README

A PHP Framework that allows you to encode and decode arbitrary ASN.1 structures using the ITU-T X.690 Encoding Rules. This encoding is very frequently used in X.509 PKI environments or the communication between heterogeneous computer systems.

The API allows you to encode ASN.1 structures to create binary data such as certificate signing requests (CSR), X.509 certificates or certificate revocation lists (CRL). PHPASN1 can also read BER encoded binary data into separate PHP objects that can be manipulated by the user and reencoded afterwards.

Unlike the original fgrosse/PHPASN1 library, this library can:

decode BER data that uses indefinite length encoding
modify the structure of decoded ASN.1 objects (add, replace or remove nested elements) and encode them again

The changelog can now be found at CHANGELOG.md.

Dependencies

PHPASN1 requires at least PHP 8.1.

It is strongly recommended to install the gmp extension, which is significantly faster for big integer arithmetic. If the extension is not available, the pure PHP adapik/gmp-polyfill (installed automatically via Composer) is used instead. The polyfill should only be relied on in environments where installing the extension is not possible, or for demonstration purposes.

If you have the extension installed, you can avoid downloading the polyfill by excluding it in the composer.json of your project using the replace section:

{
    "replace": {
        "adapik/gmp-polyfill": "*"
    }
}

Installation

The preferred way to install this library is to rely on Composer:

$ composer require adapik/phpasn1

Usage

Encoding ASN.1 Structures

PHPASN1 offers you a class for each of the implemented ASN.1 universal types. The constructors should be pretty self explanatory so you should have no big trouble getting started. All data will be encoded using DER encoding

use FG\ASN1\Universal\Integer;
use FG\ASN1\Universal\Boolean;
use FG\ASN1\Universal\Enumerated;
use FG\ASN1\Universal\IA5String;
use FG\ASN1\Universal\ObjectIdentifier;
use FG\ASN1\Universal\PrintableString;
use FG\ASN1\Universal\Sequence;
use FG\ASN1\Universal\Set;
use FG\ASN1\Universal\NullObject;

$integer = Integer::create(123456);        
$boolean = Boolean::create(true);
$enum = Enumerated::create(1);

$asnNull = NullObject::create();
$objectIdentifier1 = ObjectIdentifier('1.2.250.1.16.9');
$printableString = PrintableString::createFromString('Foo bar');

$sequence = Sequence::create([$integer, $boolean, $enum, $ia5String]);
$set = Set([$sequence, $asnNull, $objectIdentifier1, $objectIdentifier2, $printableString]);

$myBinary  = $sequence->getBinary();
$myBinary .= $set->getBinary();

echo base64_encode($myBinary);

Decoding binary data

Decoding BER encoded binary data is just as easy as encoding it:

use FG\ASN1\Object;

$base64String = ...
$binaryData = base64_decode($base64String);        
$asnObject = Object::fromBinary($binaryData);
// do stuff

You can use this function to make sure your data has exactly the format you are expecting.

Thanks

To all contributors so far!

License

This library is distributed under the MIT License.

adapik / phpasn1

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