require dnsresolve when DNS_NAME consumers are enabled

bbot/scanner/preset/preset.py

@@ -478,6 +478,33 @@ def bake(self, scan=None):
             for output_module in self.default_output_modules:
                 baked_preset.add_module(output_module, module_type="output", raise_error=False)
 
+        # dnsresolve is the intercept module that resolves every event, tags wildcards/unresolved,
+        # and rewrites wildcard hits to `_wildcard.parent`. Modules that watch DNS_NAME depend on
+        # those tags to filter false positives; without it, brute-force and passive-enum modules
+        # emit unverified and wildcard-tainted names. This catches all three explicit opt-outs:
+        # `-em dnsresolve`, top-level `dnsresolve: false`, and `dns.disable: true`. We check the
+        # user actions rather than "dnsresolve in modules" so that internal-module-trimming code
+        # paths (e.g. `--list-module-options` setting `_default_internal_modules = []`) don't trip
+        # the gate -- those aren't real scans, and the user hasn't asked to disable anything.
+        dnsresolve_disabled = (
+            "dnsresolve" in baked_preset.exclude_modules
+            or baked_preset.config.get("dnsresolve", True) is False
+            or baked_preset.config.get("dns", {}).get("disable", False)
+        )
+        if dnsresolve_disabled:
+            dns_name_consumers = sorted(
+                m
+                for m in baked_preset.modules
+                if "DNS_NAME" in baked_preset.preloaded_module(m).get("watched_events", [])
+            )
+            if dns_name_consumers:
+                raise ValidationError(
+                    f"dnsresolve is required by these enabled modules but is disabled: {', '.join(dns_name_consumers)}. "
+                    "Use `dns.minimal: true` (resolves A/AAAA only, skips MX/NS/SRV expansion) "
+                    "if you want to reduce DNS overhead while keeping wildcard and unresolved tagging. "
+                    "If you genuinely want no DNS at all, also disable the modules listed above."
+                )
+
         # create target object
         from bbot.scanner.target import BBOTTarget
 

bbot/test/test_step_1/test_presets.py

@@ -1274,3 +1274,20 @@ def test_preset_file_targets(tmp_path):
     target_inputs5 = set(preset5._target_list)
     assert "nested.evilcorp.com" in target_inputs5
     assert "my_targets.txt" not in target_inputs5
+
+
+def test_preset_dnsresolve_required_by_dns_name_consumers():
+    # gate must fire for all three opt-out paths when any DNS_NAME-watching module is enabled
+    for opt_out in (
+        {"exclude_modules": ["dnsresolve"], "flags": ["subdomain-enum"]},
+        {"config": {"dnsresolve": False}, "flags": ["subdomain-enum"]},
+        {"config": {"dns": {"disable": True}}, "flags": ["subdomain-enum"]},
+    ):
+        with pytest.raises(ValidationError, match="dnsresolve is required"):
+            Preset(**opt_out).bake()
+
+    # dns.minimal keeps dnsresolve in the pipeline -- must NOT fire
+    Preset(flags=["subdomain-enum"], config={"dns": {"minimal": True}}).bake()
+
+    # disabling dnsresolve with no DNS_NAME consumers enabled is allowed
+    Preset(exclude_modules=["dnsresolve"]).bake()