Bug 35670 - ProtectedData throws CryptographicException in OS X El Capitan
Summary: ProtectedData throws CryptographicException in OS X El Capitan
Status: NEW
Alias: None
Product: Class Libraries
Classification: Mono
Component: System.Security ()
Version: master
Hardware: Macintosh Mac OS
: Normal normal
Target Milestone: Untriaged
Assignee: Bugzilla
Depends on:
Reported: 2015-11-08 19:12 UTC by john
Modified: 2015-12-23 04:21 UTC (History)
3 users (show)

Is this bug a regression?: ---
Last known good build:

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Description john 2015-11-08 19:12:09 UTC
In OS X El Capitan, ProtectedData in per-machine scope will throw exception, complaining
"Could not create machine key store '/usr/share/.mono/keypairs'."

Following code can reproduce in Mono MDK, or, in Mono Preview package for El Capitan (4.2.1)

using System;
using System.Security.Cryptography;

static class Program
    static void Main()
        byte[] bytes = ProtectedData.Protect(new byte[]{1,2,3}, new byte[] { 1, 2, 3 },DataProtectionScope.LocalMachine);
Comment 1 john 2015-11-08 19:22:05 UTC
Once the 'System Integrity Protection' is disabled, the ProtectedData.Protect() call will succeed. 

Once the 'keypairs' was created (I assume), the ProtectedData.Protect() and ProtectedData.Unprotect() calls are OK, even when the 'System Integrity Protection' is turned on again.
Comment 2 Ross 2015-11-11 16:09:35 UTC
How about:
- Write the keypairs to a new location that 'System Integrity Protection' allows.
- Add fallback read logic which first attempts to load the keys from the new location, and if not found reads from the original location, maintaining backwards compatibility.