error strings - the destroy handler functions unload the error strings so
any pending error state referring to them will not attempt to reference
them after the ENGINE has been destroyed.

being enabled or disabled (respectively) for operation. Additionally, each
ENGINE has a constructor function where it can do more 'structural' level
intialisations such as loading error strings, creating "ex_data" indices,
etc. This change introduces a handler function that gives an ENGINE a
corresponding opportunity to cleanup when the ENGINE is being destroyed. It
also adds the "get/set" API functions that control this "destroy" handler
function in an ENGINE.

declaration and implementation had not. So a recent update recreated the
original definition in libeay.num ... this corrects it and changes the "dh"
code to the "up_ref" variant.

defined.

(Preprocessor symbols such as _POSIX_C_SOURCE or _XOPEN_SOURCE are
supposed to disable anything not allowed by the respective
specification; I'm not sure why 'strdup' would be considered
an outlaw though.)

measure (including info and instructions on "dynamic" ENGINEs).

Submitted by: "Brian Havard" <brianh@kheldar.apana.org.au>

locking callbacks to pass to the loaded library (in addition to the
existing mem, ex_data, and err callbacks). Also change the default
implementation of the "bind_engine" function to apply those callbacks, ie.
the IMPLEMENT_DYNAMIC_BIND_FN macro.

recent changes. Also, do the same change to the DSO_up() function.

always load its strings because they might have been unloaded
since the 'init' flag was deleted.

But build_SYS_str_reasons() can use an 'init' flag.

(here: X509_STORE_CTX_init())

declare their own error strings so that they can be more easily compiled as
external shared-libraries if desired. Also, each implementation has been
given canonical "dynamic" support at the base of each file and is only
built if the ENGINE_DYNAMIC_SUPPORT symbol is defined.

Also, use "void" prototypes rather than empty prototypes in engine_int.h.

This does not yet;
  (i) remove error strings when unloading,
 (ii) remove the redundant ENGINE_R_*** codes (though ENGINE_F_*** codes
      have gone), or
(iii) provide any instructions on how to build shared-library ENGINEs or
      use them.

All are on their way.

implementations to be loaded from self-contained shared-libraries. It also
provides (in engine.h) definitions and macros to help implement a
self-contained ENGINE. Version control is handled in a way whereby the
loader or loadee can veto the load depending on any objections it has with
each other's declared interface level. The way this is currently
implemented assumes a veto will only take place when one side notices the
other's interface level is too *old*. If the other side is newer, it should
be assumed the newer version knows better whether to veto the load or not.
Version checking (like other "dynamic" settings) can be controlled using
the "dynamic" ENGINE's control commands. Also, the semantics for the
loading allow a shared-library ENGINE implementation to handle differing
interface levels on the fly (eg. loading secondary shared-libraries
depending on the versions required).

Code will be added soon to the existing ENGINEs to illustrate how they can
be built as external libraries rather than building statically into
libcrypto.

NB: Applications wanting to support "dynamic"-loadable ENGINEs will need to
add support for ENGINE "control commands". See apps/engine.c for an example
of this, and use "apps/openssl engine -vvvv" to test or experiment.

"ERR_load_strings" function.

      [DR]SA_up  =>  [DR]SA_up_ref

(by using new BN_pseudo_rand_range function)

is a bad idea if OPENSSL_OPENBSD_DEV_CRYPTO is not defined

Henson). Also, reverse a previous change that used an implicit function
pointer cast rather than an explicit data pointer cast in the STACK cleanup
code.

See the commit log message for that for more information.

NB: X509_STORE_CTX's use of "ex_data" support was actually misimplemented
(initialisation by "memset" won't/can't/doesn't work). This fixes that but
requires that X509_STORE_CTX_init() be able to handle errors - so its
prototype has been changed to return 'int' rather than 'void'. All uses of
that function throughout the source code have been tracked down and
adjusted.

Currently, this change merely addresses where ex_data indexes are stored
and managed, and thus fixes the thread-safety issues that existed at that
level. "Class" code (eg. RSA, DSA, etc) no longer store their own STACKS
and per-class index counters - all such data is stored inside ex_data.c. So
rather than passing both STACK+counter to index-management ex_data
functions, a 'class_index' is instead passed to indicate the class (eg.
CRYPTO_EX_INDEX_RSA). New classes can be dynamically registered on-the-fly
and this is also thread-safe inside ex_data.c (though whether the caller
manages the return value in a thread-safe way is not addressed).

This does not change the "get/set" functions on individual "ex_data"
structures, and so thread-safety at that level isn't (yet) assured.
Likewise, the method of getting and storing per-class indexes has not
changed, so locking may still be required at the "caller" end but is
nonetheless thread-safe inside "ex_data"'s internal implementation.
Typically this occurs when code implements a new method of some kind and
stores its own per-class index in a global variable without locking the
setting and usage of that variable. If the code in question is likely to be
used in multiple threads, locking the setting and use of that index is
still up to the code in question. Possible fixes to this are being
sketched, but definitely require more major changes to the API itself than
this change undertakes.

The underlying implementation in ex_data.c has also been modularised so
that alternative "ex_data" implementations (that control all access to
state) can be plugged in. Eg. a loaded module can have its implementation
set to that of the application loaded it - the result being that
thread-safety and consistency of "ex_data" classes and indexes can be
maintained in the same place rather than the loaded module using its own
copy of ex_data support code and state.

Due to the centralisation of "state" with this change, cleanup of all
"ex_data" state can now be performed properly. Previously all allocation of
ex_data state was guaranteed to leak - and MemCheck_off() had been used to
avoid it flagging up the memory debugging. A new function has been added to
perfrom all this cleanup, CRYPTO_cleanup_all_ex_data(). The "openssl"
command(s) have been changed to use this cleanup, as have the relevant test
programs. External application code may want to do so too - failure to
cleanup will not induce more memory leaking than was the case before, but
the memory debugging is not tricked into hiding it any more so it may
"appear" where it previously did not.

Submitted by: "Brian Havard" <brianh@kheldar.apana.org.au>