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Merge bitcoin/bitcoin#25642: Don't wrap around when deriving an extended key at a too large depth

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fb9faffae3 extended keys: fail to derive too large depth instead of wrapping around (Antoine Poinsot)
8dc6670ce1 descriptor: don't assert success of extended key derivation (Antoine Poinsot)
50cfc9e761 (pubk)key: mark Derive() as nodiscard (Antoine Poinsot)
0ca258a5ac descriptor: never ignore the return value when deriving an extended key (Antoine Poinsot)
d3599c22bd spkman: don't ignore the return value when deriving an extended key (Antoine Poinsot)

Pull request description:

  We would previously  silently wrap the derived child's depth back to `0`. Instead, explicitly fail when trying to derive an impossible depth, and handle the error in callers.

  An extended fuzzing corpus of `descriptor_parse` triggered this behaviour, which was reported by MarcoFalke.

  Fixes #25751.

ACKs for top commit:
  achow101:
    re-ACK fb9faffae3
  instagibbs:
    utACK  fb9faffae3

Tree-SHA512: 9f75c23572ce847239bd15e5497df2960b6bd63c61ea72347959d968b5c4c9a4bfeee284e76bdcd7bacbf9eeb70feee85ffd3e316f353ca6eca30e93aafad343
This commit is contained in:
Andrew Chow
2022-08-10 14:09:53 -04:00
parent 251c535800 fb9faffae3
commit 93999a5fbe
8 changed files with 42 additions and 16 deletions
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15
src/wallet/scriptpubkeyman.cpp
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@ -1080,6 +1080,13 @@ CPubKey LegacyScriptPubKeyMan::GenerateNewKey(WalletBatch &batch, CHDChain& hd_c
return pubkey;
}
//! Try to derive an extended key, throw if it fails.
static void DeriveExtKey(CExtKey& key_in, unsigned int index, CExtKey& key_out) {
if (!key_in.Derive(key_out, index)) {
throw std::runtime_error("Could not derive extended key");
}
}
void LegacyScriptPubKeyMan::DeriveNewChildKey(WalletBatch &batch, CKeyMetadata& metadata, CKey& secret, CHDChain& hd_chain, bool internal)
{
// for now we use a fixed keypath scheme of m/0'/0'/k
@ -1097,11 +1104,11 @@ void LegacyScriptPubKeyMan::DeriveNewChildKey(WalletBatch &batch, CKeyMetadata&
// derive m/0'
// use hardened derivation (child keys >= 0x80000000 are hardened after bip32)
masterKey.Derive(accountKey, BIP32_HARDENED_KEY_LIMIT);
DeriveExtKey(masterKey, BIP32_HARDENED_KEY_LIMIT, accountKey);
// derive m/0'/0' (external chain) OR m/0'/1' (internal chain)
assert(internal ? m_storage.CanSupportFeature(FEATURE_HD_SPLIT) : true);
accountKey.Derive(chainChildKey, BIP32_HARDENED_KEY_LIMIT+(internal ? 1 : 0));
DeriveExtKey(accountKey, BIP32_HARDENED_KEY_LIMIT+(internal ? 1 : 0), chainChildKey);
// derive child key at next index, skip keys already known to the wallet
do {
@ -1109,7 +1116,7 @@ void LegacyScriptPubKeyMan::DeriveNewChildKey(WalletBatch &batch, CKeyMetadata&
// childIndex | BIP32_HARDENED_KEY_LIMIT = derive childIndex in hardened child-index-range
// example: 1 | BIP32_HARDENED_KEY_LIMIT == 0x80000001 == 2147483649
if (internal) {
chainChildKey.Derive(childKey, hd_chain.nInternalChainCounter | BIP32_HARDENED_KEY_LIMIT);
DeriveExtKey(chainChildKey, hd_chain.nInternalChainCounter | BIP32_HARDENED_KEY_LIMIT, childKey);
metadata.hdKeypath = "m/0'/1'/" + ToString(hd_chain.nInternalChainCounter) + "'";
metadata.key_origin.path.push_back(0 | BIP32_HARDENED_KEY_LIMIT);
metadata.key_origin.path.push_back(1 | BIP32_HARDENED_KEY_LIMIT);
@ -1117,7 +1124,7 @@ void LegacyScriptPubKeyMan::DeriveNewChildKey(WalletBatch &batch, CKeyMetadata&
hd_chain.nInternalChainCounter++;
}
else {
chainChildKey.Derive(childKey, hd_chain.nExternalChainCounter | BIP32_HARDENED_KEY_LIMIT);
DeriveExtKey(chainChildKey, hd_chain.nExternalChainCounter | BIP32_HARDENED_KEY_LIMIT, childKey);
metadata.hdKeypath = "m/0'/0'/" + ToString(hd_chain.nExternalChainCounter) + "'";
metadata.key_origin.path.push_back(0 | BIP32_HARDENED_KEY_LIMIT);
metadata.key_origin.path.push_back(0 | BIP32_HARDENED_KEY_LIMIT);