fix: cache jwks as string in CachedKeySet (#435)

Author: brandomeniconi

src/CachedKeySet.php

@@ -132,13 +132,13 @@ public function offsetUnset($offset): void
 
     private function keyIdExists(string $keyId): bool
     {
-        $keySetToCache = null;
         if (null === $this->keySet) {
             $item = $this->getCacheItem();
             // Try to load keys from cache
             if ($item->isHit()) {
                 // item found! Return it
-                $this->keySet = $item->get();
+                $jwks = $item->get();
+                $this->keySet = JWK::parseKeySet(json_decode($jwks, true), $this->defaultAlg);
             }
         }
 
@@ -148,17 +148,15 @@ private function keyIdExists(string $keyId): bool
             }
             $request = $this->httpFactory->createRequest('get', $this->jwksUri);
             $jwksResponse = $this->httpClient->sendRequest($request);
-            $jwks = json_decode((string) $jwksResponse->getBody(), true);
-            $this->keySet = $keySetToCache = JWK::parseKeySet($jwks, $this->defaultAlg);
+            $jwks = (string) $jwksResponse->getBody();
+            $this->keySet = JWK::parseKeySet(json_decode($jwks, true), $this->defaultAlg);
 
             if (!isset($this->keySet[$keyId])) {
                 return false;
             }
-        }
 
-        if ($keySetToCache) {
             $item = $this->getCacheItem();
-            $item->set($keySetToCache);
+            $item->set($jwks);
             if ($this->expiresAfter) {
                 $item->expiresAfter($this->expiresAfter);
             }

tests/CachedKeySetTest.php

@@ -117,7 +117,7 @@ public function testKeyIdIsCached()
         $cacheItem->isHit()
             ->willReturn(true);
         $cacheItem->get()
-            ->willReturn(JWK::parseKeySet(json_decode($this->testJwks1, true)));
+            ->willReturn($this->testJwks1);
 
         $cache = $this->prophesize(CacheItemPoolInterface::class);
         $cache->getItem($this->testJwksUriKey)
@@ -143,7 +143,7 @@ public function testCachedKeyIdRefresh()
             ->willReturn(true);
         $cacheItem->get()
             ->shouldBeCalledOnce()
-            ->willReturn(JWK::parseKeySet(json_decode($this->testJwks1, true)));
+            ->willReturn($this->testJwks1);
         $cacheItem->set(Argument::any())
             ->shouldBeCalledOnce()
             ->will(function () {
@@ -217,9 +217,8 @@ public function testJwtVerify()
         $cacheItem->isHit()
             ->willReturn(true);
         $cacheItem->get()
-            ->willReturn(JWK::parseKeySet(
-                json_decode(file_get_contents(__DIR__ . '/data/rsa-jwkset.json'), true)
-            ));
+            ->willReturn(file_get_contents(__DIR__ . '/data/rsa-jwkset.json')
+            );
 
         $cache = $this->prophesize(CacheItemPoolInterface::class);
         $cache->getItem($this->testJwksUriKey)