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WIP: keyfork-shard: traitify functionality #22

Manually merged
ryan merged 8 commits from keyfork-shard-traitify into main 2024-02-19 10:51:04 +00:00
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534
crates/keyfork-shard/src/openpgp.rs
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@ -1,27 +1,16 @@
//! OpenPGP Shard functionality.
use std::{
collections::{HashMap, VecDeque},
io::{stdin, stdout, Read, Write},
collections::HashMap,
io::{Read, Write},
path::Path,
str::FromStr,
};
use aes_gcm::{
aead::{consts::U12, Aead},
aes::cipher::InvalidLength,
Aes256Gcm, Error as AesError, KeyInit, Nonce,
};
use hkdf::{Hkdf, InvalidLength as HkdfInvalidLength};
use keyfork_derive_openpgp::{
derive_util::{DerivationPath, PathError, VariableLengthSeed},
derive_util::{DerivationPath, VariableLengthSeed},
XPrv,
};
use keyfork_mnemonic_util::{English, Mnemonic, MnemonicFromStrError, MnemonicGenerationError};
use keyfork_prompt::{
validators::{mnemonic::MnemonicSetValidator, Validator},
Error as PromptError, Message as PromptMessage, PromptHandler, Terminal,
};
use openpgp::{
armor::{Kind, Writer},
cert::{Cert, CertParser, ValidCert},
@ -36,12 +25,10 @@ use openpgp::{
Marshal,
},
types::KeyFlags,
Fingerprint, KeyID, PacketPile,
KeyID, PacketPile,
};
pub use sequoia_openpgp as openpgp;
use sha2::Sha256;
use sharks::{Share, Sharks};
use x25519_dalek::{EphemeralSecret, PublicKey};
use sharks::Share;
mod keyring;
use keyring::Keyring;
@ -56,13 +43,7 @@ use smartcard::SmartcardManager;
const SHARD_METADATA_VERSION: u8 = 1;
const SHARD_METADATA_OFFSET: usize = 2;
use super::{
Format, InvalidData, SharksError, HUNK_VERSION, QRCODE_COULDNT_READ, QRCODE_ERROR,
QRCODE_PROMPT, QRCODE_TIMEOUT, KeyDiscovery
};
// 256 bit share is 49 bytes + some amount of hunk bytes, gives us reasonable padding
const ENC_LEN: u8 = 4 * 16;
use super::{Format, KeyDiscovery, SharksError};
/// Errors encountered while performing operations using OpenPGP.
#[derive(Debug, thiserror::Error)]
@ -71,22 +52,6 @@ pub enum Error {
#[error("{0}")]
Sharks(#[from] SharksError),
/// Unable to decrypt a share.
#[error("Error decrypting share: {0}")]
SymDecryptShare(#[from] AesError),
/// The generated AES key is of an invalid length.
#[error("Invalid length of AES key: {0}")]
AesLength(#[from] InvalidLength),
/// The HKDF function was given an input of an invalid length.
#[error("Invalid KDF length: {0}")]
HkdfLength(#[from] HkdfInvalidLength),
/// The secret did not match the previously-known secret fingerprint.
#[error("Derived secret hash {0} != expected {1}")]
InvalidSecret(Fingerprint, Fingerprint),
/// An error occurred while performing an OpenPGP operation.
#[error("OpenPGP error: {0}")]
Sequoia(#[source] anyhow::Error),
@ -103,45 +68,9 @@ pub enum Error {
#[error("Smartcard error: {0}")]
Smartcard(#[from] smartcard::Error),
/// An error occurred while displaying a prompt.
#[error("Prompt error: {0}")]
Prompt(#[from] PromptError),
/// An error occurred while generating a mnemonic.
#[error("Mnemonic generation error: {0}")]
MnemonicGeneration(#[from] MnemonicGenerationError),
/// An error occurred while parsing a mnemonic.
#[error("Mnemonic parse error: {0}")]
MnemonicFromStr(#[from] MnemonicFromStrError),
/// An error occurred while converting mnemonic data.
#[error("{0}")]
InvalidMnemonicData(#[from] InvalidData),
/// An IO error occurred.
#[error("IO error: {0}")]
Io(#[source] std::io::Error),
/// An error occurred while deriving data.
#[error("Derivation: {0}")]
Derivation(#[from] keyfork_derive_openpgp::derive_util::extended_key::private_key::Error),
/// An error occurred while parsing a derivation path.
#[error("Derivation path: {0}")]
DerivationPath(#[from] PathError),
/// An error occurred while requesting derivation.
#[error("Derivation request: {0}")]
DerivationRequest(#[from] keyfork_derive_openpgp::derive_util::request::DerivationError),
/// An error occurred while decoding hex.
#[error("Unable to decode hex: {0}")]
HexDecode(#[from] smex::DecodeError),
/// An error occurred while creating an OpenPGP cert.
#[error("Keyfork OpenPGP: {0}")]
KeyforkOpenPGP(#[from] keyfork_derive_openpgp::Error),
}
#[allow(missing_docs)]
@ -164,6 +93,12 @@ impl EncryptedMessage {
}
/// Parse OpenPGP packets for encrypted messages.
///
/// # Errors
/// The function may return an error if Sequoia is unable to parse packets.
///
/// # Panics
/// The function may panic if an unexpected packet is encountered.
pub fn from_reader(input: impl Read + Send + Sync) -> openpgp::Result<Vec<Self>> {
let mut pkesks = Vec::new();
let mut encrypted_messages = vec![];
@ -225,8 +160,7 @@ impl EncryptedMessage {
H: VerificationHelper + DecryptionHelper,
{
let mut packets = vec![];
self.serialize(&mut packets)
.map_err(Error::Sequoia)?;
self.serialize(&mut packets).map_err(Error::Sequoia)?;
let mut decryptor = DecryptorBuilder::from_bytes(&packets)
.map_err(Error::Sequoia)?
@ -585,68 +519,6 @@ impl KeyDiscovery<OpenPGP> for &[Cert] {
}
}
/// Read all OpenPGP certificates in a path and return a [`Vec`] of them. Certificates are read
/// from a file, or from files one level deep in a directory.
///
/// # Errors
/// The function may return an error if it is unable to read the directory or if Sequoia is unable
/// to load certificates from the file.
#[deprecated]
pub fn discover_certs(path: impl AsRef<Path>) -> Result<Vec<Cert>> {
let path = path.as_ref();
if path.is_file() {
let mut vec = vec![];
for cert in CertParser::from_file(path).map_err(Error::Sequoia)? {
vec.push(cert.map_err(Error::Sequoia)?);
}
Ok(vec)
} else {
let mut vec = vec![];
for entry in path
.read_dir()
.map_err(Error::Io)?
.filter_map(Result::ok)
.filter(|p| p.path().is_file())
{
vec.push(Cert::from_file(entry.path()).map_err(Error::Sequoia)?);
}
Ok(vec)
}
}
/// Parse messages from a type implementing [`Read`] and store them as [`EncryptedMessage`].
///
/// # Errors
/// The function may return an error if the reader has run out of data or if the data is not
/// properly formatted OpenPGP messages.
///
/// # Panics
/// When given packets that are not a list of PKESK packets and SEIP packets, the function panics.
/// The `split` utility should never give packets that are not in this format.
#[deprecated]
pub fn parse_messages(reader: impl Read + Send + Sync) -> Result<VecDeque<EncryptedMessage>> {
let mut pkesks = Vec::new();
let mut encrypted_messages = VecDeque::new();
for packet in PacketPile::from_reader(reader)
.map_err(Error::Sequoia)?
.into_children()
{
match packet {
Packet::PKESK(p) => pkesks.push(p),
Packet::SEIP(s) => {
encrypted_messages.push_back(EncryptedMessage::new(&mut pkesks, s));
}
s => {
panic!("Invalid variant found: {}", s.tag());
}
}
}
Ok(encrypted_messages)
}
fn get_encryption_keys<'a>(
cert: &'a ValidCert,
) -> openpgp::cert::prelude::ValidKeyAmalgamationIter<
@ -795,383 +667,3 @@ fn decrypt_metadata(
message.decrypt_with(policy, keyring)?
})
}
#[deprecated]
fn decrypt_one(
messages: Vec<EncryptedMessage>,
certs: &[Cert],
metadata: &EncryptedMessage,
) -> Result<(Vec<u8>, u8, Cert)> {
let policy = NullPolicy::new();
let mut keyring = Keyring::new(certs)?;
let mut manager = SmartcardManager::new()?;
let content = decrypt_metadata(metadata, &policy, &mut keyring, &mut manager)?;
let (threshold, root_cert, certs) = decode_metadata_v1(&content)?;
keyring.set_root_cert(root_cert.clone());
manager.set_root_cert(root_cert.clone());
let mut messages: HashMap<KeyID, EncryptedMessage> =
certs.iter().map(Cert::keyid).zip(messages).collect();
let decrypted_messages = decrypt_with_keyring(&mut messages, &certs, &policy, &mut keyring)?;
if let Some(message) = decrypted_messages.into_values().next() {
return Ok((message, threshold, root_cert));
}
let decrypted_messages = decrypt_with_manager(1, &mut messages, &certs, &policy, &mut manager)?;
if let Some(message) = decrypted_messages.into_values().next() {
return Ok((message, threshold, root_cert));
}
unreachable!("smartcard manager should always decrypt")
}
/// Decrypt a single shard, encrypt to a remote operator, and present the transport shard as a QR
/// code and mnemonic to be sent to the remote operator.
///
/// # Errors
///
/// The function may error if an error occurs while displaying a prompt or while decrypting the
/// shard. An error will not be returned if the camera has a hardware error while scanning a QR
/// code; instead, a mnemonic prompt will be used.
///
/// # Panics
///
/// The function may panic if a share is decrypted but has a length larger than 256 bits. This is
/// atypical usage and should not be encountered in normal usage, unless something that is not a
/// Keyfork seed has been fed into [`split`].
#[deprecated]
#[allow(deprecated)]
pub fn decrypt(
certs: &[Cert],
metadata: &EncryptedMessage,
encrypted_messages: &[EncryptedMessage],
) -> Result<()> {
let mut pm = Terminal::new(stdin(), stdout())?;
let mut nonce_data: Option<[u8; 12]> = None;
let mut pubkey_data: Option<[u8; 32]> = None;
#[cfg(feature = "qrcode")]
{
pm.prompt_message(PromptMessage::Text(QRCODE_PROMPT.to_string()))?;
if let Ok(Some(hex)) =
keyfork_qrcode::scan_camera(std::time::Duration::from_secs(QRCODE_TIMEOUT), 0)
{
let decoded_data = smex::decode(&hex)?;
let _ = nonce_data.insert(decoded_data[..12].try_into().map_err(|_| InvalidData)?);
let _ = pubkey_data.insert(decoded_data[12..].try_into().map_err(|_| InvalidData)?);
} else {
pm.prompt_message(PromptMessage::Text(QRCODE_ERROR.to_string()))?;
};
}
let (nonce, pubkey) = match (nonce_data, pubkey_data) {
(Some(nonce), Some(pubkey)) => (nonce, pubkey),
_ => {
let validator = MnemonicSetValidator {
word_lengths: [9, 24],
};
let [nonce_mnemonic, pubkey_mnemonic] = pm.prompt_validated_wordlist::<English, _>(
QRCODE_COULDNT_READ,
3,
validator.to_fn(),
)?;
let nonce = nonce_mnemonic
.as_bytes()
.try_into()
.map_err(|_| InvalidData)?;
let pubkey = pubkey_mnemonic
.as_bytes()
.try_into()
.map_err(|_| InvalidData)?;
(nonce, pubkey)
}
};
let nonce = Nonce::<U12>::from_slice(&nonce);
let our_key = EphemeralSecret::random();
let our_pubkey_mnemonic = Mnemonic::from_bytes(PublicKey::from(&our_key).as_bytes())?;
let shared_secret = our_key.diffie_hellman(&PublicKey::from(pubkey)).to_bytes();
let (mut share, threshold, ..) = decrypt_one(encrypted_messages.to_vec(), certs, metadata)?;
share.insert(0, HUNK_VERSION);
share.insert(1, threshold);
assert!(
share.len() <= ENC_LEN as usize,
"invalid share length (too long, max {ENC_LEN} bytes)"
);
let hkdf = Hkdf::<Sha256>::new(None, &shared_secret);
let mut hkdf_output = [0u8; 256 / 8];
hkdf.expand(&[], &mut hkdf_output)?;
let shared_key = Aes256Gcm::new_from_slice(&hkdf_output)?;
let bytes = shared_key.encrypt(nonce, share.as_slice())?;
shared_key.decrypt(nonce, &bytes[..])?;
// NOTE: Padding length is less than u8::MAX because ENC_LEN < u8::MAX
// NOTE: This previously used a single value as the padding byte, but resulted in
// difficulty when entering in prompts manually, as one's place could be lost due to repeated
// keywords. This is done below by having sequentially increasing numbers up to but not
// including the last byte.
#[allow(clippy::assertions_on_constants)]
{
assert!(ENC_LEN < u8::MAX, "padding byte can be u8");
}
#[allow(clippy::cast_possible_truncation)]
let mut out_bytes = [bytes.len() as u8; ENC_LEN as usize];
assert!(
bytes.len() < out_bytes.len(),
"encrypted payload larger than acceptable limit"
);
out_bytes[..bytes.len()].clone_from_slice(&bytes);
#[allow(clippy::cast_possible_truncation)]
for (i, byte) in (out_bytes[bytes.len()..(ENC_LEN as usize - 1)])
.iter_mut()
.enumerate()
{
*byte = (i % u8::MAX as usize) as u8;
}
// safety: size of out_bytes is constant and always % 4 == 0
let payload_mnemonic = unsafe { Mnemonic::from_raw_bytes(&out_bytes) };
#[cfg(feature = "qrcode")]
{
use keyfork_qrcode::{qrencode, ErrorCorrection};
let mut qrcode_data = our_pubkey_mnemonic.to_bytes();
qrcode_data.extend(payload_mnemonic.as_bytes());
if let Ok(qrcode) = qrencode(&smex::encode(&qrcode_data), ErrorCorrection::Highest) {
pm.prompt_message(PromptMessage::Text(
concat!(
"A QR code will be displayed after this prompt. ",
"Send the QR code back to the operator combining the shards. ",
"Nobody else should scan this QR code."
)
.to_string(),
))?;
pm.prompt_message(PromptMessage::Data(qrcode))?;
}
}
pm.prompt_message(PromptMessage::Text(format!(
"Upon request, these words should be sent: {our_pubkey_mnemonic} {payload_mnemonic}"
)))?;
Ok(())
}
/// Combine mulitple shards into a secret.
///
/// # Errors
/// The function may return an error if an error occurs while decrypting shards, parsing shards, or
/// combining the shards into a secret.
#[deprecated]
pub fn combine(
certs: Vec<Cert>,
metadata: &EncryptedMessage,
messages: Vec<EncryptedMessage>,
mut output: impl Write,
) -> Result<()> {
// Be as liberal as possible when decrypting.
// We don't want to invalidate someone's keys just because the old sig expired.
let policy = NullPolicy::new();
let mut keyring = Keyring::new(certs)?;
let mut manager = SmartcardManager::new()?;
let content = decrypt_metadata(metadata, &policy, &mut keyring, &mut manager)?;
let (threshold, root_cert, certs) = decode_metadata_v1(&content)?;
keyring.set_root_cert(root_cert.clone());
manager.set_root_cert(root_cert.clone());
// Generate a controlled binding from certificates to encrypted messages. This is stable
// because we control the order packets are encrypted and certificates are stored.
let mut messages: HashMap<KeyID, EncryptedMessage> =
certs.iter().map(Cert::keyid).zip(messages).collect();
let mut decrypted_messages =
decrypt_with_keyring(&mut messages, &certs, &policy, &mut keyring)?;
// clean decrypted messages from encrypted messages
messages.retain(|k, _v| !decrypted_messages.contains_key(k));
let left_from_threshold = threshold as usize - decrypted_messages.len();
if left_from_threshold > 0 {
#[allow(clippy::cast_possible_truncation)]
let new_messages = decrypt_with_manager(
left_from_threshold as u8,
&mut messages,
&certs,
&policy,
&mut manager,
)?;
decrypted_messages.extend(new_messages);
}
let shares = decrypted_messages
.values()
.map(|message| Share::try_from(message.as_slice()))
.collect::<Result<Vec<_>, &str>>()
.map_err(|e| SharksError::Share(e.to_string()))?;
let secret = Sharks(threshold)
.recover(&shares)
.map_err(|e| SharksError::CombineShare(e.to_string()))?;
// TODO: extract as function
let userid = UserID::from("keyfork-sss");
let path = DerivationPath::from_str("m/7366512'/0'")?;
let seed = VariableLengthSeed::new(&secret);
let xprv = XPrv::new(seed).derive_path(&path)?;
let derived_cert = keyfork_derive_openpgp::derive(
xprv,
&[KeyFlags::empty().set_certification().set_signing()],
&userid,
)?;
// NOTE: Signatures on certs will be different. Compare fingerprints instead.
let derived_fp = derived_cert.fingerprint();
let expected_fp = root_cert.fingerprint();
if derived_fp != expected_fp {
return Err(Error::InvalidSecret(derived_fp, expected_fp));
}
output.write_all(&secret).map_err(Error::Io)?;
Ok(())
}
/// Split a secret into an OpenPGP formatted Shard file.
///
/// # Errors
///
/// The function may return an error if the shards can't be encrypted to the provided OpenPGP
/// certs or if an error happens while writing the Shard file.
///
/// # Panics
///
/// The function may panic if the metadata can't properly store the certificates used to generate
/// the encrypted shares.
#[deprecated]
pub fn split(threshold: u8, certs: Vec<Cert>, secret: &[u8], output: impl Write) -> Result<()> {
let seed = VariableLengthSeed::new(secret);
// build cert to sign encrypted shares
let userid = UserID::from("keyfork-sss");
let path = DerivationPath::from_str("m/7366512'/0'")?;
let xprv = XPrv::new(seed).derive_path(&path)?;
let derived_cert = keyfork_derive_openpgp::derive(
xprv,
&[KeyFlags::empty().set_certification().set_signing()],
&userid,
)?;
let signing_key = derived_cert
.primary_key()
.parts_into_secret()
.map_err(Error::Sequoia)?
.key()
.clone()
.into_keypair()
.map_err(Error::Sequoia)?;
let sharks = Sharks(threshold);
let dealer = sharks.dealer(secret);
let generated_shares = dealer.map(|s| Vec::from(&s)).collect::<Vec<_>>();
let policy = StandardPolicy::new();
let mut writer = Writer::new(output, Kind::Message).map_err(Error::SequoiaIo)?;
let mut total_recipients = vec![];
let mut messages = vec![];
for (share, cert) in generated_shares.iter().zip(certs) {
total_recipients.push(cert.clone());
let valid_cert = cert.with_policy(&policy, None).map_err(Error::Sequoia)?;
let encryption_keys = get_encryption_keys(&valid_cert).collect::<Vec<_>>();
let mut message_output = vec![];
let message = Message::new(&mut message_output);
let message = Encryptor2::for_recipients(
message,
encryption_keys
.iter()
.map(|k| Recipient::new(KeyID::wildcard(), k.key())),
)
.build()
.map_err(Error::Sequoia)?;
let message = Signer::new(message, signing_key.clone())
.build()
.map_err(Error::Sequoia)?;
let mut message = LiteralWriter::new(message)
.build()
.map_err(Error::Sequoia)?;
message.write_all(share).map_err(Error::SequoiaIo)?;
message.finalize().map_err(Error::Sequoia)?;
messages.push(message_output);
}
let mut pp = vec![SHARD_METADATA_VERSION, threshold];
// store derived cert to verify provided shares
derived_cert.serialize(&mut pp).map_err(Error::Sequoia)?;
for recipient in &total_recipients {
recipient.serialize(&mut pp).map_err(Error::Sequoia)?;
}
// verify packet pile
for (packet_cert, cert) in openpgp::cert::CertParser::from_bytes(&pp[2..])
.map_err(Error::Sequoia)?
.skip(1)
.zip(total_recipients.iter())
{
assert_eq!(
&packet_cert.map_err(Error::Sequoia)?,
cert,
"packet pile could not recreate cert: {}",
cert.fingerprint()
);
}
let valid_certs = total_recipients
.iter()
.map(|c| c.with_policy(&policy, None))
.collect::<openpgp::Result<Vec<_>>>()
.map_err(Error::Sequoia)?;
let total_recipients = valid_certs.iter().flat_map(|vc| {
get_encryption_keys(vc).map(|key| Recipient::new(KeyID::wildcard(), key.key()))
});
// metadata
let mut message_output = vec![];
let message = Message::new(&mut message_output);
let message = Encryptor2::for_recipients(message, total_recipients)
.build()
.map_err(Error::Sequoia)?;
let mut message = LiteralWriter::new(message)
.build()
.map_err(Error::Sequoia)?;
message.write_all(&pp).map_err(Error::SequoiaIo)?;
message.finalize().map_err(Error::Sequoia)?;
writer
.write_all(&message_output)
.map_err(Error::SequoiaIo)?;
for message in messages {
writer.write_all(&message).map_err(Error::SequoiaIo)?;
}
writer.finalize().map_err(Error::SequoiaIo)?;
Ok(())
}