CDDL HEADER START The contents of this file are subject to the terms of the Common Development and Distribution License (the "License"). You may not use this file except in compliance with the License. You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE or http://www.opensolaris.org/os/licensing. See the License for the specific language governing permissions and limitations under the License. When distributing Covered Code, include this CDDL HEADER in each file and include the License file at usr/src/OPENSOLARIS.LICENSE. If applicable, add the following below this CDDL HEADER, with the fields enclosed by brackets "[]" replaced with your own identifying information: Portions Copyright [yyyy] [name of copyright owner] CDDL HEADER END Copyright 2010 Sun Microsystems, Inc. All rights reserved. Use is subject to license terms. The Service Provider Interface for libgss and its Mechanisms ------------------------------------------------------------ 1. The libgss SPI upto 11/2004 Prior to PSARC 2004/810 the libgss SPI consisted of a function provided by each mechanism whose return value is a pointer to a structure full of references to the mechanism's entry points (hereinafter: methods). This structure does not include any hooks for versioning, which means that additions of any mechanism methods at micro/patch releases require patching libgss.so.1 and all the GSS mechanisms shipped with Solaris (Kerberos V, DH, SPNEGO). 2. The libgss SPI after PSARC 2004/810 In order to avoid changing the gss_config struct and patching all three mechanisms (four, if the dummy mech counts) and libgss together and in anticipation of a cleaner SPI in the future (see next section) the SPI after PSARC 2004/810 will be as before but supplemented as follows: - any new SPI mechanism methods will NOT be placed in gss_config, instead there is a new gss_config_ext structure, which is to be used _only_ by libgss (to avoid struct versioning and/or patch issues), which should be extended to have a pointer to the new method; - there is a new libgss function, __gss_get_mechanism_ext(), which is used to get at the gss_config_ext for a mechanism; - __gss_get_mechanism_ext() uses dlsym() to build the gss_config_ext struct for the mech by individually loading each and every mechanism method that isn't part of the old gss_config struct -- this happens only once per-method, of course; the result is cached. The symbol names that are dlsym()ed are of the form gssspi_* and correspond to gss_*; e.g., gssspi_acquire_cred_with_password(). New methods also have a corresponding typedef named <gss_func>_sfct -- the 's' in 'sfct' is for "SPI" and the 'fct' is for "function." This is used to keep cast expressions short. 3. The Future libgss SPI Once the Solaris krb5 source is resync'ed with MIT krb5 1.4 there will be no further need for the 'void *context' argument to all the libgss mechanisms' methods. At that point it will be possible to remove this 'void *context' argument from all the libgss SPI function prototypes, the main result of which will be that the mechanisms' methods will then have the same function signature as the corresponding GSS-API functions. We can then rename all mechanisms' methods from <mech>_<gss-func> to <gss-func>. The corresponding typedefs will be renamed to <gss-func>_fct. The SPI, then, will be almost exactly the same as the API. There will be some minor differences, primarily that some API functions won't have a corresponding SPI method, such as gss_release_buffer(3GSS), for example. Some time later we may open the SPI to third party implementors; this could be particularly useful as a way to get access to 3rd party implementations of SPKM and LIPKEY (assuming any ever exist -- SPKM's is a very problematic specification). Third party mechanisms should just export all the symbols for the GSS-API functions, like MIT krb5 does, but functions which libgss won't call (e.g., gss_release_buffer(3GSS)) should either not be implemented or should be weak symbols. Solaris native mechanisms may still provide the mechanism method registration function as usual for optimization purposes -- to reduce the number of calls to dlsym(). Mechanisms that do not provide the old method registration function will be loaded as follows: - libgss will look for and find the mechanism's GSS_Indicate_mechs() method and will call it to discover the mechanism provider's mechanism OIDs. - libgss will dlsym() each mechanism provider SPI method.