Date: Sat, 7 Mar 2015 17:32:05 -0800 From: Doug Hardie <bc979@lafn.org> To: Doug Hardie <bc979@lafn.org> Cc: FreeBSD - <freebsd-questions@freebsd.org>, owner-freebsd-questions@freebsd.org Subject: Re: OpenSSL Ciphers Message-ID: <70654C1C-913A-4406-B904-697E153646E0@lafn.org> In-Reply-To: <79CC9795-C5EF-451A-9A49-A2847E7C5974@lafn.org> References: <5347DC2D-AD6C-41A1-AEC7-A81C51F691B3@lafn.org> <B8A83AF6-B354-46E7-A736-64959C53CD66@lafn.org> <DC459F71-D819-4BB9-AC1A-4E1D5EB6D4E8@mac.com> <031A70A3-C348-4E2A-8C30-79F85BA4B4A1@lafn.org> <a579dadbf9688db6e2b257f76a441cc1@dweimer.net> <A0FAE283-534A-4C99-B5A0-43C219AB7065@lafn.org> <4d416c9dfa4e2922174ff469313578a0@dweimer.net> <79CC9795-C5EF-451A-9A49-A2847E7C5974@lafn.org>
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> On 7 March 2015, at 15:13, Doug Hardie <bc979@lafn.org> wrote: >=20 >=20 >> On 7 March 2015, at 08:49, dweimer <dweimer@dweimer.net> wrote: >>=20 >> On 03/07/2015 1:35 am, Doug Hardie wrote: >>>> On 6 March 2015, at 17:35, dweimer <dweimer@dweimer.net> wrote: >>>> On 03/06/2015 6:36 pm, Doug Hardie wrote: >>>>>> On 6 March 2015, at 16:28, Charles Swiger <cswiger@mac.com> = wrote: >>>>>> Hi-- >>>>>>> On Mar 6, 2015, at 3:58 PM, Doug Hardie <bc979@lafn.org> wrote: >>>>>>>> On 3 March 2015, at 23:21, Doug Hardie <bc979@lafn.org> wrote: >>>>>>>> The default list of ciphers is quite extensive and includes = some that are apparently causing some potential security issues. I have = a number of applications that use OpenSSL and many don=E2=80=99t have = the code to restrict the list. Fixing all that would take quite a bit = of work. However, looking into /usr/include/openssl/ssl.h I find a = definition for the SSL_DEFAULT_CIPHER_LIST. The comments indicate that = that list is the one used when the application doesn=E2=80=99t specify = anything. I changed its definition to: >>>>>>>> #define SSL_DEFAULT_CIPHER_LIST = "TLSv1+HIGH:!SSLv2:RC4+MEDIUM:!aNULL:!eNULL:!3DES:@STRENGTH: >>>>>>>> However, s_connect will still create a connection with the = export ciphers. I tried adding !EXPORT to that list and it had no = effect. Is the definition actually used by openssl or is it just there = for documentation? >>>>>>> Not hearing anything on this, I suspect it=E2=80=99s not very = well understood. I have started updating the various servers/clients = that use SSL/TLS. The one that has me completely stumped is sendmail. = There is a web page which provides instructions = "http://novosial.org/sendmail/cipherlist/index.html=E2=80=9D. However, = when I follow them, I can still establish a connection and deliver mail = using the export ciphers. >>>>>>> Has anyone successfully restricted the sendmail ciphers? >>>>>> You can see which ciphers openssl will support via a statement = like: >>>>>> % openssl ciphers -v = 'TLSv1+HIGH:RC4+MEDIUM:!aNULL:!eNULL:!3DES:@STRENGTH:!EXPORT' >>>>>> DHE-RSA-AES256-SHA SSLv3 Kx=3DDH Au=3DRSA = Enc=3DAES(256) Mac=3DSHA1 >>>>>> DHE-DSS-AES256-SHA SSLv3 Kx=3DDH Au=3DDSS = Enc=3DAES(256) Mac=3DSHA1 >>>>>> AES256-SHA SSLv3 Kx=3DRSA Au=3DRSA = Enc=3DAES(256) Mac=3DSHA1 >>>>>> DHE-RSA-AES128-SHA SSLv3 Kx=3DDH Au=3DRSA = Enc=3DAES(128) Mac=3DSHA1 >>>>>> DHE-DSS-AES128-SHA SSLv3 Kx=3DDH Au=3DDSS = Enc=3DAES(128) Mac=3DSHA1 >>>>>> AES128-SHA SSLv3 Kx=3DRSA Au=3DRSA = Enc=3DAES(128) Mac=3DSHA1 >>>>>> RC4-SHA SSLv3 Kx=3DRSA Au=3DRSA = Enc=3DRC4(128) Mac=3DSHA1 >>>>>> RC4-MD5 SSLv3 Kx=3DRSA Au=3DRSA = Enc=3DRC4(128) Mac=3DMD5 >>>>>> RC4-MD5 SSLv2 Kx=3DRSA Au=3DRSA = Enc=3DRC4(128) Mac=3DMD5 >>>>>> ...and you can experiment with TLS negotiation results via = something like: >>>>>> % openssl s_client -cipher 'AES256-SHA:AES128-SHA' -connect = www.google.com:443 >>>>>> [ ... ] >>>>>> New, TLSv1/SSLv3, Cipher is AES128-SHA >>>>>> Server public key is 2048 bit >>>>>> Secure Renegotiation IS supported >>>>>> Compression: NONE >>>>>> Expansion: NONE >>>>>> SSL-Session: >>>>>> Protocol : TLSv1 >>>>>> Cipher : AES128-SHA >>>>>> Session-ID: [ ... ] >>>>>> Sendmail normally performs crypto via STARTTLS negotiation rather = than via SMTPS; there's a CipherList option which can be defined via = sendmail.mc / sendmail.cf. You might need to recompile sendmail with = -D_FFR_TLS_1, which I think that novosial page mentions. >>>>> sendmail has _FFR_TLS_1 compiled in per th tests in the web page >>>>> mentioned above. The CipherList option doesn=E2=80=99t seem to = work. I can >>>>> connect and send mail with that in place using the EXPORT ciphers. >>>> Doug, >>>> I have this added to my /etc/mail/{HOSTNAME}.mc file. >>>> LOCAL_CONFIG >>>> O CipherList=3DALL:!aNULL:!eNULL:!LOW:!EXP:RC4+RSA:+HIGH:+MEDIUM >>>> Of course you can use other options, this has been there for a = while in mine, carried over from some time a few versions back. Probably = should get around to testing it to make sure it actually is still = working. It doesn't take long to add it in and run a quick test. >>> As I replied earlier, I have done that. I can still use: >>> openssl s_client -connect localhost:25 -starttls smtp -cipher EXPORT >>=20 >> Strange, it seems to be working on mine. >>=20 >> if I use the following, it connects: >> openssl s_client -connect 192.168.5.2:25 -starttls smtp >> CONNECTED(00000003) >> depth=3D1 C =3D US, ST =3D Arizona, L =3D Scottsdale, O =3D = "GoDaddy.com, Inc.", OU =3D http://certs.godaddy.com/repository/, CN =3D = Go Daddy Secure Certificate Authority - G2 >> [snip] >> New, TLSv1/SSLv3, Cipher is DHE-RSA-AES256-GCM-SHA384 >> Server public key is 4096 bit >> Secure Renegotiation IS supported >> Compression: NONE >> Expansion: NONE >> SSL-Session: >> Protocol : TLSv1.2 >> Cipher : DHE-RSA-AES256-GCM-SHA384 >> [snip] >>=20 >>=20 >> if I use the cipher option specify aNULL it fails: >>=20 >> openssl s_client -connect 192.168.5.2:25 -starttls smtp -cipher aNULL >> CONNECTED(00000003) >> 34379254472:error:14077410:SSL routines:SSL23_GET_SERVER_HELLO:sslv3 = alert handshake = failure:/jails/devel/ROOT/usr/src/secure/lib/libssl/../../../crypto/openss= l/ssl/s23_clnt.c:770: >> --- >> no peer certificate available >> --- >> No client certificate CA names sent >> --- >> SSL handshake has read 353 bytes and written 234 bytes >> --- >> New, (NONE), Cipher is (NONE) >> Secure Renegotiation IS NOT supported >> Compression: NONE >> Expansion: NONE >=20 > Interesting. That does seem to work for you. I will have to do some = more digging into the code. For some reason it doesn=E2=80=99t work for = me. Thanks for that assistance. =20 After more testing, I think you need to try: openssl s_client -connect 192.168.5.2:25 -starttls smtp -cipher EXP I suspect it will give: New, TLSv1/SSLv3, Cipher is EXP-DES-CBC-SHA That is the export cipher which is the problem.
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