122 lines
4.0 KiB
Markdown
122 lines
4.0 KiB
Markdown
# SSL/TLS Certificates
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X.509 is an ITU standard defining the format of public key certificates. X.509 are used in TLS/SSL, which is the basis for HTTPS. An X.509 certificate binds an identity to a public key using a digital signature. A certificate contains an identity (hostname, organization, etc.) and a public key (RSA, DSA, ECDSA, ed25519, etc.), and is either signed by a Certificate Authority or is Self-Signed.
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## Self-Signed Certificates
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### Generate CA
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1. Generate RSA
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```bash
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openssl genrsa -aes256 -out ca-key.pem 4096
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```
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2. Generate a public CA Cert
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```bash
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openssl req -new -x509 -sha256 -days 365 -key ca-key.pem -out ca.pem
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```
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### Optional Stage: View Certificate's Content
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```bash
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openssl x509 -in ca.pem -text
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openssl x509 -in ca.pem -purpose -noout -text
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```
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### Generate Certificate
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1. Create a RSA key
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```bash
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openssl genrsa -out cert-key.pem 4096
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```
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2. Create a Certificate Signing Request (CSR)
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```bash
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openssl req -new -sha256 -subj "/CN=yourcn" -key cert-key.pem -out cert.csr
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```
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3. Create a `extfile` with all the alternative names
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```bash
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echo "subjectAltName=DNS:your-dns.record,IP:257.10.10.1" >> extfile.cnf
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```
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```bash
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# optional
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echo extendedKeyUsage = serverAuth >> extfile.cnf
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```
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4. Create the certificate
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```bash
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openssl x509 -req -sha256 -days 365 -in cert.csr -CA ca.pem -CAkey ca-key.pem -out cert.pem -extfile extfile.cnf -CAcreateserial
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```
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## Certificate Formats
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X.509 Certificates exist in Base64 Formats **PEM (.pem, .crt, .ca-bundle)**, **PKCS#7 (.p7b, p7s)** and Binary Formats **DER (.der, .cer)**, **PKCS#12 (.pfx, p12)**.
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### Convert Certs
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COMMAND | CONVERSION
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---|---
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`openssl x509 -outform der -in cert.pem -out cert.der` | PEM to DER
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`openssl x509 -inform der -in cert.der -out cert.pem` | DER to PEM
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`openssl pkcs12 -in cert.pfx -out cert.pem -nodes` | PFX to PEM
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## Verify Certificates
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`openssl verify -CAfile ca.pem -verbose cert.pem`
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## Install the CA Cert as a trusted root CA
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### On Debian & Derivatives
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- Move the CA certificate (`ca.pem`) into `/usr/local/share/ca-certificates/ca.crt`.
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- Update the Cert Store with:
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```bash
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sudo update-ca-certificates
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```
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Refer the documentation [here](https://wiki.debian.org/Self-Signed_Certificate) and [here.](https://manpages.debian.org/buster/ca-certificates/update-ca-certificates.8.en.html)
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### On Fedora
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- Move the CA certificate (`ca.pem`) to `/etc/pki/ca-trust/source/anchors/ca.pem` or `/usr/share/pki/ca-trust-source/anchors/ca.pem`
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- Now run (with sudo if necessary):
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```bash
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update-ca-trust
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```
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Refer the documentation [here.](https://docs.fedoraproject.org/en-US/quick-docs/using-shared-system-certificates/)
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### On Arch
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System-wide – Arch(p11-kit)
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(From arch wiki)
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- Run (As root)
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```bash
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trust anchor --store myCA.crt
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```
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- The certificate will be written to /etc/ca-certificates/trust-source/myCA.p11-kit and the "legacy" directories automatically updated.
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- If you get "no configured writable location" or a similar error, import the CA manually:
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- Copy the certificate to the /etc/ca-certificates/trust-source/anchors directory.
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- and then
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```bash
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update-ca-trust
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```
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wiki page [here](https://wiki.archlinux.org/title/User:Grawity/Adding_a_trusted_CA_certificate)
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### On Windows
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Assuming the path to your generated CA certificate as `C:\ca.pem`, run:
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```powershell
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Import-Certificate -FilePath "C:\ca.pem" -CertStoreLocation Cert:\LocalMachine\Root
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```
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- Set `-CertStoreLocation` to `Cert:\CurrentUser\Root` in case you want to trust certificates only for the logged in user.
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OR
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In Command Prompt, run:
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```sh
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certutil.exe -addstore root C:\ca.pem
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```
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- `certutil.exe` is a built-in tool (classic `System32` one) and adds a system-wide trust anchor.
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### On Android
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The exact steps vary device-to-device, but here is a generalised guide:
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1. Open Phone Settings
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2. Locate `Encryption and Credentials` section. It is generally found under `Settings > Security > Encryption and Credentials`
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3. Choose `Install a certificate`
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4. Choose `CA Certificate`
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5. Locate the certificate file `ca.pem` on your SD Card/Internal Storage using the file manager.
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6. Select to load it.
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7. Done!
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