Cargo.lock

@@ -1681,6 +1681,7 @@ dependencies = [
  "clap_complete",
  "keyfork-bin",
  "keyfork-derive-openpgp",
+ "keyfork-derive-path-data",
  "keyfork-derive-util",
  "keyfork-entropy",
  "keyfork-mnemonic",
@@ -1748,6 +1749,7 @@ version = "0.1.2"
 dependencies = [
  "anyhow",
  "ed25519-dalek",
+ "keyfork-derive-path-data",
  "keyfork-derive-util",
  "keyforkd-client",
  "sequoia-openpgp",
@@ -1759,6 +1761,7 @@ name = "keyfork-derive-path-data"
 version = "0.1.1"
 dependencies = [
  "keyfork-derive-util",
+ "once_cell",
 ]
 
 [[package]]

crates/derive/keyfork-derive-openpgp/Cargo.toml

@@ -16,3 +16,4 @@ ed25519-dalek = "2.0.0"
 sequoia-openpgp = { version = "1.17.0", default-features = false }
 anyhow = "1.0.75"
 thiserror = "1.0.49"
+keyfork-derive-path-data = { version = "0.1.1", path = "../keyfork-derive-path-data" }

crates/derive/keyfork-derive-openpgp/src/main.rs

@@ -3,6 +3,7 @@
 use std::{env, process::ExitCode, str::FromStr};
 
 use keyfork_derive_util::{DerivationIndex, DerivationPath};
+use keyfork_derive_path_data::paths;
 use keyforkd_client::Client;
 
 use ed25519_dalek::SigningKey;
@@ -78,16 +79,14 @@ fn validate(
     subkey_format: &str,
     default_userid: &str,
 ) -> Result<(DerivationPath, Vec<KeyType>, UserID), Box<dyn std::error::Error>> {
-    let mut pgp_u32 = [0u8; 4];
-    pgp_u32[1..].copy_from_slice(&"pgp".bytes().collect::<Vec<u8>>());
-    let index = DerivationIndex::new(u32::from_be_bytes(pgp_u32), true)?;
+    let index = paths::OPENPGP.inner().first().unwrap();
 
     let path = DerivationPath::from_str(path)?;
     assert!(path.len() >= 2, "Expected path of at least m/{index}/account_id'");
 
     let given_index = path.iter().next().expect("checked .len() above");
     assert_eq!(
-        &index, given_index,
+        index, given_index,
         "Expected derivation path starting with m/{index}, got: {given_index}",
     );
 

crates/derive/keyfork-derive-path-data/Cargo.toml

@@ -8,3 +8,4 @@ license = "MIT"
 
 [dependencies]
 keyfork-derive-util = { version = "0.2.0", path = "../keyfork-derive-util", default-features = false, registry = "distrust" }
+once_cell = "1.19.0"

crates/derive/keyfork-derive-path-data/src/lib.rs

@@ -2,32 +2,128 @@
 
 #![allow(clippy::unreadable_literal)]
 
+use once_cell::sync::Lazy;
+
 use keyfork_derive_util::{DerivationIndex, DerivationPath};
 
-/// The default derivation path for OpenPGP.
-pub static OPENPGP: DerivationIndex = DerivationIndex::new_unchecked(7366512, true);
+pub mod paths {
+    use super::*;
+
+    /// The default derivation path for OpenPGP.
+    pub static OPENPGP: Lazy<DerivationPath> = Lazy::new(|| {
+        DerivationPath::default().chain_push(DerivationIndex::new_unchecked(
+            u32::from_be_bytes(*b"\x00pgp"),
+            true,
+        ))
+    });
+
+    /// The derivation path for OpenPGP certificates used for sharding.
+    pub static OPENPGP_SHARD: Lazy<DerivationPath> = Lazy::new(|| {
+        DerivationPath::default()
+            .chain_push(DerivationIndex::new_unchecked(
+                u32::from_be_bytes(*b"\x00pgp"),
+                true,
+            ))
+            .chain_push(DerivationIndex::new_unchecked(
+                u32::from_be_bytes(*b"shrd"),
+                true,
+            ))
+    });
+
+    /// The derivation path for OpenPGP certificates used for disaster recovery.
+    pub static OPENPGP_DISASTER_RECOVERY: Lazy<DerivationPath> = Lazy::new(|| {
+        DerivationPath::default()
+            .chain_push(DerivationIndex::new_unchecked(
+                u32::from_be_bytes(*b"\x00pgp"),
+                true,
+            ))
+            .chain_push(DerivationIndex::new_unchecked(
+                u32::from_be_bytes(*b"\x00\x00dr"),
+                true,
+            ))
+    });
+}
+
+/// Determine if a prefix matches and whether the next index exists.
+fn prefix_matches(given: &DerivationPath, target: &DerivationPath) -> Option<DerivationIndex> {
+    if given.len() <= target.len() {
+        return None;
+    }
+    if target
+        .iter()
+        .zip(given.iter())
+        .all(|(left, right)| left == right)
+    {
+        given.iter().nth(target.len()).cloned()
+    } else {
+        None
+    }
+}
 
 /// A derivation target.
+#[derive(Debug)]
+#[non_exhaustive]
 pub enum Target {
     /// An OpenPGP key, whose account is the given index.
     OpenPGP(DerivationIndex),
+
+    /// An OpenPGP key used for sharding.
+    OpenPGPShard(DerivationIndex),
+
+    /// An OpenPGP key used for disaster recovery.
+    OpenPGPDisasterRecovery(DerivationIndex),
 }
 
 impl std::fmt::Display for Target {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         match self {
-            Self::OpenPGP(account) => {
+            Target::OpenPGP(account) => {
                 write!(f, "OpenPGP key (account {account})")
             }
+            Target::OpenPGPShard(shard_index) => {
+                write!(f, "OpenPGP Shard key (shard index {shard_index})")
+            }
+            Target::OpenPGPDisasterRecovery(account) => {
+                write!(f, "OpenPGP Disaster Recovery key (account {account})")
+            }
         }
     }
 }
 
+macro_rules! test_match {
+    ($var:ident, $shard:path, $target:path) => {
+        if let Some(index) = prefix_matches($var, &$shard) {
+            return Some($target(index));
+        }
+    };
+}
+
 /// Determine the closest [`Target`] for the given path. This method is intended to be used by
 /// `keyforkd` to provide an optional textual prompt to what a client is attempting to derive.
 pub fn guess_target(path: &DerivationPath) -> Option<Target> {
-    Some(match path.iter().collect::<Vec<_>>()[..] {
-        [t, index] if t == &OPENPGP => Target::OpenPGP(index.clone()),
-        _ => return None,
-    })
+    test_match!(path, paths::OPENPGP_SHARD, Target::OpenPGPShard);
+    test_match!(
+        path,
+        paths::OPENPGP_DISASTER_RECOVERY,
+        Target::OpenPGPDisasterRecovery
+    );
+    test_match!(path, paths::OPENPGP, Target::OpenPGP);
+    None
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn it_works() {
+        let index = DerivationIndex::new(5312, false).unwrap();
+        let dr_key = paths::OPENPGP_DISASTER_RECOVERY
+            .clone()
+            .chain_push(index.clone());
+        match guess_target(&dr_key) {
+            Some(Target::OpenPGPDisasterRecovery(idx)) if idx == index => (),
+            bad => panic!("invalid value: {bad:?}"),
+        }
+    }
 }

crates/keyfork/Cargo.toml

@@ -44,3 +44,4 @@ openpgp-card-sequoia = { version = "0.2.0", default-features = false }
 openpgp-card = "0.4.1"
 clap_complete = { version = "4.4.6", optional = true }
 sequoia-openpgp = { version = "1.17.0", default-features = false, features = ["compression"] }
+keyfork-derive-path-data = { version = "0.1.1", path = "../derive/keyfork-derive-path-data" }

crates/keyfork/src/cli/derive.rs

@@ -11,6 +11,7 @@ use keyfork_derive_openpgp::{
     XPrvKey,
 };
 use keyfork_derive_util::{DerivationIndex, DerivationPath};
+use keyfork_derive_path_data::paths;
 use keyforkd_client::Client;
 
 type Result<T, E = Box<dyn std::error::Error>> = std::result::Result<T, E>;
@@ -37,12 +38,7 @@ impl DeriveSubcommands {
     fn handle(&self, account: DerivationIndex) -> Result<()> {
         match self {
             DeriveSubcommands::OpenPGP { user_id } => {
-                let mut pgp_u32 = [0u8; 4];
-                pgp_u32[1..].copy_from_slice(&"pgp".bytes().collect::<Vec<u8>>());
-                let chain = DerivationIndex::new(u32::from_be_bytes(pgp_u32), true)?;
-                let path = DerivationPath::default()
-                    .chain_push(chain)
-                    .chain_push(account);
+                let path = paths::OPENPGP.clone().chain_push(account);
                 // TODO: should this be customizable?
                 let subkeys = vec![
                     KeyFlags::empty().set_certification(),

crates/keyfork/src/cli/wizard.rs

@@ -11,16 +11,24 @@ use card_backend_pcsc::PcscBackend;
 use openpgp_card_sequoia::{state::Open, types::KeyType, Card};
 
 use keyfork_derive_openpgp::{
-    openpgp::{self, packet::UserID, types::KeyFlags, Cert, serialize::Marshal, armor::{Writer, Kind}},
+    openpgp::{
+        self,
+        armor::{Kind, Writer},
+        packet::UserID,
+        serialize::Marshal,
+        types::KeyFlags,
+        Cert,
+    },
     XPrv,
 };
+use keyfork_derive_path_data::paths;
 use keyfork_derive_util::{DerivationIndex, DerivationPath};
+use keyfork_mnemonic::Mnemonic;
 use keyfork_prompt::{
     default_terminal,
     validators::{SecurePinValidator, Validator},
     DefaultTerminal, Message, PromptHandler,
 };
-use keyfork_mnemonic::Mnemonic;
 
 use keyfork_shard::{openpgp::OpenPGP, Format};
 
@@ -42,17 +50,8 @@ fn derive_key(seed: [u8; 32], index: u8) -> Result<Cert> {
         KeyFlags::empty().set_authentication(),
     ];
 
-    let mut pgp_u32 = [0u8; 4];
-    pgp_u32[1..].copy_from_slice(&"pgp".bytes().collect::<Vec<u8>>());
-    let chain = DerivationIndex::new(u32::from_be_bytes(pgp_u32), true)?;
-    let mut shrd_u32 = [0u8; 4];
-    shrd_u32[..].copy_from_slice(&"shrd".bytes().collect::<Vec<u8>>());
-    let account = DerivationIndex::new(u32::from_be_bytes(shrd_u32), true)?;
     let subkey = DerivationIndex::new(u32::from(index), true)?;
-    let path = DerivationPath::default()
-        .chain_push(chain)
-        .chain_push(account)
-        .chain_push(subkey);
+    let path = paths::OPENPGP_SHARD.clone().chain_push(subkey);
     let xprv = XPrv::new(seed)
         .expect("could not construct master key from seed")
         .derive_path(&path)?;
@@ -193,16 +192,21 @@ fn generate_shard_secret(
     Ok(())
 }
 
-fn bottoms_up(key_discovery: &Path, threshold: u8, output_shardfile: &Path, output_cert: &Path, user_id: &str,) -> Result<()> {
+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_array(entropy);
     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)?)
+    let path = paths::OPENPGP_DISASTER_RECOVERY
+        .clone()
         .chain_push(DerivationIndex::new(0, true)?);
     let subkeys = [
         KeyFlags::empty().set_certification(),
@@ -227,7 +231,13 @@ fn bottoms_up(key_discovery: &Path, threshold: u8, output_shardfile: &Path, outp
     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)?;
+    opgp.shard_and_encrypt(
+        threshold,
+        certs.len() as u8,
+        &entropy,
+        &certs[..],
+        shardfile,
+    )?;
 
     Ok(())
 }
@@ -299,7 +309,13 @@ impl WizardSubcommands {
                 output_shardfile,
                 output_cert,
                 user_id,
-            } => bottoms_up(key_discovery, *threshold, output_shardfile, output_cert, user_id),
+            } => bottoms_up(
+                key_discovery,
+                *threshold,
+                output_shardfile,
+                output_cert,
+                user_id,
+            ),
         }
     }
 }