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Hello everyone,

I am having troubles to change the cipher suite on a custom https monitor. Our client has turned off TLS v1.0 on their servers but each time I change the cipher option from DEFAULT ie. to DEFAULT:!SSLv3:!TLSv1 (worked on serverssl profile) to limit it to TLS v1.1 and TLS v1.2 no SSL session is being established for the monitor (I'm checking it with ssldump on the LTM, we use v10.2.4). Actually it just receives TCP fin and TCP resets messages. As soon as I put DEFAULT back, without disabling any other versions, I immediately start to see SSL sessions building up (and denied by server) using TLS v1.0. The only thing I can tamper with are the hashing/encryption/authentication algorithms, like ie DEFAULT:!RC4:!AES. This works as expected. But disabling the whole version stops creating ssl sessions.

Is it somehow enforced/hard-coded? And can it be changed?

Thanks.

Hello everyone,

I am having troubles to change the cipher suite on a custom https monitor. Our client has turned off TLS v1.0 on their servers but each time I change the cipher option from DEFAULT ie. to DEFAULT:!SSLv3:!TLSv1 (worked on serverssl profile) to limit it to TLS v1.1 and TLS v1.2 no SSL session is being established for the monitor (I'm checking it with ssldump on the LTM, we use v10.2.4). Actually it just receives TCP fin and TCP resets messages. As soon as I put DEFAULT back, without disabling any other versions, I immediately start to see SSL sessions building up (and denied by server) using TLS v1.0. The only thing I can tamper with are the hashing/encryption/authentication algorithms, like ie DEFAULT:!RC4:!AES. This works as expected. But disabling the whole version stops creating ssl sessions.

Is it somehow enforced/hard-coded? And can it be changed?

Thanks.

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Hi Peter ,

https monitor uses openssl library and openssl flags sslv3 and tls1.0 same . So when you use DEFAULT:!SSLv3:!TLSv1 there are no ciphers left to negotiate .

have you tried

tmsh\nmodify ltm monitor https monitor_name cipherlist TLSv1 or someother version .

you can see openssl ciphers by using this command :

openssl -v DEFAULT or some other setting in cipherlist in monitor https

Hi SynACk,

Thanks for the reply.

I've tried to set it as TLSv1_2 directly, but no sessions were opened. But if the https monitor doesn't actually use the build-in ciphers, the native ones like server/client ssl profiles do (which I checked via \"tmm --serverciphers 'DEFAULT'\" and they do support TLSv1.2 ie), and uses openssl instead then that would make perfect sense. The build in version of openssl in this particular version we are running is 0.9.8e. TLSv1.2 is supported from version 1.0.1 I believe. Now, this is kind of disappointing, would really like to know why the native ones are not used instead. Or at least to have a option to choose them somehow.

Anyway, thanks for the help.

Hi Peter/Brad,

i also had a somewhat similar issue few days back , maybe you can tell if you faced same issue .

LTM has default cipherlist in https monitor . And team who manages backend servers disabled sslv2 ,sslv3 . After that LTM is marking pool member down .

when using curl command it reported wrong version used, handshake failure .

Any help will be appreciated . No changes done on LTM .

Thanks

Hi Peter ,

I ran ssl dump and it was something like this :

self ip ltm <->backend server sslv2 compatible client hello

Version 3.1

all the cipher suites \n.\n.\n.\n.

Backend server<->self ip TCP Fin

self ip<->backend sevrer TCP Fin

Thanks

Hi Peter,

It was like this :

1 1 0.0020 (0.0020) C>S SSLv2 compatible client hello

Version 3.1

cipher suites

cipher 1

cipher 2\n .\n .

1 0.0032 (0.0000) S>C TCP FIN

1 0.0041 (0.0009) C>S TCP FIN

Thanks

Hi Peter,

We checked and got a solution from F5 :

once the server negotiates from SSLv2 to TLS1, all subsequent connections will utilize the later protocol. Due to the fact that these pool members have already negotiated to TLSv1, some of the monitors are shown working to pool members with sslv2 disabled .

basically they told that LTM cannot perform negotiate .

They recommended to disable :

app-service none\ncert none\ncipherlist DEFAULT:+SHA:+3DES:+kEDH\ncompatibility enabled  <---try setting compatibility to disale  \n

On F5 documents compatibility Displays, when enabled, that the SSL options setting (in OpenSSL) is set to ALL. The default is Enabled.

Not able to understand it's purpose ?

Thanks

Hi Peter ,

is there any way to force bigd to use tlsv1 as starting cipher instead of using pseudo sslv2 client hello which is being just used for compatibility reasons.

Thanks

@SynAck Did the change suggested by F5 fix the issue?