gh-113796: Add more validation checks in the csv.Dialect constructor (GH-113797)

ValueError is now raised if the same character is used in different roles.

3 files changed, 96 insertions, 13 deletions

diff --git a/Lib/test/test_csv.py b/Lib/test/test_csv.py
index 36da86e..69fef59 100644
--- a/Lib/test/test_csv.py
+++ b/Lib/test/test_csv.py
@@ -28,14 +28,20 @@ class Test_Csv(unittest.TestCase):
     in TestDialectRegistry.
     """
     def _test_arg_valid(self, ctor, arg):
+        ctor(arg)
         self.assertRaises(TypeError, ctor)
         self.assertRaises(TypeError, ctor, None)
-        self.assertRaises(TypeError, ctor, arg, bad_attr = 0)
-        self.assertRaises(TypeError, ctor, arg, delimiter = 0)
-        self.assertRaises(TypeError, ctor, arg, delimiter = 'XX')
+        self.assertRaises(TypeError, ctor, arg, bad_attr=0)
+        self.assertRaises(TypeError, ctor, arg, delimiter='')
+        self.assertRaises(TypeError, ctor, arg, escapechar='')
+        self.assertRaises(TypeError, ctor, arg, quotechar='')
+        self.assertRaises(TypeError, ctor, arg, delimiter='^^')
+        self.assertRaises(TypeError, ctor, arg, escapechar='^^')
+        self.assertRaises(TypeError, ctor, arg, quotechar='^^')
         self.assertRaises(csv.Error, ctor, arg, 'foo')
         self.assertRaises(TypeError, ctor, arg, delimiter=None)
         self.assertRaises(TypeError, ctor, arg, delimiter=1)
+        self.assertRaises(TypeError, ctor, arg, escapechar=1)
         self.assertRaises(TypeError, ctor, arg, quotechar=1)
         self.assertRaises(TypeError, ctor, arg, lineterminator=None)
         self.assertRaises(TypeError, ctor, arg, lineterminator=1)
@@ -46,6 +52,40 @@ class Test_Csv(unittest.TestCase):
                           quoting=csv.QUOTE_ALL, quotechar=None)
         self.assertRaises(TypeError, ctor, arg,
                           quoting=csv.QUOTE_NONE, quotechar='')
+        self.assertRaises(ValueError, ctor, arg, delimiter='\n')
+        self.assertRaises(ValueError, ctor, arg, escapechar='\n')
+        self.assertRaises(ValueError, ctor, arg, quotechar='\n')
+        self.assertRaises(ValueError, ctor, arg, delimiter='\r')
+        self.assertRaises(ValueError, ctor, arg, escapechar='\r')
+        self.assertRaises(ValueError, ctor, arg, quotechar='\r')
+        ctor(arg, delimiter=' ')
+        ctor(arg, escapechar=' ')
+        ctor(arg, quotechar=' ')
+        ctor(arg, delimiter='\t', skipinitialspace=True)
+        ctor(arg, escapechar='\t', skipinitialspace=True)
+        ctor(arg, quotechar='\t', skipinitialspace=True)
+        self.assertRaises(ValueError, ctor, arg,
+                          delimiter=' ', skipinitialspace=True)
+        self.assertRaises(ValueError, ctor, arg,
+                          escapechar=' ', skipinitialspace=True)
+        self.assertRaises(ValueError, ctor, arg,
+                          quotechar=' ', skipinitialspace=True)
+        ctor(arg, delimiter='^')
+        ctor(arg, escapechar='^')
+        ctor(arg, quotechar='^')
+        self.assertRaises(ValueError, ctor, arg, delimiter='^', escapechar='^')
+        self.assertRaises(ValueError, ctor, arg, delimiter='^', quotechar='^')
+        self.assertRaises(ValueError, ctor, arg, escapechar='^', quotechar='^')
+        ctor(arg, delimiter='\x85')
+        ctor(arg, escapechar='\x85')
+        ctor(arg, quotechar='\x85')
+        ctor(arg, lineterminator='\x85')
+        self.assertRaises(ValueError, ctor, arg,
+                          delimiter='\x85', lineterminator='\x85')
+        self.assertRaises(ValueError, ctor, arg,
+                          escapechar='\x85', lineterminator='\x85')
+        self.assertRaises(ValueError, ctor, arg,
+                          quotechar='\x85', lineterminator='\x85')
 
     def test_reader_arg_valid(self):
         self._test_arg_valid(csv.reader, [])
@@ -535,14 +575,6 @@ class TestDialectRegistry(unittest.TestCase):
         finally:
             csv.unregister_dialect('testC')
 
-    def test_bad_dialect(self):
-        # Unknown parameter
-        self.assertRaises(TypeError, csv.reader, [], bad_attr = 0)
-        # Bad values
-        self.assertRaises(TypeError, csv.reader, [], delimiter = None)
-        self.assertRaises(TypeError, csv.reader, [], quoting = -1)
-        self.assertRaises(TypeError, csv.reader, [], quoting = 100)
-
     def test_copy(self):
         for name in csv.list_dialects():
             dialect = csv.get_dialect(name)
@@ -1088,10 +1120,15 @@ class TestDialectValidity(unittest.TestCase):
                          '"lineterminator" must be a string')
 
     def test_invalid_chars(self):
-        def create_invalid(field_name, value):
+        def create_invalid(field_name, value, **kwargs):
             class mydialect(csv.Dialect):
-                pass
+                delimiter = ','
+                quoting = csv.QUOTE_ALL
+                quotechar = '"'
+                lineterminator = '\r\n'
             setattr(mydialect, field_name, value)
+            for field_name, value in kwargs.items():
+                setattr(mydialect, field_name, value)
             d = mydialect()
 
         for field_name in ("delimiter", "escapechar", "quotechar"):
@@ -1100,6 +1137,10 @@ class TestDialectValidity(unittest.TestCase):
                 self.assertRaises(csv.Error, create_invalid, field_name, "abc")
                 self.assertRaises(csv.Error, create_invalid, field_name, b'x')
                 self.assertRaises(csv.Error, create_invalid, field_name, 5)
+                self.assertRaises(ValueError, create_invalid, field_name, "\n")
+                self.assertRaises(ValueError, create_invalid, field_name, "\r")
+                self.assertRaises(ValueError, create_invalid, field_name, " ",
+                                  skipinitialspace=True)
 
 
 class TestSniffer(unittest.TestCase):
diff --git a/Misc/NEWS.d/next/Library/2024-01-07-21-04-24.gh-issue-113796.6iNsCR.rst b/Misc/NEWS.d/next/Library/2024-01-07-21-04-24.gh-issue-113796.6iNsCR.rst
new file mode 100644
index 0000000..e9d4aba
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2024-01-07-21-04-24.gh-issue-113796.6iNsCR.rst
@@ -0,0 +1,3 @@
+Add more validation checks in the :class:`csv.Dialect` constructor.
+:exc:`ValueError` is now raised if the same character is used in different
+roles.
diff --git a/Modules/_csv.c b/Modules/_csv.c
index 8d94156..929c215 100644
--- a/Modules/_csv.c
+++ b/Modules/_csv.c
@@ -331,6 +331,33 @@ dialect_check_quoting(int quoting)
     return -1;
 }
 
+static int
+dialect_check_char(const char *name, Py_UCS4 c, DialectObj *dialect)
+{
+    if (c == '\r' || c == '\n' || (dialect->skipinitialspace && c == ' ')) {
+        PyErr_Format(PyExc_ValueError, "bad %s value", name);
+        return -1;
+    }
+    if (PyUnicode_FindChar(
+        dialect->lineterminator, c, 0,
+        PyUnicode_GET_LENGTH(dialect->lineterminator), 1) >= 0)
+    {
+        PyErr_Format(PyExc_ValueError, "bad %s or lineterminator value", name);
+        return -1;
+    }
+    return 0;
+}
+
+ static int
+dialect_check_chars(const char *name1, const char *name2, Py_UCS4 c1, Py_UCS4 c2)
+{
+    if (c1 == c2 && c1 != NOT_SET) {
+        PyErr_Format(PyExc_ValueError, "bad %s or %s value", name1, name2);
+        return -1;
+    }
+    return 0;
+}
+
 #define D_OFF(x) offsetof(DialectObj, x)
 
 static struct PyMemberDef Dialect_memberlist[] = {
@@ -508,6 +535,18 @@ dialect_new(PyTypeObject *type, PyObject *args, PyObject *kwargs)
         PyErr_SetString(PyExc_TypeError, "lineterminator must be set");
         goto err;
     }
+    if (dialect_check_char("delimiter", self->delimiter, self) ||
+        dialect_check_char("escapechar", self->escapechar, self) ||
+        dialect_check_char("quotechar", self->quotechar, self) ||
+        dialect_check_chars("delimiter", "escapechar",
+                            self->delimiter, self->escapechar) ||
+        dialect_check_chars("delimiter", "quotechar",
+                            self->delimiter, self->quotechar) ||
+        dialect_check_chars("escapechar", "quotechar",
+                            self->escapechar, self->quotechar))
+    {
+        goto err;
+    }
 
     ret = Py_NewRef(self);
 err: