keyfork-shard: add in bug messages

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

@@ -65,7 +65,7 @@ pub type Result<T, E = Error> = std::result::Result<T, E>;
 /// # Errors
 /// The function may error for any condition mentioned in [`Error`].
 pub fn derive(xprv: XPrv, keys: &[KeyFlags], userid: &UserID) -> Result<Cert> {
-    let primary_key_flags = match keys.get(0) {
+    let primary_key_flags = match keys.first() {
         Some(kf) if kf.for_certification() => kf,
         _ => return Err(Error::NotCert),
     };

crates/derive/keyfork-derive-util/src/private_key.rs

@@ -102,6 +102,10 @@ pub enum PrivateKeyError {
     /// For the given algorithm, the private key must be nonzero.
     #[error("The provided private key must be nonzero, but is not")]
     NonZero,
+
+    /// A scalar could not be constructed for the given algorithm.
+    #[error("A scalar could not be constructed for the given algorithm")]
+    InvalidScalar,
 }
 
 #[cfg(feature = "secp256k1")]
@@ -130,20 +134,19 @@ impl PrivateKey for k256::SecretKey {
     }
 
     fn derive_child(&self, other: &PrivateKeyBytes) -> Result<Self, Self::Err> {
-        if other.iter().all(|n| n == &0) {
-            return Err(PrivateKeyError::NonZero);
-        }
-        let other = *other;
-        // Checked: See above nonzero check
-        let scalar = Option::<NonZeroScalar>::from(NonZeroScalar::from_repr(other.into()))
-            .expect(bug!("Should have been able to get a NonZeroScalar"));
+        use k256::elliptic_curve::ScalarPrimitive;
+        use k256::{Scalar, Secp256k1};
+
+        // Construct a scalar from bytes
+        let scalar = ScalarPrimitive::<Secp256k1>::from_bytes(other.into());
+        let scalar = Option::<ScalarPrimitive<Secp256k1>>::from(scalar);
+        let scalar = scalar.ok_or(PrivateKeyError::InvalidScalar)?;
+        let scalar = Scalar::from(scalar);
 
         let derived_scalar = self.to_nonzero_scalar().as_ref() + scalar.as_ref();
-        Ok(
-            Option::<NonZeroScalar>::from(NonZeroScalar::new(derived_scalar))
-                .map(Into::into)
-                .expect(bug!("Should be able to make Key")),
-        )
+        let nonzero_scalar = Option::<NonZeroScalar>::from(NonZeroScalar::new(derived_scalar))
+            .ok_or(PrivateKeyError::NonZero)?;
+        Ok(Self::from(nonzero_scalar))
     }
 }
 
@@ -202,9 +205,7 @@ impl PrivateKey for TestPrivateKey {
     type Err = PrivateKeyError;
 
     fn from_bytes(b: &PrivateKeyBytes) -> Self {
-        Self {
-            key: *b
-        }
+        Self { key: *b }
     }
 
     fn to_bytes(&self) -> PrivateKeyBytes {

crates/derive/keyfork-derive-util/src/public_key.rs

@@ -77,6 +77,10 @@ pub enum PublicKeyError {
     #[error("The provided public key must be nonzero, but is not")]
     NonZero,
 
+    /// A scalar could not be constructed for the given algorithm.
+    #[error("A scalar could not be constructed for the given algorithm")]
+    InvalidScalar,
+
     /// Public key derivation is unsupported for this algorithm.
     #[error("Public key derivation is unsupported for this algorithm")]
     DerivationUnsupported,
@@ -85,7 +89,7 @@ pub enum PublicKeyError {
 #[cfg(feature = "secp256k1")]
 use k256::{
     elliptic_curve::{group::prime::PrimeCurveAffine, sec1::ToEncodedPoint},
-    AffinePoint, NonZeroScalar,
+    AffinePoint,
 };
 
 #[cfg(feature = "secp256k1")]
@@ -105,14 +109,16 @@ impl PublicKey for k256::PublicKey {
     }
 
     fn derive_child(&self, other: PrivateKeyBytes) -> Result<Self, Self::Err> {
-        if other.iter().all(|n| n == &0) {
-            return Err(PublicKeyError::NonZero);
-        }
-        // Checked: See above
-        let scalar = Option::<NonZeroScalar>::from(NonZeroScalar::from_repr(other.into()))
-            .expect(bug!("Should have been able to get a NonZeroScalar"));
+        use k256::elliptic_curve::ScalarPrimitive;
+        use k256::{Secp256k1, Scalar};
 
-        let point = self.to_projective() + (AffinePoint::generator() * *scalar);
+        // Construct a scalar from bytes
+        let scalar = ScalarPrimitive::<Secp256k1>::from_bytes(&other.into());
+        let scalar = Option::<ScalarPrimitive<Secp256k1>>::from(scalar);
+        let scalar = scalar.ok_or(PublicKeyError::InvalidScalar)?;
+        let scalar = Scalar::from(scalar);
+
+        let point = self.to_projective() + (AffinePoint::generator() * scalar);
         Ok(Self::from_affine(point.into())
             .expect(bug!("Could not from_affine after scalar arithmetic")))
     }

crates/keyfork-shard/src/lib.rs

@@ -10,6 +10,7 @@ use aes_gcm::{
     aead::{consts::U12, Aead},
     Aes256Gcm, KeyInit, Nonce,
 };
+use base64::prelude::{Engine, BASE64_STANDARD};
 use hkdf::Hkdf;
 use keyfork_bug::{bug, POISONED_MUTEX};
 use keyfork_mnemonic_util::{English, Mnemonic};
@@ -23,7 +24,6 @@ use keyfork_prompt::{
 use sha2::Sha256;
 use sharks::{Share, Sharks};
 use x25519_dalek::{EphemeralSecret, PublicKey};
-use base64::prelude::{BASE64_STANDARD, Engine};
 
 // 32-byte share, 1-byte index, 1-byte threshold, 1-byte version == 36 bytes
 // Encrypted, is 52 bytes
@@ -212,7 +212,9 @@ pub trait Format {
             if let Ok(Some(qrcode_content)) =
                 keyfork_qrcode::scan_camera(std::time::Duration::from_secs(30), 0)
             {
-                let decoded_data = BASE64_STANDARD.decode(qrcode_content).unwrap();
+                let decoded_data = BASE64_STANDARD
+                    .decode(qrcode_content)
+                    .expect(bug!("qrcode should contain base64 encoded data"));
                 pubkey_data = Some(decoded_data.try_into().map_err(|_| InvalidData)?)
             } else {
                 prompt
@@ -300,7 +302,10 @@ pub trait Format {
             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(&BASE64_STANDARD.encode(qrcode_data), ErrorCorrection::Highest) {
+            if let Ok(qrcode) = qrencode(
+                &BASE64_STANDARD.encode(qrcode_data),
+                ErrorCorrection::Highest,
+            ) {
                 prompt
                     .lock()
                     .expect(bug!(POISONED_MUTEX))
@@ -433,7 +438,10 @@ pub fn remote_decrypt(w: &mut impl Write) -> Result<(), Box<dyn std::error::Erro
         {
             use keyfork_qrcode::{qrencode, ErrorCorrection};
             let qrcode_data = key_mnemonic.to_bytes();
-            if let Ok(qrcode) = qrencode(&BASE64_STANDARD.encode(qrcode_data), ErrorCorrection::Highest) {
+            if let Ok(qrcode) = qrencode(
+                &BASE64_STANDARD.encode(qrcode_data),
+                ErrorCorrection::Highest,
+            ) {
                 pm.prompt_message(PromptMessage::Text(format!(
                     concat!(
                         "A QR code will be displayed after this prompt. ",
@@ -464,7 +472,14 @@ pub fn remote_decrypt(w: &mut impl Write) -> Result<(), Box<dyn std::error::Erro
             if let Ok(Some(qrcode_content)) =
                 keyfork_qrcode::scan_camera(std::time::Duration::from_secs(QRCODE_TIMEOUT), 0)
             {
-                let decoded_data = BASE64_STANDARD.decode(qrcode_content).unwrap();
+                let decoded_data = BASE64_STANDARD
+                    .decode(qrcode_content)
+                    .expect(bug!("qrcode should contain base64 encoded data"));
+                assert_eq!(
+                    decoded_data.len(),
+                    ENCRYPTED_LENGTH as usize,
+                    bug!("invalid payload data")
+                );
                 let _ = pubkey_data.insert(decoded_data[..32].try_into().map_err(|_| InvalidData)?);
                 let _ = payload_data.insert(decoded_data[32..].to_vec());
             } else {