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SSH2: workaround for bad arcfour256 implementations

This commit is contained in:
terrafrost 2017-08-26 19:50:17 -05:00
parent 143d28bafa
commit e5b4eef91f
1 changed files with 82 additions and 0 deletions
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82
phpseclib/Net/SSH2.php
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@ -891,6 +891,31 @@ class Net_SSH2
*/
var $send_kex_first = true;
/**
* Some versions of OpenSSH incorrectly calculate the key size
*
* @var bool
* @access private
*/
var $bad_key_size_fix = false;
/**
* The selected decryption algorithm
*
* @var string
* @access private
*/
var $decrypt_algorithm = '';
/**
* Should we try to re-connect to re-establish keys?
*
* @var bool
* @access private
*/
var $retry_connect = false;
/**
* Default Constructor.
*
@ -1929,6 +1954,8 @@ class Net_SSH2
//$this->decrypt = new Crypt_Null();
}
$this->decrypt_algorithm = $decrypt;
$keyBytes = pack('Na*', strlen($keyBytes), $keyBytes);
if ($this->encrypt) {
@ -2087,6 +2114,10 @@ class Net_SSH2
*/
function _encryption_algorithm_to_key_size($algorithm)
{
if ($this->bad_key_size_fix && $this->_bad_algorithm_candidate($algorithm)) {
return 16;
}
switch ($algorithm) {
case 'none':
return 0;
@ -2117,6 +2148,27 @@ class Net_SSH2
return null;
}
/**
* Tests whether or not proposed algorithm has a potential for issues
*
* @link https://www.chiark.greenend.org.uk/~sgtatham/putty/wishlist/ssh2-aesctr-openssh.html
* @link https://bugzilla.mindrot.org/show_bug.cgi?id=1291
* @param string $algorithm Name of the encryption algorithm
* @return bool
* @access private
*/
function _bad_algorithm_candidate($algorithm)
{
switch ($algorithm) {
case 'arcfour256':
case 'aes192-ctr':
case 'aes256-ctr':
return true;
}
return false;
}
/**
* Login
*
@ -2196,6 +2248,13 @@ class Net_SSH2
$response = $this->_get_binary_packet();
if ($response === false) {
if ($this->retry_connect) {
$this->retry_connect = false;
if (!$this->_connect()) {
return false;
}
return $this->_login_helper($username, $password);
}
user_error('Connection closed by server');
return false;
}
@ -3219,6 +3278,24 @@ class Net_SSH2
return (bool) ($this->bitmap & NET_SSH2_MASK_LOGIN);
}
/**
* Resets a connection for re-use
*
* @param int $reason
* @access private
*/
function _reset_connection($reason)
{
$this->_disconnect($reason);
$this->decrypt = $this->encrypt = false;
$this->decrypt_block_size = $this->encrypt_block_size = 8;
$this->hmac_check = $this->hmac_create = false;
$this->hmac_size = false;
$this->session_id = false;
$this->retry_connect = true;
$this->get_seq_no = $this->send_seq_no = 0;
}
/**
* Gets Binary Packets
*
@ -3262,6 +3339,11 @@ class Net_SSH2
// "implementations SHOULD check that the packet length is reasonable"
// PuTTY uses 0x9000 as the actual max packet size and so to shall we
if ($remaining_length < -$this->decrypt_block_size || $remaining_length > 0x9000 || $remaining_length % $this->decrypt_block_size != 0) {
if (!$this->bad_key_size_fix && $this->_bad_algorithm_candidate($this->decrypt_algorithm) && !($this->bitmap & NET_SSH2_MASK_LOGIN)) {
$this->bad_key_size_fix = true;
$this->_reset_connection(NET_SSH2_DISCONNECT_KEY_EXCHANGE_FAILED);
return false;
}
user_error('Invalid size');
return false;
}