buildroot/package/python-cbor2/0002-CVE-2025-68131.patch

From f1d701cd2c411ee40bb1fe383afe7f365f35abf0 Mon Sep 17 00:00:00 2001
From: Andreas Eriksen <andreer@vespa.ai>
Date: Thu, 18 Dec 2025 16:48:26 +0100
Subject: [PATCH] Merge commit from fork

* track depth of recursive encode/decode, clear shared refs on start

* test that shared refs are cleared on start

* add fix-shared-state-reset to version history

* clear shared state _after_ encode/decode

* use PY_SSIZE_T_MAX to clear shareables list

* use context manager for python decoder depth tracking

* use context manager for python encoder depth tracking

CVE: CVE-2025-68131
Upstream: https://github.com/agronholm/cbor2/commit/f1d701cd2c411ee40bb1fe383afe7f365f35abf0
[thomas: backport, stripped tests and changelog]
Signed-off-by: Thomas Perale <thomas.perale@mind.be>
---
 cbor2/_decoder.py       | 38 +++++++++++++++++-----
 cbor2/_encoder.py       | 44 +++++++++++++++++++++-----
 source/decoder.c        | 28 ++++++++++++++++-
 source/decoder.h        |  1 +
 source/encoder.c        | 23 ++++++++++++--
 source/encoder.h        |  1 +
 6 files changed, 255 insertions(+), 17 deletions(-)

diff --git a/cbor2/_decoder.py b/cbor2/_decoder.py
index 42a97400..b5524920 100644
--- a/cbor2/_decoder.py
+++ b/cbor2/_decoder.py
@@ -5,6 +5,7 @@
 import sys
 from codecs import getincrementaldecoder
 from collections.abc import Callable, Mapping, Sequence
+from contextlib import contextmanager
 from datetime import date, datetime, timedelta, timezone
 from io import BytesIO
 from typing import IO, TYPE_CHECKING, Any, TypeVar, cast, overload
@@ -59,6 +60,7 @@ class CBORDecoder:
         "_immutable",
         "_str_errors",
         "_stringref_namespace",
+        "_decode_depth",
     )
 
     _fp: IO[bytes]
@@ -100,6 +102,7 @@ def __init__(
         self._shareables: list[object] = []
         self._stringref_namespace: list[str | bytes] | None = None
         self._immutable = False
+        self._decode_depth = 0
 
     @property
     def immutable(self) -> bool:
@@ -225,13 +228,33 @@ def _decode(self, immutable: bool = False, unshared: bool = False) -> Any:
             if unshared:
                 self._share_index = old_index
 
+    @contextmanager
+    def _decoding_context(self):
+        """
+        Context manager for tracking decode depth and clearing shared state.
+
+        Shared state is cleared at the end of each top-level decode to prevent
+        shared references from leaking between independent decode operations.
+        Nested calls (from hooks) must preserve the state.
+        """
+        self._decode_depth += 1
+        try:
+            yield
+        finally:
+            self._decode_depth -= 1
+            assert self._decode_depth >= 0
+            if self._decode_depth == 0:
+                self._shareables.clear()
+                self._share_index = None
+
     def decode(self) -> object:
         """
         Decode the next value from the stream.
 
         :raises CBORDecodeError: if there is any problem decoding the stream
         """
-        return self._decode()
+        with self._decoding_context():
+            return self._decode()
 
     def decode_from_bytes(self, buf: bytes) -> object:
         """
@@ -242,12 +265,13 @@ def decode_from_bytes(self, buf: bytes) -> object:
         object needs to be decoded separately from the rest but while still
         taking advantage of the shared value registry.
         """
-        with BytesIO(buf) as fp:
-            old_fp = self.fp
-            self.fp = fp
-            retval = self._decode()
-            self.fp = old_fp
-            return retval
+        with self._decoding_context():
+            with BytesIO(buf) as fp:
+                old_fp = self.fp
+                self.fp = fp
+                retval = self._decode()
+                self.fp = old_fp
+                return retval
 
     @overload
     def _decode_length(self, subtype: int) -> int: ...
diff --git a/cbor2/_encoder.py b/cbor2/_encoder.py
index fe65763d..5b9609c7 100644
--- a/cbor2/_encoder.py
+++ b/cbor2/_encoder.py
@@ -123,6 +123,7 @@ class CBOREncoder:
         "string_referencing",
         "string_namespacing",
         "_string_references",
+        "_encode_depth",
     )
 
     _fp: IO[bytes]
@@ -183,6 +184,7 @@ def __init__(
             int, tuple[object, int | None]
         ] = {}  # indexes used for value sharing
         self._string_references: dict[str | bytes, int] = {}  # indexes used for string references
+        self._encode_depth = 0
         self._encoders = default_encoders.copy()
         if canonical:
             self._encoders.update(canonical_encoders)
@@ -298,6 +300,24 @@ def write(self, data: bytes) -> None:
         """
         self._fp_write(data)
 
+    @contextmanager
+    def _encoding_context(self):
+        """
+        Context manager for tracking encode depth and clearing shared state.
+
+        Shared state is cleared at the end of each top-level encode to prevent
+        shared references from leaking between independent encode operations.
+        Nested calls (from hooks) must preserve the state.
+        """
+        self._encode_depth += 1
+        try:
+            yield
+        finally:
+            self._encode_depth -= 1
+            if self._encode_depth == 0:
+                self._shared_containers.clear()
+                self._string_references.clear()
+
     def encode(self, obj: Any) -> None:
         """
         Encode the given object using CBOR.
@@ -305,6 +325,16 @@ def encode(self, obj: Any) -> None:
         :param obj:
             the object to encode
         """
+        with self._encoding_context():
+            self._encode_value(obj)
+
+    def _encode_value(self, obj: Any) -> None:
+        """
+        Internal fast path for encoding - used by built-in encoders.
+
+        External code should use encode() instead, which properly manages
+        shared state between independent encode operations.
+        """
         obj_type = obj.__class__
         encoder = self._encoders.get(obj_type) or self._find_encoder(obj_type) or self._default
         if not encoder:
@@ -448,7 +478,7 @@ def encode_string(self, value: str) -> None:
     def encode_array(self, value: Sequence[Any]) -> None:
         self.encode_length(4, len(value))
         for item in value:
-            self.encode(item)
+            self._encode_value(item)
 
     @container_encoder
     def encode_map(self, value: Mapping[Any, Any]) -> None:
@@ -454,8 +484,8 @@ def encode_array(self, value: Sequence[Any]) -> None:
     def encode_map(self, value: Mapping[Any, Any]) -> None:
         self.encode_length(5, len(value))
         for key, val in value.items():
-            self.encode(key)
-            self.encode(val)
+            self._encode_value(key)
+            self._encode_value(val)
 
     def encode_sortable_key(self, value: Any) -> tuple[int, bytes]:
         """
@@ -477,10 +507,10 @@ def encode_canonical_map(self, value: Mapping[Any, Any]) -> None:
                 # String referencing requires that the order encoded is
                 # the same as the order emitted so string references are
                 # generated after an order is determined
-                self.encode(realkey)
+                self._encode_value(realkey)
             else:
                 self._fp_write(sortkey[1])
-            self.encode(value)
+            self._encode_value(value)
 
     def encode_semantic(self, value: CBORTag) -> None:
         # Nested string reference domains are distinct
@@ -491,7 +521,7 @@ def encode_semantic(self, value: CBORTag) -> None:
             self._string_references = {}
 
         self.encode_length(6, value.tag)
-        self.encode(value.value)
+        self._encode_value(value.value)
 
         self.string_referencing = old_string_referencing
         self._string_references = old_string_references
@@ -554,7 +584,7 @@ def encode_decimal(self, value: Decimal) -> None:
     def encode_stringref(self, value: str | bytes) -> None:
         # Semantic tag 25
         if not self._stringref(value):
-            self.encode(value)
+            self._encode_value(value)
 
     def encode_rational(self, value: Fraction) -> None:
         # Semantic tag 30
diff --git a/source/decoder.c b/source/decoder.c
index 8b6b842c..b0bdb9a2 100644
--- a/source/decoder.c
+++ b/source/decoder.c
@@ -142,6 +142,7 @@ CBORDecoder_new(PyTypeObject *type, PyObject *args, PyObject *kwargs)
         self->str_errors = PyBytes_FromString("strict");
         self->immutable = false;
         self->shared_index = -1;
+        self->decode_depth = 0;
     }
     return (PyObject *) self;
 error:
@@ -2058,11 +2059,30 @@ decode(CBORDecoderObject *self, DecodeOptions options)
 }
 
 
+// Reset shared state at the end of each top-level decode to prevent
+// shared references from leaking between independent decode operations.
+// Nested calls (from hooks) must preserve the state.
+static inline void
+clear_shareable_state(CBORDecoderObject *self)
+{
+    PyList_SetSlice(self->shareables, 0, PY_SSIZE_T_MAX, NULL);
+    self->shared_index = -1;
+}
+
+
 // CBORDecoder.decode(self) -> obj
 PyObject *
 CBORDecoder_decode(CBORDecoderObject *self)
 {
-    return decode(self, DECODE_NORMAL);
+    PyObject *ret;
+    self->decode_depth++;
+    ret = decode(self, DECODE_NORMAL);
+    self->decode_depth--;
+    assert(self->decode_depth >= 0);
+    if (self->decode_depth == 0) {
+        clear_shareable_state(self);
+    }
+    return ret;
 }
 
 
@@ -2075,6 +2095,7 @@ CBORDecoder_decode_from_bytes(CBORDecoderObject *self, PyObject *data)
     if (!_CBOR2_BytesIO && _CBOR2_init_BytesIO() == -1)
         return NULL;
 
+    self->decode_depth++;
     save_read = self->read;
     buf = PyObject_CallFunctionObjArgs(_CBOR2_BytesIO, data, NULL);
     if (buf) {
@@ -2086,6 +2107,11 @@ CBORDecoder_decode_from_bytes(CBORDecoderObject *self, PyObject *data)
         Py_DECREF(buf);
     }
     self->read = save_read;
+    self->decode_depth--;
+    assert(self->decode_depth >= 0);
+    if (self->decode_depth == 0) {
+        clear_shareable_state(self);
+    }
     return ret;
 }
 
diff --git a/source/decoder.h b/source/decoder.h
index 6bb6d52f..a2f1bcbe 100644
--- a/source/decoder.h
+++ b/source/decoder.h
@@ -13,6 +13,7 @@ typedef struct {
     PyObject *str_errors;
     bool immutable;
     Py_ssize_t shared_index;
+    Py_ssize_t decode_depth;
 } CBORDecoderObject;
 
 extern PyTypeObject CBORDecoderType;
diff --git a/source/encoder.c b/source/encoder.c
index 4dc3c6b3..e87670d6 100644
--- a/source/encoder.c
+++ b/source/encoder.c
@@ -113,6 +113,7 @@ CBOREncoder_new(PyTypeObject *type, PyObject *args, PyObject *kwargs)
         self->shared_handler = NULL;
         self->string_referencing = false;
         self->string_namespacing = false;
+        self->encode_depth = 0;
     }
     return (PyObject *) self;
 }
@@ -2027,17 +2028,35 @@ encode(CBOREncoderObject *self, PyObject *value)
 }
 
 
+// Reset shared state at the end of each top-level encode to prevent
+// shared references from leaking between independent encode operations.
+// Nested calls (from hooks or recursive encoding) must preserve the state.
+static inline void
+clear_shared_state(CBOREncoderObject *self)
+{
+    PyDict_Clear(self->shared);
+    PyDict_Clear(self->string_references);
+}
+
+
 // CBOREncoder.encode(self, value)
 PyObject *
 CBOREncoder_encode(CBOREncoderObject *self, PyObject *value)
 {
     PyObject *ret;
 
-    // TODO reset shared dict?
-    if (Py_EnterRecursiveCall(" in CBOREncoder.encode"))
+    self->encode_depth++;
+    if (Py_EnterRecursiveCall(" in CBOREncoder.encode")) {
+        self->encode_depth--;
         return NULL;
+    }
     ret = encode(self, value);
     Py_LeaveRecursiveCall();
+    self->encode_depth--;
+    assert(self->encode_depth >= 0);
+    if (self->encode_depth == 0) {
+        clear_shared_state(self);
+    }
     return ret;
 }
 
diff --git a/source/encoder.h b/source/encoder.h
index abc6560d..915f1f21 100644
--- a/source/encoder.h
+++ b/source/encoder.h
@@ -24,6 +24,7 @@ typedef struct {
     bool value_sharing;
     bool string_referencing;
     bool string_namespacing;
+    Py_ssize_t encode_depth;
 } CBOREncoderObject;
 
 extern PyTypeObject CBOREncoderType;