Re: crypt sometimes returning undef

I was reading the documentation of crypt and I noticed from the sample code:

if (crypt($word, $pwd) ne $pwd) {
    die "Sorry...\n";
} else {
    print "ok\n";
}
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They are using first the word and then the password. It is not related to your problem but I think it would be more clear in future reference:

my $cryptedpass = crypt($passwrd1, substr($never_blank_value, 0, 2));
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The only reason that I can imagine that you might have $cryptedpass as blank is that you have $never_blank_value. You are using substr and you are cutting off the first 2 characters of the string. In case the string it has less than 2 characters then you will end up with undef value. Sample of proposed code:

#!/usr/bin/perl
use strict;
use warnings;
use feature 'say';

my $never_blank_value = 'T';
my @passset = ('a'..'k', 'm'..'n', 'p'..'z', '2'..'9');
my $passwrd1 = "";
for (my $i=0; $i<8; $i++) {
    $passwrd1 .= $passset[int(rand($#passset + 1))];
}

die 'Too small \$never_blank_value' if length $never_blank_value < 2;
my $cryptedpass = crypt($passwrd1, substr($never_blank_value, 0, 2));
say $cryptedpass;

__END__

$ perl test.pl
Too small \$never_blank_value at test.pl line 13.
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Sample of error:

#!/usr/bin/perl
use strict;
use warnings;
use feature 'say';

my $never_blank_value = 'T';
my @passset = ('a'..'k', 'm'..'n', 'p'..'z', '2'..'9');
my $passwrd1 = "";
for (my $i=0; $i<8; $i++) {
    $passwrd1 .= $passset[int(rand($#passset + 1))];
}

# die 'Too small \$never_blank_value' if length $never_blank_value < 2
+;
my $cryptedpass = crypt($passwrd1, substr($never_blank_value, 0, 2));
say $cryptedpass;

__END__

 perl test.pl
Use of uninitialized value $cryptedpass in say at test.pl line 15.
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Update: Based on the link 0007695: Crypt bug that fellow Monk poj point it out you might be passing non acceptable characters. If this is the case add this to your code:

die 'Not accepted characters at \$never_blank_value'
    unless ($never_blank_value =~ /^[a-zA-Z0-9.\/]+$/);
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Hope this helps, BR.

Seeking for Perl wisdom...on the process of learning...not there...yet!

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Re^2: crypt sometimes returning undef by Beaker (Beadle) on Feb 15, 2018 at 11:05 UTC
Thank you, I believe this is the issue. My debug for an instance of this undef value has $never_blank_value as T_ (after substr) $never_blank_value contains a–zA–Z0–9\-_ so it's likely this would break if it contains the hyphen or underscore, I will run a regex over $never_blank_value to filter out these disallowed characters.	[reply]