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 (the "License"). 6 You may not use this file except in compliance with the License. 7 8 You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE 9 or http://www.opensolaris.org/os/licensing. 10 See the License for the specific language governing permissions 11 and limitations under the License. 12 13 When distributing Covered Code, include this CDDL HEADER in each 14 file and include the License file at usr/src/OPENSOLARIS.LICENSE. 15 If applicable, add the following below this CDDL HEADER, with the 16 fields enclosed by brackets "[]" replaced with your own identifying 17 information: Portions Copyright [yyyy] [name of copyright owner] 18 19 CDDL HEADER END 20 21 Copyright 2010 Sun Microsystems, Inc. All rights reserved. 22 Use is subject to license terms. 23 24 25 The Service Provider Interface for libgss and its Mechanisms 26 ------------------------------------------------------------ 27 281. The libgss SPI upto 11/2004 29 30 Prior to PSARC 2004/810 the libgss SPI consisted of a function 31 provided by each mechanism whose return value is a pointer to a 32 structure full of references to the mechanism's entry points 33 (hereinafter: methods). 34 35 This structure does not include any hooks for versioning, which 36 means that additions of any mechanism methods at micro/patch 37 releases require patching libgss.so.1 and all the GSS mechanisms 38 shipped with Solaris (Kerberos V, DH, SPNEGO). 39 402. The libgss SPI after PSARC 2004/810 41 42 In order to avoid changing the gss_config struct and patching all 43 three mechanisms (four, if the dummy mech counts) and libgss 44 together and in anticipation of a cleaner SPI in the future (see 45 next section) the SPI after PSARC 2004/810 will be as before but 46 supplemented as follows: 47 48 - any new SPI mechanism methods will NOT be placed in gss_config, 49 instead there is a new gss_config_ext structure, which is to be 50 used _only_ by libgss (to avoid struct versioning and/or patch 51 issues), which should be extended to have a pointer to the new 52 method; 53 54 - there is a new libgss function, __gss_get_mechanism_ext(), which 55 is used to get at the gss_config_ext for a mechanism; 56 57 - __gss_get_mechanism_ext() uses dlsym() to build the 58 gss_config_ext struct for the mech by individually loading each 59 and every mechanism method that isn't part of the old gss_config 60 struct -- this happens only once per-method, of course; the 61 result is cached. 62 63 The symbol names that are dlsym()ed are of the form gssspi_* and 64 correspond to gss_*; e.g., gssspi_acquire_cred_with_password(). 65 66 New methods also have a corresponding typedef named 67 <gss_func>_sfct -- the 's' in 'sfct' is for "SPI" and the 'fct' 68 is for "function." This is used to keep cast expressions short. 69 703. The Future libgss SPI 71 72 Once the Solaris krb5 source is resync'ed with MIT krb5 1.4 there 73 will be no further need for the 'void *context' argument to all the 74 libgss mechanisms' methods. 75 76 At that point it will be possible to remove this 'void *context' 77 argument from all the libgss SPI function prototypes, the main 78 result of which will be that the mechanisms' methods will then have 79 the same function signature as the corresponding GSS-API functions. 80 81 We can then rename all mechanisms' methods from <mech>_<gss-func> to 82 <gss-func>. The corresponding typedefs will be renamed to 83 <gss-func>_fct. 84 85 The SPI, then, will be almost exactly the same as the API. 86 87 There will be some minor differences, primarily that some API 88 functions won't have a corresponding SPI method, such as 89 gss_release_buffer(3GSS), for example. 90 91 Some time later we may open the SPI to third party implementors; 92 this could be particularly useful as a way to get access to 3rd 93 party implementations of SPKM and LIPKEY (assuming any ever exist -- 94 SPKM's is a very problematic specification). 95 96 Third party mechanisms should just export all the symbols for the 97 GSS-API functions, like MIT krb5 does, but functions which libgss 98 won't call (e.g., gss_release_buffer(3GSS)) should either not be 99 implemented or should be weak symbols. 100 101 Solaris native mechanisms may still provide the mechanism method 102 registration function as usual for optimization purposes -- to 103 reduce the number of calls to dlsym(). 104 105 Mechanisms that do not provide the old method registration function 106 will be loaded as follows: 107 108 - libgss will look for and find the mechanism's 109 GSS_Indicate_mechs() method and will call it to discover the 110 mechanism provider's mechanism OIDs. 111 112 - libgss will dlsym() each mechanism provider SPI method. 113