Fix Several Bugs in the fuzz_submodule Causing a lot of False Alarms in the OSS-Fuzz Bug Tracker

fuzzing/fuzz-targets/fuzz_submodule.py

@@ -3,25 +3,16 @@
 import os
 import tempfile
 from configparser import ParsingError
-from utils import is_expected_exception_message, get_max_filename_length
-
-if getattr(sys, "frozen", False) and hasattr(sys, "_MEIPASS"):  # pragma: no cover
-    path_to_bundled_git_binary = os.path.abspath(os.path.join(os.path.dirname(__file__), "git"))
-    os.environ["GIT_PYTHON_GIT_EXECUTABLE"] = path_to_bundled_git_binary
-
+from utils import (
+    setup_git_environment,
+    handle_exception,
+    get_max_filename_length,
+)
+
+# Setup the git environment
+setup_git_environment()
 from git import Repo, GitCommandError, InvalidGitRepositoryError
 
-if not sys.warnoptions:  # pragma: no cover
-    # The warnings filter below can be overridden by passing the -W option
-    # to the Python interpreter command line or setting the `PYTHONWARNINGS` environment variable.
-    import warnings
-    import logging
-
-    # Fuzzing data causes some modules to generate a large number of warnings
-    # which are not usually interesting and make the test output hard to read, so we ignore them.
-    warnings.simplefilter("ignore")
-    logging.getLogger().setLevel(logging.ERROR)
-
 
 def TestOneInput(data):
     fdp = atheris.FuzzedDataProvider(data)
@@ -35,12 +26,13 @@ def TestOneInput(data):
                 sub_repo = Repo.init(submodule_temp_dir, bare=fdp.ConsumeBool())
                 sub_repo.index.commit(fdp.ConsumeUnicodeNoSurrogates(fdp.ConsumeIntInRange(1, 512)))
 
-                submodule_name = f"submodule_{fdp.ConsumeUnicodeNoSurrogates(fdp.ConsumeIntInRange(1, 512))}"
+                submodule_name = fdp.ConsumeUnicodeNoSurrogates(
+                    fdp.ConsumeIntInRange(1, max(1, get_max_filename_length(repo.working_tree_dir)))
+                )
                 submodule_path = os.path.join(repo.working_tree_dir, submodule_name)
-                submodule_url = sub_repo.git_dir
 
-                submodule = repo.create_submodule(submodule_name, submodule_path, url=submodule_url)
-                repo.index.commit(f"Added submodule {submodule_name}")
+                submodule = repo.create_submodule(submodule_name, submodule_path, url=sub_repo.git_dir)
+                repo.index.commit("Added submodule")
 
                 with submodule.config_writer() as writer:
                     key_length = fdp.ConsumeIntInRange(1, max(1, fdp.remaining_bytes()))
@@ -88,18 +80,11 @@ def TestOneInput(data):
             BrokenPipeError,
         ):
             return -1
-        except ValueError as e:
-            expected_messages = [
-                "SHA is empty",
-                "Reference at",
-                "embedded null byte",
-                "This submodule instance does not exist anymore",
-                "cmd stdin was empty",
-            ]
-            if is_expected_exception_message(e, expected_messages):
+        except Exception as e:
+            if isinstance(e, ValueError) and "embedded null byte" in str(e):
                 return -1
             else:
-                raise e
+                return handle_exception(e)
 
 
 def main():

fuzzing/fuzz-targets/utils.py

@@ -1,6 +1,9 @@
 import atheris  # pragma: no cover
 import os  # pragma: no cover
-from typing import List  # pragma: no cover
+import re  # pragma: no cover
+import traceback  # pragma: no cover
+import sys  # pragma: no cover
+from typing import Set, Tuple, List  # pragma: no cover
 
 
 @atheris.instrument_func
@@ -35,3 +38,85 @@ def get_max_filename_length(path: str) -> int:  # pragma: no cover
         int: The maximum filename length.
     """
     return os.pathconf(path, "PC_NAME_MAX")
+
+
+@atheris.instrument_func
+def read_lines_from_file(file_path: str) -> list:
+    """Read lines from a file and return them as a list."""
+    try:
+        with open(file_path, "r") as f:
+            return [line.strip() for line in f if line.strip()]
+    except FileNotFoundError:
+        print(f"File not found: {file_path}")
+        return []
+    except IOError as e:
+        print(f"Error reading file {file_path}: {e}")
+        return []
+
+
+@atheris.instrument_func
+def load_exception_list(file_path: str = "explicit-exceptions-list.txt") -> Set[Tuple[str, str]]:
+    """Load and parse the exception list from a default or specified file."""
+    try:
+        bundle_dir = os.path.dirname(os.path.abspath(__file__))
+        full_path = os.path.join(bundle_dir, file_path)
+        lines = read_lines_from_file(full_path)
+        exception_list: Set[Tuple[str, str]] = set()
+        for line in lines:
+            match = re.match(r"(.+):(\d+):", line)
+            if match:
+                file_path: str = match.group(1).strip()
+                line_number: str = str(match.group(2).strip())
+                exception_list.add((file_path, line_number))
+        return exception_list
+    except Exception as e:
+        print(f"Error loading exception list: {e}")
+        return set()
+
+
+@atheris.instrument_func
+def match_exception_with_traceback(exception_list: Set[Tuple[str, str]], exc_traceback) -> bool:
+    """Match exception traceback with the entries in the exception list."""
+    for filename, lineno, _, _ in traceback.extract_tb(exc_traceback):
+        for file_pattern, line_pattern in exception_list:
+            # Ensure filename and line_number are strings for regex matching
+            if re.fullmatch(file_pattern, filename) and re.fullmatch(line_pattern, str(lineno)):
+                return True
+    return False
+
+
+@atheris.instrument_func
+def check_exception_against_list(exc_traceback, exception_file: str = "explicit-exceptions-list.txt") -> bool:
+    """Check if the exception traceback matches any entry in the exception list."""
+    exception_list = load_exception_list(exception_file)
+    return match_exception_with_traceback(exception_list, exc_traceback)
+
+
+@atheris.instrument_func
+def handle_exception(e: Exception) -> int:
+    """Encapsulate exception handling logic for reusability."""
+    exc_traceback = e.__traceback__
+    if check_exception_against_list(exc_traceback):
+        return -1
+    else:
+        raise e
+
+
+@atheris.instrument_func
+def setup_git_environment() -> None:
+    """Set up the environment variables for Git."""
+    bundle_dir = os.path.dirname(os.path.abspath(__file__))
+    if getattr(sys, "frozen", False) and hasattr(sys, "_MEIPASS"):  # pragma: no cover
+        bundled_git_binary_path = os.path.join(bundle_dir, "git")
+        os.environ["GIT_PYTHON_GIT_EXECUTABLE"] = bundled_git_binary_path
+
+    if not sys.warnoptions:  # pragma: no cover
+        # The warnings filter below can be overridden by passing the -W option
+        # to the Python interpreter command line or setting the `PYTHONWARNINGS` environment variable.
+        import warnings
+        import logging
+
+        # Fuzzing data causes some modules to generate a large number of warnings
+        # which are not usually interesting and make the test output hard to read, so we ignore them.
+        warnings.simplefilter("ignore")
+        logging.getLogger().setLevel(logging.ERROR)

fuzzing/oss-fuzz-scripts/build.sh

@@ -15,5 +15,5 @@ find "$SRC" -maxdepth 1 \
 
 # Build fuzzers in $OUT.
 find "$SRC/gitpython/fuzzing" -name 'fuzz_*.py' -print0 | while IFS= read -r -d '' fuzz_harness; do
-  compile_python_fuzzer "$fuzz_harness" --add-binary="$(command -v git):."
+  compile_python_fuzzer "$fuzz_harness" --add-binary="$(command -v git):." --add-data="$SRC/explicit-exceptions-list.txt:."
 done

fuzzing/oss-fuzz-scripts/container-environment-bootstrap.sh

@@ -91,6 +91,17 @@ create_seed_corpora_zips "$WORK/qa-assets/gitpython/corpora"
 
 prepare_dictionaries_for_fuzz_targets "$WORK/qa-assets/gitpython/dictionaries" "$SRC/gitpython/fuzzing"
 
+pushd "$SRC/gitpython/"
+# Search for 'raise' and 'assert' statements in Python files within GitPython's source code and submodules, saving the
+# matched file path, line number, and line content to a file named 'explicit-exceptions-list.txt'.
+# This file can then be used by fuzz harnesses to check exception tracebacks and filter out explicitly raised or otherwise
+# anticipated exceptions to reduce false positive test failures.
+
+git grep -n --recurse-submodules -e '\braise\b' -e '\bassert\b' -- '*.py' -- ':!setup.py' -- ':!test/**' -- ':!fuzzing/**' > "$SRC/explicit-exceptions-list.txt"
+
+popd
+
+
 # The OSS-Fuzz base image has outdated dependencies by default so we upgrade them below.
 python3 -m pip install --upgrade pip
 # Upgrade to the latest versions known to work at the time the below changes were introduced:

pyproject.toml

@@ -78,6 +78,10 @@ lint.unfixable = [
 "test/**" = [
     "B018",  # useless-expression
 ]
+"fuzzing/fuzz-targets/**" = [
+  "E402",  # environment setup must happen before the `git` module is imported, thus cannot happen at top of file
+]
+
 
 [tool.codespell]
 ignore-words-list="gud,doesnt"