rfc:improve_predictable_prng_random
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rfc:improve_predictable_prng_random [2017/02/02 02:35] – Be clear about RandomState object yohgaki | rfc:improve_predictable_prng_random [2017/09/22 13:28] – external edit 127.0.0.1 | ||
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- | ====== PHP RFC: Improve predictable PRNG random ====== | + | ====== PHP RFC: Improve predictable PRNG random |
* Version: 0.9 | * Version: 0.9 | ||
* Date: 2017-02-01 | * Date: 2017-02-01 | ||
Line 14: | Line 14: | ||
<code php> | <code php> | ||
// We need the same random numbers here | // We need the same random numbers here | ||
- | mt_srand(1234); | + | srand(1234); |
for ($i=0; $i < 10; $i++) { | for ($i=0; $i < 10; $i++) { | ||
// Use my PRNG state | // Use my PRNG state | ||
- | | + | |
} | } | ||
Line 29: | Line 29: | ||
</ | </ | ||
- | **This is not limited to specific request that calls mt_srand($some_value), | + | **Above code worked as it should. PHP 7.1 broke this code.** Similarly, shuffle()/ |
+ | |||
+ | <code php> | ||
+ | // We need the same random numbers here | ||
+ | mt_srand(1234); | ||
+ | for ($i=0; $i < 10; $i++) { | ||
+ | // Use my PRNG state | ||
+ | | ||
+ | } | ||
+ | |||
+ | // Somewhere later in code AND/OR even other requests | ||
+ | |||
+ | // We need to shuffle randomly | ||
+ | shuffle($my_random_array); | ||
+ | </ | ||
+ | |||
+ | **These behaviors are not limited to specific request that calls mt_srand($some_value)/ | ||
PHP should have system and user PRNG state to resolve this behavior. | PHP should have system and user PRNG state to resolve this behavior. | ||
Line 42: | Line 58: | ||
==== Rack of Reseeding ==== | ==== Rack of Reseeding ==== | ||
- | Reseeding is important for PRNG to mitigate guessed random value. Since MT rand is predictable PRNG, using the same PRNG state allows to guess random value. Current PHP only supports very weak initialization and keeps using the same PRNG state once it is initialized. This behavior makes trivial to guess MT rand generated random numbers. | + | Reseeding is important for PRNG to mitigate guessed random value. Since MT rand is predictable PRNG, using the same PRNG state allows to guess next random value easily. Current PHP only supports very weak initialization and keeps using the same PRNG state once it is initialized. This behavior makes trivial to guess MT rand generated random numbers. |
To resolve this issue, PHP should reseed MT rand when state is used certain number of times. | To resolve this issue, PHP should reseed MT rand when state is used certain number of times. | ||
Line 48: | Line 64: | ||
===== Proposal ===== | ===== Proposal ===== | ||
- | ==== Return PRNG state object from mt_srand()/ | + | ==== Return PRNG random |
<code php> | <code php> | ||
- | | + | |
- | | + | |
</ | </ | ||
- | Returned RandomeState | + | mt_srand()/ |
Note: srand() is alias of mt_rand(). Python initializes MT rand state by string data like this proposal. | Note: srand() is alias of mt_rand(). Python initializes MT rand state by string data like this proposal. | ||
Line 70: | Line 86: | ||
<code php> | <code php> | ||
- | int mt_rand([RandomState | + | int mt_rand([RandomMT |
- | int mt_rand(int $min, int $max [, RandomState | + | int mt_rand(int $min, int $max [, RandomMT |
- | int rand([RandomState | + | int rand([Random |
- | int rand(int $min, int $max [, RandomState | + | int rand(int $min, int $max [, Random |
- | bool shuffle(array &$arr [, RandomSatate | + | bool shuffle(array &$arr [, Random |
</ | </ | ||
When user initialized PRNG state object is specified, specified state is used to generate random values. | When user initialized PRNG state object is specified, specified state is used to generate random values. | ||
- | ==== RandomState | + | ==== Random |
- | Create | + | Create |
<code php> | <code php> | ||
- | interface | + | interface |
- | public function seed(); | + | public function getInt(int $min = NULL, int $max = NULL); // Int random |
- | public function getCount(); | + | public function getBytes(int $length); // Raw bytes |
- | public function getReseedCycle(); | + | public function getString(int $length, int $bits = 6); // String [0-9a-zA-Z, |
- | public function setReseedCycle(int $count); | + | public function seed($seed = NULL); // No use with CS RNG, raise exception. |
+ | public function getState(); // Return string representation PRNG state. No use with CS RNG, raise exception. | ||
+ | public function setState(string $state); // Set PRNG state. No use with CS RNG, raise exception. | ||
+ | public function getCount(); | ||
+ | public function getReseedCycle(); | ||
+ | public function setReseedCycle(int $count); | ||
} | } | ||
- | class RandomStateMTrand | + | class RandamCS |
+ | // random_*() functions OO API | ||
+ | // Description omitted, see RandomMT | ||
+ | } | ||
+ | |||
+ | // Implement True RNG which may block process when TRNG abstraction function is implemented | ||
+ | class RandamTRNG implements RandomIterface { | ||
+ | // Description omitted, see RandomMT | ||
+ | } | ||
+ | |||
+ | class RandomMT implements RandomInterface | ||
private int $count = 0; // Number of this state is used to generate random value | private int $count = 0; // Number of this state is used to generate random value | ||
private int $reseed = 100; // Max number of count to reseed automatically | private int $reseed = 100; // Max number of count to reseed automatically | ||
private string $state; // Binary PRNG state | private string $state; // Binary PRNG state | ||
+ | | ||
+ | public function __construct($seed = NULL) { | ||
+ | $this-> | ||
+ | } | ||
+ | |||
+ | private reseed() { | ||
+ | $this-> | ||
+ | if ($this-> | ||
+ | $this-> | ||
+ | $this-> | ||
+ | } | ||
+ | } | ||
+ | | ||
+ | public function getInt($min = NULL, $max = NULL) { | ||
+ | assert($min <= $max); | ||
+ | $this-> | ||
+ | if ($min && $max) { | ||
+ | return mt_rand($min, | ||
+ | } | ||
+ | if ($min && $min > 0) { | ||
+ | // Return array of random values | ||
+ | while ($min--) { | ||
+ | $ret[] = mt_rand(); | ||
+ | } | ||
+ | return $ret; | ||
+ | } | ||
+ | trigger_error(' | ||
+ | return FALSE; | ||
+ | } | ||
+ | | ||
+ | public function getBytes(int $length) { | ||
+ | // Return raw random bytes. 3 out of 4 bytes are used not to disclose full PRNG state | ||
+ | } | ||
+ | | ||
+ | public function getString(int $length, int $bits) { | ||
+ | // Return random string as in bin_to_readable() in ext/ | ||
+ | // Only 4 to 6 bits out of a byte is used to avoid disclosing raw PRNG state and simplicity. | ||
+ | } | ||
| | ||
public function seed($seed = NULL) { | public function seed($seed = NULL) { | ||
Line 103: | Line 172: | ||
// Update state by user seed | // Update state by user seed | ||
mt_srand($seed); | mt_srand($seed); | ||
+ | $this-> | ||
} else { | } else { | ||
// Seed by system generated random value | // Seed by system generated random value | ||
Line 128: | Line 198: | ||
} | } | ||
} | } | ||
+ | </ | ||
+ | |||
+ | Random object has getBytes() and getString(). Implement function also. | ||
+ | |||
+ | <code php> | ||
+ | string mt_rand_bytes(int $length [, RandomMT $rand]) | ||
+ | string mt_rand_string(int $length [, RandomMT $rand]) | ||
+ | string rand_bytes(int $length [, Random $rand] ) // Alias of mt_rand_raw() now, but signature differs from MT rand to allow better PRNG in the future. | ||
+ | string rand_string(int $length [,int $bits [, Random $rand]]) // Alias of mt_rand_string() | ||
+ | string random_string(int $length [,int $bits]) | ||
</ | </ | ||
Line 139: | Line 219: | ||
</ | </ | ||
- | uint32_t BG(mt_rand_is_seeded) is used for already seeded flag and counter. | + | uint32_t BG(mt_rand_is_seeded) is used for already seeded flag and counter. |
Line 147: | Line 227: | ||
mt_srand()/ | mt_srand()/ | ||
- | If users want static random values, they have to use RandomStatus | + | If users want static random values, they have to use Random |
===== Proposed PHP Version(s) ===== | ===== Proposed PHP Version(s) ===== | ||
Line 189: | Line 269: | ||
===== Future Scope ===== | ===== Future Scope ===== | ||
- | Add object based predictable PRNG API. | + | Add Random objects as it required |
===== Proposed Voting Choices ===== | ===== Proposed Voting Choices ===== |
rfc/improve_predictable_prng_random.txt · Last modified: 2018/03/01 23:13 by carusogabriel