James E. King, III created THRIFT-3061:
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Summary: C++ TSSLSocket shutdown delay/vulnerability
Key: THRIFT-3061
URL: https://issues.apache.org/jira/browse/THRIFT-3061
Project: Thrift
Issue Type: Bug
Components: C++ - Library
Affects Versions: 0.9.2, 0.9.1, 0.9, 0.8
Reporter: James E. King, III
In the C++ implementation of TSSLSocket, during close() the following code
sequence is found:
{noformat}
void TSSLSocket::close() {
if (ssl_ != NULL) {
int rc = SSL_shutdown(ssl_);
if (rc == 0) {
rc = SSL_shutdown(ssl_);
}
{noformat}
According to the OpenSSL documentation, while it is "nice" to attempt to
shutdown SSL in this way, it is not required when the code is performing a
unilateral shutdown (meaning the underlying connection will be closed). It is
only necessary to call SSL_Shutdown twice like this if the socket (and
configured SSL therein) is going to be reused.
It is possible to have a misbehaving client that does not handle this part of
the shutdown process properly and fail to reply, and also fail to close. The
most likely embodiment would be a program designed specifically to fail to
reply to the "close notify" and hold the socket open in order to produce a
denial-of-service attack. Another possibility is a poorly written client.
Given the OpenSSL documentation states that calling SSL_Shutdown once is
sufficient when the socket is going to be closed, I recommend that we remove
the second SSL_Shutdown call and prevent something that can block the close()
call. We have seen this happen, and it interacts with THRIFT-2441.
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