node: use uint256::FromUserHex for -minimumchainwork parsing

Removes dependency on unsafe and deprecated uint256S.

This makes parsing more strict, by returning an error
when the input contains more than 64 hex digits.

Author: stickies-v

src/node/chainstatemanager_args.cpp

@@ -32,10 +32,11 @@ util::Result<void> ApplyArgsManOptions(const ArgsManager& args, ChainstateManage
     if (auto value{args.GetBoolArg("-checkpoints")}) opts.checkpoints_enabled = *value;
 
     if (auto value{args.GetArg("-minimumchainwork")}) {
-        if (!IsHexNumber(*value)) {
-            return util::Error{strprintf(Untranslated("Invalid non-hex (%s) minimum chain work value specified"), *value)};
+        if (auto min_work{uint256::FromUserHex(*value)}) {
+            opts.minimum_chain_work = UintToArith256(*min_work);
+        } else {
+            return util::Error{strprintf(Untranslated("Invalid minimum work specified (%s), must be up to %d hex digits"), *value, uint256::size() * 2)};
         }
-        opts.minimum_chain_work = UintToArith256(uint256S(*value));
     }
 
     if (auto value{args.GetArg("-assumevalid")}) opts.assumed_valid_block = uint256S(*value);

src/test/validation_chainstatemanager_tests.cpp

@@ -820,7 +820,8 @@ BOOST_FIXTURE_TEST_CASE(chainstatemanager_args, BasicTestingSetup)
     BOOST_CHECK_EQUAL(get_valid_opts({"-nominimumchainwork"}).minimum_chain_work.value().GetCompact(), 0U);
     BOOST_CHECK_EQUAL(get_valid_opts({"-minimumchainwork=0x1234"}).minimum_chain_work.value().GetCompact(), 0x02123400U);
 
-    BOOST_CHECK(!get_opts({"-minimumchainwork=xyz"})); // invalid hex characters
+    BOOST_CHECK(!get_opts({"-minimumchainwork=xyz"}));                                                               // invalid hex characters
+    BOOST_CHECK(!get_opts({"-minimumchainwork=01234567890123456789012345678901234567890123456789012345678901234"})); // > 64 hex chars
 }
 
 BOOST_AUTO_TEST_SUITE_END()

test/functional/feature_minchainwork.py

@@ -110,7 +110,7 @@ def run_test(self):
         self.stop_node(0)
         self.nodes[0].assert_start_raises_init_error(
             ["-minimumchainwork=test"],
-            expected_msg='Error: Invalid non-hex (test) minimum chain work value specified',
+            expected_msg='Error: Invalid minimum work specified (test), must be up to 64 hex digits',
         )