Security - 2

Mathy Vanhoef and Frank Piessens are both decorated security researchers from KU Leuven, Belgium. On an otherwise slow Sunday, 15th October 2017 Alex Hudson dropped a bombshell: Mr. Vanhoef and Mr. Piessens figured out a way to bend the authentication envelope, making WPA2 broken. Authors coined this as a Key Reinstallation AttaCK. Whaat?! Darn!

Looks like the release was planned carefully. OpenBSD had the fix on 1st March 2017. That's over 6 months earlier. Also Microsoft had a whiff of this flaw in the early phase as they managed to release a patch already. The complete vendor list can be seen @ cert.org. Its a sad read, that.

The information is at https://github.com/kristate/krackinfo and contains a very simple message:

Unless a known patch has been applied, assume that all WPA2 enabled Wi-fi devices are vulnerable.

Ok, that sounds really bad. To cut all the FUD and blah blah out, what's the big deal?

• This is a Wi-Fi client attack
  • Explanation: The entire KRACK thing works by spoofing as your router to your client. After the attacker manages to lure your laptop or cell phone into connecting to a fake network, it acts as a man-in-the-middle reading your transmissions.
  • You cannot hide your network information. If you transmit or read transmissions, somebody can read that. That's the bad part about radio transmissions, they travel to everyone.
  • The only way to hide your radio transmissions is to turn Wi-Fi off.
• Anybody attacking YOU needs to be in same physical area than you
  • Explanation: A random guy from The Net cannot attack you. They need to travel to where you are.
• Regardless of what, attacker will not gain your WPA password
  • Explanation: This attack is about fooling your laptop/cell phone/refridgerator to talk to a malicious wireless router. It does not extract your Wi-Fi network password while doing it.
  • So, this is almost as bad as the WEP weakness back in 2001. In that particular incident any random body could just crack their way to your network by figuring out what your password is. And then it was possible to read any captured past or future transmission. KRACK works only forwards, your historical transmissions are safe.
• If you are using TKIP or don't know if you are using it - you're doomed!
  • Explanation: TKIP, or Temporal Key Integrity Protocol is weak anyway. You shouldn't be using that in the first place!
• If you are using Android or Linux - you're most certainly doomed!
  • Explanation: The implementation in Linux (Android is a Linux, you know) is especially flawed! Attacker has easy means of forcing any client to fake router and then force your encryption key to something the attacker can predict, thus being able to read your traffic in real-time or introduce new data packets and spoof them to originating from your Linux/Android. That's bad, really bad!
• If you are not using Linux, and are using AES-encryption - you're doomed!
  • Explanation: Yes, if attacker can lure you to use the faked router, your transmissions can be read.
  • Examples of non-Linux clients include, but are not limited to: Windows, macOS, iOS.
• My router has Linux or I got my router free when I got my Internet connection and I don't know what operating system it has - you're doomed!
  • Explanation: This is not about your router. This is about attacker faking to be your router. Your router won't be attacked, but attacker will spoof traffic to it.
• If a random attacker can read all my traffic and can inject new transmissions spoofing as you, is that bad?
  • Explanation: Yes it is. Attacker can attempt to stop you from using SSL/TLS and there are number of scenarios where that can happen, so all your precious passwords, credit card numbers and other secrets can leak. However, there are number of scenarios where that is not possible. Still, if attacker has your encrypted traffic, other means of decrypting it exist.

As you can see from the above list, there are quite a few scenarios which end you in the 'you're doomed!' -state. So, assume that you are or will be!

The relevant question remains: Is there anything that can be done?
Answer is: Not really

Just wish/pray that your particular vendor releases fixed firmware sometimes soon. Most Android vendors won't.

This is a rare event: somebody is actually improving my privacy and I don't have do do anything. Nice!

Apple is introducing intelligent tracking prevention technology in upcoming Safari 11. They're pretty radical in their cookie blocking, they're "deleting even first-party cookies if it's been more than 30 days since you interacted with the website that set the cookie". Naturally corporations depending on tracking you don't much like that, but Apple's response is: Tough luck, privacy comes first. So, it's natural that advertisers don't want you to use Safari or know how to make their tracking harder.

Safari 8, 9 and 10 will block 3rd party cookies as default. You can opt out of that, but it's just ridiculous. I strongly advice against that. Nobody really needs 3rd party cookies, they are never up to no good. Couple years back a Swedish web shop I frequently purchased movies from changed their on-line payment vendor and they actually used 3rd party cookies for the payment transaction. I took a pause over 2 years before doing business with them again. Their current payment system works correctly.

Firefox allows 3rd party cookies, but there is a setting:

Same thing with Chrome, it allows 3rd party cookies, but you can disable it from well hidden setting:

What's really cool with Safari 11, that they'll move tracking protection to the next level. There is a "special" treatment for well-known 1st party cookies too. This is top notch stuff and it outperforms most add-ons and extensions. Really nice!

In my previous post, I was (not so) politely asking DocuSign to admit e-mail addresses leaking.

Finally, they did! They posted Update 5/16/2017 - Update on Malicious Campaign.

Q: What information was impacted?
A: It was a list of email addresses stored in a separate, non-core system used for service-related announcements.

That is something they should have done a week ago, but I guess we have to settle with that.

Btw. I got my hands on the payload VB:Trojan.VBS.Downloader.ACR as named by F-Secure. As many have reported before, it's a MS Word document with a macro in it. The VBA-thingie de-obfuscates a "picture" embedded into the .doc and injects that directly to memory to be executed. I really didn't want to waste the ton of time investigating the actual malware, its bad, I know that without looking. Its just another reminder of how dangerous the VBA-macros are, they can call any system call from Windows kernel and do really complex hacks, like any real executeable would do.

On 9th and 10th of May I got really weird spam from alleging to originate from DocuSign. The attempt to lure me to hit the link was lame and I didn't believe the communication to be valid at any point. There was no DKIM-signature in the e-mail headers. I know for a fact, that real DocuSign e-mail has that in them. So, any quick analysis of the mail originating from USA and Canada was yelling SPAM! instantly.

The subject of the two first ones was "Completed: Wire Transfer Instructions for docusign Document Ready for Signature" and the third one "subpoena from WEX inc". All of them attempted to get be to download a file from an already shut down websites. All three domains used were 12 characters long .ru-domains and looked random strings to me. I don't know if the words had actual meaning, they just looked random to me. The URLs had my e-mail address Base64-encoded to allow the perps to track any incoming clicks for active e-mails.

Of course plenty of others got the same junk as me, there is a support thread at DocuSign's site: Strange email from Docusign - is it legit? In an answer to that one, the official statement says: "However, DocuSign’s core platform has not been hacked, and our customer data remains secure". In that comment thread there are other people, who don't believe that. I'm one of them.

Why would I make such a bold claim? Well... easy. The e-mail address I'm using in DocuSign is unique. I'm not using that specific address ANYWHERE else. So, people of DocuSign, explain me where the address leaked if not from your system! I guess they claim, that it leaked from one of my systems. But then again, the same thing must have happened for number of other people too. Also, I use hundreds of different addresses for this purpose, to reliably determine which system leaked my information. Any even remotely regular user has their joe.user@mail.com-address registered to dozens and dozens of systems, so they have no possible way of knowing who leaked the data, I do.

I'm urging DocuSign to step forward with a truthful statement about the breach. Their current lies I'm not bying.

Update 15th May:

DocuSign got hacked also two years ago. Same thing happened, they deny any data leakage. Without proof, I feel like throwing unfounded wild allegation here: they have been compromised for over two years now.

In the support discussion thread couple of other people complaining about same thing than I do: the e-mail address isn't being used by anything else than DocuSign, still they're receiving junk to that particular address. How come?

CAcert is my favorite source of certificates. It has been that for years. The buggy Let's Encrypt I loathe, their poorly tinkered Python-scripts won't work and after couple hours of unnecessary fixing of their bugs, the scripts decide to write to my configurations. So, those guys really don't have a clue what they're doing.

However, CAcert isn't doing much better. Their root certificate is still MD5-signed. Argh!

CAcert's claim is, that "Severe weaknesses have been found in MD5, but at present they do not open vulnerabilities for X.509 certificates". But nobody else is buying that. It's just that this international non-profit organization is light on resources and they want to get his one done right. They just don't seem to be able to squeeze a re-signed root certificate out.

Update 20th Apr 2018: There is a follow-up post about installing this into iOS-device.

Briefly on certificate hashes

A X.509 certificate needs to be signed to make sure it originated from the Certification Authority announced in the certificate. Since the root certificates are typically self-signed, they are at the end of the certification chain, there is no other authority to validate them. That's why the hash of the signature is published at the CA's website. In case the hash doesn't match, it is possible to notice that somebody modified the signature.

What others are doing: Expiring MD5 and SHA-1 hash algorithms

Apple iOS, Oct 13, 2011, About the security content of iOS 5 Software Update

CVE-ID: CVE-2011-3427

Description:
Certificates signed using the MD5 hash algorithm were accepted by iOS. This algorithm has known cryptographic weaknesses. Further research or a misconfigured certificate authority could have allowed the creation of X.509 certificates with attacker controlled values that would have been trusted by the system. This would have exposed X.509 based protocols to spoofing, man in the middle attacks, and information disclosure. This update disables support for an X.509 certificate with an MD5 hash for any use other than as a trusted root certificate.

Microsoft, Aug 13, 2013, Update for deprecation of MD5 hashing algorithm for Microsoft root certificate program

On affected releases of Microsoft Windows, security update 2862973 requires that certificates no longer use the MD5 hashing algorithm. Microsoft products or third-party products that call into the CertGetCertificateChain function will no longer trust certificates that have MD5 hashes.

Microsoft, Nov 4 2015, SHA-1 Deprecation Update

We announced that Windows will block SHA-1 signed TLS certificates starting on January 1, 2017. In light of recent advances in attacks on the SHA-1 algorithm, we are now considering an accelerated timeline to deprecate SHA-1 signed TLS certificates as early as June 2016.

Google, Dec 31 2015, SHA-1 Deprecation: No Browser Left Behind

After December 31, 2015, SSL certificates that use the SHA-1 hash algorithm for their signature will be declared technology non grata on the modern Internet. .. over the course of 2016, will begin issuing warnings and eventually completely distrust connections to sites using SHA-1 signed certs.

Apple, Sep 20 2016, MacOS & Safari SHA-1 deprecation policy

Apple hasn't made any specific announcements here. The nearest we've come is a general warning in WWDC 2016 Session 706 What’s New in Security:

• SSLv3 cryptographic protocol and the RC4 symmetric cipher suite are no longer supported, starting at the end of 2016. It's recommended that you stop using the SHA-1 and 3DES cryptographic algorithms as soon as possible.

CAcert SHA-256 re-sign project

Altough CAcert guys think that there is no security flaw in MD5-signed certificates, they chose to do something about this. They managed to get the existing root certificate re-signed with SHA-2 on number of occasions. The most recent one is: root certificate re-signed. This was executed successfully on 2016-03-12

The result is kinda published, it's not publicly available, but if you're willing to go the SHA-256 project's SVN repository at http://svn.cacert.org/CAcert/SystemAdministration/signer/re-sign-2016/outputs/, the result is available.

Go there! Get it! Use it!

Installation instructions

Should I install the intermediate certificate too?

No.

The idea with web server certificates is, that you establish trust to root certificate. All certificates are issued from intermediate-CA, which certificate can be revoked at any given time. That's why the intermediate certificate needs to be deployed with the server certificate. This is something many system admins keep misunderstanding.

Which keychain / store the CAcert root certificate should be installed?

My preference is always to install new root certs into system-wide keychain / store. That way any human users (me and possibly others) or system/daemon users get the new cert at once.

macOS

For this to work, you'll need

• root access to your Mac
• old MD5 signed root cert
• new SHA-2 signed root cert

First disable trust to the old cert:

security remove-trusted-cert -d CAcert-root.crt 

Remove the old cert by it's signature:

security delete-certificate \
 -Z 135CEC36F49CB8E93B1AB270CD80884676CE8F33 \
 /Library/Keychains/System.keychain

Add and trust the new cert:

security add-trusted-cert -d -r trustRoot \
 -k /Library/Keychains/System.keychain \
 root_256.crt

The important point in macOS is to remember, that adding a root certificate to keychain doesn't make it trusted. You'll need to implicitly tell an added certificate, that you trust it too. That's kinda weird, but ... some smart guy at Apple designed that so.

Windows

For this to work, you'll need

• administrator access to your Windows
• new SHA-2 signed root cert

Remove MD5-signed:

certutil -delstore Root 135CEC36F49CB8E93B1AB270CD80884676CE8F33

Add and trust the new cert:

certutil -addstore Root root_256.crt

Linux

Ah, there are too many distros out there.

Any typical approach would be to place the file into /etc/pki/tls/certs/ and symlink the certificate's OpenSSL hash 99d0fa06.0 into it.

iOS

... This one I'll get back in a later post.

Update 2nd December 2017:
After receiving comments to this blog post, I started doing more digging and there is a new blog post about EBN scam.

Today I got yet another snail mail scam as a printed letter. It looks like this:

The scammers are claiming, that they are missing my corporate VAT ID. Hm. That's strange. All the other information they got from Finnish Business Registry (ytj.fi). But as they are missing my valuable VAT-number, I'll need to fill it into a pre-filled form and add a binding signature. I'm not exactly sure, what exactly should I do with this form after signing it, but such a form was sent to me.

Caution! Scam here is in the monotype-font part (see above page 2):

Order: We hereby confirm the accuracy of our company' s data as per the information given above and we hereby place an order with DAD GmbH (Publisher) to publish them in a graphically highlighted form on www.e-b-n.eu according to the general terms and conditions printed overleaf.

We accept the advertisement' s annual costs of 890 Euro, which are payable in advance upon receipt of the invoice. We acknowledge that the contract is valid for the next three years and subsequently will be automatically extended annually unless we provide a written notice requesting termination of the contract, this being no later than three months before the expiration of the contract's term.

We are only able to revoke the contract by registered letter within fourteen days of the order date; whereby the date of postage is decisive. We authorize the Publisher to use contents found on our website for the layout of our insertion.

We acknowledge Hamburg-Mitte as place of performance and jurisdiction and that German law is solely applicable. We confirm that prior to this order placement we had no business relationship with the Publisher. We agree that our company's data will be stored electronically.

Whoa! That's a long and difficult to read. All that easier to miss the part with "We accept the advertisement' s annual costs of 890 Euro, which are payable in advance upon receipt of the invoice". Oh! I thought this was some kind of "final reminder", not an order nor invoice.

There is an actual website http://e-b-n.eu/ with all collected publicly available business information in it.

To make this scam more believable, scammers added actual addresses and phone numbers in Hamburg, Germany. I don't know if neither of them are legit. I do know, that German business registry doesn't have Commercial Register, Companies' Section, Hamburg Local Court, Record No. 88115 with name of European Business Register. Actually, that record number belongs to somebody completely innocent. Also the German VAT ID of 813739877 seems to belong to somebody, but I don't know how to do a lookup on German VAT IDs, so I don't know whose VAT ID it is.

By googling the VAT ID, I found pretty much the same letter sent to Italian doctors "Registro Italiano Medici: attenzione alla modulistica". There is a scanned PDF of the letter. Funnily, it has the same German VAT ID, and Mrs. Daniela Kunst as the managing director of EuroMedi (http://euromedi.eu/). The price is bit cheaper, only 877 €. Also the website is hosted in the exactly same IP-address in Köln, Germany. Also, there is Deutsche Internet Kartei and Internet Register Österreich with same VAT ID and managing director, but on a different server.

Based on a report by (Caution: European Central Register of VAT Registration Numbers is a scam) German law firm, this scam has been going on since 2013. So, looks like their business is lucrative and nobody seems to be able to stop them.

In the previous part we established that any certificate authority can issue a certificate to any website, even if the website admin doesn't want them to do that. This post is about technical measures attempting to monitor certificate authorities' actions.

Details that need to be addressed somehow

A certificate lifecycle is very simple. One is issued by a CA, it is used by a server and eventually it expires. When things go sideways, the server administrator may want to revoke an otherwise valid and good certificate, so there needs to be a mechanism to handle a single special case. So, two actions: issuance and revocation. Everything else is handled by itself.

To monitor certificate issuance and revocation, following requirements apply:

• Monitor when somebody issues a certificate for your website
  • Preferably everybody in the entire Internet needs to know about this instantly. You decide if the issuance is good or bad thing.
• Man-in-the-middle using a fake certificate
  • When a subset of users is being targeted, clients need to know that the certificate being offered doesn't belong to the server the certificate supposedly is for.
• No trusted parties
  • This is something we learned from X-Files (the TV-show), trust no one! Any possible parties needed in verification must be assumed to be offering false information, or alternatively it needs to be digitally tamper-proof.
• Instant deployment of a new certificate
  • When you setup a server and a certificate to it, how do you notify everybody about that? Preferably no notification is needed.
• No need to modify servers
  • How is the actual server setup done. What parts you need to add there. Preferably none.
• No additional requests during connection
  • When a client requests data from your server, which additional requests to another parties are needed? Preferably none. Remember, that this type of additional request need to succeed in a split-second to make the decision wheter to open a connection to a requested server or not.

(This list is actually "borrowed" from certificate transparency tech comparison. Its just so comprehensive, so I had no other option than to use it.)

Certificate revoke list, aka. CRL

This is what we have since dawn of SSL. The idea is to go request the issuing CA and see if an already issued valid certificate is revoked. This information is published in a revocation list. The obvious problem is that revocation information doesn't happen instantly, and actually most browsers don't ever check a CRL.

To distribute the CRL-information, an issued certificate is supposed to have an URL to CRL (typically they do) and a client is supposed to be downloading that data periodically (typically they don't). In reality that doesn't work, as nobody wants to spend their precious time and bandwidth for downloading a ever-growing list of bad certs. To address that, there is a modern approach, Online Certificate Status Protocol or OCSP. It is supposed to be much faster operation with minimal bandwidth usage.

Neither of these really work well because of the need for an additional request. Also OCSP has a major fault, that a reply can be stored and "played back" on a query, so the reliability is more than questionable.

Certificate Transparency

This is the newest one and it has a good chance of becoming the commonly accepted method for tracking certificate issuers' actions. There is an RFC 6962 defining Certificate Transparency and the source code is distributed as open-source allowing anybody to see how it works and do their own audit on it. Originally the project is initiated by Google, but number of CAs already accepted the technology including Symantec, Digicert. and Globalsign. One reason for wide adoption is, that Google (the author of Chrome browser), made an ultimatum, that the seriously expensive Extended Validation certificates need to have CT signature in them for Chrome to accept them as valid.

Internally CT works with a Merkle hash tree, something that BitCoin uses internally. So, it is safe to say, that this technolocy is a blockchain. Blockchain as a tech is quite new, but robust and reliable. The good thing about Certificate Transparency is, that this tech supports all requirements from above list. All a browser needs to do is periodically load the CT logs and during a connection, read the CT-signature from server's certificate, and based on that a browser can instantly verify or decline the server's certificate.

As mentioned, Certificate Transparency needs to be supported by your browser. Being a Google project, of course Chrome does support CT since version 35. Mozilla Firefox has announced support for CT, but at the time of writing there is no implementation yet. Microsoft doesn't support CT and they announced that that they're doing something of their own for IE11, naturally their new Edge browser doesn't support CT either. So that pretty much lands Chrome being the only browser really supporting this. The good thing is, that there exists many server-to-server monitors, for example Certificate Transparency Monitor.

Not accounting for poor browser support, another weakness CT has is that every certification authority has to include CT-signature in their issued certificates and publish their CT logs to general public.

DANE

DNS-based Authentication of Named Entities, or DANE is the first serious attempt to enforce certificate's ownership. The tech is described in RFC 6698 and multiple accompanying RFCs to clarify details of it's implementation. However, DANE hasn't received much public acceptance.

This is how Wikipedia defines DANE: "DANE enables the administrator of a domain name to certify the keys used in that domain's TLS clients or servers by storing them in the Domain Name System (DNS). DANE needs the DNS records to be signed with DNSSEC for its security model to work."

As the above definition says, for DANE to work, a prerequisite is functioning DNSSEC. Nobody has that! Some stats at http://rick.eng.br/dnssecstat/ show that the situation is horrible. So, no DNSSEC, no DANE. Also DANE fails on two other things: additional requests are needed to DNS during connection and you need to trust the DNS-server response. DNS data can be forged or poisoned, so there's that.

Pinning

Certificate pinning, or HTTP Public Key Pinning is an extension header of a HTTP-response. This is yet another Google-project, but its not widely adopoted. The idea for the web server to send public key information on every response, then the web browser is supposed to locally store the information for specified time. Then any subsequent responses from that same server are supposed to have the same information in them what was cached before. Weakness is that, the initial request needs to go to the real server. If your traffic was "man-in-the-middled" already at that point, you won't get any warnings.

Pinning is supported in Chrome and Firefox, but as Microsoft nor Apple support this, it is missing from IE, Edge and Safari. There is a funny mistake in Microsoft Edge's feature list as it states Firefox not supporting pinning, but Firefox was one of the early browsers supporting this feature.

Weaknesses here are, that it requires changes both on server and client sides. Also, when the certificate is legitimately changed, there really isn't a sensible mechanism to inform about that.

Collecting every web server certificate, aka that thing Google is doing

As you may remember from part 2 of this series, most of the rogue certificates issued are for Google services. So, they're fighting this by collecting all the certificates they see. They have a massive army of bots crawling web servers all the time. Google is also publishing their findings in a Certificate Transparency log for any interested parties to see. As mentioned before, there are publicly available non-Google services monitoring the CT-logs for abnormal changes.

This is very simple idea, if you see your certificate listed there, the certificate was issued by your request or somebody else's. It should be rather simple task to determine which one was it.

Anybody can use the human interface at Google Transparency Report site.

The future?

None of these technologies is really either useful, or widely adopted by major vendors. Fact remains: due to number of past incidents Certificate Authorities need to be monitored, supervised and publicly scrutineered. The best thing to attempt is to add some transparency to their actions. Which technology that would be is yet to be seend. What worries me is Apple's and Microsoft's total ignorance for this matter. I guess they'll need to be targeted first to wake up from their deep sleep.

This is the last part of my HTTPS-series. First part was about basics of trusted certificates and second part part was about misappropriation of trust.

In the previous part we established the fact, that for HTTPS to work as intended, you as a web browser user need to trust your browser vendor's decision to trust the certificate authorities issuing the certificates to web server maintainers. This post is about when things go wrong, the chain-of-trust is broken and organization's actions are deemed not so trustworthy.

Known CA security incidents in chronological order:

• 2010 (multiple incidents): Key Internet operator VeriSign hit by hackers
  • There isn't much information available on this, but they disclosed this on their quarterly report.
  • "Are we finally ready to accept that the certificate system is completely broken?"
    - Bruce Schneier, on his blog
• March 2011: Hackers target Google, Skype with rogue SSL certificates
  • Comodo was cracked, and certificates for orgs like Google were issued without them knowing about it.
• August 2011: Hackers stole Google SSL certificate, Dutch firm admits
  • DigiNotar was cracked and Google certificates were created. Later DigiNotar went bankcrupt as they reputation was gone.
• December 2013: French Government ANSSI responsible of a MITM against Google SSL-TLS
  • French CA issuing Google certificates
• July 2014: Indian government agency issues fake Google certificates
  • This is really bad! A government agency in India issuing Google certificates. I'd understand a company doing that, but government... no.
• December 2014: Turkish Certificate Authority screwup leads to attempted Google impersonation
  • Turkish CA issuing Google certificates
• March 2015: Google to drop China’s CNNIC Root Certificate Authority after trust breach
  • A Chinese CA issuing Google certificates.
• September 2015: Symantec employees fired for issuing rogue HTTPS certificate for Google
  • Inside job at Symantec, guys wanted to issue Google certificates
• October 2016: Distrusting New WoSign and StartCom Certificates (on Mozilla and on Google)
  • WoSign issued certificate for GitHub, yet another inside job.

As you already figured out the pattern. Anybody can issue any certificate for anybody. This many-to-many pattern isn't very trustworthy. Also, there seems to be more activity during the past two years or so, there is clearly more interest in gaining access to somebody's certificate.

In part 1 of my HTTPS-series it was established, that a X.509 certificate cannot identify the server. Now that cert-business sells certificates with a claim, that they have "verified" the request and the owner is who they claim to be, the above list tells another story. Nasty things happen when there is no verification, no real customer, but a malicious act of issuing a certificate for own cracking purposes.

Other acts of mistrust:

• January 2015: Gogo Inflight Internet serves up 'man-in-the-middle' with fake SSL
  • Inflight service provider goes man-in-the-middle on purpose. Of course all bad deeds can be wrapped into good intentions, they wanted to "protect the bandwidth usage".
• February 2015: Lenovo PCs ship with man-in-the-middle adware that breaks HTTPS connections
  • Lenovo laptops were pre-installed with a certificate used for snooping your HTTPS-traffic. The thing is: if anybody can inject a trusted root certificate to your computer, you won't notice that somebody is reading your encrypted traffic.
• November 2015: Dell does a Superfish, ships PCs with easily cloneable root certificates
  • Yet another pre-installed certificate making man-in-the-middle. Every computer had same PKI installed making anybody able to eavesdrop your carefully encrypted traffic.

These acts are as evil, altough different by nature, but target the same thing: to gain access to your encypted data.

Ok, what's the risk here?

In practice, what is the threat here? What are those "nasty things" that can happen?

The incidents where new computers had a pre-installed trusted certificate, or your traffic was forced via man-in-the-middle -proxy are easier to address. Without you realizing it, all your encrypted traffic is directed to a party faking to be your intended target. Man-in-the-middle just de-crypts your passwords and credit card numbers and passes the traffic forward to the real target server acting as you. So, there is an obvious direct risk, that your traffic isn't secure at all.

Somebody issuing a trusted rogue Google certificate is bit more complex. A certificate itself isn't too dangerous, but in a scenario where the outgoing traffic from your computer is re-directed to a rogue server having the certificate you won't be able to tell the difference. How somebody's traffic can be redirected can be done locally, by changing your DNS-settings or remotely attacking the DNS-server your're using. Both cases are seen in real life. Nevertheless, it is almost impossible to know that such a change has been made and you go to a fake "google" server, enter your password without realizing, that somebody else is in possession of your login credentials. These cases haven't been publicly reported, but if anybody manages to pull that one off, it would be really really bad. Ultimately, there is only indirect risk, that you may lose your secure data.

Ok, this insecurity is horrible, isn't there anything we can do?

Yes.

There are a number of technical innovations trying to govern the certificates. However, none of them are widespread nor commonly accepted. This leaves everybody at the mercy of certificate authorities and their actions.

I'll address those technical measures in my final part of this HTTPS-series.

Three years ago I was inspired by Scofield (or Mr. Harri Hursti) when he claimed that SSL is broken and it cannot be fixed. See the post for details. In reality tech can be fixed, my previous HTTPS-post is about shortcomings and fixes of TLS-encryption. This time I'm writing about another type of HTTPS-shortcoming, trust. This is between humans and is much much harder to fix.

Ok, most users don't see the difference between HTTP and HTTPS. They simply don't pay any attemtion if their address-bar has the lock in it or not. Those rare who do make the distinction between encrypted and non-encrypted web sites are blissfully ignorant about the inner workings of HTTPS. They don't understand the concept of a X.509 certificate nor the need for one. A certificate is needed to (I'm quoting Wikipedia article here) certify the ownership of a public key by the named subject of the certificate. The ownership of a key is important, it is used to make sure the communication parties are the same who initiated the connection. Without that, the security could be easily breached with a man-in-the-middle -attack.

What the certificate isn't designed is to identify nor verify the certificate holder. Technically, the certificate has a suitable field name subject. In HTTPS-certificate, it contains the hostname (or domainname in a wildcard certificate) of the server a secured connection is initiated to. If a certificate is used on a different server, the hostname used for connection and issued in the certificate won't match, and the lock won't "lock" or "go green" depending on your choice of a web browser.

The part where trust comes into play, is because the system is built so, that somebody issues the certificate. There is a chain of certificates to follow up to a root certificate to somebody who has authority to issue them. Any newly generated certificate is untrusted by your browser by default, unless the issuer root certificate is pre-added to your browser. That's where the certificate business (read: money) is. A certificate issuer has gone trough the hard work of pre-installing their certificate to all commonly used web browsers so that some website owner can come in and purchase a certificate from them and it will work and be trusted by any website visitors. What happens here is, you as the website visitor implicitly trust the website you are visiting, because somebody you don't know said they're who they announce themselves to be and they promised to be ok when asked about it. Of course browser and operating system companies play along with this, they do their due diligence and accept requests to distribute those root certificates to establish trust between the issuer and a website.

That's a bold request! Why should I trust somebody whose name is Verisign or Thawte or TeliaSonera, whom I know nothing about! No reason. But that's how security in Internet works.

This is the first part of a three part series addressing HTTPS and it's (in)security. Next part is about misappropriation of trust. Third part is about (failed) attempts to supervise trusted authorities.

This is a solution to my request #3 to Microsoft which I made in my post about Skype hack. Doing this will vastly improve your security for Skype-logins as the old Skype account and password cannot be used to login anymore.

Step 1: Merge Skype-account and Microsoft Account

For this sequence to work I have an existing Microsoft Account which is linked to my old Skype account. Also to state the obvious, I have different random password for every single service I ever use.

Go to https://account.microsoft.com/.

Login there with your Skype-account.
This is important! You need to use the old Skype-account for logging in.

Merge the accounts:

Yes! Single password login:

Testing:

The message clearly states "Your old Skype password doesn't work anymore". A login with Microsoft Account password does work.

Step 2: Limit allowed login accounts

Yet again, go to your Microsoft Account. See More security settings:

In there, you'll find Change sign-in preferences:

Now you see a list of possible logins to use:

Un-check / check the ones to suit your login needs. I went for a single one, of course.

That's it. Done!
Now your Skype login security is vastly improved.

This one won't fade away, so I'm taking a third swing at the subject. Previous posts are here and here. I've been actively following the conversation in Sype community's Security, Privacy, Trust and Safety board's discussion thread "Link to "baidu" website sent to all of my contacts".

Recap, what happened so far

Tons of fake links are being sent to people via Skype as chat messages. The chat is originating from somebody you already know and who is in your Skype's contact list.

Microsoft has stated "Some Skype customers have reported their accounts being used to send spam" when asked about it. That is true, people have been their Skype-accounts hacked by automated attacks based on leaked passwords and those accounts have been used to send crap to their contacts. However, this beef isn't about that. This beef is about the fact, that people whose Skype-accounts HAVE NOT been hacked, are sending crap to their contacts.

Microsoft went the classic way: "change your password". People did that. The same people are STILL sending crap to their contacts. For that, there is no official statement besides to (this is so ridiculous, I have to quote this verbatum) "Delete UNKNOWN Entry from HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run and Delete all UNKNOWN files under %appdata%\Roaming". Link to the exact instructions is here. So, I consider myself to be well educated about finer details what's inside Windows registry or Windows user profile. Because there are thousands of entries there, I don't know all of them, it is impossible to tell which of them are unknown and which are not. How would somebody with almost no experience be able to do that! Actually the magnitude of Microsoft support blunder is so huge, they wiped off the chat log from the discussion board and Box.com.

What people have also established, that there are two ways to login to a Skype session on any Skype-client. There is the old fashioned Skype-way and Microsoft Account. You can set a two-factor authentication into Microsoft Account, but not for Skype. Now that there are two ways to login, also please, remember that Skype can be run on multitude of mobile devices, Windows, Mac or directly from https://web.skype.com/. So, huge amount of attack surface exists there. What people have also established, that un-installing Skype from your device-of-choice doesn't make the problem go away, you'll still keep sending links to your contacts. So, reducing your personal attack-surface doesn't do it for you.

Obviously lots of people are royally pissed about this. Also Microsoft playing down their damage and offering completely useless support doesn't help.

The client devices are not compromized

When this kind of weird occurrence happens, any layman will immediately freak out and their mind there is with 100% certainity a single thought: my computer/phone has a virus!

In this case, no it does not.

People are "sending" these fake links after they un-installed Skype (two years ago). What exists, is the Skype-account. This is the hard part, which not-so-much-software-engineers don't grasp: your stuff in The Cloud can be cracked too, it doesn't have to be via your personal device. I don't know how to make this absolutely clear to a regular person.

The thing is: this issue is bothering many many people, and has been doing that since August 2016. All security flaw scenarios are possible, even cracked computers and mobile phones. However, that's not what interests me. My focus is on people whose computers have NOT been cracked, but are sending junk via Skype.

What's still happening

So, what's happened recenty is, that people are still receiving the links. Apparently (I haven't got any yet), the link has been changed from Baidu.com-based redirection to Vk.com, a Russian equivalent of Facebook. As I haven't received any of those, I cannot confirm the new link.

There are people, who have confirmed, that their Microsoft-account has been logged into from really weird geographic location. But that one can be easily fixed, change password and enable two factor auth they won't be doing that again. How the hack is actually done, we don't know. There was a theory about advertisement API, but personally I don't see that as a viable option. It would mean, that people actually would be using their Skype clients, but there are tons of people who haven't done that for couple years and are still spewing crap around.

Do something about it: Check that your account isn't cracked

There is no login-history, device list or anything that would resemble modern tools to audit your own account in the traditional Skype. This is what you can see:

What I'd like to see is what newly created Skype-accounts have and make the original Skype-account be gone. As in merge/delete/drop. I don't need two separate logins for my Skype. Especially as there is no 2-FA, or login device history for it.

This is what you can do is make sure your Microsoft Account is secure. Login to https://account.microsoft.com/.

So, nothing wrong with my account. Here is an account having more-than-dubious history entry in it:

I've redacted the IP-address from Belarus. It's most likely some poor bastard's machine, which is cracked and used as a springboard forward.

What I'd like to see happen

Firstly Microsoft, the owners of Skype need to step forward and confirm that accounts with proper passwords are being used to send crap. They need to admit, that their systems are not recognizing any accepted password logins, but chat messages are still being sent by innocent people.

Secondly, they need to fix the issue. Whichever is broken there they need to address it. The worst case scenario is, that somebody can actually inject new chat messages out of thin air, without the sender being logged in.

Third, the old skype account login needs to be secured. That's the easiest one here to achieve. As newly created Skype-accounts are only via Microsoft Account, that shouldn't be much problem. Also I'd like to get rid of that login method. Update: Instructions for doing this are in my next post.

So, Microsoft, we're waiting for you.

On Friday 11th November, I got yet another Baidu-link from one of the same contacts, I've already received some.

As I've been communicating with the persons who are "sending" me these links, they have changed their Skype-password for their old logins since this incident gained publicity. At this point, I'm ready to bet serious money on the fact, that this is not what Microsoft officals state, a case of re-using leaked passwords. This is a serious incident with protocol having a security flaw which is being exploited by somebody who loves pointing a finger to Baidu. As the link-jumping ends at a fake Forbes site with a fake article about a miracle pill allowing you to access 100% of your brain, I don't think Chinese have anything to do with this case. IMHO this points to Russia based on the fact, that this link rotator is located in a .ru-domain and is located in St. Petersburg, Russia.

This is how the fake Baidu-link redirects your request:

• Initial site sent via Skype: http://www.baidu.com/link
• Link rotator: http://acondi.ru/
• Taget sites:
  • http://dietzzfocon.com/ (USA)
  • http://exsuperbrain.com/ (UK)
  • http://weightuulossu.com/ (Netherlands)
  • http://zbiginbrain.com/ (Netherlands)
  • http://infocoolvip.com/ (Netherlands)
  • http://habzbrain.com/ (USA)
  • http://dietzzfocon.com/ (USA)

Microsoft:
Get your heads out of the sand! You have an issue to fix here.

For the past couple of days, I've been getting weird Baidu links via Skype chat. The sender is somebody I actually know and is my contact. The messages do not stay in the message history for that person, nor they never received the reply I sent back when the link was received. It's really weird to receive such links to a Chinese search engine in the first place, but the elusive chat history is the definite clue: somebody hacked Skype's protocol. Also, I find it strange, that the link contains my Skype-handle in it (obfuscated in below pic).

The message looks like this:

I'm not alone with this phenomenon: Link to "baidu" website sent to all of my contacts.

As the messages I got are from actual contacts, I followed up on them. Both persons deny sending me such links, and their message history doesn't display the link either. So, I don't think that the personal accounts are cracked, it's the Skype servers that are being exploited. Hopefully Microsoft-guys figure this out and plug the hole.

Update:

Couple hours after posting this, somebody posted a link to Why are Skype accounts getting hacked so easily? into Skype's community discussion. The article makes a claim that Skype's 2-factor authentication can be circumvented easily by using the old Skype credentials. Looks like you can still log in with Microsoft-account (pretty secure) or the credentials used before Microsoft acquired Skype. The old credentials cannot have 2-FA set up into it and most likely you already forgot it even exists. That seems to be the way how nasty people make their way in.

Update 10th Nov 2016:

Recent buzz is about a similar incident last year, when users' Skype accounts were used to send spam. So, nobody has come forward with any proof that the protocol would be compromised. It is gearing towards to the fact that users didn't realize there are two separate passwords to their Skype account, and the non Microsoft-account had a weak password which was used to gain access to contact lists.

Update 14th Nov 2016:
Confirmed, that this is not a case of using leaked passwords, my second post about this is here.

Arstechnica wrote last week: NSA could put undetectable “trapdoors” in millions of crypto keys. The article in the link says:

A special prime devised by the researchers, however, contains certain invisible properties that make the secret parameters unusually susceptible to discovery. The researchers were able to break one of these weakened 1,024-bit primes in slightly more than two months using an academic computing cluster of 2,000 to 3,000 CPUs.

So, there is a mathematical weakness in DH-key exchange algorithm when using 1024 bits and suitable prime number.

It so happens, that Diffie Hellman has been taking major hits in the past. In May 2015 team of researches found out an implementation failure in DH-key exchange called Logjam Attack. There is no mathematical weakness, but when negotiating a key exchange, client forces the number of bits used to be ridiculously low instead of server's suggestion. And in their discovery they suggested:

The Logjam researchers include some talk about how some "attackers with nation-state resources" could break through 1024-bit DH.

All this means, that the entire Diffie Hellman algoritm is riddled by different types of flaws and any reliability it previously enjoyed among security community is gone. Even with a Logjam-patched server, using less than 1024 has been insane for a long time. Now 1024 bits are gone, what next?

Impact

In practice this affects HTTPS, SSH and VPN-tunnels. Ok, there are other software using DH-key exchange, but I'll try to keep this simple.

So, there is no backdoor that NSA or anybody can open. It's just that when client and server agree on details of the encryption used in communication, the encryption key used can be calculated by a listening party. If somebody cannot capture your key exchange and encrypted bits, they cannot de-crypt the communication. However, if somebody can grab your bits and either you're using too weak DH-key exchange, or somebody can tamper the connection and do a "Logjam", then your connection's security will be impaired. The best option is to use some other protocol for key exchange.

There is more information about key exchange and Diffie Hellman in my previous article TLS Security recap - HTTPS (in)security up until 2016.

Diffie Hellman in TLS (SSL)

To quote the Wikipedia article about Diffie Hellman: "There are three versions of Diffie Hellman used in SSL/TLS: Anonymous Diffie Hellman, Fixed Diffie Hellman and Ephemeral Diffie Hellman". To make things confusing, there is also Elliptic curve Diffie–Hellman (ECDHE), which is not affected. For the purpose of this article, it is considered a completely another key exchange protocol. Yes, it has Diffie Hellman in the name, but ... still not affected.

Of those four protocols, pretty much the only ones being used in today's Internet are DHE (affected) and ECDHE (not affected). When looking at stats according to SSL Pulse, Survey of the SSL Implementation of the Most Popular Web Sites, only 27% of the sites tested supported DH/DHE with 1024 or less bits.

What you can do

The simple version is: nothing.

If you really want to, you can check which cipher suite your browser is using:

The string "TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384", means, that the TLS 1.2 connection is using elliptic-curves DHE (the not affected one) for key exchange. 

If you want to make things really interesting, from a Linux command prompt try to lure the server to use DHE as key exchange method. First get a list of suitable ciphers:

# openssl ciphers | perl -ne 'print join("\n", grep {/DHE-/} split(/:/));'

Let's pick one with weak key exchange, but with powerful crypto DHE-RSA-AES256-GCM-SHA384, and go for it:

# openssl s_client -cipher 'DHE-RSA-AES256-GCM-SHA384' -connect www.google.com:443

As guys at Google are smart, they won't allow that. What you have is "CONNECTED" and "alert handshake failure". It means, that your client and their server failed to agree on suitable cipher suite to use. Your request for using DHE was the key here.

Final words

If you are a server admin and didn't stop accepting Diffie Hellman as key exchange before this, do it now.

If you are a regular internet user, don't worry number of government-level organizations already have your data!

Every once in a while I have enough time to read books. The ones made out of paper having printed words and images on the paper. And pretty much 98% of the books I've read in the last couple of decades have something to do with my profession. There is one book, that's worth mentioning: Security Engineering by Ross Anderson.

The price point for getting this one is a non-issue, you can download the entire book as a PDF with no cost at http://www.cl.cam.ac.uk/~rja14/book.html (that's at University of Cambridge). Having the book available is fully intentional, as four years have passed, author and publisher have agreed to place the material freely available for anybody interested. I most sincerely thank Mr. Anderson of doing that.

Of yourse, I recommend you to support this good work and purchase one. Go to Amazon, or similar and get your own copy. It will include a digital copy, all you have to do is go to above link and download one.

I'd definitely recommend this book to anybody ever designing or implementing anything with a computer. As the phrase goes: “Smart people learn from their mistakes. But the real sharp ones learn from the mistakes of others.” This is your chance of getting ahead and learning how some smart people blundered in their design and/or implementation of security. There is so much information in the book, but I found the case studies being the best part. The general idea is to get an injection of experience and start to think like hackers do.

My recommendation is that, for anybody working in software engineering should memorize this book and have an exam taken, so that it is crystal clear how secure systems are done.