbit modules to use TLSv1 exclusively, but not all of them. We fear that some older mailclients will also have problems initiating a connection, so we keep stunnel 4.35 running for now.

stunnel.conf:

fips = no debug = 7 output = stunnel.log

[imaps] accept = 130.83.174.1:993 connect = 127.0.0.1:143 cert = imap.xxx.company.yy.pem

stunnel.log:

2011.12.09 14:55:12 LOG5[6820:2144]: Service imaps accepted connection from xxx.yyy.zzz.105:45294 2011.12.09 14:55:12 LOG3[6820:2144]: SSL_accept: 1408F10B: error:1408F10B:SSL routines:SSL3_GET_RECORD:wrong version number 2011.12.09 14:55:12 LOG5[6820:2144]: Connection reset: 0 bytes sent to SSL, 0 bytes sent to socket 2011.12.09 14:55:12 LOG7[6820:2144]: Service imaps finished (0 left) 2011.12.09 14:55:12 LOG7[6820:2144]: str_stats: 0 block(s), 0 data byte(s), 0 control byte(s)

Wireshark Packet Trace (see attached image).

What's wrong here? Shouldn't client and server negotiate the methods used? The client seems to offer TLS ("Version: TLS 1.0 ..."), but instead of negotiating, the server simply closes the connection.

Greetings Markus Borst