merge bitcoin#15986: Add checksum to getdescriptorinfo

src/rpc/misc.cpp

@@ -303,7 +303,8 @@ UniValue getdescriptorinfo(const JSONRPCRequest& request)
             }}.ToString() +
             "\nResult:\n"
             "{\n"
-            "  \"descriptor\" : \"desc\",       (string)  The descriptor in canonical form, without private keys\n"
+            "  \"descriptor\" : \"desc\",         (string) The descriptor in canonical form, without private keys\n"
+            "  \"checksum\" : \"chksum\",         (string) The checksum for the input descriptor\n"
             "  \"isrange\" : true|false,        (boolean) Whether the descriptor is ranged\n"
             "  \"issolvable\" : true|false,     (boolean) Whether the descriptor is solvable\n"
             "  \"hasprivatekeys\" : true|false, (boolean) Whether the input descriptor contained at least one private key\n"
@@ -324,6 +325,7 @@ UniValue getdescriptorinfo(const JSONRPCRequest& request)
 
     UniValue result(UniValue::VOBJ);
     result.pushKV("descriptor", desc->ToString());
+    result.pushKV("checksum", GetDescriptorChecksum(request.params[0].get_str()));
     result.pushKV("isrange", desc->IsRange());
     result.pushKV("issolvable", desc->IsSolvable());
     result.pushKV("hasprivatekeys", provider.keys.size() > 0);

src/script/descriptor.cpp

@@ -832,27 +832,42 @@ std::unique_ptr<DescriptorImpl> InferScript(const CScript& script, ParseScriptCo
 
 } // namespace
 
-std::unique_ptr<Descriptor> Parse(const std::string& descriptor, FlatSigningProvider& out, bool require_checksum)
+/** Check a descriptor checksum, and update desc to be the checksum-less part. */
+bool CheckChecksum(Span<const char>& sp, bool require_checksum, std::string* out_checksum = nullptr)
 {
-    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) return false; // Multiple '#' symbols
+    if (check_split.size() == 1 && require_checksum) return false; // Missing checksum
+    if (check_split.size() == 2) {
+        if (check_split[1].size() != 8) return false; // Unexpected length for checksum
+    }
+    auto checksum = DescriptorChecksum(check_split[0]);
+    if (checksum.empty()) return false; // Invalid characters in payload
     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
+        if (!std::equal(checksum.begin(), checksum.end(), check_split[1].begin())) return false; // Checksum mismatch
     }
+    if (out_checksum) *out_checksum = std::move(checksum);
     sp = check_split[0];
+    return true;
+}
 
+std::unique_ptr<Descriptor> Parse(const std::string& descriptor, FlatSigningProvider& out, bool require_checksum)
+{
+    Span<const char> sp(descriptor.data(), descriptor.size());
+    if (!CheckChecksum(sp, require_checksum)) return nullptr;
     auto ret = ParseScript(sp, ParseScriptContext::TOP, out);
     if (sp.size() == 0 && ret) return std::unique_ptr<Descriptor>(std::move(ret));
     return nullptr;
 }
 
+std::string GetDescriptorChecksum(const std::string& descriptor)
+{
+    std::string ret;
+    Span<const char> sp(descriptor.data(), descriptor.size());
+    if (!CheckChecksum(sp, false, &ret)) return "";
+    return ret;
+}
+
 std::unique_ptr<Descriptor> InferDescriptor(const CScript& script, const SigningProvider& provider)
 {
     return InferScript(script, ParseScriptContext::TOP, provider);

src/script/descriptor.h

@@ -72,6 +72,14 @@ struct Descriptor {
  */
 std::unique_ptr<Descriptor> Parse(const std::string& descriptor, FlatSigningProvider& out, bool require_checksum = false);
 
+/** Get the checksum for a descriptor.
+ *
+ * If it already has one, and it is correct, return the checksum in the input.
+ * If it already has one that is wrong, return "".
+ * If it does not already have one, return the checksum that would need to be added.
+ */
+std::string GetDescriptorChecksum(const std::string& descriptor);
+
 /** Find a descriptor for the specified script, using information from provider where possible.
  *
  * A non-ranged descriptor which only generates the specified script will be returned in all