These are always dynamically allocated in GINIT, thus always take up memory. By
embedding them here we can avoid the dynamic allocation and additional pointer
indirection accessing them.
The test script:
<?php
for ($i = 0; $i < 9999999; $i++) mt_rand(1, 100);
Appears to run slightly faster with this change applied: Before this change it
always ran in just over 3 seconds, after this change I was also seeing times
below 3 seconds. Howver results are too close and too jittery to state this
performance improvement as a fact.
PHP 8.1 and below interpreted unknown modes as `MT_RAND_MT19937`, but PHP 8.2+
interprets them as `MT_RAND_PHP`.
Align the behavior with PHP 8.1 and below, because folks should be steered
towards the standard mode.
* random: Expose xoshiro256**'s seeding functions
* random: Expose pcgoneseq128xslrr64's seeding functions
* random: Expose Mt19937's seeding functions
* random: Expose CombinedLCG's seeding functions
* random: Call php_random_mt19937_seed32 to seed the global Mt19937
This avoids the function pointer indirection and improves type safety.
* random: NULL the generic seeding function
Different engines work quite differently, it is not useful to attempt to seed
them in a generic way using a 64 bit integer. As an example Mt19937 completely
ignores the upper 32 bits.
* random: Remove the `seed` member from `php_random_algo`
See the explanation in the previous commit for the reasoning. This member is
unused since the previous commit and was not consistently available even before
that (specifically for the Secure engine).
* UPGRADING.INTERNALS
* random: Remove useless cast in `php_mt_srand()`
* random: Remove `php_random_status`
Since 162e1dce98, the `php_random_status` struct
contains just a single `void*`, resulting in needless indirection when
accessing the engine state and thus decreasing readability because of the
additional non-meaningful `->state` references / the local helper variables.
There is also a small, but measurable performance benefit:
<?php
$e = new Random\Engine\Xoshiro256StarStar(0);
$r = new Random\Randomizer($e);
for ($i = 0; $i < 15; $i++)
var_dump(strlen($r->getBytes(100000000)));
goes from roughly 3.85s down to 3.60s.
The names of the `status` variables have not yet been touched to keep the diff
small. They will be renamed to the more appropriate `state` in a follow-up
cleanup commit.
* Introduce `php_random_algo_with_state`
This allows consumers of just the CSPRNG to include a much smaller header. It
also allows to verify at a glance whether a source file might use non-secure
randomness.
This commit includes the new header wherever the CSPRNG is used, possibly
replacing the inclusion of php_random.h if nothing else is used, but also
includes it in the main php_random.h header for compatibility.
Somewhat related to 45f8cfaf10,
2b30f18708, and
b14dd85dca.
Instead of returning the generated `uint64_t` and providing the size (i.e. the
number of bytes of the generated value) out-of-band via the
`last_generated_size` member of the `php_random_status` struct, the `generate`
function is now expected to return a new `php_random_result` struct containing
both the `size` and the `result`.
This has two benefits, one for the developer:
It's no longer possible to forget setting `last_generated_size` to the correct
value, because it now happens at the time of returning from the function.
and the other benefit is for performance:
The `php_random_result` struct will be returned as a register pair, thus the
`size` will be directly available without reloading it from main memory.
Checking a simplified version of `php_random_range64()` on Compiler Explorer
(“Godbolt”) with clang 17 shows a single change in the resulting assembly
showcasing the improvement (https://godbolt.org/z/G4WjdYxqx):
- add rbp, qword ptr [r14]
+ add rbp, rdx
Empirical testing confirms a measurable performance increase for the
`Randomizer::getBytes()` method:
<?php
$e = new Random\Engine\Xoshiro256StarStar(0);
$r = new Random\Randomizer($e);
var_dump(strlen($r->getBytes(100000000)));
goes from 250ms (before the change) to 220ms (after the change). While
generating 100 MB of random data certainly is not the most common use case, it
confirms the theoretical improvement in practice.
The CSPRNG is a delicate and security relevant piece of code and having it in
the giant random.c makes it much harder to verify changes to it. Split it into
a separate file.
* random: Convert the urandom loop into a while() loop
This allows us to more easily reduce the scope of `n` in a future commit and
now matches the getrandom(2) loop.
* random: Move the errno reset immediately above the getrandom(2) call
* random: Reduce the scope of `n` in the CSPRNG
* random: Declare `n` outside of preprocessor branch
The only way the previous `if (read_bytes < size)` branch could be taken is
when the loop was exited by the `break;` statement. We can just merge this into
the loop to make the code more obvious.
This effectively reverts #8984.
As discussed in #10327 which will enable the use of the getrandom(2) syscall on
NetBSD instead of relying on the userland arc4random_buf(), the CSPRNG should
prioritize security over speed [1] and history has shown that userland
implementations unavoidably fall short on the security side. In fact the glibc
implementation is a thin wrapper around the syscall due to security concerns
and thus does not provide any benefit over just calling getrandom(2) ourselves.
Even without any performance optimizations the CSPRNG should be plenty fast for
the vast majority of applications, because they often only need a few bytes of
randomness to generate a session ID. If speed is desired, the OO API offers
faster, but non-cryptographically secure engines.
It cannot be decided whether the device is available at build time, PHP might
run in a container or chroot that does not expose the device. Simply attempt to
open it, if it does not exist it will fail.
This improves readability of php_random_bytes() by removing one layer of
preprocessor conditions.
If, for whatever reason, the random_fd has been assigned file descriptor `0` it
previously failed to close during module shutdown, thus leaking the descriptor.
* random: Add Randomizer::nextFloat()
* random: Check that doubles are IEEE-754 in Randomizer::nextFloat()
* random: Add Randomizer::nextFloat() tests
* random: Add Randomizer::getFloat() implementing the y-section algorithm
The algorithm is published in:
Drawing Random Floating-Point Numbers from an Interval. Frédéric
Goualard, ACM Trans. Model. Comput. Simul., 32:3, 2022.
https://doi.org/10.1145/3503512
* random: Implement getFloat_gamma() optimization
see https://github.com/php/php-src/pull/9679/files#r994668327
* random: Add Random\IntervalBoundary
* random: Split the implementation of γ-section into its own file
* random: Add tests for Randomizer::getFloat()
* random: Fix γ-section for 32-bit systems
* random: Replace check for __STDC_IEC_559__ by compile-time check for DBL_MANT_DIG
* random: Drop nextFloat_spacing.phpt
* random: Optimize Randomizer::getFloat() implementation
* random: Reject non-finite parameters in Randomizer::getFloat()
* random: Add NEWS/UPGRADING for Randomizer’s float functionality
* Fix pre-PHP 8.2 compatibility for php_mt_rand_range() with MT_RAND_PHP
As some left-over comments indicated:
> Legacy mode deliberately not inside php_mt_rand_range()
> to prevent other functions being affected
The broken scaler was only used for `php_mt_rand_common()`, not
`php_mt_rand_range()`. The former is only used for `mt_rand()`, whereas the
latter is used for `array_rand()` and others.
With the refactoring for the introduction of ext/random `php_mt_rand_common()`
and `php_mt_rand_range()` were accidentally unified, thus introducing a
behavioral change that was reported in FakerPHP/Faker#528.
This commit moves the checks for `MT_RAND_PHP` from the general-purpose
`range()` function back into `php_mt_rand_common()` and also into
`Randomizer::getInt()` for drop-in compatibility with `mt_rand()`.
* [ci skip] NEWS for `MT_RAND_PHP` compatibility
This reverts commit 94ee4f9834.
The commit was a bit too late to be included in PHP 8.2 RC1. Given it's a massive ABI break, we decide to postpone the change to PHP 8.3.
This fixes an incompatibility when wrapping native 32-bit engines with a userland
engine. The latter always used the 64-bit range function which then used two
32-bit numbers from the underlying engine to fill the 64-bit range, whereas the
native implementation used only one.
Now the selection of the range variant only depends on the requested range. A
32-bit range uses the 32-bit variant (even for 64-bit engines), whereas a
larger range uses the 64-bit variant.
This was found in https://github.com/php/php-src/pull/9410#discussion_r953213000
* Fix rand_range32() for umax = UINT32_MAX
This was introduced in the commit that added the random extension:
4d8dd8d258.
Resolves GH-9415
* [ci skip] Rename `$r` to `$randomizer` in gh9415.phpt
* Make gh9415.phpt deterministic
* Make gh9415.phpt compatible with 32-bit
* Add Random\Random{Error,Exception} and Random\BrokenRandomEngineError
* Throw BrokenRandomEngineError
* Throw RandomException on seeding failure
* Throw RandomException when CSPRNG fails
* Remove unused include from ext/random/engine_combinedlcg.c
* Remove unused include from ext/random/engine_secure.c
* Remove unused include from ext/random/random.c
* [ci skip] Add ext/random Exception hierarchy to NEWS
* [ci skip] Add the change of Exception for random_(int|bytes) to UPGRADING
Whenever ->last_unsafe is set to `true` an exception has been thrown. Thus we
can replace the check for `->last_unsafe` with a check for `EG(exception)`
which is a much more natural way to ommunicate an error up the chain.
* Use `php_random_bytes_throw()` in Secure engine's generate()
This exposes the underlying exception, improving debugging:
Fatal error: Uncaught Exception: Cannot open source device in php-src/test.php:5
Stack trace:
#0 php-src/test.php(5): Random\Engine\Secure->generate()
#1 {main}
Next RuntimeException: Random number generation failed in php-src/test.php:5
Stack trace:
#0 php-src/test.php(5): Random\Engine\Secure->generate()
#1 {main}
thrown in php-src/test.php on line 5
* Use `php_random_int_throw()` in Secure engine's range()
This exposes the underlying exception, improving debugging:
Exception: Cannot open source device in php-src/test.php:17
Stack trace:
#0 php-src/test.php(17): Random\Randomizer->getInt(1, 3)
#1 {main}
Next RuntimeException: Random number generation failed in php-src/test.php:17
Stack trace:
#0 php-src/test.php(17): Random\Randomizer->getInt(1, 3)
#1 {main}
* Throw exception when a user engine returns an empty string
This improves debugging, because the actual reason for the failure is available
as a previous Exception:
DomainException: The returned string must not be empty in php-src/test.php:17
Stack trace:
#0 php-src/test.php(17): Random\Randomizer->getBytes(123)
#1 {main}
Next RuntimeException: Random number generation failed in php-src/test.php:17
Stack trace:
#0 php-src/test.php(17): Random\Randomizer->getBytes(123)
#1 {main}
* Throw exception when the range selector fails to get acceptable numbers in 50 attempts
This improves debugging, because the actual reason for the failure is available
as a previous Exception:
RuntimeException: Failed to generate an acceptable random number in 50 attempts in php-src/test.php:17
Stack trace:
#0 php-src/test.php(17): Random\Randomizer->getInt(1, 3)
#1 {main}
Next RuntimeException: Random number generation failed in php-src/test.php:17
Stack trace:
#0 php-src/test.php(17): Random\Randomizer->getInt(1, 3)
#1 {main}
* Improve user_unsafe test
Select parameters for ->getInt() that will actually lead to unsafe behavior.
* Fix user_unsafe test
If an engine fails once it will be permanently poisoned by setting
`->last_unsafe`. This is undesirable for the test, because it skews the
results.
Fix this by creating a fresh engine for each "assertion".
* Remove duplication in user_unsafe.phpt
* Catch `Throwable` in user_unsafe.phpt
As we print the full stringified exception we implicitly assert the type of the
exception. No need to be overly specific in the catch block.
* Throw an error if an engine returns an empty string
* Throw an Error if range fails to find an acceptable number in 50 attempts
The previous shifting logic is problematic for two reasons:
1. It invokes undefined behavior when the `->last_generated_size` is at least
as large as the target integer in `result`, because the shift is larger than
the target integer. This was reported in GH-9083.
2. It expands the returned bytes in a big-endian fashion: Earlier bytes are
shifting into the most-significant position. As all the other logic in the
random extension treats byte-strings as little-endian numbers this is
inconsistent.
By fixing the second issue, we can implicitly fix the first one: Instead of
shifting the existing bits by the number of "newly added" bits, we shift the
newly added bits by the number of existing bits. As we stop requesting new bits
once the total_size reached the size of the target integer we can be sure to
never invoke undefined behavior during shifting.
The get_int_user.phpt test was adjusted to verify the little-endian behavior.
It generates a single byte per call and we expect the first byte generated to
appear at the start of the resulting number.
see GH-9056 for a previous fix in the same area.
Fixes GH-9083 which reports the undefined behavior.
Resolves GH-9085 which was an alternative attempt to fix GH-9083.
* Fix shift in rand_range??()
The last generated size is in bytes, whereas the shift is in bits. Multiple the
generated size by 8 to correctly handle each byte once.
* Correctly handle user engines returning less than 4 bytes in rand_rangeXX()
We need to loop until we accumulate sufficient bytes, instead of just checking
once. The version in the rejection loop was already correct.
* Clean up some repetition in rand_rangeXX()
