ChaCha20 decryption #2727
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ChaCha20 decryption #2727
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Decryption is TLS 1.3 handshakes is very slow if the response is encrypted using ChaCha20 and the $OPENSSL enc command does not support ChaCha20. This commit mitigates that problem by using $OPENSSL2 for ChaCha20 decryption if such decryption is needed and $OPENSSL does not support it. This commit also changes testssl.sh to make use of $OPENSSL2 for AES-GCM decryption, when $OPENSSL2 supports it, but $OPENSSL does not. However, this change is not as important. Implementing AES-GCM in Bash using $OPENSSL for AES ECB operations isn't nearly as slow as fully implementing ChaCha20 in Bash.
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Excellent, thanks! |
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Looking a bit forward into the future, David: Do you happen to know when (version) the enc functions with those algorithms were implemented? |
It seems that
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drwetter
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Jun 11, 2025
In #2727 there were workarounds introduced which sped up processing decryption of ChaCha20 and and AES-GCM by using OPENSSL2 when it is supporting such functions. However when OPENSSL2 is called and OPENSSL_CONF still points to the autogenerated file which works for `~/bin/openssl.$(uname -s).$(uname -m)` the decryption `$plaintext` will be empty which later on caused a negative value, see #2780 . This fixes #2780 by prepending `OPENSSL_CONF=''` to each OPENSSL2 instance. Also it makes `chacha20()` and `gcm-decrypt()` more robust. It is now more readable now. At other places $OPENSSL2 were prepended by `OPENSSL_CONF=''` also if there weren't any obvious errors noticed. Also now all OPENSSL2 vars will appear in /tmp/testssl.XXXXXX/environment.txt when debugging. It was also noticed that the `find_socat()` function had room for improvements, it was not set in any case when `socat was in $PATH or supplied via env SOCAT.
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Describe your changes
Decryption of TLS 1.3 handshakes is very slow if the response is encrypted using ChaCha20 and the
$OPENSSL enccommand does not support ChaCha20. This commit mitigates that problem by using$OPENSSL2for ChaCha20 decryption if such decryption is needed and$OPENSSLdoes not support it.This PR also changes testssl.sh to make use of
$OPENSSL2for AES-GCM decryption, when$OPENSSL2supports it, but$OPENSSLdoes not. However, this change is not as important. Implementing AES-GCM in Bash using$OPENSSLfor AES ECB operations isn't nearly as slow as fully implementing ChaCha20 in Bash.What is your pull request about?
If it's a code change please check the boxes which are applicable
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