Category Archives: Internet

Cryptography, Internet, Security, Software, Tutorials and guides

How to ask for a certificate the right way: CSR via Windows or Keytool with Subject Alternative Names (SANs)

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Sooo you’re working in an enterprise and have to maintain an internal server. The security audit asks you to ensure all HTTP communications are encrypted, so you need to change to HTTPS. Boy is this SO not obvious. You’d think this should be quite easy by now, but there are A LOT of pitfalls in your way.

If you want the TL;DR version, to skip the explanation and go directly to the instructions, scroll directly to the Mandalorian below. No hard feelings, honest šŸ˜Š

Mistake #1: Use a self-signed certificate

Many, many, MANY tutorials you’ll find online are written with a developer in mind, leaving the maintainer/admin as an afterthought -if that. So what they care about is having some certificate, any certificate, as long as it works on the developer’s PC.

But what this certificate says is basically “I’m Jim because I say so”.

Do I need to say that it won’t work for other PCs? Yes? Well surprise, it won’t.

Mistake #2: Get a certificate from your PC’s certificate authority

I don’t know how some people don’t understand that this, while being a bit more complex, it’s basically the same as #1. What this certificate says is “I’m Jim because someone else who is also Jim says so”.

Yeah, no, it won’t work.

Mistake #3: Get a certificate from a trusted certificate authority using only a server name (or an alias).

Now we’re getting more serious.

Getting a certificate from a trusted certificate authority (CA for short) is the right thing to do. The certificate you get then says “I’m Jim because someone else who you already trust says so”.

So if you get a certificate that verifies you’re, say, server web-ch-zh.xyz123.com or mysite.xyz123.com is good enough. Right?

Ummm…

IT DEPENDS.

If you run a website (e.g. https://www.xyz123.com) and want your HTTPS URL to work without giving a certificate warning that’s fine. You don’t need to do anything else. That’s why most tutorials that avoid the self-signed certificate mine stop here.

But remember, our scenario is that we’re working for an enterprise (a big company) and we’re maintaining an internal server. What that usually -not always, but a lot of the time- means is that communication to our server happens using different hostnames.

Let me give you my own example:

  • I run a service called Joint Information Module or JIM for short -that’s a totally real service name [1].
  • The server name is ch-zh-jim-01.mycompany.local.
  • The users use the web interface of the service by navigating to https://jim.mycompany.com.
  • Another application uses the REST API of the service using the server name (ch-zh-jim-01) without the domain name (mycompany.local).
  • The service uses a queuing software that is installed on the same server. We want to use the same certificate for this as well. The JIM service accesses the queues via https://localhost (and a port number).

Now, if the certificate you got says “ch-zh-jim-01.mycompany.local ” and you try to access the server via https://ch-zh-jim-01, https://jim.mycompany.com, https://localhost or https://127.0.0.1, you’ll get a certificate error much like the following:

certificate error chrome

Also, the REST API won’t work. The caller will throw an exception, e.g. java.security.cert.CertPathValidatorException in Java or System.Security.Authentication.AuthenticationException in DotNet. You can avoid this by forcing your code to not care about invalid certificates but this is a) lazy b) bad c) reaaaaaaaaaaly bad, seriously man, don’t do this unless the API you’re connecting to is completely out of your control (e.g. it belongs to a government).

The correct way

So you need a certificate that is trusted and valid for all the names that will be used to communicate with your server. How do you do that? SIMPLEZ!

  1. Generate a CSR (a certificate signing request, which is a small file you send to the CA) with the alternative names (SANs) you need. That’s what I’ll cover here.
  2. Send it to a trusted CA
    1. either the one your own company operates or
    2. a commercial one (which you have to pay), say Digicert.
  3. Get the signed certificate and install it on your software.

Important note: the CA you send the CSR to must support SANs. Not every CA supports this, for their own reasons. Make sure you read their FAQ or ask their helpdesk. Let’s Encrypt, a free and very popular CA, supports them.

Here I’ll show how you can generate a CSR, both in the “Microsoft World” (i.e. on a Windows machine) and in the “Java World” (i.e. on any machine that has Java installed).

A. Using Windows

Note that this is the GUI way to do this. There’s also a command line tool for this, certreq. I won’t cover it here as this post is already quite long, but you can read a nice guide here and Microsoft’s reference here. One thing to note though is that it’s a bit cumbersome to include SANs with this method.

  1. Open C:\windows\System32\certlm.msc (“Local Computer Certificates”).
  2. Expand “Personal” and right click on “Certificates”. Select “All tasks” > “Advanced Operations” > “Create Custom Request”.
  3. In the “Before you begin” page, click Next.
  4. In the “Select Certificate Enrollment Policy” page, click “Proceed without enrollment policy” and then Next.
  5. In the “Custom Request” page, leave the defaults (CNG key / PKCS #10) and click Next.
  6. In the “Certificate Information” page, click on Details, then on Properties.
  7. In the “General” tab:
    1. In the “Friendly Name” field write a short name for your certificate (that has nothing to do with the server). E.g. cert-jim-05-2021.
    2. In the “Description” field, write a description, duh šŸ˜Š
  8. In the “Subject” tab:
    1. Under “Subject Name” make sure the “Type” is set to “Full DN” and in the Value field paste the following (without the quotes): “CN=ch-zh-jim-01.mycompany.local, OU=IT, O=mycompany, L=Zurich, ST=ZH, C=CH” and click “Add”. Here:
      • Instead of “ch-zh-jim-01.mycompany.local” enter your full server name, complete with domain name. You can get it by typing ipconfig /all in a command prompt (combine Host Name and Primary Dns Suffix).
      • Instead of “IT” and “mycompany” enter your department and company name respectively.
      • Instead of “Zurich”, “ZH” and “CH” enter the city, state (or Kanton or Bundesland or region or whatever) and country respectively.
    2. Under “Alternative Name”:
      1. Change the type to “IP Address (v4)” and in the Value field type “127.0.0.1”. Click “Add”.
      2. Change the type to “DNS” and in the Value field type the following, clicking “Add” every time:
        • localhost
        • ch-zh-jim-01 (i.e. the server name without the default domain)
        • jim.mycompany.com (i.e. the alias that will be normally used)
        • (add as many names as needed)

Important note: all names you enter there must be resolvable (i.e. there’s a DNS entry for the name) by the CA that will generate your certificate. Otherwise there’s no way they can confirm you’re telling the truth and the request will most likely be rejected.

It should end up looking like this:

  1. In the “Extensions” tab, expand “Extended Key Usage (application policies)”. Select “Server Authentication” and “Client Authentication” and click “Add”.
  2. In the “Private Key” tab, expand “Key Options”.
    1. Set the “Key Size” to 2048 (recommended) or higher.
    2. Check the “Mark private key exportable” check box.
    3. (optional, but HIGHLY recommended) Check the “Strong private key protection” check box. This will make the process ask for a certificate password. Avoid only if your software doesn’t support this (although if it does, you really should question if you should be using it!).

At the end, click OK, then Next. Provide a password (make sure you keep it somewhere safe NOT ON A TEXT FILE ON YOUR DESKTOP, YOU KNOW THAT RIGHT???) and save the CSR file. That’s what you have to send to your CA, according to their instuctions.

B. Using Java

Here the process is sooo much simpler:

  1. Open a command prompt (I’m assuming your Java/bin is in the system path; if not, cd to the bin directory of your Java installation). You should have enough permissions to write to your Java security dir; in Windows, that means that you need an administrative command prompt.
  2. Create the certificate. Type the following, in one line, but given here splitted for clarity. Replace as explained below.
keytool
-genkey
-noprompt
-cacerts
-alias cert-jim-05-2021 
-dname "CN=ch-zh-jim-01.mycompany.local, OU=IT, O=mycompany, L=Zurich, ST=ZH, C=CH" 
-keyalg RSA
-keysize 2048
-storepass changeit
-keypass MYSUPERSECRETPASSWORD
  1. Create the certificate signing request (CSR). Type the following, in one line, but given here splitted for clarity. Replace as explained below.
keytool 
-certreq 
-file c:\temp\cert-jim-05-2021.csr 
-cacerts 
-alias cert-jim-05-2021 
-dname "CN=ch-zh-jim-01.mycompany.local, OU=IT, O=mycompany, L=Zurich, ST=ZH, C=CH" 
-ext "SAN=IP:127.0.0.1,DNS:localhost,DNS:ch-zh-jim-01,DNS:jim.mycompany.com" 
-ext "EKU=serverAuth,clientAuth"
-storepass changeit 
-keypass MYSUPERSECRETPASSWORD

In the steps above, you need to replace:

  • “cert-jim-05-2021”, both in the filename and the alias, with your certificate name (which is the short name for your certificate; this has nothing to do with the server itself).
  • “ch-zh-jim-01.mycompany.local” with the full DNS name of your server.
  • “IT” and “mycompany” with your department and company name respectively.
  • “Zurich”, “ZH” and “CH” with your city, state (or Kanton or Bundesland or region or whatever) and country respectively.
  • “ch-zh-jim-01” with your server name (without the domain name).
  • “jim.mycompany.com” with the DNS alias you’re using. You can add as many as needed, e.g. “DNS:jim.mycompany.com,DNS:jim-server.mycompany.com,DNS:jim.mycompany.gr,DNS:jim.mycompany.ch”

Important note: all names you enter there must be resolvable (i.e. there’s a DNS entry for the name) by the CA that will generate your certificate. Otherwise there’s no way they can confirm you’re telling the truth and the request will most likely be rejected.

  • “changeit” is the default password of the Java certificate store (JAVA_HOME/jre/lib/security/cacerts). It should be replaced by the actual password of the certificate store you’re using. But 99.999% of all java installations never get this changed šŸ˜Š so if you don’t know otherwise, leave it as it is.
  • “MYSUPERSECRETPASSWORD” is a password for the certificate. Make sure you keep it somewhere safe NOT ON A TEXT FILE ON YOUR DESKTOP, YOU KNOW THAT RIGHT???

That’s it. The CSR is saved in the path you specified (in the “-file” option). That’s what you have to send to your CA, according to their instuctions.

Enjoy!

[1] no it’s not, c’mon

health, Internet, Software

I’m a donor for Folding@Home (and you can be as well)

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I’m not a fan of IT hubris. I cringe -literally- when I hear stuff like “let’s fight cancer (or whatever) with scrum”. You don’t fight diseases with IT; at best, you can help.

But help can be important. One problem that IT is very well suited to solve is understanding how viruses and bacteria behave under certain circumstances. The Folding@Home project explains:

WHAT IS PROTEIN FOLDING AND HOW IS IT RELATED TO DISEASE?
Proteins are necklaces of amino acids, long chain molecules. They are the basis of how biology gets things done. As enzymes, they are the driving force behind all of the biochemical reactions that make biology work. As structural elements, they are the main constituent of our bones, muscles, hair, skin and blood vessels. As antibodies, they recognize invading elements and allow the immune system to get rid of the unwanted invaders. For these reasons, scientists have sequenced the human genome ā€“ the blueprint for all of the proteins in biology ā€“ but how can we understand what these proteins do and how they work?

However, only knowing this sequence tells us little about what the protein does and how it does it. In order to carry out their function (e.g. as enzymes or antibodies), they must take on a particular shape, also known as a ā€œfold.ā€ Thus, proteins are truly amazing machines: before they do their work, they assemble themselves! This self-assembly is called ā€œfolding.ā€

WHAT HAPPENS IF PROTEINS DONā€™T FOLD CORRECTLY?
Diseases such as Alzheimerā€™s disease, Huntingtonā€™s disease, cystic fibrosis, BSE (Mad Cow disease), an inherited form of emphysema, and even many cancers are believed to result from protein misfolding. When proteins misfold, they can clump together (ā€œaggregateā€). These clumps can often gather in the brain, where they are believed to cause the symptoms of Mad Cow or Alzheimerā€™s disease.

The project has made it very easy for anyone to help. You just download and install their software, and your computer starts calculating, solving math problems -essentially, you’re giving your computer’s processing power when you don’t use it. You can see your -and other’s- contribution in the project stats.

I heartily encourage you to do so.

folding at home stats
That’s my HP i7, sitting in the attic and doing what little it can to help beat COVID19.
Internet, Security

How I fought off a Facebook hacker -and how to avoid getting hacked yourself

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Last night I helped a close friend: I successfully fought off a Facebook account takeover. It wasn’t easy. I sweated for a couple of hours until I got it done. And I even had to face a rather unsophisticated, or maybe just lazy, enemy. Here I’ll recap what happened and give some easy but effective advice that you can easily use .

What happened?

As it happens with many IT professionals, I’m the go-to person for any computer related problems for family and friends.

My friend called me, frantically trying to explain that someone, using his Facebook account, was using Messenger to send personal messages to all his contacts. The message was in casual language, like you would talk to a friend, claiming that he had lost his wallet and asking if the friend has an account in a certain bank (obviously the bank had nothing to do with this). Most importantly, the message didn’t look obviously fake.

“Good evening.. how are you?!! I’m here and there. I lost my wallet šŸ˜¦ Can I ask you something.. do you maybe have an account in Piraeus Bank? I need a big favor, I lost the bank card as well :(“

The response

Mitigation: informing people

To avoid people actually sending money, I logged into Messenger with my friend’s credentials and started sending messages to people that were replying, concerned about what had might have happened to their friend. I opted for something short, clear and alarming: “I’VE BEEN HACKED PLEASE IGNORE IT’S A VIRUS” (yes, I know that technically speaking that’s not especially accurate)

But the enemy was active and chatting with 2-3 of the contacts. In these cases, I saw my message being deleted.

I noticed that all his messages were more or less the same; he had some kind of playbook and was copy-pasting text, maybe slightly changing the text to fit the conversation.

And in one case he came close to being victorious: before I could sent the “please ignore” message, one of the contacts sent him some bank details -not sure what exactly as the message was deleted by the enemy, presumably after copying it. The contact then saw my message and replied alarmed “I sent him, what do I do now???” to which I replied “Call your bank NOW and lock your account and credit card”. I hope that helped; I’ll definitely follow up on that.

Taking back control of the account

The enemy hadn’t changed any password, so I was able to log in. Remember that Messenger accounts are controlled in Facebook (unless you have a Messenger-only account, which was not the case here). So the first thing I checked was the active sessions in Facebook (Settings > Security and Login Settings > Where You’re Logged In). That was what I got:

Unfortunately I didn’t know at the time that you can hover over the session with the mouse and get more info, like the session’s IP address. Had I done that, we could have a chance to retaliate -like going to the police.

My friend uses an Ubuntu laptop (which I set up for him), a Windows PC at work and a Samsung mobile where he uses Facebook and Messenger through the apps. So the first 3 sessions were almost certainly the enemy. I immediately disconnected him. Then I changed the password.

But we were not out of the woods yet.

The Empire Strikes Back

After changing the password and believing that I had locked him out for good, I continuing notifying people in Messenger. But after a few minutes, I suddenly saw a fresh batch of the same message being sent. My friend has around 500 contacts (“friends”) and I suppose there’s some limitation from Messenger so the enemy wasn’t able to send his message to everyone at once.

How was this possible? I had changed the password and disconnected his sessions. I glanced at Facebook Settings (“Where You’re Logged In”) and, sure enough, new sessions of the Huawei Mate 8 were there. He couldn’t have guessed the new 18-character completely random password I had set. I tried logging into Facebook from a private browser window and I got “Wrong password”. Hmmm… the options I had from Facebook for changing a forgotten password was 1) SMS 2) email 3) recognize people in pictures. Until that point, I had used SMS. So how did he do that?

I called my friend:

Me: please tell me that you don’t have the same password in your email as in Facebook
(note: his password was something like “oldman53#”)
Friend: no I don’t
Me: so what’s your email password?
Friend: The same but without the # at the end

NICE. Well that’s really damn secure I thought to myself, though I didn’t say anything -didn’t want to castigate my beleaguered friend, I’m saving that for the weekend šŸ™‚

So first thing, as people were already replying in Messenger and there was real danger of someone sending money, I had to stop him getting in. So I went to Facebook settings to change the email.

The thing is, with the password already changed and unknown to me, I had to reset the password first. And Facebook wouldn’t send an SMS anymore, after having used it a few times already.

Return of the Jedi

So I had to resort to face recognition. The process presented me with 3 photos at a time, for a total of 5 people, and a list of possible names from the friends list. There was the option “I don’t know”, but you could use it only twice -then you were out.

Obviously these people were unknown to me, so I had to send them through What’s App to my friend. It took us around 10 precious minutes but at the end it worked. I immediately changed the email to one that I own (and has a decent, unique password and multi-factor authentication!).

After that, I disconnected his sessions and that was the end of it, I didn’t see him again. I quickly headed over to outlook.com, where his email is hosted, changed the password there and added two factor authentication by SMS.

I anxiously kept monitoring Facebook’s sessions in case he somehow came back on one window and at the same time continued to notify the hundreds of people he had sent his message to. At the same time I tested, with a private browser window, that I even knowing the password I couldn’t login to Facebook or outlook.com without an SMS to my friend’s phone.

After around half an hour had passed, I felt the worst were behind us. I called my friend and told him to log in to Messenger and continue talking to people.

Some conclusions

To be clear, the reason this happened was because my friend, like many, many people, had bad password hygiene. He was using relatively easy (for a machine) to guess passwords but most importantly, he was reusing passwords between web sites. And web sites get passwords stolen. A lot.

What can you do to avoid this happening to you? Start from the low-hanging fruit. You get very decent security with very little effort.

So here’s a small TODO list:

UPDATE: I wrote a blog post explaining how to install and use a password manager. You can read it here.

  • Use random long (18 character or more) passwords. If it’s really random (e.g zGasd6t7a6tgQaERys6Ld5AoVF567) you don’t even need symbols. Don’t create them by hand, use a password generator (like this).
  • Use unique passwords. Every site or service you use needs to have its own. It will get stolen, eventually, but the damage will be contained to this site only. And no, oldman53 and oldman53# are NOT really different.
  • The two points above are basically impossible for a human to do. So you need to use a password manager. I use LastPass and I’m very happy with it. It costs around EUR 35 a year. If you want a free alternative use either Bitwarden or Firefox Lockwise. UPDATE: I’ve moved to Bitwarden Premium (just $10/year) and I’ve never been happier. I also recommend Bitwarden Free (+ Authy for 2FA) for my friends that don’t want to pay a cent.
  • When available, use two-factor authentication (2FA); you might also see it named as multi-factor authentication (MFA) or two-step validation (2SV, that’s what Amazon calls it). This is an absolute must. 2FA is when, in order to login to a service, you need a username, a password plus something more. Usually it’s an SMS, and that’s fine, but even better you can use an authenticator app. LastPass has its own, and its backed up in your LastPass account, but if you want a free alternative get either Authy or the one from Microsoft which is backed up in your Microsoft account. Obviously your authenticator backup needs to be well protected, so use two-factor for this as well -but a different one in case you lose access to it, so here SMS is better. UPDATE: Bitwarden Premium (not Free) can store 2FA in the same record where you store the site’s username & password. What’s really really really convenient with this is that, as soon as it fills in the password, it auto-copies the 2FA token to the clipboard, saving you the hassle. It doesn’t sound much but if you login to many different sites every day (as I do), you’ll love it.
How much effort is this?

I did this with my friend so I got a taste. Note that I’m in Switzerland and he’s in Greece, so he did the whole process with me giving instructions on the phone -which slowed us down considerably. But on the other hand I knew what had to be done, while less experienced users might be not so comfortable when doing this for the first time. We used Bitwarden + Authy.

  • It took us around 90 min to set up Bitwarden and Authy, and then add all his passwords there. We set it up on his laptop and two mobile phones.
  • It took another hour to change the password for the most important services (Gmail, Outlook.com, Paypal and Facebook) and to set up two-factor authentication.
  • Add to that another 45 minutes of training, for him to learn to use a password generator, the password manager and 2FA. Basically how to use really long and random passwords when signing up to web sites, how to save the passwords in Bitwarden, how to log in from the laptop or phone without having to type the password and how to add 2FA (where available) in Authy.

So that was, what, almost three and a half hours in total. It’s not trivial. But trust me, if you find yourself in his shoes you’ll wish you had done it already. It’s time well spent šŸ™‚

Internet, Logic, Post-truth

I’m a translator for Skeptical Science

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Short version: I’m honoured to be accepted as a volunteer translator for the Debunking Handbook and skepticalscience.com.

Hoaxes, myths, fake news. Unless you’ve been living under a rock (which is mildly unlikely given you’re reading a blog right now) you’ve encountered at least one, probably many. Is fluoridated water a plan to impose a communist government in the US? (no). Do airplanes spray us with chemicals to make us obedient? (no). Are the members of the UK Royal Family lizards? (no). Do vaccines cause autism? (hell no).

THEY are watching YOU (?)

Over the years, the issue has gotten me both fascinated and to the brink of despair. I’m genuinely fascinated in the way people think –or, as is unfortunately often the case, don’t. And I frequently despair when witnessing how easy it is for people, even ones that I think very highly of, to fall victims to the stupidest of conspiracy theories.

Hard as I try, I’m not immune to this myself –why would I? As a recent example, when reading that “people who curse are smarter” (yes I’m painfully aware of the irony) I immediately fell for it. It was only later that I found out that this is an existing but brutally misrepresented piece of research [link, in Greek].

Many times, when discussing with friends or family, I’ve heard yet another hoax, myth or conspiracy theory. I have then tried, and completely failed, to make my friend or relative aware of the misinformation or fallacy; and not for a lack of well-founded arguments. So I started looking for a way to effectively communicate science and, ultimately, truth.

That’s how I found the Debunking Handbook and skepticalscience.com. Upon reading it, in English, I immediately knew that that’s what I was looking for. The decision to help this effort by translating the handbook in Greek was almost a no-brainer.

Internet, Software, Tutorials and guides

Citrix on Ubuntu 18.04

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I recently changed from Win10 to Ubuntu 18.04 as my main OS at home. I still have Windows in a few VMs, as I need to do the occasional development with Visual Studio.

But a problem I had was that needed to connect to the office when doing home office.

Now, at work we have Citrix Netscaler Gateway. And there’s a Linux client available. It worked, but not as smoothly as I hoped šŸ™‚

Here’s what I did:

From Ubuntu’s Software Center, I installed Citrix Receiver.

Then it asked for the server and tried to connect, but I was getting an error: “An SSL connection to the server could not be established because the server’s certificate could not be trusted.”

So I opened a terminal and gave the following commands (source):

sudo ln -s /usr/share/ca-certificates/mozilla/* /opt/Citrix/ICAClient/keystore/cacerts/

sudo c_rehash /opt/Citrix/ICAClient/keystore/cacerts/

After that it connected, but it was still giving an error: “A protocol error occured while communicating with the Authentication Service”

So after some sleuthing, I opened my browser (Chrome) and connected to the my company’s Citrix server address (https://server). When I clicked the apps there, it worked.

Internet, Politics, Post-truth

Post-truth, clearly illustrated

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That’s a piece of news, tweeted by a random guy, that went viral. It’s false, but it didn’t matter at all.

Note that this is NOT a typical fake news case. The “guilty” guy -the one who tweeted the wrong info- actually did some effort to verify if his claim was true. Not that much; but this is totally understandable given that he had, like, 40 followers (basically his friends). And when his tweet went viral and was shared 100s of 1000s of times, he tried to find the truth. When he did, he admitted it, deleted the original tweet and posted the fact that it was false.

It didn’t matter.

These are not the buses you’re looking for

It immediately became, and still is, “proof” for a lot of people, asserting a fact that never happened.

I’m becoming increasingly desperate. There really doesn’t look any way out of this mess. People will believe anything if they want to believe it. And through the internet, it’s all too easy to find it. True or not; it doesn’t matter.