From 187eae8a13d958e21a879bf4ad95c95416b43c0a Mon Sep 17 00:00:00 2001
From: Dr Maxim Orlovsky <orlovsky@pandoracore.com>
Date: Sat, 1 May 2021 13:40:21 +0200
Subject: [PATCH] Streamlining private key construction API in BIP32

---
 src/util/bip32.rs | 25 ++++++-------------------
 src/util/ecdsa.rs |  8 ++++++++
 2 files changed, 14 insertions(+), 19 deletions(-)

diff --git a/src/util/bip32.rs b/src/util/bip32.rs
index 0e70c8ee23..efc40a4fa4 100644
--- a/src/util/bip32.rs
+++ b/src/util/bip32.rs
@@ -497,14 +497,12 @@ impl ExtendedPrivKey {
         hmac_engine.input(seed);
         let hmac_result: Hmac<sha512::Hash> = Hmac::from_engine(hmac_engine);
 
-        let sk = secp256k1::SecretKey::from_slice(&hmac_result[..32])?;
-
         Ok(ExtendedPrivKey {
             network: network,
             depth: 0,
             parent_fingerprint: Default::default(),
             child_number: ChildNumber::from_normal_idx(0)?,
-            private_key: PrivateKey::new(sk, network),
+            private_key: PrivateKey::from_slice(&hmac_result[..32], network)?,
             chain_code: ChainCode::from(&hmac_result[32..]),
         })
     }
@@ -541,11 +539,8 @@ impl ExtendedPrivKey {
 
         hmac_engine.input(&endian::u32_to_array_be(u32::from(i)));
         let hmac_result: Hmac<sha512::Hash> = Hmac::from_engine(hmac_engine);
-        let mut sk = PrivateKey::new(
-            secp256k1::SecretKey::from_slice(&hmac_result[..32])?,
-            self.network
-        );
-        sk.key.add_assign(&self.private_key[..]).map_err(Error::Ecdsa)?;
+        let mut sk = PrivateKey::from_slice(&hmac_result[..32], self.network)?;
+        sk.key.add_assign(&self.private_key[..])?;
 
         Ok(ExtendedPrivKey {
             network: self.network,
@@ -573,18 +568,13 @@ impl ExtendedPrivKey {
             return Err(Error::UnknownVersion(ver));
         };
 
-        let sk = PrivateKey::new(
-            secp256k1::SecretKey::from_slice(&data[46..78])?,
-            network
-        );
-
         Ok(ExtendedPrivKey {
             network: network,
             depth: data[4],
             parent_fingerprint: Fingerprint::from(&data[5..9]),
             child_number: endian::slice_to_u32_be(&data[9..13]).into(),
             chain_code: ChainCode::from(&data[13..45]),
-            private_key: sk,
+            private_key: PrivateKey::from_slice(&data[46..78], network)?,
         })
     }
 
@@ -656,10 +646,7 @@ impl ExtendedPubKey {
 
                 let hmac_result: Hmac<sha512::Hash> = Hmac::from_engine(hmac_engine);
 
-                let private_key = PrivateKey::new(
-                    secp256k1::SecretKey::from_slice(&hmac_result[..32])?,
-                    self.network,
-                );
+                let private_key = PrivateKey::from_slice(&hmac_result[..32], self.network)?;
                 let chain_code = ChainCode::from(&hmac_result[32..]);
                 Ok((private_key, chain_code))
             }
@@ -674,7 +661,7 @@ impl ExtendedPubKey {
     ) -> Result<ExtendedPubKey, Error> {
         let (sk, chain_code) = self.ckd_pub_tweak(i)?;
         let mut pk = self.public_key;
-        pk.key.add_exp_assign(secp, &sk[..]).map_err(Error::Ecdsa)?;
+        pk.key.add_exp_assign(secp, &sk[..])?;
 
         Ok(ExtendedPubKey {
             network: self.network,
diff --git a/src/util/ecdsa.rs b/src/util/ecdsa.rs
index c62ac5851d..99d7af67a6 100644
--- a/src/util/ecdsa.rs
+++ b/src/util/ecdsa.rs
@@ -201,6 +201,14 @@ impl PrivateKey {
         self.key[..].to_vec()
     }
 
+    /// Deserialize a private key from a slice
+    pub fn from_slice(data: &[u8], network: Network) -> Result<PrivateKey, Error> {
+        Ok(PrivateKey::new(
+            secp256k1::SecretKey::from_slice(data)?,
+            network,
+        ))
+    }
+
     /// Format the private key to WIF format.
     pub fn fmt_wif(&self, fmt: &mut dyn fmt::Write) -> fmt::Result {
         let mut ret = [0; 34];