Cryptography and SSL/TLS Toolkit



SSL_free - free an allocated SSL structure


#include <openssl/ssl.h>

void SSL_free(SSL *ssl);


SSL_free() decrements the reference count of ssl, and removes the SSL structure pointed to by ssl and frees up the allocated memory if the reference count has reached 0. If ssl is NULL nothing is done.


SSL_free() also calls the free()ing procedures for indirectly affected items, if applicable: the buffering BIO, the read and write BIOs, cipher lists specially created for this ssl, the SSL_SESSION. Do not explicitly free these indirectly freed up items before or after calling SSL_free(), as trying to free things twice may lead to program failure.

The ssl session has reference counts from two users: the SSL object, for which the reference count is removed by SSL_free() and the internal session cache. If the session is considered bad, because SSL_shutdown(3) was not called for the connection and SSL_set_shutdown(3) was not used to set the SSL_SENT_SHUTDOWN state, the session will also be removed from the session cache as required by RFC2246.

When used to free a QUIC stream SSL object, the respective sending and receiving parts of the stream are reset unless those parts have already been concluded normally:

  • If the stream has a sending part (in other words, if it is bidirectional or a locally-initiated unidirectional stream) and that part has not been concluded via a call to SSL_stream_conclude(3) or SSL_stream_reset(3) on the QUIC stream SSL object, a call to SSL_free() automatically resets the sending part of the stream as though SSL_stream_reset(3) were called with a QUIC application error code of 0.

  • If the stream has a receiving part (in other words, if it is bidirectional or a remotely-initiated unidirectional stream), and the peer has not yet concluded that part of the stream normally (such as via a call to SSL_stream_conclude(3) on its own end), a call to SSL_free() automatically requests the reset of the receiving part of the stream using a QUIC STOP_SENDING frame with a QUIC application error code of 0. Note that as per the QUIC protocol, this will automatically cause the peer to reset that part of the stream in turn (which is its sending part).

A QUIC stream SSL object maintains a reference to a QUIC connection SSL object internally, therefore a QUIC stream SSL object and its parent QUIC connection SSL object can be freed in either order.


SSL_free() does not provide diagnostic information.

SSL_new(3), SSL_clear(3), SSL_shutdown(3), SSL_set_shutdown(3), ssl(7)

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