Re: disabling certain ciphers
Am 02.12.2014 um 06:44 schrieb Will Yardley: On Mon, Dec 01, 2014 at 09:27:48PM -0800, Darren Pilgrim wrote: On 12/1/2014 4:43 PM, Will Yardley wrote: Can you use both ssl_protocols *and* ssl_cipher_list in the same config (in a way that's sane)? Is there a way to exclude these ciphers, while still keeping my config easy to parse and avoiding duplicative or deprecated configs? Yes to both. If you need to support older clients: ssl_cipher_list = HIGH:!RC4:!MD5:!SRP:!PSK:!aNULL:@STRENGTH ssl_dh_parameters_length = 2048 ssl_parameters_regenerate = 0 ssl_protocols = !SSLv2 !SSLv3 TLSv1 TLSv1.1 TLSv1.2 But why does ssl_protocols behave differently depending on if $ssl_cipher_list is defined? Shouldn't !SSLv2 and !SSLv3 be sufficient? It seems that if ssl_cipher_list is defined, ssl_protocols = !SSLv2 !SSLv3 results in TLS1.2 being the only one active, but if it is defined, 1.0, 1.1, and 1.2 are all active? ssl_protocols = !SSLv2 !SSLv3 and you are fine, aynthing else is nonsense because when TLSv1.3 will be released you go to each and every server to add it to the config? likely not! signature.asc Description: OpenPGP digital signature
Re: disabling certain ciphers
On 12/2/2014 1:32 AM, Reindl Harald wrote: Am 02.12.2014 um 06:44 schrieb Will Yardley: On Mon, Dec 01, 2014 at 09:27:48PM -0800, Darren Pilgrim wrote: On 12/1/2014 4:43 PM, Will Yardley wrote: Can you use both ssl_protocols *and* ssl_cipher_list in the same config (in a way that's sane)? Is there a way to exclude these ciphers, while still keeping my config easy to parse and avoiding duplicative or deprecated configs? Yes to both. If you need to support older clients: ssl_cipher_list = HIGH:!RC4:!MD5:!SRP:!PSK:!aNULL:@STRENGTH ssl_dh_parameters_length = 2048 ssl_parameters_regenerate = 0 ssl_protocols = !SSLv2 !SSLv3 TLSv1 TLSv1.1 TLSv1.2 But why does ssl_protocols behave differently depending on if $ssl_cipher_list is defined? Shouldn't !SSLv2 and !SSLv3 be sufficient? It seems that if ssl_cipher_list is defined, ssl_protocols = !SSLv2 !SSLv3 results in TLS1.2 being the only one active, but if it is defined, 1.0, 1.1, and 1.2 are all active? ssl_protocols = !SSLv2 !SSLv3 and you are fine, aynthing else is nonsense because when TLSv1.3 will be released you go to each and every server to add it to the config? likely not! Configuration management. :) Also, no, you need to do more than just disable SSLv3. You need to disable several cipher groups allowed in TLSv1.0 and TLSv1.1, bump up the DH parameter size, and, if your client base allows it, only allow ciphers with forward secrecy.
Re: disabling certain ciphers
On 12/1/2014 9:44 PM, Will Yardley wrote: On Mon, Dec 01, 2014 at 09:27:48PM -0800, Darren Pilgrim wrote: On 12/1/2014 4:43 PM, Will Yardley wrote: Can you use both ssl_protocols *and* ssl_cipher_list in the same config (in a way that's sane)? Is there a way to exclude these ciphers, while still keeping my config easy to parse and avoiding duplicative or deprecated configs? Yes to both. If you need to support older clients: ssl_cipher_list = HIGH:!RC4:!MD5:!SRP:!PSK:!aNULL:@STRENGTH ssl_dh_parameters_length = 2048 ssl_parameters_regenerate = 0 ssl_protocols = !SSLv2 !SSLv3 TLSv1 TLSv1.1 TLSv1.2 But why does ssl_protocols behave differently depending on if $ssl_cipher_list is defined? Shouldn't !SSLv2 and !SSLv3 be sufficient? It seems that if ssl_cipher_list is defined, ssl_protocols = !SSLv2 !SSLv3 results in TLS1.2 being the only one active, but if it is defined, 1.0, 1.1, and 1.2 are all active? Where are you see this behaviour? What tool is reporting this?
Re: disabling certain ciphers
Am 02.12.2014 um 17:33 schrieb Darren Pilgrim: On 12/2/2014 1:32 AM, Reindl Harald wrote: ssl_cipher_list = HIGH:!RC4:!MD5:!SRP:!PSK:!aNULL:@STRENGTH ssl_dh_parameters_length = 2048 ssl_parameters_regenerate = 0 ssl_protocols = !SSLv2 !SSLv3 TLSv1 TLSv1.1 TLSv1.2 But why does ssl_protocols behave differently depending on if $ssl_cipher_list is defined? Shouldn't !SSLv2 and !SSLv3 be sufficient? It seems that if ssl_cipher_list is defined, ssl_protocols = !SSLv2 !SSLv3 results in TLS1.2 being the only one active, but if it is defined, 1.0, 1.1, and 1.2 are all active? ssl_protocols = !SSLv2 !SSLv3 and you are fine, aynthing else is nonsense because when TLSv1.3 will be released you go to each and every server to add it to the config? likely not! Configuration management. :) mis-management is the right word for disable future procotols Also, no, you need to do more than just disable SSLv3. You need to disable several cipher groups allowed in TLSv1.0 and TLSv1.1, bump up the DH parameter size, and, if your client base allows it, only allow ciphers with forward secrecy i *only* referred to ssl_protocols and not to ciphers that below are sane settings supporting older Outlooks only talking RC4/DES but prefer a specific order for other clients ssl_protocols = !SSLv2 !SSLv3 ssl_prefer_server_ciphers = yes ssl_options = no_compression ssl_cipher_list = ECDHE-RSA-AES128-GCM-SHA256:ECDHE-RSA-AES256-GCM-SHA384:DHE-RSA-AES128-GCM-SHA256:DHE-RSA-AES256-GCM-SHA384:ECDHE-RSA-AES128-SHA256:ECDHE-RSA-AES256-SHA384:ECDHE-RSA-AES128-SHA:ECDHE-RSA-AES256-SHA:DHE-RSA-AES128-SHA256:DHE-RSA-AES256-SHA256:DHE-RSA-AES128-SHA:DHE-RSA-AES256-SHA:AES128-GCM-SHA256:AES256-GCM-SHA384:AES128-SHA:AES256-SHA:DHE-RSA-CAMELLIA128-SHA:DHE-RSA-CAMELLIA256-SHA:CAMELLIA128-SHA:CAMELLIA256-SHA:ECDHE-RSA-DES-CBC3-SHA:DES-CBC3-SHA signature.asc Description: OpenPGP digital signature
Re: disabling certain ciphers
On 12/2/2014 8:38 AM, Reindl Harald wrote: Am 02.12.2014 um 17:33 schrieb Darren Pilgrim: On 12/2/2014 1:32 AM, Reindl Harald wrote: ssl_cipher_list = HIGH:!RC4:!MD5:!SRP:!PSK:!aNULL:@STRENGTH ssl_dh_parameters_length = 2048 ssl_parameters_regenerate = 0 ssl_protocols = !SSLv2 !SSLv3 TLSv1 TLSv1.1 TLSv1.2 But why does ssl_protocols behave differently depending on if $ssl_cipher_list is defined? Shouldn't !SSLv2 and !SSLv3 be sufficient? It seems that if ssl_cipher_list is defined, ssl_protocols = !SSLv2 !SSLv3 results in TLS1.2 being the only one active, but if it is defined, 1.0, 1.1, and 1.2 are all active? ssl_protocols = !SSLv2 !SSLv3 and you are fine, aynthing else is nonsense because when TLSv1.3 will be released you go to each and every server to add it to the config? likely not! Configuration management. :) mis-management is the right word for disable future procotols It wouldn't. As you've pointed out, you don't have to explicitly enable TLSv1.0+. That's because they're (now) enabled by default. There was a period of time when TLSv1.1 and TLSv1.2 weren't enabled by default. There are also some softwares that don't do the SSL setup correctly without explicit protocol lists. It's easier to be uniformly explicit everywhere. I'd rather be needlessly explicit than have a security failure due to incorrectly assuming an implicit behaviour. Also, no, you need to do more than just disable SSLv3. You need to disable several cipher groups allowed in TLSv1.0 and TLSv1.1, bump up the DH parameter size, and, if your client base allows it, only allow ciphers with forward secrecy i *only* referred to ssl_protocols and not to ciphers Sorry, that wasn't obvious to me. that below are sane settings supporting older Outlooks only talking RC4/DES but prefer a specific order for other clients ssl_protocols = !SSLv2 !SSLv3 ssl_prefer_server_ciphers = yes ssl_options = no_compression ssl_cipher_list = [really long cipherspec snipped] A student of Mozilla's security policies, I see. ;) You really only need TLSv1 3DES without PFS for Outlook on Windows XP/2003. Outlook on later Windows will do TLSv1 DHE-AES. Older Android devices will need TLSv1 AES128 without PFS. The minimum would therefore be: HIGH+kEECDH:HIGH+kEDH:-3DES:AES128-SHA:DES-CBC3-SHA:!aNULL:@STRENGTH Supporting other older ciphers may support ancient Android, IOS, MacOS and Thunderbird clients, but IME AES128-SHA and DES-CBC3-SHA are all you need for a realistic userbase of old software.
Re: disabling certain ciphers
On Tue, Dec 02, 2014 at 08:34:50AM -0800, Darren Pilgrim wrote: On 12/1/2014 9:44 PM, Will Yardley wrote: On Mon, Dec 01, 2014 at 09:27:48PM -0800, Darren Pilgrim wrote: On 12/1/2014 4:43 PM, Will Yardley wrote: Can you use both ssl_protocols *and* ssl_cipher_list in the same config (in a way that's sane)? Yes to both. If you need to support older clients: But why does ssl_protocols behave differently depending on if $ssl_cipher_list is defined? Shouldn't !SSLv2 and !SSLv3 be sufficient? It seems that if ssl_cipher_list is defined, ssl_protocols = !SSLv2 !SSLv3 results in TLS1.2 being the only one active, but if it is defined, 1.0, 1.1, and 1.2 are all active? Where are you see this behaviour? What tool is reporting this? I have mostly been testing with nmap, e.g., nmap -p 993 --script ssl-enum-ciphers [target] This then breaks down the ciphers by protocol suite. I'll test with your ssl_cipher_list example and see if it's reproducible. w
Re: disabling certain ciphers
On 12/2/2014 10:05 AM, Will Yardley wrote: I had some problems the first few times I restarted with ssl-params seeming to hang, but it finally works. That would have been dovecot generating the 4096-bit DH parameters. It can take a bit, but Dovecot is quite fast at it. If Dovecot supported it, you could use OpenSSL to generate tested-safe DH parameters and supply them by file the same way you do for Postfix, nginx, etc.
Re: disabling certain ciphers
On Tue, Dec 02, 2014 at 10:12:22AM -0800, Darren Pilgrim wrote: On 12/2/2014 10:05 AM, Will Yardley wrote: I had some problems the first few times I restarted with ssl-params seeming to hang, but it finally works. That would have been dovecot generating the 4096-bit DH parameters. It can take a bit, but Dovecot is quite fast at it. If Dovecot supported it, you could use OpenSSL to generate tested-safe DH parameters and supply them by file the same way you do for Postfix, nginx, etc. In this case, it was consuming a lot of CPU for 5+ minutes, and the .dat.tmp file hadn't been updated since the process started, so I'm not sure if something went wrong. strace on the ssl-params process itself (without following child procs, anyway) didn't seem to show anything happening. This happened for a couple of restarts. I enabled verbose ssl logging, restarted, and it seemed to work, then disabled verbose logging again, and it still works. w
Re: disabling certain ciphers
On 12/2/2014 10:26 AM, Will Yardley wrote: In this case, it was consuming a lot of CPU for 5+ minutes, and the .dat.tmp file hadn't been updated since the process started, so I'm not sure if something went wrong. Yes, large DH parameters take time to generate, hence turning off regeneration. 5 minutes is pretty reasonable.
disabling certain ciphers
Can you use both ssl_protocols *and* ssl_cipher_list in the same config (in a way that's sane)? ssl_protocols (= 2.1) and ssl_cipher_list co-exist, or are they mutually exclusive? I have a Dovecot 2.2.13 system, and I tried setting: I also tried things like ssl_cipher_list = HIGH or ssl_cipher_list = HIGH:!MEDIUM:!LOW however, doing this seems to make v3 still work unless I explicitly do !SSLv3 in ssl_cipher_list in addition to disabling it in $ssl_protocols. This is different from Apache, which has similar parameters, but where disabling the protocol takes precedence. If I just do: ssl_protocols = !SSLv2 !SSLv3 I still get some ciphers that show up as weak, e.g., | SSLv3: | ciphers: | TLS_DHE_RSA_WITH_3DES_EDE_CBC_SHA - strong | TLS_DHE_RSA_WITH_AES_128_CBC_SHA - strong | TLS_DHE_RSA_WITH_AES_256_CBC_SHA - strong | TLS_DHE_RSA_WITH_DES_CBC_SHA - weak [] | TLS_RSA_WITH_DES_CBC_SHA - weak Is there a way to exclude these ciphers, while still keeping my config easy to parse and avoiding duplicative or deprecated configs? The behavior is also pretty strange; if I have something like one of the following, with or without $ssl_protocols set to exclude SSLv2 and SSLv3: ssl_cipher_list = HIGH:!MEDIUM:!LOW:!SSLv3 ssl_cipher_list = ALL:!ADH:!LOW:!SSLv2:!SSLv3:!EXP:!aNULL:+HIGH:!MEDIUM TLS v1.0 and v1.1 get disabled as well. I also can't seem to explicitly enable TLS 1.0 or 1.1 in $ssl_cipher_list. w
Re: disabling certain ciphers
On 12/1/2014 4:43 PM, Will Yardley wrote: Can you use both ssl_protocols *and* ssl_cipher_list in the same config (in a way that's sane)? Is there a way to exclude these ciphers, while still keeping my config easy to parse and avoiding duplicative or deprecated configs? Yes to both. If you need to support older clients: ssl_cipher_list = HIGH:!RC4:!MD5:!SRP:!PSK:!aNULL:@STRENGTH ssl_dh_parameters_length = 2048 ssl_parameters_regenerate = 0 ssl_protocols = !SSLv2 !SSLv3 TLSv1 TLSv1.1 TLSv1.2 If your userbase is limited to current clients and OSes, you can take it a bit further: ssl_cipher_list = HIGH+kEECDH:HIGH+kEDH:!3DES:!aNULL:@STRENGTH ssl_dh_parameters_length = 4096 ssl_parameters_regenerate = 0 ssl_protocols = !SSLv2 !SSLv3 TLSv1 TLSv1.1 TLSv1.2 This drops 3DES support and makes forward secrecy mandatory.
Re: disabling certain ciphers
On Mon, Dec 01, 2014 at 09:27:48PM -0800, Darren Pilgrim wrote: On 12/1/2014 4:43 PM, Will Yardley wrote: Can you use both ssl_protocols *and* ssl_cipher_list in the same config (in a way that's sane)? Is there a way to exclude these ciphers, while still keeping my config easy to parse and avoiding duplicative or deprecated configs? Yes to both. If you need to support older clients: ssl_cipher_list = HIGH:!RC4:!MD5:!SRP:!PSK:!aNULL:@STRENGTH ssl_dh_parameters_length = 2048 ssl_parameters_regenerate = 0 ssl_protocols = !SSLv2 !SSLv3 TLSv1 TLSv1.1 TLSv1.2 But why does ssl_protocols behave differently depending on if $ssl_cipher_list is defined? Shouldn't !SSLv2 and !SSLv3 be sufficient? It seems that if ssl_cipher_list is defined, ssl_protocols = !SSLv2 !SSLv3 results in TLS1.2 being the only one active, but if it is defined, 1.0, 1.1, and 1.2 are all active? w
