Thanks, Rüdiger. Maybe this sheds some light on EVP_cleanup(): https://github.com/google/keyczar/issues/135
Seems libssl install algorithms into libcrypto and does not clean up on termination which means EVP_cleanup sees data which is already gone. -Stefan > Am 03.08.2018 um 15:42 schrieb Ruediger Pluem <[email protected]>: > > > > On 08/03/2018 03:28 PM, Stefan Eissing wrote: >> (I am trying to understand this issue, since someone reported probs >> with mod_md/mod_ssl/some db drive init order related to openssl init.) >> >> The the move from cleanup() to pre_cleanup() fixed this issue. It means (as >> I read it) >> that something was happening in sub-pools cleanup()s that was out-of-order. >> >> Looking at apr_crypto_init(), it registers the cleanup at the "root" pool, >> does this give a clue? >> >> So we might have: >> >> - mod_ssl loading libssl, loading libcrypto >> cleanup at pool >> - ... >> - someone (indirectly) calling apr_crypto_init() >> cleanup at root pool >> >> root pool destroy: >> sub pool destroy >> -> mod_ssl cleanup called >> -> apr cleanup called > > We have > > 1. ap_init_rng in main.c causes apr_crypto_init called with ap_pglobal > 2. This causes apr__crypto_openssl_term to be registered as a cleanup with > ap_pglobal. > 3. mod_ssl is loaded via the pconf pool which is a child of ap_pglobal > 4. The loading of mod_ssl triggers the loading of libssl via the dynamic > linker. > 5. libssl is initialized in ssl_hook_pre_config via > SSL_load_error_strings(); > SSL_library_init(); > 6. The above seems to cause references to static data in libssl being saved > in data structures > managed by libcrypto. > 7. apr_pool_destroy(process->pool) in main.c:283 destroys the ap_pglobal > which in turn > a) first destroys pconf > b) which causes mod_ssl to be unloaded > c) which cause libssl to be unloaded > 8. The cleanups of ap_pglobal are now called, especially > apr__crypto_openssl_term which > a) calls EVP_cleanup() > b) which tries to access the data stored in 6., but is gone since 7c) > > Using a pre_cleanup moves 8. before 7. and thus removes the issue. > > Regards > > Rüdiger
