Is there a way to get the session_id from the pyopenssl

[ratnapolepalli]

I see there is a method for set_session_id , but could not find get_session_id. I could not find the way to get the session Id. I also found set_session and get_session , but could not find the get_session_id.

Could anyone help on this , how to fix this issue

[vkosuri]

any luck?

[adiroiban]

I am also looking into this in order to implement the security check for an FTPS data connection.

For the OpenSSL API I found SSL_SESSION_get_id

I can see that pypopenssl access is done via from cryptography.hazmat.bindings.openssl.binding import Binding

And I can see that SSL_SESSION_get_id is defined in cryptography

https://github.com/reaperhulk/cryptography/blob/f69f27b1dd20ad2d24f48053a72545527e808104/src/_cffi_src/openssl/ssl.py#L303

I am not very familiar with cffi ... so I am not sure how this is exposed.

Hope it helps

[reaperhulk]

We no longer bind SSL_SESSION_get_id, but we can re-add the binding if it makes sense for pyOpenSSL. @adiroiban are you interested in doing PRs on both sides? It would look roughly like:

• Add binding back to cryptography
• Submit PR to pyOpenSSL. The CI will fail except on cryptographyMain, but that's okay
• Release new cryptography
• Update PR with new minimum version of cryptography, review, merge
• Release new pyOpenSSL with the feature.

[adiroiban]

I can give it a try. I tried to read the cryptography code for the binding ... but at a first look, I could't find the place where the binding is made... maybe this was moved to rust.

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I don't realy need the actual session ID value. I only want to make sure that 2 independent TCP connections have the same session ID :)

There is this function SSL.Connection.master_key()

I guess that if 2 connections have the same peer certificate and the same encryption key, they might also share the same session.

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But for the future, I think is best for FTPS applications to use the session_id() rather than handle the encryption key... and accidentlly leaking in some logs.

[adiroiban]

I have continue working on this.

On client-side for TLS 1.2 it looks like SSL.Connection.get_session() and SSL.Connection.set_session() are enought to implement client-side TLS session resumption.

Now, the actual session ID is still usefull on the client side to validate wheter the sessions was resumed for not.

The client can set a session ID, but the server can decide not to reuse it.

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For TLS 1.3 it looks like we also need SSL_CTX_sess_set_new_cb

From SSL_get1_session docs

Calling these functions on the client side in TLSv1.3 before the session has been established will still return an SSL_SESSION object but that object cannot be used for resuming the session.

For session resumption, there is also the SSL_SESSION_is_resumable

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I guess we should start by looking into the API required to implement session resumption for server-side and client-side on pyopenssl for TLS 1.2 and TLS 1.3

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For the client side with TLS 1.3, SSL.Connection.get_session() returns a resumable session, if I set the context to context.set_session_cache_mode(SSL.SESS_CACHE_OFF)

Setting the cache to SESS_CACHE_CLIENT returns a session that can only be used to resume one.

I will do more testing and more code and docs reading :)

[adiroiban]

It looks like SSL_SESSION_get_id was removed here (https://github.com/pyca/cryptography/pull/8340 ) and I think the removal was released in 40.0.0

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I think that the critical API that should be available in cryptography and pyOpenSSL is SSL_session_reused

I started a ticket here https://github.com/pyca/cryptography/issues/9969

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I still need to do more reading about SSL_SESSION_get_id and TLS 1.3 as in TLS 1.3 there are session tickets instead of session IDs.

[adiroiban]

Cryptography PR at https://github.com/pyca/cryptography/pull/9978

It doesn't add SSL_SESSION_get_id

It adds SSL_session_reused which can be used to check if the previously set session was reused.

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We can also have SSL_SESSION_get_id exposes, but I think that it would help to know the use case for this API.

When a session is resued, the client-side will have the same ID...but the server side has different ID, even when reused.

[vkosuri]

When a session is resued, the client-side will have the same ID...but the server side has different ID, even when reused.

I'm just curious to know, is this behaviour the same as earlier?

[adiroiban]

Hi

I'm just curious to know, is this behaviour the same as earlier?

This is only on TLS 1.3

You can try with pip install cryptography==39.0.2 as this verion has the missing API.

In my tests, on TLS 1.3 SSL_session_reused returns 1 (was reused) while SSL_SESSION_get_id were different... but maybe there was an error in my process.

I am trying to get SSL_session_reused as I think this is the API

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I have create a PR for SSL_session_reused here, but I'm not sure how to write the automated tests.

All ok for TLS 1.2 but for TLS 1.3 the automated tests are failing.

I did some manual tests with curl and it looked fine.

https://github.com/pyca/pyopenssl/pull/1276

If you have time, maybe you can give it a try.

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For which protocol do you need SSL_SESSION_get_id ?

For HTTPS you might not need it on TLS1.3 - https://timtaubert.de/blog/2017/02/the-future-of-session-resumption/

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I need this API to implement an FTPS server and client.