I’ve been arguing with my web hosting company about their use of RC4. Like many enterprise networks they aren’t consistent across all their servers with respect to available ciphers and such. It appears that all customer servers support TLS_RSA_WITH_CAMELLIA_256_CBC_SHA and TLS_RSA_WITH_CAMELLIA_128_CBC_SHA, in addition to TLS_RSA_WITH_RC4_128_SHA (although the latter is preferred over the other two) but their backend controlling web servers only support RC4. This is a problem if you are handling crypto (keys) (and other settings) over a weak encryption path to better secure your web service as you have essentially failed due to using the weak encryption to begin with.
So what’s wrong with RC4?
It’s been known for a while (years!) that RC4 is not a good encryption cipher. It’s broken and there are several attacks that are available. So why is it being used so frequently? In a word: BEAST. RC4 was the only stream cipher available that can combat BEAST and so it became the standard for all TLS connections. It’s not clear which attack vector is worse: BEAST or the weak RC4.
In recent months most Internet browsers have implemented the workaround n/n-1 to fix the BEAST vulnerability. With the fix in place it should, once again, be safe to use block ciphers and, thus, get better encryption ciphers (better protection). There have been many people and organizations talking about the need to get rid of RC4 now since it is a bigger threat to web security. Yesterday Microsoft released a security bulletin discussing the problem and urged all developers to stop using RC4. (Oh yeah, and they also want to stop using SHA-1 as well.) I usually think of Microsoft as trailing in the security field (lets face it, their products aren’t known for being secure ever since that whole network thing happened) so when they say that this mess with RC4 must stop it’s gotten to a point where we should have already done so.
So what are we waiting for?
I think, simply, we’re waiting for TLSv1.1 and TLSv1.2 to become mainstream. It’s not as if these technologies have just popped up on our radar screens, however, (they’ve been out since April 2006 and August 2008, respectfully) but there has been slow adoption of the two flavors of TLS. According to Microsoft, their products are ready for TLSv1.1 and TLSv1.2 (both IIS on and IE 11+). Firefox supports up to TLSv1.2 in 25.0 but you have to manually turn it on (it’s for testing) and OpenSSL (used for Apache) should support TLSv1.2 in its 1.0.1e release. It’s time to start pushing these better encryption mechanisms into operation… now.
Thought I’d pass along this research study, The keys to the kingdom, as I found it to be quite interesting (especially when you scan the entire Internet for your data). If you don’t understand the math explanation at the beginning just continue reading as you don’t need to have a degree in math and science to understand what’s going on.
This morning I was greeted with a blog post from the fine folks over at Qualys on how BEAST isn’t really still a threat (unless you are using an Apple product). BEAST, a vulnerability found in SSL and TLS 1.0, was discovered around this time a couple of years ago and put web users in a precarious position of using a poor cipher choice (RC4) or be vulnerable. Not to worry, however, as developers were able to come up with a solution to the problem (n/n-1).
So I mentioned the Qualys article in my $dayjob IRC channel where my always awake coworker provided information that Fedora is, in fact, still vulnerable to the attack. Thanks to a problem with pidgin-sipe connecting to a Microsoft server, the n/n-1 split was backed out of the NSS software leaving anything that depends on it potentially vulnerable (Chrome, Firefox, and Thunderbird to name a few).
There is a fix, although it’s not fantastic by any stretch of the imagination. By simply adding these two lines to your /usr/bin/firefox file the vulnerability should be fixed:
We added these two lines at line 36 and restarted Firefox. My way-too-awake coworker did a test and confirmed that it was working in his environment. Your mileage may vary.
Hopefully the fix for BEAST can be reapplied to NSS in Fedora soon as leaving users exposed can be dangerous.
Thanks to Hubert Kario for pointing me, and walking me, though this stuff before my morning coffee.
Update: 2013-09-12 @ 14:30 UTC
Apparently this problem will be persistent according to the NSS package maintainer. From the ticket:
I bit of information from the nss side of things. The nss disabling patch is not applied on Rawhide or f20, onlt applied on stable branches. After we branch Rawhide for the next fedora release and we enter in Alpha, I send emails to the fedora development mailing list telling them that NSS_SSL_CBC_RANDOM_IV=1 will be the default as they use updates-testing and ask for feedback on whether it causes problems. Twice they have said it still causes problems. There are still unpatches servers out there. Once we go beta I have to enable the patch again. f20 is entering Alpha soon so I’ll send that email again. I know this bug is for Firefox but I though worth informing you that we monitor this every six months for nss.
Update: 2013-10-10 @ 15:22 UTC
Update: 2013-10-17 @ 10:32 UTC
I believe this problem has been fixed (finally!) for Fedora 19 and beyond.
I went to sign an outgoing message tonight and my Gemalto USB Shell Token wouldn’t light up when I plugged it into my USB port. After doing the typical troubleshooting I am left with the thought that the device has given up the ghost. This isn’t a big problem because I saved the card the SIM came out of and I’m able to use my token on my personal laptop with a traditional card reader. My work computer, however, does not have one of these fancy card readers (maybe I can find my USB one somewhere?).
I can buy another Gemalto device but I’m wondering if there is a better device to use? I mean, the Gemalto lasted almost 500 signatures. But I guess I can now take advantage of the failure to try something else. Does anyone have any suggestions?
Someone recently asked what my GPG.conf file looks like since he hadn’t updated his in… years. Okay, let’s take a look and I’ll try to explain what each setting is and why I feel it is important. I’m not guaranteeing this as being complete and I welcome input from others.
This says that if a program needs a public key but it’s not in my keyring that it should automatically reach out to the keyserver (see below) and download it.
This says to use the GPG agent. I cannot remember, right now, why this was a good idea. Perhaps it isn’t?
auto-key-locate cert pka ldap hkps://hkps.pool.sks-keyservers.net keyserver hkps://hkps.pool.sks-keyservers.net keyserver-options ca-cert-file=/etc/ssl/certs/sks-keyservers.netCA.pem keyserver-options no-honor-keyserver-url keyserver-options auto-key-retrieve
Almost the fun stuff there. This is just setting up the keyserver that I wish to use (note the use of hkps instead of hkp).
default-preference-list AES AES192 AES256 TWOFISH SHA1 SHA224 SHA256 SHA384 SHA512 Uncompressed ZIP ZLIB BZIP2 personal-cipher-preferences AES256 TWOFISH AES192 AES personal-digest-preferences SHA512 SHA384 SHA256 SHA224 personal-compress-preferences BZIP2 ZLIB ZIP
Okay, the fun stuff. These are all the algorithms that I wish to use. If you setup your GPG key to advertise these then it will make it easier for others to use the most secure algorithms since they will already know what you can do. The first line just lists all the preferences. The second, third, and fourth lines actually provide the preferences in order of them being used. If you’ll note my preferred cipher is AES with a 256-bit key and my preferred hash (digest) is SHA with a 512-bit key. There are other options available and a quick
should provide what options are available to you. For instance, my current installation says that its supported algorithms are:
Pubkey: RSA, RSA-E, RSA-S, ELG-E, DSA
Cipher: IDEA, 3DES, CAST5, BLOWFISH, AES, AES192, AES256, TWOFISH,
CAMELLIA128, CAMELLIA192, CAMELLIA256
Hash: MD5, SHA1, RIPEMD160, SHA256, SHA384, SHA512, SHA224
Compression: Uncompressed, ZIP, ZLIB, BZIP2
I’ve omitted 3DES, MD5, and SHA1 from my preferences due to their weaknesses but I could still use them according to my GnuPG software.
Again, this wasn’t meant to be a strict “thou must do this to be secure” but rather a “this is what I’m doing” sort of thing. I’d appreciate feedback!
I was recently introduced to a privacy issue when refreshing your OpenPGP keys using GnuPG. When refreshing your public key ring using a public key server GnuPG will generally use the OpenPGP HTTP Key Protocol (HKP) to synchronize keys. The problem is that when you do refresh your keys using HKP everyone that you maintain in your public key ring is sent across the Internet unencrypted. This can allow anyone monitoring your network traffic to receive a complete list of contacts in which you may hope to use OpenPGP.
The fix is quite simple: in your gpg.conf file make sure that your keyserver entries include hkps:// instead of hkp://. This will force GnuPG to wrap HKP in SSL to keep the key exchange private.
Much of our daily lives are contained within our smartphones and computers. Email, text messages, and phone calls all contain bits and pieces of information that, in the wrong hands, could harm our privacy. Unfortunately many people either don’t understand how vulnerable their data is when sent across the Internet (or another commercial circuit) or just don’t care. While I don’t have much to say for the crowd in the latter category (can’t fix stupid) I do try to help people in the prior category understand that any network outside of their control is fair game for pilfering and that basic protections need to be taken to protect themselves. While I’m not going to dig into how data can be intercepted (there are plenty of articles out there on the subject) I would like to talk about how one can use tools to protect their data when using an Android smartphone.
Until recently email was the only easily-encrypted mode of communication. Most people didn’t have the means of encrypting their phone conversations and certainly not their SMS messages (unless you happen to be using a SME-PED, but those things are terrible in other ways). Now, Whisper Systems have released two open source programs that allow you to protect your communications. The first is called “RedPhone”. This program encrypts your phone conversations and allows you to converse securely. The second program is called “TextSecure” and encrypts text messages using authenticated, asymmetrical encryption.
I like the way TextSecure manages keys and allows you to verify the user’s key directly so you can establish trust. RedPhone appears to use the trust in the phone number for authentication. RedPhone also provides encryption opportunities when the distant party also has RedPhone on their device which is a nice feature that I wish TextSecure also provided. Both of these programs are very easy to use and need very little configuration.
TextSecure also provides an encrypted container for all your text messages so that your text messages are secure if the attacker has physical access to the device.
And OpenPGP is still a great option for protecting your email communications but that is a topic for later.