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AES: inconsistencey with 160 / 224-bits keys

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re: https://github.com/phpseclib/phpseclib/issues/110
This commit is contained in:
Hans-Jürgen Petrich 2013-06-01 08:00:04 +07:00
parent e71ec8f4c8
commit 53276ba4a1
2 changed files with 73 additions and 48 deletions
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60
phpseclib/Crypt/AES.php
View File

@ -193,6 +193,39 @@ class Crypt_AES extends Crypt_Rijndael {
return;
}
/**
* Sets the key length
*
* Valid key lengths are 128, 160, 192, 224, and 256. If the length is less than 128, it will be rounded up to
* 128. If the length is greater than 128 and invalid, it will be rounded down to the closest valid amount.
*
* Note: phpseclib extends AES for using 160- and 224-bit keys but they are officially not defined in AES
* and the most (if not all) implementations of AES are not able using 160/224-bit keys but round/pad
* them up to 192/256 bits as, for example, mcrypt will do.
*
* That said, if you want be compatible with other AES implementations,
* you should not setKeyLength(160) or setKeyLength(224).
*
* Additional: In case of 160- and 224-bit keys, phpseclib will/can, for that reason, not use
* the mcrypt php extention, even if available. This results then in slower encryption.
*
* @access public
* @param Integer $length
*/
function setKeyLength($length)
{
parent::setKeyLength($length);
switch ($this->key_size) {
case 20: // 160-bits
case 28: // 224-bits
$this->engine = CRYPT_AES_MODE_INTERNAL; // because mcrypt is not able to use (real) 160/224-bit keys
break; // we force using our internal AES engine instead of mcrypt.
default:
$this->engine = CRYPT_AES_MODE;
}
}
/**
* Setup the CRYPT_MODE_MCRYPT $engine
*
@ -204,33 +237,20 @@ class Crypt_AES extends Crypt_Rijndael {
function _setupMcrypt()
{
if (!$this->explicit_key_length) {
// this just copied from Crypt_Rijndael::_setup()
$length = strlen($this->key) >> 2;
if ($length > 8) {
$length = 8;
} else if ($length < 4) {
$length = 4;
}
$this->Nk = $length;
$this->key_size = $length << 2;
}
switch ($this->Nk) {
case 4: // 128
$length = strlen($this->key);
switch (true) {
case $length <= 16:
$this->key_size = 16;
break;
case 5: // 160
case 6: // 192
case $length <= 24:
$this->key_size = 24;
break;
case 7: // 224
case 8: // 256
default:
$this->key_size = 32;
}
}
$this->password_key_size = $this->key_size;
$this->key = str_pad(substr($this->key, 0, $this->key_size), $this->key_size, chr(0));
$this->key = str_pad(substr($this->key, 0, $this->key_size), $this->key_size, "\0");
parent::_setupMcrypt();
}
}

53
phpseclib/Crypt/Rijndael.php
View File

@ -218,7 +218,7 @@ class Crypt_Rijndael extends Crypt_Base {
* @see setKeyLength()
* @var Integer
* @access private
* @internal The max value is 256 / 8 = 32, the min value is 128 / 8 = 16. Exists in conjunction with $key_size
* @internal The max value is 256 / 8 = 32, the min value is 128 / 8 = 16. Exists in conjunction with $Nk
* because the encryption / decryption / key schedule creation requires this number and not $key_size. We could
* derive this from $key_size or vice versa, but that'd mean we'd have to do multiple shift operations, so in lieu
* of that, we'll just precompute it once.
@ -704,10 +704,6 @@ class Crypt_Rijndael extends Crypt_Base {
*/
function setKey($key)
{
if (strlen($key) > 32) {
$key = substr($key, 0, 32);
}
parent::setKey($key);
}
@ -722,14 +718,22 @@ class Crypt_Rijndael extends Crypt_Base {
*/
function setKeyLength($length)
{
$length >>= 5;
if ($length > 8) {
$length = 8;
} else if ($length < 4) {
$length = 4;
switch (true) {
case $length == 160:
$this->key_size = 20;
break;
case $length == 224:
$this->key_size = 28;
break;
case $length <= 128:
$this->key_size = 16;
break;
case $length <= 192:
$this->key_size = 24;
break;
default:
$this->key_size = 32;
}
$this->Nk = $length;
$this->key_size = $this->password_key_size = $length << 2;
$this->explicit_key_length = true;
$this->changed = true;
@ -970,26 +974,27 @@ class Crypt_Rijndael extends Crypt_Base {
);
if (!$this->explicit_key_length) {
// we do >> 2, here, and not >> 5, as we do above, since strlen($this->key) tells us the number of bytes - not bits
$length = strlen($this->key) >> 2;
if ($length > 8) {
$length = 8;
} else if ($length < 4) {
$length = 4;
$length = strlen($this->key);
switch (true) {
case $length <= 16:
$this->key_size = 16;
break;
case $length <= 24:
$this->key_size = 24;
break;
default:
$this->key_size = 32;
}
$this->Nk = $length;
$this->key_size = $this->password_key_size = $length << 2;
}
$key = str_pad(substr($this->key, 0, $this->key_size), $this->key_size, chr(0));
$key = str_pad(substr($this->key, 0, $this->key_size), $this->key_size, "\0");
if (isset($this->kl['key']) && $key === $this->kl['key'] && $this->key_size === $this->kl['key_size'] && $this->block_size === $this->kl['block_size']) {
// already expanded
return;
}
$this->kl = array('key' => $key, 'block_size' => $this->block_size, 'key_size' => $this->key_size);
$this->kl = array('key' => $key, 'key_size' => $this->key_size, 'block_size' => $this->block_size);
$this->Nk = $this->key_size >> 2;
// see Rijndael-ammended.pdf#page=44
$this->Nr = max($this->Nk, $this->Nb) + 6;