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Don't allow read/write after fatal error
OpenSSL 1.0.2 (starting from version 1.0.2b) introduced an "error state" mechanism. The intent was that if a fatal error occurred during a handshake then OpenSSL would move into the error state and would immediately fail if you attempted to continue the handshake. This works as designed for the explicit handshake functions (SSL_do_handshake(), SSL_accept() and SSL_connect()), however due to a bug it does not work correctly if SSL_read() or SSL_write() is called directly. In that scenario, if the handshake fails then a fatal error will be returned in the initial function call. If SSL_read()/SSL_write() is subsequently called by the application for the same SSL object then it will succeed and the data is passed without being decrypted/encrypted directly from the SSL/TLS record layer. In order to exploit this issue an attacker would have to trick an application into behaving incorrectly by issuing an SSL_read()/SSL_write() after having already received a fatal error. Thanks to David Benjamin (Google) for reporting this issue and suggesting this fix. CVE-2017-3737 Reviewed-by: Rich Salz <firstname.lastname@example.org>
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