241 lines
6.1 KiB
Markdown
241 lines
6.1 KiB
Markdown
# OpenPGP Workshop
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[important reference](img/iceberg.png)
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---
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## What is OpenPGP
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* OpenPGP is an open standard for encrypting and decrypting data, as well as
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creating and managing digital signatures.
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* It is based on the PGP (Pretty Good Privacy) protocol, which was originally
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developed by Phil Zimmermann in the 1990s.
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* Uses asymmetric / public key cryptography
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<!--
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What are some useful ways we can use OpenPGP:
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* Email encryption and signing
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* Signing git commits
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* SSH
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* Password management
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-->
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---
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## Implementations
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* GPG
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* Gnu Privacy Guard
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* Best known and most widely used
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* Great starting point
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* There are lots of other implementations of OpenPGP:
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* https://www.openpgp.org/software/developer/
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---
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## How Does It Work?
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---
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## Encrypt / Decrypt
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---
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## Sign / Verify
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---
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## Diffie Helman Key Exchange
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---
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## OpenPGP Anatomy
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* Many components but key ones are:
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* Public Key
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* Private Key
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---
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## Let's Try It!
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* Most OS come with GPG pre-installed (not Windows!)
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* `gpg --version`
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* `man gpg`
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* **THESE FOLLOWING KEYS WILL NOT BE SECURE, DO NOT USE THEM FOR ANYTHING OTHER THAN THIS EXERCISE!**
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* Generate keypair: `gpg --expert --full-gen-key`
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* 1, 4096, Enter (3072), Enter (0), y, "Test Key", <your_email>, Enter (""), O, "password1"
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* Use a unique email otherwise you will have issues with the exercise that follows
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* During generation, **mash input devices for added entropy**
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---
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## Test Your GPG Key
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* `gpg --list-keys`
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* `echo "super secret text" > test.txt && cat test.txt`
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* `gpg --encrypt --recipient <email/ID> test.txt`
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* `gpg -er <email/ID> <filename> && cat test.txt.gpg`: notice it's a binary
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* You can use `--armor/-a` to encode it as ASCII so you can send the encrypted data as text
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* `gpg --armor -er <email/ID> test.txt && cat test.txt.asc`
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* `rm test.txt && ls`
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* `gpg --decrypt test.txt.gpg > test.txt`
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* `gpg --decrypt test.txt.asc > test.txt`
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---
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## Sharing Your Public Key 🔑
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* `gpg --list-keys`
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* `gpg --export --armor <email/ID> > <name>.asc`
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* `gpg --import <name>.asc`
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* Task: pair up and exchange your keys, encrypt data to each other, then decrypt the message so you can tell your partner the contents of the message
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* Tip: you may encrypt the data to multiple people
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---
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## Verifying Signatures 📝
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* Go to: https://www.qubes-os.org/downloads/
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* Download:
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* Qubes-R*.iso
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* Cryptographic hash values
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* `gpg --verify --default-key <key> <filename>`
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* Detached PGP signature
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* Qubes release signing key
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* They have a guide that's worth reading: https://www.qubes-os.org/security/verifying-signatures/
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* Task: verify the signatures for the software are valid
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---
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## Solution
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* `gpg --import qubes-release-*`: import qubes signing key
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* `gpg --verify *.DIGESTS`: verify signature
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* `sha256sum -c Qubes-<...>.iso.DIGESTS`: verify hashes match
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---
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## Secure Key Management 🔒
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* You should assume your computer is compromised
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* How do we protect the GPG private key?
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* Never expose them to an untrusted environment
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---
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## Basic: On-board generation:
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* YubiKey offers generating keys inside of the YubiKey
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* Cryptographic attestation keys were never exposed available: https://developers.yubico.com/PGP/Attestation.html
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* CON: can't back up the keys
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* PRO: simple setup
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---
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## Advanced - cold / virtualization
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* Can use `gpg` / `sq` / `keyfork` to derive
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* Key is to derive keys in a secure environment:
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* Airgapped system (preferred)
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* [AirgapOS](https://git.distrust.co/public/airgap): A full-source-bootstrapped, deterministic, minimal, immutable, and offline, workstation linux distribution designed for creating and managing secrets offline.
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* Virtual machine on a hypervisor via hardware virtualization (ok for some threat models)
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* [Hashbang GPG Guide](https://book.hashbang.sh/docs/security/key-management/gnupg/): helpful guide for GPG - good resource for beginners who want to do the advanced setup
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* [openpgp-card-tools](https://codeberg.org/openpgp-card/openpgp-card-tools): great for loading keys onto smart cards
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* Can use a variety of smart cards: NitroKey3, SoloKey, Yubikey
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* NitroKey and SoloKey are fully open which is great for verifiability - may requires flashing firmware
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* [Quorum Key Management](https://docs.distrust.co/qkm/)
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---
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## Backup Trick 🧙
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* Generate long lived keys
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* Load them onto smart card
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* Take plaintext key data and put it in a dir
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* Encrypt the dir to your public key
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* Delete keys so that only ones that remain are on smart cards (recommended to have at least 2 or 3, for redundancy)
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* Smart cards have a "brick" after x attempts feature
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---
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## SSH Usage
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* OpenPGP keys can be used for SSH as well 🪄:
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* `gpg --export-ssh-key <email/keyID>`
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* Set up shell to use smart card for ssh:
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```
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# always use smart card for ssh
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unset SSH_AGENT_PID
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if [ "${gnupg_SSH_AUTH_SOCK_by:-0}" -ne $$ ]; then
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export SSH_AUTH_SOCK="$(gpgconf --list-dirs agent-ssh-socket)"
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fi
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```
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---
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## Git Usage
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* You can sign commits using OpenPGP / GPG
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```~/.bashrc
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GPG_TTY=$(tty)
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export GPG_TTY
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```
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```~/.gitconfig
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[user]
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email = <email>
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name = <name>
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signingKey = <key_id>
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[commit]
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gpgSign = true
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[merge]
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gpgSign = true
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[gpg]
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program = gpg
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```
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---
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## Further Studies
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* [keyoxide](https://keyoxide.org/): decentralized tool to create and verify decentralized online identities
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* [pass](https://www.passwordstore.org/): Unix based `gpg` password manager
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* [OpenPGP for application developers](https://openpgp.dev/book/): Deep dive on OpenPGP
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* [Sequoia](https://sequoia-pgp.org/): alternate OpenPGP implementation in rust
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* [openpgp-card](https://codeberg.org/openpgp-card)
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* [openpgp-card-tools](https://codeberg.org/openpgp-card/openpgp-card-tools)
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* [ssh-agent](https://codeberg.org/openpgp-card/ssh-agent)
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---
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# Cleanup
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* `gpg --delete-secret-and-public-keys <key_id>`
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