Fixes#7988. As described there, the steps involved are:
1. Update our tests so they fail due to this problem.
2. Update the keys used in the tests so they pass with the new changes.
For 1, see a [failing travis run](https://travis-ci.com/github/certbot/certbot/jobs/340710511) with the included change. And for the full output to confirm that this is what is failing, see a [run on debian 10](https://github.com/certbot/certbot/files/4692350/debian_run_log.txt).
This PR adds `rsa4096_key.pem` and `rsa4096_cert.pem`, updates the `TLS-ALPN` test to use those keys in place of the 1024-bit versions, and fixes the README in that `testdata` folder with correct instructions to generate these files.
* export PIP_NO_BINARY in pip install subshell in test_sdists.sh
* set environment variable on the line that installs most packages
* Generate 4096-bit rsa key and cert, and fix README instructions to do so.
* Update TLS_ALPN test to use 4096-bit key instead of 1024-bit key.
* Update changelog
* Older versions of Python have an error when both VIRTUAL_NO_DOWNLOAD and PIP_NO_BINARY are set, so only apply the latter at the install phase.
* Add enum34 constraint manually, since rebuild_dependencies.py seems to be broken.
* only delete key if it exists
* Check OpenSSL version before trying to set PIP_NO_BINARY
* Add comment explaining why we only set PIP_NO_BINARY at the install step
This PR is the first part of work described in #6724.
It reintroduces the tls-alpn-01 challenge in `acme` module, that was introduced by #5894 and reverted by #6100. The reason it was removed in the past is because some tests showed that with `1.0.2` branch of OpenSSL, the self-signed certificate containing the authorization key is sent to the requester even if the ALPN protocol `acme-tls/1` was not declared as supported by the requester during the TLS handshake.
However recent discussions lead to the conclusion that this behavior was not a security issue, because first it is coherent with the behavior with servers that do not support ALPN at all, and second it cannot make a tls-alpn-01 challenge be validated in this kind of corner case.
On top of the original modifications given by #5894, I merged the code to be up-to-date with our `master`, and fixed tests to match recent evolution about not displaying the `keyAuthorization` in the deserialized JSON form of an ACME challenge.
I also move the logic to verify if ALPN is available on the current system, and so that the tls-alpn-01 challenge can be used, to a dedicated static function `is_available` in `acme.challenge.TLSALPN01`. This function is used in the related tests to skip them, and will be used in the future from Certbot plugins to trigger or not the logic related to tls-alpn-01, depending on the OpenSSL version available to Python.
* Reimplement TLS-ALPN-01 challenge and standalone TLS-ALPN server from #5894.
* Setup a class method to check if tls-alpn-01 is supported.
* Add potential missing parameter in validation for tls-alpn
* Improve comments
* Make a class private
* Handle old versions of openssl that do not terminate the handshake when they should do.
* Add changelog
* Explicitly close the TLS connection by the book.
* Remove unused exception
* Fix lint
* Move acme tests to tests/ directory outside of acme module
* Fix call to messages_test in client_test
* Move test_util.py and testdata/ into tests/
* Update manifest to package tests
* Exclude pycache and .py[cod]
