[3.10] gh-108310: Fix CVE-2023-40217: Check for & avoid the ssl pre-close flaw #108318
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…ose flaw Instances of `ssl.SSLSocket` were vulnerable to a bypass of the TLS handshake and included protections (like certificate verification) and treating sent unencrypted data as if it were post-handshake TLS encrypted data. The vulnerability is caused when a socket is connected, data is sent by the malicious peer and stored in a buffer, and then the malicious peer closes the socket within a small timing window before the other peers’ TLS handshake can begin. After this sequence of events the closed socket will not immediately attempt a TLS handshake due to not being connected but will also allow the buffered data to be read as if a successful TLS handshake had occurred. Co-Authored-By: Gregory P. Smith [Google LLC] <greg@krypto.org>
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Instances of
ssl.SSLSocketwere vulnerable to a bypass of the TLS handshake and included protections (like certificate verification) and treating sent unencrypted data as if it were post-handshake TLS encrypted data.The vulnerability is caused when a socket is connected, data is sent by the malicious peer and stored in a buffer, and then the malicious peer closes the socket within a small timing window before the other peers’ TLS handshake can begin. After this sequence of events the closed socket will not immediately attempt a TLS handshake due to not being connected but will also allow the buffered data to be read as if a successful TLS handshake had occurred.