Retry failed calls to open SecTrust enumerators.

It doesn't seem to fail very often, but I've seen it fail, and CI has seen it fail.
Presumably there's some sort of race/sync condition in the OS that's being
encountered, so treat it as an intermittent problem and retry.

Author: bartonjs

src/Common/src/Interop/OSX/System.Security.Cryptography.Native.Apple/Interop.Trust.cs

@@ -55,36 +55,50 @@ private static SafeCFArrayHandle EnumerateStore(
             StoreEnumerator userEnumerator,
             StoreEnumerator machineEnumerator)
         {
-            int result;
-            SafeCFArrayHandle matches;
-            int osStatus;
+            const int RetryLimit = 3;
+            int osStatus = 0;
 
-            if (location == StoreLocation.CurrentUser)
+            // Occasionally calls to enumerate the trust list get errSecInvalidRecord.
+            // So, if we fail with result 0 ("see osStatus") just retry and see if the
+            // intermediate state has flushed itself.
+            for (int i = 0; i < RetryLimit; i++)
             {
-                result = userEnumerator(out matches, out osStatus);
-            }
-            else if (location == StoreLocation.LocalMachine)
-            {
-                result = machineEnumerator(out matches, out osStatus);
-            }
-            else
-            {
-                Debug.Fail($"Unrecognized StoreLocation value: {location}");
-                throw new CryptographicException();
-            }
+                int result;
+                SafeCFArrayHandle matches;
 
-            if (result == 1)
-            {
-                return matches;
-            }
+                if (location == StoreLocation.CurrentUser)
+                {
+                    result = userEnumerator(out matches, out osStatus);
+                }
+                else if (location == StoreLocation.LocalMachine)
+                {
+                    result = machineEnumerator(out matches, out osStatus);
+                }
+                else
+                {
+                    Debug.Fail($"Unrecognized StoreLocation value: {location}");
+                    throw new CryptographicException();
+                }
+
+                if (result == 1)
+                {
+                    return matches;
+                }
 
-            matches.Dispose();
+                matches.Dispose();
 
-            if (result == 0)
-                throw CreateExceptionForOSStatus(osStatus);
+                if (result == 0)
+                {
+                    // Instead of limiting it to particular error codes, just try it again.
+                    // A permanent error will be stable, a temporary one will hopefully go away.
+                    continue;
+                }
+
+                Debug.Fail($"Unexpected result from {location} trust store enumeration: {result}");
+                throw new CryptographicException();
+            }
 
-            Debug.Fail($"Unexpected result from {location} trust store enumeration: {result}");
-            throw new CryptographicException();
+            throw CreateExceptionForOSStatus(osStatus);
         }
     }
 }