refactor: Take Span in SetSeed

This makes calling code less verbose and less fragile. Also, by adding
the CKey::data() member function, it is now possible to call HexStr()
with a CKey object.

Author: MarcoFalke

src/key.cpp

@@ -319,10 +319,11 @@ bool CExtKey::Derive(CExtKey &out, unsigned int _nChild) const {
     return key.Derive(out.key, out.chaincode, _nChild, chaincode);
 }
 
-void CExtKey::SetSeed(const unsigned char *seed, unsigned int nSeedLen) {
+void CExtKey::SetSeed(Span<const uint8_t> seed)
+{
     static const unsigned char hashkey[] = {'B','i','t','c','o','i','n',' ','s','e','e','d'};
     std::vector<unsigned char, secure_allocator<unsigned char>> vout(64);
-    CHMAC_SHA512(hashkey, sizeof(hashkey)).Write(seed, nSeedLen).Finalize(vout.data());
+    CHMAC_SHA512{hashkey, sizeof(hashkey)}.Write(seed.data(), seed.size()).Finalize(vout.data());
     key.Set(vout.data(), vout.data() + 32, true);
     memcpy(chaincode.begin(), vout.data() + 32, 32);
     nDepth = 0;

src/key.h

@@ -85,6 +85,7 @@ class CKey
 
     //! Simple read-only vector-like interface.
     unsigned int size() const { return (fValid ? keydata.size() : 0); }
+    const unsigned char* data() const { return keydata.data(); }
     const unsigned char* begin() const { return keydata.data(); }
     const unsigned char* end() const { return keydata.data() + size(); }
 
@@ -177,7 +178,7 @@ struct CExtKey {
     void Decode(const unsigned char code[BIP32_EXTKEY_SIZE]);
     bool Derive(CExtKey& out, unsigned int nChild) const;
     CExtPubKey Neuter() const;
-    void SetSeed(const unsigned char* seed, unsigned int nSeedLen);
+    void SetSeed(Span<const uint8_t> seed);
 };
 
 /** Initialize the elliptic curve support. May not be called twice without calling ECC_Stop first. */

src/test/bip32_tests.cpp

@@ -124,7 +124,7 @@ void RunTest(const TestVector &test) {
     std::vector<unsigned char> seed = ParseHex(test.strHexMaster);
     CExtKey key;
     CExtPubKey pubkey;
-    key.SetSeed(seed.data(), seed.size());
+    key.SetSeed(seed);
     pubkey = key.Neuter();
     for (const TestDerivation &derive : test.vDerive) {
         unsigned char data[74];

src/test/key_io_tests.cpp

@@ -46,7 +46,7 @@ BOOST_AUTO_TEST_CASE(key_io_valid_parse)
             privkey = DecodeSecret(exp_base58string);
             BOOST_CHECK_MESSAGE(privkey.IsValid(), "!IsValid:" + strTest);
             BOOST_CHECK_MESSAGE(privkey.IsCompressed() == isCompressed, "compressed mismatch:" + strTest);
-            BOOST_CHECK_MESSAGE(privkey.size() == exp_payload.size() && std::equal(privkey.begin(), privkey.end(), exp_payload.begin()), "key mismatch:" + strTest);
+            BOOST_CHECK_MESSAGE(Span<const uint8_t>{privkey} == Span<const uint8_t>{exp_payload}, "key mismatch:" + strTest);
 
             // Private key must be invalid public key
             destination = DecodeDestination(exp_base58string);

src/wallet/rpcdump.cpp

@@ -797,7 +797,7 @@ RPCHelpMan dumpwallet()
         CKey seed;
         if (spk_man.GetKey(seed_id, seed)) {
             CExtKey masterKey;
-            masterKey.SetSeed(seed.begin(), seed.size());
+            masterKey.SetSeed(seed);
 
             file << "# extended private masterkey: " << EncodeExtKey(masterKey) << "\n\n";
         }

src/wallet/scriptpubkeyman.cpp

@@ -400,7 +400,7 @@ void LegacyScriptPubKeyMan::UpgradeKeyMetadata()
             CKey key;
             GetKey(meta.hd_seed_id, key);
             CExtKey masterKey;
-            masterKey.SetSeed(key.begin(), key.size());
+            masterKey.SetSeed(key);
             // Add to map
             CKeyID master_id = masterKey.key.GetPubKey().GetID();
             std::copy(master_id.begin(), master_id.begin() + 4, meta.key_origin.fingerprint);
@@ -1085,7 +1085,7 @@ void LegacyScriptPubKeyMan::DeriveNewChildKey(WalletBatch &batch, CKeyMetadata&
     if (!GetKey(hd_chain.seed_id, seed))
         throw std::runtime_error(std::string(__func__) + ": seed not found");
 
-    masterKey.SetSeed(seed.begin(), seed.size());
+    masterKey.SetSeed(seed);
 
     // derive m/0'
     // use hardened derivation (child keys >= 0x80000000 are hardened after bip32)

src/wallet/wallet.cpp

@@ -3160,7 +3160,7 @@ void CWallet::SetupDescriptorScriptPubKeyMans()
 
         // Get the extended key
         CExtKey master_key;
-        master_key.SetSeed(seed_key.begin(), seed_key.size());
+        master_key.SetSeed(seed_key);
 
         for (bool internal : {false, true}) {
             for (OutputType t : OUTPUT_TYPES) {