xref: /titanic_41/usr/src/lib/libgss/README.spi (revision 159d09a20817016f09b3ea28d1bdada4a336bb91)
1
2 CDDL HEADER START
3
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.
8
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
12 and limitations under the License.
13
14 When distributing Covered Code, include this CDDL HEADER in each
15 file and include the License file at usr/src/OPENSOLARIS.LICENSE.
16 If applicable, add the following below this CDDL HEADER, with the
17 fields enclosed by brackets "[]" replaced with your own identifying
18 information: Portions Copyright [yyyy] [name of copyright owner]
19
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
331.  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
452.  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
753.  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 */
120