Merge bitcoin/bitcoin#27935: fuzz: call lookup functions before calling `Ban`

fca0a8938e34cb4f6c400e1d1d0be02f027d80c5 ci: remove "--exclude banman" for fuzzing in mac (brunoerg)
f9b286353f79cdb5e55e2ff4ca47d73e14f9da48 fuzz: call lookup functions before calling `Ban` (brunoerg)

Pull request description:

  Fixes #27924

  To not have any discrepancy, it's required to call lookup functions before calling `Ban`. If we don't do it, the assertion `assert(banmap == banmap_read);` may fail because `BanMapFromJson` will call `LookupSubNet` and cause the discrepancy between the banned and the loaded one. It happens especially in MacOS (#27924).

  Also, calling lookup functions before banning is what RPC `setban` does.

ACKs for top commit:
  maflcko:
    lgtm ACK fca0a8938e34cb4f6c400e1d1d0be02f027d80c5
  dergoegge:
    ACK fca0a8938e34cb4f6c400e1d1d0be02f027d80c5

Tree-SHA512: a3d635088a556df4507e65542157f10b41d4f87dce42927b58c3b812f262f4544b6b57f3384eef1097ffdd7c32b8dd1556aae201254960cbfbf48d45551200f7

2 files changed, 18 insertions, 6 deletions

diff --git a/ci/test/00_setup_env_mac_native.sh b/ci/test/00_setup_env_mac_native.sh
index c9f65bf397..439fba16ef 100755
--- a/ci/test/00_setup_env_mac_native.sh
+++ b/ci/test/00_setup_env_mac_native.sh
@@ -15,4 +15,3 @@ export NO_DEPENDS=1
 export OSX_SDK=""
 export CCACHE_MAXSIZE=400M
 export RUN_FUZZ_TESTS=true
-export FUZZ_TESTS_CONFIG="--exclude banman"  # https://github.com/bitcoin/bitcoin/issues/27924
diff --git a/src/test/fuzz/banman.cpp b/src/test/fuzz/banman.cpp
index 3882e0e547..4a040c56de 100644
--- a/src/test/fuzz/banman.cpp
+++ b/src/test/fuzz/banman.cpp
@@ -63,17 +63,28 @@ FUZZ_TARGET(banman, .init = initialize_banman)
         // The complexity is O(N^2), where N is the input size, because each call
         // might call DumpBanlist (or other methods that are at least linear
         // complexity of the input size).
+        bool contains_invalid{false};
         LIMITED_WHILE(fuzzed_data_provider.ConsumeBool(), 300)
         {
             CallOneOf(
                 fuzzed_data_provider,
                 [&] {
-                    ban_man.Ban(ConsumeNetAddr(fuzzed_data_provider),
-                                ConsumeBanTimeOffset(fuzzed_data_provider), fuzzed_data_provider.ConsumeBool());
+                    CNetAddr net_addr{ConsumeNetAddr(fuzzed_data_provider)};
+                    const std::optional<CNetAddr>& addr{LookupHost(net_addr.ToStringAddr(), /*fAllowLookup=*/false)};
+                    if (addr.has_value() && addr->IsValid()) {
+                        net_addr = *addr;
+                    } else {
+                        contains_invalid = true;
+                    }
+                    ban_man.Ban(net_addr, ConsumeBanTimeOffset(fuzzed_data_provider), fuzzed_data_provider.ConsumeBool());
                 },
                 [&] {
-                    ban_man.Ban(ConsumeSubNet(fuzzed_data_provider),
-                                ConsumeBanTimeOffset(fuzzed_data_provider), fuzzed_data_provider.ConsumeBool());
+                    CSubNet subnet{ConsumeSubNet(fuzzed_data_provider)};
+                    subnet = LookupSubNet(subnet.ToString());
+                    if (!subnet.IsValid()) {
+                        contains_invalid = true;
+                    }
+                    ban_man.Ban(subnet, ConsumeBanTimeOffset(fuzzed_data_provider), fuzzed_data_provider.ConsumeBool());
                 },
                 [&] {
                     ban_man.ClearBanned();
@@ -109,7 +120,9 @@ FUZZ_TARGET(banman, .init = initialize_banman)
             BanMan ban_man_read{banlist_file, /*client_interface=*/nullptr, /*default_ban_time=*/0};
             banmap_t banmap_read;
             ban_man_read.GetBanned(banmap_read);
-            assert(banmap == banmap_read);
+            if (!contains_invalid) {
+                assert(banmap == banmap_read);
+            }
         }
     }
     fs::remove(fs::PathToString(banlist_file + ".json"));