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fc5acc0151
Implement proper synopsis wrapping for HTML generation. This was done in three pieces. First, add HTML-specific tags to the POD to mark the synopsis for HTML purposes so that we can apply style information to it. Second, update the style sheet to indent all lines except for the first in the synopsis section. Third, add the appropriate S<> tags around option and argument pairs so that we don't wrap between the option and its argument. Unfortunately, due to the <I<foo>> style that looks nicer for other reasons, we have to use the very verbose S<<< >>>. Oh well.
112 lines
4.0 KiB
Plaintext
112 lines
4.0 KiB
Plaintext
=head1 NAME
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pagsh - Creates a new PAG
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=head1 SYNOPSIS
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=for html
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<div class="synopsis">
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B<pagsh>
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=for html
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</div>
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=head1 DESCRIPTION
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The B<pagsh> command creates a new command shell (owned by the issuer of
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the command) and associates a new I<process authentication group> (PAG)
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with the shell and the user. A PAG is a number guaranteed to identify the
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issuer of commands in the new shell uniquely to the local Cache
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Manager. The PAG is used, instead of the issuer's UNIX UID, to identify
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the issuer in the credential structure that the Cache Manager creates to
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track each user.
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Any tokens acquired subsequently (presumably for other cells) become
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associated with the PAG, rather than with the user's UNIX UID. This
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method for distinguishing users has two advantages.
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=over 4
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=item *
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It means that processes spawned by the user inherit the PAG and so share
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the token; thus they gain access to AFS as the authenticated user. In
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many environments, for example, printer and other daemons run under
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identities (such as the local superuser C<root>) that the AFS server
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processes recognize only as C<anonymous>. Unless PAGs are used, such
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daemons cannot access files in directories whose access control lists
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(ACLs) do not extend permissions to the system:anyuser group.
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=item *
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It closes a potential security loophole: UNIX allows anyone already logged
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in as the local superuser C<root> on a machine to assume any other
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identity by issuing the UNIX B<su> command. If the credential structure is
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identified by a UNIX UID rather than a PAG, then the local superuser
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C<root> can assume a UNIX UID and use any tokens associated with that
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UID. Use of a PAG as an identifier eliminates that possibility.
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=back
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=head1 CAUTIONS
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Each PAG created uses two of the memory slots that the kernel uses to
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record the UNIX groups associated with a user. If none of these slots are
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available, the B<pagsh> command fails. This is not a problem with most
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operating systems, which make at least 16 slots available per user.
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In cells that do not use an AFS-modified login utility, use this command
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to obtain a PAG before issuing the B<klog> command (or include the
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B<-setpag> argument to the B<klog> command). If a PAG is not acquired, the
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Cache Manager stores the token in a credential structure identified by
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local UID rather than PAG. This creates the potential security exposure
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described in L<DESCRIPTION>.
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If users of NFS client machines for which AFS is supported are to issue
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this command as part of authenticating with AFS, do not use the B<fs
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exportafs> command's B<-uidcheck on> argument to enable UID checking on
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NFS/AFS Translator machines. Enabling UID checking prevents this command
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from succeeding. See L<klog(1)>.
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If UID checking is not enabled on Translator machines, then by default it
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is possible to issue this command on a properly configured NFS client
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machine that is accessing AFS via the NFS/AFS Translator, assuming that
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the NFS client machine is a supported system type. The B<pagsh> binary
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accessed by the NFS client must be owned by, and grant setuid privilege
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to, the local superuser C<root>. The complete set of mode bits must be
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C<-rwsr-xr-x>. This is not a requirement when the command is issued on AFS
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client machines.
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However, if the translator machine's administrator has enabled UID
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checking by including the B<-uidcheck on> argument to the B<fs exportafs>
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command, the command fails with an error message similar to the following:
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Warning: Remote setpag to <translator_machine> has failed (err=8). . .
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setpag: Exec format error
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=head1 EXAMPLES
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In the following example, the issuer invokes the C shell instead of the
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default Bourne shell:
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# pagsh -c /bin/csh
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=head1 PRIVILEGE REQUIRED
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None
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=head1 SEE ALSO
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L<fs_exportafs(1)>,
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L<klog(1)>,
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L<tokens(1)>
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=head1 COPYRIGHT
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IBM Corporation 2000. <http://www.ibm.com/> All Rights Reserved.
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This documentation is covered by the IBM Public License Version 1.0. It was
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converted from HTML to POD by software written by Chas Williams and Russ
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Allbery, based on work by Alf Wachsmann and Elizabeth Cassell.
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