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SSL_SESSION_FREE(3) Library Functions Manual SSL_SESSION_FREE(3)


SSL_SESSION_freefree an allocated SSL_SESSION structure


#include <openssl/ssl.h>


SSL_SESSION_free() decrements the reference count of session and removes the SSL_SESSION structure pointed to by session and frees up the allocated memory, if the reference count has reached 0. If session is a NULL pointer, no action occurs.
SSL_SESSION objects are allocated when a TLS/SSL handshake operation is successfully completed. Depending on the settings, see SSL_CTX_set_session_cache_mode(3), the SSL_SESSION objects are internally referenced by the SSL_CTX and linked into its session cache. SSL objects may be using the SSL_SESSION object; as a session may be reused, several SSL objects may be using one SSL_SESSION object at the same time. It is therefore crucial to keep the reference count (usage information) correct and not delete a SSL_SESSION object that is still used, as this may lead to program failures due to dangling pointers. These failures may also appear delayed, e.g., when an SSL_SESSION object is completely freed as the reference count incorrectly becomes 0, but it is still referenced in the internal session cache and the cache list is processed during a SSL_CTX_flush_sessions(3) operation.
SSL_SESSION_free() must only be called for SSL_SESSION objects, for which the reference count was explicitly incremented (e.g., by calling SSL_get1_session(3); see SSL_get_session(3)) or when the SSL_SESSION object was generated outside a TLS handshake operation, e.g., by using d2i_SSL_SESSION(3). It must not be called on other SSL_SESSION objects, as this would cause incorrect reference counts and therefore program failures.


d2i_SSL_SESSION(3), SSL_CTX_flush_sessions(3), SSL_CTX_set_session_cache_mode(3), SSL_get_session(3), SSL_SESSION_new(3)
December 6, 2016 OpenBSD-current