183 lines
4.4 KiB
Groff
183 lines
4.4 KiB
Groff
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.\" $Id: acl_check.3,v 1.2 1996/06/12 21:29:08 bg Exp $
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.\" Copyright 1989 by the Massachusetts Institute of Technology.
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.\"
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.\" For copying and distribution information,
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.\" please see the file <mit-copyright.h>.
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.\"
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.TH ACL_CHECK 3 "Kerberos Version 4.0" "MIT Project Athena"
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.SH NAME
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acl_canonicalize_principal, acl_check, acl_exact_match, acl_add,
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acl_delete, acl_initialize \- Access control list routines
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.SH SYNOPSIS
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.nf
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.nj
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.ft B
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cc <files> \-lacl \-lkrb
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.PP
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.ft B
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#include <krb.h>
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.PP
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.ft B
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acl_canonicalize_principal(principal, buf)
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char *principal;
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char *buf;
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.PP
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.ft B
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acl_check(acl, principal)
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char *acl;
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char *principal;
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.PP
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.ft B
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acl_exact_match(acl, principal)
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char *acl;
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char *principal;
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.PP
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.ft B
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acl_add(acl, principal)
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char *acl;
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char *principal;
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.PP
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.ft B
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acl_delete(acl, principal)
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char *acl;
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char *principal;
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.PP
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.ft B
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acl_initialize(acl_file, mode)
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char *acl_file;
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int mode;
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.fi
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.ft R
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.SH DESCRIPTION
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.SS Introduction
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.PP
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An access control list (ACL) is a list of principals, where each
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principal is represented by a text string which cannot contain
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whitespace. The library allows application programs to refer to named
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access control lists to test membership and to atomically add and
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delete principals using a natural and intuitive interface. At
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present, the names of access control lists are required to be Unix
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filenames, and refer to human-readable Unix files; in the future, when
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a networked ACL server is implemented, the names may refer to a
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different namespace specific to the ACL service.
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.PP
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.SS Principal Names
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.PP
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Principal names have the form
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.nf
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.in +5n
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<name>[.<instance>][@<realm>]
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.in -5n
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e.g.:
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.in +5n
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asp
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asp.root
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asp@ATHENA.MIT.EDU
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asp.@ATHENA.MIT.EDU
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asp.root@ATHENA.MIT.EDU
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.in -5n
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.fi
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It is possible for principals to be underspecified. If an instance is
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missing, it is assumed to be "". If realm is missing, it is assumed
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to be the local realm as determined by
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.IR krb_get_lrealm (3).
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The canonical form contains all of name, instance,
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and realm; the acl_add and acl_delete routines will always
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leave the file in that form. Note that the canonical form of
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asp@ATHENA.MIT.EDU is actually asp.@ATHENA.MIT.EDU.
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.SS Routines
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.PP
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.I acl_canonicalize_principal
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stores the canonical form of
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.I principal
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in
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.IR buf .
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.I Buf
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must contain enough
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space to store a principal, given the limits on the sizes of name,
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instance, and realm specified as ANAME_SZ, INST_SZ, and REALM_SZ,
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respectively, in
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.IR /usr/include/krb.h .
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.PP
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.I acl_check
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returns nonzero if
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.I principal
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appears in
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.IR acl .
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Returns 0 if principal
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does not appear in acl, or if an error occurs. Canonicalizes
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principal before checking, and allows the ACL to contain wildcards. The
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only supported wildcards are entries of the form
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name.*@realm, *.*@realm, and *.*@*. An asterisk matches any value for the
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its component field. For example, "jtkohl.*@*" would match principal
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jtkohl, with any instance and any realm.
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.PP
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.I acl_exact_match
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performs like
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.IR acl_check ,
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but does no canonicalization or wildcard matching.
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.PP
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.I acl_add
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atomically adds
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.I principal
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to
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.IR acl .
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Returns 0 if successful, nonzero otherwise. It is considered a failure
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if
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.I principal
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is already in
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.IR acl .
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This routine will canonicalize
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.IR principal ,
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but will treat wildcards literally.
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.PP
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.I acl_delete
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atomically deletes
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.I principal
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from
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.IR acl .
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Returns 0 if successful,
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nonzero otherwise. It is considered a failure if
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.I principal
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is not
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already in
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.IR acl .
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This routine will canonicalize
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.IR principal ,
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but will treat wildcards literally.
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.PP
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.I acl_initialize
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initializes
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.IR acl_file .
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If the file
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.I acl_file
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does not exist,
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.I acl_initialize
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creates it with mode
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.IR mode .
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If the file
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.I acl_file
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exists,
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.I acl_initialize
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removes all members. Returns 0 if successful,
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nonzero otherwise. WARNING: Mode argument is likely to change with
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the eventual introduction of an ACL service.
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.SH NOTES
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In the presence of concurrency, there is a very small chance that
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.I acl_add
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or
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.I acl_delete
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could report success even though it would have
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had no effect. This is a necessary side effect of using lock files
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for concurrency control rather than flock(2), which is not supported
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by NFS.
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.PP
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The current implementation caches ACLs in memory in a hash-table
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format for increased efficiency in checking membership; one effect of
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the caching scheme is that one file descriptor will be kept open for
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each ACL cached, up to a maximum of 8.
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.SH SEE ALSO
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kerberos(3), krb_get_lrealm(3)
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.SH AUTHOR
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James Aspnes (MIT Project Athena)
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