BookStack/app/Access/Oidc/OidcIdToken.php
2023-05-17 17:56:55 +01:00

228 lines
8.3 KiB
PHP

<?php
namespace BookStack\Access\Oidc;
class OidcIdToken
{
protected array $header;
protected array $payload;
protected string $signature;
protected string $issuer;
protected array $tokenParts = [];
/**
* @var array[]|string[]
*/
protected array $keys;
public function __construct(string $token, string $issuer, array $keys)
{
$this->keys = $keys;
$this->issuer = $issuer;
$this->parse($token);
}
/**
* Parse the token content into its components.
*/
protected function parse(string $token): void
{
$this->tokenParts = explode('.', $token);
$this->header = $this->parseEncodedTokenPart($this->tokenParts[0]);
$this->payload = $this->parseEncodedTokenPart($this->tokenParts[1] ?? '');
$this->signature = $this->base64UrlDecode($this->tokenParts[2] ?? '') ?: '';
}
/**
* Parse a Base64-JSON encoded token part.
* Returns the data as a key-value array or empty array upon error.
*/
protected function parseEncodedTokenPart(string $part): array
{
$json = $this->base64UrlDecode($part) ?: '{}';
$decoded = json_decode($json, true);
return is_array($decoded) ? $decoded : [];
}
/**
* Base64URL decode. Needs some character conversions to be compatible
* with PHP's default base64 handling.
*/
protected function base64UrlDecode(string $encoded): string
{
return base64_decode(strtr($encoded, '-_', '+/'));
}
/**
* Validate all possible parts of the id token.
*
* @throws OidcInvalidTokenException
*/
public function validate(string $clientId): bool
{
$this->validateTokenStructure();
$this->validateTokenSignature();
$this->validateTokenClaims($clientId);
return true;
}
/**
* Fetch a specific claim from this token.
* Returns null if it is null or does not exist.
*
* @return mixed|null
*/
public function getClaim(string $claim)
{
return $this->payload[$claim] ?? null;
}
/**
* Get all returned claims within the token.
*/
public function getAllClaims(): array
{
return $this->payload;
}
/**
* Replace the existing claim data of this token with that provided.
*/
public function replaceClaims(array $claims): void
{
$this->payload = $claims;
}
/**
* Validate the structure of the given token and ensure we have the required pieces.
* As per https://datatracker.ietf.org/doc/html/rfc7519#section-7.2.
*
* @throws OidcInvalidTokenException
*/
protected function validateTokenStructure(): void
{
foreach (['header', 'payload'] as $prop) {
if (empty($this->$prop) || !is_array($this->$prop)) {
throw new OidcInvalidTokenException("Could not parse out a valid {$prop} within the provided token");
}
}
if (empty($this->signature) || !is_string($this->signature)) {
throw new OidcInvalidTokenException('Could not parse out a valid signature within the provided token');
}
}
/**
* Validate the signature of the given token and ensure it validates against the provided key.
*
* @throws OidcInvalidTokenException
*/
protected function validateTokenSignature(): void
{
if ($this->header['alg'] !== 'RS256') {
throw new OidcInvalidTokenException("Only RS256 signature validation is supported. Token reports using {$this->header['alg']}");
}
$parsedKeys = array_map(function ($key) {
try {
return new OidcJwtSigningKey($key);
} catch (OidcInvalidKeyException $e) {
throw new OidcInvalidTokenException('Failed to read signing key with error: ' . $e->getMessage());
}
}, $this->keys);
$parsedKeys = array_filter($parsedKeys);
$contentToSign = $this->tokenParts[0] . '.' . $this->tokenParts[1];
/** @var OidcJwtSigningKey $parsedKey */
foreach ($parsedKeys as $parsedKey) {
if ($parsedKey->verify($contentToSign, $this->signature)) {
return;
}
}
throw new OidcInvalidTokenException('Token signature could not be validated using the provided keys');
}
/**
* Validate the claims of the token.
* As per https://openid.net/specs/openid-connect-basic-1_0.html#IDTokenValidation.
*
* @throws OidcInvalidTokenException
*/
protected function validateTokenClaims(string $clientId): void
{
// 1. The Issuer Identifier for the OpenID Provider (which is typically obtained during Discovery)
// MUST exactly match the value of the iss (issuer) Claim.
if (empty($this->payload['iss']) || $this->issuer !== $this->payload['iss']) {
throw new OidcInvalidTokenException('Missing or non-matching token issuer value');
}
// 2. The Client MUST validate that the aud (audience) Claim contains its client_id value registered
// at the Issuer identified by the iss (issuer) Claim as an audience. The ID Token MUST be rejected
// if the ID Token does not list the Client as a valid audience, or if it contains additional
// audiences not trusted by the Client.
if (empty($this->payload['aud'])) {
throw new OidcInvalidTokenException('Missing token audience value');
}
$aud = is_string($this->payload['aud']) ? [$this->payload['aud']] : $this->payload['aud'];
if (count($aud) !== 1) {
throw new OidcInvalidTokenException('Token audience value has ' . count($aud) . ' values, Expected 1');
}
if ($aud[0] !== $clientId) {
throw new OidcInvalidTokenException('Token audience value did not match the expected client_id');
}
// 3. If the ID Token contains multiple audiences, the Client SHOULD verify that an azp Claim is present.
// NOTE: Addressed by enforcing a count of 1 above.
// 4. If an azp (authorized party) Claim is present, the Client SHOULD verify that its client_id
// is the Claim Value.
if (isset($this->payload['azp']) && $this->payload['azp'] !== $clientId) {
throw new OidcInvalidTokenException('Token authorized party exists but does not match the expected client_id');
}
// 5. The current time MUST be before the time represented by the exp Claim
// (possibly allowing for some small leeway to account for clock skew).
if (empty($this->payload['exp'])) {
throw new OidcInvalidTokenException('Missing token expiration time value');
}
$skewSeconds = 120;
$now = time();
if ($now >= (intval($this->payload['exp']) + $skewSeconds)) {
throw new OidcInvalidTokenException('Token has expired');
}
// 6. The iat Claim can be used to reject tokens that were issued too far away from the current time,
// limiting the amount of time that nonces need to be stored to prevent attacks.
// The acceptable range is Client specific.
if (empty($this->payload['iat'])) {
throw new OidcInvalidTokenException('Missing token issued at time value');
}
$dayAgo = time() - 86400;
$iat = intval($this->payload['iat']);
if ($iat > ($now + $skewSeconds) || $iat < $dayAgo) {
throw new OidcInvalidTokenException('Token issue at time is not recent or is invalid');
}
// 7. If the acr Claim was requested, the Client SHOULD check that the asserted Claim Value is appropriate.
// The meaning and processing of acr Claim Values is out of scope for this document.
// NOTE: Not used for our case here. acr is not requested.
// 8. When a max_age request is made, the Client SHOULD check the auth_time Claim value and request
// re-authentication if it determines too much time has elapsed since the last End-User authentication.
// NOTE: Not used for our case here. A max_age request is not made.
// Custom: Ensure the "sub" (Subject) Claim exists and has a value.
if (empty($this->payload['sub'])) {
throw new OidcInvalidTokenException('Missing token subject value');
}
}
}