Merge bitcoin/bitcoin#26567: Wallet: estimate the size of signed inputs using descriptors

10546a569c6c96a5ec1b9708abf9ff5c8644f669 wallet: accurately account for the size of the witness stack (Antoine Poinsot)
9b7ec393b82ca9d7ada77d06e0835df0386a8b85 wallet: use descriptor satisfaction size to estimate inputs size (Antoine Poinsot)
8d870a98731e8db5ecc614bb5f7c064cbf30c7f4 script/signingprovider: introduce a MultiSigningProvider (Antoine Poinsot)
fa7c46b503f0b69630f55dc43021d2099e3515ba descriptor: introduce a method to get the satisfaction size (Antoine Poinsot)
bdba7667d2d65f31484760a8e8420c488fc5f801 miniscript: introduce a helper to get the maximum witness size (Antoine Poinsot)
4ab382c2cdb09fb4056711b4336807845cbe1ad5 miniscript: make GetStackSize independent of P2WSH context (Antoine Poinsot)

Pull request description:

  The wallet currently estimates the size of a signed input by doing a dry run of the signing logic. This is unnecessary since all outputs we can sign for can be represented by a descriptor, and we can derive the size of a satisfaction ("signature") directly from the descriptor itself.
  In addition, the current approach does not generalize well: dry runs of the signing logic are only possible for the most basic scripts. See for instance the discussion in #24149 around that.

  This introduces a method to get the maximum size of a satisfaction from a descriptor, and makes the wallet use that instead of the dry-run.

ACKs for top commit:
  sipa:
    utACK 10546a569c6c96a5ec1b9708abf9ff5c8644f669
  achow101:
    re-ACK 10546a569c6c96a5ec1b9708abf9ff5c8644f669

Tree-SHA512: 43ed1529fbd30af709d903c8c5063235e8c6a03b500bc8f144273d6184e23a53edf0fea9ef898ed57d8a40d73208b5d935cc73b94a24fad3ad3c63b3b2027174

5 files changed, 327 insertions, 11 deletions

diff --git a/src/script/descriptor.cpp b/src/script/descriptor.cpp
index 436ea9c093..2f3f2c7a1d 100644
--- a/src/script/descriptor.cpp
+++ b/src/script/descriptor.cpp
@@ -22,6 +22,7 @@
 #include <util/vector.h>
 
 #include <memory>
+#include <numeric>
 #include <optional>
 #include <string>
 #include <vector>
@@ -706,6 +707,19 @@ public:
     }
 
     std::optional<OutputType> GetOutputType() const override { return std::nullopt; }
+
+    std::optional<int64_t> ScriptSize() const override { return {}; }
+
+    /** A helper for MaxSatisfactionWeight.
+     *
+     * @param use_max_sig Whether to assume ECDSA signatures will have a high-r.
+     * @return The maximum size of the satisfaction in raw bytes (with no witness meaning).
+     */
+    virtual std::optional<int64_t> MaxSatSize(bool use_max_sig) const { return {}; }
+
+    std::optional<int64_t> MaxSatisfactionWeight(bool) const override { return {}; }
+
+    std::optional<int64_t> MaxSatisfactionElems() const override { return {}; }
 };
 
 /** A parsed addr(A) descriptor. */
@@ -725,6 +739,8 @@ public:
     }
     bool IsSingleType() const final { return true; }
     bool ToPrivateString(const SigningProvider& arg, std::string& out) const final { return false; }
+
+    std::optional<int64_t> ScriptSize() const override { return GetScriptForDestination(m_destination).size(); }
 };
 
 /** A parsed raw(H) descriptor. */
@@ -746,6 +762,8 @@ public:
     }
     bool IsSingleType() const final { return true; }
     bool ToPrivateString(const SigningProvider& arg, std::string& out) const final { return false; }
+
+    std::optional<int64_t> ScriptSize() const override { return m_script.size(); }
 };
 
 /** A parsed pk(P) descriptor. */
@@ -766,6 +784,21 @@ protected:
 public:
     PKDescriptor(std::unique_ptr<PubkeyProvider> prov, bool xonly = false) : DescriptorImpl(Vector(std::move(prov)), "pk"), m_xonly(xonly) {}
     bool IsSingleType() const final { return true; }
+
+    std::optional<int64_t> ScriptSize() const override {
+        return 1 + (m_xonly ? 32 : m_pubkey_args[0]->GetSize()) + 1;
+    }
+
+    std::optional<int64_t> MaxSatSize(bool use_max_sig) const override {
+        const auto ecdsa_sig_size = use_max_sig ? 72 : 71;
+        return 1 + (m_xonly ? 65 : ecdsa_sig_size);
+    }
+
+    std::optional<int64_t> MaxSatisfactionWeight(bool use_max_sig) const override {
+        return *MaxSatSize(use_max_sig) * WITNESS_SCALE_FACTOR;
+    }
+
+    std::optional<int64_t> MaxSatisfactionElems() const override { return 1; }
 };
 
 /** A parsed pkh(P) descriptor. */
@@ -782,6 +815,19 @@ public:
     PKHDescriptor(std::unique_ptr<PubkeyProvider> prov) : DescriptorImpl(Vector(std::move(prov)), "pkh") {}
     std::optional<OutputType> GetOutputType() const override { return OutputType::LEGACY; }
     bool IsSingleType() const final { return true; }
+
+    std::optional<int64_t> ScriptSize() const override { return 1 + 1 + 1 + 20 + 1 + 1; }
+
+    std::optional<int64_t> MaxSatSize(bool use_max_sig) const override {
+        const auto sig_size = use_max_sig ? 72 : 71;
+        return 1 + sig_size + 1 + m_pubkey_args[0]->GetSize();
+    }
+
+    std::optional<int64_t> MaxSatisfactionWeight(bool use_max_sig) const override {
+        return *MaxSatSize(use_max_sig) * WITNESS_SCALE_FACTOR;
+    }
+
+    std::optional<int64_t> MaxSatisfactionElems() const override { return 2; }
 };
 
 /** A parsed wpkh(P) descriptor. */
@@ -798,6 +844,19 @@ public:
     WPKHDescriptor(std::unique_ptr<PubkeyProvider> prov) : DescriptorImpl(Vector(std::move(prov)), "wpkh") {}
     std::optional<OutputType> GetOutputType() const override { return OutputType::BECH32; }
     bool IsSingleType() const final { return true; }
+
+    std::optional<int64_t> ScriptSize() const override { return 1 + 1 + 20; }
+
+    std::optional<int64_t> MaxSatSize(bool use_max_sig) const override {
+        const auto sig_size = use_max_sig ? 72 : 71;
+        return (1 + sig_size + 1 + 33);
+    }
+
+    std::optional<int64_t> MaxSatisfactionWeight(bool use_max_sig) const override {
+        return MaxSatSize(use_max_sig);
+    }
+
+    std::optional<int64_t> MaxSatisfactionElems() const override { return 2; }
 };
 
 /** A parsed combo(P) descriptor. */
@@ -842,6 +901,24 @@ protected:
 public:
     MultisigDescriptor(int threshold, std::vector<std::unique_ptr<PubkeyProvider>> providers, bool sorted = false) : DescriptorImpl(std::move(providers), sorted ? "sortedmulti" : "multi"), m_threshold(threshold), m_sorted(sorted) {}
     bool IsSingleType() const final { return true; }
+
+    std::optional<int64_t> ScriptSize() const override {
+        const auto n_keys = m_pubkey_args.size();
+        auto op = [](int64_t acc, const std::unique_ptr<PubkeyProvider>& pk) { return acc + 1 + pk->GetSize();};
+        const auto pubkeys_size{std::accumulate(m_pubkey_args.begin(), m_pubkey_args.end(), int64_t{0}, op)};
+        return 1 + BuildScript(n_keys).size() + BuildScript(m_threshold).size() + pubkeys_size;
+    }
+
+    std::optional<int64_t> MaxSatSize(bool use_max_sig) const override {
+        const auto sig_size = use_max_sig ? 72 : 71;
+        return (1 + (1 + sig_size) * m_threshold);
+    }
+
+    std::optional<int64_t> MaxSatisfactionWeight(bool use_max_sig) const override {
+        return *MaxSatSize(use_max_sig) * WITNESS_SCALE_FACTOR;
+    }
+
+    std::optional<int64_t> MaxSatisfactionElems() const override { return 1 + m_threshold; }
 };
 
 /** A parsed (sorted)multi_a(...) descriptor. Always uses x-only pubkeys. */
@@ -867,6 +944,17 @@ protected:
 public:
     MultiADescriptor(int threshold, std::vector<std::unique_ptr<PubkeyProvider>> providers, bool sorted = false) : DescriptorImpl(std::move(providers), sorted ? "sortedmulti_a" : "multi_a"), m_threshold(threshold), m_sorted(sorted) {}
     bool IsSingleType() const final { return true; }
+
+    std::optional<int64_t> ScriptSize() const override {
+        const auto n_keys = m_pubkey_args.size();
+        return (1 + 32 + 1) * n_keys + BuildScript(m_threshold).size() + 1;
+    }
+
+    std::optional<int64_t> MaxSatSize(bool use_max_sig) const override {
+        return (1 + 65) * m_threshold + (m_pubkey_args.size() - m_threshold);
+    }
+
+    std::optional<int64_t> MaxSatisfactionElems() const override { return m_pubkey_args.size(); }
 };
 
 /** A parsed sh(...) descriptor. */
@@ -879,16 +967,39 @@ protected:
         if (ret.size()) out.scripts.emplace(CScriptID(scripts[0]), scripts[0]);
         return ret;
     }
+
+    bool IsSegwit() const { return m_subdescriptor_args[0]->GetOutputType() == OutputType::BECH32; }
+
 public:
     SHDescriptor(std::unique_ptr<DescriptorImpl> desc) : DescriptorImpl({}, std::move(desc), "sh") {}
 
     std::optional<OutputType> GetOutputType() const override
     {
         assert(m_subdescriptor_args.size() == 1);
-        if (m_subdescriptor_args[0]->GetOutputType() == OutputType::BECH32) return OutputType::P2SH_SEGWIT;
+        if (IsSegwit()) return OutputType::P2SH_SEGWIT;
         return OutputType::LEGACY;
     }
     bool IsSingleType() const final { return true; }
+
+    std::optional<int64_t> ScriptSize() const override { return 1 + 1 + 20 + 1; }
+
+    std::optional<int64_t> MaxSatisfactionWeight(bool use_max_sig) const override {
+        if (const auto sat_size = m_subdescriptor_args[0]->MaxSatSize(use_max_sig)) {
+            if (const auto subscript_size = m_subdescriptor_args[0]->ScriptSize()) {
+                // The subscript is never witness data.
+                const auto subscript_weight = (1 + *subscript_size) * WITNESS_SCALE_FACTOR;
+                // The weight depends on whether the inner descriptor is satisfied using the witness stack.
+                if (IsSegwit()) return subscript_weight + *sat_size;
+                return subscript_weight + *sat_size * WITNESS_SCALE_FACTOR;
+            }
+        }
+        return {};
+    }
+
+    std::optional<int64_t> MaxSatisfactionElems() const override {
+        if (const auto sub_elems = m_subdescriptor_args[0]->MaxSatisfactionElems()) return 1 + *sub_elems;
+        return {};
+    }
 };
 
 /** A parsed wsh(...) descriptor. */
@@ -905,6 +1016,26 @@ public:
     WSHDescriptor(std::unique_ptr<DescriptorImpl> desc) : DescriptorImpl({}, std::move(desc), "wsh") {}
     std::optional<OutputType> GetOutputType() const override { return OutputType::BECH32; }
     bool IsSingleType() const final { return true; }
+
+    std::optional<int64_t> ScriptSize() const override { return 1 + 1 + 32; }
+
+    std::optional<int64_t> MaxSatSize(bool use_max_sig) const override {
+        if (const auto sat_size = m_subdescriptor_args[0]->MaxSatSize(use_max_sig)) {
+            if (const auto subscript_size = m_subdescriptor_args[0]->ScriptSize()) {
+                return GetSizeOfCompactSize(*subscript_size) + *subscript_size + *sat_size;
+            }
+        }
+        return {};
+    }
+
+    std::optional<int64_t> MaxSatisfactionWeight(bool use_max_sig) const override {
+        return MaxSatSize(use_max_sig);
+    }
+
+    std::optional<int64_t> MaxSatisfactionElems() const override {
+        if (const auto sub_elems = m_subdescriptor_args[0]->MaxSatisfactionElems()) return 1 + *sub_elems;
+        return {};
+    }
 };
 
 /** A parsed tr(...) descriptor. */
@@ -958,6 +1089,18 @@ public:
     }
     std::optional<OutputType> GetOutputType() const override { return OutputType::BECH32M; }
     bool IsSingleType() const final { return true; }
+
+    std::optional<int64_t> ScriptSize() const override { return 1 + 1 + 32; }
+
+    std::optional<int64_t> MaxSatisfactionWeight(bool) const override {
+        // FIXME: We assume keypath spend, which can lead to very large underestimations.
+        return 1 + 65;
+    }
+
+    std::optional<int64_t> MaxSatisfactionElems() const override {
+        // FIXME: See above, we assume keypath spend.
+        return 1;
+    }
 };
 
 /* We instantiate Miniscript here with a simple integer as key type.
@@ -1041,6 +1184,17 @@ public:
 
     bool IsSolvable() const override { return true; }
     bool IsSingleType() const final { return true; }
+
+    std::optional<int64_t> ScriptSize() const override { return m_node->ScriptSize(); }
+
+    std::optional<int64_t> MaxSatSize(bool) const override {
+        // For Miniscript we always assume high-R ECDSA signatures.
+        return m_node->GetWitnessSize();
+    }
+
+    std::optional<int64_t> MaxSatisfactionElems() const override {
+        return m_node->GetStackSize();
+    }
 };
 
 /** A parsed rawtr(...) descriptor. */
@@ -1059,6 +1213,18 @@ public:
     RawTRDescriptor(std::unique_ptr<PubkeyProvider> output_key) : DescriptorImpl(Vector(std::move(output_key)), "rawtr") {}
     std::optional<OutputType> GetOutputType() const override { return OutputType::BECH32M; }
     bool IsSingleType() const final { return true; }
+
+    std::optional<int64_t> ScriptSize() const override { return 1 + 1 + 32; }
+
+    std::optional<int64_t> MaxSatisfactionWeight(bool) const override {
+        // We can't know whether there is a script path, so assume key path spend.
+        return 1 + 65;
+    }
+
+    std::optional<int64_t> MaxSatisfactionElems() const override {
+        // See above, we assume keypath spend.
+        return 1;
+    }
 };
 
 ////////////////////////////////////////////////////////////////////////////
diff --git a/src/script/descriptor.h b/src/script/descriptor.h
index c6860c5cf6..caa5d1608d 100644
--- a/src/script/descriptor.h
+++ b/src/script/descriptor.h
@@ -146,6 +146,18 @@ struct Descriptor {
 
     /** @return The OutputType of the scriptPubKey(s) produced by this descriptor. Or nullopt if indeterminate (multiple or none) */
     virtual std::optional<OutputType> GetOutputType() const = 0;
+
+    /** Get the size of the scriptPubKey for this descriptor. */
+    virtual std::optional<int64_t> ScriptSize() const = 0;
+
+    /** Get the maximum size of a satisfaction for this descriptor, in weight units.
+     *
+     * @param use_max_sig Whether to assume ECDSA signatures will have a high-r.
+     */
+    virtual std::optional<int64_t> MaxSatisfactionWeight(bool use_max_sig) const = 0;
+
+    /** Get the maximum size number of stack elements for satisfying this descriptor. */
+    virtual std::optional<int64_t> MaxSatisfactionElems() const = 0;
 };
 
 /** Parse a `descriptor` string. Included private keys are put in `out`.
diff --git a/src/script/miniscript.h b/src/script/miniscript.h
index b58740a125..4c6bd0bb1d 100644
--- a/src/script/miniscript.h
+++ b/src/script/miniscript.h
@@ -337,6 +337,15 @@ struct StackSize {
     StackSize(MaxInt<uint32_t> in_sat, MaxInt<uint32_t> in_dsat) : sat(in_sat), dsat(in_dsat) {};
 };
 
+struct WitnessSize {
+    //! Maximum witness size to satisfy;
+    MaxInt<uint32_t> sat;
+    //! Maximum witness size to dissatisfy;
+    MaxInt<uint32_t> dsat;
+
+    WitnessSize(MaxInt<uint32_t> in_sat, MaxInt<uint32_t> in_dsat) : sat(in_sat), dsat(in_dsat) {};
+};
+
 struct NoDupCheck {};
 
 } // namespace internal
@@ -360,6 +369,8 @@ private:
     const internal::Ops ops;
     //! Cached stack size bounds.
     const internal::StackSize ss;
+    //! Cached witness size bounds.
+    const internal::WitnessSize ws;
     //! Cached expression type (computed by CalcType and fed through SanitizeType).
     const Type typ;
     //! Cached script length (computed by CalcScriptLen).
@@ -846,6 +857,56 @@ private:
         assert(false);
     }
 
+    internal::WitnessSize CalcWitnessSize() const {
+        switch (fragment) {
+            case Fragment::JUST_0: return {{}, 0};
+            case Fragment::JUST_1:
+            case Fragment::OLDER:
+            case Fragment::AFTER: return {0, {}};
+            case Fragment::PK_K: return {1 + 72, 1};
+            case Fragment::PK_H: return {1 + 72 + 1 + 33, 1 + 1 + 33};
+            case Fragment::SHA256:
+            case Fragment::RIPEMD160:
+            case Fragment::HASH256:
+            case Fragment::HASH160: return {1 + 32, {}};
+            case Fragment::ANDOR: {
+                const auto sat{(subs[0]->ws.sat + subs[1]->ws.sat) | (subs[0]->ws.dsat + subs[2]->ws.sat)};
+                const auto dsat{subs[0]->ws.dsat + subs[2]->ws.dsat};
+                return {sat, dsat};
+            }
+            case Fragment::AND_V: return {subs[0]->ws.sat + subs[1]->ws.sat, {}};
+            case Fragment::AND_B: return {subs[0]->ws.sat + subs[1]->ws.sat, subs[0]->ws.dsat + subs[1]->ws.dsat};
+            case Fragment::OR_B: {
+                const auto sat{(subs[0]->ws.dsat + subs[1]->ws.sat) | (subs[0]->ws.sat + subs[1]->ws.dsat)};
+                const auto dsat{subs[0]->ws.dsat + subs[1]->ws.dsat};
+                return {sat, dsat};
+            }
+            case Fragment::OR_C: return {subs[0]->ws.sat | (subs[0]->ws.dsat + subs[1]->ws.sat), {}};
+            case Fragment::OR_D: return {subs[0]->ws.sat | (subs[0]->ws.dsat + subs[1]->ws.sat), subs[0]->ws.dsat + subs[1]->ws.dsat};
+            case Fragment::OR_I: return {(subs[0]->ws.sat + 1 + 1) | (subs[1]->ws.sat + 1), (subs[0]->ws.dsat + 1 + 1) | (subs[1]->ws.dsat + 1)};
+            case Fragment::MULTI: return {k * (1 + 72) + 1, k + 1};
+            case Fragment::WRAP_A:
+            case Fragment::WRAP_N:
+            case Fragment::WRAP_S:
+            case Fragment::WRAP_C: return subs[0]->ws;
+            case Fragment::WRAP_D: return {1 + 1 + subs[0]->ws.sat, 1};
+            case Fragment::WRAP_V: return {subs[0]->ws.sat, {}};
+            case Fragment::WRAP_J: return {subs[0]->ws.sat, 1};
+            case Fragment::THRESH: {
+                auto sats = Vector(internal::MaxInt<uint32_t>(0));
+                for (const auto& sub : subs) {
+                    auto next_sats = Vector(sats[0] + sub->ws.dsat);
+                    for (size_t j = 1; j < sats.size(); ++j) next_sats.push_back((sats[j] + sub->ws.dsat) | (sats[j - 1] + sub->ws.sat));
+                    next_sats.push_back(sats[sats.size() - 1] + sub->ws.sat);
+                    sats = std::move(next_sats);
+                }
+                assert(k <= sats.size());
+                return {sats[k], sats[0]};
+            }
+        }
+        assert(false);
+    }
+
     template<typename Ctx>
     internal::InputResult ProduceInput(const Ctx& ctx) const {
         using namespace internal;
@@ -1148,22 +1209,29 @@ public:
         return true;
     }
 
-    /** Return the maximum number of stack elements needed to satisfy this script non-malleably, including
-     * the script push. */
+    /** Return the maximum number of stack elements needed to satisfy this script non-malleably.
+     * This does not account for the P2WSH script push. */
     std::optional<uint32_t> GetStackSize() const {
         if (!ss.sat.valid) return {};
-        return ss.sat.value + 1;
+        return ss.sat.value;
     }
 
     //! Check the maximum stack size for this script against the policy limit.
     bool CheckStackSize() const {
-        if (const auto ss = GetStackSize()) return *ss - 1 <= MAX_STANDARD_P2WSH_STACK_ITEMS;
+        if (const auto ss = GetStackSize()) return *ss <= MAX_STANDARD_P2WSH_STACK_ITEMS;
         return true;
     }
 
     //! Whether no satisfaction exists for this node.
     bool IsNotSatisfiable() const { return !GetStackSize(); }
 
+    /** Return the maximum size in bytes of a witness to satisfy this script non-malleably. Note this does
+     * not include the witness script push. */
+    std::optional<uint32_t> GetWitnessSize() const {
+        if (!ws.sat.valid) return {};
+        return ws.sat.value;
+    }
+
     //! Return the expression type.
     Type GetType() const { return typ; }
 
@@ -1260,12 +1328,12 @@ public:
     bool operator==(const Node<Key>& arg) const { return Compare(*this, arg) == 0; }
 
     // Constructors with various argument combinations, which bypass the duplicate key check.
-    Node(internal::NoDupCheck, Fragment nt, std::vector<NodeRef<Key>> sub, std::vector<unsigned char> arg, uint32_t val = 0) : fragment(nt), k(val), data(std::move(arg)), subs(std::move(sub)), ops(CalcOps()), ss(CalcStackSize()), typ(CalcType()), scriptlen(CalcScriptLen()) {}
-    Node(internal::NoDupCheck, Fragment nt, std::vector<unsigned char> arg, uint32_t val = 0) : fragment(nt), k(val), data(std::move(arg)), ops(CalcOps()), ss(CalcStackSize()), typ(CalcType()), scriptlen(CalcScriptLen()) {}
-    Node(internal::NoDupCheck, Fragment nt, std::vector<NodeRef<Key>> sub, std::vector<Key> key, uint32_t val = 0) : fragment(nt), k(val), keys(std::move(key)), subs(std::move(sub)), ops(CalcOps()), ss(CalcStackSize()), typ(CalcType()), scriptlen(CalcScriptLen()) {}
-    Node(internal::NoDupCheck, Fragment nt, std::vector<Key> key, uint32_t val = 0) : fragment(nt), k(val), keys(std::move(key)), ops(CalcOps()), ss(CalcStackSize()), typ(CalcType()), scriptlen(CalcScriptLen()) {}
-    Node(internal::NoDupCheck, Fragment nt, std::vector<NodeRef<Key>> sub, uint32_t val = 0) : fragment(nt), k(val), subs(std::move(sub)), ops(CalcOps()), ss(CalcStackSize()), typ(CalcType()), scriptlen(CalcScriptLen()) {}
-    Node(internal::NoDupCheck, Fragment nt, uint32_t val = 0) : fragment(nt), k(val), ops(CalcOps()), ss(CalcStackSize()), typ(CalcType()), scriptlen(CalcScriptLen()) {}
+    Node(internal::NoDupCheck, Fragment nt, std::vector<NodeRef<Key>> sub, std::vector<unsigned char> arg, uint32_t val = 0) : fragment(nt), k(val), data(std::move(arg)), subs(std::move(sub)), ops(CalcOps()), ss(CalcStackSize()), ws(CalcWitnessSize()), typ(CalcType()), scriptlen(CalcScriptLen()) {}
+    Node(internal::NoDupCheck, Fragment nt, std::vector<unsigned char> arg, uint32_t val = 0) : fragment(nt), k(val), data(std::move(arg)), ops(CalcOps()), ss(CalcStackSize()), ws(CalcWitnessSize()), typ(CalcType()), scriptlen(CalcScriptLen()) {}
+    Node(internal::NoDupCheck, Fragment nt, std::vector<NodeRef<Key>> sub, std::vector<Key> key, uint32_t val = 0) : fragment(nt), k(val), keys(std::move(key)), subs(std::move(sub)), ops(CalcOps()), ss(CalcStackSize()), ws(CalcWitnessSize()), typ(CalcType()), scriptlen(CalcScriptLen()) {}
+    Node(internal::NoDupCheck, Fragment nt, std::vector<Key> key, uint32_t val = 0) : fragment(nt), k(val), keys(std::move(key)), ops(CalcOps()), ss(CalcStackSize()), ws(CalcWitnessSize()), typ(CalcType()), scriptlen(CalcScriptLen()) {}
+    Node(internal::NoDupCheck, Fragment nt, std::vector<NodeRef<Key>> sub, uint32_t val = 0) : fragment(nt), k(val), subs(std::move(sub)), ops(CalcOps()), ss(CalcStackSize()), ws(CalcWitnessSize()), typ(CalcType()), scriptlen(CalcScriptLen()) {}
+    Node(internal::NoDupCheck, Fragment nt, uint32_t val = 0) : fragment(nt), k(val), ops(CalcOps()), ss(CalcStackSize()), ws(CalcWitnessSize()), typ(CalcType()), scriptlen(CalcScriptLen()) {}
 
     // Constructors with various argument combinations, which do perform the duplicate key check.
     template <typename Ctx> Node(const Ctx& ctx, Fragment nt, std::vector<NodeRef<Key>> sub, std::vector<unsigned char> arg, uint32_t val = 0) : Node(internal::NoDupCheck{}, nt, std::move(sub), std::move(arg), val) { DuplicateKeyCheck(ctx); }
diff --git a/src/script/signingprovider.cpp b/src/script/signingprovider.cpp
index f3a69e5d21..168b3030cc 100644
--- a/src/script/signingprovider.cpp
+++ b/src/script/signingprovider.cpp
@@ -225,6 +225,61 @@ CKeyID GetKeyForDestination(const SigningProvider& store, const CTxDestination&
     }
     return CKeyID();
 }
+
+void MultiSigningProvider::AddProvider(std::unique_ptr<SigningProvider> provider)
+{
+    m_providers.push_back(std::move(provider));
+}
+
+bool MultiSigningProvider::GetCScript(const CScriptID& scriptid, CScript& script) const
+{
+    for (const auto& provider: m_providers) {
+        if (provider->GetCScript(scriptid, script)) return true;
+    }
+    return false;
+}
+
+bool MultiSigningProvider::GetPubKey(const CKeyID& keyid, CPubKey& pubkey) const
+{
+    for (const auto& provider: m_providers) {
+        if (provider->GetPubKey(keyid, pubkey)) return true;
+    }
+    return false;
+}
+
+
+bool MultiSigningProvider::GetKeyOrigin(const CKeyID& keyid, KeyOriginInfo& info) const
+{
+    for (const auto& provider: m_providers) {
+        if (provider->GetKeyOrigin(keyid, info)) return true;
+    }
+    return false;
+}
+
+bool MultiSigningProvider::GetKey(const CKeyID& keyid, CKey& key) const
+{
+    for (const auto& provider: m_providers) {
+        if (provider->GetKey(keyid, key)) return true;
+    }
+    return false;
+}
+
+bool MultiSigningProvider::GetTaprootSpendData(const XOnlyPubKey& output_key, TaprootSpendData& spenddata) const
+{
+    for (const auto& provider: m_providers) {
+        if (provider->GetTaprootSpendData(output_key, spenddata)) return true;
+    }
+    return false;
+}
+
+bool MultiSigningProvider::GetTaprootBuilder(const XOnlyPubKey& output_key, TaprootBuilder& builder) const
+{
+    for (const auto& provider: m_providers) {
+        if (provider->GetTaprootBuilder(output_key, builder)) return true;
+    }
+    return false;
+}
+
 /*static*/ TaprootBuilder::NodeInfo TaprootBuilder::Combine(NodeInfo&& a, NodeInfo&& b)
 {
     NodeInfo ret;
diff --git a/src/script/signingprovider.h b/src/script/signingprovider.h
index 712e2e73d1..3298376389 100644
--- a/src/script/signingprovider.h
+++ b/src/script/signingprovider.h
@@ -298,4 +298,19 @@ public:
 /** Return the CKeyID of the key involved in a script (if there is a unique one). */
 CKeyID GetKeyForDestination(const SigningProvider& store, const CTxDestination& dest);
 
+/** A signing provider to be used to interface with multiple signing providers at once. */
+class MultiSigningProvider: public SigningProvider {
+    std::vector<std::unique_ptr<SigningProvider>> m_providers;
+
+public:
+    void AddProvider(std::unique_ptr<SigningProvider> provider);
+
+    bool GetCScript(const CScriptID& scriptid, CScript& script) const override;
+    bool GetPubKey(const CKeyID& keyid, CPubKey& pubkey) const override;
+    bool GetKeyOrigin(const CKeyID& keyid, KeyOriginInfo& info) const override;
+    bool GetKey(const CKeyID& keyid, CKey& key) const override;
+    bool GetTaprootSpendData(const XOnlyPubKey& output_key, TaprootSpendData& spenddata) const override;
+    bool GetTaprootBuilder(const XOnlyPubKey& output_key, TaprootBuilder& builder) const override;
+};
+
 #endif // BITCOIN_SCRIPT_SIGNINGPROVIDER_H