sqlmapproject/sqlmap · error · SqlmapGenericException

missing function 'preprocess(req)' in preprocess script

Error message

missing function 'preprocess(req)' in preprocess script '%s'

What it means

After a successful import, sqlmap inspects all functions of the preprocess module looking for one named exactly 'preprocess' whose signature accepts a single 'req' argument (the callable applied to each HTTP request). If no such function is found, found stays False and this SqlmapGenericException is raised — a contract check that the script exports the required hook with the required signature.

Solutions

1. Define a top-level function `def preprocess(req):` in the script; keep the name and the `req` parameter exactly as required.
2. Make sure the function is defined at module top level, not nested or inside a class, so inspect.getmembers(isfunction) can find it.
3. Avoid renaming the argument; use `def preprocess(req):` rather than an alternate parameter name, since the check matches on 'req'.
4. Copy the official template script from sqlmap's data/ directory as a starting point.

When it happens

Trigger: Thrown at lib/core/option.py:1032 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of sqlmapproject/sqlmap@0a35b20e39 (2026-08-26). Data as JSON: /api/errors/ad5878e71a21fc7c. Report an issue: GitHub.

Appendix: source

Thrown at lib/core/option.py:1032

            except Exception as ex:
                raise SqlmapSyntaxException("cannot import preprocess module '%s' (%s)" % (getUnicode(filename[:-3]), getSafeExString(ex)))

            for name, function in inspect.getmembers(module, inspect.isfunction):
                try:
                    if name == "preprocess" and inspect.getargspec(function).args and all(_ in inspect.getargspec(function).args for _ in ("req",)):
                        found = True

                        kb.preprocessFunctions.append(function)
                        function.__name__ = module.__name__

                        break
                except ValueError:  # Note: https://github.com/sqlmapproject/sqlmap/issues/4357
                    pass

            if not found:
                errMsg = "missing function 'preprocess(req)' "
                errMsg += "in preprocess script '%s'" % script
                raise SqlmapGenericException(errMsg)
            else:
                try:
                    function(_urllib.request.Request("http://localhost"))
                except Exception as ex:
                    tbMsg = traceback.format_exc()

                    if conf.debug:
                        dataToStdout(tbMsg)

                    handle, filename = tempfile.mkstemp(prefix=MKSTEMP_PREFIX.PREPROCESS, suffix=".py")
                    os.close(handle)

                    openFile(filename, "w+").write("#!/usr/bin/env\n\ndef preprocess(req):\n    pass\n")
                    openFile(os.path.join(os.path.dirname(filename), "__init__.py"), "w+").write("pass")

                    errMsg = "function 'preprocess(req)' "
                    errMsg += "in preprocess script '%s' " % script
                    errMsg += "had issues in a test run ('%s'). " % getSafeExString(ex)

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