Implement standard conversion traits for Secp256k1Keys

- Improve Display impl for key-util Error, add more error variants
- Update format in key-util unit tests

utils/key-utils/src/lib.rs

@@ -3,17 +3,28 @@ use core::convert::TryFrom;
 use secp256k1::{SecretKey, XOnlyPublicKey};
 use serde::{Deserialize, Serialize};
 use std::fmt::Display;
+use std::str::FromStr;
 
 #[derive(Debug)]
 pub enum Error {
     Bs58Decode(Bs58DecodeError),
     Secp256k1(secp256k1::Error),
-    Custom,
+    KeyVersion(u16),
+    KeyLength,
+    Custom(String),
 }
 
 impl Display for Error {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-        write!(f, "Key Utils Error")
+        match self {
+            Self::Bs58Decode(error) => write!(f, "Base58 code error: {error}"),
+            Self::Secp256k1(error) => write!(f, "Secp256k1 error: {error}"),
+            Self::KeyVersion(obtained) => {
+                write!(f, "Unknown public key version. version found: {obtained}")
+            }
+            Self::KeyLength => write!(f, "Bad key length"),
+            Self::Custom(error) => write!(f, "Custom error: {error}"),
+        }
     }
 }
 
@@ -29,14 +40,22 @@ impl From<secp256k1::Error> for Error {
     }
 }
 
-#[derive(Debug, Clone, Serialize, Deserialize)]
+#[derive(Debug, Copy, Clone, Serialize, Deserialize)]
 #[serde(into = "String", try_from = "String")]
 pub struct Secp256k1SecretKey(pub SecretKey);
 
 impl TryFrom<String> for Secp256k1SecretKey {
     type Error = Error;
 
     fn try_from(value: String) -> Result<Self, Self::Error> {
+        value.parse()
+    }
+}
+
+impl FromStr for Secp256k1SecretKey {
+    type Err = Error;
+
+    fn from_str(value: &str) -> Result<Self, Self::Err> {
         let decoded = decode(value).with_check(None).into_vec()?;
         let secret = SecretKey::from_slice(&decoded)?;
         Ok(Secp256k1SecretKey(secret))
@@ -45,27 +64,43 @@ impl TryFrom<String> for Secp256k1SecretKey {
 
 impl From<Secp256k1SecretKey> for String {
     fn from(secret: Secp256k1SecretKey) -> Self {
-        let bytes = secret.0.secret_bytes();
-        bs58::encode(bytes).with_check().into_string()
+        secret.to_string()
     }
 }
 
-#[derive(Debug, Clone, Serialize, Deserialize)]
+impl Display for Secp256k1SecretKey {
+    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
+        let bytes = self.0.secret_bytes();
+        f.write_str(&bs58::encode(bytes).with_check().into_string())
+    }
+}
+
+#[derive(Debug, Copy, Clone, Serialize, Deserialize)]
 #[serde(into = "String", try_from = "String")]
 pub struct Secp256k1PublicKey(pub XOnlyPublicKey);
 
 impl TryFrom<String> for Secp256k1PublicKey {
     type Error = Error;
 
     fn try_from(value: String) -> Result<Self, Self::Error> {
+        value.parse()
+    }
+}
+
+impl FromStr for Secp256k1PublicKey {
+    type Err = Error;
+
+    fn from_str(value: &str) -> Result<Self, Self::Err> {
         let decoded = decode(value).with_check(None).into_vec()?;
         if decoded.len() < 34 {
-            return Err(Error::Custom);
+            return Err(Error::KeyLength);
         }
-        if decoded[..2] != [1, 0] {
-            return Err(Error::Custom);
+        let key_version =
+            u16::from_le_bytes(decoded[..2].try_into().expect("Invalid array length"));
+        if key_version != 1 {
+            return Err(Error::KeyVersion(key_version));
         }
-        let public = XOnlyPublicKey::from_slice(&decoded[2..]).expect("Invalid public key");
+        let public = XOnlyPublicKey::from_slice(&decoded[2..]).map_err(Error::Secp256k1)?;
         Ok(Secp256k1PublicKey(public))
     }
 }
@@ -97,28 +132,61 @@ impl Secp256k1SecretKey {
     }
 }
 
+impl From<Secp256k1SecretKey> for Secp256k1PublicKey {
+    fn from(value: Secp256k1SecretKey) -> Self {
+        let context = secp256k1::Secp256k1::new();
+        let (x_coordinate, _) = value.0.public_key(&context).x_only_public_key();
+        Self(x_coordinate)
+    }
+}
+
 #[cfg(test)]
 mod test {
     use super::*;
 
-    #[derive(Serialize, Deserialize)]
-    struct Test {
-        public_key: Secp256k1PublicKey,
-        secret_key: Secp256k1SecretKey,
-    }
-
     #[test]
-    fn deserialize_serialize_toml() {
-        let pub_ = "3VANfft6ei6jQq1At7d8nmiZzVhBFS4CiQujdgim1ign";
-        let secr = "7qbpUjScc865jyX2kiB4NVJANoC7GA7TAJupdzXWkc62";
-        let string = r#"
-            public_key = "3VANfft6ei6jQq1At7d8nmiZzVhBFS4CiQujdgim1ign"
-            secret_key = "7qbpUjScc865jyX2kiB4NVJANoC7GA7TAJupdzXWkc62"
-        "#;
-        let test: Test = toml::from_str(&string).unwrap();
-        let ser_p: String = test.public_key.try_into().unwrap();
-        let ser_s: String = test.secret_key.try_into().unwrap();
-        assert_eq!(ser_p, pub_);
-        assert_eq!(ser_s, secr);
+    fn key_conversions() {
+        let secret_key = "zmBEmPhqo3A92FkiLVvyCz6htc3e53ph3ZbD4ASqGaLjwnFLi";
+        let public_key = "9bDuixKmZqAJnrmP746n8zU1wyAQRrus7th9dxnkPg6RzQvCnan";
+        let bad_public_key1 = "9bDuixKmZqAJnrmP746n8zU1wyAQRrus7th9dxnkPg6RzQvCnam"; // invalid checksum (swapped char)
+        let bad_public_key2 = "2myPhc5vkPzuC5FXNK5tee79WmP7uoLh55SxezoF8iqwF3E3rnPY"; // invalid version (version 12)
+        let bad_public_key3 = "2wmHTKZkLg2QzXyEXGMBXzKP7JXDUt8yy9SA5hoQwERc92qR6c"; // invalid length (1 B missing)
+
+        let error = bad_public_key1
+            .parse::<Secp256k1PublicKey>()
+            .expect_err("Bad bud public key failed to raise error");
+        assert!(
+            matches!(error, Error::Bs58Decode(_)),
+            "expected failed checksum error, got {}",
+            error
+        );
+        let error = bad_public_key2
+            .parse::<Secp256k1PublicKey>()
+            .expect_err("Bad bud public key failed to raise error");
+        assert!(
+            matches!(error, Error::KeyVersion(_)),
+            "expected invalid key version error, got {}",
+            error
+        );
+        let error = bad_public_key3
+            .parse::<Secp256k1PublicKey>()
+            .expect_err("Bad bud public key failed to raise error");
+        assert!(
+            matches!(error, Error::KeyLength),
+            "expected invalid key length error, got {}",
+            error
+        );
+
+        let parsed_key = secret_key
+            .parse::<Secp256k1SecretKey>()
+            .expect("Invalid test key");
+
+        let calculated_public_key = Secp256k1PublicKey::from(parsed_key);
+        assert_eq!(calculated_public_key.to_string(), public_key);
+
+        let parsed_public_key = public_key
+            .parse::<Secp256k1PublicKey>()
+            .expect("Invalid test pubkey");
+        assert_eq!(calculated_public_key.0, parsed_public_key.0);
     }
 }