Fix cryptography errors on macOS 10.13

src/Native/Unix/System.Security.Cryptography.Native.Apple/pal_symmetric.cpp

@@ -131,6 +131,10 @@ extern "C" int32_t AppleCryptoNative_CryptorReset(CCCryptorRef cryptor, const ui
     if (cryptor == nullptr)
         return -1;
 
+    // 10.13 Beta reports an error when resetting ECB, which is the only mode which has a null IV.
+    if (pbIv == nullptr)
+        return 1;
+
     CCStatus status = CCCryptorReset(cryptor, pbIv);
     *pccStatus = status;
     return status == kCCSuccess;

src/Native/Unix/System.Security.Cryptography.Native.Apple/pal_x509chain.cpp

@@ -174,7 +174,12 @@ static void MergeStatusCodes(CFTypeRef key, CFTypeRef value, void* context)
         // (On Windows CERT_CHAIN_PARA.pStrongSignPara is NULL, so "strongness" checks
         // are not performed).
     }
-
+    else if (CFEqual(keyString, CFSTR("StatusCodes")))
+    {
+        // 10.13 added a StatusCodes value which may be a numeric rehashing of the string data.
+        // It doesn't represent a new error code, and we're still getting the old ones, so
+        // just ignore it for now.
+    }
     else
     {
 #ifdef DEBUGGING_UNKNOWN_VALUE

src/System.Security.Cryptography.X509Certificates/tests/ChainTests.cs

@@ -165,6 +165,8 @@ public static void TestDispose()
         }
 
         [Fact]
+        // Crashing on macOS 10.13 Beta
+        [ActiveIssue(21436, TestPlatforms.OSX)]
         public static void TestResetMethod()
         {
             using (var sampleCert = new X509Certificate2(TestData.DssCer))