keyfork: add `bottoms-up` wizard

This commit is contained in:
Ryan Heywood 2024-07-29 00:48:10 -04:00
parent 142bea3b9f
commit 8d40d2630c
Signed by: ryan
GPG Key ID: 8E401478A3FBEF72
2 changed files with 85 additions and 4 deletions

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@ -83,7 +83,7 @@ fn validate(
let index = DerivationIndex::new(u32::from_be_bytes(pgp_u32), true)?; let index = DerivationIndex::new(u32::from_be_bytes(pgp_u32), true)?;
let path = DerivationPath::from_str(path)?; let path = DerivationPath::from_str(path)?;
assert_eq!(2, path.len(), "Expected path of m/{index}/account_id'"); assert!(path.len() >= 2, "Expected path of at least m/{index}/account_id'");
let given_index = path.iter().next().expect("checked .len() above"); let given_index = path.iter().next().expect("checked .len() above");
assert_eq!( assert_eq!(

View File

@ -1,20 +1,26 @@
use super::Keyfork; use super::Keyfork;
use clap::{Parser, Subcommand}; use clap::{Parser, Subcommand};
use std::{collections::HashSet, fs::File, io::IsTerminal, path::PathBuf}; use std::{
collections::HashSet,
fs::File,
io::IsTerminal,
path::{Path, PathBuf},
};
use card_backend_pcsc::PcscBackend; use card_backend_pcsc::PcscBackend;
use openpgp_card_sequoia::{state::Open, types::KeyType, Card}; use openpgp_card_sequoia::{state::Open, types::KeyType, Card};
use keyfork_derive_openpgp::{ use keyfork_derive_openpgp::{
openpgp::{self, packet::UserID, types::KeyFlags, Cert}, openpgp::{self, packet::UserID, types::KeyFlags, Cert, serialize::Marshal, armor::{Writer, Kind}},
XPrv, XPrv,
}; };
use keyfork_derive_util::{DerivationIndex, DerivationPath}; use keyfork_derive_util::{DerivationIndex, DerivationPath, VariableLengthSeed};
use keyfork_prompt::{ use keyfork_prompt::{
default_terminal, default_terminal,
validators::{SecurePinValidator, Validator}, validators::{SecurePinValidator, Validator},
DefaultTerminal, Message, PromptHandler, DefaultTerminal, Message, PromptHandler,
}; };
use keyfork_mnemonic_util::Mnemonic;
use keyfork_shard::{openpgp::OpenPGP, Format}; use keyfork_shard::{openpgp::OpenPGP, Format};
@ -24,6 +30,8 @@ pub struct PinLength(usize);
type Result<T, E = Box<dyn std::error::Error>> = std::result::Result<T, E>; type Result<T, E = Box<dyn std::error::Error>> = std::result::Result<T, E>;
// TODO: refactor to use mnemonic derived seed instead of 256 bit entropy to allow for possible
// recovery in the future.
fn derive_key(seed: [u8; 32], index: u8) -> Result<Cert> { fn derive_key(seed: [u8; 32], index: u8) -> Result<Cert> {
let subkeys = vec![ let subkeys = vec![
KeyFlags::empty().set_certification(), KeyFlags::empty().set_certification(),
@ -185,6 +193,46 @@ fn generate_shard_secret(
Ok(()) Ok(())
} }
fn bottoms_up(key_discovery: &Path, threshold: u8, output_shardfile: &Path, output_cert: &Path, user_id: &str,) -> Result<()> {
let entropy = keyfork_entropy::generate_entropy_of_const_size::<{ 256 / 8 }>()?;
let mnemonic = Mnemonic::from_nonstandard_bytes(entropy);
// TODO: make this return const size, since is hash based
let seed = mnemonic.generate_seed(None);
// TODO: should this allow for customizing the account index from 0? Potential for key reuse
// errors.
let path = DerivationPath::default()
.chain_push(DerivationIndex::new(u32::from_be_bytes(*b"\x00pgp"), true)?)
.chain_push(DerivationIndex::new(u32::from_be_bytes(*b"\x00\x00dr"), true)?)
.chain_push(DerivationIndex::new(0, true)?);
let subkeys = [
KeyFlags::empty().set_certification(),
KeyFlags::empty().set_signing(),
KeyFlags::empty()
.set_transport_encryption()
.set_storage_encryption(),
KeyFlags::empty().set_authentication(),
];
let xprv = XPrv::new(VariableLengthSeed::new(&seed))
.expect("could not construct master key from seed")
.derive_path(&path)?;
let userid = UserID::from(user_id);
let cert = keyfork_derive_openpgp::derive(xprv, &subkeys, &userid)?;
let certfile = File::create(output_cert)?;
let mut w = Writer::new(certfile, Kind::PublicKey)?;
cert.serialize(&mut w)?;
w.finalize()?;
let opgp = OpenPGP::<DefaultTerminal>::new();
let certs = OpenPGP::<DefaultTerminal>::discover_certs(key_discovery)?;
let shardfile = File::create(output_shardfile)?;
opgp.shard_and_encrypt(threshold, certs.len() as u8, &entropy, &certs[..], shardfile)?;
Ok(())
}
#[derive(Subcommand, Clone, Debug)] #[derive(Subcommand, Clone, Debug)]
pub enum WizardSubcommands { pub enum WizardSubcommands {
/// Create a 256 bit secret and shard the secret to smart cards. /// Create a 256 bit secret and shard the secret to smart cards.
@ -209,6 +257,32 @@ pub enum WizardSubcommands {
#[arg(long)] #[arg(long)]
output: Option<PathBuf>, output: Option<PathBuf>,
}, },
/// Create a 256 bit secret and shard the secret to previously known OpenPGP certificates,
/// deriving the default OpenPGP certificate for the secret.
///
/// This command was purpose-built for DEFCON and is not intended to be used normally, as it
/// implies keys used for sharding have been generated by a custom source.
BottomsUp {
/// The location of OpenPGP certificates to use when sharding.
key_discovery: PathBuf,
/// The minimum amount of keys required to decrypt the secret.
#[arg(long)]
threshold: u8,
/// The file to write the generated shard file to.
#[arg(long)]
output_shardfile: PathBuf,
/// The file to write the generated OpenPGP certificate to.
#[arg(long)]
output_cert: PathBuf,
/// The User ID for the generated OpenPGP certificate.
#[arg(long, default_value = "Disaster Recovery")]
user_id: String,
},
} }
impl WizardSubcommands { impl WizardSubcommands {
@ -220,6 +294,13 @@ impl WizardSubcommands {
keys_per_shard, keys_per_shard,
output, output,
} => generate_shard_secret(*threshold, *max, *keys_per_shard, output), } => generate_shard_secret(*threshold, *max, *keys_per_shard, output),
WizardSubcommands::BottomsUp {
key_discovery,
threshold,
output_shardfile,
output_cert,
user_id,
} => bottoms_up(key_discovery, *threshold, output_shardfile, output_cert, user_id),
} }
} }
} }