path: root/contrib/libs/openssl/README.ENGINE

  ENGINE 
  ====== 
 
  With OpenSSL 0.9.6, a new component was added to support alternative 
  cryptography implementations, most commonly for interfacing with external 
  crypto devices (eg. accelerator cards). This component is called ENGINE, 
  and its presence in OpenSSL 0.9.6 (and subsequent bug-fix releases) 
  caused a little confusion as 0.9.6** releases were rolled in two 
  versions, a "standard" and an "engine" version. In development for 0.9.7, 
  the ENGINE code has been merged into the main branch and will be present 
  in the standard releases from 0.9.7 forwards. 
 
  There are currently built-in ENGINE implementations for the following 
  crypto devices: 
 
      o Microsoft CryptoAPI 
      o VIA Padlock 
      o nCipher CHIL 
 
  In addition, dynamic binding to external ENGINE implementations is now 
  provided by a special ENGINE called "dynamic". See the "DYNAMIC ENGINE" 
  section below for details. 
 
  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 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 
  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 
  based input to those ENGINEs, in the form of name-value pairs. This is an 
  extensible way for ENGINEs to define their own "configuration" mechanisms 
  that are specific to a given ENGINE (eg. for a particular hardware 
  device) but that should be consistent across *all* OpenSSL-based 
  applications when they use that ENGINE. Work is in progress (or at least 
  in planning) for supporting these control commands from the CONF (or 
  NCONF) code so that applications using OpenSSL's existing configuration 
  file format can have ENGINE settings specified in much the same way. 
  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; 
       openssl engine -vvvv 
 
3 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 
  would help make this happen. 
 
  STABILITY & BUG-REPORTS 
  ======================= 
 
  What already exists is fairly stable as far as it has been tested, but 
  the test base has been a bit small most of the time. For the most part, 
  the vendors of the devices these ENGINEs support have contributed to the 
  development and/or testing of the implementations, and *usually* (with no 
  guarantees) have experience in using the ENGINE support to drive their 
  devices from common OpenSSL-based applications. Bugs and/or inexplicable 
  behaviour in using a specific ENGINE implementation should be sent to the 
  author of that implementation (if it is mentioned in the corresponding C 
  file), and in the case of implementations for commercial hardware 
  devices, also through whatever vendor support channels are available.  If 
  none of this is possible, or the problem seems to be something about the 
  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; 
 
     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. 
 
  USAGE 
  ===== 
 
  The default "openssl" ENGINE is always chosen when performing crypto 
  operations unless you specify otherwise. You must actively tell the 
  openssl utility commands to use anything else through a new command line 
  switch called "-engine". Also, if you want to use the ENGINE support in 
  your own code to do something similar, you must likewise explicitly 
  select the ENGINE implementation you want. 
 
  Depending on the type of hardware, system, and configuration, "settings" 
  may need to be applied to an ENGINE for it to function as expected/hoped. 
  The recommended way of doing this is for the application to support 
  ENGINE "control commands" so that each ENGINE implementation can provide 
  whatever configuration primitives it might require and the application 
  can allow the user/admin (and thus the hardware vendor's support desk 
  also) to provide any such input directly to the ENGINE implementation. 
  This way, applications do not need to know anything specific to any 
  device, they only need to provide the means to carry such user/admin 
  input through to the ENGINE in question. Ie. this connects *you* (and 
  your helpdesk) to the specific ENGINE implementation (and device), and 
  allows application authors to not get buried in hassle supporting 
  arbitrary devices they know (and care) nothing about. 
 
  A new "openssl" utility, "openssl engine", has been added in that allows 
  for testing and examination of ENGINE implementations. Basic usage 
  instructions are available by specifying the "-?" command line switch. 
 
  DYNAMIC ENGINES 
  =============== 
 
  The new "dynamic" ENGINE provides a low-overhead way to support ENGINE 
  implementations that aren't pre-compiled and linked into OpenSSL-based 
  applications. This could be because existing compiled-in implementations 
  have known problems and you wish to use a newer version with an existing 
  application. It could equally be because the application (or OpenSSL 
  library) you are using simply doesn't have support for the ENGINE you 
  wish to use, and the ENGINE provider (eg. hardware vendor) is providing 
  you with a self-contained implementation in the form of a shared-library. 
  The other use-case for "dynamic" is with applications that wish to 
  maintain the smallest foot-print possible and so do not link in various 
  ENGINE implementations from OpenSSL, but instead leaves you to provide 
  them, if you want them, in the form of "dynamic"-loadable 
  shared-libraries. It should be possible for hardware vendors to provide 
  their own shared-libraries to support arbitrary hardware to work with 
  applications based on OpenSSL 0.9.7 or later. If you're using an 
  application based on 0.9.7 (or later) and the support you desire is only 
  announced for versions later than the one you need, ask the vendor to 
  backport their ENGINE to the version you need. 
 
  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). 
 
  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. 
 
  PROBLEMS 
  ======== 
 
  It seems like the ENGINE part doesn't work too well with CryptoSwift on Win32. 
  A quick test done right before the release showed that trying "openssl speed 
  -engine cswift" generated errors. If the DSO gets enabled, an attempt is made 
  to write at memory address 0x00000002.