HP Open Source Security for OpenVMS Volume 2: HP SSL for OpenVMS > SSL Application Programming Interface (API)
SSL_get_ex_data_X509_STORE_CTX_idx() returns the index number under which the pointer to the SSL object is stored into the X509_STORE_CTX object.
Whenever a X509_STORE_CTX object is created for the verification of the peers certificate during a handshake, a pointer to the SSL object is stored into the X509_STORE_CTX object to identify the connection affected. To retrieve this pointer the X509_STORE_CTX_get_ex_data() function can be used with the correct index. This index is globally the same for all X509_STORE_CTX objects and can be retrieved using SSL_get_ex_data_X509_STORE_CTX_idx(). The index value is set when SSL_get_ex_data_X509_STORE_CTX_idx() is first called either by the application program directly or indirectly during other SSL setup functions or during the handshake.
The value depends on other index values defined for X509_STORE_CTX objects before the SSL index is created.
The index returned from SSL_get_ex_data_X509_STORE_CTX_idx() allows to access the SSL object for the connection to be accessed during the verify_callback() when checking the peers certificate. Please check the example in SSL_CTX_set_verify(3),