Those who care about their communications (individuals or enterprise), may at one point decide to look into encrypting email. Email is unfortunately a product of its past, designed for sending communications from one mailbox and delivering to another across the internet, yet during a time where encrypting that communication wasn’t even an afterthought. There have been some bolt on patches to secure email but really a nice new protocol is needed. Being stuck with what we have, you may have decided for one reason or another that S/MIME certificates are what you’d like to use to secure your email. Definitely a lot of people are concerned with the privacy of their email if you look at the section, “How important is it that your online information remain private?” in this article. I recently needed to ensure such certificates were also FIPS compliant. I had a hard time using the normal openssl binaries and ensuring I was using FIPS compliant commands to generate the certificates. So first we will compile an openssl binary in FIPS mode. This binary will error as soon as we run a command that is not FIPS compliant, ensuring our resultant certs are good. Then I’ll show how to generate the certs to be either self-signed by your own CA if you will use and trust among friends/family or to have signed by an Enterprise CA if you are a company with a trusted Enterprise CA and clients that trust it. Regardless, at the end you’ll have S/MIME certs you can use in your mail clients for secure communications.
h4. Building OpenSSL with FIPS Mode
I’m using Ubuntu 14.04.03 LTS, instructions may vary slightly on a different target system.
First download and extract the openssl source tarballs we will need (the below are the latest at time of this writing but always grab the latest stable releases)
tar xvzf openssl-fips-2.0.11.tar.gz
tar xvzf openssl-1.0.2e.tar.gz
You’ll probably need build-essential package which I had already installed so go ahead and `aptitude install build-essential`.
Next lets build the FIPS module our openssl will need:
Near the bottom of that output you should see something like installing to /usr/local/ssl/fips-2.0, we will need that directory in a bit to reference.
Now lets compile our own openssl, cd into the openssl-1.0.2e/ dir you extracted above
./config fips shared
What we did here was tell our compiled openssl that we have a shared fips module to use. The output of the above should tell you “OpenSSL shared libraries have been installed in:
So what you’ve done is you have your normal system openssl completely intact but now in /usr/local/ssl you have the one compiled with FIPS support.
You can check the version
openssl version will come from your system and output something like `OpenSSL 1.0.1f 6 Jan 2014`
whereas if you cd /usr/local/ssl/bin and run ./openssl version you’ll see our fips one `OpenSSL 1.0.2e-fips 3 Dec 2015`.
Great now lets export a couple variables so that our compiled openssl can get to the shared fips module:
export LD_LIBRARY_PATH=/usr/local/ssl/fips-2.0 && export OPENSSL_FIPS=1
One final test to prove this openssl will error on anything that is not FIPS compliant is we can try to get an MD5 hash of a file.
./openssl md5 /home/user/somefile
and you’ll get some error output like:
Error setting digest md5
140006545020576:error:060A80A3:digital envelope routines:FIPS_DIGESTINIT:disabled for fips:fips_md.c:180:
since md5 hash is not FIPS compliant.
h4. Creating the FIPS S/MIME Certs
Now that we have an openssl that will only allow us to run things that are FIPS compliant we can generate some S/MIME certs.
I’m going to number the steps to take here to create your certs with a comment after each numbered step describing what the step is doing. Where you see multiple of the same number, that means you chose the step you want based on your desired outcome (what options you want, what CA will be used, etc.).
1. ./openssl genrsa -out newkey.key 4096 – where newkey.key is the key and can be named anything you want, we are just generating a 4096 bit key.
2. ./openssl pkcs8 -v1 PBE-SHA1-3DES -topk8 -in newkey.key -out enc_newkey.key – this takes our normal key above and encodes it in pkcs8 format. This is a common format used but you have options, like my next command uses v2 which isn’t as widely accepted and there is also pkcs12. If you think you need to use some variant of a command I specify here you can get more information with running ./openssl pkcs12 /? and it’ll output your options.
2. ./openssl pkcs8 -v2 des3 -topk8 -in newkey.key -out enc_newkey.key Here is another variant of the above command if you wanted to use version2 of pkcs8, again chose one of these commands to run.
*With any of the step 2 commands, you will be asked for a password, please enter something from 4 to 1023 characters long and then provide it when asked in step 3 below.
3. ./openssl req -new -key enc_newkey.key -out new_request.csr – Now we take our new pkcs8 encoded key and generate a CSR (Certificate Signing Request) with it.
(see CSR Creation Info below for examples of fields)
Depending on how you want to have your certificate signed, use ONE of the Step 4’s below:
4. ./openssl x509 -req -days 3650 -in new_request.csr -signkey enc_newkey.key -out email.crt – This is the self-signed option
4. ./openssl x509 -req -days 3650 -in new_request.csr -signkey enc_newkey.key -CA enterprise_ca.cer -CAkey enterpriseprivatekeynopass.pem -set_serial 13 -out email.crt – This shows using a CA you have the cert and key for.
Using a Microsoft Enterprise CA Web UI:
Click on Request a Certificate Link
Click on the advanced certificate request link
Paste contents of CSR into top box (DO NOT include the Beginning and Ending lines!!!)
Download the Base 64 Encoded Certificate and Chain, name them yournameB64.cer and yournameB64.p7b
If you used the Web UI then this is your Step 5:
5. openssl pkcs12 -export -out yourname.pfx -inkey yournamekey.p7b -in yournameB64.cer -certfile enterprise_ca.cer
5. ./openssl pkcs12 -export -descert -in email.crt -inkey enc_email.key -out email.pfx
This is exporting your new cert and key into a pfx file that is generally used to import into mail clients to support S/MIME.
h5. CSR Creation Info
You are about to be asked to enter information that will be incorporated
into your certificate request.
What you are about to enter is what is called a Distinguished Name or a DN.
There are quite a few fields but you can leave some blank
For some fields there will be a default value,
If you enter ‘.’, the field will be left blank.
Country Name (2 letter code) [AU]:US
State or Province Name (full name) [Some-State]:South Dakota
Locality Name (eg, city) :Sioux Falls
Organization Name (eg, company) [Internet Widgits Pty Ltd]:Company Inc
Organizational Unit Name (eg, section) :Development
Common Name (e.g. server FQDN or YOUR name) :John Doe
Email Address :email@example.com
Please enter the following ‘extra’ attributes
to be sent with your certificate request
A challenge password :
An optional company name :