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Add DescriptorCache* read_cache and DescriptorCache* write_cache to Expand and GetPubKey 

Have Expand, ExpandFromCache, and ExpandHelper take additional DescriptorCache
parameters. These are then passed into PubkeyProvider::GetPubKey which
also takes them as arguments.

Reading and writing to the cache is pushed down into GetPubKey. The old cache where
pubkeys are serialized to a vector is completely removed and instead xpubs are being
cached in DescriptorCache.
This commit is contained in:
Andrew Chow 2020-02-25 16:01:58 -05:00
parent 66c2cadc91
commit 58f54b686f
3 changed files with 74 additions and 61 deletions
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121
src/script/descriptor.cpp
View File

@ -160,8 +160,12 @@ public:
virtual ~PubkeyProvider() = default;
/** Derive a public key. If key==nullptr, only info is desired. */
virtual bool GetPubKey(int pos, const SigningProvider& arg, CPubKey* key, KeyOriginInfo& info) const = 0;
/** Derive a public key.
* read_cache is the cache to read keys from (if not nullptr)
* write_cache is the cache to write keys to (if not nullptr)
* Caches are not exclusive but this is not tested. Currently we use them exclusively
*/
virtual bool GetPubKey(int pos, const SigningProvider& arg, CPubKey& key, KeyOriginInfo& info, const DescriptorCache* read_cache = nullptr, DescriptorCache* write_cache = nullptr) const = 0;
/** Whether this represent multiple public keys at different positions. */
virtual bool IsRange() const = 0;
@ -191,9 +195,9 @@ class OriginPubkeyProvider final : public PubkeyProvider
public:
OriginPubkeyProvider(uint32_t exp_index, KeyOriginInfo info, std::unique_ptr<PubkeyProvider> provider) : PubkeyProvider(exp_index), m_origin(std::move(info)), m_provider(std::move(provider)) {}
bool GetPubKey(int pos, const SigningProvider& arg, CPubKey* key, KeyOriginInfo& info) const override
bool GetPubKey(int pos, const SigningProvider& arg, CPubKey& key, KeyOriginInfo& info, const DescriptorCache* read_cache = nullptr, DescriptorCache* write_cache = nullptr) const override
{
if (!m_provider->GetPubKey(pos, arg, key, info)) return false;
if (!m_provider->GetPubKey(pos, arg, key, info, read_cache, write_cache)) return false;
std::copy(std::begin(m_origin.fingerprint), std::end(m_origin.fingerprint), info.fingerprint);
info.path.insert(info.path.begin(), m_origin.path.begin(), m_origin.path.end());
return true;
@ -221,9 +225,9 @@ class ConstPubkeyProvider final : public PubkeyProvider
public:
ConstPubkeyProvider(uint32_t exp_index, const CPubKey& pubkey) : PubkeyProvider(exp_index), m_pubkey(pubkey) {}
bool GetPubKey(int pos, const SigningProvider& arg, CPubKey* key, KeyOriginInfo& info) const override
bool GetPubKey(int pos, const SigningProvider& arg, CPubKey& key, KeyOriginInfo& info, const DescriptorCache* read_cache = nullptr, DescriptorCache* write_cache = nullptr) const override
{
if (key) *key = m_pubkey;
key = m_pubkey;
info.path.clear();
CKeyID keyid = m_pubkey.GetID();
std::copy(keyid.begin(), keyid.begin() + sizeof(info.fingerprint), info.fingerprint);
@ -271,6 +275,16 @@ class BIP32PubkeyProvider final : public PubkeyProvider
return true;
}
// Derives the last xprv
bool GetDerivedExtKey(const SigningProvider& arg, CExtKey& xprv) const
{
if (!GetExtKey(arg, xprv)) return false;
for (auto entry : m_path) {
xprv.Derive(xprv, entry);
}
return true;
}
bool IsHardened() const
{
if (m_derive == DeriveType::HARDENED) return true;
@ -284,29 +298,47 @@ public:
BIP32PubkeyProvider(uint32_t exp_index, const CExtPubKey& extkey, KeyPath path, DeriveType derive) : PubkeyProvider(exp_index), m_root_extkey(extkey), m_path(std::move(path)), m_derive(derive) {}
bool IsRange() const override { return m_derive != DeriveType::NO; }
size_t GetSize() const override { return 33; }
bool GetPubKey(int pos, const SigningProvider& arg, CPubKey* key, KeyOriginInfo& info) const override
bool GetPubKey(int pos, const SigningProvider& arg, CPubKey& key_out, KeyOriginInfo& final_info_out, const DescriptorCache* read_cache = nullptr, DescriptorCache* write_cache = nullptr) const override
{
if (key) {
if (IsHardened()) {
CKey priv_key;
if (!GetPrivKey(pos, arg, priv_key)) return false;
*key = priv_key.GetPubKey();
} else {
// TODO: optimize by caching
CExtPubKey extkey = m_root_extkey;
for (auto entry : m_path) {
extkey.Derive(extkey, entry);
}
if (m_derive == DeriveType::UNHARDENED) extkey.Derive(extkey, pos);
assert(m_derive != DeriveType::HARDENED);
*key = extkey.pubkey;
}
}
// Info of parent of the to be derived pubkey
KeyOriginInfo parent_info;
CKeyID keyid = m_root_extkey.pubkey.GetID();
std::copy(keyid.begin(), keyid.begin() + sizeof(info.fingerprint), info.fingerprint);
info.path = m_path;
if (m_derive == DeriveType::UNHARDENED) info.path.push_back((uint32_t)pos);
if (m_derive == DeriveType::HARDENED) info.path.push_back(((uint32_t)pos) | 0x80000000L);
std::copy(keyid.begin(), keyid.begin() + sizeof(parent_info.fingerprint), parent_info.fingerprint);
parent_info.path = m_path;
// Info of the derived key itself which is copied out upon successful completion
KeyOriginInfo final_info_out_tmp = parent_info;
if (m_derive == DeriveType::UNHARDENED) final_info_out_tmp.path.push_back((uint32_t)pos);
if (m_derive == DeriveType::HARDENED) final_info_out_tmp.path.push_back(((uint32_t)pos) | 0x80000000L);
// Derive keys or fetch them from cache
CExtPubKey final_extkey = m_root_extkey;
bool der = true;
if (read_cache) {
if (!read_cache->GetCachedDerivedExtPubKey(m_expr_index, pos, final_extkey)) return false;
} else if (IsHardened()) {
CExtKey xprv;
if (!GetDerivedExtKey(arg, xprv)) return false;
if (m_derive == DeriveType::UNHARDENED) der = xprv.Derive(xprv, pos);
if (m_derive == DeriveType::HARDENED) der = xprv.Derive(xprv, pos | 0x80000000UL);
final_extkey = xprv.Neuter();
} else {
for (auto entry : m_path) {
der = final_extkey.Derive(final_extkey, entry);
assert(der);
}
if (m_derive == DeriveType::UNHARDENED) der = final_extkey.Derive(final_extkey, pos);
assert(m_derive != DeriveType::HARDENED);
}
assert(der);
final_info_out = final_info_out_tmp;
key_out = final_extkey.pubkey;
if (write_cache) {
write_cache->CacheDerivedExtPubKey(m_expr_index, pos, final_extkey);
}
return true;
}
std::string ToString() const override
@ -332,10 +364,7 @@ public:
bool GetPrivKey(int pos, const SigningProvider& arg, CKey& key) const override
{
CExtKey extkey;
if (!GetExtKey(arg, extkey)) return false;
for (auto entry : m_path) {
extkey.Derive(extkey, entry);
}
if (!GetDerivedExtKey(arg, extkey)) return false;
if (m_derive == DeriveType::UNHARDENED) extkey.Derive(extkey, pos);
if (m_derive == DeriveType::HARDENED) extkey.Derive(extkey, pos | 0x80000000UL);
key = extkey.key;
@ -434,7 +463,7 @@ public:
return ret;
}
bool ExpandHelper(int pos, const SigningProvider& arg, Span<const unsigned char>* cache_read, std::vector<CScript>& output_scripts, FlatSigningProvider& out, std::vector<unsigned char>* cache_write) const
bool ExpandHelper(int pos, const SigningProvider& arg, const DescriptorCache* read_cache, std::vector<CScript>& output_scripts, FlatSigningProvider& out, DescriptorCache* write_cache) const
{
std::vector<std::pair<CPubKey, KeyOriginInfo>> entries;
entries.reserve(m_pubkey_args.size());
@ -442,27 +471,12 @@ public:
// Construct temporary data in `entries` and `subscripts`, to avoid producing output in case of failure.
for (const auto& p : m_pubkey_args) {
entries.emplace_back();
// If we have a cache, we don't need GetPubKey to compute the public key.
// Pass in nullptr to signify only origin info is desired.
if (!p->GetPubKey(pos, arg, cache_read ? nullptr : &entries.back().first, entries.back().second)) return false;
if (cache_read) {
// Cached expanded public key exists, use it.
if (cache_read->size() == 0) return false;
bool compressed = ((*cache_read)[0] == 0x02 || (*cache_read)[0] == 0x03) && cache_read->size() >= 33;
bool uncompressed = ((*cache_read)[0] == 0x04) && cache_read->size() >= 65;
if (!(compressed || uncompressed)) return false;
CPubKey pubkey(cache_read->begin(), cache_read->begin() + (compressed ? 33 : 65));
entries.back().first = pubkey;
*cache_read = cache_read->subspan(compressed ? 33 : 65);
}
if (cache_write) {
cache_write->insert(cache_write->end(), entries.back().first.begin(), entries.back().first.end());
}
if (!p->GetPubKey(pos, arg, entries.back().first, entries.back().second, read_cache, write_cache)) return false;
}
std::vector<CScript> subscripts;
if (m_subdescriptor_arg) {
FlatSigningProvider subprovider;
if (!m_subdescriptor_arg->ExpandHelper(pos, arg, cache_read, subscripts, subprovider, cache_write)) return false;
if (!m_subdescriptor_arg->ExpandHelper(pos, arg, read_cache, subscripts, subprovider, write_cache)) return false;
out = Merge(out, subprovider);
}
@ -486,15 +500,14 @@ public:
return true;
}
bool Expand(int pos, const SigningProvider& provider, std::vector<CScript>& output_scripts, FlatSigningProvider& out, std::vector<unsigned char>* cache = nullptr) const final
bool Expand(int pos, const SigningProvider& provider, std::vector<CScript>& output_scripts, FlatSigningProvider& out, DescriptorCache* write_cache = nullptr) const final
{
return ExpandHelper(pos, provider, nullptr, output_scripts, out, cache);
return ExpandHelper(pos, provider, nullptr, output_scripts, out, write_cache);
}
bool ExpandFromCache(int pos, const std::vector<unsigned char>& cache, std::vector<CScript>& output_scripts, FlatSigningProvider& out) const final
bool ExpandFromCache(int pos, const DescriptorCache& read_cache, std::vector<CScript>& output_scripts, FlatSigningProvider& out) const final
{
Span<const unsigned char> span = MakeSpan(cache);
return ExpandHelper(pos, DUMMY_SIGNING_PROVIDER, &span, output_scripts, out, nullptr) && span.size() == 0;
return ExpandHelper(pos, DUMMY_SIGNING_PROVIDER, &read_cache, output_scripts, out, nullptr);
}
void ExpandPrivate(int pos, const SigningProvider& provider, FlatSigningProvider& out) const final

8
src/script/descriptor.h
View File

@ -96,18 +96,18 @@ struct Descriptor {
* @param[in] provider The provider to query for private keys in case of hardened derivation.
* @param[out] output_scripts The expanded scriptPubKeys.
* @param[out] out Scripts and public keys necessary for solving the expanded scriptPubKeys (may be equal to `provider`).
* @param[out] cache Cache data necessary to evaluate the descriptor at this point without access to private keys.
* @param[out] write_cache Cache data necessary to evaluate the descriptor at this point without access to private keys.
*/
virtual bool Expand(int pos, const SigningProvider& provider, std::vector<CScript>& output_scripts, FlatSigningProvider& out, std::vector<unsigned char>* cache = nullptr) const = 0;
virtual bool Expand(int pos, const SigningProvider& provider, std::vector<CScript>& output_scripts, FlatSigningProvider& out, DescriptorCache* write_cache = nullptr) const = 0;
/** Expand a descriptor at a specified position using cached expansion data.
*
* @param[in] pos The position at which to expand the descriptor. If IsRange() is false, this is ignored.
* @param[in] cache Cached expansion data.
* @param[in] read_cache Cached expansion data.
* @param[out] output_scripts The expanded scriptPubKeys.
* @param[out] out Scripts and public keys necessary for solving the expanded scriptPubKeys (may be equal to `provider`).
*/
virtual bool ExpandFromCache(int pos, const std::vector<unsigned char>& cache, std::vector<CScript>& output_scripts, FlatSigningProvider& out) const = 0;
virtual bool ExpandFromCache(int pos, const DescriptorCache& read_cache, std::vector<CScript>& output_scripts, FlatSigningProvider& out) const = 0;
/** Expand the private key for a descriptor at a specified position, if possible.
*

6
src/test/descriptor_tests.cpp
View File

@ -135,14 +135,14 @@ void DoCheck(const std::string& prv, const std::string& pub, int flags, const st
// Evaluate the descriptor selected by `t` in poisition `i`.
FlatSigningProvider script_provider, script_provider_cached;
std::vector<CScript> spks, spks_cached;
std::vector<unsigned char> cache;
BOOST_CHECK((t ? parse_priv : parse_pub)->Expand(i, key_provider, spks, script_provider, &cache));
DescriptorCache desc_cache;
BOOST_CHECK((t ? parse_priv : parse_pub)->Expand(i, key_provider, spks, script_provider, &desc_cache));
// Compare the output with the expected result.
BOOST_CHECK_EQUAL(spks.size(), ref.size());
// Try to expand again using cached data, and compare.
BOOST_CHECK(parse_pub->ExpandFromCache(i, cache, spks_cached, script_provider_cached));
BOOST_CHECK(parse_pub->ExpandFromCache(i, desc_cache, spks_cached, script_provider_cached));
BOOST_CHECK(spks == spks_cached);
BOOST_CHECK(script_provider.pubkeys == script_provider_cached.pubkeys);
BOOST_CHECK(script_provider.scripts == script_provider_cached.scripts);