Algorithm::_checkKEKSize() - Code Metrics - sop/aes-kw - Measure and Improve Code Quality continuously with Scrutinizer

Algorithm::_checkKEKSize() A
last analyzed 2019-05-23 10:28 UTC

↳ Parent: Algorithm

Complexity

Conditions	2
Paths	2

Size

Total Lines	7
Code Lines	4

Duplication

Lines	0
Ratio	0 %

Code Coverage

Tests	5
CRAP Score	2

Importance

Changes

Metric	Value
eloc	4
dl	0
loc	7
ccs	5
cts	5
cp	1
rs	10
c	0
b	0
f	0
cc	2
nc	2
nop	1
crap	2

<?php

declare(strict_types = 1);

namespace Sop\AESKW;

/**
 * Base class for AES key wrap algorithms with varying key sizes.
 *
 * @see https://tools.ietf.org/html/rfc3394
 */
abstract class Algorithm implements AESKeyWrapAlgorithm
{
    /**
     * Default initial value.
     *
     * @see https://tools.ietf.org/html/rfc3394#section-2.2.3.1
     *
     * @var string
     */
    const DEFAULT_IV = "\xA6\xA6\xA6\xA6\xA6\xA6\xA6\xA6";

    /**
     * High order bytes of the alternative initial value for padding.
     *
     * @see https://tools.ietf.org/html/rfc5649#section-3
     *
     * @var string
     */
    const AIV_HI = "\xA6\x59\x59\xA6";

    /**
     * Initial value.
     *
     * @var string
     */
    protected $_iv;

    /**
     * Constructor.
     *
     * @param string $iv Initial value
     */
    public function __construct(string $iv = self::DEFAULT_IV)
    {
        if (8 !== strlen($iv)) {
            throw new \UnexpectedValueException('IV size must be 64 bits.');
        }
        $this->_iv = $iv;
    }

    /**
     * Wrap a key using given key encryption key.
     *
     * Key length must be at least 64 bits (8 octets) and a multiple
     * of 64 bits (8 octets). Use `wrapPad()` to wrap a key of arbitrary length.
     *
     * Key encryption key must have a size of underlying AES algorithm,
     * ie. 128, 196 or 256 bits.
     *
     * @param string $key Key to wrap
     * @param string $kek Key encryption key
     *
     * @throws \UnexpectedValueException If the key length is invalid
     *
     * @return string Ciphertext
     */
    public function wrap(string $key, string $kek): string
    {
        $key_len = strlen($key);
        // rfc3394 dictates n to be at least 2
        if ($key_len < 16) {
            throw new \UnexpectedValueException(
                'Key length must be at least 16 octets.');
        }
        if (0 !== $key_len % 8) {
            throw new \UnexpectedValueException(
                'Key length must be a multiple of 64 bits.');
        }
        $this->_checkKEKSize($kek);
        // P = plaintext as 64 bit blocks
        $P = [];
        $i = 1;
        foreach (str_split($key, 8) as $val) {
            $P[$i++] = $val;
        }
        $C = $this->_wrapBlocks($P, $kek, $this->_iv);
        return implode('', $C);
    }

    /**
     * Unwrap a key from a ciphertext using given key encryption key.
     *
     * @param string $ciphertext Ciphertext of the wrapped key
     * @param string $kek        Key encryption key
     *
     * @throws \UnexpectedValueException If the ciphertext is invalid
     *
     * @return string Unwrapped key
     */
    public function unwrap(string $ciphertext, string $kek): string
    {
        if (0 !== strlen($ciphertext) % 8) {
            throw new \UnexpectedValueException(
                'Ciphertext length must be a multiple of 64 bits.');
        }
        $this->_checkKEKSize($kek);
        // C = ciphertext as 64 bit blocks with integrity check value prepended
        $C = str_split($ciphertext, 8);
        [$A, $R] = $this->_unwrapBlocks($C, $kek);
        // check integrity value
        if (!hash_equals($this->_iv, $A)) {
            throw new \UnexpectedValueException('Integrity check failed.');
        }
        // output the plaintext
        $P = array_slice($R, 1, null, true);
        return implode('', $P);
    }

    /**
     * Wrap a key of arbitrary length using given key encryption key.
     *
     * This variant of wrapping does not place any restriction on key size.
     *
     * Key encryption key has the same restrictions as with `wrap()` method.
     *
     * @param string $key Key to wrap
     * @param string $kek Key encryption key
     *
     * @throws \UnexpectedValueException If the key length is invalid
     *
     * @return string Ciphertext
     */
    public function wrapPad(string $key, string $kek): string
    {
        if (!strlen($key)) {
            throw new \UnexpectedValueException(
                'Key must have at least one octet.');
        }
        $this->_checkKEKSize($kek);
        [$key, $aiv] = $this->_padKey($key);
        // If the padded key contains exactly eight octets,
        // let the ciphertext be:
        // C[0] | C[1] = ENC(K, A | P[1]).
        if (8 === strlen($key)) {
            return $this->_encrypt($kek, $aiv . $key);
        }
        // build plaintext blocks and apply normal wrapping with AIV as an
        // initial value
        $P = [];
        $i = 1;
        foreach (str_split($key, 8) as $val) {
            $P[$i++] = $val;
        }
        $C = $this->_wrapBlocks($P, $kek, $aiv);
        return implode('', $C);
    }

    /**
     * Unwrap a key from a padded ciphertext using given key encryption key.
     *
     * This variant of unwrapping must be used if the key was wrapped using `wrapPad()`.
     *
     * @param string $ciphertext Ciphertext of the wrapped and padded key
     * @param string $kek        Key encryption key
     *
     * @throws \UnexpectedValueException If the ciphertext is invalid
     *
     * @return string Unwrapped key
     */
    public function unwrapPad(string $ciphertext, string $kek): string
    {
        if (0 !== strlen($ciphertext) % 8) {
            throw new \UnexpectedValueException(
                'Ciphertext length must be a multiple of 64 bits.');
        }
        $this->_checkKEKSize($kek);
        [$P, $A] = $this->_unwrapPaddedCiphertext($ciphertext, $kek);
        // check message integrity
        $this->_checkPaddedIntegrity($A);
        // verify padding
        $len = $this->_verifyPadding($P, $A);
        // remove padding and return unwrapped key
        return substr(implode('', $P), 0, $len);
    }

    /**
     * Get OpenSSL cipher method.
     *
     * @return string
     */
    abstract protected function _cipherMethod(): string;

    /**
     * Get key encryption key size.
     *
     * @return int
     */
    abstract protected function _keySize(): int;

    /**
     * Check KEK size.
     *
     * @param string $kek
     *
     * @throws \UnexpectedValueException
     *
     * @return self
     */
    protected function _checkKEKSize(string $kek): self
    {
        $len = $this->_keySize();
        if (strlen($kek) !== $len) {
            throw new \UnexpectedValueException("KEK size must be {$len} bytes.");
        }
        return $this;
    }

    /**
     * Apply Key Wrap to data blocks.
     *
     * Uses alternative version of the key wrap procedure described in the RFC.
     *
     * @see https://tools.ietf.org/html/rfc3394#section-2.2.1
     *
     * @param string[] $P   Plaintext, n 64-bit values `{P1, P2, ..., Pn}`
     * @param string   $kek Key encryption key
     * @param string   $iv  Initial value
     *
     * @return string[] Ciphertext, (n+1) 64-bit values `{C0, C1, ..., Cn}`
     */
    protected function _wrapBlocks(array $P, string $kek, string $iv): array
    {
        $n = count($P);
        // Set A = IV
        $A = $iv;
        // For i = 1 to n
        //   R[i] = P[i]
        $R = $P;
        // For j = 0 to 5
        for ($j = 0; $j <= 5; ++$j) {
            // For i = 1 to n
            for ($i = 1; $i <= $n; ++$i) {
                // B = AES(K, A | R[i])
                $B = $this->_encrypt($kek, $A . $R[$i]);
                // A = MSB(64, B) ^ t where t = (n*j)+i
                $t = $n * $j + $i;
                $A = $this->_msb64($B) ^ $this->_uint64($t);
                // R[i] = LSB(64, B)
                $R[$i] = $this->_lsb64($B);
            }
        }
        // Set C[0] = A
        $C = [$A];
        // For i = 1 to n
        for ($i = 1; $i <= $n; ++$i) {
            // C[i] = R[i]
            $C[$i] = $R[$i];
        }
        return $C;
    }

    /**
     * Unwrap the padded ciphertext producing plaintext and integrity value.
     *
     * @param string $ciphertext Ciphertext
     * @param string $kek        Encryption key
     *
     * @return array Tuple of plaintext `{P1, P2, ..., Pn}` and integrity value `A`
     */
    protected function _unwrapPaddedCiphertext(string $ciphertext, string $kek): array
    {
        // split to blocks
        $C = str_split($ciphertext, 8);
        $n = count($C) - 1;
        // if key consists of only one block, recover AIV and padded key as:
        // A | P[1] = DEC(K, C[0] | C[1])
        if (1 === $n) {
            $P = str_split($this->_decrypt($kek, $C[0] . $C[1]), 8);
            $A = $P[0];
            unset($P[0]);
        } else {
            // apply normal unwrapping
            [$A, $R] = $this->_unwrapBlocks($C, $kek);
            $P = array_slice($R, 1, null, true);
        }
        return [$P, $A];
    }

    /**
     * Apply Key Unwrap to data blocks.
     *
     * Uses the index based version of key unwrap procedure described in the RFC.
     *
     * Does not compute step 3.
     *
     * @see https://tools.ietf.org/html/rfc3394#section-2.2.2
     *
     * @param string[] $C   Ciphertext, (n+1) 64-bit values `{C0, C1, ..., Cn}`
     * @param string   $kek Key encryption key
     *
     * @throws \UnexpectedValueException
     *
     * @return array Tuple of integrity value `A` and register `R`
     */
    protected function _unwrapBlocks(array $C, string $kek): array
    {
        $n = count($C) - 1;
        if (!$n) {
            throw new \UnexpectedValueException('No blocks.');
        }
        // Set A = C[0]
        $A = $C[0];
        // For i = 1 to n
        //   R[i] = C[i]
        $R = $C;
        // For j = 5 to 0
        for ($j = 5; $j >= 0; --$j) {
            // For i = n to 1
            for ($i = $n; $i >= 1; --$i) {
                // B = AES-1(K, (A ^ t) | R[i]) where t = n*j+i
                $t = $n * $j + $i;
                $B = $this->_decrypt($kek, ($A ^ $this->_uint64($t)) . $R[$i]);
                // A = MSB(64, B)
                $A = $this->_msb64($B);
                // R[i] = LSB(64, B)
                $R[$i] = $this->_lsb64($B);
            }
        }
        return [$A, $R];
    }

    /**
     * Pad a key with zeroes and compute alternative initial value.
     *
     * @param string $key Key
     *
     * @return array Tuple of padded key and AIV
     */
    protected function _padKey(string $key): array
    {
        $len = strlen($key);
        // append padding
        if (0 !== $len % 8) {
            $key .= str_repeat("\0", 8 - $len % 8);
        }
        // compute AIV
        $mli = pack('N', $len);
        $aiv = self::AIV_HI . $mli;
        return [$key, $aiv];
    }

    /**
     * Check that the integrity check value of the padded key is correct.
     *
     * @param string $A
     *
     * @throws \UnexpectedValueException
     */
    protected function _checkPaddedIntegrity(string $A): void
    {
        // check that MSB(32,A) = A65959A6
        if (!hash_equals(self::AIV_HI, substr($A, 0, 4))) {
            throw new \UnexpectedValueException('Integrity check failed.');
        }
    }

    /**
     * Verify that the padding of the plaintext is valid.
     *
     * @param array  $P Plaintext, n 64-bit values `{P1, P2, ..., Pn}`
     * @param string $A Integrity check value
     *
     * @throws \UnexpectedValueException
     *
     * @return int Message length without padding
     */
    protected function _verifyPadding(array $P, string $A): int
    {
        // extract mli
        $mli = substr($A, -4);
        $len = unpack('N1', $mli)[1];
        // check under and overflow
        $n = count($P);
        if (8 * ($n - 1) >= $len || $len > 8 * $n) {
            throw new \UnexpectedValueException('Invalid message length.');
        }
        // if key is padded
        $b = 8 - ($len % 8);
        if ($b < 8) {
            // last block (note that the first index in P is 1)
            $Pn = $P[$n];
            // check that padding consists of zeroes
            if (substr($Pn, -$b) !== str_repeat("\0", $b)) {
                throw new \UnexpectedValueException('Invalid padding.');
            }
        }
        return $len;
    }

    /**
     * Apply AES(K, W) operation (encrypt) to 64 bit block.
     *
     * @param string $kek
     * @param string $block
     *
     * @throws \RuntimeException If encrypt fails
     *
     * @return string
     */
    protected function _encrypt(string $kek, string $block): string
    {
        $str = openssl_encrypt($block, $this->_cipherMethod(), $kek,
            OPENSSL_RAW_DATA | OPENSSL_ZERO_PADDING);
        if (false === $str) {
            throw new \RuntimeException(
                'openssl_encrypt() failed: ' . $this->_getLastOpenSSLError());
        }
        return $str;
    }

    /**
     * Apply AES-1(K, W) operation (decrypt) to 64 bit block.
     *
     * @param string $kek
     * @param string $block
     *
     * @throws \RuntimeException If decrypt fails
     *
     * @return string
     */
    protected function _decrypt(string $kek, string $block): string
    {
        $str = openssl_decrypt($block, $this->_cipherMethod(), $kek,
            OPENSSL_RAW_DATA | OPENSSL_ZERO_PADDING);
        if (false === $str) {
            throw new \RuntimeException(
                'openssl_decrypt() failed: ' . $this->_getLastOpenSSLError());
        }
        return $str;
    }

    /**
     * Get the latest OpenSSL error message.
     *
     * @return string
     */
    protected function _getLastOpenSSLError(): string
    {
        $msg = '';
        while (false !== ($err = openssl_error_string())) {
            $msg = $err;
        }
        return $msg;
    }

    /**
     * Take 64 most significant bits from value.
     *
     * @param string $val
     *
     * @return string
     */
    protected function _msb64(string $val): string
    {
        return substr($val, 0, 8);
    }

    /**
     * Take 64 least significant bits from value.
     *
     * @param string $val
     *
     * @return string
     */
    protected function _lsb64(string $val): string
    {
        return substr($val, -8);
    }

    /**
     * Convert number to 64 bit unsigned integer octet string with
     * most significant bit first.
     *
     * @param int $num
     *
     * @return string
     */
    protected function _uint64(int $num): string
    {
        // truncate on 32 bit hosts
        if (PHP_INT_SIZE < 8) {
            return "\0\0\0\0" . pack('N', $num);
        }
        return pack('J', $num);
    }
}


1		<?php
2
3		declare(strict_types = 1);
4
5		namespace Sop\AESKW;
6
7		/**
8		* Base class for AES key wrap algorithms with varying key sizes.
9		*
10		* @see https://tools.ietf.org/html/rfc3394
11		*/
12		abstract class Algorithm implements AESKeyWrapAlgorithm
13		{
14		/**
15		* Default initial value.
16		*
17		* @see https://tools.ietf.org/html/rfc3394#section-2.2.3.1
18		*
19		* @var string
20		*/
21		const DEFAULT_IV = "\xA6\xA6\xA6\xA6\xA6\xA6\xA6\xA6";
22
23		/**
24		* High order bytes of the alternative initial value for padding.
25		*
26		* @see https://tools.ietf.org/html/rfc5649#section-3
27		*
28		* @var string
29		*/
30		const AIV_HI = "\xA6\x59\x59\xA6";
31
32		/**
33		* Initial value.
34		*
35		* @var string
36		*/
37		protected $_iv;
38
39		/**
40		* Constructor.
41		*
42		* @param string $iv Initial value
43		*/
44	48	public function __construct(string $iv = self::DEFAULT_IV)
45		{
46	48	if (8 !== strlen($iv)) {
47	1	throw new \UnexpectedValueException('IV size must be 64 bits.');
48		}
49	47	$this->_iv = $iv;
50	47	}
51
52		/**
53		* Wrap a key using given key encryption key.
54		*
55		* Key length must be at least 64 bits (8 octets) and a multiple
56		* of 64 bits (8 octets). Use `wrapPad()` to wrap a key of arbitrary length.
57		*
58		* Key encryption key must have a size of underlying AES algorithm,
59		* ie. 128, 196 or 256 bits.
60		*
61		* @param string $key Key to wrap
62		* @param string $kek Key encryption key
63		*
64		* @throws \UnexpectedValueException If the key length is invalid
65		*
66		* @return string Ciphertext
67		*/
68	13	public function wrap(string $key, string $kek): string
69		{
70	13	$key_len = strlen($key);
71		// rfc3394 dictates n to be at least 2
72	13	if ($key_len < 16) {
73	2	throw new \UnexpectedValueException(
74	2	'Key length must be at least 16 octets.');
75		}
76	11	if (0 !== $key_len % 8) {
77	1	throw new \UnexpectedValueException(
78	1	'Key length must be a multiple of 64 bits.');
79		}
80	10	$this->_checkKEKSize($kek);
81		// P = plaintext as 64 bit blocks
82	8	$P = [];
83	8	$i = 1;
84	8	foreach (str_split($key, 8) as $val) {
85	8	$P[$i++] = $val;
86		}
87	8	$C = $this->_wrapBlocks($P, $kek, $this->_iv);
88	8	return implode('', $C);
89		}
90
91		/**
92		* Unwrap a key from a ciphertext using given key encryption key.
93		*
94		* @param string $ciphertext Ciphertext of the wrapped key
95		* @param string $kek Key encryption key
96		*
97		* @throws \UnexpectedValueException If the ciphertext is invalid
98		*
99		* @return string Unwrapped key
100		*/
101	12	public function unwrap(string $ciphertext, string $kek): string
102		{
103	12	if (0 !== strlen($ciphertext) % 8) {
104	1	throw new \UnexpectedValueException(
105	1	'Ciphertext length must be a multiple of 64 bits.');
106		}
107	11	$this->_checkKEKSize($kek);
108		// C = ciphertext as 64 bit blocks with integrity check value prepended
109	10	$C = str_split($ciphertext, 8);
110	10	[$A, $R] = $this->_unwrapBlocks($C, $kek);
111		// check integrity value
112	9	if (!hash_equals($this->_iv, $A)) {
113	1	throw new \UnexpectedValueException('Integrity check failed.');
114		}
115		// output the plaintext
116	8	$P = array_slice($R, 1, null, true);
117	8	return implode('', $P);
118		}
119
120		/**
121		* Wrap a key of arbitrary length using given key encryption key.
122		*
123		* This variant of wrapping does not place any restriction on key size.
124		*
125		* Key encryption key has the same restrictions as with `wrap()` method.
126		*
127		* @param string $key Key to wrap
128		* @param string $kek Key encryption key
129		*
130		* @throws \UnexpectedValueException If the key length is invalid
131		*
132		* @return string Ciphertext
133		*/
134	19	public function wrapPad(string $key, string $kek): string
135		{
136	19	if (!strlen($key)) {
137	1	throw new \UnexpectedValueException(
138	1	'Key must have at least one octet.');
139		}
140	18	$this->_checkKEKSize($kek);
141	17	[$key, $aiv] = $this->_padKey($key);
142		// If the padded key contains exactly eight octets,
143		// let the ciphertext be:
144		// C[0] \| C[1] = ENC(K, A \| P[1]).
145	17	if (8 === strlen($key)) {
146	8	return $this->_encrypt($kek, $aiv . $key);
147		}
148		// build plaintext blocks and apply normal wrapping with AIV as an
149		// initial value
150	9	$P = [];
151	9	$i = 1;
152	9	foreach (str_split($key, 8) as $val) {
153	9	$P[$i++] = $val;
154		}
155	9	$C = $this->_wrapBlocks($P, $kek, $aiv);
156	9	return implode('', $C);
157		}
158
159		/**
160		* Unwrap a key from a padded ciphertext using given key encryption key.
161		*
162		* This variant of unwrapping must be used if the key was wrapped using `wrapPad()`.
163		*
164		* @param string $ciphertext Ciphertext of the wrapped and padded key
165		* @param string $kek Key encryption key
166		*
167		* @throws \UnexpectedValueException If the ciphertext is invalid
168		*
169		* @return string Unwrapped key
170		*/
171	15	public function unwrapPad(string $ciphertext, string $kek): string
172		{
173	15	if (0 !== strlen($ciphertext) % 8) {
174	1	throw new \UnexpectedValueException(
175	1	'Ciphertext length must be a multiple of 64 bits.');
176		}
177	14	$this->_checkKEKSize($kek);
178	13	[$P, $A] = $this->_unwrapPaddedCiphertext($ciphertext, $kek);
179		// check message integrity
180	13	$this->_checkPaddedIntegrity($A);
181		// verify padding
182	12	$len = $this->_verifyPadding($P, $A);
183		// remove padding and return unwrapped key
184	10	return substr(implode('', $P), 0, $len);
185		}
186
187		/**
188		* Get OpenSSL cipher method.
189		*
190		* @return string
191		*/
192		abstract protected function _cipherMethod(): string;
193
194		/**
195		* Get key encryption key size.
196		*
197		* @return int
198		*/
199		abstract protected function _keySize(): int;
200
201		/**
202		* Check KEK size.
203		*
204		* @param string $kek
205		*
206		* @throws \UnexpectedValueException
207		*
208		* @return self
209		*/
210	38	protected function _checkKEKSize(string $kek): self
211		{
212	38	$len = $this->_keySize();
213	38	if (strlen($kek) !== $len) {
214	5	throw new \UnexpectedValueException("KEK size must be {$len} bytes.");
215		}
216	33	return $this;
217		}
218
219		/**
220		* Apply Key Wrap to data blocks.
221		*
222		* Uses alternative version of the key wrap procedure described in the RFC.
223		*
224		* @see https://tools.ietf.org/html/rfc3394#section-2.2.1
225		*
226		* @param string[] $P Plaintext, n 64-bit values `{P1, P2, ..., Pn}`
227		* @param string $kek Key encryption key
228		* @param string $iv Initial value
229		*
230		* @return string[] Ciphertext, (n+1) 64-bit values `{C0, C1, ..., Cn}`
231		*/
232	17	protected function _wrapBlocks(array $P, string $kek, string $iv): array
233		{
234	17	$n = count($P);
235		// Set A = IV
236	17	$A = $iv;
237		// For i = 1 to n
238		// R[i] = P[i]
239	17	$R = $P;
240		// For j = 0 to 5
241	17	for ($j = 0; $j <= 5; ++$j) {
242		// For i = 1 to n
243	17	for ($i = 1; $i <= $n; ++$i) {
244		// B = AES(K, A \| R[i])
245	17	$B = $this->_encrypt($kek, $A . $R[$i]);
246		// A = MSB(64, B) ^ t where t = (n*j)+i
247	17	$t = $n * $j + $i;
248	17	$A = $this->_msb64($B) ^ $this->_uint64($t);
249		// R[i] = LSB(64, B)
250	17	$R[$i] = $this->_lsb64($B);
251		}
252		}
253		// Set C[0] = A
254	17	$C = [$A];
255		// For i = 1 to n
256	17	for ($i = 1; $i <= $n; ++$i) {
257		// C[i] = R[i]
258	17	$C[$i] = $R[$i];
259		}
260	17	return $C;
261		}
262
263		/**
264		* Unwrap the padded ciphertext producing plaintext and integrity value.
265		*
266		* @param string $ciphertext Ciphertext
267		* @param string $kek Encryption key
268		*
269		* @return array Tuple of plaintext `{P1, P2, ..., Pn}` and integrity value `A`
270		*/
271	13	protected function _unwrapPaddedCiphertext(string $ciphertext, string $kek): array
272		{
273		// split to blocks
274	13	$C = str_split($ciphertext, 8);
275	13	$n = count($C) - 1;
276		// if key consists of only one block, recover AIV and padded key as:
277		// A \| P[1] = DEC(K, C[0] \| C[1])
278	13	if (1 === $n) {
279	8	$P = str_split($this->_decrypt($kek, $C[0] . $C[1]), 8);
280	8	$A = $P[0];
281	8	unset($P[0]);
282		} else {
283		// apply normal unwrapping
284	5	[$A, $R] = $this->_unwrapBlocks($C, $kek);
285	5	$P = array_slice($R, 1, null, true);
286		}
287	13	return [$P, $A];
288		}
289
290		/**
291		* Apply Key Unwrap to data blocks.
292		*
293		* Uses the index based version of key unwrap procedure described in the RFC.
294		*
295		* Does not compute step 3.
296		*
297		* @see https://tools.ietf.org/html/rfc3394#section-2.2.2
298		*
299		* @param string[] $C Ciphertext, (n+1) 64-bit values `{C0, C1, ..., Cn}`
300		* @param string $kek Key encryption key
301		*
302		* @throws \UnexpectedValueException
303		*
304		* @return array Tuple of integrity value `A` and register `R`
305		*/
306	15	protected function _unwrapBlocks(array $C, string $kek): array
307		{
308	15	$n = count($C) - 1;
309	15	if (!$n) {
310	1	throw new \UnexpectedValueException('No blocks.');
311		}
312		// Set A = C[0]
313	14	$A = $C[0];
314		// For i = 1 to n
315		// R[i] = C[i]
316	14	$R = $C;
317		// For j = 5 to 0
318	14	for ($j = 5; $j >= 0; --$j) {
319		// For i = n to 1
320	14	for ($i = $n; $i >= 1; --$i) {
321		// B = AES-1(K, (A ^ t) \| R[i]) where t = n*j+i
322	14	$t = $n * $j + $i;
323	14	$B = $this->_decrypt($kek, ($A ^ $this->_uint64($t)) . $R[$i]);
324		// A = MSB(64, B)
325	14	$A = $this->_msb64($B);
326		// R[i] = LSB(64, B)
327	14	$R[$i] = $this->_lsb64($B);
328		}
329		}
330	14	return [$A, $R];
331		}
332
333		/**
334		* Pad a key with zeroes and compute alternative initial value.
335		*
336		* @param string $key Key
337		*
338		* @return array Tuple of padded key and AIV
339		*/
340	17	protected function _padKey(string $key): array
341		{
342	17	$len = strlen($key);
343		// append padding
344	17	if (0 !== $len % 8) {
345	12	$key .= str_repeat("\0", 8 - $len % 8);
346		}
347		// compute AIV
348	17	$mli = pack('N', $len);
349	17	$aiv = self::AIV_HI . $mli;
350	17	return [$key, $aiv];
351		}
352
353		/**
354		* Check that the integrity check value of the padded key is correct.
355		*
356		* @param string $A
357		*
358		* @throws \UnexpectedValueException
359		*/
360	13	protected function _checkPaddedIntegrity(string $A): void
361		{
362		// check that MSB(32,A) = A65959A6
363	13	if (!hash_equals(self::AIV_HI, substr($A, 0, 4))) {
364	1	throw new \UnexpectedValueException('Integrity check failed.');
365		}
366	12	}
367
368		/**
369		* Verify that the padding of the plaintext is valid.
370		*
371		* @param array $P Plaintext, n 64-bit values `{P1, P2, ..., Pn}`
372		* @param string $A Integrity check value
373		*
374		* @throws \UnexpectedValueException
375		*
376		* @return int Message length without padding
377		*/
378	12	protected function _verifyPadding(array $P, string $A): int
379		{
380		// extract mli
381	12	$mli = substr($A, -4);
382	12	$len = unpack('N1', $mli)[1];
383		// check under and overflow
384	12	$n = count($P);
385	12	if (8 * ($n - 1) >= $len \|\| $len > 8 * $n) {
386	1	throw new \UnexpectedValueException('Invalid message length.');
387		}
388		// if key is padded
389	11	$b = 8 - ($len % 8);
390	11	if ($b < 8) {
391		// last block (note that the first index in P is 1)
392	8	$Pn = $P[$n];
393		// check that padding consists of zeroes
394	8	if (substr($Pn, -$b) !== str_repeat("\0", $b)) {
395	1	throw new \UnexpectedValueException('Invalid padding.');
396		}
397		}
398	10	return $len;
399		}
400
401		/**
402		* Apply AES(K, W) operation (encrypt) to 64 bit block.
403		*
404		* @param string $kek
405		* @param string $block
406		*
407		* @throws \RuntimeException If encrypt fails
408		*
409		* @return string
410		*/
411	26	protected function _encrypt(string $kek, string $block): string
412		{
413	26	$str = openssl_encrypt($block, $this->_cipherMethod(), $kek,
414	26	OPENSSL_RAW_DATA \| OPENSSL_ZERO_PADDING);
415	26	if (false === $str) {
416	1	throw new \RuntimeException(
417	1	'openssl_encrypt() failed: ' . $this->_getLastOpenSSLError());
418		}
419	25	return $str;
420		}
421
422		/**
423		* Apply AES-1(K, W) operation (decrypt) to 64 bit block.
424		*
425		* @param string $kek
426		* @param string $block
427		*
428		* @throws \RuntimeException If decrypt fails
429		*
430		* @return string
431		*/
432	23	protected function _decrypt(string $kek, string $block): string
433		{
434	23	$str = openssl_decrypt($block, $this->_cipherMethod(), $kek,
435	23	OPENSSL_RAW_DATA \| OPENSSL_ZERO_PADDING);
436	23	if (false === $str) {
437	1	throw new \RuntimeException(
438	1	'openssl_decrypt() failed: ' . $this->_getLastOpenSSLError());
439		}
440	22	return $str;
441		}
442
443		/**
444		* Get the latest OpenSSL error message.
445		*
446		* @return string
447		*/
448	2	protected function _getLastOpenSSLError(): string
449		{
450	2	$msg = '';
451	2	while (false !== ($err = openssl_error_string())) {
452	2	$msg = $err;
453		}
454	2	return $msg;
455		}
456
457		/**
458		* Take 64 most significant bits from value.
459		*
460		* @param string $val
461		*
462		* @return string
463		*/
464	20	protected function _msb64(string $val): string
465		{
466	20	return substr($val, 0, 8);
467		}
468
469		/**
470		* Take 64 least significant bits from value.
471		*
472		* @param string $val
473		*
474		* @return string
475		*/
476	20	protected function _lsb64(string $val): string
477		{
478	20	return substr($val, -8);
479		}
480
481		/**
482		* Convert number to 64 bit unsigned integer octet string with
483		* most significant bit first.
484		*
485		* @param int $num
486		*
487		* @return string
488		*/
489	20	protected function _uint64(int $num): string
490		{
491		// truncate on 32 bit hosts
492	20	if (PHP_INT_SIZE < 8) {
493		return "\0\0\0\0" . pack('N', $num);
494		}
495	20	return pack('J', $num);
496		}
497		}
498

sop / aes-kw

Algorithm::_checkKEKSize() A last analyzed 2019-05-23 10:28 UTC

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Algorithm::_checkKEKSize() A
last analyzed 2019-05-23 10:28 UTC