<?php
declare(strict_types=1);
namespace ParagonIE\Blakechain;
use ParagonIE_Sodium_Compat as SodiumCompat;
use ParagonIE\ConstantTime\Base64UrlSafe;
/**
* Class Verifier
* @package ParagonIE\Blakechain
*/
class Verifier
{
const FINAL_HASH_MISMATCH = 'The final hash for this Blakechain does not match what was expected';
const HASH_DOES_NOT_MATCH = 'The hash for this item does not match its contents';
const PREV_DOES_NOT_MATCH = 'The previous hash for this item does not match the previous hash';
/**
* @var array
*/
protected $lastErrorData = [];
/**
* @return array
*/
public function getLastError(): array
{
return $this->lastErrorData;
}
/**
* Walk down the entire chain, recalculate the final hash, then
* verify that it matches what we expect.
*
* @param Blakechain $chain
* @param string $lastHash
* @return bool
*
* @throws \SodiumException
*/
public function verifyLastHash(
Blakechain $chain,
string $lastHash
): bool {
/**
* @var array<int, Node> $nodes
*/
$nodes = $chain->getNodes();
$count = \count($nodes);
$prevHash = '';
for ($i = 0; $i < $count; ++$i) {
/** @var Node $curr */
$curr = $nodes[$i];
$actualHash = SodiumCompat::crypto_generichash(
$curr->getData(),
$prevHash
);
if (!\hash_equals($actualHash, $curr->getHash(true))) {
$this->lastErrorData = [
'index' => $i,
'item' => [
'prev' => $curr->getPrevHash(),
'data' => $curr->getData(),
'hash' => $curr->getHash()
],
'failure' => static::HASH_DOES_NOT_MATCH
];
return false;
}
$prevHash = $curr->getHash(true);
}
$decoded = Base64UrlSafe::decode($lastHash);
if (!\hash_equals($prevHash, $decoded)) {
$this->lastErrorData = [
'item' => null,
'expected' => $lastHash,
'calculated' => Base64UrlSafe::encode($prevHash),
'failure' => static::FINAL_HASH_MISMATCH
];
return false;
}
return true;
}
/**
* This is a self-consistency check for a subset of a Blakechain.
*
* @param Blakechain $chain
* @param int $offset
* @param int $limit
* @return bool
*
* @throws \SodiumException
*/
public function verifySequenceHashes(
Blakechain $chain,
int $offset = 0,
int $limit = PHP_INT_MAX
): bool {
$subchain = $chain->getPartialChain($offset, $limit);
/** @var string $prev */
$prev = '';
/**
* @var int $idx
* @var array<string, string> $item
*/
foreach ($subchain as $idx => $item) {
$prevHash = Base64UrlSafe::decode($item['prev']);
$storedHash = Base64UrlSafe::decode($item['hash']);
$actualHash = SodiumCompat::crypto_generichash(
$item['data'],
$prevHash
);
if (!\hash_equals($actualHash, $storedHash)) {
$this->lastErrorData = [
'index' => $idx,
'item' => $item,
'failure' => static::HASH_DOES_NOT_MATCH
];
return false;
}
if (!empty($prev)) {
if (!\hash_equals($prev, $item['prev'])) {
$this->lastErrorData = [
'index' => $idx,
'prev' => $prev,
'item' => $item,
'failure' => static::PREV_DOES_NOT_MATCH
];
return false;
}
}
/** @var string $prev */
$prev = $item['hash'];
}
return true;
}
}
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