1 files changed, 146 insertions, 0 deletions
diff --git a/lib/Crypto/Util/strxor.py b/lib/Crypto/Util/strxor.py
new file mode 100644
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+++ b/lib/Crypto/Util/strxor.py
@@ -0,0 +1,146 @@
+# ===================================================================
+#
+# Copyright (c) 2014, Legrandin <helderijs@gmail.com>
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions
+# are met:
+#
+# 1. Redistributions of source code must retain the above copyright
+#    notice, this list of conditions and the following disclaimer.
+# 2. Redistributions in binary form must reproduce the above copyright
+#    notice, this list of conditions and the following disclaimer in
+#    the documentation and/or other materials provided with the
+#    distribution.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+# FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+# COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+# INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+# BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+# LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+# CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+# ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+# POSSIBILITY OF SUCH DAMAGE.
+# ===================================================================
+
+from Crypto.Util._raw_api import (load_pycryptodome_raw_lib, c_size_t,
+                                  create_string_buffer, get_raw_buffer,
+                                  c_uint8_ptr, is_writeable_buffer)
+
+_raw_strxor = load_pycryptodome_raw_lib(
+                    "Crypto.Util._strxor",
+                    """
+                    void strxor(const uint8_t *in1,
+                                const uint8_t *in2,
+                                uint8_t *out, size_t len);
+                    void strxor_c(const uint8_t *in,
+                                  uint8_t c,
+                                  uint8_t *out,
+                                  size_t len);
+                    """)
+
+
+def strxor(term1, term2, output=None):
+    """From two byte strings of equal length,
+    create a third one which is the byte-by-byte XOR of the two.
+
+    Args:
+      term1 (bytes/bytearray/memoryview):
+        The first byte string to XOR.
+      term2 (bytes/bytearray/memoryview):
+        The second byte string to XOR.
+      output (bytearray/memoryview):
+        The location where the result will be written to.
+        It must have the same length as ``term1`` and ``term2``.
+        If ``None``, the result is returned.
+    :Return:
+        If ``output`` is ``None``, a new byte string with the result.
+        Otherwise ``None``.
+
+    .. note::
+        ``term1`` and ``term2`` must have the same length.
+    """
+
+    if len(term1) != len(term2):
+        raise ValueError("Only byte strings of equal length can be xored")
+
+    if output is None:
+        result = create_string_buffer(len(term1))
+    else:
+        # Note: output may overlap with either input
+        result = output
+
+        if not is_writeable_buffer(output):
+            raise TypeError("output must be a bytearray or a writeable memoryview")
+
+        if len(term1) != len(output):
+            raise ValueError("output must have the same length as the input"
+                             "  (%d bytes)" % len(term1))
+
+    _raw_strxor.strxor(c_uint8_ptr(term1),
+                       c_uint8_ptr(term2),
+                       c_uint8_ptr(result),
+                       c_size_t(len(term1)))
+
+    if output is None:
+        return get_raw_buffer(result)
+    else:
+        return None
+
+
+def strxor_c(term, c, output=None):
+    """From a byte string, create a second one of equal length
+    where each byte is XOR-red with the same value.
+
+    Args:
+      term(bytes/bytearray/memoryview):
+        The byte string to XOR.
+      c (int):
+        Every byte in the string will be XOR-ed with this value.
+        It must be between 0 and 255 (included).
+      output (None or bytearray/memoryview):
+        The location where the result will be written to.
+        It must have the same length as ``term``.
+        If ``None``, the result is returned.
+
+    Return:
+        If ``output`` is ``None``, a new ``bytes`` string with the result.
+        Otherwise ``None``.
+    """
+
+    if not 0 <= c < 256:
+        raise ValueError("c must be in range(256)")
+
+    if output is None:
+        result = create_string_buffer(len(term))
+    else:
+        # Note: output may overlap with either input
+        result = output
+
+        if not is_writeable_buffer(output):
+            raise TypeError("output must be a bytearray or a writeable memoryview")
+
+        if len(term) != len(output):
+            raise ValueError("output must have the same length as the input"
+                             "  (%d bytes)" % len(term))
+
+    _raw_strxor.strxor_c(c_uint8_ptr(term),
+                         c,
+                         c_uint8_ptr(result),
+                         c_size_t(len(term))
+                         )
+
+    if output is None:
+        return get_raw_buffer(result)
+    else:
+        return None
+
+
+def _strxor_direct(term1, term2, result):
+    """Very fast XOR - check conditions!"""
+    _raw_strxor.strxor(term1, term2, result, c_size_t(len(term1)))