Merge bitcoin/bitcoin#20772: fuzz: bolster ExtractDestination(s) checks

a29f522ba4aa71582b54025c5682b4c1687ae9f3 fuzz: bolster ExtractDestination(s) checks (Michael Dietz)

Pull request description:

ACKs for top commit:
  practicalswift:
    Tested ACK a29f522ba4aa71582b54025c5682b4c1687ae9f3

Tree-SHA512: 0fc194edb7b0fce77c7bb725fe65dec7976598edcd53882b5a0eb7cd83281a3ddcd2b3de00282468be659a7e5bc9991eb482816418f55b30e657cdc5a3bd7438

1 files changed, 38 insertions, 10 deletions

diff --git a/src/test/fuzz/script.cpp b/src/test/fuzz/script.cpp
index e87ae5b04b..c8f95c2980 100644
--- a/src/test/fuzz/script.cpp
+++ b/src/test/fuzz/script.cpp
@@ -55,22 +55,45 @@ FUZZ_TARGET_INIT(script, initialize_script)
     }
 
     CTxDestination address;
-    (void)ExtractDestination(script, address);
-
     TxoutType type_ret;
     std::vector<CTxDestination> addresses;
     int required_ret;
-    (void)ExtractDestinations(script, type_ret, addresses, required_ret);
-
-    const FlatSigningProvider signing_provider;
-    (void)InferDescriptor(script, signing_provider);
-
-    (void)IsSegWitOutput(signing_provider, script);
-
-    (void)IsSolvable(signing_provider, script);
+    bool extract_destinations_ret = ExtractDestinations(script, type_ret, addresses, required_ret);
+    bool extract_destination_ret = ExtractDestination(script, address);
+    if (!extract_destinations_ret) {
+        assert(!extract_destination_ret);
+        if (type_ret == TxoutType::MULTISIG) {
+            assert(addresses.empty() && required_ret == 0);
+        } else {
+            assert(type_ret == TxoutType::PUBKEY ||
+                   type_ret == TxoutType::NONSTANDARD ||
+                   type_ret == TxoutType::NULL_DATA);
+        }
+    } else {
+        assert(required_ret >= 1 && required_ret <= 16);
+        assert((unsigned long)required_ret == addresses.size());
+        assert(type_ret == TxoutType::MULTISIG || required_ret == 1);
+    }
+    if (type_ret == TxoutType::NONSTANDARD || type_ret == TxoutType::NULL_DATA) {
+        assert(!extract_destinations_ret);
+    }
+    if (!extract_destination_ret) {
+        assert(type_ret == TxoutType::PUBKEY ||
+               type_ret == TxoutType::NONSTANDARD ||
+               type_ret == TxoutType::NULL_DATA ||
+               type_ret == TxoutType::MULTISIG);
+    } else {
+        assert(address == addresses[0]);
+    }
+    if (type_ret == TxoutType::NONSTANDARD ||
+        type_ret == TxoutType::NULL_DATA ||
+        type_ret == TxoutType::MULTISIG) {
+        assert(!extract_destination_ret);
+    }
 
     TxoutType which_type;
     bool is_standard_ret = IsStandard(script, which_type);
+    assert(type_ret == which_type);
     if (!is_standard_ret) {
         assert(which_type == TxoutType::NONSTANDARD ||
                which_type == TxoutType::NULL_DATA ||
@@ -87,6 +110,11 @@ FUZZ_TARGET_INIT(script, initialize_script)
                which_type == TxoutType::NONSTANDARD);
     }
 
+    const FlatSigningProvider signing_provider;
+    (void)InferDescriptor(script, signing_provider);
+    (void)IsSegWitOutput(signing_provider, script);
+    (void)IsSolvable(signing_provider, script);
+
     (void)RecursiveDynamicUsage(script);
 
     std::vector<std::vector<unsigned char>> solutions;