# random_compat

[![Build Status](https://travis-ci.org/paragonie/random_compat.svg?branch=master)](https://travis-ci.org/paragonie/random_compat)
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PHP 5.x polyfill for `random_bytes()` and `random_int()` created and maintained
by [Paragon Initiative Enterprises](https://paragonie.com).

Although this library *should* function in earlier versions of PHP, we will only
consider issues relevant to [supported PHP versions](https://secure.php.net/supported-versions.php).
**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](https://github.com/paragonie/random_compat/releases/latest).**

For the background of this library, please refer to our blog post on 
[Generating Random Integers and Strings in PHP](https://paragonie.com/blog/2015/07/how-safely-generate-random-strings-and-integers-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.

## Usage

This library exposes the [CSPRNG functions added in PHP 7](https://secure.php.net/manual/en/ref.csprng.php)
for use in PHP 5 projects. Their behavior should be identical.

### Generate a string of random bytes

```php
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)

```php
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`.
* Catching `Throwable` does *not* work the same between PHP5 and PHP7.
* There is *no* portable way to catch all errors/exceptions.

#### Our recommendation

**Always** catch `Error` before `Exception`, **do not** catch `Throwable`.

#### Example

```php
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:

* [@AndrewCarterUK (Andrew Carter)](https://github.com/AndrewCarterUK)
* [@asgrim (James Titcumb)](https://github.com/asgrim)
* [@CodesInChaos (Christian Winnerlein)](https://github.com/CodesInChaos)
* [@chriscct7 (Chris Christoff)](https://github.com/chriscct7)
* [@cs278 (Chris Smith)](https://github.com/cs278)
* [@cweagans (Cameron Eagans)](https://github.com/cweagans)
* [@dd32 (Dion Hulse)](https://github.com/dd32)
* [@geggleto (Glenn Eggleton)](https://github.com/geggleto)
* [@ircmaxell (Anthony Ferrara)](https://github.com/ircmaxell)
* [@jedisct1 (Frank Denis)](https://github.com/jedisct1)
* [@juliangut (Julián Gutiérrez)](https://github.com/juliangut)
* [@kelunik (Niklas Keller)](https://github.com/kelunik)
* [@lt (Leigh)](https://github.com/lt)
* [@MasonM (Mason Malone)](https://github.com/MasonM)
* [@mmeyer2k (Michael M)](https://github.com/mmeyer2k)
* [@narfbg (Andrey Andreev)](https://github.com/narfbg)
* [@oittaa](https://github.com/oittaa)
* [@redragonx (Stephen Chavez)](https://github.com/redragonx)
* [@rchouinard (Ryan Chouinard)](https://github.com/rchouinard)
* [@SammyK (Sammy Kaye Powers)](https://github.com/SammyK)
* [@scottchiefbaker (Scott Baker)](https://github.com/scottchiefbaker)
* [@skyosev (Stoyan Kyosev)](https://github.com/skyosev)
* [@stof (Christophe Coevoet)](https://github.com/stof)
* [@teohhanhui (Teoh Han Hui)](https://github.com/teohhanhui)
* [@tom-- (Tom Worster)](https://github.com/tom--)
* [@tsyr2ko](https://github.com/tsyr2ko)
* [@trowski (Aaron Piotrowski)](https://github.com/trowski)
* [@twistor (Chris Lepannen)](https://github.com/twistor)
* [@voku (Lars Moelleken)](https://github.com/voku)
* [@xabbuh (Christian Flothmann)](https://github.com/xabbuh)
