keyfork: add `bottoms-up` wizard

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

@@ -83,7 +83,7 @@ fn validate(
     let index = DerivationIndex::new(u32::from_be_bytes(pgp_u32), true)?;
 
     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");
     assert_eq!(

crates/keyfork/src/cli/wizard.rs

@@ -1,20 +1,26 @@
 use super::Keyfork;
 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 openpgp_card_sequoia::{state::Open, types::KeyType, Card};
 
 use keyfork_derive_openpgp::{
-    openpgp::{self, packet::UserID, types::KeyFlags, Cert},
+    openpgp::{self, packet::UserID, types::KeyFlags, Cert, serialize::Marshal, armor::{Writer, Kind}},
     XPrv,
 };
-use keyfork_derive_util::{DerivationIndex, DerivationPath};
+use keyfork_derive_util::{DerivationIndex, DerivationPath, VariableLengthSeed};
 use keyfork_prompt::{
     default_terminal,
     validators::{SecurePinValidator, Validator},
     DefaultTerminal, Message, PromptHandler,
 };
+use keyfork_mnemonic_util::Mnemonic;
 
 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>;
 
+// 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> {
     let subkeys = vec![
         KeyFlags::empty().set_certification(),
@@ -185,6 +193,46 @@ fn generate_shard_secret(
     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)]
 pub enum WizardSubcommands {
     /// Create a 256 bit secret and shard the secret to smart cards.
@@ -209,6 +257,32 @@ pub enum WizardSubcommands {
         #[arg(long)]
         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 {
@@ -220,6 +294,13 @@ impl WizardSubcommands {
                 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),
         }
     }
 }