# k2gl/dsse

> Sign and verify DSSE envelopes (Dead Simple Signing Envelope) in PHP.

The signing envelope in-toto and Sigstore are built on — PAE encoding and ECDSA/Ed25519 signers included.

## Install

```bash
composer require k2gl/dsse
```

## Requirements

- PHP >=8.1

## Documentation

# k2gl/dsse

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Sign and verify DSSE (Dead Simple Signing Envelope) payloads in PHP with pluggable keys.
It's the envelope Sigstore, in-toto, SLSA and npm provenance use to wrap a signed payload.

It gives you the three pieces of the spec and nothing else:

- **PAE** — the exact, binary-safe byte string that gets signed.
- **Envelope** — the JSON envelope (`payload` / `payloadType` / `signatures`) with
  lossless (de)serialization.
- **Signer / Verifier** — tiny interfaces so you can plug in any key (or a remote
  KMS/HSM). ECDSA (P-256/384/521), Ed25519, and RSA (PKCS#1 v1.5) implementations are included.

## Install

```bash
composer require k2gl/dsse
```

Requires PHP 8.1+. The bundled signers use `ext-openssl` (ECDSA P-256/384/521, RSA) and
`ext-sodium` (Ed25519); both ship with PHP by default. The core (`Pae`, `Envelope`)
needs neither.

## Usage

### PAE — what actually gets signed

```php
use K2gl\Dsse\Pae;

Pae::encode('http://example.com/HelloWorld', 'hello world');
// "DSSEv1 29 http://example.com/HelloWorld 11 hello world"
```

Lengths are **byte** counts, so the encoding is unambiguous for any payload,
including binary data.

### Sign

```php
use K2gl\Dsse\Envelope;
use K2gl\Dsse\EcdsaP256Signer;

$signer   = EcdsaP256Signer::fromPem($privateKeyPem, keyId: 'k1');
$envelope = Envelope::sign('hello world', 'http://example.com/HelloWorld', $signer);

echo $envelope->toJson();
// {"payload":"aGVsbG8gd29ybGQ=","payloadType":"http://example.com/HelloWorld","signatures":[{"keyid":"k1","sig":"..."}]}
```

`Envelope::sign()` accepts several signers to produce a multi-signature envelope.

### Verify

```php
use K2gl\Dsse\Envelope;
use K2gl\Dsse\EcdsaP256Verifier;
use K2gl\Dsse\Exception\SignatureVerificationFailed;

$envelope = Envelope::fromJson($json);

try {
    $payload = $envelope->verify(EcdsaP256Verifier::fromPem($publicKeyPem));
    // $payload === 'hello world'
} catch (SignatureVerificationFailed) {
    // no signature matched any supplied verifier
}
```

The envelope is accepted if **any** signature verifies against **any** verifier you
pass, mirroring the spec's verification model. Pass several verifiers to accept a set
of trusted keys.

### Ed25519

```php
use K2gl\Dsse\Ed25519Signer;
use K2gl\Dsse\Ed25519Verifier;

$keypair  = sodium_crypto_sign_keypair();
$signer   = new Ed25519Signer(sodium_crypto_sign_secretkey($keypair), 'ed-1');
$verifier = new Ed25519Verifier(sodium_crypto_sign_publickey($keypair));
```

### ECDSA P-384 / P-521 and RSA

The other bundled algorithms follow the same `fromPem()` pattern:

```php
use K2gl\Dsse\EcdsaP384Signer;
use K2gl\Dsse\EcdsaP384Verifier;
use K2gl\Dsse\RsaSigner;
use K2gl\Dsse\RsaVerifier;

$signer   = EcdsaP384Signer::fromPem($p384PrivateKeyPem);
$verifier = EcdsaP384Verifier::fromPem($p384PublicKeyPem);

// RSASSA-PKCS1-v1_5; hash algorithm defaults to sha256 (sha384/sha512 also supported)
$rsaSigner   = RsaSigner::fromPem($rsaPrivateKeyPem, hashAlgorithm: 'sha512');
$rsaVerifier = RsaVerifier::fromPem($rsaPublicKeyPem, hashAlgorithm: 'sha512');
```

`EcdsaP521Signer` / `EcdsaP521Verifier` work identically.

### Loading a key without knowing its algorithm

When a key arrives as a PEM file or a JWK from a JWKS endpoint, `PublicKey` picks the
right verifier for you — RSA, ECDSA (P-256/384/521) or Ed25519 — so you don't have to
branch on the algorithm yourself:

```php
use K2gl\Dsse\PublicKey;

$verifier = PublicKey::fromPem($publicKeyPem); // detects the algorithm and curve
$verifier = PublicKey::fromJwk($jwk);          // EC / RSA / OKP (Ed25519)

$payload = $envelope->verify($verifier);
```

RSA keys carry no hash, so these verify with SHA-256; for another hash use
`RsaVerifier::fromPem($pem, hashAlgorithm: 'sha512')` directly.

`KeyId` computes the two identifiers commonly used for a signature's `keyId`:

```php
use K2gl\Dsse\KeyId;

KeyId::sha256Spki($publicKeyPem); // hex SHA-256 of the DER key (cosign / Sigstore style)
KeyId::jwkThumbprint($jwk);       // RFC 7638 base64url thumbprint
```

### Plugging in your own key backend

Implement two methods to sign with a KMS/HSM or any other scheme:

```php
use K2gl\Dsse\Signer;

final class KmsSigner implements Signer
{
    public function sign(string $message): string { /* sign PAE bytes, return raw signature */ }
    public function keyId(): ?string { return 'arn:aws:kms:...'; }
}
```

## Design

- **Crypto-agnostic core.** `Pae` and `Envelope` carry no cryptography; signing is
  delegated to `Signer` / `Verifier`, so you control the algorithm and key storage.
- **Raw signatures.** The bundled ECDSA signers emit raw `r||s` signatures (64/96/132 bytes for P-256/384/521)
  (the form DSSE/JOSE/WebCrypto/Sigstore use), converting to and from OpenSSL's DER
  internally. The verifier accepts both raw `r||s` and ASN.1 DER signatures,
  detecting the encoding automatically — so DER signatures (OpenSSL native, Sigstore
  bundles) verify without any extra wiring.
- **Strict and typed.** `declare(strict_types=1)` throughout, analysed at PHPStan
  level 9; every exception implements `DsseException`.

## License

MIT — see [LICENSE](LICENSE).

Based on the DSSE specification (Apache-2.0) by the Secure Systems Lab; this is an
independent, clean-room PHP implementation.

## API

### K2gl\Dsse\EcdsaP256Signer (class)

- `fromPem(string $pem, ?string $keyId = null): self`
- `sign(string $message): string`
- `keyId(): ?string`

### K2gl\Dsse\EcdsaP256Verifier (class)

- `fromPem(string $pem): self`
- `verify(string $message, string $signature): bool`

### K2gl\Dsse\EcdsaP384Signer (class)

- `fromPem(string $pem, ?string $keyId = null): self`
- `sign(string $message): string`
- `keyId(): ?string`

### K2gl\Dsse\EcdsaP384Verifier (class)

- `fromPem(string $pem): self`
- `verify(string $message, string $signature): bool`

### K2gl\Dsse\EcdsaP521Signer (class)

- `fromPem(string $pem, ?string $keyId = null): self`
- `sign(string $message): string`
- `keyId(): ?string`

### K2gl\Dsse\EcdsaP521Verifier (class)

- `fromPem(string $pem): self`
- `verify(string $message, string $signature): bool`

### K2gl\Dsse\Ed25519Signer (class)

- `__construct( private readonly string $secretKey, private readonly ?string $keyId = null, )`
- `sign(string $message): string`
- `keyId(): ?string`

### K2gl\Dsse\Ed25519Verifier (class)

- `__construct(private readonly string $publicKey)`
- `verify(string $message, string $signature): bool`

### K2gl\Dsse\Envelope (class)

- `__construct( public readonly string $payload, public readonly string $payloadType, public readonly array $signatures, )`
- `pae(): string`
- `sign(string $payload, string $payloadType, Signer ...$signers): self`
- `verify(Verifier ...$verifiers): string`
- `fromJson(string $json): self`
- `fromArray(array $data): self`
- `toArray(): array`
- `toJson(): string`

### K2gl\Dsse\Exception\CryptoException (class)

_no public methods_

### K2gl\Dsse\Exception\DsseException (interface)

_no public methods_

### K2gl\Dsse\Exception\InvalidEnvelopeException (class)

_no public methods_

### K2gl\Dsse\Exception\SignatureVerificationFailed (class)

_no public methods_

### K2gl\Dsse\KeyId (class)

- `sha256Spki(string $publicKeyPem): string`
- `jwkThumbprint(array $jwk): string`

### K2gl\Dsse\Pae (class)

- `encode(string $payloadType, string $payload): string`

### K2gl\Dsse\PublicKey (class)

- `fromPem(string $pem): Verifier`
- `fromJwk(array $jwk): Verifier`

### K2gl\Dsse\RsaSigner (class)

- `fromPem(string $pem, ?string $keyId = null, string $hashAlgorithm = 'sha256'): self`
- `sign(string $message): string`
- `keyId(): ?string`

### K2gl\Dsse\RsaVerifier (class)

- `fromPem(string $pem, string $hashAlgorithm = 'sha256'): self`
- `verify(string $message, string $signature): bool`

### K2gl\Dsse\Signature (class)

- `__construct( public readonly string $sig, public readonly ?string $keyId = null, )`

### K2gl\Dsse\Signer (interface)

- `sign(string $message): string`
- `keyId(): ?string`

### K2gl\Dsse\Verifier (interface)

- `verify(string $message, string $signature): bool`

## Links

- GitHub: https://github.com/k2gl/dsse
- Packagist: https://packagist.org/packages/k2gl/dsse