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-rw-r--r--Modules/operator.c180
1 files changed, 162 insertions, 18 deletions
diff --git a/Modules/operator.c b/Modules/operator.c
index 866ec3a761..5156b6b32d 100644
--- a/Modules/operator.c
+++ b/Modules/operator.c
@@ -159,6 +159,143 @@ is_not(PyObject *s, PyObject *a)
#undef spam2
#undef spam1o
#undef spam1o
+
+/* compare_digest **********************************************************/
+
+/*
+ * timing safe compare
+ *
+ * Returns 1 of the strings are equal.
+ * In case of len(a) != len(b) the function tries to keep the timing
+ * dependent on the length of b. CPU cache locally may still alter timing
+ * a bit.
+ */
+static int
+_tscmp(const unsigned char *a, const unsigned char *b,
+ Py_ssize_t len_a, Py_ssize_t len_b)
+{
+ /* The volatile type declarations make sure that the compiler has no
+ * chance to optimize and fold the code in any way that may change
+ * the timing.
+ */
+ volatile Py_ssize_t length;
+ volatile const unsigned char *left;
+ volatile const unsigned char *right;
+ Py_ssize_t i;
+ unsigned char result;
+
+ /* loop count depends on length of b */
+ length = len_b;
+ left = NULL;
+ right = b;
+
+ /* don't use else here to keep the amount of CPU instructions constant,
+ * volatile forces re-evaluation
+ * */
+ if (len_a == length) {
+ left = *((volatile const unsigned char**)&a);
+ result = 0;
+ }
+ if (len_a != length) {
+ left = b;
+ result = 1;
+ }
+
+ for (i=0; i < length; i++) {
+ result |= *left++ ^ *right++;
+ }
+
+ return (result == 0);
+}
+
+PyDoc_STRVAR(compare_digest__doc__,
+"compare_digest(a, b) -> bool\n"
+"\n"
+"Return 'a == b'. This function uses an approach designed to prevent\n"
+"timing analysis, making it appropriate for cryptography.\n"
+"a and b must both be of the same type: either str (ASCII only),\n"
+"or any type that supports the buffer protocol (e.g. bytes).\n"
+"\n"
+"Note: If a and b are of different lengths, or if an error occurs,\n"
+"a timing attack could theoretically reveal information about the\n"
+"types and lengths of a and b--but not their values.\n");
+
+static PyObject*
+compare_digest(PyObject *self, PyObject *args)
+{
+ PyObject *a, *b;
+ int rc;
+
+ if (!PyArg_ParseTuple(args, "OO:compare_digest", &a, &b)) {
+ return NULL;
+ }
+
+ /* ASCII unicode string */
+ if(PyUnicode_Check(a) && PyUnicode_Check(b)) {
+ if (PyUnicode_READY(a) == -1 || PyUnicode_READY(b) == -1) {
+ return NULL;
+ }
+ if (!PyUnicode_IS_ASCII(a) || !PyUnicode_IS_ASCII(b)) {
+ PyErr_SetString(PyExc_TypeError,
+ "comparing strings with non-ASCII characters is "
+ "not supported");
+ return NULL;
+ }
+
+ rc = _tscmp(PyUnicode_DATA(a),
+ PyUnicode_DATA(b),
+ PyUnicode_GET_LENGTH(a),
+ PyUnicode_GET_LENGTH(b));
+ }
+ /* fallback to buffer interface for bytes, bytesarray and other */
+ else {
+ Py_buffer view_a;
+ Py_buffer view_b;
+
+ if ((PyObject_CheckBuffer(a) == 0) & (PyObject_CheckBuffer(b) == 0)) {
+ PyErr_Format(PyExc_TypeError,
+ "unsupported operand types(s) or combination of types: "
+ "'%.100s' and '%.100s'",
+ Py_TYPE(a)->tp_name, Py_TYPE(b)->tp_name);
+ return NULL;
+ }
+
+ if (PyObject_GetBuffer(a, &view_a, PyBUF_SIMPLE) == -1) {
+ return NULL;
+ }
+ if (view_a.ndim > 1) {
+ PyErr_SetString(PyExc_BufferError,
+ "Buffer must be single dimension");
+ PyBuffer_Release(&view_a);
+ return NULL;
+ }
+
+ if (PyObject_GetBuffer(b, &view_b, PyBUF_SIMPLE) == -1) {
+ PyBuffer_Release(&view_a);
+ return NULL;
+ }
+ if (view_b.ndim > 1) {
+ PyErr_SetString(PyExc_BufferError,
+ "Buffer must be single dimension");
+ PyBuffer_Release(&view_a);
+ PyBuffer_Release(&view_b);
+ return NULL;
+ }
+
+ rc = _tscmp((const unsigned char*)view_a.buf,
+ (const unsigned char*)view_b.buf,
+ view_a.len,
+ view_b.len);
+
+ PyBuffer_Release(&view_a);
+ PyBuffer_Release(&view_b);
+ }
+
+ return PyBool_FromLong(rc);
+}
+
+/* operator methods **********************************************************/
+
#define spam1(OP,DOC) {#OP, OP, METH_VARARGS, PyDoc_STR(DOC)},
#define spam2(OP,ALTOP,DOC) {#OP, op_##OP, METH_VARARGS, PyDoc_STR(DOC)}, \
{#ALTOP, op_##OP, METH_VARARGS, PyDoc_STR(DOC)},
@@ -227,6 +364,8 @@ spam2(ne,__ne__, "ne(a, b) -- Same as a!=b.")
spam2(gt,__gt__, "gt(a, b) -- Same as a>b.")
spam2(ge,__ge__, "ge(a, b) -- Same as a>=b.")
+ {"_compare_digest", (PyCFunction)compare_digest, METH_VARARGS,
+ compare_digest__doc__},
{NULL, NULL} /* sentinel */
};
@@ -321,8 +460,8 @@ PyDoc_STRVAR(itemgetter_doc,
"itemgetter(item, ...) --> itemgetter object\n\
\n\
Return a callable object that fetches the given item(s) from its operand.\n\
-After, f=itemgetter(2), the call f(r) returns r[2].\n\
-After, g=itemgetter(2,5,3), the call g(r) returns (r[2], r[5], r[3])");
+After f = itemgetter(2), the call f(r) returns r[2].\n\
+After g = itemgetter(2, 5, 3), the call g(r) returns (r[2], r[5], r[3])");
static PyTypeObject itemgetter_type = {
PyVarObject_HEAD_INIT(NULL, 0)
@@ -402,7 +541,8 @@ attrgetter_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
for (idx = 0; idx < nattrs; ++idx) {
PyObject *item = PyTuple_GET_ITEM(args, idx);
Py_ssize_t item_len;
- Py_UNICODE *item_buffer;
+ void *data;
+ unsigned int kind;
int dot_count;
if (!PyUnicode_Check(item)) {
@@ -411,13 +551,18 @@ attrgetter_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
Py_DECREF(attr);
return NULL;
}
- item_len = PyUnicode_GET_SIZE(item);
- item_buffer = PyUnicode_AS_UNICODE(item);
+ if (PyUnicode_READY(item)) {
+ Py_DECREF(attr);
+ return NULL;
+ }
+ item_len = PyUnicode_GET_LENGTH(item);
+ kind = PyUnicode_KIND(item);
+ data = PyUnicode_DATA(item);
/* check whethere the string is dotted */
dot_count = 0;
for (char_idx = 0; char_idx < item_len; ++char_idx) {
- if (item_buffer[char_idx] == (Py_UNICODE)'.')
+ if (PyUnicode_READ(kind, data, char_idx) == '.')
++dot_count;
}
@@ -438,12 +583,12 @@ attrgetter_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
}
for (; dot_count > 0; --dot_count) {
- while (item_buffer[unibuff_till] != (Py_UNICODE)'.') {
+ while (PyUnicode_READ(kind, data, unibuff_till) != '.') {
++unibuff_till;
}
- attr_chain_item = PyUnicode_FromUnicode(
- item_buffer + unibuff_from,
- unibuff_till - unibuff_from);
+ attr_chain_item = PyUnicode_Substring(item,
+ unibuff_from,
+ unibuff_till);
if (attr_chain_item == NULL) {
Py_DECREF(attr_chain);
Py_DECREF(attr);
@@ -456,9 +601,8 @@ attrgetter_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
}
/* now add the last dotless name */
- attr_chain_item = PyUnicode_FromUnicode(
- item_buffer + unibuff_from,
- item_len - unibuff_from);
+ attr_chain_item = PyUnicode_Substring(item,
+ unibuff_from, item_len);
if (attr_chain_item == NULL) {
Py_DECREF(attr_chain);
Py_DECREF(attr);
@@ -568,9 +712,9 @@ PyDoc_STRVAR(attrgetter_doc,
"attrgetter(attr, ...) --> attrgetter object\n\
\n\
Return a callable object that fetches the given attribute(s) from its operand.\n\
-After, f=attrgetter('name'), the call f(r) returns r.name.\n\
-After, g=attrgetter('name', 'date'), the call g(r) returns (r.name, r.date).\n\
-After, h=attrgetter('name.first', 'name.last'), the call h(r) returns\n\
+After f = attrgetter('name'), the call f(r) returns r.name.\n\
+After g = attrgetter('name', 'date'), the call g(r) returns (r.name, r.date).\n\
+After h = attrgetter('name.first', 'name.last'), the call h(r) returns\n\
(r.name.first, r.name.last).");
static PyTypeObject attrgetter_type = {
@@ -700,8 +844,8 @@ PyDoc_STRVAR(methodcaller_doc,
"methodcaller(name, ...) --> methodcaller object\n\
\n\
Return a callable object that calls the given method on its operand.\n\
-After, f = methodcaller('name'), the call f(r) returns r.name().\n\
-After, g = methodcaller('name', 'date', foo=1), the call g(r) returns\n\
+After f = methodcaller('name'), the call f(r) returns r.name().\n\
+After g = methodcaller('name', 'date', foo=1), the call g(r) returns\n\
r.name('date', foo=1).");
static PyTypeObject methodcaller_type = {
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