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Tiny Deathstars of Foulness

September 29th, 2018

Posted In: Mac OS X, Mac OS X Server

Tags: ,

Reporting on application usage is an interesting topic on the Mac. This is done automatically with a number of device management solutions. But there are things built into the OS that can help as well.

mdls "/Applications/Xcode.app" -name kMDItemLastUsedDate | awk '{print $3}'

Now, if you happen to also need the time, simply add ,$4 to the end of your awk print so you can see the next position, which is the time. Additionally, a simple one-liner to grab the foreground app via AppleScript is:

osascript -e 'tell application "System Events"' -e 'set frontApp to name of first application process whose frontmost is true' -e 'end tell'

That’s pretty much all I had to say about that.

September 27th, 2018

Posted In: Mac OS X, Mac Security

Tags: , , ,

There are a number of solutions on the market for scanning a Mac for files that have become infected with a virus or macro-virus. Many of these have a negative return on investment. So customers can instead go the open source route to scan files and quarantine them. And customers can use Jamf Pro to enable doing so. This page is meant to provide a quick and dirty guide to doing so, along with how this might be packaged and potentially tracked with Jamf Pro. First, we’ll install and configure a free tool called clamav.

There are a number of ways to install clam. For this example, just to get it done quickly, we’ll use homebrew which is simply brew with the install verb and clamav as the recipe to be brewed:

brew install clamav

This is going to place your configuration files in /usr/local/etc/clamav and these cannot be used as those supplied by default are simply sample configurations. Because the .sample files have a line that indicates they are an “Example” they cannot be used. So we’ll copy the sample configuration files for freshclam.conf and clamd.conf (the demonized version) and then remove the Example line using the following two lines:

cp /usr/local/etc/clamav/freshclam.conf.sample /usr/local/etc/clamav/freshclam.conf; sed -ie 's/^Example/#Example/g' /usr/local/etc/clamav/freshclam.conf
cp /usr/local/etc/clamav/clamd.conf.sample /usr/local/etc/clamav/clamd.conf; sed -ie 's/^Example/#Example/g' /usr/local/etc/clamav/clamd.conf

Next, we’ll need to update the virus definitions for clamav. This can be run without the fully qualified file path but we are going to go ahead and include it as some computers might have another version installed (e.g. via macOS Server):

freshclam -v

The initial scan should cover the full hard drive and can be run as clamscan

sudo /usr/local/bin/clamscan -r — bell -i /

Your routinely run jobs should be setup to a quarantine location. Because all users should be able to see their data that was quarantined we would write this to /Users/Shared/Quarantine. We can then use a standard clamscan to scan the system and then “move” quarantined items to that location and log those transactions to /Users/Shared/Quarantine/Quarantine.txt.

sudo mkdir /Users/Shared/Quarantine
sudo clamscan -r — scan-pdf=yes -l /Users/Shared/Quarantine/Quarantine.txt — move=/Users/Shared/Quarantine/ /

You can then use an Extension Attribute to read the Quarantine.txt file:

#!/bin/bash
 
#Read Quarantine
 
result = `cat /Users/Shared/Quarantine/Quarantine.txt`
 
#Echo Quarantine into EA
 
echo "<result>$result</result>"

Every environment is different. When combined with standard mrt scans using the built-in malware removal tool for macOS, clamAV can provide a routine added protection to isolate and help you remediate infections. 

Finally, it seems like I have yet to discuss antivirus and malware without getting into the conversation about whether you need it or not. In this post I am in no way taking a side on that argument, and it’s worth mentioning that I’m also not using “antivirus” to exclusively reference viruses but instead including all forms of malware. Rather, I’m exploring options for scanning systems routinely.You can easily run this nightly and parse the quarantine.txt file prior to picking it up with the Extension Attribute routinely in order to provided an additional layer of defense against potential threats to the Mac. Putting all of this into a software package would be rudimentary, and could benefit many organizations without putting our coworkers through the performance hit that many a commercial antivirus solution brings with it.

September 26th, 2018

Posted In: Mac OS X, Mac Security

Tags: , , , ,

I’ve been making guides to macOS Server since Server 2:
And along the way, I’ve also sold plenty of books on Mac Servers and gotten a lot of opportunities I might not have gotten otherwise. So thank you to everyone for joining me on that journey. After teaching so many how to use the services that Apple made available in their server operating system, when they announced they’d no longer be making many of the services my readers have grown dependent upon, I decided to start working on a guide on moving away from macOS Server. 
And then there are tons of all-in-one small business servers solutions, including Buffalo, Qnap, NetGear’s ReadyNAS, Thecus, LaCie, Seagate BlackArmor, and Synology. Because I happen to have a Synology, let’s look at setting up the same services we had in macOS Server, but on a cheaper Synology appliance:

September 25th, 2018

Posted In: Mac OS X, Mac OS X Server, Mac Security

Tags: , , , , , , , , , ,

September 25th, 2018

Posted In: JAMF, Mac OS X

Tags: , , , ,

macOS now comes with a vulnerability scanner called mrt. It’s installed within the MRT.app bundle in /System/Library/CoreServices/MRT.app/Contents/MacOS/ and while it doesn’t currently have a lot that it can do – it does protect against the various bad stuff that is actually available for the Mac. To use mrt, simply run the binary with a -a flag for agent and then a -r flag along with the path to run it against. For example, let’s say you run a launchctl command to list LaunchDaemons and LaunchAgents running:

launchctl list

And you see something that starts with com.abc. Let me assure you that nothing should ever start with that. So you can scan it using the following command: 

sudo /System/Library/CoreServices/MRT.app/Contents/MacOS/mrt -a -r ~/Library/LaunchAgents/com.abc.123.c1e71c3d22039f57527c52d467e06612af4fdc9A.plist

What happens next is that the bad thing you’re scanning for will be checked to see if it matches a known hash from MRT or from /System/Library/CoreServices/XProtect.bundle/Contents/Resources/XProtect.yara and the file will be removed if so. 

A clean output will look like the following:

2018-09-24 21:19:32.036 mrt[48924:4256323] Running as agent

2018-09-24 21:19:32.136 mrt[48924:4256323] Agent finished.

2018-09-24 21:19:32.136 mrt[48924:4256323] Finished MRT run

Note: Yara rules are documented at https://yara.readthedocs.io/en/v3.7.0/. For a brief explanation of the json you see in those yara rules, see https://yara.readthedocs.io/en/v3.5.0/writingrules.html.

So you might be saying “but a user would have had to a username and password for it to run.” And you would be correct. But XProtect protects against 247 file hashes that include about 90 variants of threats. Those are threats that APPLE has acknowledged. And most malware is a numbers game. Get enough people to click on that phishing email about their iTunes account or install that Safari extension or whatever and you can start sending things from their computers to further the cause. But since users have to accept things as they come in through Gatekeeper, let’s look at what was allowed.

To see a list of hashes that have been allowed:

spctl --list

When you allow an app via spctl the act of doing so is stored in a table in 

sudo sqlite3 /var/db/SystemPolicy

Then run .schema to see the structure of tables, etc. These include feature, authority, sequence, and object which contains hashes.

On the flip side, you can search for the com.apple.quarantine attribute set to com.apple.quarantine:

xattr -d -r com.apple.quarantine ~/Downloads

And to view the signature used on an app, use codesign:

codesign -dv MyAwesome.app

To sign a package:

productbuild --distribution mycoolpackage.dist --sign MYSUPERSECRETIDENTITY mycoolpackage.pkg

To sign a dmg:

codesign -s MYSUPERSECRETIDENTITY mycooldmg.dmg

However, in my tests, codesign is used to manage signatures and sign, spctl only checks things with valid developer IDs and spctl checks items downloaded from the App Store. None of these allow for validating a file that has been brought into the computer otherwise (e.g. through a file share). 

Additionally, I see people disable Gatekeeper frequently, which is done by disabling LSQuarantine directly:

defaults write com.apple.LaunchServices LSQuarantine -bool NO

And/or via spctl:

spctl --master-disable

Likewise, mrt is running somewhat resource intensive at the moment and simply moving the binary out of the MRT.app directory will effectively disable it for now if you’re one of the people impacted.

September 24th, 2018

Posted In: Mac OS X, Mac Security

Tags: , , , , ,

Firefox describes their malware posture at https://support.mozilla.org/en-US/kb/how-does-phishing-and-malware-protection-work which heavily leverages Google SafeBrowsing, as do many a browser. Settings for SafeBrowsing are set in the browser.safebrowsing.downloads.remote.enabled pref. To lock this pref, you would need to create an autoconfig.js file in 

/Applications/Firefox.app/Contents/Resources/defaults/pref that points to a firefox.cfg file with a lock pref in it. To do so, create the autoconfig.js file and paste in these settings:

// Configure SafeBrowsing
pref("general.config.filename", "firefox.cfg");
pref("general.config.obscure_value", 0);

Then create the firefox.cfg file and paste in these settings:

// Configuring SafeBrowsing
lockPref("browser.safebrowsing.downloads.remote.enabled", TRUE)

Live Firefox preferences can be seen at /Users/charles.edge 1/Library/Application Support/Firefox/Profiles/*.default. Because SafeBrowsing is enabled by default, you shouldn’t see it listed unless it’s been disabled. But you can confirm it’s doing its thing by parsing the contents of these settings:

user_pref("browser.safebrowsing.provider.google4.lastupdatetime", "1537457871853");
user_pref("browser.safebrowsing.provider.google4.nextupdatetime", "1537459685853");
user_pref("browser.safebrowsing.provider.mozilla.lastupdatetime", "1537457872202");
user_pref("browser.safebrowsing.provider.mozilla.nextupdatetime", "1537461472202");

September 21st, 2018

Posted In: Mac OS X, Mac Security

Tags: , , ,

September 20th, 2018

Posted In: Bushel

Tags:

macOS allows you to launch an app but in a hidden state. To do so, use the open command to open the app and then use the -a flag to specify the path of the app and –hide after the path to the app, as follows:

/usr/bin/open -a /Applications/Notes.app --hide

September 19th, 2018

Posted In: Mac OS X

Tags: , , ,

OpenBSM is a subsystem that has been installed on the Mac for some time. OpenBSM provides that ability to create and read audit logs based on the Common Criteria standards.

Audit Logs

The quick and easy way to see what OpenBSM is auditing is to cat the /etc/security/audit_control file:

cat /etc/security/audit_control

The output displays the directory of audit logs, as well as what is currently being audited. By default the configuration is as follows:

#
# $P4: //depot/projects/trustedbsd/openbsm/etc/audit_control#8 $
#
dir:/var/audit
flags:lo,aa
minfree:5
naflags:lo,aa
policy:cnt,argv
filesz:2M
expire-after:10M
superuser-set-sflags-mask:has_authenticated,has_console_access
superuser-clear-sflags-mask:has_authenticated,has_console_access
member-set-sflags-mask:
member-clear-sflags-mask:has_authenticated

You can then see all of the files in your audit log, using a standard ls of those 

ls /var/audit

As you can see, the files are then stored with a date/time stamp naming convention. 

20180119012009.crash_recovery 20180407065646.20180407065716 20180407073931.20180407074018
20180119022233.crash_recovery 20180407065716.20180407065747 20180407074018.20180407074050
20180119043338.crash_recovery 20180407065747.20180407065822 20180407074050.20180511030725
20180119134354.crash_recovery 20180407065822.20180407065853 20180511030725.crash_recovery
20180208172535.crash_recovery 20180407065853.20180407065928 20180616025641.crash_recovery
20180219133137.crash_recovery 20180407065928.20180407070004 20180624022028.crash_recovery
20180312153634.crash_recovery 20180407070004.20180407070036 20180718235941.crash_recovery
20180312160131.crash_recovery 20180407070036.20180407071722 20180720031150.crash_recovery
20180322141701.crash_recovery 20180407071722.20180407072215 20180724021901.crash_recovery
20180330190040.crash_recovery 20180407072215.20180407072259 20180728173033.crash_recovery
20180330191420.20180407064622 20180407072259.20180407073747 20180907031058.crash_recovery
20180407064622.20180407065616 20180407073747.20180407073836 20180911021141.not_terminated
20180407065616.20180407065646 20180407073836.20180407073931 current

The files are binary and so cannot be read properly without the use of a tool to interpret the output. In the next section we will review how to read the logs. 

Using praudit

Binary files aren’t easy to read. Using the praudit binary, you can dump audit logs into XML using the -x flag followed by the path of the log. For example, the following command would read a given log in the above /var/audit example directory:

praudit -x 20180407065747.20180407065822

One record of the output would look as follows

<record version="11" event="session start" modifier="0" time="Sat Apr 7 01:58:22 2018" msec=" + 28 msec" >
<argument arg-num="1" value="0x0" desc="sflags" />
<argument arg-num="2" value="0x0" desc="am_success" />
<argument arg-num="3" value="0x0" desc="am_failure" />
<subject audit-uid="-1" uid="root" gid="wheel" ruid="root" rgid="wheel" pid="0" sid="100645" tid="0 0.0.0.0" />
<return errval="success" retval="0" />
</record>

In the above output, you’ll find the time that an event was logged, as well as the type of event. This could be parsed for specific events, and, as an example, just dump the time and event in a simple json or xml for tracking in another tool. For example, if you’re doing statistical analysis for how many times privileges were escalated as a means of detecting a bad actor on a system.

You can also use the auditreduce command to filter records. Once filtered, results are still in binary and must be converted using praudit.

September 18th, 2018

Posted In: Mac OS X, Mac Security

Tags: , , , ,

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