I just finished building and configuring stunnel 4.42 on my x86_64 CentOS6 box. It appears to run, but not long into the SSL connection stunnel dies. Log info below. This only happens if I do NOT specify --disable-fips during ./configure (as it enables FIPS by default). I assume this is because FIPS compliancy requires a key to have a passphrase, which my key does not have? [root@host stunnel]# tail -f /var/log/stunnel.log /var/log/messages ==> /var/log/stunnel.log <== 2011.08.19 16:27:36 LOG7[31681:139656510936832]: Option TCP_NODELAY set on local socket 2011.08.19 16:27:36 LOG5[31681:139656510936832]: Service ntop accepted connection from 12.117.176.190:13258 2011.08.19 16:27:36 LOG7[31681:139656510936832]: SSL state (accept): before/accept initialization 2011.08.19 16:27:36 LOG7[31681:139656510936832]: SSL state (accept): SSLv3 read client hello A 2011.08.19 16:27:36 LOG7[31681:139656510936832]: SSL state (accept): SSLv3 write server hello A 2011.08.19 16:27:36 LOG7[31681:139656510936832]: SSL state (accept): SSLv3 write certificate A 2011.08.19 16:27:36 LOG7[31681:139656510936832]: SSL state (accept): SSLv3 write key exchange A 2011.08.19 16:27:36 LOG7[31681:139656510936832]: SSL state (accept): SSLv3 write server done A 2011.08.19 16:27:36 LOG7[31681:139656510936832]: SSL state (accept): SSLv3 flush data 2011.08.19 16:27:37 LOG7[31681:139656510936832]: SSL state (accept): SSLv3 read client key exchange A ==> /var/log/messages <== Aug 19 16:27:24 host stunnel: LOG5[31680:139656510941120]: FIPS mode enabled Aug 19 16:27:24 host stunnel: LOG6[31680:139656510941120]: Initializing SSL context for service ntop Aug 19 16:27:24 host stunnel: LOG4[31680:139656510941120]: Insecure file permissions on /usr/local/etc/stunnel/stunnel.pem Aug 19 16:27:24 host stunnel: LOG6[31680:139656510941120]: SSL context initialized Aug 19 16:27:24 host stunnel: LOG5[31680:139656510941120]: Configuration successful Aug 19 16:27:36 host stunnel: LOG5[31681:139656510936832]: Service ntop accepted connection from 12.117.176.190:13257 Aug 19 16:27:36 host stunnel: LOG3[31681:139656510936832]: SSL_accept: 1408F10B: error:1408F10B:SSL routines:SSL3_GET_RECORD:wrong version number Aug 19 16:27:36 host stunnel: LOG5[31681:139656510936832]: Connection reset: 0 bytes sent to SSL, 0 bytes sent to socket Aug 19 16:27:36 host stunnel: LOG5[31681:139656510936832]: Service ntop accepted connection from 12.117.176.190:13258 Aug 19 16:27:37 host kernel: stunnel[31724] trap divide error ip:7f044fd0d3d1 sp:7f0450b98a40 error:0 in libssl.so.1.0.0[7f044fce2000+53000]