Tuesday, October 17, 2017

KRACK is wack on Power Macs

After WEP fell due to the 2001 Flurher-Mantin-Shamir attack, WPA2 became the standard way to secure a WiFi connection. Now, the mighty have fallen due to KRACK (Key Reinstallation AttACK), meaning no WiFi network is safe.

KRACK is particularly wack problematic because there are multiple varieties of attack and virtually every system tested was vulnerable to at least one of them:

The attacks concentrate primarily on the handshakes used to distribute keys, including the 4-way handshake used to bring up a new client ("supplicant"). This last point is particularly relevant because Mavericks and Sierra were both vulnerable to attacks on the 4-way handshake but iOS 10.3.1 is not.

We can confidently assume that 10.4 and 10.5 (and 10.6, for that matter) are vulnerable in the same or similar ways that at least 10.9.5 are (I'll dive into this in a moment), but the situation is really bad for Linux. wpa_supplicant 2.6 and prior are vulnerable to all of the variants, including current PPC Linux users and devices running Android 6.0+. These will almost certainly be patched eventually, even considering the shrinking support for 32-bit PowerPC in Linux. OpenBSD is also vulnerable, but patches emerged prior to the embargo, and its close relative NetBSD will likely be repaired in a similar fashion. Microsoft has quietly issued a Patch Tuesday update that covers KRACK. There are reports that the issue is already patched in current betas of macOS and iOS, but it's not clear yet if these patches will be backported to Sierra or El Capitan.

10.5 and earlier exclusively use the private framework Apple80211.framework for WiFi connectivity. Although the public wireless networking framework CoreWLAN was introduced with 10.6, the later private framework CoreWifi is not present and a comparison of symbols shows subsequent upgrades to Apple80211's functionality in Snow Leopard, so it is very likely in use invisibly there as well. Although this framework still exists in 10.12, it does not appear to be used or linked by CoreWLAN, implying it was since internally deprecated. Apple never documented this framework or made it open source, but there have been attempts to reverse engineer it. However, the necessary changes likely mean inserting more sanity checks during the key handshake, which would require a bit more than just patching the library in place. I've done a little preliminary disassembly of it but I haven't found where this critical section exists yet. However, there is a tool in this framework which will be very helpful to determine your actual risk; read on.

WPA2 has three major encryption protocols, only two of which are supported by PPC Mac OS X, namely TKIP (a legacy encryption protocol from WEP intended as an interim compatibility measure), and AES-CCMP, a more secure protocol which is supported in 10.3.3+ and is sometimes just abbreviated "AES" (incorrectly) or "CCMP." TKIP was deprecated in 2012, but is still often used. The last form is GCMP, which no Power Mac supports in OS X and is part of 802.11ac Gigabit WiFi. This turns out to be a blessing, because KRACK can actually recover the key from GCMP-based connections and forge packets in both directions. This is even worse than TKIP's exposure, despite being the older and historically more insecure means of encryption.

The router situation is probably worst of all. Many older WiFi access points will never receive firmware updates, and even if they do, just patching the router is insufficient; every connecting client must also be patched. Some information circulated earlier that said only patching the router is adequate to mitigate the risk, but the discoverer of the flaw is clear both clients and the router must be updated to eliminate the risk completely.

Given it's not currently clear how we can patch OS X, then, what can you do with your Power Mac? Well, obviously, if you have the ability to hardwire your system, that would be preferable. All of my desktop Power Macs connect to a secured internal network over wired Ethernet that cannot directly route to the Internet.

If your connection to the router you control is still using TKIP (or any form of WPA or WEP), you should make sure it is WPA2 AES-CCMP. Log into your router and look at your security settings and change them if necessary; while you're at it, also see if your manufacturer has a firmware update for your router. While AES-CCMP is still vulnerable to some of these attacks and traffic secured by it can be decrypted, the actual key cannot be forged, so an attacker cannot actually join your network and attack it in place; they would have to clone your WiFi router's MAC address to a new access point with the same name on a different channel that's in range. This might be a risk in a hotel or apartment building but probably not in your house unless your neighbour is naughty and needs a baseball bat education. (If you have an Apple AirPort base station, this old TidBITS article can help you with the steps.) You can confirm your setup by opening a Terminal and entering these commands ([...] means not important for this usage):

% cd /System/Library/PrivateFrameworks/Apple80211.framework/Resources/
% ./airport -s
1 Infrastructure networks found:
       SSID Security     Ch [...] BSSID
yournetwork WPA2 PSK      6 [...] 20:4e:7f:ff:fe:fd [...](AES2),[...]
% ./airport -I
[...]
            SSID: yournetwork
        Security: WPA2 PSK cipher: AES2

These steps use a command line utility called airport that comes with Apple80211.framework; you can see other commands with ./airport --help. The first airport command scans for access points. In place of the SSID yournetwork, you should see the name you assigned your router in its settings; its channel may or may not be six, its BSSID will almost certainly differ from this example, and you may see any number of other access points your PowerBook is in range of. What you should not see under ordinary circumstances are multiple copies of your network SSID with the same BSSID on multiple channels. If you do, something might be wrong!

The second airport command tells you what access point you are currently associated with. Verify the SSID matches the one you expect and that the security is WPA2 and AES2 (notice this appeared in the first command, too). Periodically recheck these commands as you get suspicious-looking new neighbours or black vans and helicopters show up on your block. Consider replacing your router if there is no update; this won't help your Power Mac, but it would potentially help other connecting devices that were themselves updated.

If you are connecting to a router you can't control, like a public access point in your coffee shop or hotel, you should treat any WiFi connection you make to it as if it were open and unencrypted and that an attacker can see and forge any traffic you generate. Though the commands above can give you an idea of your instantaneous risk, even if AES-CCMP is in use a wily attacker may choose to deploy their malicious access point intermittently or when you're not checking, so your best defense is to encrypt what you send and receive. Only use https:// URLs and prefer sites that use HTTP Strict Transport Security and HTTP Public Key Pinning, both of which TenFourFox supports, so that an initial HTTP-to-HTTPS redirect is less likely to be intercepted and stripped and it is much harder for an attacker to impersonate a HPKP-secured site. There are still some sophisticated ways to get around even these added precautions, however, so if you need to do something highly secure like banking or taxes I'd strongly advise going home and plugging into your router's Ethernet ports directly. Even a VPN might not be enough.

Meanwhile, I guess I'll be rewriting that Power Mac security rollup post again. Assuming the current state of AES-CCMP holds, though, there may be a way to design a tool to programmatically/automatically detect a forged connection even if the underlying vulnerability cannot be corrected. I have a few ideas about that. More later.

Thursday, October 12, 2017

OverbiteWX now available from AMO

OverbiteWX, the WebExtensions Gopher protocol add-on for Firefox, is now available from Mozilla Addons.

OverbiteWX is only for Firefox 56+. TenFourFox and Firefox 52ESR can still use OverbiteFF, which is a superior add-on in every respect for obvious reasons.

New OverbiteWX users, please read the directions thoroughly! And Mozilla, how about a spec for bug 1247628 so we can finally get TCP sockets working in WebExtensions? We can't even scratch our itch because you won't tell us what type of scratching you'll accept!

Thursday, October 5, 2017

Various and sundry: OverbiteWX is coming, TenFourFox FPR4 progress, get your Talos orders in and Microsoft's new browser has no clothes

This blog post is coming to you from a midway build of TenFourFox FPR4, now with more AltiVec string acceleration, less browser chrome fat, some layout performance updates and upgraded Brotli, OTS and WOFF2 support (current to what's in mozilla-central). Next up is getting some more kinks out of CSS Grid support, and hopefully a beta will be ready in a couple weeks for you to play with.

Meanwhile, for those of you using the Gopher enabler add-on OverbiteFF on Firefox, its successor is on the way for the Firefox self-inflicted add-on apocalypse: OverbiteWX. OverbiteWX requires Firefox 56 or higher and implements an internal protocol handler that redirects gopher:// URLs typed in the Firefox omnibox or clicked on to the Floodgap Public Gopher Proxy. The reason I've decided to create a new one instead of uploading a "WebExtensions-compatible" version is because, frankly, right now it's impossible. Because there is still no TCP socket API in WebExtensions, there is presently no way to implement a Gopher handler except via a web proxy, and this would be unexpected behaviour to an OverbiteFF user expecting a direct connection (which implemented a true nsIChannel to make the protocol once again a first class citizen in the browser). Since this means Gopher URLs you access are now being sent through an external service, albeit a benign one I run, I think you at least should opt in to that by affirmatively getting the new extension rather than being silently "upgraded" to a new version with (despite my best efforts) rather less functionality.

The extension is designed to be forward compatible so that in the near future you can select from your choice of proxies, and eventually, once Someone(tm) writes the API, true socket access directly to the Gopher server of your choice. It won't be as nice as OverbiteFF was, but given that WebExtensions' first and most important goal is to reduce what add-on authors can do to the browser, it may be as good as we get. A prototype is available from the Floodgap Gopher server, which, if you care about Gopher, you already can access (please note that this URL is temporary). Assuming no issues, a more fully-fledged version with a bit more window dressing should be available in AMO hopefully sometime next week.

TenFourFox users, never fear; OverbiteFF remains compatible. I've also been approached about a Pale Moon version and I'm looking into it.

For those of you following my previous posts on the Raptor Talos II, the next-generation POWER9 workstation with a fully-open-source stack from the firmware to the operating system and no x86 anywhere, you'll recall that orders are scheduled for fulfillment starting in Q4 2017. And we're in Q4. Even though I think it's a stellar package given what you get, it hasn't gotten any cheaper, so if you've got your money together or you've at least got a little headroom on the credit card it's time to fish or cut bait. Raptor may still take orders after this batch starts shipping, but at best you'll have a long wait for their next production run (if there is one), and at worst you might not get to order at all. Let Raptor know there is a lasting and willing market for an alternative architecture you fully control. This machine really is the best successor to the Power Mac. When mine arrives you'll see it first.

Last but not least, Microsoft is announcing their Edge browser for iOS and Android. "Cool," sez I, owner of a Pixel XL, "another choice of layout engines on Android" (I use Android Firefox, natch); I was rather looking forward to seeing the desktop Edge layout engine running on non-Microsoft phones. Well, no, it's just a shell over Blink and Chromium. Remember a few years ago when I said Blink would eat the Web? Through attrition and now, arguably, collusion, that's exactly what's happening.