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Keyword: ‘System Integrity Protection’

Google Keystone update breaks Macs’ ability to boot if System Integrity Protection is disabled

September 25, 2019 6 comments

On the evening of Monday, September 23rd, a number of film and TV editors started reporting that their workstations were not rebooting successfully. The problem was initially blamed on the Media Composer software sold by Avid.

On September 24th, more instances were reported and it became clear that this was not an issue restricted to Macs with Media Composer installed. After extensive checking and testing, the folks in the MacAdmins Slack were able to narrow down the issue to an update to Google’s Keystone software, which Google uses to update Google Chrome and other Google products on macOS.

The now-pulled Keystone update attempts to remove the /var symlink, which is usually protected by Apple’s System Integrity Protection (SIP) security feature.

Image 2

On Macs where SIP was disabled, this protection did not apply and the Keystone update was able to remove the /var symlink. This symlink is not a directory itself, but points to another directory (/private/var) which contains software necessary for the operating system to boot and function correctly, so removing the /var symlink rendered the affected Macs unbootable.

As mentioned previously, Google has pulled the problematic Keystone update and has published instructions on how to remediate affected Macs. For more details, please see below the jump.

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Updated System Integrity Protection status reporting script

December 18, 2015 Leave a comment

After writing a Casper Extension Attribute script to report on the status of System Integrity Protection, I realized that I hadn’t accounted for reporting SIP’s custom configurations. These are configurations where SIP is enabled, but one or more of SIP’s protections or restrictions has been disabled. I’ve now updated the script to also report on the following SIP configurations:

  • Kext Signing: disabled
  • Filesystem Protections: disabled
  • NVRAM Protections: disabled
  • Debugging Restrictions: disabled
  • DTrace Restrictions: disabled

For more details, please see below the jump.

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Casper Extension Attribute script to report System Integrity Protection status

December 16, 2015 Leave a comment

To follow up on Apple’s changing the output of csrutil status when System Integrity Protection (SIP) is disabled, I’ve posted the following Casper extension attribute to my GitHub repo to report on whether SIP is enabled or disabled.

The script has the following functions:

If the Mac is running 10.10.x or earlier

The script reports System Integrity Protection Not Available For and then reports the relevant version of OS X. For example, the script returns the following output on a Mac running OS X 10.10.5:

System Integrity Protection Not Available For 10.10.5

If the Mac is running 10.11.x or later

This script uses csrutil status to check SIP’s status. If System Integrity Protection is disabled, the script returns the following output:

Disabled

If System Integrity Protection is enabled, the script returns the following output:

Active

For those interested, the script is available on my GitHub repo:

https://github.com/rtrouton/rtrouton_scripts/tree/master/rtrouton_scripts/Casper_Extension_Attributes/check_system_integrity_protection_status

System Integrity Protection’s csrutil status’ message change for OS X 10.11.2

December 16, 2015 3 comments

In order to check whether System Integrity Protection (SIP) is enabled or disabled on a Mac running OS X El Capitan, you can use the csrutil command to report on SIP’s current status. For example, to learn if SIP is enabled or disabled, run the following command:

csrutil status

This command can be run without root privileges and will tell you if SIP is on or off.

If SIP is enabled on 10.11.0 or higher, you should receive the following message:

System Integrity Protection: enabled

Csrutil status enabled run outside recovery

If SIP is disabled on OS X 10.11.0 or 10.11.1, you may receive a confusing message which indicates that SIP is enabled, followed by a list of individual SIP functions which are disabled. If all functions listed are showing as being disabled, SIP is actually completely disabled; it’s just confusingly worded.

Csrutil status disabled run outside recovery 10101

It appears that Apple has updated the status message on OS X 10.11.2 to make it much more clear when SIP is disabled. On 10.11.2, if SIP is disabled, you now should receive the following message:

System Integrity Protection: disabled

Csrutil status disabled run outside recovery 10102

Configuring System Integrity Protection without booting to Recovery HD

October 5, 2015 4 comments

One interesting part of Apple’s developer documentation for System Integrity Protection (SIP) is the note shown below, indicating that it’s possible to configure SIP for environments that can’t access Recovery.

Apple developer documentation for configuring SIP outside recovery

When I followed up with Apple about this, I was told that this meant I could configure it using NetBoot, using a NetBoot set that included the needed Recovery environment.

The example used was leveraging a new option in System Image Utility to create a package-only installation NetBoot set.

System image utility package only installation

This new type of NetBoot set is is designed to install only scripts, configuration profiles and packages as opposed to installing an OS. For more details, see below the jump.

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System Integrity Protection – Adding another layer to Apple’s security model

October 1, 2015 15 comments

As part of the release of OS X El Capitan, Apple has added a new layer named System Integrity Protection (SIP) to its security model. To understand how System Integrity Protection fits in, let’s first take a look at Apple’s security model as it existed as of OS X Yosemite.

OS X Defenses

 

Gatekeeper

Gatekeeper is one of the outer lines of defense. It allows users to restrict which sources they can install applications from, with the general idea being that malware will not be from an allowed source.

 

Sandboxing

OS X also uses sandboxing extensively. A sandbox typically provides a tightly controlled set of resources for programs to run in. Network access, the ability to inspect the host system, or reading from input devices is usually disallowed or heavily restricted.

 

POSIX permissions

OS X uses the Unix permissions model as defined by POSIX, which governs which users and groups can access which files and directories. If a particular user account requests access to a particular file or directory and does not have the necessary rights, that account is refused access.

 

Keychains

The innermost layer of defense are keychains. Keychains are very specialized databases which are designed for the storing of secrets, like passwords, private keys, PIN numbers, and then controlling access to those secrets. To help protect these secrets, keychains are encrypted.

 

There’s an issue with this model though and it’s been there for decades. It pre-exists OS X and even pre-exists Apple as a company. That issue is found in the POSIX permissions layer.

OS X defenses with POSIX highlighted

Root

Whoami root

 

Root is the superuser for a Unix system and the Unix permissions model is designed around the assumption that root has access to everything. Apple has not ignored this issue and has put some controls in place to limit the actual root user. These controls include disabling the root user account, discouraging its use, and providing ways to access elevated or root privileges using other means.

However, the root user account is still present and still can do anything on the system.

 

System Integrity Protection

To limit what the superuser can do and add another layer to OS X’s security model, Apple has developed SIP and deployed it as part of OS X El Capitan. SIP is designed to limit the power of root and to protect the system even from the superuser. For more details, see below the jump.

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System Integrity Protection and resetting NVRAM

September 21, 2015 Leave a comment

OS X El Capitan’s new System Integrity Protection (SIP) security feature stores its active security configuration in NVRAM. This allows SIP’s configuration to persist across OS installs, but this design choice also means that resetting NVRAM will cause SIP to reset as well. In my testing, this reset will result in the following SIP configuration:

Resetting the NVRAM, otherwise known as a PRAM reset or PRAM zap, has been a standard part of the Mac troubleshooting toolkit for a long time and is performed by pressing and holding down the Option, Command (⌘), P, and R keyboard keys at startup.

PRAM zap

For shops that do not plan to change SIP’s default configuration or set a NetBoot whitelist, NVRAM resets causing SIP’s configuration to also reset should not affect normal operations.

However, for those shops who will need to maintain a NetBoot whitelist or a custom SIP configuration, I would advise education where needed about this change and how it affects SIP configuration in your environment.

System Integrity Protection and the end of XProtect management for browser plug-ins

September 14, 2015 13 comments

OS X El Capitan adds a new security feature named System Integrity Protection (SIP). Among other things, SIP prevents parties other than Apple from adding, deleting or modifying directories and files stored in certain directories:

  • /bin
  • /sbin
  • /usr
  • /System

Apple has indicated that the following directories are available for developers to access:

  • /usr/local
  • /Applications
  • /Library
  • ~/Library

All directories in /usr except for /usr/local are protected by SIP.

SIP’s protection of /System affects XProtect’s XProtect.plist and XProtect.meta.plist configuration files as they are stored in the following location inside /System:

/System/Library/CoreServices/CoreTypes.bundle/Contents/Resources/XProtect.plist
/System/Library/CoreServices/CoreTypes.bundle/Contents/Resources/XProtect.meta.plist

As the XProtect configuration files will be locked against editing on OS X El Capitan, this means that they can no longer be managed to allow older versions of the Flash and Java browser plug-ins to run.

If your shop includes a mission-critical system that requires using older Flash or Java browser plug-ins, I recommend working with your vendor and/or in-house developers to find out:

  1. If the use of the Java and/or Flash browser plug-ins can be discontinued.
  2. If their use can’t be discontinued, if the system in question can be updated to support the latest versions of these plug-ins and continue to be compatible as new versions of the Java and/or Flash browser plug-ins are released.

Update – 9-14-2015: Josh Dyson has pointed out that there is a way to allow older plug-ins to access specific sites.

By adding the needed sites to a whitelist in Safari and setting those specific sites to Allow Always, those sites’ functions will be accessible with the older browser plug-in even if XProtect would otherwise block the use of the plug-in. Websites not included in the whitelist would still have the use of the plug-in blocked.

Screen Shot 2015-09-14 at 8.20.10 PM

Apple has provided a KBase article showing how to manage Safari plug-in options, including how to whitelist websites, using a configuration profile. It’s available via the link below:

https://support.apple.com/HT202947

NetBooting and System Integrity Protection

September 5, 2015 7 comments

Apple took an unusual step this week and released a knowledgebase (KBase) article that refers to an as-yet unreleased operating system:

Prepare for NetBoot, NetInstall, and NetRestore requirements in OS X El Capitan

I can only praise the decision to create it. The content covered affects a number of enterprise Mac environments and gives the Mac admins who support those environments time to prepare for an important change which may affect them.

That said, the KBase article itself is confusingly written and also includes an error. For more details, see below the jump.

Read more…

Kernel extensions and macOS High Sierra

August 24, 2017 10 comments

As part of the pre-release announcements about macOS High Sierra, Apple released the following KBase article:

As part of the KBase article, Apple included a Changes coming with macOS High Sierra section which featured this note:

macOS High Sierra introduces a new feature that requires user approval before loading new third-party kernel extensions. This feature will require changes to some apps and installers in order to preserve the desired user experience.

Screen Shot 2017 08 23 at 9 33 49 PM

That section in turn links to this KBase article, which describes the behavior in more detail:

To improve security on the Mac, kernel extensions installed with or after the installation of macOS High Sierra require user consent in order to load. This is known as User Approved Kernel Extension Loading. Any user can approve a kernel extension, even if they don’t have administrator privileges.


Screen Shot 2017 08 23 at 10 23 34 PM

What’s all this mean? For more details, see below the jump.

Read more…

Categories: Mac administration, macOS
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