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Merge #14934: Descriptor expansion cache clarifications

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2e68ffaf20 [doc] descriptor: explain GetPubKey() usage with cached public key (Sjors Provoost)
2290269759 scripted-diff: rename DescriptorImpl m_script_arg to m_subdescriptor_arg (Sjors Provoost)

Pull request description:

  I found the name `m_script_arg` to be confusing while reviewing https://github.com/bitcoin/bitcoin/pull/14646#discussion_r240677238. @sipa let me know if `m_subdescriptor_arg` is completely wrong.

  I also added an explanation of why we call `GetPubKey` when we don't ask it for a public key.

ACKs for top commit:
  laanwj:
    ACK 2e68ffaf20

Tree-SHA512: 06698e9a91cdda93c043a82732793f0ad3cd91daa2513565953e9fa048d5573322fb534e9d0ea9ab736e6366be5921e2b8699c4f4b3693edab48039aaae06f78
This commit is contained in:
Wladimir J. van der Laan 2019-08-14 13:30:23 +02:00
commit e7df1ecd17
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GPG key ID: 1E4AED62986CD25D
2 changed files with 21 additions and 17 deletions
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32
src/script/descriptor.cpp
View file

@ -335,10 +335,12 @@ public:
/** Base class for all Descriptor implementations. */
class DescriptorImpl : public Descriptor
{
//! Public key arguments for this descriptor (size 1 for PK, PKH, WPKH; any size of Multisig).
//! Public key arguments for this descriptor (size 1 for PK, PKH, WPKH; any size for Multisig).
const std::vector<std::unique_ptr<PubkeyProvider>> m_pubkey_args;
//! The sub-descriptor argument (nullptr for everything but SH and WSH).
const std::unique_ptr<DescriptorImpl> m_script_arg;
//! In doc/descriptors.m this is referred to as SCRIPT expressions sh(SCRIPT)
//! and wsh(SCRIPT), and distinct from KEY expressions and ADDR expressions.
const std::unique_ptr<DescriptorImpl> m_subdescriptor_arg;
//! The string name of the descriptor function.
const std::string m_name;
@ -349,10 +351,10 @@ protected:
/** A helper function to construct the scripts for this descriptor.
*
* This function is invoked once for every CScript produced by evaluating
* m_script_arg, or just once in case m_script_arg is nullptr.
* m_subdescriptor_arg, or just once in case m_subdescriptor_arg is nullptr.
* @param pubkeys The evaluations of the m_pubkey_args field.
* @param script The evaluation of m_script_arg (or nullptr when m_script_arg is nullptr).
* @param script The evaluation of m_subdescriptor_arg (or nullptr when m_subdescriptor_arg is nullptr).
* @param out A FlatSigningProvider to put scripts or public keys in that are necessary to the solver.
* The script arguments to this function are automatically added, as is the origin info of the provided pubkeys.
* @return A vector with scriptPubKeys for this descriptor.
@ -360,12 +362,12 @@ protected:
virtual std::vector<CScript> MakeScripts(const std::vector<CPubKey>& pubkeys, const CScript* script, FlatSigningProvider& out) const = 0;
public:
DescriptorImpl(std::vector<std::unique_ptr<PubkeyProvider>> pubkeys, std::unique_ptr<DescriptorImpl> script, const std::string& name) : m_pubkey_args(std::move(pubkeys)), m_script_arg(std::move(script)), m_name(name) {}
DescriptorImpl(std::vector<std::unique_ptr<PubkeyProvider>> pubkeys, std::unique_ptr<DescriptorImpl> script, const std::string& name) : m_pubkey_args(std::move(pubkeys)), m_subdescriptor_arg(std::move(script)), m_name(name) {}
bool IsSolvable() const override
{
if (m_script_arg) {
if (!m_script_arg->IsSolvable()) return false;
if (m_subdescriptor_arg) {
if (!m_subdescriptor_arg->IsSolvable()) return false;
}
return true;
}
@ -375,8 +377,8 @@ public:
for (const auto& pubkey : m_pubkey_args) {
if (pubkey->IsRange()) return true;
}
if (m_script_arg) {
if (m_script_arg->IsRange()) return true;
if (m_subdescriptor_arg) {
if (m_subdescriptor_arg->IsRange()) return true;
}
return false;
}
@ -396,10 +398,10 @@ public:
}
ret += std::move(tmp);
}
if (m_script_arg) {
if (m_subdescriptor_arg) {
if (pos++) ret += ",";
std::string tmp;
if (!m_script_arg->ToStringHelper(arg, tmp, priv)) return false;
if (!m_subdescriptor_arg->ToStringHelper(arg, tmp, priv)) return false;
ret += std::move(tmp);
}
out = std::move(ret) + ")";
@ -428,6 +430,8 @@ 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.
@ -444,9 +448,9 @@ public:
}
}
std::vector<CScript> subscripts;
if (m_script_arg) {
if (m_subdescriptor_arg) {
FlatSigningProvider subprovider;
if (!m_script_arg->ExpandHelper(pos, arg, cache_read, subscripts, subprovider, cache_write)) return false;
if (!m_subdescriptor_arg->ExpandHelper(pos, arg, cache_read, subscripts, subprovider, cache_write)) return false;
out = Merge(out, subprovider);
}
@ -456,7 +460,7 @@ public:
pubkeys.push_back(entry.first);
out.origins.emplace(entry.first.GetID(), std::make_pair<CPubKey, KeyOriginInfo>(CPubKey(entry.first), std::move(entry.second)));
}
if (m_script_arg) {
if (m_subdescriptor_arg) {
for (const auto& subscript : subscripts) {
out.scripts.emplace(CScriptID(subscript), subscript);
std::vector<CScript> addscripts = MakeScripts(pubkeys, &subscript, out);

6
src/script/descriptor.h
View file

@ -47,9 +47,9 @@ struct Descriptor {
*
* pos: the position at which to expand the descriptor. If IsRange() is false, this is ignored.
* provider: the provider to query for private keys in case of hardened derivation.
* output_script: the expanded scriptPubKeys will be put here.
* output_scripts: 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.
* 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, std::vector<unsigned char>* cache = nullptr) const = 0;
@ -57,7 +57,7 @@ struct Descriptor {
*
* 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.
* output_scripts: 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;