Pivotal Engineering Journal

Technical articles from Pivotal engineers.

Deploying a BOSH Director With SSL Certificates Issued by Recognized CA

A BOSH director is typically deployed with self-signed SSL (Secure Sockets Layer) certificates; however, the director can be deployed with certificates issued by a trusted CA (Certificate Authority). Here’s how.

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0. Abstract

A BOSH director is a virtual machine (VM) orchestrator which deploys VMs to various Infrastructures as a Service (IaaS) such as Amazon Web Services (AWS) and Google Cloud Platform (GCP). The BOSH Command Line (CLI) communicates with the director over Secure Sockets Layer (SSL). While most BOSH directors are deployed with self-signed certificates, it is possible to configure a BOSH director with certificates issued by a recognized certificate authority (CA) (e.g. Comodo, Symantec, Let’s Encrypt). This blog post describes a technique to deploy a BOSH director with a CA-issued SSL certificate.

Additionally, this blog posts describes a mechanism to override the automatically-generated passwords (e.g. for logging into the director from the CLI).

This blog post may be of use to organizations who desire the following:

  • use CA-issued SSL certificates on their BOSH director
  • set specific passwords on the BOSH director’s services (e.g. login, PostgreSQL)
  • dispense with the --var-store file (which stores the auto-generated passwords and the self-signed SSL certificate authority’s certificate), a file created by the BOSH CLI during deployment and which normally must be stored in a safe & secure manner

This blog posts assumes familiarity with BOSH CLI v2 and with the procedure to deploy a BOSH director.

The blog post describes deploying (i.e. creating) a BOSH director (bosh-gce.nono.io) to the Google Cloud Platform.

1. Overview of the Procedure To Deploy a BOSH Director

The procedure to deploy a BOSH director with valid SSL certificate is a superset of the normal procedure to deploy a BOSH director, with an additional step: using bosh interpolate to create an intermediate manifest.

Below is a visual diagram of the process:

2. Deploying the BOSH Director to GCP

2.1 Pre-requisites: IP addresses, DNS Records, and SSL Certificates

We are deploying our BOSH director to Google Cloud Platform (GCP), so we acquire an external IP address via the GCP console.

  • 104.154.39.128 — the external IP address acquired from GCP. Note that the IP address need not be a public address — in fact, most BOSH directors have private (RFC 1918) addresses. Having one’s BOSH directors reachable solely via a jumpbox adds a layer of security.
  • bosh-gce.nono.io — the DNS record must point to the director’s IP address (i.e. 104.154.39.128) (dig +short bosh-gce.nono.io returns the expected IP address).
  • SSL Certificate — we use a wildcard certificate (i.e. *.nono.io), but a wildcard certificate is not necessary, and a regular SSL certificate (e.g. bosh-gce.nono.io) is much less expensive.

2.2 Create a Manifest Operations (gce.yml) File to Insert the SSL Certificate

We create a manifest operations YAML file (gce.yml) that contains the directives to adjust the generic BOSH director’s manifest template (bosh.yml) to use our CA-issued certificate. Our certificate is a chained certificate, which means that it includes the CA bundle (i.e. the certificates of the CAs that issued our certificate). [Chained Certificate]

We use a variables to substitute the SSL certificate and key in our manifest (((nono_io_crt)) and ((nono_io_key)), respectively), which will be interpolated in the second stage (double parentheses, “(())”, are an indicator to the BOSH CLI parser to perform variable substitution).

Below is a shortened version of our manifest operations file; the full one can be viewed on GitHub:

- type: replace
  path: /instance_groups/name=bosh/properties/director/ssl/key?
  value: ((nono_io_key))
- type: replace
  path: /instance_groups/name=bosh/properties/director/ssl/cert?
  value: ((nono_io_crt))

2.3 Create the SSL Certificate (nono.io.crt) File

We create a PEM-formatted (Privacy Enhanced Mail) file that contains the SSL chained certificate.

We will set the nono_io_crt variable via the CLI to the contents of the nono.io.crt file when we perform our first stage, interpolation, which will substitute the SSL certificate in the appropriate locations.

Our certificate file can be viewed on GitHub.

2.4 Run bosh interpolate to Create Intermediate Manifest

We run the bosh interpolate to create our intermediate manifest, bosh-gce.yml.

bosh interpolate ~/workspace/bosh-deployment/bosh.yml \
  -o ~/workspace/bosh-deployment/misc/powerdns.yml \
  -o ~/workspace/bosh-deployment/gcp/cpi.yml \
  -o ~/workspace/bosh-deployment/external-ip-not-recommended.yml \
  -o ~/workspace/bosh-deployment/jumpbox-user.yml \
  -o etc/gce.yml \
  --var-file nono_io_crt=etc/nono.io.crt \
  -v dns_recursor_ip="169.254.169.254" \
  -v internal_gw="10.128.0.1" \
  -v internal_cidr="10.128.0.0/20" \
  -v internal_ip="10.128.0.2" \
  -v external_ip="104.154.39.128" \
  -v network="cf" \
  -v subnetwork="cf-e6ecf3fd8a498fbe" \
  -v tags="[ cf-internal, cf-bosh ]" \
  -v zone="us-central1-b" \
  -v project_id="blabbertabber" \
  -v director_name="gce" \
  > bosh-gce.yml

The first argument to bosh interpolate is the BOSH director manifest template file, ~/workspace/bosh-deployment/bosh.yml. This has the generic defaults for a BOSH director (e.g. persistent disk size of 32,768MB, the five jobs of the director, etc…). The source of this file is the bosh-deployment git repo, which has been cloned to ~/workspace/bosh-deployment/ on our workstation.

The -o (--ops-file) (“manifest operations from a YAML file”) are a set of files which configure the BOSH director with specific attributes. With the exception of our custom (gce.yml), the manifest operations files reside in the bosh-deployment repository.

Here is the list of manifest operations files and their purpose:

  • misc/powerdns.ym: this is only needed for dynamic networks, where the IaaS, rather than the director, assigns IP addresses to the VMs deployed by the director. The BOSH development team is doing interesting work with hostname resolution (DNS), and this particular manifest operations file will likely be deprecated soon.
  • gcp/cpi.yml: this is needed for deploying a BOSH director to GCP, it sets properties such as machine_type (n1-standard-1).
  • external-ip-not-recommended.yml: this is not recommended for general use; it’s for deploying a BOSH director with a publicly-accessible IP address. [Security]
  • jumpbox-user.yml: this creates an account, jumpbox, on the director. This account has sudo privileges and can be ssh’ed into using an ssh key. In our example, the interpolated variable gce_jumpbox_user_public_key, contains the public key which will be inserted into the file ~jumpbox/.ssh/authorized_keys on the BOSH director. The private key is kept in ~/.ssh/google on our workstation. The command to ssh into our director is the following: ssh -i ~/.ssh/google jumpbox@bosh-gce.nono.io

The --var-file nono_io_crt=etc/nono.io.crt directive tells the BOSH CLI to substitute every occurrence of ((nono_io_crt)) with the contents of the file etc/nono.io.crt) (our SSL certificate).

The -v arguments set variables which are interpolated, e.g. -v dns_recursor_ip="169.254.169.254" replaces occurrences of ((dns_recursor_ip)) with 169.254.169.254 in our manifest.

We use a script to create our intermediate manifest; our script can be viewed on GitHub.

Our intermediate manifest (without secrets) can also be seen on GitHub.

2.5 Create a Secrets File

We create a YAML file with our secrets (passwords and keys). These will be substituted during the second stage (bosh create-env). Below is a redacted version of our file (the passwords aren’t the real passwords; don’t even bother trying to use them) (the public ssh key, however, is the real deal) (the GCP credentials JSON values are mostly real, too):

admin_password: IReturnedAndSawUnderTheSun
blobstore_agent_password: ThatTheRaceIsNotToTheSwift
blobstore_director_password: NorTheBattleToTheStrong
hm_password: NeitherYetBreadToTheWise
mbus_bootstrap_password: NorYetRichesToMenOfUnderstanding
nats_password: NorYetFavourToMenOfSkill
postgres_password: ButTimeAndChanceHappenethToThemAll

gce_jumpbox_user_public_key: "ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQC9An3FOF/vUnEA2VkaYHoACjbmk3G4yAHE3lXnGpIhz3EV5k4B5RzEFKZnAIFcX18eBjYQIN9xQO0L9xkhlCyrQHrnXBjCDwt/BuQSiRvp3tlx9g0tGyuuJRI5n656Shc7w/g4UbrQWUBdLKjxTT4kTgAdK+1pgDbhAXdPtMwt4D/sz5OEFdf5O5Cp+0spxC+Ctdb94taZhScqB4xt6dRl7bwI28vZdq6Sjg/hbMBbTXzSJ17+ql8LJtXiUHO5W7MwNtKdZmlglOUy3CEIwDz3FdI9zKEfnfpfosp/hu+07/8Y02+U/fsjQyJy8ZCSsGY2e2XpvNNVj/3mnj8fP5cX cunnie@nono.io"

gcp_credentials_json: |
  {
    "type": "service_account",
    "project_id": "blabbertabber",
    "private_key_id": "642493xxxxxxx",
    "private_key": "-----BEGIN PRIVATE KEY-----\nMIIEvAIBADANBgkqhkiG9w0BYwoIBAQCtNvKlIorU1xlP\nlXOxMTS8lT2djHXXN2od0l1mR/\nX4tDHQ2DPvAuKXSLYfgQRuNlydxMQcN7Ln7aDtECgYAgTNO/7a9QjyVyov2tzZMT\nPG19XeHbuu/SZHcQqa+oEGWwTM02+TUCfaCQVOesxcRHjeGjCJbBC1jaWL7\nFRSsSpYEPdcaDO9p56CbebgGvrp790EgM1YvacjbW3CoUA\nG2B88HgJ5MmxAZRCuPaVjg==\n-----END PRIVATE KEY-----\n",
    "client_email": "bosh-user@blabbertabber.iam.gserviceaccount.com",
    "client_id": "11221xxxx",
    "auth_uri": "https://accounts.google.com/o/oauth2/auth",
    "token_uri": "https://accounts.google.com/o/oauth2/token",
    "auth_provider_x509_cert_url": "https://www.googleapis.com/oauth2/v1/certs",
    "client_x509_cert_url": "https://www.googleapis.com/robot/v1/metadata/x509/bosh-user%40blabbertabber.iam.gserviceaccount.com"
  }

nono_io_key: |
  -----BEGIN RSA PRIVATE KEY-----
  MIIEpQIBAAKCAQEAty5zouKiJfdQQ45DUR1AvhArzgwMAxf/c+2QEKueRSqCfm6l
  <snip>
  K+6Y18ijXoJimhW32UhmjnsmeAlq0/0HUvLBCe9mXlA8cWg533V3v30=
  -----END RSA PRIVATE KEY-----

2.6 Deploying the director

Deploying the director is a bit anticlimactic. In this example, we assume the name of the file which contains our secrets which we created in the previous step is named secrets.yml:

bosh create-env bosh-gce.yml -l secrets.yml

In a more complex example (we use LastPass™ to store our secrets in a note named deployments.yml), we take advantage of bash’s process substitution to take the output of the LastPass CLI’s command and make it appear as a file argument to the BOSH CLI:

bosh create-env bosh-gce.yml -l <(lpass show --note deployments.yml)

Remember to save the bosh-gce-state.json file — it contains the location of the persistent disk, which is important if you ever decide to re-deploy your BOSH director, for the director’s state (including deployments, releases, stemcells) is stored on the persistent disk.

3. Optimizations: Collapse Two Stages into One

The two stages can be collapsed into one by dispensing with the bosh interpolate section and merging its options with the bosh create-env step. Indeed, the only advantage of using a two-stage process is the creation of the intermediate BOSH director manifest file, bosh-gce.yml.

4. SSL Certificates on Other Infrastructures

This technique applies equally well to other IaaSes (such as AWS, Azure, and vSphere). As a proof of concept, we have deployed BOSH directors with CA-issued SSL certificates to each of the IaaSes listed below (ignore the “forbidden” page when clicking BOSH Director links; instead, pay attention to the valid SSL certificate presented to the browser):

Infrastructure BOSH Director (URL) BOSH Director Manifest
Amazon AWS https://bosh-aws.nono.io:25555/info bosh-aws.yml
Google GCP https://bosh-gce.nono.io:25555/info bosh-gce.yml
Microsoft Azure https://bosh-azure.nono.io:25555/info bosh-azure.yml
VMware vSphere https://bosh-vsphere.nono.io:25555/info bosh-vsphere.yml

Acknowledgements

Dmitriy Kalinin suggested collapsing the two stages into one, and making the title more accurate. Danny Berger suggested adopting a more objective tone with respect to the current set of security tools (i.e. iptables, SELinux, AppArmor, auditd).

Footnotes

[Security] The author has mixed feelings for many of the best-practices in the security space; for example, the author feels that firewalls are no substitute for knowing which services should (and should not) be running on one’s server and that tools such as AppArmor, SELinux, and auditd often introduce subtle and hard-to-debug failures at the expense of arguably modest security improvements.

[Chained Certificates] The order in which the certificates appear and whether the root certificate is included is important.

We recommend placing the server’s certificate topmost and the root certificate last in order to conform with the Transport Layer Security (TLS) Protocol Version 1.2 Request For Comment (RFC):

This is a sequence (chain) of certificates. The sender’s certificate MUST come first in the list. Each following certificate MUST directly certify the one preceding it. Because certificate validation requires that root keys be distributed independently, the self-signed certificate that specifies the root certificate authority MAY be omitted from the chain, under the assumption that the remote end must already possess it in order to validate it in any case.

We recommend omitting the root certificate (and so do others), for it is the one certificate that is included on every client machine, so there’s no need to transmit it (and if it’s not already on the client machine, then you have bigger worries).

The recommendation for certificate ordering has been borne out in practice. Apache, for example, recommends placing the server certificate first, and the root certificate last:

The files may also include intermediate CA certificates, sorted from leaf to root

Nginx makes a similar recommendation:

The server certificate must appear before the chained certificates in the combined file

Golang, too:

A Certificate is a chain of one or more certificates, leaf first.

For those curious about how a root certificate differs from a regular certificate, the answer is simple: the root certificate is a self-signed certificate. That is to say, the certificate’s Subject is the same as the Issuer.

We can use the openssl command to examine our server certificate and determine that the Issuer and Subject are different, and thus be sure that our server certificate is not a root certificate:

$ openssl x509 -in etc/nono.io.crt -noout -text | egrep "Subject:|Issuer:"
        Issuer: C=GB, ST=Greater Manchester, L=Salford, O=COMODO CA Limited, CN=COMODO RSA Domain Validation Secure Server CA
        Subject: OU=Domain Control Validated, OU=PositiveSSL Multi-Domain, CN=*.nono.io

The presence of the root certificate in the chain may cause validation problems; The author, for example, recollects fixing a problem where his web server’s certificate was flagged as invalid on Android (but not on other platforms). It was fixed by removing the root certificate from the certificate chain file.

Bibliography

bosh-deployment is a GitHub repository containing a collection of manifest templates and manifest operations files. Manifest operations files use the go-patch syntax.

go-patch is a tool which modifies a target YAML file based on directives, the directives which in turn are are also YAML files. go-patch is the mechanism which the BOSH CLI uses to apply changes to the BOSH template (e.g. external-ip-not-recommended.yml is a go-patch-format file in the bosh-deployment GitHub repo, which, when applied to the bosh.yml manifest file, creates the necessary properties for a BOSH director with an external IP address.

Corrections & Updates

2017-08-17

Clarified the author’s statement with regard to the pros and cons of current security practices. The original statement was controversial and could reflect poorly on the author and the journal. The present statement is more neutral in tone.

Removed an incomplete sentence, described the provenance of the --var-store file, clarified the contributions in the Acknowledgements section.

2017-08-18

Tweaked the wording in the title (added “Recognized CA”), emphasized collapsing the two stages into one, centered the labels in the boxes, updated the URL for go-patch.

2017-09-03

We dispensed with mbus_bootstrap_ssl file; it was both complex and unnecessary.

We fixed a bug where the mbus bootstrap SSL was interpolated incorrectly, resulting in an error (cannot unmarshal !!str 'certifi...' into manifest.Certificate) when using newer versions (>= 2.0.32) of the BOSH CLI.

We refactored the SSL certificate into its own file, nono.io.crt.

2017-09-07

Added the section, SSL Certificates on Other Infrastructures.