- ENGINE
- ======
+ENGINES
+=======
With OpenSSL 0.9.6, a new component was added to support alternative
cryptography implementations, most commonly for interfacing with external
There are currently built-in ENGINE implementations for the following
crypto devices:
- o Microsoft CryptoAPI
- o VIA Padlock
- o nCipher CHIL
+ * Microsoft CryptoAPI
+ * VIA Padlock
+ * nCipher CHIL
In addition, dynamic binding to external ENGINE implementations is now
provided by a special ENGINE called "dynamic". See the "DYNAMIC ENGINE"
At this stage, a number of things are still needed and are being worked on:
- 1 Integration of EVP support.
- 2 Configuration support.
- 3 Documentation!
+ 1. Integration of EVP support.
+ 2. Configuration support.
+ 3. Documentation!
-1 With respect to EVP, this relates to support for ciphers and digests in
+ Integration of EVP support
+ --------------------------
+
+ With respect to EVP, this relates to support for ciphers and digests in
the ENGINE model so that alternative implementations of existing
algorithms/modes (or previously unimplemented ones) can be provided by
ENGINE implementations.
-2 Configuration support currently exists in the ENGINE API itself, in the
+ Configuration support
+ ---------------------
+
+ Configuration support currently exists in the ENGINE API itself, in the
form of "control commands". These allow an application to expose to the
user/admin the set of commands and parameter types a given ENGINE
implementation supports, and for an application to directly feed string
Presently however, applications must use the ENGINE API itself to provide
such functionality. To see first hand the types of commands available
with the various compiled-in ENGINEs (see further down for dynamic
- ENGINEs), use the "engine" openssl utility with full verbosity, ie;
+ ENGINEs), use the "engine" openssl utility with full verbosity, i.e.:
+
openssl engine -vvvv
-3 Documentation? Volunteers welcome! The source code is reasonably well
+ Documentation
+ -------------
+
+ Documentation? Volunteers welcome! The source code is reasonably well
self-documenting, but some summaries and usage instructions are needed -
moreover, they are needed in the same POD format the existing OpenSSL
documentation is provided in. Any complete or incomplete contributions
ENGINE API itself (ie. not necessarily specific to a particular ENGINE
implementation) then you should mail complete details to the relevant
OpenSSL mailing list. For a definition of "complete details", refer to
- the OpenSSL "README" file. As for which list to send it to;
+ the OpenSSL "README" file. As for which list to send it to:
- openssl-users: if you are *using* the ENGINE abstraction, either in an
- pre-compiled application or in your own application code.
+ * openssl-users: if you are *using* the ENGINE abstraction, either in an
+ pre-compiled application or in your own application code.
- openssl-dev: if you are discussing problems with OpenSSL source code.
+ * openssl-dev: if you are discussing problems with OpenSSL source code.
USAGE
=====
How does "dynamic" work?
------------------------
- The dynamic ENGINE has a special flag in its implementation such that
- every time application code asks for the 'dynamic' ENGINE, it in fact
- gets its own copy of it. As such, multi-threaded code (or code that
- multiplexes multiple uses of 'dynamic' in a single application in any
- way at all) does not get confused by 'dynamic' being used to do many
- independent things. Other ENGINEs typically don't do this so there is
- only ever 1 ENGINE structure of its type (and reference counts are used
- to keep order). The dynamic ENGINE itself provides absolutely no
- cryptographic functionality, and any attempt to "initialise" the ENGINE
- automatically fails. All it does provide are a few "control commands"
- that can be used to control how it will load an external ENGINE
- implementation from a shared-library. To see these control commands,
- use the command-line;
-
- openssl engine -vvvv dynamic
-
- The "SO_PATH" control command should be used to identify the
- shared-library that contains the ENGINE implementation, and "NO_VCHECK"
- might possibly be useful if there is a minor version conflict and you
- (or a vendor helpdesk) is convinced you can safely ignore it.
- "ID" is probably only needed if a shared-library implements
- multiple ENGINEs, but if you know the engine id you expect to be using,
- it doesn't hurt to specify it (and this provides a sanity check if
- nothing else). "LIST_ADD" is only required if you actually wish the
- loaded ENGINE to be discoverable by application code later on using the
- ENGINE's "id". For most applications, this isn't necessary - but some
- application authors may have nifty reasons for using it. The "LOAD"
- command is the only one that takes no parameters and is the command
- that uses the settings from any previous commands to actually *load*
- the shared-library ENGINE implementation. If this command succeeds, the
- (copy of the) 'dynamic' ENGINE will magically morph into the ENGINE
- that has been loaded from the shared-library. As such, any control
- commands supported by the loaded ENGINE could then be executed as per
- normal. Eg. if ENGINE "foo" is implemented in the shared-library
- "libfoo.so" and it supports some special control command "CMD_FOO", the
- following code would load and use it (NB: obviously this code has no
- error checking);
-
- ENGINE *e = ENGINE_by_id("dynamic");
- ENGINE_ctrl_cmd_string(e, "SO_PATH", "/lib/libfoo.so", 0);
- ENGINE_ctrl_cmd_string(e, "ID", "foo", 0);
- ENGINE_ctrl_cmd_string(e, "LOAD", NULL, 0);
- ENGINE_ctrl_cmd_string(e, "CMD_FOO", "some input data", 0);
-
- For testing, the "openssl engine" utility can be useful for this sort
- of thing. For example the above code excerpt would achieve much the
- same result as;
-
- openssl engine dynamic \
- -pre SO_PATH:/lib/libfoo.so \
- -pre ID:foo \
- -pre LOAD \
- -pre "CMD_FOO:some input data"
-
- Or to simply see the list of commands supported by the "foo" ENGINE;
-
- openssl engine -vvvv dynamic \
- -pre SO_PATH:/lib/libfoo.so \
- -pre ID:foo \
- -pre LOAD
-
- Applications that support the ENGINE API and more specifically, the
- "control commands" mechanism, will provide some way for you to pass
- such commands through to ENGINEs. As such, you would select "dynamic"
- as the ENGINE to use, and the parameters/commands you pass would
- control the *actual* ENGINE used. Each command is actually a name-value
- pair and the value can sometimes be omitted (eg. the "LOAD" command).
- Whilst the syntax demonstrated in "openssl engine" uses a colon to
- separate the command name from the value, applications may provide
- their own syntax for making that separation (eg. a win32 registry
- key-value pair may be used by some applications). The reason for the
- "-pre" syntax in the "openssl engine" utility is that some commands
- might be issued to an ENGINE *after* it has been initialised for use.
- Eg. if an ENGINE implementation requires a smart-card to be inserted
- during initialisation (or a PIN to be typed, or whatever), there may be
- a control command you can issue afterwards to "forget" the smart-card
- so that additional initialisation is no longer possible. In
- applications such as web-servers, where potentially volatile code may
- run on the same host system, this may provide some arguable security
- value. In such a case, the command would be passed to the ENGINE after
- it has been initialised for use, and so the "-post" switch would be
- used instead. Applications may provide a different syntax for
- supporting this distinction, and some may simply not provide it at all
- ("-pre" is almost always what you're after, in reality).
+
+ The dynamic ENGINE has a special flag in its implementation such that
+ every time application code asks for the 'dynamic' ENGINE, it in fact
+ gets its own copy of it. As such, multi-threaded code (or code that
+ multiplexes multiple uses of 'dynamic' in a single application in any
+ way at all) does not get confused by 'dynamic' being used to do many
+ independent things. Other ENGINEs typically don't do this so there is
+ only ever 1 ENGINE structure of its type (and reference counts are used
+ to keep order). The dynamic ENGINE itself provides absolutely no
+ cryptographic functionality, and any attempt to "initialise" the ENGINE
+ automatically fails. All it does provide are a few "control commands"
+ that can be used to control how it will load an external ENGINE
+ implementation from a shared-library. To see these control commands,
+ use the command-line;
+
+ openssl engine -vvvv dynamic
+
+ The "SO_PATH" control command should be used to identify the
+ shared-library that contains the ENGINE implementation, and "NO_VCHECK"
+ might possibly be useful if there is a minor version conflict and you
+ (or a vendor helpdesk) is convinced you can safely ignore it.
+ "ID" is probably only needed if a shared-library implements
+ multiple ENGINEs, but if you know the engine id you expect to be using,
+ it doesn't hurt to specify it (and this provides a sanity check if
+ nothing else). "LIST_ADD" is only required if you actually wish the
+ loaded ENGINE to be discoverable by application code later on using the
+ ENGINE's "id". For most applications, this isn't necessary - but some
+ application authors may have nifty reasons for using it. The "LOAD"
+ command is the only one that takes no parameters and is the command
+ that uses the settings from any previous commands to actually *load*
+ the shared-library ENGINE implementation. If this command succeeds, the
+ (copy of the) 'dynamic' ENGINE will magically morph into the ENGINE
+ that has been loaded from the shared-library. As such, any control
+ commands supported by the loaded ENGINE could then be executed as per
+ normal. Eg. if ENGINE "foo" is implemented in the shared-library
+ "libfoo.so" and it supports some special control command "CMD_FOO", the
+ following code would load and use it (NB: obviously this code has no
+ error checking);
+
+ ENGINE *e = ENGINE_by_id("dynamic");
+ ENGINE_ctrl_cmd_string(e, "SO_PATH", "/lib/libfoo.so", 0);
+ ENGINE_ctrl_cmd_string(e, "ID", "foo", 0);
+ ENGINE_ctrl_cmd_string(e, "LOAD", NULL, 0);
+ ENGINE_ctrl_cmd_string(e, "CMD_FOO", "some input data", 0);
+
+ For testing, the "openssl engine" utility can be useful for this sort
+ of thing. For example the above code excerpt would achieve much the
+ same result as;
+
+ openssl engine dynamic \
+ -pre SO_PATH:/lib/libfoo.so \
+ -pre ID:foo \
+ -pre LOAD \
+ -pre "CMD_FOO:some input data"
+
+ Or to simply see the list of commands supported by the "foo" ENGINE;
+
+ openssl engine -vvvv dynamic \
+ -pre SO_PATH:/lib/libfoo.so \
+ -pre ID:foo \
+ -pre LOAD
+
+ Applications that support the ENGINE API and more specifically, the
+ "control commands" mechanism, will provide some way for you to pass
+ such commands through to ENGINEs. As such, you would select "dynamic"
+ as the ENGINE to use, and the parameters/commands you pass would
+ control the *actual* ENGINE used. Each command is actually a name-value
+ pair and the value can sometimes be omitted (eg. the "LOAD" command).
+ Whilst the syntax demonstrated in "openssl engine" uses a colon to
+ separate the command name from the value, applications may provide
+ their own syntax for making that separation (eg. a win32 registry
+ key-value pair may be used by some applications). The reason for the
+ "-pre" syntax in the "openssl engine" utility is that some commands
+ might be issued to an ENGINE *after* it has been initialised for use.
+ Eg. if an ENGINE implementation requires a smart-card to be inserted
+ during initialisation (or a PIN to be typed, or whatever), there may be
+ a control command you can issue afterwards to "forget" the smart-card
+ so that additional initialisation is no longer possible. In
+ applications such as web-servers, where potentially volatile code may
+ run on the same host system, this may provide some arguable security
+ value. In such a case, the command would be passed to the ENGINE after
+ it has been initialised for use, and so the "-post" switch would be
+ used instead. Applications may provide a different syntax for
+ supporting this distinction, and some may simply not provide it at all
+ ("-pre" is almost always what you're after, in reality).
How do I build a "dynamic" ENGINE?
----------------------------------
- This question is trickier - currently OpenSSL bundles various ENGINE
- implementations that are statically built in, and any application that
- calls the "ENGINE_load_builtin_engines()" function will automatically
- have all such ENGINEs available (and occupying memory). Applications
- that don't call that function have no ENGINEs available like that and
- would have to use "dynamic" to load any such ENGINE - but on the other
- hand such applications would only have the memory footprint of any
- ENGINEs explicitly loaded using user/admin provided control commands.
- The main advantage of not statically linking ENGINEs and only using
- "dynamic" for hardware support is that any installation using no
- "external" ENGINE suffers no unnecessary memory footprint from unused
- ENGINEs. Likewise, installations that do require an ENGINE incur the
- overheads from only *that* ENGINE once it has been loaded.
-
- Sounds good? Maybe, but currently building an ENGINE implementation as
- a shared-library that can be loaded by "dynamic" isn't automated in
- OpenSSL's build process. It can be done manually quite easily however.
- Such a shared-library can either be built with any OpenSSL code it
- needs statically linked in, or it can link dynamically against OpenSSL
- if OpenSSL itself is built as a shared library. The instructions are
- the same in each case, but in the former (statically linked any
- dependencies on OpenSSL) you must ensure OpenSSL is built with
- position-independent code ("PIC"). The default OpenSSL compilation may
- already specify the relevant flags to do this, but you should consult
- with your compiler documentation if you are in any doubt.
-
- This example will show building the "atalla" ENGINE in the
- crypto/engine/ directory as a shared-library for use via the "dynamic"
- ENGINE.
- 1) "cd" to the crypto/engine/ directory of a pre-compiled OpenSSL
- source tree.
- 2) Recompile at least one source file so you can see all the compiler
- flags (and syntax) being used to build normally. Eg;
- touch hw_atalla.c ; make
- will rebuild "hw_atalla.o" using all such flags.
- 3) Manually enter the same compilation line to compile the
- "hw_atalla.c" file but with the following two changes;
- (a) add "-DENGINE_DYNAMIC_SUPPORT" to the command line switches,
- (b) change the output file from "hw_atalla.o" to something new,
- eg. "tmp_atalla.o"
- 4) Link "tmp_atalla.o" into a shared-library using the top-level
- OpenSSL libraries to resolve any dependencies. The syntax for doing
- this depends heavily on your system/compiler and is a nightmare
- known well to anyone who has worked with shared-library portability
- before. 'gcc' on Linux, for example, would use the following syntax;
- gcc -shared -o dyn_atalla.so tmp_atalla.o -L../.. -lcrypto
- 5) Test your shared library using "openssl engine" as explained in the
- previous section. Eg. from the top-level directory, you might try;
- apps/openssl engine -vvvv dynamic \
- -pre SO_PATH:./crypto/engine/dyn_atalla.so -pre LOAD
- If the shared-library loads successfully, you will see both "-pre"
- commands marked as "SUCCESS" and the list of control commands
- displayed (because of "-vvvv") will be the control commands for the
- *atalla* ENGINE (ie. *not* the 'dynamic' ENGINE). You can also add
- the "-t" switch to the utility if you want it to try and initialise
- the atalla ENGINE for use to test any possible hardware/driver
- issues.
+
+ This question is trickier - currently OpenSSL bundles various ENGINE
+ implementations that are statically built in, and any application that
+ calls the "ENGINE_load_builtin_engines()" function will automatically
+ have all such ENGINEs available (and occupying memory). Applications
+ that don't call that function have no ENGINEs available like that and
+ would have to use "dynamic" to load any such ENGINE - but on the other
+ hand such applications would only have the memory footprint of any
+ ENGINEs explicitly loaded using user/admin provided control commands.
+ The main advantage of not statically linking ENGINEs and only using
+ "dynamic" for hardware support is that any installation using no
+ "external" ENGINE suffers no unnecessary memory footprint from unused
+ ENGINEs. Likewise, installations that do require an ENGINE incur the
+ overheads from only *that* ENGINE once it has been loaded.
+
+ Sounds good? Maybe, but currently building an ENGINE implementation as
+ a shared-library that can be loaded by "dynamic" isn't automated in
+ OpenSSL's build process. It can be done manually quite easily however.
+ Such a shared-library can either be built with any OpenSSL code it
+ needs statically linked in, or it can link dynamically against OpenSSL
+ if OpenSSL itself is built as a shared library. The instructions are
+ the same in each case, but in the former (statically linked any
+ dependencies on OpenSSL) you must ensure OpenSSL is built with
+ position-independent code ("PIC"). The default OpenSSL compilation may
+ already specify the relevant flags to do this, but you should consult
+ with your compiler documentation if you are in any doubt.
+
+ This example will show building the "atalla" ENGINE in the
+ crypto/engine/ directory as a shared-library for use via the "dynamic"
+ ENGINE.
+
+ 1. "cd" to the crypto/engine/ directory of a pre-compiled OpenSSL
+ source tree.
+
+ 2. Recompile at least one source file so you can see all the compiler
+ flags (and syntax) being used to build normally. Eg;
+
+ touch hw_atalla.c ; make
+
+ will rebuild "hw_atalla.o" using all such flags.
+
+ 3. Manually enter the same compilation line to compile the
+ "hw_atalla.c" file but with the following two changes;
+ * add "-DENGINE_DYNAMIC_SUPPORT" to the command line switches,
+ * change the output file from "hw_atalla.o" to something new,
+ eg. "tmp_atalla.o"
+
+ 4. Link "tmp_atalla.o" into a shared-library using the top-level
+ OpenSSL libraries to resolve any dependencies. The syntax for doing
+ this depends heavily on your system/compiler and is a nightmare
+ known well to anyone who has worked with shared-library portability
+ before. 'gcc' on Linux, for example, would use the following syntax;
+
+ gcc -shared -o dyn_atalla.so tmp_atalla.o -L../.. -lcrypto
+
+ 5. Test your shared library using "openssl engine" as explained in the
+ previous section. Eg. from the top-level directory, you might try
+
+ apps/openssl engine -vvvv dynamic \
+ -pre SO_PATH:./crypto/engine/dyn_atalla.so -pre LOAD
+
+ If the shared-library loads successfully, you will see both "-pre"
+ commands marked as "SUCCESS" and the list of control commands
+ displayed (because of "-vvvv") will be the control commands for the
+ *atalla* ENGINE (ie. *not* the 'dynamic' ENGINE). You can also add
+ the "-t" switch to the utility if you want it to try and initialise
+ the atalla ENGINE for use to test any possible hardware/driver issues.
PROBLEMS
========
projects / openssl.git / blobdiff