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Day 07: flappy.pl
Challenge
Time for a little game. It’s hardy obfuscated, i promise … ;-)
Solution*
Saving the perl script and running, it turns out to be a copy of flappy bird, in ascii. Pressing the space bar lets you move right, otherwise you fall left. After getting through the first three stages we saw that the barriers spelt HV1, so clearly going to be our key.
We reformat the script:
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use Term::ReadKey;
sub k {
ReadKey(-1)
};
ReadMode 3;
sub rk {
$Q='';$Q.=$QQ while($QQ=k());$Q
};
$|=1;
print "\ec\e[0;0r\e[4242;1H\e[6n\e[1;1H";
($p .= $c) until (($c=k()) eq 'R');
$x=75;
$dx=3;
(($yy) = ($p =~ /(\d+);/)) && ($yy-=10);
print (("\r\n\e[40m\e[37m#".(' 'x78)."#")x100);
$r=(sub {$M=shift;
sub {$M=(($M*0x41C64E6D)+12345)&0x7FFFFFFF;
$M%shift;
}})->(42);
$s=(sub {select($HV18, $faLL, $D33p, shift);});
$INT0?$H3ll:$PERL;
@HASH=unpack("C*",pack("H*",'73740c12387652487105575346620e6c55655e1b4b6b6f541a6b2d7275'));
for $i(0..666){
$s->(0.1);
print("\e[40;91m\e[${yy};${x}H.");
$dx += int(rk() =~ / /g)*2-1;
$dx = ($dx>3?3:($dx<-3?-3:$dx));
$x += $dx;
# BOUNDARY CHECK
#($x>1&&$x<80)||last;
(($i%23)&&print ("\e[4242;1H\n\e[40m\e[37m#".(' 'x78)."#"))||(($h=20+$r->(42))&&(print ("\e[4242;1H\n\e[40m\e[37m#".((chr($HASH[$i/23]^$h))x($h-5)).(" "x10).((chr($HASH[$i/23]^$h))x(73-$h))."#")));
# BARRIER CHECK
#(($i+13)%23)?42:((abs($x-$h)<6)||last);
print ("\e[${yy};${x}H\e[41m\e[37m@");
};
ReadMode 1;
And we comment out the checks for if we hit a barrier or a boundary that will ‘kill’ us. And then we just watch the flag scroll by and write it down as it passes.
Flag
HV18-bMnF-racH-XdMC-xSJJ-I2fL