Add fuzzer for pickle module

Fuzzes the CPython _pickle C module (Modules/_pickle.c). Dispatches to
four operations: pickle.dumps() with protocols 0–5 over a mix of
container types (bytes, str, int list, tuple, set, frozenset, bytearray,
dict) built from fuzzed data; pickle.loads() driven through restricted
and persistent-load Unpickler subclasses (including a fix_imports/bytes
encoding variant); Pickler.dump() with memo clearing between objects;
and a dumps/loads roundtrip to exercise both sides together.

Author: AdamKorcz

Makefile

@@ -1,8 +1,8 @@
-all : fuzzer-html fuzzer-email fuzzer-httpclient fuzzer-json fuzzer-difflib fuzzer-csv fuzzer-decode fuzzer-ast fuzzer-tarfile fuzzer-tarfile-hypothesis fuzzer-zipfile fuzzer-zipfile-hypothesis fuzzer-re fuzzer-configparser fuzzer-tomllib fuzzer-plistlib fuzzer-xml fuzzer-zoneinfo
+all : fuzzer-html fuzzer-email fuzzer-httpclient fuzzer-json fuzzer-difflib fuzzer-csv fuzzer-decode fuzzer-ast fuzzer-tarfile fuzzer-tarfile-hypothesis fuzzer-zipfile fuzzer-zipfile-hypothesis fuzzer-re fuzzer-configparser fuzzer-tomllib fuzzer-plistlib fuzzer-xml fuzzer-zoneinfo fuzzer-pickle
 
 PYTHON_CONFIG_PATH=$(CPYTHON_INSTALL_PATH)/bin/python3-config
 CXXFLAGS += $(shell $(PYTHON_CONFIG_PATH) --cflags)
-LDFLAGS += -rdynamic $(shell $(PYTHON_CONFIG_PATH) --ldflags --embed)
+LDFLAGS += -rdynamic $(shell $(PYTHON_CONFIG_PATH) --ldflags --embed) $(CPYTHON_MODLIBS) -Wl,--allow-multiple-definition
 
 fuzzer-html:
 	clang++ $(CXXFLAGS) $(LIB_FUZZING_ENGINE) -std=c++17 fuzzer.cpp -DPYTHON_HARNESS_PATH="\"html.py\"" -ldl $(LDFLAGS) -o fuzzer-html
@@ -40,3 +40,6 @@ fuzzer-xml:
 	clang++ $(CXXFLAGS) $(LIB_FUZZING_ENGINE) -std=c++17 fuzzer.cpp -DPYTHON_HARNESS_PATH="\"xml.py\"" -ldl $(LDFLAGS) -o fuzzer-xml
 fuzzer-zoneinfo:
 	clang++ $(CXXFLAGS) $(LIB_FUZZING_ENGINE) -std=c++17 fuzzer.cpp -DPYTHON_HARNESS_PATH="\"zoneinfo.py\"" -ldl $(LDFLAGS) -o fuzzer-zoneinfo
+
+fuzzer-pickle:
+	clang++ $(CXXFLAGS) $(LIB_FUZZING_ENGINE) -std=c++17 fuzzer.cpp -DPYTHON_HARNESS_PATH="\"pickle.py\"" -ldl $(LDFLAGS) -o fuzzer-pickle

fuzz_targets.txt

@@ -7,6 +7,7 @@ email email.py
 html html.py
 httpclient httpclient.py
 json json.py
+pickle pickle.py
 plistlib plist.py
 re re.py
 tarfile tarfile.py

pickle.py

@@ -0,0 +1,139 @@
+from fuzzeddataprovider import FuzzedDataProvider
+import pickle
+import io
+
+MAX_CONTAINER_SIZE = 200  # cap on generated container/string sizes to avoid OOM
+
+# Top-level operation constants for FuzzerRunOne dispatch
+OP_DUMPS = 0
+OP_LOADS = 1
+OP_PICKLER = 2
+OP_ROUNDTRIP = 3
+
+# Container type constants for build_container
+CTYPE_BYTES = 0
+CTYPE_STRING = 1
+CTYPE_INT_LIST = 2
+CTYPE_TUPLE = 3
+CTYPE_SET = 4
+CTYPE_FROZENSET = 5
+CTYPE_BYTEARRAY = 6
+CTYPE_DICT = 7
+
+# Unpickler variant constants for op_loads
+VARIANT_RESTRICTED = 0
+VARIANT_PERSISTENT = 1
+VARIANT_RESTRICTED_FIX_IMPORTS = 2
+
+
+class RestrictedUnpickler(pickle.Unpickler):
+    def find_class(self, module, name):
+        raise pickle.UnpicklingError("restricted")
+
+
+class PersistentUnpickler(pickle.Unpickler):
+    def persistent_load(self, pid):
+        return pid
+
+    def find_class(self, module, name):
+        raise pickle.UnpicklingError("restricted")
+
+
+def build_container(fdp, ctype):
+    n = fdp.ConsumeIntInRange(0, min(fdp.remaining_bytes(), MAX_CONTAINER_SIZE))
+    if ctype == CTYPE_BYTES:
+        return fdp.ConsumeBytes(n)
+    elif ctype == CTYPE_STRING:
+        return fdp.ConsumeUnicode(n)
+    elif ctype == CTYPE_INT_LIST:
+        return fdp.ConsumeIntList(n, 1)
+    elif ctype == CTYPE_TUPLE:
+        return tuple(fdp.ConsumeIntList(n, 1))
+    elif ctype == CTYPE_SET:
+        return set(fdp.ConsumeIntList(n, 1))
+    elif ctype == CTYPE_FROZENSET:
+        return frozenset(fdp.ConsumeIntList(n, 1))
+    elif ctype == CTYPE_BYTEARRAY:
+        return bytearray(fdp.ConsumeBytes(n))
+    elif ctype == CTYPE_DICT:
+        d = {}
+        entries = fdp.ConsumeIntInRange(0, min(n, 64))
+        for _ in range(entries):
+            if fdp.remaining_bytes() == 0:
+                break
+            kn = fdp.ConsumeIntInRange(1, 20)
+            key = fdp.ConsumeUnicode(kn)
+            val = fdp.ConsumeRandomValue()
+            d[key] = val
+        return d
+    return fdp.ConsumeBytes(n)
+
+
+def op_dumps(fdp):
+    ctype = fdp.ConsumeIntInRange(CTYPE_BYTES, CTYPE_DICT)
+    protocol = fdp.ConsumeIntInRange(0, 5)
+    fix_imports = fdp.ConsumeBool()
+    obj = build_container(fdp, ctype)
+    pickle.dumps(obj, protocol=protocol, fix_imports=fix_imports)
+
+
+def op_loads(fdp):
+    variant = fdp.ConsumeIntInRange(VARIANT_RESTRICTED, VARIANT_RESTRICTED_FIX_IMPORTS)
+    data = fdp.ConsumeBytes(fdp.remaining_bytes())
+    bio = io.BytesIO(data)
+    if variant == VARIANT_RESTRICTED:
+        unpickler = RestrictedUnpickler(bio)
+    elif variant == VARIANT_PERSISTENT:
+        unpickler = PersistentUnpickler(bio)
+    else:
+        unpickler = RestrictedUnpickler(bio, fix_imports=True, encoding="bytes")
+    unpickler.load()
+
+
+def op_pickler(fdp):
+    protocol = fdp.ConsumeIntInRange(0, 5)
+    n = (
+        fdp.ConsumeIntInRange(1, min(fdp.remaining_bytes(), MAX_CONTAINER_SIZE))
+        if fdp.remaining_bytes() > 0
+        else 0
+    )
+    if n == 0:
+        return
+    obj1 = fdp.ConsumeIntList(n, 1)
+    s = fdp.ConsumeUnicode(fdp.ConsumeIntInRange(0, MAX_CONTAINER_SIZE))
+    bio = io.BytesIO()
+    p = pickle.Pickler(bio, protocol)
+    p.dump(obj1)
+    p.clear_memo()
+    p.dump(s)
+    bio.getvalue()
+
+
+def op_roundtrip(fdp):
+    ctype = fdp.ConsumeIntInRange(CTYPE_BYTES, CTYPE_DICT)
+    obj = build_container(fdp, ctype)
+    dumped = pickle.dumps(obj)
+    pickle.loads(dumped)
+
+
+# Fuzzes the _pickle C module (Modules/_pickle.c). Exercises pickle.dumps()
+# with protocols 0-5 on various container types (bytes, strings, int lists,
+# tuples, sets, frozensets, bytearrays, dicts), pickle.loads() with
+# restricted and persistent-load unpickler variants, Pickler.dump() with
+# memo clearing, and dumps/loads roundtrips.
+def FuzzerRunOne(FuzzerInput):
+    if len(FuzzerInput) < 1 or len(FuzzerInput) > 0x100000:
+        return
+    fdp = FuzzedDataProvider(FuzzerInput)
+    op = fdp.ConsumeIntInRange(OP_DUMPS, OP_ROUNDTRIP)
+    try:
+        if op == OP_DUMPS:
+            op_dumps(fdp)
+        elif op == OP_LOADS:
+            op_loads(fdp)
+        elif op == OP_PICKLER:
+            op_pickler(fdp)
+        else:
+            op_roundtrip(fdp)
+    except Exception:
+        pass