502 lines
19 KiB
Perl
502 lines
19 KiB
Perl
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#------------------------------------------------------------------------------
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# File: AES.pm
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#
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# Description: AES encryption with cipher-block chaining
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#
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# Revisions: 2010/10/14 - P. Harvey Created
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#
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# References: 1) http://www.hoozi.com/Articles/AESEncryption.htm
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# 2) http://www.csrc.nist.gov/publications/fips/fips197/fips-197.pdf
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# 3) http://www.faqs.org/rfcs/rfc3602.html
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#------------------------------------------------------------------------------
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package Image::ExifTool::AES;
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use strict;
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use vars qw($VERSION @ISA @EXPORT_OK);
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require Exporter;
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$VERSION = '1.01';
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@ISA = qw(Exporter);
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@EXPORT_OK = qw(Crypt);
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my $seeded; # flag set if we already seeded random number generator
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my $nr; # number of rounds in AES cipher
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my @cbc; # cipher-block chaining bytes
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# arrays (all unsigned character) to hold intermediate results during encryption
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my @state = ([],[],[],[]); # the 2-dimensional state array
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my @RoundKey; # round keys
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my @sbox = (
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0x63, 0x7c, 0x77, 0x7b, 0xf2, 0x6b, 0x6f, 0xc5, 0x30, 0x01, 0x67, 0x2b, 0xfe, 0xd7, 0xab, 0x76,
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0xca, 0x82, 0xc9, 0x7d, 0xfa, 0x59, 0x47, 0xf0, 0xad, 0xd4, 0xa2, 0xaf, 0x9c, 0xa4, 0x72, 0xc0,
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0xb7, 0xfd, 0x93, 0x26, 0x36, 0x3f, 0xf7, 0xcc, 0x34, 0xa5, 0xe5, 0xf1, 0x71, 0xd8, 0x31, 0x15,
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0x04, 0xc7, 0x23, 0xc3, 0x18, 0x96, 0x05, 0x9a, 0x07, 0x12, 0x80, 0xe2, 0xeb, 0x27, 0xb2, 0x75,
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0x09, 0x83, 0x2c, 0x1a, 0x1b, 0x6e, 0x5a, 0xa0, 0x52, 0x3b, 0xd6, 0xb3, 0x29, 0xe3, 0x2f, 0x84,
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0x53, 0xd1, 0x00, 0xed, 0x20, 0xfc, 0xb1, 0x5b, 0x6a, 0xcb, 0xbe, 0x39, 0x4a, 0x4c, 0x58, 0xcf,
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0xd0, 0xef, 0xaa, 0xfb, 0x43, 0x4d, 0x33, 0x85, 0x45, 0xf9, 0x02, 0x7f, 0x50, 0x3c, 0x9f, 0xa8,
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0x51, 0xa3, 0x40, 0x8f, 0x92, 0x9d, 0x38, 0xf5, 0xbc, 0xb6, 0xda, 0x21, 0x10, 0xff, 0xf3, 0xd2,
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0xcd, 0x0c, 0x13, 0xec, 0x5f, 0x97, 0x44, 0x17, 0xc4, 0xa7, 0x7e, 0x3d, 0x64, 0x5d, 0x19, 0x73,
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0x60, 0x81, 0x4f, 0xdc, 0x22, 0x2a, 0x90, 0x88, 0x46, 0xee, 0xb8, 0x14, 0xde, 0x5e, 0x0b, 0xdb,
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0xe0, 0x32, 0x3a, 0x0a, 0x49, 0x06, 0x24, 0x5c, 0xc2, 0xd3, 0xac, 0x62, 0x91, 0x95, 0xe4, 0x79,
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0xe7, 0xc8, 0x37, 0x6d, 0x8d, 0xd5, 0x4e, 0xa9, 0x6c, 0x56, 0xf4, 0xea, 0x65, 0x7a, 0xae, 0x08,
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0xba, 0x78, 0x25, 0x2e, 0x1c, 0xa6, 0xb4, 0xc6, 0xe8, 0xdd, 0x74, 0x1f, 0x4b, 0xbd, 0x8b, 0x8a,
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0x70, 0x3e, 0xb5, 0x66, 0x48, 0x03, 0xf6, 0x0e, 0x61, 0x35, 0x57, 0xb9, 0x86, 0xc1, 0x1d, 0x9e,
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0xe1, 0xf8, 0x98, 0x11, 0x69, 0xd9, 0x8e, 0x94, 0x9b, 0x1e, 0x87, 0xe9, 0xce, 0x55, 0x28, 0xdf,
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0x8c, 0xa1, 0x89, 0x0d, 0xbf, 0xe6, 0x42, 0x68, 0x41, 0x99, 0x2d, 0x0f, 0xb0, 0x54, 0xbb, 0x16,
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);
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# reverse sbox
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my @rsbox = (
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0x52, 0x09, 0x6a, 0xd5, 0x30, 0x36, 0xa5, 0x38, 0xbf, 0x40, 0xa3, 0x9e, 0x81, 0xf3, 0xd7, 0xfb,
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0x7c, 0xe3, 0x39, 0x82, 0x9b, 0x2f, 0xff, 0x87, 0x34, 0x8e, 0x43, 0x44, 0xc4, 0xde, 0xe9, 0xcb,
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0x54, 0x7b, 0x94, 0x32, 0xa6, 0xc2, 0x23, 0x3d, 0xee, 0x4c, 0x95, 0x0b, 0x42, 0xfa, 0xc3, 0x4e,
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0x08, 0x2e, 0xa1, 0x66, 0x28, 0xd9, 0x24, 0xb2, 0x76, 0x5b, 0xa2, 0x49, 0x6d, 0x8b, 0xd1, 0x25,
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0x72, 0xf8, 0xf6, 0x64, 0x86, 0x68, 0x98, 0x16, 0xd4, 0xa4, 0x5c, 0xcc, 0x5d, 0x65, 0xb6, 0x92,
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0x6c, 0x70, 0x48, 0x50, 0xfd, 0xed, 0xb9, 0xda, 0x5e, 0x15, 0x46, 0x57, 0xa7, 0x8d, 0x9d, 0x84,
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0x90, 0xd8, 0xab, 0x00, 0x8c, 0xbc, 0xd3, 0x0a, 0xf7, 0xe4, 0x58, 0x05, 0xb8, 0xb3, 0x45, 0x06,
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0xd0, 0x2c, 0x1e, 0x8f, 0xca, 0x3f, 0x0f, 0x02, 0xc1, 0xaf, 0xbd, 0x03, 0x01, 0x13, 0x8a, 0x6b,
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0x3a, 0x91, 0x11, 0x41, 0x4f, 0x67, 0xdc, 0xea, 0x97, 0xf2, 0xcf, 0xce, 0xf0, 0xb4, 0xe6, 0x73,
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0x96, 0xac, 0x74, 0x22, 0xe7, 0xad, 0x35, 0x85, 0xe2, 0xf9, 0x37, 0xe8, 0x1c, 0x75, 0xdf, 0x6e,
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0x47, 0xf1, 0x1a, 0x71, 0x1d, 0x29, 0xc5, 0x89, 0x6f, 0xb7, 0x62, 0x0e, 0xaa, 0x18, 0xbe, 0x1b,
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0xfc, 0x56, 0x3e, 0x4b, 0xc6, 0xd2, 0x79, 0x20, 0x9a, 0xdb, 0xc0, 0xfe, 0x78, 0xcd, 0x5a, 0xf4,
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0x1f, 0xdd, 0xa8, 0x33, 0x88, 0x07, 0xc7, 0x31, 0xb1, 0x12, 0x10, 0x59, 0x27, 0x80, 0xec, 0x5f,
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0x60, 0x51, 0x7f, 0xa9, 0x19, 0xb5, 0x4a, 0x0d, 0x2d, 0xe5, 0x7a, 0x9f, 0x93, 0xc9, 0x9c, 0xef,
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0xa0, 0xe0, 0x3b, 0x4d, 0xae, 0x2a, 0xf5, 0xb0, 0xc8, 0xeb, 0xbb, 0x3c, 0x83, 0x53, 0x99, 0x61,
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0x17, 0x2b, 0x04, 0x7e, 0xba, 0x77, 0xd6, 0x26, 0xe1, 0x69, 0x14, 0x63, 0x55, 0x21, 0x0c, 0x7d,
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);
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# the round constant word array, $rcon[i], contains the values given by
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# x to the power (i-1) being powers of x (x is denoted as {02}) in the field GF(2^8)
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# Note that i starts at 1, not 0).
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my @rcon = (
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0x8d, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36, 0x6c, 0xd8, 0xab, 0x4d, 0x9a,
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0x2f, 0x5e, 0xbc, 0x63, 0xc6, 0x97, 0x35, 0x6a, 0xd4, 0xb3, 0x7d, 0xfa, 0xef, 0xc5, 0x91, 0x39,
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0x72, 0xe4, 0xd3, 0xbd, 0x61, 0xc2, 0x9f, 0x25, 0x4a, 0x94, 0x33, 0x66, 0xcc, 0x83, 0x1d, 0x3a,
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0x74, 0xe8, 0xcb, 0x8d, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36, 0x6c, 0xd8,
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0xab, 0x4d, 0x9a, 0x2f, 0x5e, 0xbc, 0x63, 0xc6, 0x97, 0x35, 0x6a, 0xd4, 0xb3, 0x7d, 0xfa, 0xef,
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0xc5, 0x91, 0x39, 0x72, 0xe4, 0xd3, 0xbd, 0x61, 0xc2, 0x9f, 0x25, 0x4a, 0x94, 0x33, 0x66, 0xcc,
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0x83, 0x1d, 0x3a, 0x74, 0xe8, 0xcb, 0x8d, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b,
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0x36, 0x6c, 0xd8, 0xab, 0x4d, 0x9a, 0x2f, 0x5e, 0xbc, 0x63, 0xc6, 0x97, 0x35, 0x6a, 0xd4, 0xb3,
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0x7d, 0xfa, 0xef, 0xc5, 0x91, 0x39, 0x72, 0xe4, 0xd3, 0xbd, 0x61, 0xc2, 0x9f, 0x25, 0x4a, 0x94,
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0x33, 0x66, 0xcc, 0x83, 0x1d, 0x3a, 0x74, 0xe8, 0xcb, 0x8d, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20,
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0x40, 0x80, 0x1b, 0x36, 0x6c, 0xd8, 0xab, 0x4d, 0x9a, 0x2f, 0x5e, 0xbc, 0x63, 0xc6, 0x97, 0x35,
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0x6a, 0xd4, 0xb3, 0x7d, 0xfa, 0xef, 0xc5, 0x91, 0x39, 0x72, 0xe4, 0xd3, 0xbd, 0x61, 0xc2, 0x9f,
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0x25, 0x4a, 0x94, 0x33, 0x66, 0xcc, 0x83, 0x1d, 0x3a, 0x74, 0xe8, 0xcb, 0x8d, 0x01, 0x02, 0x04,
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0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36, 0x6c, 0xd8, 0xab, 0x4d, 0x9a, 0x2f, 0x5e, 0xbc, 0x63,
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0xc6, 0x97, 0x35, 0x6a, 0xd4, 0xb3, 0x7d, 0xfa, 0xef, 0xc5, 0x91, 0x39, 0x72, 0xe4, 0xd3, 0xbd,
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0x61, 0xc2, 0x9f, 0x25, 0x4a, 0x94, 0x33, 0x66, 0xcc, 0x83, 0x1d, 0x3a, 0x74, 0xe8, 0xcb,
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);
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#------------------------------------------------------------------------------
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# This function produces 4*($nr+1) round keys.
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# The round keys are used in each round to encrypt the states.
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# Inputs: 0) key string (must be 16, 24 or 32 bytes long)
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sub KeyExpansion($)
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{
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my $key = shift;
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my @key = unpack 'C*', $key; # convert the key into a byte array
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my $nk = int(length($key) / 4); # number of 32-bit words in the key
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$nr = $nk + 6; # number of rounds
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# temporary variables (all unsigned characters)
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my ($i,@temp);
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# The first round key is the key itself.
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for ($i=0; $i<$nk; ++$i) {
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@RoundKey[$i*4..$i*4+3] = @key[$i*4..$i*4+3];
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}
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# All other round keys are found from the previous round keys.
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while ($i < (4 * ($nr+1))) {
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@temp[0..3] = @RoundKey[($i-1)*4..($i-1)*4+3];
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if ($i % $nk == 0) {
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# rotate the 4 bytes in a word to the left once
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# [a0,a1,a2,a3] becomes [a1,a2,a3,a0]
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@temp[0..3] = @temp[1,2,3,0];
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# take a four-byte input word and apply the S-box
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# to each of the four bytes to produce an output word.
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@temp[0..3] = @sbox[@temp[0..3]];
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$temp[0] = $temp[0] ^ $rcon[$i/$nk];
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} elsif ($nk > 6 && $i % $nk == 4) {
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@temp[0..3] = @sbox[@temp[0..3]];
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}
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$RoundKey[$i*4+0] = $RoundKey[($i-$nk)*4+0] ^ $temp[0];
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$RoundKey[$i*4+1] = $RoundKey[($i-$nk)*4+1] ^ $temp[1];
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$RoundKey[$i*4+2] = $RoundKey[($i-$nk)*4+2] ^ $temp[2];
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$RoundKey[$i*4+3] = $RoundKey[($i-$nk)*4+3] ^ $temp[3];
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++$i;
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}
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}
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#------------------------------------------------------------------------------
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# This function adds the round key to state.
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# The round key is added to the state by an XOR function.
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sub AddRoundKey($)
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{
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my $round = shift;
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my ($i,$j);
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for ($i=0; $i<4; ++$i) {
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my $k = $round*16 + $i*4;
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for ($j=0; $j<4; ++$j) {
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$state[$j][$i] ^= $RoundKey[$k + $j];
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}
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}
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}
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#------------------------------------------------------------------------------
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# Substitute the values in the state matrix with values in an S-box
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sub SubBytes()
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{
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my $i;
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for ($i=0; $i<4; ++$i) {
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@{$state[$i]}[0..3] = @sbox[@{$state[$i]}[0..3]];
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}
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}
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sub InvSubBytes()
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{
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my $i;
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for ($i=0; $i<4; ++$i) {
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@{$state[$i]}[0..3] = @rsbox[@{$state[$i]}[0..3]];
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}
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}
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#------------------------------------------------------------------------------
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# Shift the rows in the state to the left.
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# Each row is shifted with different offset.
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# Offset = Row number. So the first row is not shifted.
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sub ShiftRows()
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{
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# rotate first row 1 columns to left
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@{$state[1]}[0,1,2,3] = @{$state[1]}[1,2,3,0];
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# rotate second row 2 columns to left
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@{$state[2]}[0,1,2,3] = @{$state[2]}[2,3,0,1];
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# rotate third row 3 columns to left
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@{$state[3]}[0,1,2,3] = @{$state[3]}[3,0,1,2];
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}
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sub InvShiftRows()
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{
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# rotate first row 1 columns to right
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@{$state[1]}[0,1,2,3] = @{$state[1]}[3,0,1,2];
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# rotate second row 2 columns to right
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@{$state[2]}[0,1,2,3] = @{$state[2]}[2,3,0,1];
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# rotate third row 3 columns to right
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@{$state[3]}[0,1,2,3] = @{$state[3]}[1,2,3,0];
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}
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#------------------------------------------------------------------------------
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# Find the product of {02} and the argument to xtime modulo 0x1b
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# Note: returns an integer which may need to be trimmed to 8 bits
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sub xtime($)
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{
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return ($_[0]<<1) ^ ((($_[0]>>7) & 1) * 0x1b);
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}
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#------------------------------------------------------------------------------
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# Multiply numbers in the field GF(2^8)
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sub Mult($$)
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{
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my ($x, $y) = @_;
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return (($y & 1) * $x) ^
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(($y>>1 & 1) * xtime($x)) ^
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(($y>>2 & 1) * xtime(xtime($x))) ^
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(($y>>3 & 1) * xtime(xtime(xtime($x)))) ^
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(($y>>4 & 1) * xtime(xtime(xtime(xtime($x)))));
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}
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#------------------------------------------------------------------------------
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# Mix the columns of the state matrix
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sub MixColumns()
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{
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my ($i,$t0,$t1,$t2);
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for ($i=0; $i<4; ++$i) {
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$t0 = $state[0][$i];
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$t2 = $state[0][$i] ^ $state[1][$i] ^ $state[2][$i] ^ $state[3][$i];
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$t1 = $state[0][$i] ^ $state[1][$i] ; $t1 = xtime($t1) & 0xff; $state[0][$i] ^= $t1 ^ $t2 ;
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$t1 = $state[1][$i] ^ $state[2][$i] ; $t1 = xtime($t1) & 0xff; $state[1][$i] ^= $t1 ^ $t2 ;
|
||
|
|
$t1 = $state[2][$i] ^ $state[3][$i] ; $t1 = xtime($t1) & 0xff; $state[2][$i] ^= $t1 ^ $t2 ;
|
||
|
|
$t1 = $state[3][$i] ^ $t0 ; $t1 = xtime($t1) & 0xff; $state[3][$i] ^= $t1 ^ $t2 ;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
sub InvMixColumns()
|
||
|
|
{
|
||
|
|
my $i;
|
||
|
|
for ($i=0; $i<4; ++$i) {
|
||
|
|
my $a = $state[0][$i];
|
||
|
|
my $b = $state[1][$i];
|
||
|
|
my $c = $state[2][$i];
|
||
|
|
my $d = $state[3][$i];
|
||
|
|
$state[0][$i] = (Mult($a,0x0e) ^ Mult($b,0x0b) ^ Mult($c,0x0d) ^ Mult($d,0x09)) & 0xff;
|
||
|
|
$state[1][$i] = (Mult($a,0x09) ^ Mult($b,0x0e) ^ Mult($c,0x0b) ^ Mult($d,0x0d)) & 0xff;
|
||
|
|
$state[2][$i] = (Mult($a,0x0d) ^ Mult($b,0x09) ^ Mult($c,0x0e) ^ Mult($d,0x0b)) & 0xff;
|
||
|
|
$state[3][$i] = (Mult($a,0x0b) ^ Mult($b,0x0d) ^ Mult($c,0x09) ^ Mult($d,0x0e)) & 0xff;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
#------------------------------------------------------------------------------
|
||
|
|
# Encrypt (Cipher) or decrypt (InvCipher) a block of data with CBC
|
||
|
|
# Inputs: 0) string to cipher (must be 16 bytes long)
|
||
|
|
# Returns: cipher'd string
|
||
|
|
sub Cipher($)
|
||
|
|
{
|
||
|
|
my @in = unpack 'C*', $_[0]; # unpack input plaintext
|
||
|
|
my ($i, $j, $round);
|
||
|
|
|
||
|
|
# copy the input PlainText to state array and apply the CBC
|
||
|
|
for ($i=0; $i<4; ++$i) {
|
||
|
|
for ($j=0; $j<4; ++$j) {
|
||
|
|
my $k = $i*4 + $j;
|
||
|
|
$state[$j][$i] = $in[$k] ^ $cbc[$k];
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
# add the First round key to the state before starting the rounds
|
||
|
|
AddRoundKey(0);
|
||
|
|
|
||
|
|
# there will be $nr rounds; the first $nr-1 rounds are identical
|
||
|
|
for ($round=1; ; ++$round) {
|
||
|
|
SubBytes();
|
||
|
|
ShiftRows();
|
||
|
|
if ($round < $nr) {
|
||
|
|
MixColumns();
|
||
|
|
AddRoundKey($round);
|
||
|
|
} else {
|
||
|
|
# MixColumns() is not used in the last round
|
||
|
|
AddRoundKey($nr);
|
||
|
|
last;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
# the encryption process is over
|
||
|
|
# copy the state array to output array (and save for CBC)
|
||
|
|
for ($i=0; $i<4; ++$i) {
|
||
|
|
for ($j=0; $j<4; ++$j) {
|
||
|
|
$cbc[$i*4+$j] = $state[$j][$i];
|
||
|
|
}
|
||
|
|
}
|
||
|
|
return pack 'C*', @cbc; # return packed ciphertext
|
||
|
|
}
|
||
|
|
|
||
|
|
sub InvCipher($)
|
||
|
|
{
|
||
|
|
my @in = unpack 'C*', $_[0]; # unpack input ciphertext
|
||
|
|
my (@out, $i, $j, $round);
|
||
|
|
|
||
|
|
# copy the input CipherText to state array
|
||
|
|
for ($i=0; $i<4; ++$i) {
|
||
|
|
for ($j=0; $j<4; ++$j) {
|
||
|
|
$state[$j][$i] = $in[$i*4 + $j];
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
# add the First round key to the state before starting the rounds
|
||
|
|
AddRoundKey($nr);
|
||
|
|
|
||
|
|
# there will be $nr rounds; the first $nr-1 rounds are identical
|
||
|
|
for ($round=$nr-1; ; --$round) {
|
||
|
|
InvShiftRows();
|
||
|
|
InvSubBytes();
|
||
|
|
AddRoundKey($round);
|
||
|
|
# InvMixColumns() is not used in the last round
|
||
|
|
last if $round <= 0;
|
||
|
|
InvMixColumns();
|
||
|
|
}
|
||
|
|
|
||
|
|
# copy the state array to output array and reverse the CBC
|
||
|
|
for ($i=0; $i<4; ++$i) {
|
||
|
|
for ($j=0; $j<4; ++$j) {
|
||
|
|
my $k = $i*4 + $j;
|
||
|
|
$out[$k] = $state[$j][$i] ^ $cbc[$k];
|
||
|
|
}
|
||
|
|
}
|
||
|
|
@cbc = @in; # update CBC for next block
|
||
|
|
return pack 'C*', @out; # return packed plaintext
|
||
|
|
}
|
||
|
|
|
||
|
|
#------------------------------------------------------------------------------
|
||
|
|
# Encrypt/Decrypt using AES-CBC algorithm (with fixed 16-byte blocks)
|
||
|
|
# Inputs: 0) data reference (with leading 16-byte initialization vector when decrypting)
|
||
|
|
# 1) encryption key (16, 24 or 32 bytes for AES-128, AES-192 or AES-256)
|
||
|
|
# 2) encrypt flag (false for decryption, true with length 16 bytes to
|
||
|
|
# encrypt using this as the CBC IV, or true with other length to
|
||
|
|
# encrypt with a randomly-generated IV)
|
||
|
|
# 3) flag to disable padding
|
||
|
|
# Returns: error string, or undef on success
|
||
|
|
# Notes: encrypts/decrypts data in place (encrypted data returned with leading IV)
|
||
|
|
sub Crypt($$;$$)
|
||
|
|
{
|
||
|
|
my ($dataPt, $key, $encrypt, $noPad) = @_;
|
||
|
|
|
||
|
|
# validate key length
|
||
|
|
my $keyLen = length $key;
|
||
|
|
unless ($keyLen == 16 or $keyLen == 24 or $keyLen == 32) {
|
||
|
|
return "Invalid AES key length ($keyLen)";
|
||
|
|
}
|
||
|
|
my $partLen = length($$dataPt) % 16;
|
||
|
|
my ($pos, $i);
|
||
|
|
if ($encrypt) {
|
||
|
|
if (length($encrypt) == 16) {
|
||
|
|
@cbc = unpack 'C*', $encrypt;
|
||
|
|
} else {
|
||
|
|
# generate a random 16-byte CBC initialization vector
|
||
|
|
unless ($seeded) {
|
||
|
|
srand(time() & ($$ + ($$<<15)));
|
||
|
|
$seeded = 1;
|
||
|
|
}
|
||
|
|
for ($i=0; $i<16; ++$i) {
|
||
|
|
$cbc[$i] = int(rand(256));
|
||
|
|
}
|
||
|
|
$encrypt = pack 'C*', @cbc;
|
||
|
|
}
|
||
|
|
$$dataPt = $encrypt . $$dataPt; # add IV to the start of the data
|
||
|
|
# add required padding so we can recover the
|
||
|
|
# original string length after decryption
|
||
|
|
# (padding bytes have value set to padding length)
|
||
|
|
my $padLen = 16 - $partLen;
|
||
|
|
$$dataPt .= (chr($padLen)) x $padLen unless $padLen == 16 and $noPad;
|
||
|
|
$pos = 16; # start encrypting at byte 16 (after the IV)
|
||
|
|
} elsif ($partLen) {
|
||
|
|
return 'Invalid AES ciphertext length';
|
||
|
|
} elsif (length $$dataPt >= 32) {
|
||
|
|
# take the CBC initialization vector from the start of the data
|
||
|
|
@cbc = unpack 'C16', $$dataPt;
|
||
|
|
$$dataPt = substr($$dataPt, 16);
|
||
|
|
$pos = 0; # start decrypting from byte 0 (now that IV is removed)
|
||
|
|
} else {
|
||
|
|
$$dataPt = ''; # empty text
|
||
|
|
return undef;
|
||
|
|
}
|
||
|
|
# the KeyExpansion routine must be called before encryption
|
||
|
|
KeyExpansion($key);
|
||
|
|
|
||
|
|
# loop through the data and convert in blocks
|
||
|
|
my $dataLen = length $$dataPt;
|
||
|
|
my $last = $dataLen - 16;
|
||
|
|
my $func = $encrypt ? \&Cipher : \&InvCipher;
|
||
|
|
while ($pos <= $last) {
|
||
|
|
# cipher this block
|
||
|
|
substr($$dataPt, $pos, 16) = &$func(substr($$dataPt, $pos, 16));
|
||
|
|
$pos += 16;
|
||
|
|
}
|
||
|
|
unless ($encrypt or $noPad) {
|
||
|
|
# remove padding if necessary (padding byte value gives length of padding)
|
||
|
|
my $padLen = ord(substr($$dataPt, -1, 1));
|
||
|
|
return 'AES decryption error (invalid pad byte)' if $padLen > 16;
|
||
|
|
$$dataPt = substr($$dataPt, 0, $dataLen - $padLen);
|
||
|
|
}
|
||
|
|
return undef;
|
||
|
|
}
|
||
|
|
|
||
|
|
1; # end
|
||
|
|
|
||
|
|
|
||
|
|
__END__
|
||
|
|
|
||
|
|
=head1 NAME
|
||
|
|
|
||
|
|
Image::ExifTool::AES - AES encryption with cipher-block chaining
|
||
|
|
|
||
|
|
=head1 SYNOPSIS
|
||
|
|
|
||
|
|
use Image::ExifTool::AES qw(Crypt);
|
||
|
|
|
||
|
|
$err = Crypt(\$plaintext, $key, 1); # encryption
|
||
|
|
|
||
|
|
$err = Crypt(\$ciphertext, $key); # decryption
|
||
|
|
|
||
|
|
=head1 DESCRIPTION
|
||
|
|
|
||
|
|
This module contains an implementation of the AES encryption/decryption
|
||
|
|
algorithms with cipher-block chaining (CBC) and RFC 2898 PKCS #5 padding.
|
||
|
|
This is the AESV2 and AESV3 encryption mode used in PDF documents.
|
||
|
|
|
||
|
|
=head1 EXPORTS
|
||
|
|
|
||
|
|
Exports nothing by default, but L</Crypt> may be exported.
|
||
|
|
|
||
|
|
=head1 METHODS
|
||
|
|
|
||
|
|
=head2 Crypt
|
||
|
|
|
||
|
|
Implement AES encryption/decryption with cipher-block chaining.
|
||
|
|
|
||
|
|
=over 4
|
||
|
|
|
||
|
|
=item Inputs:
|
||
|
|
|
||
|
|
0) Scalar reference for data to encrypt/decrypt.
|
||
|
|
|
||
|
|
1) Encryption key string (must have length 16, 24 or 32).
|
||
|
|
|
||
|
|
2) [optional] Encrypt flag (false to decrypt).
|
||
|
|
|
||
|
|
3) [optional] Flag to avoid removing padding after decrypting, or to avoid
|
||
|
|
adding 16 bytes of padding before encrypting when data length is already a
|
||
|
|
multiple of 16 bytes.
|
||
|
|
|
||
|
|
=item Returns:
|
||
|
|
|
||
|
|
On success, the return value is undefined and the data is encrypted or
|
||
|
|
decrypted as specified. Otherwise returns an error string and the data is
|
||
|
|
left in an indeterminate state.
|
||
|
|
|
||
|
|
=item Notes:
|
||
|
|
|
||
|
|
The length of the encryption key dictates the AES mode, with lengths of 16,
|
||
|
|
24 and 32 bytes resulting in AES-128, AES-192 and AES-256.
|
||
|
|
|
||
|
|
When encrypting, the input data may be any length and will be padded to an
|
||
|
|
even 16-byte block size using the specified padding technique. If the
|
||
|
|
encrypt flag has length 16, it is used as the initialization vector for
|
||
|
|
the cipher-block chaining, otherwise a random IV is generated. Upon
|
||
|
|
successful return the data will be encrypted, with the first 16 bytes of
|
||
|
|
the data being the CBC IV.
|
||
|
|
|
||
|
|
When decrypting, the input data begins with the 16-byte CBC initialization
|
||
|
|
vector.
|
||
|
|
|
||
|
|
=back
|
||
|
|
|
||
|
|
=head1 BUGS
|
||
|
|
|
||
|
|
This code is blindingly slow. But in truth, slowing down processing is the
|
||
|
|
main purpose of encryption, so this really can't be considered a bug.
|
||
|
|
|
||
|
|
=head1 AUTHOR
|
||
|
|
|
||
|
|
Copyright 2003-2016, Phil Harvey (phil at owl.phy.queensu.ca)
|
||
|
|
|
||
|
|
This library is free software; you can redistribute it and/or modify it
|
||
|
|
under the same terms as Perl itself.
|
||
|
|
|
||
|
|
=head1 REFERENCES
|
||
|
|
|
||
|
|
=over 4
|
||
|
|
|
||
|
|
=item L<http://www.hoozi.com/Articles/AESEncryption.htm>
|
||
|
|
|
||
|
|
=item L<http://www.csrc.nist.gov/publications/fips/fips197/fips-197.pdf>
|
||
|
|
|
||
|
|
=item L<http://www.faqs.org/rfcs/rfc3602.html>
|
||
|
|
|
||
|
|
=back
|
||
|
|
|
||
|
|
=head1 SEE ALSO
|
||
|
|
|
||
|
|
L<Image::ExifTool(3pm)|Image::ExifTool>
|
||
|
|
|
||
|
|
=cut
|