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package filetest; |
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our $VERSION = '1.01'; |
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=head1 NAME |
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filetest - Perl pragma to control the filetest permission operators |
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=head1 SYNOPSIS |
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$can_perhaps_read = -r "file"; # use the mode bits |
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{ |
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use filetest 'access'; # intuit harder |
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$can_really_read = -r "file"; |
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} |
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$can_perhaps_read = -r "file"; # use the mode bits again |
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=head1 DESCRIPTION |
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This pragma tells the compiler to change the behaviour of the filetest |
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permission operators, C<-r> C<-w> C<-x> C<-R> C<-W> C<-X> |
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(see L<perlfunc>). |
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The default behaviour is to use the mode bits as returned by the stat() |
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family of calls. This, however, may not be the right thing to do if |
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for example various ACL (access control lists) schemes are in use. |
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For such environments, C<use filetest> may help the permission |
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operators to return results more consistent with other tools. |
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Each "use filetest" or "no filetest" affects statements to the end of |
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the enclosing block. |
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There may be a slight performance decrease in the filetests |
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when C<use filetest> is in effect, because in some systems |
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the extended functionality needs to be emulated. |
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B<NOTE>: using the file tests for security purposes is a lost cause |
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from the start: there is a window open for race conditions (who is to |
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say that the permissions will not change between the test and the real |
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operation?). Therefore if you are serious about security, just try |
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the real operation and test for its success - think in terms of atomic |
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operations. |
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=head2 subpragma access |
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Currently only one subpragma, C<access> is implemented. It enables |
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(or disables) the use of access() or similar system calls. This |
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extended filetest functionality is used only when the argument of the |
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operators is a filename, not when it is a filehandle. |
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=cut |
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$filetest::hint_bits = 0x00400000; # HINT_FILETEST_ACCESS |
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sub import { |
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if ( $_[1] eq 'access' ) { |
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$^H |= $filetest::hint_bits; |
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} else { |
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die "filetest: the only implemented subpragma is 'access'.\n"; |
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} |
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} |
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sub unimport { |
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if ( $_[1] eq 'access' ) { |
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$^H &= ~$filetest::hint_bits; |
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} else { |
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die "filetest: the only implemented subpragma is 'access'.\n"; |
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} |
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} |
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1; |
