Hello all: I'm running Stunnel 4.52 under WinXP SP3. Last night I had some questions about how the cipher list in Stunnel interacts with the cipher negotiation routine between client and server, so I did some experiments in an attempt to address those questions. In the course of doing so, I noticed that, if I attempt to load certain ciphers, Stunnel would stall at configuration load. Using OpenSSL to list TLS ciphers with 4.52's libraries yields the following: ~~~~~~~~~~~~~~~~~~~~~ C:\Program Files\stunnel>openssl ciphers -v -tls1 DHE-RSA-AES256-SHA SSLv3 Kx=DH Au=RSA Enc=AES(256) Mac=SHA1 DHE-DSS-AES256-SHA SSLv3 Kx=DH Au=DSS Enc=AES(256) Mac=SHA1 AES256-SHA SSLv3 Kx=RSA Au=RSA Enc=AES(256) Mac=SHA1 EDH-RSA-DES-CBC3-SHA SSLv3 Kx=DH Au=RSA Enc=3DES(168) Mac=SHA1 EDH-DSS-DES-CBC3-SHA SSLv3 Kx=DH Au=DSS Enc=3DES(168) Mac=SHA1 DES-CBC3-SHA SSLv3 Kx=RSA Au=RSA Enc=3DES(168) Mac=SHA1 DHE-RSA-AES128-SHA SSLv3 Kx=DH Au=RSA Enc=AES(128) Mac=SHA1 DHE-DSS-AES128-SHA SSLv3 Kx=DH Au=DSS Enc=AES(128) Mac=SHA1 AES128-SHA SSLv3 Kx=RSA Au=RSA Enc=AES(128) Mac=SHA1 IDEA-CBC-SHA SSLv3 Kx=RSA Au=RSA Enc=IDEA(128) Mac=SHA1 RC4-SHA SSLv3 Kx=RSA Au=RSA Enc=RC4(128) Mac=SHA1 RC4-MD5 SSLv3 Kx=RSA Au=RSA Enc=RC4(128) Mac=MD5 EDH-RSA-DES-CBC-SHA SSLv3 Kx=DH Au=RSA Enc=DES(56) Mac=SHA1 EDH-DSS-DES-CBC-SHA SSLv3 Kx=DH Au=DSS Enc=DES(56) Mac=SHA1 DES-CBC-SHA SSLv3 Kx=RSA Au=RSA Enc=DES(56) Mac=SHA1 EXP-EDH-RSA-DES-CBC-SHA SSLv3 Kx=DH(512) Au=RSA Enc=DES(40) Mac=SHA1 export EXP-EDH-DSS-DES-CBC-SHA SSLv3 Kx=DH(512) Au=DSS Enc=DES(40) Mac=SHA1 export EXP-DES-CBC-SHA SSLv3 Kx=RSA(512) Au=RSA Enc=DES(40) Mac=SHA1 export EXP-RC2-CBC-MD5 SSLv3 Kx=RSA(512) Au=RSA Enc=RC2(40) Mac=MD5 export EXP-RC4-MD5 SSLv3 Kx=RSA(512) Au=RSA Enc=RC4(40) Mac=MD5 export C:\Program Files\stunnel> ~~~~~~~~~~~~~~~~~~~~~ As such, ciphers RC4-SHA and RC4-MD5 appear to be valid. However, any attempt at using those in client mode causes Stunnel to stall when reading the cipher from stunnel.conf: ~~~~~~~~~~~~~~~~~~~~~ 2012.03.08 20:17:10 LOG5[432:592]: Reading configuration from file stunnel.conf 2012.03.08 20:17:10 LOG5[432:592]: FIPS mode is enabled 2012.03.08 20:17:10 LOG7[432:592]: Compression not enabled 2012.03.08 20:17:10 LOG7[432:592]: Snagged 64 random bytes from C:/.rnd 2012.03.08 20:17:10 LOG7[432:592]: Wrote 1024 new random bytes to C:/.rnd 2012.03.08 20:17:10 LOG7[432:592]: PRNG seeded successfully 2012.03.08 20:17:10 LOG6[432:592]: Initializing SSL context for service nntps.1 2012.03.08 20:17:10 LOG7[432:592]: Loaded verify certificates from peer-nntps.1.pem 2012.03.08 20:17:10 LOG7[432:592]: Loaded peer-nntps.1.pem revocation lookup file 2012.03.08 20:17:10 LOG7[432:592]: SSL options set: 0x00000004 2012.03.08 20:17:10 LOG6[432:592]: SSL context initialized 2012.03.08 20:17:10 LOG6[432:592]: Initializing SSL context for service nntps.2 2012.03.08 20:17:10 LOG7[432:592]: Loaded verify certificates from peer-nntps.2.pem 2012.03.08 20:17:10 LOG7[432:592]: Loaded peer-nntps.2.pem revocation lookup file 2012.03.08 20:17:10 LOG3[432:592]: SSL_CTX_set_cipher_list: 1410D0B9: error:1410D0B9:SSL routines:SSL_CTX_set_cipher_list:no cipher match 2012.03.08 20:17:10 LOG3[432:592]: Failed to reload the configuration file 2012.03.08 20:17:10 LOG7[432:592]: Signal pipe is empty ~~~~~~~~~~~~~~~~~~~~ This is the relevant snippet from my stunnel.conf file: ~~~~~~~~~~~~~~~~~~~~ debug = 7 delay = yes output = stunnel.log [nntps.1] client = yes sslVersion = TLSv1 ciphers = DHE-RSA-AES256-SHA:DHE-DSS-AES256-SHA:AES256-SHA cafile = peer-nntps.1.pem verify = 4 accept = 127.0.1.1:119 connect = news.server.com:443 [nntps.2] client = yes sslVersion = TLSv1 ciphers = RC4-SHA cafile = peer-nntps.2.pem verify = 4 accept = 127.0.1.2:119 connect = news.server.org:563 ~~~~~~~~~~~~~~~~~~~~ Any attempt at using ciphers RC4-SHA or RC4-MD5. with or without TLS specified, results in the same configuration crash. I don't really need to use those ciphers, but since I observed this behavior, I thought I'd better report it. Any comments welcome. Regards; Thomas . -- Attention: This message and all attachments are private and may contain information that is confidential and privileged. If you received this message in error, please notify the sender by reply email and delete the message immediately.