Revoking Chinese CNNIC Root Certificate in Mac OS X
Earlier this month, Google and Firefox both dropped the Root Certificate of Chinese Certificate Authority CNNIC, after it was discovered that it had delegated its authority to an Egyptian intermediary to allow it to fraudulently sign SSL/TLS certificates for the google.com domain (presumably for the purposes of performing man-in-the-middle attacks and snooping on Egyptian internet traffic).
Apple, despite releasing Mac OS X 10.10.3 and iOS 8.3, has yet to remove this rogue CA. I hope that Apple joins in and revokes the CNNIC in an upcoming update, but in the meantime you can remove it from OS X yourself!
Simply run the following command in the Terminal and *poof*, another unnecessary and untrusted CA bites the dust:
sudo security delete-certificate -c "CNNIC ROOT" /System/Library/Keychains/SystemRootCertificates.keychain
It’s worth pointing out that a deleted Root CA cert may re-appear in a subsequent system update (I will check when 10.10.4 comes out). The alternative to this, which can only be achieved using Keychain Access (I believe), is to tell OS X to never trust a given Root CA certificate – a setting that shouldn’t be undone by future updates. To do this:
- Open Keychain Access
- Click on ‘System Roots’ on the left
- Right-click on the Root CA you don’t trust (ie. CNNIC ROOT) and select Get Info
- Expand the ‘Trust’ section
- Select ‘Never Trust’ from the “When using this certificate” dropdown
- Close the panel (OS X will probably ask for your password to authenticate the change)
- You should then see a red X icon next to the untrusted cert.
I personally think that our operating systems and browsers already trust far too many Root CAs, many of which are unnecessary, others are potentially malicious. OS X by default trusts around 204 Root CAs. I’m planning on cutting this down to a short list of CAs that are both (a) trusted and (b) necessary for normal day-to-day use of the Internet. I’ll report back on that when I get time.
Unfortunately, there is no mechanism in iOS to remove certificates from the Root CA store. The list of current trusted Root CAs in iOS can be found here.
Security Update 2011-005 Fixes DigiNotar SSL Vulnerability
Apple has finally issued Security Update 2011-005 to address the recent issues around compromised Dutch certificate authority DigiNotar. It was discovered that at least 531 fraudulent SSL certificates were issued by DigiNotar, leading to their root certificate being revoked in all major operating systems and browsers over the past two weeks. A man-in-the-middle attacker in possession of one of these certs (eg. Google, Skype), would be able to intercept SSL-encrypted traffic to those sites. It is believed that the use of these fraudulent certs may have been limited to the Iranian government.
This patch removes the DigiNotar CA from the trusted root certificates in the Mac OS X keychain (which is also used by Safari) for Lion and Snow Leopard. Unfortunately no patch has been issued for Leopard (10.5) users, leaving them at a heightened risk from these bad certificates. It is recommended that Leopard users delete the DigiNotar CA certificate from the Keychain using the following steps:
- Open Keychain Access (/Applications/Utilities/Keychain Access)
- Click on the System Roots keychain in the top-left hand panel
- Click on Certificates in the bottom-left hand panel
- Type DigiNotar into the search field in the top right.
- Right-click on the DigiNotar Root CA, and select Delete.
# sudo /usr/bin/security delete-certificate -Z C060ED44CBD881BD0EF86C0BA287DDCF8167478C /System/Library/Keychains/SystemRootCertificates.keychain
Firefox users should update to the latest version of Firefox. Here is the full Apple description for this update:
Security Update 2011-005
- Certificate Trust Policy Available for: Mac OS X v10.6.8, Mac OS X Server v10.6.8, OS X Lion v10.7.1, Lion Server v10.7.1Impact: An attacker with a privileged network position may intercept user credentials or other sensitive information
Description: Fraudulent certificates were issued by multiple certificate authorities operated by DigiNotar. This issue is addressed by removing DigiNotar from the list of trusted root certificates, from the list of Extended Validation (EV) certificate authorities, and by configuring default system trust settings so that DigiNotar’s certificates, including those issued by other authorities, are not trusted.
Key iOS Security Updates Patch PDF and Certificate Validation Vulnerabilities (4.3.4 and 4.3.5)
The two latest iOS updates are fairly significant in that they patch two critical vulnerabilities. iOS update 4.3.4 patched a number of bugs including comex’s PDF/FreeType vulnerability used to create the latest JailbreakMe exploit. If you’re a jailbreaker, it’s essential that you run comex’s ‘PDF Patcher 2’ within Cydia, in order to patch the underlying vulnerability. iOS update 4.3.5 released a couple days ago, patches a fairly significant bug in the way iOS validates SSL/TLS certificates. This vulnerability can allow an attacker to intercept and/or modify data protected within an SSL session without the user knowing it. This was possible to due the fact that iOS didn’t validate the basicContstrains parameter of SSL certificates in the chain.
If you’re only an occasional patcher – now is the time.
Safari, Mac OS X and Fraudulent SSL Certificates (Comodo)
Following the recent hacking of Comodo, a certificate authority that distributes SSL certificates, web users to the following domains are at a higher risk of phishing and sniffing attacks:
- login.live.com
- mail.google.com
- www.google.com
- login.yahoo.com
- login.skype.com
- addons.mozilla.org
Attackers were able to obtain SSL certificates for these domains, essentially allowing them to pose as those websites. The certificates have since been revoked by Comodo, however this relies on browsers checking for them by checking Comodo’s Certificate Revocation List (CRL) and having the Online Certificate Status Protocol (OCSP) enabled. Firefox and Chrome were updated last week to block the fraudulent certs, but Safari doesn’t do CRL and OCSP checking by default.
Hit the jump for how to enable these checks in OSX and Safari. Read more
Intercepting Unencrypted Sessions with Firesheep
Firesheep, a new Firefox extension that allows you to intercept unencrypted sessions being transmitted over the network, has been released by Eric Butler. Taking advantage of websites that don’t use SSL by default, such as Facebook and Twitter, Firesheep uses network-sniffing to intercept the cookies used to transport session IDs (also known as sidejacking). Note this attack will work over Wifi by default, but will require extra work on a switched wired network.
Once Firesheep has intercepted a user’s cookie over the network, it allows you to be logged in as that user. The concept of session-stealing is as old as the internet, but to have a Firefox extension that does it in such a user-friendly manner is great. It’s also a lot more dangerous as it makes this attack so much easier for any unskilled attacker to carry out.
Protecting Yourself
The are a couple ways of protecting yourself from sidejacking attacks. The first and foremost is to ensure that you use SSL when visiting popular or particularly sensitive web services, including Gmail, Hotmail, Facebook, Twitter, or any other site that’s of importance to you (online banking?). The best way of doing this is to make sure your bookmarks (or the URL you type in) starts with “https://”, and that no SSL certificate errors appear. Another Firefox plugin, HTTPS Everywhere, from the privacy advocates over at the Electronic Frontier Foundation (EFF), enforces SSL on predefined sites. You can also protect your searches by using Google over SSL (encrypted.google.com).
Another way of protecting yourself is to channel your browser traffic through a VPN or SSH Tunnel. Your data is then sent through an encrypted link to a remote host (preferably one you control), before being sent to the destination.
Installing Firecat
Firebug runs in Firefox on Mac OS X and Windows, however Windows users will need to install WinPcap first. After downloading the extension file (xpi), simply open it by going to File -> Open File (you will need to restart Firefox). To clarify some confusion, once you’ve installed the extension, you need to go to View -> Sidebar -> Firesheep to enable it, and click Start Capturing.
Give it a try for yourself.
[Update] Detecting and protecting against Firesheep with FireShepherd.
Apple Launches MobileMe Beta (adds persistent SSL)
After logging into my MobileMe account today I was greeted with a small banner in the left-hand menu announcing an upcoming Mail Beta. Although I haven’t yet been upgraded to the Beta, it appears that Apple have been hard at work on turning MobileMe Mail into a full blown web email client… it’s about time.
Additions include proper formatting capability, improved layout and display, e-mail rules, and persistent SSL. With regards to that last one, although MobileMe supports SSL at the login screen to protect your credentials, all subsequent information (read: all your emails are belong to us) is sent in cleartext – an issue I posted about a long time ago. Google enabled the option to use persistent SSL for its Gmail service back in mid-2008 (although it is an option you have to specifically set in your Gmail preferences).
From my initial impressions of the beta, it definitely looks much better to begin with. The ability to view your inbox in the three (classic, compact, widescreen) views will probably be quite popular. The search field also works better. They finally allow you to scroll fluidly through your mailbox folders, however it only loads a certain number of message at a time. Now, this wouldn’t be too bad except that in this case it takes a bit too long for that loading to happen. Apart from that the persistent SSL also works nicely, so once they fix any small bugs and improve performance, I’ll consider myself happy.
Oh… and there’s rumors that MobileMe might become free. THAT would make me happy too!
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