/usr/include/asio/ssl/ is in libasio-dev 1:1.10.6-3.
This file is owned by root:root, with mode 0o755.
..
/usr/include/asio/ssl/basic_context.hpp
/usr/include/asio/ssl/context.hpp
/usr/include/asio/ssl/context_base.hpp
/usr/include/asio/ssl/context_service.hpp
/usr/include/asio/ssl/detail/
/usr/include/asio/ssl/detail/buffered_handshake_op.hpp
/usr/include/asio/ssl/detail/engine.hpp
/usr/include/asio/ssl/detail/handshake_op.hpp
/usr/include/asio/ssl/detail/impl/
/usr/include/asio/ssl/detail/impl/engine.ipp
/usr/include/asio/ssl/detail/impl/openssl_init.ipp
/usr/include/asio/ssl/detail/io.hpp
/usr/include/asio/ssl/detail/openssl_init.hpp
/usr/include/asio/ssl/detail/openssl_types.hpp
/usr/include/asio/ssl/detail/password_callback.hpp
/usr/include/asio/ssl/detail/read_op.hpp
/usr/include/asio/ssl/detail/shutdown_op.hpp
/usr/include/asio/ssl/detail/stream_core.hpp
/usr/include/asio/ssl/detail/verify_callback.hpp
/usr/include/asio/ssl/detail/write_op.hpp
/usr/include/asio/ssl/error.hpp
/usr/include/asio/ssl/impl/
/usr/include/asio/ssl/impl/context.hpp
/usr/include/asio/ssl/impl/context.ipp
/usr/include/asio/ssl/impl/error.ipp
/usr/include/asio/ssl/impl/rfc2818_verification.ipp
/usr/include/asio/ssl/impl/src.hpp
/usr/include/asio/ssl/old/
/usr/include/asio/ssl/old/basic_context.hpp
/usr/include/asio/ssl/old/context_service.hpp
/usr/include/asio/ssl/old/detail/
/usr/include/asio/ssl/old/detail/openssl_context_service.hpp
/usr/include/asio/ssl/old/detail/openssl_operation.hpp
/usr/include/asio/ssl/old/detail/openssl_stream_service.hpp
/usr/include/asio/ssl/old/stream.hpp
/usr/include/asio/ssl/old/stream_service.hpp
/usr/include/asio/ssl/rfc2818_verification.hpp
/usr/include/asio/ssl/stream.hpp
/usr/include/asio/ssl/stream_base.hpp
/usr/include/asio/ssl/stream_service.hpp
/usr/include/asio/ssl/verify_context.hpp
/usr/include/asio/ssl/verify_mode.hpp