1 | package filetest;
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2 |
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3 | our $VERSION = '1.01';
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4 |
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5 | =head1 NAME
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6 |
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7 | filetest - Perl pragma to control the filetest permission operators
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8 |
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9 | =head1 SYNOPSIS
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10 |
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11 | $can_perhaps_read = -r "file"; # use the mode bits
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12 | {
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13 | use filetest 'access'; # intuit harder
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14 | $can_really_read = -r "file";
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15 | }
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16 | $can_perhaps_read = -r "file"; # use the mode bits again
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17 |
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18 | =head1 DESCRIPTION
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19 |
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20 | This pragma tells the compiler to change the behaviour of the filetest
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21 | permission operators, C<-r> C<-w> C<-x> C<-R> C<-W> C<-X>
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22 | (see L<perlfunc>).
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23 |
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24 | The default behaviour is to use the mode bits as returned by the stat()
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25 | family of calls. This, however, may not be the right thing to do if
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26 | for example various ACL (access control lists) schemes are in use.
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27 | For such environments, C<use filetest> may help the permission
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28 | operators to return results more consistent with other tools.
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29 |
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30 | Each "use filetest" or "no filetest" affects statements to the end of
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31 | the enclosing block.
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32 |
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33 | There may be a slight performance decrease in the filetests
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34 | when C<use filetest> is in effect, because in some systems
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35 | the extended functionality needs to be emulated.
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36 |
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37 | B<NOTE>: using the file tests for security purposes is a lost cause
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38 | from the start: there is a window open for race conditions (who is to
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39 | say that the permissions will not change between the test and the real
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40 | operation?). Therefore if you are serious about security, just try
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41 | the real operation and test for its success - think in terms of atomic
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42 | operations.
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43 |
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44 | =head2 subpragma access
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45 |
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46 | Currently only one subpragma, C<access> is implemented. It enables
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47 | (or disables) the use of access() or similar system calls. This
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48 | extended filetest functionality is used only when the argument of the
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49 | operators is a filename, not when it is a filehandle.
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50 |
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51 | =cut
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52 |
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53 | $filetest::hint_bits = 0x00400000; # HINT_FILETEST_ACCESS
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54 |
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55 | sub import {
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56 | if ( $_[1] eq 'access' ) {
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57 | $^H |= $filetest::hint_bits;
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58 | } else {
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59 | die "filetest: the only implemented subpragma is 'access'.\n";
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60 | }
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61 | }
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62 |
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63 | sub unimport {
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64 | if ( $_[1] eq 'access' ) {
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65 | $^H &= ~$filetest::hint_bits;
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66 | } else {
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67 | die "filetest: the only implemented subpragma is 'access'.\n";
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68 | }
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69 | }
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70 |
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71 | 1;
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