3 files changed, 275 insertions, 2 deletions

diff --git a/src/wallet/scriptpubkeyman.cpp b/src/wallet/scriptpubkeyman.cpp
index 5919783ce1..3e6830a08d 100644
--- a/src/wallet/scriptpubkeyman.cpp
+++ b/src/wallet/scriptpubkeyman.cpp
@@ -999,9 +999,10 @@ bool LegacyScriptPubKeyMan::GetKeyOrigin(const CKeyID& keyID, KeyOriginInfo& inf
     {
         LOCK(cs_KeyStore);
         auto it = mapKeyMetadata.find(keyID);
-        if (it != mapKeyMetadata.end()) {
-            meta = it->second;
+        if (it == mapKeyMetadata.end()) {
+            return false;
         }
+        meta = it->second;
     }
     if (meta.has_key_origin) {
         std::copy(meta.key_origin.fingerprint, meta.key_origin.fingerprint + 4, info.fingerprint);
@@ -1711,6 +1712,258 @@ const std::unordered_set<CScript, SaltedSipHasher> LegacyScriptPubKeyMan::GetScr
     return spks;
 }
 
+std::optional<MigrationData> LegacyScriptPubKeyMan::MigrateToDescriptor()
+{
+    LOCK(cs_KeyStore);
+    if (m_storage.IsLocked()) {
+        return std::nullopt;
+    }
+
+    MigrationData out;
+
+    std::unordered_set<CScript, SaltedSipHasher> spks{GetScriptPubKeys()};
+
+    // Get all key ids
+    std::set<CKeyID> keyids;
+    for (const auto& key_pair : mapKeys) {
+        keyids.insert(key_pair.first);
+    }
+    for (const auto& key_pair : mapCryptedKeys) {
+        keyids.insert(key_pair.first);
+    }
+
+    // Get key metadata and figure out which keys don't have a seed
+    // Note that we do not ignore the seeds themselves because they are considered IsMine!
+    for (auto keyid_it = keyids.begin(); keyid_it != keyids.end();) {
+        const CKeyID& keyid = *keyid_it;
+        const auto& it = mapKeyMetadata.find(keyid);
+        if (it != mapKeyMetadata.end()) {
+            const CKeyMetadata& meta = it->second;
+            if (meta.hdKeypath == "s" || meta.hdKeypath == "m") {
+                keyid_it++;
+                continue;
+            }
+            if (m_hd_chain.seed_id == meta.hd_seed_id || m_inactive_hd_chains.count(meta.hd_seed_id) > 0) {
+                keyid_it = keyids.erase(keyid_it);
+                continue;
+            }
+        }
+        keyid_it++;
+    }
+
+    // keyids is now all non-HD keys. Each key will have its own combo descriptor
+    for (const CKeyID& keyid : keyids) {
+        CKey key;
+        if (!GetKey(keyid, key)) {
+            assert(false);
+        }
+
+        // Get birthdate from key meta
+        uint64_t creation_time = 0;
+        const auto& it = mapKeyMetadata.find(keyid);
+        if (it != mapKeyMetadata.end()) {
+            creation_time = it->second.nCreateTime;
+        }
+
+        // Get the key origin
+        // Maybe this doesn't matter because floating keys here shouldn't have origins
+        KeyOriginInfo info;
+        bool has_info = GetKeyOrigin(keyid, info);
+        std::string origin_str = has_info ? "[" + HexStr(info.fingerprint) + FormatHDKeypath(info.path) + "]" : "";
+
+        // Construct the combo descriptor
+        std::string desc_str = "combo(" + origin_str + HexStr(key.GetPubKey()) + ")";
+        FlatSigningProvider keys;
+        std::string error;
+        std::unique_ptr<Descriptor> desc = Parse(desc_str, keys, error, false);
+        WalletDescriptor w_desc(std::move(desc), creation_time, 0, 0, 0);
+
+        // Make the DescriptorScriptPubKeyMan and get the scriptPubKeys
+        auto desc_spk_man = std::unique_ptr<DescriptorScriptPubKeyMan>(new DescriptorScriptPubKeyMan(m_storage, w_desc));
+        desc_spk_man->AddDescriptorKey(key, key.GetPubKey());
+        desc_spk_man->TopUp();
+        auto desc_spks = desc_spk_man->GetScriptPubKeys();
+
+        // Remove the scriptPubKeys from our current set
+        for (const CScript& spk : desc_spks) {
+            size_t erased = spks.erase(spk);
+            assert(erased == 1);
+            assert(IsMine(spk) == ISMINE_SPENDABLE);
+        }
+
+        out.desc_spkms.push_back(std::move(desc_spk_man));
+    }
+
+    // Handle HD keys by using the CHDChains
+    std::vector<CHDChain> chains;
+    chains.push_back(m_hd_chain);
+    for (const auto& chain_pair : m_inactive_hd_chains) {
+        chains.push_back(chain_pair.second);
+    }
+    for (const CHDChain& chain : chains) {
+        for (int i = 0; i < 2; ++i) {
+            // Skip if doing internal chain and split chain is not supported
+            if (chain.seed_id.IsNull() || (i == 1 && !m_storage.CanSupportFeature(FEATURE_HD_SPLIT))) {
+                continue;
+            }
+            // Get the master xprv
+            CKey seed_key;
+            if (!GetKey(chain.seed_id, seed_key)) {
+                assert(false);
+            }
+            CExtKey master_key;
+            master_key.SetSeed(seed_key);
+
+            // Make the combo descriptor
+            std::string xpub = EncodeExtPubKey(master_key.Neuter());
+            std::string desc_str = "combo(" + xpub + "/0'/" + ToString(i) + "'/*')";
+            FlatSigningProvider keys;
+            std::string error;
+            std::unique_ptr<Descriptor> desc = Parse(desc_str, keys, error, false);
+            uint32_t chain_counter = std::max((i == 1 ? chain.nInternalChainCounter : chain.nExternalChainCounter), (uint32_t)0);
+            WalletDescriptor w_desc(std::move(desc), 0, 0, chain_counter, 0);
+
+            // Make the DescriptorScriptPubKeyMan and get the scriptPubKeys
+            auto desc_spk_man = std::unique_ptr<DescriptorScriptPubKeyMan>(new DescriptorScriptPubKeyMan(m_storage, w_desc));
+            desc_spk_man->AddDescriptorKey(master_key.key, master_key.key.GetPubKey());
+            desc_spk_man->TopUp();
+            auto desc_spks = desc_spk_man->GetScriptPubKeys();
+
+            // Remove the scriptPubKeys from our current set
+            for (const CScript& spk : desc_spks) {
+                size_t erased = spks.erase(spk);
+                assert(erased == 1);
+                assert(IsMine(spk) == ISMINE_SPENDABLE);
+            }
+
+            out.desc_spkms.push_back(std::move(desc_spk_man));
+        }
+    }
+    // Add the current master seed to the migration data
+    if (!m_hd_chain.seed_id.IsNull()) {
+        CKey seed_key;
+        if (!GetKey(m_hd_chain.seed_id, seed_key)) {
+            assert(false);
+        }
+        out.master_key.SetSeed(seed_key);
+    }
+
+    // Handle the rest of the scriptPubKeys which must be imports and may not have all info
+    for (auto it = spks.begin(); it != spks.end();) {
+        const CScript& spk = *it;
+
+        // Get birthdate from script meta
+        uint64_t creation_time = 0;
+        const auto& mit = m_script_metadata.find(CScriptID(spk));
+        if (mit != m_script_metadata.end()) {
+            creation_time = mit->second.nCreateTime;
+        }
+
+        // InferDescriptor as that will get us all the solving info if it is there
+        std::unique_ptr<Descriptor> desc = InferDescriptor(spk, *GetSolvingProvider(spk));
+        // Get the private keys for this descriptor
+        std::vector<CScript> scripts;
+        FlatSigningProvider keys;
+        if (!desc->Expand(0, DUMMY_SIGNING_PROVIDER, scripts, keys)) {
+            assert(false);
+        }
+        std::set<CKeyID> privkeyids;
+        for (const auto& key_orig_pair : keys.origins) {
+            privkeyids.insert(key_orig_pair.first);
+        }
+
+        std::vector<CScript> desc_spks;
+
+        // Make the descriptor string with private keys
+        std::string desc_str;
+        bool watchonly = !desc->ToPrivateString(*this, desc_str);
+        if (watchonly && !m_storage.IsWalletFlagSet(WALLET_FLAG_DISABLE_PRIVATE_KEYS)) {
+            out.watch_descs.push_back({desc->ToString(), creation_time});
+
+            // Get the scriptPubKeys without writing this to the wallet
+            FlatSigningProvider provider;
+            desc->Expand(0, provider, desc_spks, provider);
+        } else {
+            // Make the DescriptorScriptPubKeyMan and get the scriptPubKeys
+            WalletDescriptor w_desc(std::move(desc), creation_time, 0, 0, 0);
+            auto desc_spk_man = std::unique_ptr<DescriptorScriptPubKeyMan>(new DescriptorScriptPubKeyMan(m_storage, w_desc));
+            for (const auto& keyid : privkeyids) {
+                CKey key;
+                if (!GetKey(keyid, key)) {
+                    continue;
+                }
+                desc_spk_man->AddDescriptorKey(key, key.GetPubKey());
+            }
+            desc_spk_man->TopUp();
+            auto desc_spks_set = desc_spk_man->GetScriptPubKeys();
+            desc_spks.insert(desc_spks.end(), desc_spks_set.begin(), desc_spks_set.end());
+
+            out.desc_spkms.push_back(std::move(desc_spk_man));
+        }
+
+        // Remove the scriptPubKeys from our current set
+        for (const CScript& desc_spk : desc_spks) {
+            auto del_it = spks.find(desc_spk);
+            assert(del_it != spks.end());
+            assert(IsMine(desc_spk) != ISMINE_NO);
+            it = spks.erase(del_it);
+        }
+    }
+
+    // Multisigs are special. They don't show up as ISMINE_SPENDABLE unless they are in a P2SH
+    // So we have to check if any of our scripts are a multisig and if so, add the P2SH
+    for (const auto& script_pair : mapScripts) {
+        const CScript script = script_pair.second;
+
+        // Get birthdate from script meta
+        uint64_t creation_time = 0;
+        const auto& it = m_script_metadata.find(CScriptID(script));
+        if (it != m_script_metadata.end()) {
+            creation_time = it->second.nCreateTime;
+        }
+
+        std::vector<std::vector<unsigned char>> sols;
+        TxoutType type = Solver(script, sols);
+        if (type == TxoutType::MULTISIG) {
+            CScript sh_spk = GetScriptForDestination(ScriptHash(script));
+            CTxDestination witdest = WitnessV0ScriptHash(script);
+            CScript witprog = GetScriptForDestination(witdest);
+            CScript sh_wsh_spk = GetScriptForDestination(ScriptHash(witprog));
+
+            // We only want the multisigs that we have not already seen, i.e. they are not watchonly and not spendable
+            // For P2SH, a multisig is not ISMINE_NO when:
+            // * All keys are in the wallet
+            // * The multisig itself is watch only
+            // * The P2SH is watch only
+            // For P2SH-P2WSH, if the script is in the wallet, then it will have the same conditions as P2SH.
+            // For P2WSH, a multisig is not ISMINE_NO when, other than the P2SH conditions:
+            // * The P2WSH script is in the wallet and it is being watched
+            std::vector<std::vector<unsigned char>> keys(sols.begin() + 1, sols.begin() + sols.size() - 1);
+            if (HaveWatchOnly(sh_spk) || HaveWatchOnly(script) || HaveKeys(keys, *this) || (HaveCScript(CScriptID(witprog)) && HaveWatchOnly(witprog))) {
+                // The above emulates IsMine for these 3 scriptPubKeys, so double check that by running IsMine
+                assert(IsMine(sh_spk) != ISMINE_NO || IsMine(witprog) != ISMINE_NO || IsMine(sh_wsh_spk) != ISMINE_NO);
+                continue;
+            }
+            assert(IsMine(sh_spk) == ISMINE_NO && IsMine(witprog) == ISMINE_NO && IsMine(sh_wsh_spk) == ISMINE_NO);
+
+            std::unique_ptr<Descriptor> sh_desc = InferDescriptor(sh_spk, *GetSolvingProvider(sh_spk));
+            out.solvable_descs.push_back({sh_desc->ToString(), creation_time});
+
+            const auto desc = InferDescriptor(witprog, *this);
+            if (desc->IsSolvable()) {
+                std::unique_ptr<Descriptor> wsh_desc = InferDescriptor(witprog, *GetSolvingProvider(witprog));
+                out.solvable_descs.push_back({wsh_desc->ToString(), creation_time});
+                std::unique_ptr<Descriptor> sh_wsh_desc = InferDescriptor(sh_wsh_spk, *GetSolvingProvider(sh_wsh_spk));
+                out.solvable_descs.push_back({sh_wsh_desc->ToString(), creation_time});
+            }
+        }
+    }
+
+    // Make sure that we have accounted for all scriptPubKeys
+    assert(spks.size() == 0);
+    return out;
+}
+
 util::Result<CTxDestination> DescriptorScriptPubKeyMan::GetNewDestination(const OutputType type)
 {
     // Returns true if this descriptor supports getting new addresses. Conditions where we may be unable to fetch them (e.g. locked) are caught later
diff --git a/src/wallet/scriptpubkeyman.h b/src/wallet/scriptpubkeyman.h
index 8de6fd2b7d..19ec277c56 100644
--- a/src/wallet/scriptpubkeyman.h
+++ b/src/wallet/scriptpubkeyman.h
@@ -265,6 +265,8 @@ static const std::unordered_set<OutputType> LEGACY_OUTPUT_TYPES {
     OutputType::BECH32,
 };
 
+class DescriptorScriptPubKeyMan;
+
 class LegacyScriptPubKeyMan : public ScriptPubKeyMan, public FillableSigningProvider
 {
 private:
@@ -511,6 +513,10 @@ public:
 
     std::set<CKeyID> GetKeys() const override;
     const std::unordered_set<CScript, SaltedSipHasher> GetScriptPubKeys() const override;
+
+    /** Get the DescriptorScriptPubKeyMans (with private keys) that have the same scriptPubKeys as this LegacyScriptPubKeyMan.
+     * Does not modify this ScriptPubKeyMan. */
+    std::optional<MigrationData> MigrateToDescriptor();
 };
 
 /** Wraps a LegacyScriptPubKeyMan so that it can be returned in a new unique_ptr. Does not provide privkeys */
diff --git a/src/wallet/walletutil.h b/src/wallet/walletutil.h
index 788d41ceb7..8434d64fb5 100644
--- a/src/wallet/walletutil.h
+++ b/src/wallet/walletutil.h
@@ -104,6 +104,20 @@ public:
     WalletDescriptor() {}
     WalletDescriptor(std::shared_ptr<Descriptor> descriptor, uint64_t creation_time, int32_t range_start, int32_t range_end, int32_t next_index) : descriptor(descriptor), creation_time(creation_time), range_start(range_start), range_end(range_end), next_index(next_index) {}
 };
+
+class CWallet;
+class DescriptorScriptPubKeyMan;
+
+/** struct containing information needed for migrating legacy wallets to descriptor wallets */
+struct MigrationData
+{
+    CExtKey master_key;
+    std::vector<std::pair<std::string, int64_t>> watch_descs;
+    std::vector<std::pair<std::string, int64_t>> solvable_descs;
+    std::vector<std::unique_ptr<DescriptorScriptPubKeyMan>> desc_spkms;
+    std::shared_ptr<CWallet> watchonly_wallet{nullptr};
+    std::shared_ptr<CWallet> solvable_wallet{nullptr};
+};
 } // namespace wallet
 
 #endif // BITCOIN_WALLET_WALLETUTIL_H