If an engine comes up explicitely, it must also come down explicitely
In apps/apps.c, one can set up an engine with setup_engine(). However, we freed the structural reference immediately, which means that for engines that don't already have a structural reference somewhere else (because it has registered at least one cipher or digest algorithm method, and therefore gets a functional reference through the ENGINE_set_default() call), we end up returning an invalid reference. Instead, the function release_engine() is added, and called at the end of the routines that call setup_engine(). Originally, the ENGINE API wasn't designed for this to happen, an engine had to register at least one algorithm method, and was especially expected to register the algorithms corresponding to the key types that could be stored and hidden in hardware. However, it turns out that some engines will not register those algorithms with the ENGINE_set_{algo}, ENGINE_set_cipher or ENGINE_set_digest functions, as they only want the methods to be used for keys, not as general crypto accelerator methods. That may cause ENGINE_set_default() to do nothing, and no functional reference is therefore made, leading to a premature deallocation of the engine and it thereby becoming unavailable when trying to fetch a key. Reviewed-by:Rich Salz <rsalz@openssl.org> (Merged from https://github.com/openssl/openssl/pull/1644)
Please register or sign in to comment