// Copyright (c) 2018 The Bitcoin Core developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.
#include <script/descriptor.h>
#include <key_io.h>
#include <pubkey.h>
#include <script/script.h>
#include <script/standard.h>
#include <span.h>
#include <util/bip32.h>
#include <util/system.h>
#include <util/strencodings.h>
#include <memory>
#include <string>
#include <vector>
namespace {
////////////////////////////////////////////////////////////////////////////
// Checksum //
////////////////////////////////////////////////////////////////////////////
// This section implements a checksum algorithm for descriptors with the
// following properties:
// * Mistakes in a descriptor string are measured in "symbol errors". The higher
// the number of symbol errors, the harder it is to detect:
// * An error substituting a character from 0123456789()[],'/*abcdefgh@:$%{} for
// another in that set always counts as 1 symbol error.
// * Note that hex encoded keys are covered by these characters. Xprvs and
// xpubs use other characters too, but already have their own checksum
// mechanism.
// * Function names like "multi()" use other characters, but mistakes in
// these would generally result in an unparseable descriptor.
// * A case error always counts as 1 symbol error.
// * Any other 1 character substitution error counts as 1 or 2 symbol errors.
// * Any 1 symbol error is always detected.
// * Any 2 or 3 symbol error in a descriptor of up to 49154 characters is always detected.
// * Any 4 symbol error in a descriptor of up to 507 characters is always detected.
// * Any 5 symbol error in a descriptor of up to 77 characters is always detected.
// * Is optimized to minimize the chance a 5 symbol error in a descriptor up to 387 characters is undetected
// * Random errors have a chance of 1 in 2**40 of being undetected.
//
// These properties are achieved by expanding every group of 3 (non checksum) characters into
// 4 GF(32) symbols, over which a cyclic code is defined.
/*
* Interprets c as 8 groups of 5 bits which are the coefficients of a degree 8 polynomial over GF(32),
* multiplies that polynomial by x, computes its remainder modulo a generator, and adds the constant term val.
*
* This generator is G(x) = x^8 + {30}x^7 + {23}x^6 + {15}x^5 + {14}x^4 + {10}x^3 + {6}x^2 + {12}x + {9}.
* It is chosen to define an cyclic error detecting code which is selected by:
* - Starting from all BCH codes over GF(32) of degree 8 and below, which by construction guarantee detecting
* 3 errors in windows up to 19000 symbols.
* - Taking all those generators, and for degree 7 ones, extend them to degree 8 by adding all degree-1 factors.
* - Selecting just the set of generators that guarantee detecting 4 errors in a window of length 512.
* - Selecting one of those with best worst-case behavior for 5 errors in windows of length up to 512.
*
* The generator and the constants to implement it can be verified using this Sage code:
* B = GF(2) # Binary field
* BP.<b> = B[] # Polynomials over the binary field
* F_mod = b**5 + b**3 + 1
* F.<f> = GF(32, modulus=F_mod, repr='int') # GF(32) definition
* FP.<x> = F[] # Polynomials over GF(32)
* E_mod = x**3 + x + F.fetch_int(8)
* E.<e> = F.extension(E_mod) # Extension field definition
* alpha = e**2743 # Choice of an element in extension field
* for p in divisors(E.order() - 1): # Verify alpha has order 32767.
* assert((alpha**p == 1) == (p % 32767 == 0))
* G = lcm([(alpha**i).minpoly() for i in [1056,1057,1058]] + [x + 1])
* print(G) # Print out the generator
* for i in [1,2,4,8,16]: # Print out {1,2,4,8,16}*(G mod x^8), packed in hex integers.
* v = 0
* for coef in reversed((F.fetch_int(i)*(G % x**8)).coefficients(sparse=True)):
* v = v*32 + coef.integer_representation()
* print("0x%x" % v)
*/
uint64_t PolyMod(uint64_t c, int val)
{
uint8_t c0 = c >> 35;
c = ((c & 0x7ffffffff) << 5) ^ val;
if (c0 & 1) c ^= 0xf5dee51989;
if (c0 & 2) c ^= 0xa9fdca3312;
if (c0 & 4) c ^= 0x1bab10e32d;
if (c0 & 8) c ^= 0x3706b1677a;
if (c0 & 16) c ^= 0x644d626ffd;
return c;
}
std::string DescriptorChecksum(const Span<const char>& span)
{
/** A character set designed such that:
* - The most common 'unprotected' descriptor characters (hex, keypaths) are in the first group of 32.
* - Case errors cause an offset that's a multiple of 32.
* - As many alphabetic characters are in the same group (while following the above restrictions).
*
* If p(x) gives the position of a character c in this character set, every group of 3 characters
* (a,b,c) is encoded as the 4 symbols (p(a) & 31, p(b) & 31, p(c) & 31, (p(a) / 32) + 3 * (p(b) / 32) + 9 * (p(c) / 32).
* This means that changes that only affect the lower 5 bits of the position, or only the higher 2 bits, will just
* affect a single symbol.
*
* As a result, within-group-of-32 errors count as 1 symbol, as do cross-group errors that don't affect
* the position within the groups.
*/
static std::string INPUT_CHARSET =
"0123456789()[],'/*abcdefgh@:$%{}"
"IJKLMNOPQRSTUVWXYZ&+-.;<=>?!^_|~"
"ijklmnopqrstuvwxyzABCDEFGH`#\"\\ ";
/** The character set for the checksum itself (same as bech32). */
static std::string CHECKSUM_CHARSET = "qpzry9x8gf2tvdw0s3jn54khce6mua7l";
uint64_t c = 1;
int cls = 0;
int clscount = 0;
for (auto ch : span) {
auto pos = INPUT_CHARSET.find(ch);
if (pos == std::string::npos) return "";
c = PolyMod(c, pos & 31); // Emit a symbol for the position inside the group, for every character.
cls = cls * 3 + (pos >> 5); // Accumulate the group numbers
if (++clscount == 3) {
// Emit an extra symbol representing the group numbers, for every 3 characters.
c = PolyMod(c, cls);
cls = 0;
clscount = 0;
}
}
if (clscount > 0) c = PolyMod(c, cls);
for (int j = 0; j < 8; ++j) c = PolyMod(c, 0); // Shift further to determine the checksum.
c ^= 1; // Prevent appending zeroes from not affecting the checksum.
std::string ret(8, ' ');
for (int j = 0; j < 8; ++j) ret[j] = CHECKSUM_CHARSET[(c >> (5 * (7 - j))) & 31];
return ret;
}
std::string AddChecksum(const std::string& str) { return str + "#" + DescriptorChecksum(MakeSpan(str)); }
////////////////////////////////////////////////////////////////////////////
// Internal representation //
////////////////////////////////////////////////////////////////////////////
typedef std::vector<uint32_t> KeyPath;
/** Interface for public key objects in descriptors. */
struct PubkeyProvider
{
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;
/** Whether this represent multiple public keys at different positions. */
virtual bool IsRange() const = 0;
/** Get the size of the generated public key(s) in bytes (33 or 65). */
virtual size_t GetSize() const = 0;
/** Get the descriptor string form. */
virtual std::string ToString() const = 0;
/** Get the descriptor string form including private data (if available in arg). */
virtual bool ToPrivateString(const SigningProvider& arg, std::string& out) const = 0;
};
class OriginPubkeyProvider final : public PubkeyProvider
{
KeyOriginInfo m_origin;
std::unique_ptr<PubkeyProvider> m_provider;
std::string OriginString() const
{
return HexStr(std::begin(m_origin.fingerprint), std::end(m_origin.fingerprint)) + FormatHDKeypath(m_origin.path);
}
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
{
if (!m_provider->GetPubKey(pos, arg, key, info)) 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;
}
bool IsRange() const override { return m_provider->IsRange(); }
size_t GetSize() const override { return m_provider->GetSize(); }
std::string ToString() const override { return "[" + OriginString() + "]" + m_provider->ToString(); }
bool ToPrivateString(const SigningProvider& arg, std::string& ret) const override
{
std::string sub;
if (!m_provider->ToPrivateString(arg, sub)) return false;
ret = "[" + OriginString() + "]" + std::move(sub);
return true;
}
};
/** An object representing a parsed constant public key in a descriptor. */
class ConstPubkeyProvider final : public PubkeyProvider
{
CPubKey m_pubkey;
public:
ConstPubkeyProvider(const CPubKey& pubkey) : m_pubkey(pubkey) {}
bool GetPubKey(int pos, const SigningProvider& arg, CPubKey* key, KeyOriginInfo& info) const override
{
if (key) *key = m_pubkey;
info.path.clear();
CKeyID keyid = m_pubkey.GetID();
std::copy(keyid.begin(), keyid.begin() + sizeof(info.fingerprint), info.fingerprint);
return true;
}
bool IsRange() const override { return false; }
size_t GetSize() const override { return m_pubkey.size(); }
std::string ToString() const override { return HexStr(m_pubkey.begin(), m_pubkey.end()); }
bool ToPrivateString(const SigningProvider& arg, std::string& ret) const override
{
CKey key;
if (!arg.GetKey(m_pubkey.GetID(), key)) return false;
ret = EncodeSecret(key);
return true;
}
};
enum class DeriveType {
NO,
UNHARDENED,
HARDENED,
};
/** An object representing a parsed extended public key in a descriptor. */
class BIP32PubkeyProvider final : public PubkeyProvider
{
CExtPubKey m_extkey;
KeyPath m_path;
DeriveType m_derive;
bool GetExtKey(const SigningProvider& arg, CExtKey& ret) const
{
CKey key;
if (!arg.GetKey(m_extkey.pubkey.GetID(), key)) return false;
ret.nDepth = m_extkey.nDepth;
std::copy(m_extkey.vchFingerprint, m_extkey.vchFingerprint + sizeof(ret.vchFingerprint), ret.vchFingerprint);
ret.nChild = m_extkey.nChild;
ret.chaincode = m_extkey.chaincode;
ret.key = key;
return true;
}
bool IsHardened() const
{
if (m_derive == DeriveType::HARDENED) return true;
for (auto entry : m_path) {
if (entry >> 31) return true;
}
return false;
}
public:
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
{
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;
}
}
CKeyID keyid = m_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);
return true;
}
std::string ToString() const override
{
std::string ret = EncodeExtPubKey(m_extkey) + FormatHDKeypath(m_path);
if (IsRange()) {
ret += "/*";
if (m_derive == DeriveType::HARDENED) ret += '\'';
}
return ret;
}
bool ToPrivateString(const SigningProvider& arg, std::string& out) const override
{
CExtKey key;
if (!GetExtKey(arg, key)) return false;
out = EncodeExtKey(key) + FormatHDKeypath(m_path);
if (IsRange()) {
out += "/*";
if (m_derive == DeriveType::HARDENED) out += '\'';
}
return true;
}
};
/** 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).
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;
//! The string name of the descriptor function.
const std::string m_name;
protected:
//! Return a serialization of anything except pubkey and script arguments, to be prepended to those.
virtual std::string ToStringExtra() const { return ""; }
/** 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.
* @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 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.
*/
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) {}
bool IsSolvable() const override
{
if (m_script_arg) {
if (!m_script_arg->IsSolvable()) return false;
}
return true;
}
bool IsRange() const final
{
for (const auto& pubkey : m_pubkey_args) {
if (pubkey->IsRange()) return true;
}
if (m_script_arg) {
if (m_script_arg->IsRange()) return true;
}
return false;
}
bool ToStringHelper(const SigningProvider* arg, std::string& out, bool priv) const
{
std::string extra = ToStringExtra();
size_t pos = extra.size() > 0 ? 1 : 0;
std::string ret = m_name + "(" + extra;
for (const auto& pubkey : m_pubkey_args) {
if (pos++) ret += ",";
std::string tmp;
if (priv) {
if (!pubkey->ToPrivateString(*arg, tmp)) return false;
} else {
tmp = pubkey->ToString();
}
ret += std::move(tmp);
}
if (m_script_arg) {
if (pos++) ret += ",";
std::string tmp;
if (!m_script_arg->ToStringHelper(arg, tmp, priv)) return false;
ret += std::move(tmp);
}
out = std::move(ret) + ")";
return true;
}
std::string ToString() const final
{
std::string ret;
ToStringHelper(nullptr, ret, false);
return AddChecksum(ret);
}
bool ToPrivateString(const SigningProvider& arg, std::string& out) const override final
{
bool ret = ToStringHelper(&arg, out, true);
out = AddChecksum(out);
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
{
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, 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->ExpandHelper(pos, arg, cache_read, subscripts, subprovider, cache_write)) return false;
out = Merge(out, subprovider);
}
std::vector<CPubKey> pubkeys;
pubkeys.reserve(entries.size());
for (auto& entry : entries) {
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) {
for (const auto& subscript : subscripts) {
out.scripts.emplace(CScriptID(subscript), subscript);
std::vector<CScript> addscripts = MakeScripts(pubkeys, &subscript, out);
for (auto& addscript : addscripts) {
output_scripts.push_back(std::move(addscript));
}
}
} else {
output_scripts = MakeScripts(pubkeys, nullptr, out);
}
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. */
template<typename T>
std::vector<T> Singleton(T elem)
{
std::vector<T> ret;
ret.emplace_back(std::move(elem));
return ret;
}
/** A parsed addr(A) descriptor. */
class AddressDescriptor final : public DescriptorImpl
{
const CTxDestination m_destination;
protected:
std::string ToStringExtra() const override { return EncodeDestination(m_destination); }
std::vector<CScript> MakeScripts(const std::vector<CPubKey>&, const CScript*, FlatSigningProvider&) const override { return Singleton(GetScriptForDestination(m_destination)); }
public:
AddressDescriptor(CTxDestination destination) : DescriptorImpl({}, {}, "addr"), m_destination(std::move(destination)) {}
bool IsSolvable() const final { return false; }
};
/** A parsed raw(H) descriptor. */
class RawDescriptor final : public DescriptorImpl
{
const CScript m_script;
protected:
std::string ToStringExtra() const override { return HexStr(m_script.begin(), m_script.end()); }
std::vector<CScript> MakeScripts(const std::vector<CPubKey>&, const CScript*, FlatSigningProvider&) const override { return Singleton(m_script); }
public:
RawDescriptor(CScript script) : DescriptorImpl({}, {}, "raw"), m_script(std::move(script)) {}
bool IsSolvable() const final { return false; }
};
/** A parsed pk(P) descriptor. */
class PKDescriptor final : public DescriptorImpl
{
protected:
std::vector<CScript> MakeScripts(const std::vector<CPubKey>& keys, const CScript*, FlatSigningProvider&) const override { return Singleton(GetScriptForRawPubKey(keys[0])); }
public:
PKDescriptor(std::unique_ptr<PubkeyProvider> prov) : DescriptorImpl(Singleton(std::move(prov)), {}, "pk") {}
};
/** A parsed pkh(P) descriptor. */
class PKHDescriptor final : public DescriptorImpl
{
protected:
std::vector<CScript> MakeScripts(const std::vector<CPubKey>& keys, const CScript*, FlatSigningProvider& out) const override
{
CKeyID id = keys[0].GetID();
out.pubkeys.emplace(id, keys[0]);
return Singleton(GetScriptForDestination(id));
}
public:
PKHDescriptor(std::unique_ptr<PubkeyProvider> prov) : DescriptorImpl(Singleton(std::move(prov)), {}, "pkh") {}
};
/** A parsed wpkh(P) descriptor. */
class WPKHDescriptor final : public DescriptorImpl
{
protected:
std::vector<CScript> MakeScripts(const std::vector<CPubKey>& keys, const CScript*, FlatSigningProvider& out) const override
{
CKeyID id = keys[0].GetID();
out.pubkeys.emplace(id, keys[0]);
return Singleton(GetScriptForDestination(WitnessV0KeyHash(id)));
}
public:
WPKHDescriptor(std::unique_ptr<PubkeyProvider> prov) : DescriptorImpl(Singleton(std::move(prov)), {}, "wpkh") {}
};
/** A parsed combo(P) descriptor. */
class ComboDescriptor final : public DescriptorImpl
{
protected:
std::vector<CScript> MakeScripts(const std::vector<CPubKey>& keys, const CScript*, FlatSigningProvider& out) const override
{
std::vector<CScript> ret;
CKeyID id = keys[0].GetID();
out.pubkeys.emplace(id, keys[0]);
ret.emplace_back(GetScriptForRawPubKey(keys[0])); // P2PK
ret.emplace_back(GetScriptForDestination(id)); // P2PKH
if (keys[0].IsCompressed()) {
CScript p2wpkh = GetScriptForDestination(WitnessV0KeyHash(id));
out.scripts.emplace(CScriptID(p2wpkh), p2wpkh);
ret.emplace_back(p2wpkh);
ret.emplace_back(GetScriptForDestination(CScriptID(p2wpkh))); // P2SH-P2WPKH
}
return ret;
}
public:
ComboDescriptor(std::unique_ptr<PubkeyProvider> prov) : DescriptorImpl(Singleton(std::move(prov)), {}, "combo") {}
};
/** A parsed multi(...) descriptor. */
class MultisigDescriptor final : public DescriptorImpl
{
const int m_threshold;
protected:
std::string ToStringExtra() const override { return strprintf("%i", m_threshold); }
std::vector<CScript> MakeScripts(const std::vector<CPubKey>& keys, const CScript*, FlatSigningProvider&) const override { return Singleton(GetScriptForMultisig(m_threshold, keys)); }
public:
MultisigDescriptor(int threshold, std::vector<std::unique_ptr<PubkeyProvider>> providers) : DescriptorImpl(std::move(providers), {}, "multi"), m_threshold(threshold) {}
};
/** A parsed sh(...) descriptor. */
class SHDescriptor final : public DescriptorImpl
{
protected:
std::vector<CScript> MakeScripts(const std::vector<CPubKey>&, const CScript* script, FlatSigningProvider&) const override { return Singleton(GetScriptForDestination(CScriptID(*script))); }
public:
SHDescriptor(std::unique_ptr<DescriptorImpl> desc) : DescriptorImpl({}, std::move(desc), "sh") {}
};
/** A parsed wsh(...) descriptor. */
class WSHDescriptor final : public DescriptorImpl
{
protected:
std::vector<CScript> MakeScripts(const std::vector<CPubKey>&, const CScript* script, FlatSigningProvider&) const override { return Singleton(GetScriptForDestination(WitnessV0ScriptHash(*script))); }
public:
WSHDescriptor(std::unique_ptr<DescriptorImpl> desc) : DescriptorImpl({}, std::move(desc), "wsh") {}
};
////////////////////////////////////////////////////////////////////////////
// Parser //
////////////////////////////////////////////////////////////////////////////
enum class ParseScriptContext {
TOP,
P2SH,
P2WSH,
};
/** Parse a constant. If successful, sp is updated to skip the constant and return true. */
bool Const(const std::string& str, Span<const char>& sp)
{
if ((size_t)sp.size() >= str.size() && std::equal(str.begin(), str.end(), sp.begin())) {
sp = sp.subspan(str.size());
return true;
}
return false;
}
/** Parse a function call. If successful, sp is updated to be the function's argument(s). */
bool Func(const std::string& str, Span<const char>& sp)
{
if ((size_t)sp.size() >= str.size() + 2 && sp[str.size()] == '(' && sp[sp.size() - 1] == ')' && std::equal(str.begin(), str.end(), sp.begin())) {
sp = sp.subspan(str.size() + 1, sp.size() - str.size() - 2);
return true;
}
return false;
}
/** Return the expression that sp begins with, and update sp to skip it. */
Span<const char> Expr(Span<const char>& sp)
{
int level = 0;
auto it = sp.begin();
while (it != sp.end()) {
if (*it == '(') {
++level;
} else if (level && *it == ')') {
--level;
} else if (level == 0 && (*it == ')' || *it == ',')) {
break;
}
++it;
}
Span<const char> ret = sp.first(it - sp.begin());
sp = sp.subspan(it - sp.begin());
return ret;
}
/** Split a string on every instance of sep, returning a vector. */
std::vector<Span<const char>> Split(const Span<const char>& sp, char sep)
{
std::vector<Span<const char>> ret;
auto it = sp.begin();
auto start = it;
while (it != sp.end()) {
if (*it == sep) {
ret.emplace_back(start, it);
start = it + 1;
}
++it;
}
ret.emplace_back(start, it);
return ret;
}
/** Parse a key path, being passed a split list of elements (the first element is ignored). */
NODISCARD bool ParseKeyPath(const std::vector<Span<const char>>& split, KeyPath& out)
{
for (size_t i = 1; i < split.size(); ++i) {
Span<const char> elem = split[i];
bool hardened = false;
if (elem.size() > 0 && (elem[elem.size() - 1] == '\'' || elem[elem.size() - 1] == 'h')) {
elem = elem.first(elem.size() - 1);
hardened = true;
}
uint32_t p;
if (!ParseUInt32(std::string(elem.begin(), elem.end()), &p) || p > 0x7FFFFFFFUL) return false;
out.push_back(p | (((uint32_t)hardened) << 31));
}
return true;
}
/** Parse a public key that excludes origin information. */
std::unique_ptr<PubkeyProvider> ParsePubkeyInner(const Span<const char>& sp, bool permit_uncompressed, FlatSigningProvider& out)
{
auto split = Split(sp, '/');
std::string str(split[0].begin(), split[0].end());
if (split.size() == 1) {
if (IsHex(str)) {
std::vector<unsigned char> data = ParseHex(str);
CPubKey pubkey(data);
if (pubkey.IsFullyValid() && (permit_uncompressed || pubkey.IsCompressed())) return MakeUnique<ConstPubkeyProvider>(pubkey);
}
CKey key = DecodeSecret(str);
if (key.IsValid() && (permit_uncompressed || key.IsCompressed())) {
CPubKey pubkey = key.GetPubKey();
out.keys.emplace(pubkey.GetID(), key);
return MakeUnique<ConstPubkeyProvider>(pubkey);
}
}
CExtKey extkey = DecodeExtKey(str);
CExtPubKey extpubkey = DecodeExtPubKey(str);
if (!extkey.key.IsValid() && !extpubkey.pubkey.IsValid()) return nullptr;
KeyPath path;
DeriveType type = DeriveType::NO;
if (split.back() == MakeSpan("*").first(1)) {
split.pop_back();
type = DeriveType::UNHARDENED;
} else if (split.back() == MakeSpan("*'").first(2) || split.back() == MakeSpan("*h").first(2)) {
split.pop_back();
type = DeriveType::HARDENED;
}
if (!ParseKeyPath(split, path)) return nullptr;
if (extkey.key.IsValid()) {
extpubkey = extkey.Neuter();
out.keys.emplace(extpubkey.pubkey.GetID(), extkey.key);
}
return MakeUnique<BIP32PubkeyProvider>(extpubkey, std::move(path), type);
}
/** Parse a public key including origin information (if enabled). */
std::unique_ptr<PubkeyProvider> ParsePubkey(const Span<const char>& sp, bool permit_uncompressed, FlatSigningProvider& out)
{
auto origin_split = Split(sp, ']');
if (origin_split.size() > 2) return nullptr;
if (origin_split.size() == 1) return ParsePubkeyInner(origin_split[0], permit_uncompressed, out);
if (origin_split[0].size() < 1 || origin_split[0][0] != '[') return nullptr;
auto slash_split = Split(origin_split[0].subspan(1), '/');
if (slash_split[0].size() != 8) return nullptr;
std::string fpr_hex = std::string(slash_split[0].begin(), slash_split[0].end());
if (!IsHex(fpr_hex)) return nullptr;
auto fpr_bytes = ParseHex(fpr_hex);
KeyOriginInfo info;
static_assert(sizeof(info.fingerprint) == 4, "Fingerprint must be 4 bytes");
assert(fpr_bytes.size() == 4);
std::copy(fpr_bytes.begin(), fpr_bytes.end(), info.fingerprint);
if (!ParseKeyPath(slash_split, info.path)) return nullptr;
auto provider = ParsePubkeyInner(origin_split[1], permit_uncompressed, out);
if (!provider) return nullptr;
return MakeUnique<OriginPubkeyProvider>(std::move(info), std::move(provider));
}
/** Parse a script in a particular context. */
std::unique_ptr<DescriptorImpl> ParseScript(Span<const char>& sp, ParseScriptContext ctx, FlatSigningProvider& out)
{
auto expr = Expr(sp);
if (Func("pk", expr)) {
auto pubkey = ParsePubkey(expr, ctx != ParseScriptContext::P2WSH, out);
if (!pubkey) return nullptr;
return MakeUnique<PKDescriptor>(std::move(pubkey));
}
if (Func("pkh", expr)) {
auto pubkey = ParsePubkey(expr, ctx != ParseScriptContext::P2WSH, out);
if (!pubkey) return nullptr;
return MakeUnique<PKHDescriptor>(std::move(pubkey));
}
if (ctx == ParseScriptContext::TOP && Func("combo", expr)) {
auto pubkey = ParsePubkey(expr, true, out);
if (!pubkey) return nullptr;
return MakeUnique<ComboDescriptor>(std::move(pubkey));
}
if (Func("multi", expr)) {
auto threshold = Expr(expr);
uint32_t thres;
std::vector<std::unique_ptr<PubkeyProvider>> providers;
if (!ParseUInt32(std::string(threshold.begin(), threshold.end()), &thres)) return nullptr;
size_t script_size = 0;
while (expr.size()) {
if (!Const(",", expr)) return nullptr;
auto arg = Expr(expr);
auto pk = ParsePubkey(arg, ctx != ParseScriptContext::P2WSH, out);
if (!pk) return nullptr;
script_size += pk->GetSize() + 1;
providers.emplace_back(std::move(pk));
}
if (providers.size() < 1 || providers.size() > 16 || thres < 1 || thres > providers.size()) return nullptr;
if (ctx == ParseScriptContext::TOP) {
if (providers.size() > 3) return nullptr; // Not more than 3 pubkeys for raw multisig
}
if (ctx == ParseScriptContext::P2SH) {
if (script_size + 3 > 520) return nullptr; // Enforce P2SH script size limit
}
return MakeUnique<MultisigDescriptor>(thres, std::move(providers));
}
if (ctx != ParseScriptContext::P2WSH && Func("wpkh", expr)) {
auto pubkey = ParsePubkey(expr, false, out);
if (!pubkey) return nullptr;
return MakeUnique<WPKHDescriptor>(std::move(pubkey));
}
if (ctx == ParseScriptContext::TOP && Func("sh", expr)) {
auto desc = ParseScript(expr, ParseScriptContext::P2SH, out);
if (!desc || expr.size()) return nullptr;
return MakeUnique<SHDescriptor>(std::move(desc));
}
if (ctx != ParseScriptContext::P2WSH && Func("wsh", expr)) {
auto desc = ParseScript(expr, ParseScriptContext::P2WSH, out);
if (!desc || expr.size()) return nullptr;
return MakeUnique<WSHDescriptor>(std::move(desc));
}
if (ctx == ParseScriptContext::TOP && Func("addr", expr)) {
CTxDestination dest = DecodeDestination(std::string(expr.begin(), expr.end()));
if (!IsValidDestination(dest)) return nullptr;
return MakeUnique<AddressDescriptor>(std::move(dest));
}
if (ctx == ParseScriptContext::TOP && Func("raw", expr)) {
std::string str(expr.begin(), expr.end());
if (!IsHex(str)) return nullptr;
auto bytes = ParseHex(str);
return MakeUnique<RawDescriptor>(CScript(bytes.begin(), bytes.end()));
}
return nullptr;
}
std::unique_ptr<PubkeyProvider> InferPubkey(const CPubKey& pubkey, ParseScriptContext, const SigningProvider& provider)
{
std::unique_ptr<PubkeyProvider> key_provider = MakeUnique<ConstPubkeyProvider>(pubkey);
KeyOriginInfo info;
if (provider.GetKeyOrigin(pubkey.GetID(), info)) {
return MakeUnique<OriginPubkeyProvider>(std::move(info), std::move(key_provider));
}
return key_provider;
}
std::unique_ptr<DescriptorImpl> InferScript(const CScript& script, ParseScriptContext ctx, const SigningProvider& provider)
{
std::vector<std::vector<unsigned char>> data;
txnouttype txntype = Solver(script, data);
if (txntype == TX_PUBKEY) {
CPubKey pubkey(data[0].begin(), data[0].end());
if (pubkey.IsValid()) {
return MakeUnique<PKDescriptor>(InferPubkey(pubkey, ctx, provider));
}
}
if (txntype == TX_PUBKEYHASH) {
uint160 hash(data[0]);
CKeyID keyid(hash);
CPubKey pubkey;
if (provider.GetPubKey(keyid, pubkey)) {
return MakeUnique<PKHDescriptor>(InferPubkey(pubkey, ctx, provider));
}
}
if (txntype == TX_WITNESS_V0_KEYHASH && ctx != ParseScriptContext::P2WSH) {
uint160 hash(data[0]);
CKeyID keyid(hash);
CPubKey pubkey;
if (provider.GetPubKey(keyid, pubkey)) {
return MakeUnique<WPKHDescriptor>(InferPubkey(pubkey, ctx, provider));
}
}
if (txntype == TX_MULTISIG) {
std::vector<std::unique_ptr<PubkeyProvider>> providers;
for (size_t i = 1; i + 1 < data.size(); ++i) {
CPubKey pubkey(data[i].begin(), data[i].end());
providers.push_back(InferPubkey(pubkey, ctx, provider));
}
return MakeUnique<MultisigDescriptor>((int)data[0][0], std::move(providers));
}
if (txntype == TX_SCRIPTHASH && ctx == ParseScriptContext::TOP) {
uint160 hash(data[0]);
CScriptID scriptid(hash);
CScript subscript;
if (provider.GetCScript(scriptid, subscript)) {
auto sub = InferScript(subscript, ParseScriptContext::P2SH, provider);
if (sub) return MakeUnique<SHDescriptor>(std::move(sub));
}
}
if (txntype == TX_WITNESS_V0_SCRIPTHASH && ctx != ParseScriptContext::P2WSH) {
CScriptID scriptid;
CRIPEMD160().Write(data[0].data(), data[0].size()).Finalize(scriptid.begin());
CScript subscript;
if (provider.GetCScript(scriptid, subscript)) {
auto sub = InferScript(subscript, ParseScriptContext::P2WSH, provider);
if (sub) return MakeUnique<WSHDescriptor>(std::move(sub));
}
}
CTxDestination dest;
if (ExtractDestination(script, dest)) {
if (GetScriptForDestination(dest) == script) {
return MakeUnique<AddressDescriptor>(std::move(dest));
}
}
return MakeUnique<RawDescriptor>(script);
}
} // namespace
std::unique_ptr<Descriptor> Parse(const std::string& descriptor, FlatSigningProvider& out, bool require_checksum)
{
Span<const char> sp(descriptor.data(), descriptor.size());
// Checksum checks
auto check_split = Split(sp, '#');
if (check_split.size() > 2) return nullptr; // Multiple '#' symbols
if (check_split.size() == 1 && require_checksum) return nullptr; // Missing checksum
if (check_split.size() == 2) {
if (check_split[1].size() != 8) return nullptr; // Unexpected length for checksum
auto checksum = DescriptorChecksum(check_split[0]);
if (checksum.empty()) return nullptr; // Invalid characters in payload
if (!std::equal(checksum.begin(), checksum.end(), check_split[1].begin())) return nullptr; // Checksum mismatch
}
sp = check_split[0];
auto ret = ParseScript(sp, ParseScriptContext::TOP, out);
if (sp.size() == 0 && ret) return std::unique_ptr<Descriptor>(std::move(ret));
return nullptr;
}
std::unique_ptr<Descriptor> InferDescriptor(const CScript& script, const SigningProvider& provider)
{
return InferScript(script, ParseScriptContext::TOP, provider);
}