File Coverage

blib/lib/Image/ExifTool/AES.pm
Criterion Covered Total %
statement 97 162 59.8
branch 14 28 50.0
condition 9 15 60.0
subroutine 11 15 73.3
pod 1 13 7.6
total 132 233 56.6


line stmt bran cond sub pod time code
1             #------------------------------------------------------------------------------
2             # File: AES.pm
3             #
4             # Description: AES encryption with cipher-block chaining
5             #
6             # Revisions: 2010/10/14 - P. Harvey Created
7             #
8             # References: 1) http://www.hoozi.com/Articles/AESEncryption.htm
9             # 2) http://www.csrc.nist.gov/publications/fips/fips197/fips-197.pdf
10             # 3) http://www.faqs.org/rfcs/rfc3602.html
11             #------------------------------------------------------------------------------
12              
13             package Image::ExifTool::AES;
14              
15 1     1   548 use strict;
  1         2  
  1         64  
16 1     1   7 use vars qw($VERSION @ISA @EXPORT_OK);
  1         2  
  1         2016  
17             require Exporter;
18              
19             $VERSION = '1.01';
20             @ISA = qw(Exporter);
21             @EXPORT_OK = qw(Crypt);
22              
23             my $seeded; # flag set if we already seeded random number generator
24             my $nr; # number of rounds in AES cipher
25             my @cbc; # cipher-block chaining bytes
26              
27             # arrays (all unsigned character) to hold intermediate results during encryption
28             my @state = ([],[],[],[]); # the 2-dimensional state array
29             my @RoundKey; # round keys
30              
31             my @sbox = (
32             0x63, 0x7c, 0x77, 0x7b, 0xf2, 0x6b, 0x6f, 0xc5, 0x30, 0x01, 0x67, 0x2b, 0xfe, 0xd7, 0xab, 0x76,
33             0xca, 0x82, 0xc9, 0x7d, 0xfa, 0x59, 0x47, 0xf0, 0xad, 0xd4, 0xa2, 0xaf, 0x9c, 0xa4, 0x72, 0xc0,
34             0xb7, 0xfd, 0x93, 0x26, 0x36, 0x3f, 0xf7, 0xcc, 0x34, 0xa5, 0xe5, 0xf1, 0x71, 0xd8, 0x31, 0x15,
35             0x04, 0xc7, 0x23, 0xc3, 0x18, 0x96, 0x05, 0x9a, 0x07, 0x12, 0x80, 0xe2, 0xeb, 0x27, 0xb2, 0x75,
36             0x09, 0x83, 0x2c, 0x1a, 0x1b, 0x6e, 0x5a, 0xa0, 0x52, 0x3b, 0xd6, 0xb3, 0x29, 0xe3, 0x2f, 0x84,
37             0x53, 0xd1, 0x00, 0xed, 0x20, 0xfc, 0xb1, 0x5b, 0x6a, 0xcb, 0xbe, 0x39, 0x4a, 0x4c, 0x58, 0xcf,
38             0xd0, 0xef, 0xaa, 0xfb, 0x43, 0x4d, 0x33, 0x85, 0x45, 0xf9, 0x02, 0x7f, 0x50, 0x3c, 0x9f, 0xa8,
39             0x51, 0xa3, 0x40, 0x8f, 0x92, 0x9d, 0x38, 0xf5, 0xbc, 0xb6, 0xda, 0x21, 0x10, 0xff, 0xf3, 0xd2,
40             0xcd, 0x0c, 0x13, 0xec, 0x5f, 0x97, 0x44, 0x17, 0xc4, 0xa7, 0x7e, 0x3d, 0x64, 0x5d, 0x19, 0x73,
41             0x60, 0x81, 0x4f, 0xdc, 0x22, 0x2a, 0x90, 0x88, 0x46, 0xee, 0xb8, 0x14, 0xde, 0x5e, 0x0b, 0xdb,
42             0xe0, 0x32, 0x3a, 0x0a, 0x49, 0x06, 0x24, 0x5c, 0xc2, 0xd3, 0xac, 0x62, 0x91, 0x95, 0xe4, 0x79,
43             0xe7, 0xc8, 0x37, 0x6d, 0x8d, 0xd5, 0x4e, 0xa9, 0x6c, 0x56, 0xf4, 0xea, 0x65, 0x7a, 0xae, 0x08,
44             0xba, 0x78, 0x25, 0x2e, 0x1c, 0xa6, 0xb4, 0xc6, 0xe8, 0xdd, 0x74, 0x1f, 0x4b, 0xbd, 0x8b, 0x8a,
45             0x70, 0x3e, 0xb5, 0x66, 0x48, 0x03, 0xf6, 0x0e, 0x61, 0x35, 0x57, 0xb9, 0x86, 0xc1, 0x1d, 0x9e,
46             0xe1, 0xf8, 0x98, 0x11, 0x69, 0xd9, 0x8e, 0x94, 0x9b, 0x1e, 0x87, 0xe9, 0xce, 0x55, 0x28, 0xdf,
47             0x8c, 0xa1, 0x89, 0x0d, 0xbf, 0xe6, 0x42, 0x68, 0x41, 0x99, 0x2d, 0x0f, 0xb0, 0x54, 0xbb, 0x16,
48             );
49              
50             # reverse sbox
51             my @rsbox = (
52             0x52, 0x09, 0x6a, 0xd5, 0x30, 0x36, 0xa5, 0x38, 0xbf, 0x40, 0xa3, 0x9e, 0x81, 0xf3, 0xd7, 0xfb,
53             0x7c, 0xe3, 0x39, 0x82, 0x9b, 0x2f, 0xff, 0x87, 0x34, 0x8e, 0x43, 0x44, 0xc4, 0xde, 0xe9, 0xcb,
54             0x54, 0x7b, 0x94, 0x32, 0xa6, 0xc2, 0x23, 0x3d, 0xee, 0x4c, 0x95, 0x0b, 0x42, 0xfa, 0xc3, 0x4e,
55             0x08, 0x2e, 0xa1, 0x66, 0x28, 0xd9, 0x24, 0xb2, 0x76, 0x5b, 0xa2, 0x49, 0x6d, 0x8b, 0xd1, 0x25,
56             0x72, 0xf8, 0xf6, 0x64, 0x86, 0x68, 0x98, 0x16, 0xd4, 0xa4, 0x5c, 0xcc, 0x5d, 0x65, 0xb6, 0x92,
57             0x6c, 0x70, 0x48, 0x50, 0xfd, 0xed, 0xb9, 0xda, 0x5e, 0x15, 0x46, 0x57, 0xa7, 0x8d, 0x9d, 0x84,
58             0x90, 0xd8, 0xab, 0x00, 0x8c, 0xbc, 0xd3, 0x0a, 0xf7, 0xe4, 0x58, 0x05, 0xb8, 0xb3, 0x45, 0x06,
59             0xd0, 0x2c, 0x1e, 0x8f, 0xca, 0x3f, 0x0f, 0x02, 0xc1, 0xaf, 0xbd, 0x03, 0x01, 0x13, 0x8a, 0x6b,
60             0x3a, 0x91, 0x11, 0x41, 0x4f, 0x67, 0xdc, 0xea, 0x97, 0xf2, 0xcf, 0xce, 0xf0, 0xb4, 0xe6, 0x73,
61             0x96, 0xac, 0x74, 0x22, 0xe7, 0xad, 0x35, 0x85, 0xe2, 0xf9, 0x37, 0xe8, 0x1c, 0x75, 0xdf, 0x6e,
62             0x47, 0xf1, 0x1a, 0x71, 0x1d, 0x29, 0xc5, 0x89, 0x6f, 0xb7, 0x62, 0x0e, 0xaa, 0x18, 0xbe, 0x1b,
63             0xfc, 0x56, 0x3e, 0x4b, 0xc6, 0xd2, 0x79, 0x20, 0x9a, 0xdb, 0xc0, 0xfe, 0x78, 0xcd, 0x5a, 0xf4,
64             0x1f, 0xdd, 0xa8, 0x33, 0x88, 0x07, 0xc7, 0x31, 0xb1, 0x12, 0x10, 0x59, 0x27, 0x80, 0xec, 0x5f,
65             0x60, 0x51, 0x7f, 0xa9, 0x19, 0xb5, 0x4a, 0x0d, 0x2d, 0xe5, 0x7a, 0x9f, 0x93, 0xc9, 0x9c, 0xef,
66             0xa0, 0xe0, 0x3b, 0x4d, 0xae, 0x2a, 0xf5, 0xb0, 0xc8, 0xeb, 0xbb, 0x3c, 0x83, 0x53, 0x99, 0x61,
67             0x17, 0x2b, 0x04, 0x7e, 0xba, 0x77, 0xd6, 0x26, 0xe1, 0x69, 0x14, 0x63, 0x55, 0x21, 0x0c, 0x7d,
68             );
69              
70             # the round constant word array, $rcon[i], contains the values given by
71             # x to the power (i-1) being powers of x (x is denoted as {02}) in the field GF(2^8)
72             # Note that i starts at 1, not 0).
73             my @rcon = (
74             0x8d, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36, 0x6c, 0xd8, 0xab, 0x4d, 0x9a,
75             0x2f, 0x5e, 0xbc, 0x63, 0xc6, 0x97, 0x35, 0x6a, 0xd4, 0xb3, 0x7d, 0xfa, 0xef, 0xc5, 0x91, 0x39,
76             0x72, 0xe4, 0xd3, 0xbd, 0x61, 0xc2, 0x9f, 0x25, 0x4a, 0x94, 0x33, 0x66, 0xcc, 0x83, 0x1d, 0x3a,
77             0x74, 0xe8, 0xcb, 0x8d, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36, 0x6c, 0xd8,
78             0xab, 0x4d, 0x9a, 0x2f, 0x5e, 0xbc, 0x63, 0xc6, 0x97, 0x35, 0x6a, 0xd4, 0xb3, 0x7d, 0xfa, 0xef,
79             0xc5, 0x91, 0x39, 0x72, 0xe4, 0xd3, 0xbd, 0x61, 0xc2, 0x9f, 0x25, 0x4a, 0x94, 0x33, 0x66, 0xcc,
80             0x83, 0x1d, 0x3a, 0x74, 0xe8, 0xcb, 0x8d, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b,
81             0x36, 0x6c, 0xd8, 0xab, 0x4d, 0x9a, 0x2f, 0x5e, 0xbc, 0x63, 0xc6, 0x97, 0x35, 0x6a, 0xd4, 0xb3,
82             0x7d, 0xfa, 0xef, 0xc5, 0x91, 0x39, 0x72, 0xe4, 0xd3, 0xbd, 0x61, 0xc2, 0x9f, 0x25, 0x4a, 0x94,
83             0x33, 0x66, 0xcc, 0x83, 0x1d, 0x3a, 0x74, 0xe8, 0xcb, 0x8d, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20,
84             0x40, 0x80, 0x1b, 0x36, 0x6c, 0xd8, 0xab, 0x4d, 0x9a, 0x2f, 0x5e, 0xbc, 0x63, 0xc6, 0x97, 0x35,
85             0x6a, 0xd4, 0xb3, 0x7d, 0xfa, 0xef, 0xc5, 0x91, 0x39, 0x72, 0xe4, 0xd3, 0xbd, 0x61, 0xc2, 0x9f,
86             0x25, 0x4a, 0x94, 0x33, 0x66, 0xcc, 0x83, 0x1d, 0x3a, 0x74, 0xe8, 0xcb, 0x8d, 0x01, 0x02, 0x04,
87             0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36, 0x6c, 0xd8, 0xab, 0x4d, 0x9a, 0x2f, 0x5e, 0xbc, 0x63,
88             0xc6, 0x97, 0x35, 0x6a, 0xd4, 0xb3, 0x7d, 0xfa, 0xef, 0xc5, 0x91, 0x39, 0x72, 0xe4, 0xd3, 0xbd,
89             0x61, 0xc2, 0x9f, 0x25, 0x4a, 0x94, 0x33, 0x66, 0xcc, 0x83, 0x1d, 0x3a, 0x74, 0xe8, 0xcb,
90             );
91              
92             #------------------------------------------------------------------------------
93             # This function produces 4*($nr+1) round keys.
94             # The round keys are used in each round to encrypt the states.
95             # Inputs: 0) key string (must be 16, 24 or 32 bytes long)
96             sub KeyExpansion($)
97             {
98 6     6 0 10 my $key = shift;
99 6         16 my @key = unpack 'C*', $key; # convert the key into a byte array
100 6         16 my $nk = int(length($key) / 4); # number of 32-bit words in the key
101 6         7 $nr = $nk + 6; # number of rounds
102              
103             # temporary variables (all unsigned characters)
104 6         10 my ($i,@temp);
105              
106             # The first round key is the key itself.
107 6         13 for ($i=0; $i<$nk; ++$i) {
108 44         130 @RoundKey[$i*4..$i*4+3] = @key[$i*4..$i*4+3];
109             }
110             # All other round keys are found from the previous round keys.
111 6         13 while ($i < (4 * ($nr+1))) {
112              
113 300         495 @temp[0..3] = @RoundKey[($i-1)*4..($i-1)*4+3];
114              
115 300 100 100     720 if ($i % $nk == 0) {
    100          
116             # rotate the 4 bytes in a word to the left once
117             # [a0,a1,a2,a3] becomes [a1,a2,a3,a0]
118 45         65 @temp[0..3] = @temp[1,2,3,0];
119              
120             # take a four-byte input word and apply the S-box
121             # to each of the four bytes to produce an output word.
122 45         65 @temp[0..3] = @sbox[@temp[0..3]];
123              
124 45         70 $temp[0] = $temp[0] ^ $rcon[$i/$nk];
125              
126             } elsif ($nk > 6 && $i % $nk == 4) {
127              
128 30         47 @temp[0..3] = @sbox[@temp[0..3]];
129             }
130 300         419 $RoundKey[$i*4+0] = $RoundKey[($i-$nk)*4+0] ^ $temp[0];
131 300         380 $RoundKey[$i*4+1] = $RoundKey[($i-$nk)*4+1] ^ $temp[1];
132 300         389 $RoundKey[$i*4+2] = $RoundKey[($i-$nk)*4+2] ^ $temp[2];
133 300         368 $RoundKey[$i*4+3] = $RoundKey[($i-$nk)*4+3] ^ $temp[3];
134 300         456 ++$i;
135             }
136             }
137              
138             #------------------------------------------------------------------------------
139             # This function adds the round key to state.
140             # The round key is added to the state by an XOR function.
141             sub AddRoundKey($)
142             {
143 131     131 0 156 my $round = shift;
144 131         156 my ($i,$j);
145 131         217 for ($i=0; $i<4; ++$i) {
146 524         596 my $k = $round*16 + $i*4;
147 524         759 for ($j=0; $j<4; ++$j) {
148 2096         3194 $state[$j][$i] ^= $RoundKey[$k + $j];
149             }
150             }
151             }
152              
153             #------------------------------------------------------------------------------
154             # Substitute the values in the state matrix with values in an S-box
155             sub SubBytes()
156             {
157 0     0 0 0 my $i;
158 0         0 for ($i=0; $i<4; ++$i) {
159 0         0 @{$state[$i]}[0..3] = @sbox[@{$state[$i]}[0..3]];
  0         0  
  0         0  
160             }
161             }
162              
163             sub InvSubBytes()
164             {
165 122     122 0 131 my $i;
166 122         200 for ($i=0; $i<4; ++$i) {
167 488         510 @{$state[$i]}[0..3] = @rsbox[@{$state[$i]}[0..3]];
  488         793  
  488         590  
168             }
169             }
170              
171             #------------------------------------------------------------------------------
172             # Shift the rows in the state to the left.
173             # Each row is shifted with different offset.
174             # Offset = Row number. So the first row is not shifted.
175             sub ShiftRows()
176             {
177             # rotate first row 1 columns to left
178 0     0 0 0 @{$state[1]}[0,1,2,3] = @{$state[1]}[1,2,3,0];
  0         0  
  0         0  
179              
180             # rotate second row 2 columns to left
181 0         0 @{$state[2]}[0,1,2,3] = @{$state[2]}[2,3,0,1];
  0         0  
  0         0  
182              
183             # rotate third row 3 columns to left
184 0         0 @{$state[3]}[0,1,2,3] = @{$state[3]}[3,0,1,2];
  0         0  
  0         0  
185             }
186              
187             sub InvShiftRows()
188             {
189             # rotate first row 1 columns to right
190 122     122 0 149 @{$state[1]}[0,1,2,3] = @{$state[1]}[3,0,1,2];
  122         189  
  122         176  
191              
192             # rotate second row 2 columns to right
193 122         147 @{$state[2]}[0,1,2,3] = @{$state[2]}[2,3,0,1];
  122         154  
  122         150  
194              
195             # rotate third row 3 columns to right
196 122         147 @{$state[3]}[0,1,2,3] = @{$state[3]}[1,2,3,0];
  122         160  
  122         157  
197             }
198              
199             #------------------------------------------------------------------------------
200             # Find the product of {02} and the argument to xtime modulo 0x1b
201             # Note: returns an integer which may need to be trimmed to 8 bits
202             sub xtime($)
203             {
204 72320     72320 0 97376 return ($_[0]<<1) ^ ((($_[0]>>7) & 1) * 0x1b);
205             }
206              
207             #------------------------------------------------------------------------------
208             # Multiply numbers in the field GF(2^8)
209             sub Mult($$)
210             {
211 7232     7232 0 8937 my ($x, $y) = @_;
212 7232         9389 return (($y & 1) * $x) ^
213             (($y>>1 & 1) * xtime($x)) ^
214             (($y>>2 & 1) * xtime(xtime($x))) ^
215             (($y>>3 & 1) * xtime(xtime(xtime($x)))) ^
216             (($y>>4 & 1) * xtime(xtime(xtime(xtime($x)))));
217             }
218              
219             #------------------------------------------------------------------------------
220             # Mix the columns of the state matrix
221             sub MixColumns()
222             {
223 0     0 0 0 my ($i,$t0,$t1,$t2);
224 0         0 for ($i=0; $i<4; ++$i) {
225 0         0 $t0 = $state[0][$i];
226 0         0 $t2 = $state[0][$i] ^ $state[1][$i] ^ $state[2][$i] ^ $state[3][$i];
227 0         0 $t1 = $state[0][$i] ^ $state[1][$i] ; $t1 = xtime($t1) & 0xff; $state[0][$i] ^= $t1 ^ $t2 ;
  0         0  
  0         0  
228 0         0 $t1 = $state[1][$i] ^ $state[2][$i] ; $t1 = xtime($t1) & 0xff; $state[1][$i] ^= $t1 ^ $t2 ;
  0         0  
  0         0  
229 0         0 $t1 = $state[2][$i] ^ $state[3][$i] ; $t1 = xtime($t1) & 0xff; $state[2][$i] ^= $t1 ^ $t2 ;
  0         0  
  0         0  
230 0         0 $t1 = $state[3][$i] ^ $t0 ; $t1 = xtime($t1) & 0xff; $state[3][$i] ^= $t1 ^ $t2 ;
  0         0  
  0         0  
231             }
232             }
233              
234             sub InvMixColumns()
235             {
236 113     113 0 121 my $i;
237 113         161 for ($i=0; $i<4; ++$i) {
238 452         552 my $a = $state[0][$i];
239 452         472 my $b = $state[1][$i];
240 452         494 my $c = $state[2][$i];
241 452         484 my $d = $state[3][$i];
242 452         539 $state[0][$i] = (Mult($a,0x0e) ^ Mult($b,0x0b) ^ Mult($c,0x0d) ^ Mult($d,0x09)) & 0xff;
243 452         774 $state[1][$i] = (Mult($a,0x09) ^ Mult($b,0x0e) ^ Mult($c,0x0b) ^ Mult($d,0x0d)) & 0xff;
244 452         765 $state[2][$i] = (Mult($a,0x0d) ^ Mult($b,0x09) ^ Mult($c,0x0e) ^ Mult($d,0x0b)) & 0xff;
245 452         771 $state[3][$i] = (Mult($a,0x0b) ^ Mult($b,0x0d) ^ Mult($c,0x09) ^ Mult($d,0x0e)) & 0xff;
246             }
247             }
248              
249             #------------------------------------------------------------------------------
250             # Encrypt (Cipher) or decrypt (InvCipher) a block of data with CBC
251             # Inputs: 0) string to cipher (must be 16 bytes long)
252             # Returns: cipher'd string
253             sub Cipher($)
254             {
255 0     0 0 0 my @in = unpack 'C*', $_[0]; # unpack input plaintext
256 0         0 my ($i, $j, $round);
257              
258             # copy the input PlainText to state array and apply the CBC
259 0         0 for ($i=0; $i<4; ++$i) {
260 0         0 for ($j=0; $j<4; ++$j) {
261 0         0 my $k = $i*4 + $j;
262 0         0 $state[$j][$i] = $in[$k] ^ $cbc[$k];
263             }
264             }
265              
266             # add the First round key to the state before starting the rounds
267 0         0 AddRoundKey(0);
268              
269             # there will be $nr rounds; the first $nr-1 rounds are identical
270 0         0 for ($round=1; ; ++$round) {
271 0         0 SubBytes();
272 0         0 ShiftRows();
273 0 0       0 if ($round < $nr) {
274 0         0 MixColumns();
275 0         0 AddRoundKey($round);
276             } else {
277             # MixColumns() is not used in the last round
278 0         0 AddRoundKey($nr);
279 0         0 last;
280             }
281             }
282              
283             # the encryption process is over
284             # copy the state array to output array (and save for CBC)
285 0         0 for ($i=0; $i<4; ++$i) {
286 0         0 for ($j=0; $j<4; ++$j) {
287 0         0 $cbc[$i*4+$j] = $state[$j][$i];
288             }
289             }
290 0         0 return pack 'C*', @cbc; # return packed ciphertext
291             }
292              
293             sub InvCipher($)
294             {
295 9     9 0 32 my @in = unpack 'C*', $_[0]; # unpack input ciphertext
296 9         16 my (@out, $i, $j, $round);
297              
298             # copy the input CipherText to state array
299 9         19 for ($i=0; $i<4; ++$i) {
300 36         56 for ($j=0; $j<4; ++$j) {
301 144         231 $state[$j][$i] = $in[$i*4 + $j];
302             }
303             }
304              
305             # add the First round key to the state before starting the rounds
306 9         29 AddRoundKey($nr);
307              
308             # there will be $nr rounds; the first $nr-1 rounds are identical
309 9         16 for ($round=$nr-1; ; --$round) {
310 122         235 InvShiftRows();
311 122         214 InvSubBytes();
312 122         218 AddRoundKey($round);
313             # InvMixColumns() is not used in the last round
314 122 100       190 last if $round <= 0;
315 113         150 InvMixColumns();
316             }
317              
318             # copy the state array to output array and reverse the CBC
319 9         19 for ($i=0; $i<4; ++$i) {
320 36         56 for ($j=0; $j<4; ++$j) {
321 144         153 my $k = $i*4 + $j;
322 144         233 $out[$k] = $state[$j][$i] ^ $cbc[$k];
323             }
324             }
325 9         20 @cbc = @in; # update CBC for next block
326 9         64 return pack 'C*', @out; # return packed plaintext
327             }
328              
329             #------------------------------------------------------------------------------
330             # Encrypt/Decrypt using AES-CBC algorithm (with fixed 16-byte blocks)
331             # Inputs: 0) data reference (with leading 16-byte initialization vector when decrypting)
332             # 1) encryption key (16, 24 or 32 bytes for AES-128, AES-192 or AES-256)
333             # 2) encrypt flag (false for decryption, true with length 16 bytes to
334             # encrypt using this as the CBC IV, or true with other length to
335             # encrypt with a randomly-generated IV)
336             # 3) flag to disable padding
337             # Returns: error string, or undef on success
338             # Notes: encrypts/decrypts data in place (encrypted data returned with leading IV)
339             sub Crypt($$;$$)
340             {
341 6     6 1 64 my ($dataPt, $key, $encrypt, $noPad) = @_;
342              
343             # validate key length
344 6         10 my $keyLen = length $key;
345 6 50 66     30 unless ($keyLen == 16 or $keyLen == 24 or $keyLen == 32) {
      66        
346 0         0 return "Invalid AES key length ($keyLen)";
347             }
348 6         12 my $partLen = length($$dataPt) % 16;
349 6         10 my ($pos, $i);
350 6 50       19 if ($encrypt) {
    50          
    50          
351 0 0       0 if (length($encrypt) == 16) {
352 0         0 @cbc = unpack 'C*', $encrypt;
353             } else {
354             # generate a random 16-byte CBC initialization vector
355 0 0       0 unless ($seeded) {
356 0         0 srand(time() & ($$ + ($$<<15)));
357 0         0 $seeded = 1;
358             }
359 0         0 for ($i=0; $i<16; ++$i) {
360 0         0 $cbc[$i] = int(rand(256));
361             }
362 0         0 $encrypt = pack 'C*', @cbc;
363             }
364 0         0 $$dataPt = $encrypt . $$dataPt; # add IV to the start of the data
365             # add required padding so we can recover the
366             # original string length after decryption
367             # (padding bytes have value set to padding length)
368 0         0 my $padLen = 16 - $partLen;
369 0 0 0     0 $$dataPt .= (chr($padLen)) x $padLen unless $padLen == 16 and $noPad;
370 0         0 $pos = 16; # start encrypting at byte 16 (after the IV)
371             } elsif ($partLen) {
372 0         0 return 'Invalid AES ciphertext length';
373             } elsif (length $$dataPt >= 32) {
374             # take the CBC initialization vector from the start of the data
375 6         20 @cbc = unpack 'C16', $$dataPt;
376 6         15 $$dataPt = substr($$dataPt, 16);
377 6         7 $pos = 0; # start decrypting from byte 0 (now that IV is removed)
378             } else {
379 0         0 $$dataPt = ''; # empty text
380 0         0 return undef;
381             }
382             # the KeyExpansion routine must be called before encryption
383 6         13 KeyExpansion($key);
384              
385             # loop through the data and convert in blocks
386 6         9 my $dataLen = length $$dataPt;
387 6         10 my $last = $dataLen - 16;
388 6 50       11 my $func = $encrypt ? \&Cipher : \&InvCipher;
389 6         12 while ($pos <= $last) {
390             # cipher this block
391 9         26 substr($$dataPt, $pos, 16) = &$func(substr($$dataPt, $pos, 16));
392 9         30 $pos += 16;
393             }
394 6 100 66     24 unless ($encrypt or $noPad) {
395             # remove padding if necessary (padding byte value gives length of padding)
396 4         9 my $padLen = ord(substr($$dataPt, -1, 1));
397 4 50       9 return 'AES decryption error (invalid pad byte)' if $padLen > 16;
398 4         7 $$dataPt = substr($$dataPt, 0, $dataLen - $padLen);
399             }
400 6         18 return undef;
401             }
402              
403             1; # end
404              
405              
406             __END__