diff --git a/.gitattributes b/.gitattributes
index d85a794e..24a9c15e 100644
--- a/.gitattributes
+++ b/.gitattributes
@@ -10,4 +10,5 @@
 /phpunit.xml.dist export-ignore
 /CHANGELOG.md export-ignore
 /CONTRIBUTING.md export-ignore
-/README.md export-ignore
\ No newline at end of file
+/README.md export-ignore
+
diff --git a/README.md b/README.md
index 7f421104..28047d6b 100644
--- a/README.md
+++ b/README.md
@@ -62,9 +62,7 @@ Bugs and feature request are tracked on [GitHub](https://github.com/thephpleague
 
 If you have any questions about OAuth _please_ open a ticket here; please **don't** email the address below.
 
-<a target='_blank' rel='nofollow' href='https://app.codesponsor.io/link/N2YMJcLBppt2Eg9E1jGu4gef/thephpleague/oauth2-server'>
-  <img alt='Sponsor' width='888' height='68' src='https://app.codesponsor.io/embed/N2YMJcLBppt2Eg9E1jGu4gef/thephpleague/oauth2-server.svg' />
-</a>
+
 
 ## Commercial Support
 
diff --git a/src/CryptKey.php b/src/CryptKey.php
index 2ede9e33..0d5f5cf6 100644
--- a/src/CryptKey.php
+++ b/src/CryptKey.php
@@ -14,7 +14,7 @@ namespace League\OAuth2\Server;
 class CryptKey
 {
     const RSA_KEY_PATTERN =
-        '/^(-----BEGIN (RSA )?(PUBLIC|PRIVATE) KEY-----\n)(.|\n)+(-----END (RSA )?(PUBLIC|PRIVATE) KEY-----)$/';
+        '/^(-----BEGIN (RSA )?(PUBLIC|PRIVATE) KEY-----)\R.*(-----END (RSA )?(PUBLIC|PRIVATE) KEY-----)\R?$/s';
 
     /**
      * @var string
diff --git a/src/Grant/AuthCodeGrant.php b/src/Grant/AuthCodeGrant.php
index e974ded1..122edf00 100644
--- a/src/Grant/AuthCodeGrant.php
+++ b/src/Grant/AuthCodeGrant.php
@@ -153,7 +153,7 @@ class AuthCodeGrant extends AbstractAuthorizeGrant
                 case 'S256':
                     if (
                         hash_equals(
-                            hash('sha256', strtr(rtrim(base64_encode($codeVerifier), '='), '+/', '-_')),
+                            strtr(rtrim(base64_encode(hash('sha256', $codeVerifier, true)), '='), '+/', '-_'),
                             $authCodePayload->code_challenge
                         ) === false
                     ) {
diff --git a/tests/AuthorizationServerTest.php b/tests/AuthorizationServerTest.php
index 068b914d..8b409a00 100644
--- a/tests/AuthorizationServerTest.php
+++ b/tests/AuthorizationServerTest.php
@@ -35,6 +35,7 @@ class AuthorizationServerTest extends TestCase
         // Make sure the keys have the correct permissions.
         chmod(__DIR__ . '/Stubs/private.key', 0600);
         chmod(__DIR__ . '/Stubs/public.key', 0600);
+        chmod(__DIR__ . '/Stubs/private.key.crlf', 0600);
     }
 
     public function testRespondToRequestInvalidGrantType()
diff --git a/tests/CryptKeyTest.php b/tests/CryptKeyTest.php
index f4fd0659..70bbc8d7 100644
--- a/tests/CryptKeyTest.php
+++ b/tests/CryptKeyTest.php
@@ -33,5 +33,13 @@ class CryptKeyTest extends TestCase
             'file://' . sys_get_temp_dir() . '/' . sha1($keyContent) . '.key',
             $key->getKeyPath()
         );
+
+        $keyContent = file_get_contents(__DIR__ . '/Stubs/private.key.crlf');
+        $key = new CryptKey($keyContent);
+
+        $this->assertEquals(
+            'file://' . sys_get_temp_dir() . '/' . sha1($keyContent) . '.key',
+            $key->getKeyPath()
+        );
     }
 }
diff --git a/tests/Grant/AuthCodeGrantTest.php b/tests/Grant/AuthCodeGrantTest.php
index c72073ec..40e4ef99 100644
--- a/tests/Grant/AuthCodeGrantTest.php
+++ b/tests/Grant/AuthCodeGrantTest.php
@@ -47,8 +47,12 @@ class AuthCodeGrantTest extends TestCase
     public function setUp()
     {
         $this->cryptStub = new CryptTraitStub;
-        $this->codeVerifier = rtrim(strtr(base64_encode(random_bytes(32)), '+/', '-_'), '=');
-        $this->codeChallenge = hash('sha256', strtr(rtrim(base64_encode($this->codeVerifier), '='), '+/', '-_'));
+
+        // [RFC 7636] Appendix B.  Example for the S256 code_challenge_method
+        // $this->codeVerifier = 'dBjftJeZ4CVP-mB92K27uhbUJU1p1r_wW1gFWFOEjXk';
+        $this->codeVerifier = strtr(rtrim(base64_encode(random_bytes(32)), '='), '+/', '-_');
+        // $this->codeChallenge = 'E9Melhoa2OwvFrEMTJguCHaoeK1t8URWbuGJSstw-cM';
+        $this->codeChallenge = strtr(rtrim(base64_encode(hash('sha256', $this->codeVerifier, true)), '='), '+/', '-_');
     }
 
     public function testGetIdentifier()
diff --git a/tests/Stubs/.gitattributes b/tests/Stubs/.gitattributes
new file mode 100644
index 00000000..ea9fa3f5
--- /dev/null
+++ b/tests/Stubs/.gitattributes
@@ -0,0 +1 @@
+private.key.crlf text eol=crlf
diff --git a/tests/Stubs/private.key.crlf b/tests/Stubs/private.key.crlf
new file mode 100644
index 00000000..5e7e5a01
--- /dev/null
+++ b/tests/Stubs/private.key.crlf
@@ -0,0 +1,27 @@
+-----BEGIN RSA PRIVATE KEY-----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+-----END RSA PRIVATE KEY-----