Re: [stunnel-users] Stunnel.conf won't load with certain ciphers.

Parting thoughts.

One of the striking differences between version 4.47 and 4.52, in my experience, is that version 4.47 does not negotiate for strong ciphers in client mode with a "plain vanilla" stunnel.conf. With 4.47, if I do not specify which ciphers to use, the session always uses a 128-bit cipher. Even if I specify sslVersion = TLSv1 in stunnel.conf, the session still defaults to something like RC4-SHA. When I first observed this behavior, it didn't make sense to me.

From Wiki on TLS:

[quote]

The handshake begins when a client connects to a TLS-enabled server requesting a secure connection and presents a list of supported cipher suites (ciphers and hash functions).

From this list, the server picks the strongest cipher and hash function that it also supports and notifies the client of the decision.

[/quote]

Which is not what was happening. All of the servers I connect to support 256-bit ciphers, but I wasn't getting that level of encryption until I specifically told Stunnel which ciphers to use.

With version 4.52, I don't have to specify any ciphers at all in stunnel.conf. I always end up with strong encryption, even without sslVersion = TLSv1 .

In any case, things are back up and working as expected once again. I think I'll call it a night.

To all of Stunnel's developers/contributors.. thanks for making this great utility available. What a fantastic learning experience this has been.

Regards;

Thomas

On 3/8/2012 11:40 PM, Thomas Eifert wrote:

Update:

I uninstalled version 4.52, then reinstalled version 4.47. RC4-SHA cipher now works correctly, with the same stunnel.conf.

2012.03.08 23:36:50 LOG5[420:580]: stunnel 4.47 on x86-pc-mingw32-gnu 
platform
2012.03.08 23:36:50 LOG5[420:580]: Compiled/running with OpenSSL 
1.0.0e 6 Sep 2011
2012.03.08 23:36:50 LOG5[420:580]: Threading:WIN32 SSL:ENGINE 
Auth:none Sockets:SELECT,IPv6
2012.03.08 23:36:50 LOG5[420:580]: Reading configuration from file 
stunnel.conf
2012.03.08 23:36:50 LOG6[420:580]: Initializing SSL context for 
service nntps.1
2012.03.08 23:36:50 LOG6[420:580]: SSL context initialized
2012.03.08 23:36:50 LOG6[420:580]: Initializing SSL context for 
service nntps.2
2012.03.08 23:36:50 LOG6[420:580]: SSL context initialized
2012.03.08 23:36:50 LOG5[420:580]: Configuration successful
2012.03.08 23:37:08 LOG5[420:2804]: Service nntps.2 accepted 
connection from 127.0.1.2:1033
2012.03.08 23:37:08 LOG6[420:2804]: connect_blocking: connecting 
88.198.244.100:563
2012.03.08 23:37:09 LOG5[420:2804]: connect_blocking: connected 
88.198.244.100:563
2012.03.08 23:37:09 LOG5[420:2804]: Service nntps.2 connected remote 
server from 173.89.4.172:1034
2012.03.08 23:37:09 LOG5[420:2804]: Certificate accepted: depth=2, 
/C=IL/O=StartCom Ltd./OU=Secure Digital Certificate 
Signing/CN=StartCom Certification Authority
2012.03.08 23:37:09 LOG5[420:2804]: Certificate accepted: depth=1, 
/C=IL/O=StartCom Ltd./OU=Secure Digital Certificate 
Signing/CN=StartCom Class 1 Primary Intermediate Server CA
2012.03.08 23:37:09 LOG6[420:2804]: CERT: Locally installed 
certificate matched
2012.03.08 23:37:09 LOG5[420:2804]: Certificate accepted: depth=0, 
/description=436134-bRSt8Rml1Sum890r/CN=news.eternal-september.org/emailAddress=wolfgang@weyand-hg.de 

2012.03.08 23:37:09 LOG6[420:2804]: SSL connected: new session negotiated
2012.03.08 23:37:09 LOG6[420:2804]: Negotiated ciphers: RC4-SHA SSLv3 
Kx=RSA Au=RSA Enc=RC4(128) Mac=SHA1
2012.03.08 23:37:20 LOG6[420:2804]: SSL_shutdown successfully sent 
close_notify
2012.03.08 23:37:20 LOG5[420:2804]: Connection closed: 1251 bytes sent 
to SSL, 1861 bytes sent to socket

Regards;

Thomas

On 3/8/2012 8:44 PM, Thomas Eifert wrote:
> 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
> .
>