random_compat
PHP 5.x polyfill for random_bytes() and random_int() created and maintained
by Paragon Initiative Enterprises.
Although this library should function in earlier versions of PHP, we will only
consider issues relevant to supported PHP versions.
If you are using an unsupported version of PHP, please upgrade as soon as possible.
Important
Although this library has been examined by some security experts in the PHP
community, there will always be a chance that we overlooked something. Please
ask your favorite trusted hackers to hammer it for implementation errors and
bugs before even thinking about deploying it in production.
Do not use the master branch, use a stable release.
For the background of this library, please refer to our blog post on
Generating Random Integers and Strings in PHP.
Usability Notice
If PHP cannot safely generate random data, this library will throw an Exception.
It will never fall back to insecure random data. If this keeps happening, upgrade
to a newer version of PHP immediately.
Installing
With Composer:
composer require paragonie/random_compat
Signed PHP Archive:
As of version 1.2.0, we also ship an ECDSA-signed PHP Archive with each stable
release on Github.
- Download the
.phar, .phar.pubkey, and .phar.pubkey.asc files.
- (Recommended but not required) Verify the PGP signature of
.phar.pubkey
(contained within the .asc file) using the PGP public key for Paragon Initiative Enterprises.
- Extract both
.phar and .phar.pubkey files to the same directory.
require_once "/path/to/random_compat.phar";- When a new version is released, you only need to replace the
.phar file;
the .pubkey will not change (unless our signing key is ever compromised).
Manual Installation:
- Download a stable release.
- Extract the files into your project.
require_once "/path/to/random_compat/lib/random.php";
Usage
This library exposes the CSPRNG functions added in PHP 7
for use in PHP 5 projects. Their behavior should be identical.
Generate a string of random bytes
try {
$string = random_bytes(32);
} catch (TypeError $e) {
// Well, it's an integer, so this IS unexpected.
die("An unexpected error has occurred");
} catch (Error $e) {
// This is also unexpected because 32 is a reasonable integer.
die("An unexpected error has occurred");
} catch (Exception $e) {
// If you get this message, the CSPRNG failed hard.
die("Could not generate a random string. Is our OS secure?");
}
var_dump(bin2hex($string));
// string(64) "5787c41ae124b3b9363b7825104f8bc8cf27c4c3036573e5f0d4a91ad2eeac6f"
Generate a random integer between two given integers (inclusive)
try {
$int = random_int(0,255);
} catch (TypeError $e) {
// Well, it's an integer, so this IS unexpected.
die("An unexpected error has occurred");
} catch (Error $e) {
// This is also unexpected because 0 and 255 are both reasonable integers.
die("An unexpected error has occurred");
} catch (Exception $e) {
// If you get this message, the CSPRNG failed hard.
die("Could not generate a random string. Is our OS secure?");
}
var_dump($int);
// int(47)
Exception handling
When handling exceptions and errors you must account for differences between
PHP 5 and PHP7.
The differences:
- Catching
Error works, so long as it is caught before Exception.
- Catching
Exception has different behavior, without previously catching Error.
- There is no portable way to catch all errors/exceptions.
Our recommendation
Always catch Error before Exception.
Example
try {
return random_int(1, $userInput);
} catch (TypeError $e) {
// This is okay, so long as `Error` is caught before `Exception`.
throw new Exception('Please enter a number!');
} catch (Error $e) {
// This is required, if you do not need to do anything just rethrow.
throw $e;
} catch (Exception $e) {
// This is optional and maybe omitted if you do not want to handle errors
// during generation.
throw new InternalServerErrorException(
'Oops, our server is bust and cannot generate any random data.',
500,
$e
);
}
Contributors
This project would not be anywhere near as excellent as it is today if it
weren't for the contributions of the following individuals: