XML Prague 2018

XML Prague
Image  XML Prague ©

This week I am attending XML Prague at the University of Economics College campus in Prague, a conference on markup languages and data on the web. Together with other XSpec developers I am organising the XSpec Users Meetup. I’m also giving a lightning talk in the Schematron Users Meetup on how to test Schematron with XSpec.

Slides of the XSpec Users Meetup are available here whereas my lightning talk on testing Schematron with XSpec is available here.

How to exclude a package from being updated on Linux

Image by Marc Falardeau – CC BY 2.0

Sometimes you prefer not to update a specific package in Linux. This may be because you don’t want to upgrade to a new version with new features but no security updates. Or maybe because upgrading requires a service restart that you want to avoid just yet. This was the case for me recently when a new version of Docker came up and upgrading would have restarted the docker daemon and stopped the running containers.

It is possible to exclude a package from being updated. On Linux RPM systems (RedHat, CentOS, Fedora, etc.) this is the command to install all updates but exclude a specific package (say docker):

On Debian-like systems (Debian, Ubuntu, Mint, etc.) it is slightly more convoluted because you need to hold a package first and then upgrade the system

and remember to remove the hold when you’re ready to upgrade that package too





AWS Lambda and Jenkins Integration

AWS Lambda and Jenkins
Logos by Amazon Web Services © and Jenkins ©

Serverless is gaining attention as the next big thing in the DevOps space after containers. Developers are excited because they don’t have to worry about servers any more; Ops may be sceptical and slightly worried to hear about a world without servers (and sys admin maintaining them). Can these two worlds co-exist? Can serverless just be another tool in the DevOps toolkit?

I recently implemented a real use case at work where we took advantage of an event-driven workflow to trigger Jenkins jobs originally created to be executed manually or on a schedule. The workflow is as follows:

1. New data is uploaded to an S3 bucket
2. The S3 event calls a lambda function that triggers a Jenkins job via the Jenkins API
3. The Jenkins job validates the data according to various criteria
4. If the job passes, the data is upload on an S3 bucket and a successful message is sent to a Slack channel
5. If the job fails, a message with a link to the failed job is sent to a Slack channel

Workflow S3 Lambda Jenkins Slack-workflow

Jenkins User

Let’s start by creating a new user with the correct permissions in Jenkins. This allows to restrict what the lambda function can do in Jenkins.

In Manage Jenkins -> Manage Users -> Create User I create a user called lambda:

Create Jenkins User

In Manage Jenkins -> Configure Global Security -> Authorization -> Matrix-based Security  add the user lambda  to User/group to add and set the permissions as in the matrix below:

Set Jenkins User PermissionsThis is a minimum set up and allows the lambda user to build jobs. According to your security policies, you may want to further restrict the permissions of the lambda user in order to run only some specific jobs (you may need role based authentication for setting this up).


Now let’s move to AWS and set up a IAM Role for the lambda function. Head to IAM -> Roles and create a new roles with the following policies (my role name is digiteum-file-transfer , sensitive information is obfuscated for security reasons):

AWS IAM RoleThis role allows to execute lambda functions, access S3 buckets as well as the Virtual Private Cloud (VPC).

S3 Configuration

I create an empty S3 bucket using the wizard configuration in S3 and name it gadictionaries-leap-dev-digiteum. This is the bucket that is going to trigger the lambda function.

AWS Lambda Configuration

Finally, let’s write the lambda function. Go to Lambda -> Functions -> Create a Lambda Function. Select Python 2.7 (read Limitations to see why I’m not using Python 3) as runtime environment and select a blank function.

In Configure Trigger, set up the trigger from S3 to Lambda, select the S3 bucket you created above (my S3 bucket is named gadictionaries-leap-dev-digiteum ), select the event type to occur in S3 (my trigger is set to respond to any new file drop in the bucket) and optionally select prefixes or suffixes for directories and file names (I only want the trigger to occur on XML files). Here is my trigger configuration:

AWS Lambda Configure TriggerIn Configure Function, choose a name for your function (mine is file_transfer ) and check out the following Python code before uploading it:

Note the following:

  • Line 6 imports the python-jenkins module. This module is not in Python’s standard library and needs to be provided within the zip file (more on this in a minute).
  • Line 12 sets up the URL of the EC2 instance where Jenkins is deployed. Note that you need to use the private IP address as shown in EC2, it won’t work if you use the public IP address or the Elastic IP address.
  • Lines 15 and 16 set up the credentials of the Jenkins user lambda. The credentials will be exposed to the lambda function as environment variables and, unlike in this example,  it is recommended to encrypt them.
  • Lines 18-31 contain the handler function that is triggered automatically by a new file upload in the S3 bucket. The handler function does the following:
    • retrieve the filename of the new file uploaded on S3 (lines 21-22) 
    • log into Jenkins via username and password for the lambda user (line 25)
    • build the job called Digiteum_File_Transfer  in the folder Pipeline  (line 26)
    • throw an error if it can’t connect to Jenkins or start the job (lines 28-31)

As an example, here is the zip file to upload in Configure Function. It contains the lambda function and all the Python modules needed, including the python-jenkins module. Make sure you edit the private IP address of your Jenkins instance in line 12. If you need to install additional Python modules, you can follow these instructions.

Here is how my Configure Function looks like:

Lambda Configure FunctionNote the name (it should read file_transfer  instead of file_transfe ), the handler (as in the Python code above), and the role (as created in IAM). Note also that the username and the password of the Jenkins user lambda are provided as environment variables (ideally, you should encrypt these values by using the option Enable encryption helpers).

Once you’ve done the basic configuration, click on Advanced Settings. In here you need to select the VPC, subnet, and security group of the EC2 instance where Jenkins is running (all these details about the instance are in EC2 -> Instances). In fact, the lambda function needs to run in the same VPC as Jenkins otherwise it cannot connect to Jenkins. For example, here is how my advanced settings look like (sensitive information is obfuscated):

Lambda Configure Function Advanced SettingsFinally, review your settings and click on Create Function.

Test the Lambda Function

Once you created a lambda function, configure a test event to make sure the lambda function behaves as intended. Go to Actions -> Configure test event and select S3 Put to simulate a data upload in the S3 bucket. You need to replace the bucket name (in this example gadictionaries-leap-dev-digiteum) and the name of an object in that bucket (in this example I uploaded a file in the bucket and called it test.xml). Here is a test example to adapt:

Click on Save and Test and you should see the lambda function in action. Go to Jenkins and check that the job has been executed by user lambda . If it doesn’t work, have a look at the logging in AWS Lambda to debug what went wrong.

Slack Configuration

Finally, I set up a Slack integration in Jenkins so that every time the Jenkins job is executed, a notification is sent to a Slack channel. This also allows several people to get notified about a new data delivery.

First, install and configure the Slack plugin in Jenkins following the instructions on the GitHub page. The main configuration is done in Manage Jenkins -> Configure System -> Global Slack Notifier Settings. For example, this is my configuration:

Jenkins Slack Notifier SettingsNote that:

  • Team Subdomain is the name of your Slack account
  • Channel is the name of your default slack channel (you can override this in every job)
  • Integration Token Credential ID is created by clicking Add and creating a token in Jenkins’ credentials. As the message says, it is recommended to use a token for security reasons. Here is an example of a Token Credential ID for Slack in Jenkins:

Jenkins Slack Integration Token

You typically want to add a notification to a specific Slack channel in your Jenkins job as a post-build action in order to notify the result of a job. In Jenkins go to your job’s configuration, add Post-build Actions -> Slack Notifications and use settings similar to these:

Jenkins Post-build ActionsThis sends a notification to the Slack channel (either the default one set in Global Slack Notifier Settings or a new one set here in Project Channel)  every time a job passes or fails. When a notification is sent to Slack, I will look like this:

Slack NotificationsNow you can keep both technical and non-technical users informed without having to create specific accounts on Jenkins or AWS or spamming users with emails.


I ran into two problems that I was not yet been able to solve due to lack of time. I want to flag them as they can improve the lambda function and make it more maintainable. If anyone want to help me to fix this, please send me your comments.

  • Encryption: I tried to encrypt the Jenkins password  but I could not make the lambda function decrypt the password. I set up an encryption key in IAM -> Encryption keys -> Configuration -> Advances settings -> KMS key and pasted the sample code in the lambda function but the lambda function timed out without giving an error message. I imported the b64decode  module from base64  in the Python code but there must be an issue with this instructions that decrypts the variable ENCRYPTED :
  • Python 2.7: I wanted to use Python 3 but I had issues with the installation of some modules. Therefore I used Python 2.7 but the code should be compatible with Python 3 (apart from the imported modules).


Integrating AWS Lambda and Jenkins requires a little bit of configuration but I hope this tutorial may help other people to set it up. If the integration needs to be done the other way round (i.e. trigger a lambda function from a Jenkins job), check out the AWS Lambda Plugin.

I believe integrating AWS Lambda (or any FaaS) with Jenkins (or any CI/CD server) is particularly suited for the following uses cases:

  • Organisations that already have some DevOps practices in place and a history of build jobs but want to take advantages of the serverless workflow without completely re-architecturing their infrastructure. 
  • CI/CD pipelines that need be triggered by events but are too complex or long to be crammed in a single function.

XSpec v0.5.0

Image  XSpec MIT License

XSpec is a unit test and behaviour driven development (BDD) framework for XSLT and XQuery. I picked up this open source project at work for testing our XSLT and I’m now actively contributing to it together with the XSpec community.

XSpec v0.5.0 has just been released and is the new XSpec release after 5 years. It includes new features like XSLT 3 support, JUnit report for integration with Continuous Integration tools, support for Saxon-B, etc. It also fixes long standing regression bugs as well as integration bugs in the code coverage, provides feature parity between the shell and batch scripts, integrates an automated test suite, and updates the documentation in the wiki. More information on the official release notes


How to delete a branch in git

Git Logo
Image by Jason Long CC BY 3.0

Git encourages branching but sometimes you need to do a clean up and delete merged or orphaned branches from your local and remote repositories. Here is the procedure from the command line.

To delete a branch locally:

You may get an error like this one if the branch has not been merged yet:

This is a good reminder in case you are deleting something you should not be deleting.

To delete a branch remotely (e.g. on a GitHub repository):

How to force HTTPS on Apache

HTTPS image

I recently added an SSL certificate to this website. I used Let’s Encrypt which is an awesome initiative to increase the use of HTTPS in websites by making SSL certificates free and easy to install.

My web hosting provider offers Let’s Encrypt certificates via cPanel so installing one for my website was as easy as clicking few buttons. If you are not that lucky, Let’s Encrypt provides instructions to install certificates via the shell as well as a list of hosting providers supporting Let’s Encrypt.

Once you have your SSL certificate installed on your server, you may want to force HTTPS so that any request for HTTP pages will automatically be redirected to HTTPS.

The Apache web server provides the .htaccess file to store Apache configuration on a per-directory basis. For example, if your website is stored under /var/www/html/mysite  and you’re using Apache, you can create the following .htaccess  file in that directory:

The third line is the rewrite rule that forces HTTPS for any request made to the web server. Note that you need to have the mod_rewrite module installed on Apache to add rewrite rules for URL redirection.


Make sure that the URL in the rewrite rule is the one used in the SSL certificate. I initially put www.sandrocirulli.net  in the rewrite rule even though I register the SSL certificate for sandrocirulli.net  and all its sub-domains (including www.sandrocirulli.net ) and got nasty security warnings displaying on the browser. You can easily check the SSL certificate with any browser by clicking on the green padlock near the URL and select View Certificate or the like:

View CertificateIf the padlock near the URL displays a warning, click on it and see what’s the problem. I initially encountered issues with mixed content. This occurred because I had links to images on the websites with HTTP instead of HTTPS. All the major browsers allow you to see where the error occurs, just click on the warning and then Details or the like. Changing these links to HTTPS solved the issue with mixed content.

CD Summit and Jenkins Days 2016

CD Summit and Jenkins Days Berlin 2016
Image by DevOps Connect ©

This week I’m giving a talk about Continuous Security with Jenkins, Docker Bench, and Amazon Inspector at CD Summit & Jenkins Days in Amsterdam and in Berlin. CD Summit & Jenkins Days are a series of conferences in the US and in Europe focusing on Continuous Integration (CI) and Continuous Delivery (CD).

This is the abstract of my talk:

Security testing is often left out from CI/CD pipelines and perceived as an ad hoc and one-off audit performed by external security experts. However, the integration of security testing into a DevOps workflow (aka DevSecOps) allows to achieve security by design and to continuously assess software vulnerabilities within a CI/CD pipeline. But how does security fit in the world of cloud and microservices?

In this talk I show how to leverage tools like Jenkins, Docker Bench , and Amazon Inspector to perform security testing at the operating system and container levels in a cloud environment and how to integrate them into a typical CI/CD workflow. I discuss how these tools can help assessing the risk of security vulnerabilities during development, improving security and compliance, and lower support costs in the long term.

I also present two demos showing how to integrate Docker Bench with Jenkins and how to run Amazon Inspector from Jenkins.

The slides of my talk are available here.

Continuous Security with Jenkins and Amazon Inspector

Amazon Inspector
Image by Amazon Web Services, Inc. ©

Amazon Inspector is an automated security assessment service on Amazon Web Services (AWS). It allows to identify security vulnerabilities at operating system and network levels by scanning the host against a knowledge base of security best practices and rules.

I recently integrated Amazon Inspector to run in a Jenkins job so that security testing can be automated and performed prior to deployment to production.

AWS Configuration

The first thing to do is to set up the assessment target and assessment template in Amazon Inspector. An assessment target allows to select the EC2 instances via their tags in order to include them in the security scan. Here is an example of my assessment target for the EC2 instances tagged as gadictionaries-leap-ogl-stage-v360 :

Assessment TargetThe assessment template allows to specify the type of scan and its duration and is linked to the assessment target set up above. Here is an example of my assessment template (ARN is masked for security reasons). I selected the Common Vulnerabilities and Exposures (CVE) rule package scanning for 15 minutes (one hour is the recommended duration time to reliable results).

Assessment Template

Jenkins Configuration

We now move to the Jenkins configuration in order to run the security scan via a Jenkins job instead of using the AWS console.

The first thing to do is to make sure that openssh is installed on the instance where Jenkins is running and on the host you want to check. For example, on Ubuntu you can install openssh with:

Then install the SSH Agent plugin in Jenkins. This will provide Jenkins with SSH credentials to automatically login into a machine on the cloud. Add the credentials in Jenkins -> Credentials -> System -> Global credentials (unrestricted) -> Add credentials -> SSH Username with private key. This is an example of my credentials for user jenkins (private key details are obfuscated):

set up mock SSH credentialsThen create a Jenkins job and select the SSH agent credentials for user jenkins in Build Environment:

SSH agent credentialsThis will allow Jenkins to ssh into the machine with the private key stored securely (make sure you only grant permission to configure Jenkins to administrators otherwise your private keys are not safe).

I like to parameterize my builds so that I can run Amazon Inspector on a specific EC2 instance within a given Elastic Beanstalk stack:


Then we set up build and post-build actions. The build executes a shell script invoke_aws_inspector.sh pulled from the version control system. The post-build action provides the location of the JUnit file.

The shell script invoke_aws_inspector.sh looks like this:

The shell script works as follows:

  • line 4 allows Jenkins to ssh into a host (I’m using AWS EC2 as you can guess by the username ec2-user, replace it with your default username but do not user root). Note that the environment variable $HOSTNAME is passed from the parameter we set up earlier. The EOF allows to run a sequence of commands directly on the host so that you don’t have to disconnect every time. The single quotes are important, don’t skip them!
  • lines 5-8 install and start the Amazon Inspector agent on the host
  • lines 12-13 configure and set up a Python script  execute_aws_inspector.py  for running Amazon Inspector (we’ll see it in a minute)
  • lines 16-18 remove the Amazon Inspector agent so that no trace is left on the host
  • the final EOF disconnect Jenkins from host

The Python script execute_aws_inspector.py uses the Boto3 library for interacting with AWS services. The script looks like this:

The Python script works as follows:

  • lines 10-17 read the environment variable set in the parameterized build and select the correct template (I set up two different template for two different stacks, the ARNs are obfuscated for security reasons)
  • lines 20-26 run the assessment template and waits a bit longer than 15 minutes so that the scan can finish
  • lines 29-39 filters findings with severities High and Medium
  • lines 42-58 serialize the findings into a JUnit report so that they can be automatically read by Jenkins

Finally, here is an example of Test Result Trend and JUnit test results showing security vulnerabilities on an EC2 instance running unpatched packages:

JUnit Report

Happy security testing with Jenkins and Amazon Inspector!