descriptors: Check result of InferPubkey

InferPubkey can return a nullptr, so check it's result before continuing
with creating the inferred descriptor.

Author: achow101

src/script/descriptor.cpp

@@ -1491,13 +1491,17 @@ struct KeyParser {
         if (miniscript::IsTapscript(m_script_ctx) && end - begin == 32) {
             XOnlyPubKey pubkey;
             std::copy(begin, end, pubkey.begin());
-            m_keys.push_back(InferPubkey(pubkey.GetEvenCorrespondingCPubKey(), ParseContext(), *m_in));
-            return key;
+            if (auto pubkey_provider = InferPubkey(pubkey.GetEvenCorrespondingCPubKey(), ParseContext(), *m_in)) {
+                m_keys.push_back(std::move(pubkey_provider));
+                return key;
+            }
         } else if (!miniscript::IsTapscript(m_script_ctx)) {
-            CPubKey pubkey{begin, end};
+            CPubKey pubkey(begin, end);
             if (pubkey.IsValidNonHybrid()) {
-                m_keys.push_back(InferPubkey(pubkey, ParseContext(), *m_in));
-                return key;
+                if (auto pubkey_provider = InferPubkey(pubkey, ParseContext(), *m_in)) {
+                    m_keys.push_back(std::move(pubkey_provider));
+                    return key;
+                }
             }
         }
         return {};
@@ -1512,9 +1516,11 @@ struct KeyParser {
         CKeyID keyid(hash);
         CPubKey pubkey;
         if (m_in->GetPubKey(keyid, pubkey)) {
-            Key key = m_keys.size();
-            m_keys.push_back(InferPubkey(pubkey, ParseContext(), *m_in));
-            return key;
+            if (auto pubkey_provider = InferPubkey(pubkey, ParseContext(), *m_in)) {
+                Key key = m_keys.size();
+                m_keys.push_back(std::move(pubkey_provider));
+                return key;
+            }
         }
         return {};
     }
@@ -1850,32 +1856,44 @@ std::unique_ptr<DescriptorImpl> InferScript(const CScript& script, ParseScriptCo
     if (txntype == TxoutType::PUBKEY && (ctx == ParseScriptContext::TOP || ctx == ParseScriptContext::P2SH || ctx == ParseScriptContext::P2WSH)) {
         CPubKey pubkey(data[0]);
         if (pubkey.IsValidNonHybrid()) {
-            return std::make_unique<PKDescriptor>(InferPubkey(pubkey, ctx, provider));
+            if (auto pubkey_provider = InferPubkey(pubkey, ctx, provider)) {
+                return std::make_unique<PKDescriptor>(std::move(pubkey_provider));
+            }
         }
     }
     if (txntype == TxoutType::PUBKEYHASH && (ctx == ParseScriptContext::TOP || ctx == ParseScriptContext::P2SH || ctx == ParseScriptContext::P2WSH)) {
         uint160 hash(data[0]);
         CKeyID keyid(hash);
         CPubKey pubkey;
         if (provider.GetPubKey(keyid, pubkey)) {
-            return std::make_unique<PKHDescriptor>(InferPubkey(pubkey, ctx, provider));
+            if (auto pubkey_provider = InferPubkey(pubkey, ctx, provider)) {
+                return std::make_unique<PKHDescriptor>(std::move(pubkey_provider));
+            }
         }
     }
     if (txntype == TxoutType::WITNESS_V0_KEYHASH && (ctx == ParseScriptContext::TOP || ctx == ParseScriptContext::P2SH)) {
         uint160 hash(data[0]);
         CKeyID keyid(hash);
         CPubKey pubkey;
         if (provider.GetPubKey(keyid, pubkey)) {
-            return std::make_unique<WPKHDescriptor>(InferPubkey(pubkey, ctx, provider));
+            if (auto pubkey_provider = InferPubkey(pubkey, ctx, provider)) {
+                return std::make_unique<WPKHDescriptor>(std::move(pubkey_provider));
+            }
         }
     }
     if (txntype == TxoutType::MULTISIG && (ctx == ParseScriptContext::TOP || ctx == ParseScriptContext::P2SH || ctx == ParseScriptContext::P2WSH)) {
+        bool ok = true;
         std::vector<std::unique_ptr<PubkeyProvider>> providers;
         for (size_t i = 1; i + 1 < data.size(); ++i) {
             CPubKey pubkey(data[i]);
-            providers.push_back(InferPubkey(pubkey, ctx, provider));
+            if (auto pubkey_provider = InferPubkey(pubkey, ctx, provider)) {
+                providers.push_back(std::move(pubkey_provider));
+            } else {
+                ok = false;
+                break;
+            }
         }
-        return std::make_unique<MultisigDescriptor>((int)data[0][0], std::move(providers));
+        if (ok) return std::make_unique<MultisigDescriptor>((int)data[0][0], std::move(providers));
     }
     if (txntype == TxoutType::SCRIPTHASH && ctx == ParseScriptContext::TOP) {
         uint160 hash(data[0]);