zcash_keys: Add decode_extfvk_with_network

zcash_keys/CHANGELOG.md

@@ -6,6 +6,12 @@ and this library adheres to Rust's notion of
 
 ## [Unreleased]
 
+### Added
+- `zcash_keys::encoding::decode_extfvk_with_network`
+- `impl std::error::Error for Bech32DecodeError`
+- `impl std::error::Error for DecodingError`
+- `impl std::error::Error for DerivationError`
+
 ## [0.3.0] - 2024-08-19
 ### Notable changes
 - `zcash_keys`:

zcash_keys/src/encoding.rs

@@ -6,7 +6,7 @@
 use crate::address::UnifiedAddress;
 use bs58::{self, decode::Error as Bs58Error};
 use std::fmt;
-use zcash_primitives::consensus::NetworkConstants;
+use zcash_primitives::consensus::{NetworkConstants, NetworkType};
 
 use zcash_address::unified::{self, Encoding};
 use zcash_primitives::{consensus, legacy::TransparentAddress};
@@ -66,6 +66,16 @@
     }
 }
 
+#[cfg(feature = "sapling")]
+impl std::error::Error for Bech32DecodeError {
+    fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
+        match &self {
+            Bech32DecodeError::Bech32Error(e) => Some(e),
+            _ => None,
+        }
+    }
+}
+
 #[cfg(feature = "sapling")]
 fn bech32_decode<T, F>(hrp: &str, s: &str, read: F) -> Result<T, Bech32DecodeError>
 where
@@ -245,9 +255,8 @@
     bech32_encode(hrp, |w| extfvk.write(w))
 }
 
-/// Decodes an [`ExtendedFullViewingKey`] from a Bech32-encoded string.
-///
-/// [`ExtendedFullViewingKey`]: sapling::zip32::ExtendedFullViewingKey
+/// Decodes an [`ExtendedFullViewingKey`] from a Bech32-encoded string, verifying that it matches
+/// the provided human-readable prefix.
 #[cfg(feature = "sapling")]
 pub fn decode_extended_full_viewing_key(
     hrp: &str,
@@ -256,6 +265,39 @@
     bech32_decode(hrp, s, |data| ExtendedFullViewingKey::read(&data[..]).ok())
 }
 
+/// Decodes an [`ExtendedFullViewingKey`] and the [`NetworkType`] that it is intended for use with
+/// from a Bech32-encoded string.
+#[cfg(feature = "sapling")]
+pub fn decode_extfvk_with_network(
+    s: &str,
+) -> Result<(NetworkType, ExtendedFullViewingKey), Bech32DecodeError> {
+    use zcash_protocol::constants::{mainnet, regtest, testnet};
+
+    let (decoded_hrp, data, variant) = bech32::decode(s)?;
+    if variant != Variant::Bech32 {
+        Err(Bech32DecodeError::IncorrectVariant(variant))
+    } else {
+        let network = match &decoded_hrp[..] {
+            mainnet::HRP_SAPLING_EXTENDED_FULL_VIEWING_KEY => Ok(NetworkType::Main),
+            testnet::HRP_SAPLING_EXTENDED_FULL_VIEWING_KEY => Ok(NetworkType::Test),
+            regtest::HRP_SAPLING_EXTENDED_FULL_VIEWING_KEY => Ok(NetworkType::Regtest),
+            other => Err(Bech32DecodeError::HrpMismatch {
+                expected: format!(
+                    "One of {}, {}, or {}",
+                    mainnet::HRP_SAPLING_EXTENDED_FULL_VIEWING_KEY,
+                    testnet::HRP_SAPLING_EXTENDED_FULL_VIEWING_KEY,
+                    regtest::HRP_SAPLING_EXTENDED_FULL_VIEWING_KEY,
+                ),
+                actual: other.to_string(),
+            }),
+        }?;
+        let fvk = ExtendedFullViewingKey::read(&Vec::<u8>::from_base32(&data)?[..])
+            .map_err(|_| Bech32DecodeError::ReadError)?;
+
+        Ok((network, fvk))
+    }
+}
+
 /// Writes a [`PaymentAddress`] as a Bech32-encoded string.
 ///
 /// # Examples

zcash_keys/src/keys.rs

@@ -37,6 +37,9 @@
 #[cfg(feature = "orchard")]
 use orchard::{self, keys::Scope};
 
+#[cfg(all(feature = "sapling", feature = "unstable"))]
+use ::sapling::zip32::ExtendedFullViewingKey;
+
 #[cfg(feature = "sapling")]
 pub mod sapling {
     pub use sapling::zip32::{
@@ -111,6 +114,8 @@
     }
 }
 
+impl std::error::Error for DerivationError {}
+
 /// A version identifier for the encoding of unified spending keys.
 ///
 /// Each era corresponds to a range of block heights. During an era, the unified spending key
@@ -176,6 +181,8 @@
     }
 }
 
+impl std::error::Error for DecodingError {}
+
 #[cfg(feature = "unstable")]
 impl Era {
     /// Returns the unique identifier for the era.
@@ -674,6 +681,24 @@
             vec![],
         )
     }
+
+    #[cfg(all(feature = "sapling", feature = "unstable"))]
+    pub fn from_sapling_extended_full_viewing_key(
+        sapling: ExtendedFullViewingKey,
+    ) -> Result<UnifiedFullViewingKey, DerivationError> {
+        Self::from_checked_parts(
+            #[cfg(feature = "transparent-inputs")]
+            None,
+            #[cfg(feature = "sapling")]
+            Some(sapling.to_diversifiable_full_viewing_key()),
+            #[cfg(feature = "orchard")]
+            None,
+            // We don't currently allow constructing new UFVKs with unknown items, but we store
+            // this to allow parsing such UFVKs.
+            vec![],
+        )
+    }
+
     /// Construct a UFVK from its constituent parts, after verifying that UIVK derivation can
     /// succeed.
     fn from_checked_parts(