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Add descriptor expansion cache
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@sipa
sipa committed Nov 28, 2018
1 parent 1eda33a commit 82df4c6
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Showing 3 changed files with 75 additions and 30 deletions.
78 changes: 52 additions & 26 deletions src/script/descriptor.cpp
View file
Original file line number Diff line number Diff line change
Expand Up @@ -40,8 +40,8 @@ struct PubkeyProvider
{
virtual ~PubkeyProvider() = default;

/** Derive a public key. */
virtual bool GetPubKey(int pos, const SigningProvider& arg, CPubKey& key, KeyOriginInfo& info) const = 0;
/** 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;

/** Whether this represent multiple public keys at different positions. */
virtual bool IsRange() const = 0;
Expand All @@ -68,7 +68,7 @@ class OriginPubkeyProvider final : public PubkeyProvider

public:
OriginPubkeyProvider(KeyOriginInfo info, std::unique_ptr<PubkeyProvider> provider) : 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 override
{
if (!m_provider->GetPubKey(pos, arg, key, info)) return false;
std::copy(std::begin(m_origin.fingerprint), std::end(m_origin.fingerprint), info.fingerprint);
Expand All @@ -94,9 +94,9 @@ class ConstPubkeyProvider final : public PubkeyProvider

public:
ConstPubkeyProvider(const CPubKey& pubkey) : 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 override
{
key = m_pubkey;
if (key) *key = m_pubkey;
info.path.clear();
CKeyID keyid = m_pubkey.GetID();
std::copy(keyid.begin(), keyid.begin() + sizeof(info.fingerprint), info.fingerprint);
Expand Down Expand Up @@ -152,26 +152,28 @@ class BIP32PubkeyProvider final : public PubkeyProvider
BIP32PubkeyProvider(const CExtPubKey& extkey, KeyPath path, DeriveType derive) : m_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, KeyOriginInfo& info) const override
{
if (IsHardened()) {
CExtKey extkey;
if (!GetExtKey(arg, extkey)) return false;
for (auto entry : m_path) {
extkey.Derive(extkey, entry);
}
if (m_derive == DeriveType::UNHARDENED) extkey.Derive(extkey, pos);
if (m_derive == DeriveType::HARDENED) extkey.Derive(extkey, pos | 0x80000000UL);
key = extkey.Neuter().pubkey;
} else {
// TODO: optimize by caching
CExtPubKey extkey = m_extkey;
for (auto entry : m_path) {
extkey.Derive(extkey, entry);
if (key) {
if (IsHardened()) {
CExtKey extkey;
if (!GetExtKey(arg, extkey)) return false;
for (auto entry : m_path) {
extkey.Derive(extkey, entry);
}
if (m_derive == DeriveType::UNHARDENED) extkey.Derive(extkey, pos);
if (m_derive == DeriveType::HARDENED) extkey.Derive(extkey, pos | 0x80000000UL);
*key = extkey.Neuter().pubkey;
} else {
// TODO: optimize by caching
CExtPubKey extkey = m_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;
}
if (m_derive == DeriveType::UNHARDENED) extkey.Derive(extkey, pos);
assert(m_derive != DeriveType::HARDENED);
key = extkey.pubkey;
}
CKeyID keyid = m_extkey.pubkey.GetID();
std::copy(keyid.begin(), keyid.begin() + sizeof(info.fingerprint), info.fingerprint);
Expand Down Expand Up @@ -285,20 +287,33 @@ class DescriptorImpl : public Descriptor

bool ToPrivateString(const SigningProvider& arg, std::string& out) const override final { return ToStringHelper(&arg, out, true); }

bool Expand(int pos, const SigningProvider& arg, std::vector<CScript>& output_scripts, FlatSigningProvider& out) const final
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
{
std::vector<std::pair<CPubKey, KeyOriginInfo>> entries;
entries.reserve(m_pubkey_args.size());

// 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 (!p->GetPubKey(pos, arg, entries.back().first, entries.back().second)) return false;
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());
}
}
std::vector<CScript> subscripts;
if (m_script_arg) {
FlatSigningProvider subprovider;
if (!m_script_arg->Expand(pos, arg, subscripts, subprovider)) return false;
if (!m_script_arg->ExpandHelper(pos, arg, cache_read, subscripts, subprovider, cache_write)) return false;
out = Merge(out, subprovider);
}

Expand All @@ -322,6 +337,17 @@ class DescriptorImpl : public Descriptor
}
return true;
}

bool Expand(int pos, const SigningProvider& provider, std::vector<CScript>& output_scripts, FlatSigningProvider& out, std::vector<unsigned char>* cache = nullptr) const final
{
return ExpandHelper(pos, provider, nullptr, output_scripts, out, cache);
}

bool ExpandFromCache(int pos, const std::vector<unsigned char>& 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;
}
};

/** Construct a vector with one element, which is moved into it. */
Expand Down
12 changes: 11 additions & 1 deletion src/script/descriptor.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -48,8 +48,18 @@ struct Descriptor {
* provider: the provider to query for private keys in case of hardened derivation.
* output_script: the expanded scriptPubKeys will be put here.
* out: scripts and public keys necessary for solving the expanded scriptPubKeys will be put here (may be equal to provider).
* cache: vector which will be overwritten with 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) const = 0;
virtual bool Expand(int pos, const SigningProvider& provider, std::vector<CScript>& output_scripts, FlatSigningProvider& out, std::vector<unsigned char>* cache = nullptr) const = 0;

/** Expand a descriptor at a specified position using cached expansion data.
*
* pos: the position at which to expand the descriptor. If IsRange() is false, this is ignored.
* cache: vector from which cached expansion data will be read.
* output_script: the expanded scriptPubKeys will be put here.
* out: scripts and public keys necessary for solving the expanded scriptPubKeys will be put here (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;
};

/** Parse a descriptor string. Included private keys are put in out. Returns nullptr if parsing fails. */
Expand Down
15 changes: 12 additions & 3 deletions src/test/descriptor_tests.cpp
View file
Original file line number Diff line number Diff line change
Expand Up @@ -88,9 +88,18 @@ void Check(const std::string& prv, const std::string& pub, int flags, const std:
const auto& ref = scripts[(flags & RANGE) ? i : 0];
for (int t = 0; t < 2; ++t) {
const FlatSigningProvider& key_provider = (flags & HARDENED) ? keys_priv : keys_pub;
FlatSigningProvider script_provider;
std::vector<CScript> spks;
BOOST_CHECK((t ? parse_priv : parse_pub)->Expand(i, key_provider, spks, script_provider));
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));

// Try to expand again using cached data, and compare.
BOOST_CHECK(parse_pub->ExpandFromCache(i, 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);
BOOST_CHECK(script_provider.origins == script_provider_cached.origins);

BOOST_CHECK_EQUAL(spks.size(), ref.size());
for (size_t n = 0; n < spks.size(); ++n) {
BOOST_CHECK_EQUAL(ref[n], HexStr(spks[n].begin(), spks[n].end()));
Expand Down

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