351 lines
13 KiB
PHP
351 lines
13 KiB
PHP
<?php declare(strict_types=1);
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/*
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* This file is part of the Monolog package.
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*
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* (c) Jordi Boggiano <j.boggiano@seld.be>
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*
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* For the full copyright and license information, please view the LICENSE
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* file that was distributed with this source code.
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*/
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namespace Monolog\Formatter;
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use Monolog\LogRecord;
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use Monolog\Utils;
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/**
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* Wraps another formatter to redact sensitive data from log records.
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*
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* It works in three passes so that it can mask secrets wherever they end up:
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*
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* - Before delegating, it masks the value of any context/extra key whose name
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* matches one of the configured sensitive keys (case-insensitive, recursive).
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* - After delegating, it removes those same secret values from the wrapped
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* formatter's output, which catches the copies masking the record cannot
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* reach, e.g. a secret interpolated into the message by the
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* PsrLogMessageProcessor or embedded in an exception message.
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* - Last, it runs the configured regex patterns over the output, which catches
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* secrets that only became strings once the inner formatter normalized
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* objects (e.g. tokens buried in an exception stack trace). If a pattern
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* cannot be applied, the record is dropped instead of emitted unredacted.
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*
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* On top of the sensitive keys, secrets are also read from the properties of the
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* objects in the record matching a constructor parameter marked
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* #[SensitiveParameter]. Those can only be handled by the output pass, as the
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* objects carrying them cannot be modified. This is the one part that reflects on
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* every logged object, so it can be turned off with $redactSensitiveParameters.
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*
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* Only string and array output can be swept, so wrapping a formatter which returns
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* objects (e.g. the ElasticaFormatter) leaves you with the key masking alone.
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*
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* Because it is a formatter rather than a processor, it is guaranteed to run
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* after every processor (both Logger- and Handler-level), so it always sees the
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* final record with all data at hand.
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*
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* @author Jordi Boggiano <j.boggiano@seld.be>
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*/
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final class RedactingFormatter implements WrappingFormatterInterface
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{
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/**
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* Matches long token-like words (30+ alphanumerics, optionally prefixed like api_key_),
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* which are very likely to be secrets/tokens. Provided as an opt-in pattern as it may
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* cause collateral damage on legitimate long strings (hashes, UUIDs, base64, ...).
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*/
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public const TOKEN_PATTERN = '{\b(?:[a-z]+_)*[a-zA-Z0-9]{30,}\b}';
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/**
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* How deep to walk the record and the output, mirrors NormalizerFormatter's default
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*/
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private const MAX_DEPTH = 9;
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/** @var list<string> Lowercased sensitive keys */
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private array $sensitiveKeys;
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/** @var list<string> */
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private array $patterns;
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/** @var array<class-string, array<string, \ReflectionProperty>> */
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private array $sensitiveProperties = [];
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/**
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* @param FormatterInterface $formatter The formatter to wrap and whose output gets redacted
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* @param list<string> $sensitiveKeys Exact context/extra keys whose values to mask (case-insensitive)
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* @param list<string> $patterns PCRE patterns to mask in the formatted output (e.g. self::TOKEN_PATTERN)
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* @param string $mask Replacement token
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* @param bool $redactSensitiveParameters Whether to also read secrets off the properties matching a
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* #[SensitiveParameter] constructor parameter, which requires
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* walking and reflecting on every object in the record
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* @param int $minSecretLength Minimum length a secret must have to be removed from the
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* output, to avoid short values like "pass" redacting
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* unrelated data
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*
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* @throws \InvalidArgumentException If a pattern is not a valid PCRE regex
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*/
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public function __construct(
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private readonly FormatterInterface $formatter,
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array $sensitiveKeys = ['password', 'passwd', 'pwd', 'secret', 'token', 'api_key', 'apikey', 'authorization', 'auth', 'cookie'],
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array $patterns = [],
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private readonly string $mask = '[REDACTED]',
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private readonly bool $redactSensitiveParameters = true,
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private readonly int $minSecretLength = 5,
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) {
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$this->sensitiveKeys = array_values(array_map('strtolower', $sensitiveKeys));
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foreach ($patterns as $pattern) {
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if (@preg_match($pattern, '') === false) {
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throw new \InvalidArgumentException(sprintf('Invalid redaction pattern provided to RedactingFormatter: %s', var_export($pattern, true)));
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}
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}
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$this->patterns = array_values($patterns);
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}
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public function getWrappedFormatter(): FormatterInterface
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{
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return $this->formatter;
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}
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public function format(LogRecord $record)
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{
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// secrets must be collected before the keys get masked, as masking loses the values
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$secrets = $this->collectSecrets([$record]);
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return $this->sweep($this->formatter->format($this->redactRecord($record)), $secrets);
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}
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public function formatBatch(array $records)
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{
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$secrets = $this->collectSecrets($records);
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foreach ($records as $key => $record) {
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$records[$key] = $this->redactRecord($record);
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}
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return $this->sweep($this->formatter->formatBatch($records), $secrets);
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}
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private function redactRecord(LogRecord $record): LogRecord
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{
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return $record->with(
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context: $this->redactKeys($record->context),
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extra: $this->redactKeys($record->extra),
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);
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}
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/**
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* @param array<mixed> $data
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* @return array<mixed>
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*/
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private function redactKeys(array $data, int $depth = 0): array
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{
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// context comes from userland and can hold a self-referencing array
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if ($depth > self::MAX_DEPTH) {
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return $data;
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}
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foreach ($data as $key => $value) {
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if (\is_string($key) && \in_array(strtolower($key), $this->sensitiveKeys, true)) {
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$data[$key] = $this->mask;
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} elseif (\is_array($value)) {
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$data[$key] = $this->redactKeys($value, $depth + 1);
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}
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}
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return $data;
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}
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/**
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* Gathers the secret values present in the given records, longest first
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*
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* @param iterable<LogRecord> $records
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* @return list<string>
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*/
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private function collectSecrets(iterable $records): array
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{
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$secrets = [];
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$seen = [];
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foreach ($records as $record) {
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$this->collect($record->context, $secrets, $seen, 0);
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$this->collect($record->extra, $secrets, $seen, 0);
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}
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if ([] === $secrets) {
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return [];
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}
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// a secret containing quotes/backslashes/newlines shows up escaped in json output,
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// so both forms have to be looked for
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$escapedSecrets = [];
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foreach ($secrets as $secret) {
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$escaped = substr(Utils::jsonEncode($secret, null, true), 1, -1);
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if ($escaped !== $secret && $escaped !== '') {
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$escapedSecrets[] = $escaped;
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}
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}
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$secrets = array_values(array_unique(array_merge($secrets, $escapedSecrets)));
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// longest first, so that overlapping secrets do not leave fragments behind
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usort($secrets, static fn (string $a, string $b) => \strlen($b) <=> \strlen($a));
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return $secrets;
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}
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/**
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* @param list<string> $secrets
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* @param array<int, true> $seen Ids of the objects visited so far, to survive cyclic graphs
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*/
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private function collect(mixed $data, array &$secrets, array &$seen, int $depth): void
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{
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if ($depth > self::MAX_DEPTH) {
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return;
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}
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if (\is_array($data)) {
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foreach ($data as $key => $value) {
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if (\is_string($key) && \in_array(strtolower($key), $this->sensitiveKeys, true)) {
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// no need to recurse, the whole value is masked in the record anyway
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$this->addSecret($value, $secrets);
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continue;
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}
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$this->collect($value, $secrets, $seen, $depth + 1);
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}
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return;
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}
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// the array walk above is essentially free, reflecting on objects is not
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if (!\is_object($data) || !$this->redactSensitiveParameters) {
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return;
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}
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$id = spl_object_id($data);
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if (isset($seen[$id])) {
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return;
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}
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$seen[$id] = true;
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foreach ($this->getSensitiveProperties($data) as $property) {
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if ($property->isInitialized($data)) {
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$this->addSecret($property->getValue($data), $secrets);
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}
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}
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// public properties only, matching what formatters get to see, but enough to reach
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// objects nested inside this one
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foreach (get_object_vars($data) as $value) {
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$this->collect($value, $secrets, $seen, $depth + 1);
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}
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}
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/**
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* Reflects the properties of an object matching a #[SensitiveParameter] constructor parameter
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*
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* Non-public properties are included as they can still leak through __toString(), and the
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* result is cached per class as reflecting on every logged object would be far too costly.
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*
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* @return array<string, \ReflectionProperty>
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*/
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private function getSensitiveProperties(object $data): array
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{
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$class = $data::class;
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if (isset($this->sensitiveProperties[$class])) {
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return $this->sensitiveProperties[$class];
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}
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$names = Utils::getSensitiveParameterNames($class);
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// PHP 8.2+ wraps the arguments it hides from stack traces in a SensitiveParameterValue,
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// whose own constructor parameter is not marked. Matched by name and read as a property
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// so that it does not matter whether symfony/polyfill-php82 is installed on PHP 8.1:
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// naming the class makes PHPStan report either the @internal getValue() the polyfill
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// inherits, or a missing class when it is absent.
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if ('SensitiveParameterValue' === $class) {
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$names['value'] = true;
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}
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$properties = [];
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foreach ($names as $name => $_) {
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// walking up is required as a private property of a parent class is not
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// reachable through the child's ReflectionClass
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for ($reflection = new \ReflectionClass($class); false !== $reflection; $reflection = $reflection->getParentClass()) {
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if ($reflection->hasProperty($name)) {
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$properties[$name] = $reflection->getProperty($name);
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break;
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}
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}
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}
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return $this->sensitiveProperties[$class] = $properties;
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}
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/**
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* @param list<string> $secrets
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*/
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private function addSecret(mixed $value, array &$secrets): void
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{
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// a Stringable secret ends up in the output as its string form, so that is what
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// has to be looked for
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if ($value instanceof \Stringable) {
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try {
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$value = $value->__toString();
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} catch (\Throwable) {
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return;
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}
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}
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// ints/floats are left out on purpose, sweeping a digit run out of the output
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// would silently corrupt unrelated data
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if (\is_string($value) && $value !== '' && \strlen($value) >= $this->minSecretLength) {
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$secrets[] = $value;
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}
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}
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/**
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* Removes the collected secrets and applies the configured patterns to the formatter output,
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* recursing into arrays to support formatters that do not return a string (e.g. MongoDBFormatter).
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*
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* @param list<string> $secrets
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*/
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private function sweep(mixed $formatted, array $secrets, int $depth = 0): mixed
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{
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if ([] === $this->patterns && [] === $secrets) {
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return $formatted;
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}
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// deeper than any formatter will render anyway, and a custom one may well
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// hand back a self-referencing array
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if ($depth > self::MAX_DEPTH) {
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return $formatted;
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}
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if (\is_string($formatted)) {
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if ([] !== $secrets) {
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$formatted = str_replace($secrets, $this->mask, $formatted);
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}
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if ([] !== $this->patterns) {
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$replaced = preg_replace($this->patterns, $this->mask, $formatted);
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if (null === $replaced) {
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// the patterns could not be applied so the output cannot be trusted, drop it
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// entirely. Neither the patterns (which may embed a secret themselves) nor the
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// mask are reported, preg_last_error_msg() is one of a fixed set of PCRE strings
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return '[RedactingFormatter dropped this record, pattern redaction failed with "'.preg_last_error_msg().'"]';
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}
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$formatted = $replaced;
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}
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return $formatted;
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}
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if (\is_array($formatted)) {
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foreach ($formatted as $key => $value) {
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$formatted[$key] = $this->sweep($value, $secrets, $depth + 1);
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}
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}
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return $formatted;
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}
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}
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