Harden SecKeyCopyExternalRepresentation against sensitive keys

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

@@ -15,6 +15,8 @@ internal static partial class AppleCrypto
         private const int kSuccess = 1;
         private const int kErrorSeeError = -2;
         private const int kPlatformNotSupported = -5;
+        private const int kKeyIsSensitive = -6;
+        private const int kKeyIsNotExtractable = -7;
 
         internal enum PAL_KeyAlgorithm : uint
         {
@@ -125,12 +127,6 @@ internal static bool TrySecKeyCopyExternalRepresentation(
             SafeSecKeyRefHandle key,
             out byte[] externalRepresentation)
         {
-            const int errSecPassphraseRequired = -25260;
-
-            // macOS Sonoma 14.4 started returning errSecInvalidKeyAttributeMask when a key could not be exported
-            // because it must be exported with a password.
-            const int errSecInvalidKeyAttributeMask = -67738;
-
             int result = AppleCryptoNative_SecKeyCopyExternalRepresentation(
                 key,
                 out SafeCFDataHandle data,
@@ -144,12 +140,12 @@ internal static bool TrySecKeyCopyExternalRepresentation(
                     case kSuccess:
                         externalRepresentation = CoreFoundation.CFGetData(data);
                         return true;
+                    case kKeyIsSensitive:
+                        externalRepresentation = [];
+                        return false;
+                    case kKeyIsNotExtractable:
+                        throw new CryptographicException(SR.Cryptography_KeyNotExtractable);
                     case kErrorSeeError:
-                        if (Interop.CoreFoundation.GetErrorCode(errorHandle) is errSecPassphraseRequired or errSecInvalidKeyAttributeMask)
-                        {
-                            externalRepresentation = Array.Empty<byte>();
-                            return false;
-                        }
                         throw CreateExceptionForCFError(errorHandle);
                     default:
                         Debug.Fail($"SecKeyCopyExternalRepresentation returned {result}");

src/libraries/System.Security.Cryptography/src/Resources/Strings.resx

@@ -465,6 +465,9 @@
   <data name="Cryptography_KeyBlobParsingError" xml:space="preserve">
     <value>Key Blob not in expected format.</value>
   </data>
+  <data name="Cryptography_KeyNotExtractable" xml:space="preserve">
+    <value>The key does not permit being exported.</value>
+  </data>
   <data name="Cryptography_KeyTooSmall" xml:space="preserve">
     <value>The key is too small for the requested operation.</value>
   </data>

src/libraries/System.Security.Cryptography/tests/Resources/Strings.resx

@@ -75,6 +75,9 @@
   <data name="Cryptography_Invalid_IA5String" xml:space="preserve">
     <value>The string contains a character not in the 7 bit ASCII character set.</value>
   </data>
+  <data name="Cryptography_KeyNotExtractable" xml:space="preserve">
+    <value>The key does not permit being exported.</value>
+  </data>
   <data name="Cryptography_X509Store_WouldModifyUserTrust" xml:space="preserve">
     <value>Removing the requested certificate would modify user trust settings, and has been denied.</value>
   </data>

src/native/libs/System.Security.Cryptography.Native.Apple/pal_seckey.c

@@ -72,9 +72,31 @@ int32_t AppleCryptoNative_SecKeyCopyExternalRepresentation(SecKeyRef pKey,
     assert(pErrorOut != NULL);
 
     *pErrorOut = NULL;
+    *ppDataOut = NULL;
+    int32_t ret = 0;
+    CFDictionaryRef attributes = SecKeyCopyAttributes(pKey);
 
-    *ppDataOut = SecKeyCopyExternalRepresentation(pKey, pErrorOut);
-    return *ppDataOut == NULL ? kErrorSeeError : 1;
+    if (attributes != NULL)
+    {
+        if (CFDictionaryGetValue(attributes, kSecAttrIsExtractable) == kCFBooleanFalse)
+        {
+            ret = kKeyIsNotExtractable;
+        }
+        else if (CFDictionaryGetValue(attributes, kSecAttrIsSensitive) == kCFBooleanTrue)
+        {
+            ret = kKeyIsSensitive;
+        }
+
+        CFRelease(attributes);
+    }
+
+    if (ret == 0)
+    {
+        *ppDataOut = SecKeyCopyExternalRepresentation(pKey, pErrorOut);
+        ret = *ppDataOut == NULL ? kErrorSeeError : 1;
+    }
+
+    return ret;
 }
 
 SecKeyRef AppleCryptoNative_SecKeyCopyPublicKey(SecKeyRef privateKey)

src/native/libs/System.Security.Cryptography.Native.Apple/pal_seckey.h

@@ -16,6 +16,8 @@ static const int32_t kErrorSeeError = -2;
 static const int32_t kErrorUnknownAlgorithm = -3;
 static const int32_t kErrorUnknownState = -4;
 static const int32_t kPlatformNotSupported = -5;
+static const int32_t kKeyIsSensitive = -6;
+static const int32_t kKeyIsNotExtractable = -7;
 
 enum
 {