plaidctf2015 uncorrupt png

The execution time of the code is very long, very embarrassing!

Reference the code of the https://13c5.wordpress.com/2015/04/20/plaidctf-2015-png-uncorrupt/

Through this topic, also to the PNG file format more in-depth understanding!

The premise of using this code is to change the 0x0a inside PNG signature to 0x0d0a

1  fromItertools Import Combinations2 Import Binascii3 Import OS4 5 6 def find_all (source,aim):7start=08       whileTrue:9start=Source.find (Aim,start)Ten           ifstart==-1: One                return A           yieldStart -Start + =Len (AIM) -  the def repair (SOURCE,AIM,FILEDES,NUM,CRC): -Matchlist=list (Find_all (source,'\x0a')) -  -       forSubnetinchcombinations (matchlist,num): +subnet=sorted (subnet) -temp="' +           if(num==3): Atemp=source[:subnet[0]]+'\x0d\x0a'+source[subnet[0]+1: subnet[1]]+'\x0d\x0a'+source[subnet[1]+1: subnet[2]]+'\x0d\x0a'+source[subnet[2]+1:] at           if(num==2): -temp=source[:subnet[0]]+'\x0d\x0a'+source[subnet[0]+1: subnet[1]]+'\x0d\x0a'+source[subnet[1]+1:] -           if(num==1): -temp=source[:subnet[0]]+'\x0d\x0a'+source[subnet[0]+1:] -           if "%08x"% (BINASCII.CRC32 (temp) &0xFFFFFFFF)==CRC: - filedes.write (temp) in Filedes.write (Binascii.a2b_hex (CRC)) - Filedes.flush () toPrint"Success" +                 Break; -Print"fail" the  *Uncfile=open ("Corrupt_735acee15fa4f3be8ecd0c6bcf294fd4.png","RB") $Cocfile=open ("Correct.png","WB")Panax Notoginseng #first Write -Correct=uncfile.read (0x6d) the Cocfile.write (correct) + Cocfile.flush () A  theCorrect=uncfile.read (0x4) #length + Cocfile.write (correct) - Cocfile.flush () $  $Uncorrect=uncfile.read (0x20000-0x1+0x4) -Crc=uncfile.read (0x4) -Crc=Binascii.hexlify (CRC) the Print CRC -Repair (Uncorrect,'\x0a', Cocfile,1, CRC) #1Wuyi #second Write theCorrect=uncfile.read (0x4) #length - Cocfile.write (correct) Wu Cocfile.flush () -Uncorrect=uncfile.read (0x20000-0x3+0x4) AboutCrc=uncfile.read (0x4) $Crc=Binascii.hexlify (CRC) - Print CRC -Repair (Uncorrect,'\x0a', Cocfile,3, CRC) #2 - #third Write ACorrect=uncfile.read (0x4) #length + Cocfile.write (correct) the Cocfile.flush () -Uncorrect=uncfile.read (0x20000-0x1+0x4) $Crc=uncfile.read (0x4) theCrc=Binascii.hexlify (CRC) the Print CRC theRepair (Uncorrect,'\x0a', Cocfile,1, CRC) #3 the #fourth Write -Correct=uncfile.read (0x4+0x4+0x20000+0x4) in Cocfile.write (correct) the Cocfile.flush () the #fifth Write AboutCorrect=uncfile.read (0x4) #length the Cocfile.write (correct) the Cocfile.flush () theUncorrect=uncfile.read (0x20000-0x3+0x4) +Crc=uncfile.read (0x4) -Crc=Binascii.hexlify (CRC) the Print CRCBayiRepair (Uncorrect,'\x0a', Cocfile,3, CRC) #4 the #6th theCorrect=uncfile.read (0x4) #length - Cocfile.write (correct) - Cocfile.flush () theUncorrect=uncfile.read (0x20000-0x1+0x4) theCrc=uncfile.read (0x4) theCrc=Binascii.hexlify (CRC) the Print CRC -Repair (Uncorrect,'\x0a', Cocfile,1, CRC) #5 the #7th theCorrect=uncfile.read (0x4) the Cocfile.write (correct)94 Cocfile.flush () theUncorrect=uncfile.read (0x20000-0x2+0x4) theCrc=uncfile.read (0x4) theCrc=Binascii.hexlify (CRC)98 Print CRC AboutRepair (Uncorrect,'\x0a', Cocfile,2, CRC) #6 - #8th101Correct=uncfile.read (0x4+0x4+0x20000+0x4)102 Cocfile.write (correct)103 Cocfile.flush ()104 #9th theCorrect=uncfile.read (0x4)106 Cocfile.write (correct)107 Cocfile.flush ()108Uncorrect=uncfile.read (0x20000-0x1+0x4)109Crc=uncfile.read (0x4) theCrc=Binascii.hexlify (CRC)111 Print CRC theRepair (Uncorrect,'\x0a', Cocfile,1, CRC) #7113 #10th theCorrect=uncfile.read (0x4+0x4+0x216f) the Cocfile.write (correct) the Cocfile.flush ()117 118 uncfile.close ()119Cocfile.close ()

　　

Results:

Reference documents:

http://blog.csdn.net/gogor/article/details/5265710

Http://www.libpng.org/pub/png/apps/pngcheck.html

Http://www.libpng.org/pub/png/book/chapter08.html

http://stackoverflow.com/questions/27238021/png-images-not-loaded

https://13c5.wordpress.com/2015/04/20/plaidctf-2015-png-uncorrupt/

plaidctf2015 uncorrupt png