keyfork-shard: enable step 1 decoding with openpgp-card, fix bug with multiple smartcards when decrypting

keyfork-shard/src/bin/keyfork-shard-combine-openpgp.rs

@@ -25,8 +25,8 @@ fn validate(
     // Load certs from path
     let certs = discover_certs(key_discovery)?;
 
-    let recovery_file = PathBuf::from(if recovery_file == "=" {
+    let recovery_file = PathBuf::from(if recovery_file == "-" {
-        eprintln!("loading certs from stdin; note that prompting smartcard devices will not work");
+        eprintln!("loading certs from stdin; note that prompting smartcard PINs will not work");
         "/dev/stdin"
     } else {
         recovery_file

keyfork-shard/src/openpgp.rs

@@ -177,7 +177,14 @@ pub fn combine(
     let policy = NullPolicy::new();
 
     let mut keyring = Keyring::new(certs);
-    let content = metadata.decrypt_with(&policy, &mut keyring)?;
+    let mut manager = SmartcardManager::new();
+    let content = if keyring.is_empty() {
+        let card_fp = manager.load_any_card()?;
+        eprintln!("key discovery is empty, using hardware smartcard: {card_fp}");
+        metadata.decrypt_with(&policy, &mut manager)?
+    } else {
+        metadata.decrypt_with(&policy, &mut keyring)?
+    };
 
     let mut cert_parser = CertParser::from_bytes(&content)?;
     let root_cert = match cert_parser.next() {
@@ -186,7 +193,8 @@ pub fn combine(
         None => panic!("No certs found in cert parser"),
     };
     let certs = cert_parser.collect::<openpgp::Result<Vec<_>>>()?;
-    keyring.set_root_cert(root_cert);
+    keyring.set_root_cert(root_cert.clone());
+    manager.set_root_cert(root_cert);
     let mut messages: HashMap<KeyID, EncryptedMessage> =
         HashMap::from_iter(certs.iter().map(|c| c.keyid()).zip(messages));
     let mut decrypted_messages: HashMap<KeyID, Vec<u8>> = HashMap::new();
@@ -231,9 +239,6 @@ pub fn combine(
     let left_from_threshold = threshold as usize - decrypted_messages.len();
     if left_from_threshold > 0 {
         eprintln!("remaining keys: {left_from_threshold}, prompting yubikeys");
-        // TODO: allow decrypt metadata with Yubikey, avoid require stage 1
-        let mut manager =
-            SmartcardManager::new(keyring.root_cert().expect("stage 1 decrypt").clone());
         let mut remaining_usable_certs = certs
             .iter()
             .filter(|cert| messages.contains_key(&cert.keyid()))
@@ -241,29 +246,33 @@ pub fn combine(
 
         while threshold as usize - decrypted_messages.len() > 0 {
             remaining_usable_certs.retain(|cert| messages.contains_key(&cert.keyid()));
-            let mut fingerprints = HashMap::new();
+            let mut key_by_fingerprints = HashMap::new();
+            let mut total_fingerprints = vec![];
             for valid_cert in remaining_usable_certs
                 .iter()
                 .map(|cert| cert.with_policy(&policy, None))
             {
                 let valid_cert = valid_cert?;
-                fingerprints.insert(
+                let fp = valid_cert
-                    valid_cert.keyid(),
-                    valid_cert
                     .keys()
                     .for_storage_encryption()
                     .map(|k| k.fingerprint())
-                        .collect::<Vec<_>>(),
+                    .collect::<Vec<_>>();
-                );
+                for fp in &fp {
+                    key_by_fingerprints.insert(fp.clone(), valid_cert.keyid());
                 }
-            for (cert_id, fingerprints) in fingerprints {
+                total_fingerprints.extend(fp.iter().cloned());
-                if manager.load_any_fingerprint(fingerprints)?.is_some() {
+            }
-                    // manager is loaded with a Card<Open>, utilize in tx
+
-                    let message = messages.remove(&cert_id);
+            // Iterate over all fingerprints and use key_by_fingerprints to assoc with Enc. Message
+            if let Some(fp) = manager.load_any_fingerprint(total_fingerprints)? {
+                // soundness: `key_by_fingerprints` is extended by the same fps that are then
+                // inserted into `total_fingerprints`
+                let cert_keyid = key_by_fingerprints.get(&fp).unwrap().clone();
+                let message = messages.remove(&cert_keyid);
                 if let Some(message) = message {
                     let message = message.decrypt_with(&policy, &mut manager)?;
-                        decrypted_messages.insert(cert_id, message);
+                    decrypted_messages.insert(cert_keyid, message);
-                    }
                 }
             }
         }

keyfork-shard/src/openpgp/keyring.rs

@@ -40,6 +40,10 @@ impl Keyring {
         }
     }
 
+    pub fn is_empty(&self) -> bool {
+        self.full_certs.is_empty()
+    }
+
     // Sets the root cert, returning the old cert
     pub fn set_root_cert(&mut self, cert: impl Into<Option<Cert>>) -> Option<Cert> {
         let mut cert = cert.into();

keyfork-shard/src/openpgp/smartcard.rs

@@ -13,34 +13,37 @@ use openpgp_card_sequoia::{state::Open, Card};
 
 #[derive(Clone, Debug)]
 pub enum SmartcardFailure {
-    #[allow(dead_code)]
-    SmartCardPromptFailed,
-
     SmartCardNotFound,
+    SmartCardHasNoDecrypt,
 }
 
 impl std::fmt::Display for SmartcardFailure {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         match self {
-            Self::SmartCardPromptFailed => f.write_str("Attempt to prompt for smart card failed"),
             Self::SmartCardNotFound => f.write_str("No smart card backend was stored"),
+            Self::SmartCardHasNoDecrypt => f.write_str("Selected smart card has no decrypt key"),
         }
     }
 }
 
 impl std::error::Error for SmartcardFailure {}
 
+#[derive(Default)]
 pub struct SmartcardManager {
     current_card: Option<Card<Open>>,
-    root: Cert,
+    root: Option<Cert>,
 }
 
 impl SmartcardManager {
-    pub fn new(root: Cert) -> Self {
+    pub fn new() -> Self {
-        Self {
+        Default::default()
-            current_card: None,
-            root,
     }
+
+    // Sets the root cert, returning the old cert
+    pub fn set_root_cert(&mut self, cert: impl Into<Option<Cert>>) -> Option<Cert> {
+        let mut cert = cert.into();
+        std::mem::swap(&mut self.root, &mut cert);
+        cert
     }
 
     /// Utility function to prompt for a newline from standard input.
@@ -57,6 +60,7 @@ impl SmartcardManager {
         Ok(output)
     }
 
+    /*
     /// Return all [`Fingerprint`] for the currently accessible backends.
     ///
     /// NOTE: Only implemented for decryption keys.
@@ -74,6 +78,29 @@ impl SmartcardManager {
             })
         })
     }
+    */
+
+    /// Load any backend.
+    pub fn load_any_card(&mut self) -> Result<Fingerprint, Box<dyn std::error::Error>> {
+        PcscBackend::cards(None)?
+            .next()
+            .transpose()?
+            .ok_or(SmartcardFailure::SmartCardNotFound.into())
+            .and_then(
+                |backend| -> Result<Fingerprint, Box<dyn std::error::Error>> {
+                    let mut card = Card::<Open>::new(backend)?;
+                    let transaction = card.transaction()?;
+                    let fingerprint = transaction
+                        .fingerprints()?
+                        .decryption()
+                        .map(|fp| Fingerprint::from_bytes(fp.as_bytes()))
+                        .ok_or(SmartcardFailure::SmartCardHasNoDecrypt)?;
+                    drop(transaction);
+                    self.current_card.replace(card);
+                    Ok(fingerprint)
+                },
+            )
+    }
 
     /// Load a backend if any [`Fingerprint`] has been matched by a currently active card.
     ///
@@ -125,13 +152,8 @@ impl VerificationHelper for &mut SmartcardManager {
     fn get_certs(&mut self, ids: &[openpgp::KeyHandle]) -> openpgp::Result<Vec<Cert>> {
         Ok(ids
             .iter()
-            .flat_map(|kh| {
+            .flat_map(|kh| self.root.as_ref().filter(|cert| cert.key_handle() == *kh))
-                if &self.root.key_handle() == kh {
+            .cloned()
-                    Some(self.root.clone())
-                } else {
-                    None
-                }
-            })
             .collect())
     }