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   2  CDDL HEADER START
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   4  The contents of this file are subject to the terms of the
   5  Common Development and Distribution License, Version 1.0 only
   6  (the "License").  You may not use this file except in compliance
   7  with the License.
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   9  You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
  10  or http://www.opensolaris.org/os/licensing.
  11  See the License for the specific language governing permissions
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  14  When distributing Covered Code, include this CDDL HEADER in each
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  16  If applicable, add the following below this CDDL HEADER, with the
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  20  CDDL HEADER END
  21 
  22  Copyright 2005 Sun Microsystems, Inc.  All rights reserved.
  23  Use is subject to license terms.
  24 
  25 #ident  "%Z%%M% %I%     %E% SMI"
  26 
  27 
  28         The Service Provider Interface for libgss and its Mechanisms
  29         ------------------------------------------------------------
  30 
  31 /* CRYPT DELETE START */
  32 
  33 1.  The libgss SPI upto 11/2004
  34 
  35     Prior to PSARC 2004/810 the libgss SPI consisted of a function
  36     provided by each mechanism whose return value is a pointer to a
  37     structure full of references to the mechanism's entry points
  38     (hereinafter: methods).
  39 
  40     This structure does not include any hooks for versioning, which
  41     means that additions of any mechanism methods at micro/patch
  42     releases require patching libgss.so.1 and all the GSS mechanisms
  43     shipped with Solaris (Kerberos V, DH, SPNEGO).
  44 
  45 2.  The libgss SPI after PSARC 2004/810
  46 
  47     In order to avoid changing the gss_config struct and patching all
  48     three mechanisms (four, if the dummy mech counts) and libgss
  49     together and in anticipation of a cleaner SPI in the future (see
  50     next section) the SPI after PSARC 2004/810 will be as before but
  51     supplemented as follows:
  52 
  53      - any new SPI mechanism methods will NOT be placed in gss_config,
  54        instead there is a new gss_config_ext structure, which is to be
  55        used _only_ by libgss (to avoid struct versioning and/or patch
  56        issues), which should be extended to have a pointer to the new
  57        method;
  58 
  59      - there is a new libgss function, __gss_get_mechanism_ext(), which
  60        is used to get at the gss_config_ext for a mechanism;
  61 
  62      - __gss_get_mechanism_ext() uses dlsym() to build the
  63        gss_config_ext struct for the mech by individually loading each
  64        and every mechanism method that isn't part of the old gss_config
  65        struct -- this happens only once per-method, of course; the
  66        result is cached.
  67 
  68        The symbol names that are dlsym()ed are of the form gssspi_* and
  69        correspond to gss_*; e.g., gssspi_acquire_cred_with_password().
  70 
  71        New methods also have a corresponding typedef named
  72        <gss_func>_sfct -- the 's' in 'sfct' is for "SPI" and the 'fct'
  73        is for "function."  This is used to keep cast expressions short.
  74 
  75 3.  The Future libgss SPI
  76 
  77     Once the Solaris krb5 source is resync'ed with MIT krb5 1.4 there
  78     will be no further need for the 'void *context' argument to all the
  79     libgss mechanisms' methods.
  80 
  81     At that point it will be possible to remove this 'void *context'
  82     argument from all the libgss SPI function prototypes, the main
  83     result of which will be that the mechanisms' methods will then have
  84     the same function signature as the corresponding GSS-API functions.
  85 
  86     We can then rename all mechanisms' methods from <mech>_<gss-func> to
  87     <gss-func>.  The corresponding typedefs will be renamed to
  88     <gss-func>_fct.
  89 
  90     The SPI, then, will be almost exactly the same as the API.
  91 
  92     There will be some minor differences, primarily that some API
  93     functions won't have a corresponding SPI method, such as
  94     gss_release_buffer(3GSS), for example.
  95 
  96     Some time later we may open the SPI to third party implementors;
  97     this could be particularly useful as a way to get access to 3rd
  98     party implementations of SPKM and LIPKEY (assuming any ever exist --
  99     SPKM's is a very problematic specification).
 100 
 101     Third party mechanisms should just export all the symbols for the
 102     GSS-API functions, like MIT krb5 does, but functions which libgss
 103     won't call (e.g., gss_release_buffer(3GSS)) should either not be
 104     implemented or should be weak symbols.
 105 
 106     Solaris native mechanisms may still provide the mechanism method
 107     registration function as usual for optimization purposes -- to
 108     reduce the number of calls to dlsym().
 109 
 110     Mechanisms that do not provide the old method registration function
 111     will be loaded as follows:
 112 
 113      - libgss will look for and find the mechanism's
 114        GSS_Indicate_mechs() method and will call it to discover the
 115        mechanism provider's mechanism OIDs.
 116 
 117      - libgss will dlsym() each mechanism provider SPI method.
 118 
 119 /* CRYPT DELETE END */