From f8e15c1f693127f11327ee0f80334019b0990c5e Mon Sep 17 00:00:00 2001
From: Claudiu Popa <pcmanticore@gmail.com>
Date: Fri, 22 Nov 2019 10:53:03 +0100
Subject: [PATCH] bpo-38876: Raise pickle.UnpicklingError when loading an item
 from memo for invalid input

The previous code was raising a `KeyError` for both the Python and C implementation.
This was caused by the specified index of an invalid input which did not exist
in the memo structure, where the pickle stores what objects it has seen.
The malformed input would have caused either a `BINGET` or `LONG_BINGET` load
from the memo, leading to a `KeyError` as the determined index was bogus.
---
 Lib/pickle.py                                  | 18 +++++++++++++++---
 Lib/test/pickletester.py                       |  4 +++-
 .../2019-11-22-10-58-58.bpo-38876.qqy1Vp.rst   |  9 +++++++++
 Modules/_pickle.c                              | 12 ++++++++----
 4 files changed, 35 insertions(+), 8 deletions(-)
 create mode 100644 Misc/NEWS.d/next/Library/2019-11-22-10-58-58.bpo-38876.qqy1Vp.rst

diff --git a/Lib/pickle.py b/Lib/pickle.py
index 71aa57d500ecce..01d41422aa4a68 100644
--- a/Lib/pickle.py
+++ b/Lib/pickle.py
@@ -1604,17 +1604,29 @@ def load_dup(self):
 
     def load_get(self):
         i = int(self.readline()[:-1])
-        self.append(self.memo[i])
+        try:
+            self.append(self.memo[i])
+        except KeyError:
+            msg = f'Memo value not found at index {i}'
+            raise UnpicklingError(msg) from None
     dispatch[GET[0]] = load_get
 
     def load_binget(self):
         i = self.read(1)[0]
-        self.append(self.memo[i])
+        try:
+            self.append(self.memo[i])
+        except KeyError as exc:
+            msg = f'Memo value not found at index {i}'
+            raise UnpicklingError(msg) from None
     dispatch[BINGET[0]] = load_binget
 
     def load_long_binget(self):
         i, = unpack('<I', self.read(4))
-        self.append(self.memo[i])
+        try:
+            self.append(self.memo[i])
+        except KeyError as exc:
+            msg = f'Memo value not found at index {i}'
+            raise UnpicklingError(msg) from None
     dispatch[LONG_BINGET[0]] = load_long_binget
 
     def load_put(self):
diff --git a/Lib/test/pickletester.py b/Lib/test/pickletester.py
index c9f374678ae35a..953fd5c5a278ba 100644
--- a/Lib/test/pickletester.py
+++ b/Lib/test/pickletester.py
@@ -1019,7 +1019,9 @@ def test_short_binunicode(self):
         self.assertEqual(self.loads(dumped), '\u20ac\x00')
 
     def test_misc_get(self):
-        self.check_unpickling_error(KeyError, b'g0\np0')
+        self.check_unpickling_error(pickle.UnpicklingError, b'g0\np0')
+        self.check_unpickling_error(pickle.UnpicklingError, b'jens:')
+        self.check_unpickling_error(pickle.UnpicklingError, b'hens:')
         self.assert_is_copy([(100,), (100,)],
                             self.loads(b'((Kdtp0\nh\x00l.))'))
 
diff --git a/Misc/NEWS.d/next/Library/2019-11-22-10-58-58.bpo-38876.qqy1Vp.rst b/Misc/NEWS.d/next/Library/2019-11-22-10-58-58.bpo-38876.qqy1Vp.rst
new file mode 100644
index 00000000000000..43b25acc39d2ee
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2019-11-22-10-58-58.bpo-38876.qqy1Vp.rst
@@ -0,0 +1,9 @@
+Raise pickle.UnpicklingError when loading an item from memo for invalid
+input
+
+The previous code was raising a `KeyError` for both the Python and C
+implementation. This was caused by the specified index of an invalid input
+which did not exist in the memo structure, where the pickle stores what
+objects it has seen. The malformed input would have caused either a `BINGET`
+or `LONG_BINGET` load from the memo, leading to a `KeyError` as the
+determined index was bogus. Patch by Claudiu Popa
diff --git a/Modules/_pickle.c b/Modules/_pickle.c
index 7370be5938831a..baa0a274196938 100644
--- a/Modules/_pickle.c
+++ b/Modules/_pickle.c
@@ -6174,8 +6174,10 @@ load_get(UnpicklerObject *self)
 
     value = _Unpickler_MemoGet(self, idx);
     if (value == NULL) {
-        if (!PyErr_Occurred())
-            PyErr_SetObject(PyExc_KeyError, key);
+        if (!PyErr_Occurred()) {
+           PickleState *st = _Pickle_GetGlobalState();
+           PyErr_Format(st->UnpicklingError, "Memo value not found at index %ld", idx);
+        }
         Py_DECREF(key);
         return -1;
     }
@@ -6201,7 +6203,8 @@ load_binget(UnpicklerObject *self)
     if (value == NULL) {
         PyObject *key = PyLong_FromSsize_t(idx);
         if (key != NULL) {
-            PyErr_SetObject(PyExc_KeyError, key);
+            PickleState *st = _Pickle_GetGlobalState();
+            PyErr_Format(st->UnpicklingError, "Memo value not found at index %ld", idx);
             Py_DECREF(key);
         }
         return -1;
@@ -6227,7 +6230,8 @@ load_long_binget(UnpicklerObject *self)
     if (value == NULL) {
         PyObject *key = PyLong_FromSsize_t(idx);
         if (key != NULL) {
-            PyErr_SetObject(PyExc_KeyError, key);
+            PickleState *st = _Pickle_GetGlobalState();
+            PyErr_Format(st->UnpicklingError, "Memo value not found at index %ld", idx);
             Py_DECREF(key);
         }
         return -1;