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99 lines
2.9 KiB
Markdown
99 lines
2.9 KiB
Markdown
---
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title: "Quick CA for internal LAN"
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date: 2020-04-18T16:26:53-04:00
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draft: false
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tags: ["network"]
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---
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Setting up trusted HTTPs inside a network without exposure to the Internet requires creating a Certificate Authority. The audience for this post is oriented for people setting up services in a small low threat model environment. Additional cautions should be applied when setting this up for a business, for example working off an intermediate CA.
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We're going to be using [CFSSL](https://blog.cloudflare.com/introducing-cfssl/), this is Cloudflare's PKI toolkit to accomplish this. To install on Ubuntu,
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```bash
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sudo apt install golang-cfssl
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```
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## Creating the CA
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This tool makes heavy use of JSON for its configuration. To setup a CA, first let's create `csr_ca.json` that contains the following information
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```json
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{
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"CN": "Common Name",
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"key": {
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"algo": "rsa",
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"size": 2048
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},
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"names": [
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{
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"C": "US",
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"O": "Orgnaization",
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"OU": "Organizational Unit",
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"ST": "Washington",
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"L": "Locality"
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}
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]
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}
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```
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Where `C` is the two-letter country code and `ST` is the full state name.
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Then to create the certificate authority
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```bash
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cfssl gencert -initca csr_ca.json | cfssljson -bare ca
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```
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This will create the following files
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| Filename | Purpose |
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| ---------- | --------------------------- |
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| ca.pem | Public Certificate |
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| ca-key.pem | Private Key |
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| ca.csr | Certificate Signing Request |
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## Creating Certficates
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Now we can create SSL certificates for whatever websites we wish by specifying in a file we'll call `csr_client.json`
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```json
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{
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"hosts": [
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"example.com",
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"*.example.com"
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],
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"key": {
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"algo": "rsa",
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"size": 2048
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},
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"names": [
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{
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"C": "US",
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"O": "Orgnaization",
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"OU": "Organizational Unit",
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"ST": "Washington",
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"L": "Locality"
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}
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]
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}
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```
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Then to create the certs,
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```bash
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cfssl gencert -ca=ca.pem -ca-key=ca-key.pem csr_client.json | cfssljson -bare cert
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```
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It will create the private key, public certificate, and CSR just like the previous command. By default the certificate will last for one year and has the following usages:
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- Signing
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- Key Encipherment
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- Server Authentication
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- Client Authentication
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To have more full grained control over the certificate usages and expiry time, I will defer you to the documentation. It involves creating another JSON file to pass as a flag into `cfssl gencert`.
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## Trusting the CA
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To trust the CA on Linux, you need to copy the `ca.pem` file over to `/usr/local/share/ca-certificates/` and then execute `sudo update-ca-certificates`. Firefox has its own certificate store that you can add `ca.pem` to by accessing Preferences->Privacy & Security->Security->Certificates->View Certificates->Authorities->Import. The exact trail might have changed by the time you read this.
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