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ACME (aka Letsencrypt) support for DFN's PKI

This project provides support for ACME-based certificates using the DFN PKI. The DFN PKI provides a SOAP-based API for requesting and approving certificate requests. However, it currently does not support ACME clients.

Hence, this project implements the following: ACME client <---> ACME server <---> DFN PKI SOAP API.

Overview

It is based on the ACME server implementation acme2certifier (in Python) and the SOAP client provided by DFN-CERT Services GmbH, Hamburg, Germany and its contributors. (cf. SOAP-Client Version 4.3) written in Java.

This project is comprised of two parts:

  • acme2file: A custom ca_handler.py for acme2certifier.
  • file2dfn: A Java program interacting with DFN's SOAP service.

acme2file

A Python handler script that receives incoming CSRs from acme2certifier (the ACME server).

It works as follows:

  • Invoked by acme2certifier, it receives incoming CSRs from ACME clients (after the challenges have completed)
  • Writes CSRs to a directory
  • Waits for certificates to appear in this directory
  • Notifies acme2certifier by invoking the trigger endpoint

file2dfn

Java program for interacting with DFN's SOAP API to request certificates and to approve them.

It works as follows:

  • It watches for new CSRs in the aforementioned directory (stored there by acme2file). The files must have a prefix new- and suffix .csr. Everything in between is treated as an identifier used by acme2file.
  • Submits each CSR to the DFN SOAP server and approves them
  • Polls the SOAP server for matching certificates and stores them in the directory in the form "cert-" + acmeId + ".crt".

Usage

Configuration

Create a directory structure as follows:

private/configdir/
├── ca-name.txt
├── ca.p12
├── password.txt
├── pin.txt
├── ra-id.txt
└── role.txt

and populate the files (except for audit-smtp*) according to DFN PKI's documentation (e.g., role.txt may contain Web Server).

Using SMTP Audit Logging

To use SMTP for auditing purposes, configure command line option -audit smtp

Add the folloging files to the configmap abouve.

Set SMTP options in audit-smtp.json as follows

{
	"Username": "...",
	"Password": "...",
	"Host": "...",
	"Port": 25,
	"Sender": "...",
	"Recipient": "...",
	"Subject": "[acme2file] Audit log message",
	"Text": "See attachment."
}

and create a private (audit-smtp-priv.pem) and public (audit-smtp-pub.pem ) key using commands such as:

openssl genrsa -out audit-smtp-priv.pem 4096
openssl rsa -in audit-smtp-key.pem -pubout -outform PEM -out audit-smtp-pub.pem

To verify the signature in the mail, use a command similar to this:

cat audit.json | openssl dgst -sha512 -verify private/configdir/audit-smtp-pub.pem -signature signature.asc

Create configuration map

Then, create config map in your Kubernetes cluster:

kubectl create configmap acme2file-configmap --from-file=private/configdir

(add -o yaml --dry-run to see the result only)

Run the ACME server

Run skaffold dev

Testing

file2dfn dry-run (i.e., without accessing the SOAP API)

For development, a local dry-run is supported:

(cd file2dfn ; mvn exec:java -Dexec.mainClass=de.farberg.file2dfn.Main -Dexec.args="-dryrun -configdir ../private/configdir/ -dryrunCsrFile ../private/csr-base64.txt -dryrunCertFile ../private/example-cert.pem")

Testing with certbot

To run an interactive ACME test client in Kubernetes, use the following command:

# Create an interactive pod with certbot installed
kubectl delete pod/certbot ; kubectl run certbot --command=true --rm -ti --image certbot/certbot -- /bin/sh

# Obtain the primary IP and the pods Kubernetes DNS name
# cf. https://kubernetes.io/docs/concepts/services-networking/dns-pod-service/#a-aaaa-records-1
PRIMARY_IP=`ifconfig | grep -Eo 'inet (addr:)?([0-9]*\.){3}[0-9]*' | grep -Eo '([0-9]*\.){3}[0-9]*' | grep -v '127.0.0.1'`
MY_HOSTNAME="`echo $PRIMARY_IP | tr '.' '-'`.default.pod.cluster.local"
CERTBOT_COMMON_ARGS="--config-dir /tmp/acme/conf --work-dir /tmp/acme/work --logs-dir /tmp/acme/logs --agree-tos -m bla@bla.de --server http://acme2file-service --no-eff-email --standalone --debug"

# Register the account with the ACME server and obtain certificate
rm -rf /tmp/acme ; certbot $CERTBOT_COMMON_ARGS register ; certbot $CERTBOT_COMMON_ARGS --preferred-challenges http -d "$MY_HOSTNAME" --cert-name certbot-test certonly

Acknowledgements

Libraries used and included in this repository

Internal Stuff

Record asciinema

Record asciinema in Iterm2

  • tmux -CC new -s myrec and resize to 150 x 40
  • tmux set status off ; export PS1='${PWD/*\//}$ '
  • Split screen as required

In another shell

  • Run asciinema rec --overwrite -i 2 -c "tmux attach -t myrec" demo.cast
  • Detach the session in tmux: ctrl + b + d
  • Convert to SVG using cat demo.cast | svg-term --out demo.svg --term iterm2 --window --profile iterm2

Add a new version of DFN's libs

These are stored in the folder file2dfn/local-maven-repo

# Soapclient
mvn deploy:deploy-file \
	-Durl=file:./local-maven-repo/ \
	-DrepositoryId=local-maven-repo \
	-DupdateReleaseInfo=true \
	-DgroupId=de.dfncert \
	-DartifactId=soapclient \
	-Dversion=4.3 \
	-Dfile=soapclient-4.3.jar

# Utils
mvn deploy:deploy-file \
	-Durl=file:./local-maven-repo/ \
	-DrepositoryId=local-maven-repo \
	-DupdateReleaseInfo=true \
	-DgroupId=de.dfncert \
	-DartifactId=utils \
	-Dversion=2.13 \
	-Dfile=utils-2.13.jar