Re: How to configure encryption ciphers and SSL/TLS protocols
On Mon, 9 Jun 2014 10:16:43 +0200, you wrote: On Mon, Jun 09, 2014 at 08:39:52AM +0100, John Cox wrote: Hi That's not correct no, I get plenty of TLS 1.0 trafic and it has been the case for many years To parrot this on all of my various instances OpenSMTPD and not I get tons of TLS 1.0 and SSLv3 traffic, I wish I didn't but it still happens. Heck every now and again I see SSLv2 attempts which for most of my instances get killed. I haven't seen one on my OpenSMTPD instance yet but its only time. But seriously for email any transport encryption is better than none and OpenSMTPD's default should be the best way to handle opportunistic TLS where you always try to use the highest protocol version supported with the best ciphers supported, and there shouldnt need to be a knob for it. Whilst I agree with what you are saying for general purpose mail servers, I can see applications where enforced encryption levels are worth having. I can see that some company gateways, where they know all of the other endpoints, might wish to enforce appropriate encryption as everybody who should be talking to that MTA should be capable of it and anything else is therefore spam or hacking. This is particularly plausible on any link where TLS or SSL is already mandatory. please define enforced encryption levels ? Tricky - I don't have a specific use case in mind, but I worked on building a military email system (X.400 based - it was that long ago, though they may still use it for all I know) and they were pretty keen on nailing down exactly what was expected on each link. pretty much anyone tweaking ssl_ciphers will actually downgrade security or/and break interop with other servers. some people may know how to tie things further for their specific use-cases but the minute we add a knob other people will start using it and shoot themselves in the foot. Sadly that is the case with pretty much all security, but the lack of an ability to check/filter based on what security level has been negotiated means that those people who _do_ know what they are doing can't. I'm still annoyed by the general (not smtpd particularly) impossibility of having usefully functioning CRLs, which are pretty much a requirement of any PK system but have been generally ignored to date. At the time being we're looking to is to have the bul0k of users safe by default and we're looking for more: https://twitter.com/Mayeu/status/474109854651785216 the magic of OpenSMTPD, you do no TLS configuration and you're graded A by default 3 (test here: starttls.info) I do not disagree Im not saying that this will hold true forever but at this point in time I would prefer that we dont have ssl_ciphers and that any improvement we do is made to the default until we exhausted all possibilities to do so. Fair enough - I just felt it was worth adding another point of view to the discussion. Thanks JC -- You received this mail because you are subscribed to misc@opensmtpd.org To unsubscribe, send a mail to: misc+unsubscr...@opensmtpd.org
Re: How to configure encryption ciphers and SSL/TLS protocols
Hi That's not correct no, I get plenty of TLS 1.0 trafic and it has been the case for many years To parrot this on all of my various instances OpenSMTPD and not I get tons of TLS 1.0 and SSLv3 traffic, I wish I didn't but it still happens. Heck every now and again I see SSLv2 attempts which for most of my instances get killed. I haven't seen one on my OpenSMTPD instance yet but its only time. But seriously for email any transport encryption is better than none and OpenSMTPD's default should be the best way to handle opportunistic TLS where you always try to use the highest protocol version supported with the best ciphers supported, and there shouldnt need to be a knob for it. Whilst I agree with what you are saying for general purpose mail servers, I can see applications where enforced encryption levels are worth having. I can see that some company gateways, where they know all of the other endpoints, might wish to enforce appropriate encryption as everybody who should be talking to that MTA should be capable of it and anything else is therefore spam or hacking. This is particularly plausible on any link where TLS or SSL is already mandatory. Regards JC -- You received this mail because you are subscribed to misc@opensmtpd.org To unsubscribe, send a mail to: misc+unsubscr...@opensmtpd.org
Re: How to configure encryption ciphers and SSL/TLS protocols
On Mon, Jun 09, 2014 at 08:39:52AM +0100, John Cox wrote: Hi That's not correct no, I get plenty of TLS 1.0 trafic and it has been the case for many years To parrot this on all of my various instances OpenSMTPD and not I get tons of TLS 1.0 and SSLv3 traffic, I wish I didn't but it still happens. Heck every now and again I see SSLv2 attempts which for most of my instances get killed. I haven't seen one on my OpenSMTPD instance yet but its only time. But seriously for email any transport encryption is better than none and OpenSMTPD's default should be the best way to handle opportunistic TLS where you always try to use the highest protocol version supported with the best ciphers supported, and there shouldnt need to be a knob for it. Whilst I agree with what you are saying for general purpose mail servers, I can see applications where enforced encryption levels are worth having. I can see that some company gateways, where they know all of the other endpoints, might wish to enforce appropriate encryption as everybody who should be talking to that MTA should be capable of it and anything else is therefore spam or hacking. This is particularly plausible on any link where TLS or SSL is already mandatory. please define enforced encryption levels ? pretty much anyone tweaking ssl_ciphers will actually downgrade security or/and break interop with other servers. some people may know how to tie things further for their specific use-cases but the minute we add a knob other people will start using it and shoot themselves in the foot. At the time being we're looking to is to have the bul0k of users safe by default and we're looking for more: https://twitter.com/Mayeu/status/474109854651785216 the magic of OpenSMTPD, you do no TLS configuration and you're graded A by default 3 (test here: starttls.info) Im not saying that this will hold true forever but at this point in time I would prefer that we dont have ssl_ciphers and that any improvement we do is made to the default until we exhausted all possibilities to do so. -- Gilles Chehade https://www.poolp.org @poolpOrg -- You received this mail because you are subscribed to misc@opensmtpd.org To unsubscribe, send a mail to: misc+unsubscr...@opensmtpd.org
Re: How to configure encryption ciphers and SSL/TLS protocols
I think at build time you can fine-tune which ciphers you want by editing ssl.h -- in particular the SSL_CIPHERS define. --Adam On Mon, 9 Jun 2014, Gilles Chehade wrote: On Mon, Jun 09, 2014 at 08:39:52AM +0100, John Cox wrote: Hi That's not correct no, I get plenty of TLS 1.0 trafic and it has been the case for many years To parrot this on all of my various instances OpenSMTPD and not I get tons of TLS 1.0 and SSLv3 traffic, I wish I didn't but it still happens. Heck every now and again I see SSLv2 attempts which for most of my instances get killed. I haven't seen one on my OpenSMTPD instance yet but its only time. But seriously for email any transport encryption is better than none and OpenSMTPD's default should be the best way to handle opportunistic TLS where you always try to use the highest protocol version supported with the best ciphers supported, and there shouldnt need to be a knob for it. Whilst I agree with what you are saying for general purpose mail servers, I can see applications where enforced encryption levels are worth having. I can see that some company gateways, where they know all of the other endpoints, might wish to enforce appropriate encryption as everybody who should be talking to that MTA should be capable of it and anything else is therefore spam or hacking. This is particularly plausible on any link where TLS or SSL is already mandatory. please define enforced encryption levels ? pretty much anyone tweaking ssl_ciphers will actually downgrade security or/and break interop with other servers. some people may know how to tie things further for their specific use-cases but the minute we add a knob other people will start using it and shoot themselves in the foot. At the time being we're looking to is to have the bul0k of users safe by default and we're looking for more: https://twitter.com/Mayeu/status/474109854651785216 the magic of OpenSMTPD, you do no TLS configuration and you're graded A by default 3 (test here: starttls.info) Im not saying that this will hold true forever but at this point in time I would prefer that we dont have ssl_ciphers and that any improvement we do is made to the default until we exhausted all possibilities to do so. -- Gilles Chehade https://www.poolp.org @poolpOrg -- You received this mail because you are subscribed to misc@opensmtpd.org To unsubscribe, send a mail to: misc+unsubscr...@opensmtpd.org -- You received this mail because you are subscribed to misc@opensmtpd.org To unsubscribe, send a mail to: misc+unsubscr...@opensmtpd.org
Re: How to configure encryption ciphers and SSL/TLS protocols
On Sat, Jun 07, 2014 at 03:40:12PM -0700, Clint Pachl wrote: Is there a way to configure smtpd to only use specified ciphers or limit it to TLSv1.[12]? I'm looking for something similar to Dovecot's `ssl_cipher_list` or Nginx's `ssl_ciphers` or `ssl_protocols` configuration directives. no, we don't want to make this tunable. the rationale is that we want to propose the best encryption by default. if there is a better choice, it should be proposed and discussed openly as it should become the new default. yes, it's tempting to provide ssl_ciphers but unless there's a very good reason to do it, we won't introduce this new knob. The reason I ask is because I'm very close to failing my PCI compliance because of smptd. They score each compliance test from 0 to 9. If any single score is 4.0 or higher, I fail PCI compliance. OpenSMTPD 5.4.2 is currently receiving a risk score of 3.9. I have a feeling that in the not too distant future this particular test will fail. My PCI-DSS vendor, Security Metrics, states that smtpd is vulnerable to information disclosure because of the initialization vector implementations in SSLv3 and TLSv1.0. Thier stated resolution is: Configure SSL/TLS servers to only use TLS 1.1 or TLS 1.2 if supported. Configure SSL/TLS servers to only support cipher suites that do not use block ciphers. This can certainly be improved without adding ssl_ciphers knob I'm not a mail expert, but my feeling is that secured email hasn't been widespread until recent years. If any MTAs support encryption, they are probably using the latest protocols and ciphers. That's not correct no, I get plenty of TLS 1.0 trafic and it has been the case for many years -- Gilles Chehade https://www.poolp.org @poolpOrg -- You received this mail because you are subscribed to misc@opensmtpd.org To unsubscribe, send a mail to: misc+unsubscr...@opensmtpd.org
