From 1dac2263372df2b85db5d029a45721fa158a5c9d Mon Sep 17 00:00:00 2001
From: xiubuzhe <xiubuzhe@sina.com>
Date: Sun, 8 Oct 2023 20:59:00 +0800
Subject: first add files

---
 lib/Crypto/Util/Padding.py | 108 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 108 insertions(+)
 create mode 100644 lib/Crypto/Util/Padding.py

(limited to 'lib/Crypto/Util/Padding.py')

diff --git a/lib/Crypto/Util/Padding.py b/lib/Crypto/Util/Padding.py
new file mode 100644
index 0000000..da69e55
--- /dev/null
+++ b/lib/Crypto/Util/Padding.py
@@ -0,0 +1,108 @@
+#
+# Util/Padding.py :  Functions to manage padding
+#
+# ===================================================================
+#
+# 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.
+# ===================================================================
+
+__all__ = [ 'pad', 'unpad' ]
+
+from Crypto.Util.py3compat import *
+
+
+def pad(data_to_pad, block_size, style='pkcs7'):
+    """Apply standard padding.
+
+    Args:
+      data_to_pad (byte string):
+        The data that needs to be padded.
+      block_size (integer):
+        The block boundary to use for padding. The output length is guaranteed
+        to be a multiple of :data:`block_size`.
+      style (string):
+        Padding algorithm. It can be *'pkcs7'* (default), *'iso7816'* or *'x923'*.
+
+    Return:
+      byte string : the original data with the appropriate padding added at the end.
+    """
+
+    padding_len = block_size-len(data_to_pad)%block_size
+    if style == 'pkcs7':
+        padding = bchr(padding_len)*padding_len
+    elif style == 'x923':
+        padding = bchr(0)*(padding_len-1) + bchr(padding_len)
+    elif style == 'iso7816':
+        padding = bchr(128) + bchr(0)*(padding_len-1)
+    else:
+        raise ValueError("Unknown padding style")
+    return data_to_pad + padding
+
+
+def unpad(padded_data, block_size, style='pkcs7'):
+    """Remove standard padding.
+
+    Args:
+      padded_data (byte string):
+        A piece of data with padding that needs to be stripped.
+      block_size (integer):
+        The block boundary to use for padding. The input length
+        must be a multiple of :data:`block_size`.
+      style (string):
+        Padding algorithm. It can be *'pkcs7'* (default), *'iso7816'* or *'x923'*.
+    Return:
+        byte string : data without padding.
+    Raises:
+      ValueError: if the padding is incorrect.
+    """
+
+    pdata_len = len(padded_data)
+    if pdata_len == 0:
+        raise ValueError("Zero-length input cannot be unpadded")
+    if pdata_len % block_size:
+        raise ValueError("Input data is not padded")
+    if style in ('pkcs7', 'x923'):
+        padding_len = bord(padded_data[-1])
+        if padding_len<1 or padding_len>min(block_size, pdata_len):
+            raise ValueError("Padding is incorrect.")
+        if style == 'pkcs7':
+            if padded_data[-padding_len:]!=bchr(padding_len)*padding_len:
+                raise ValueError("PKCS#7 padding is incorrect.")
+        else:
+            if padded_data[-padding_len:-1]!=bchr(0)*(padding_len-1):
+                raise ValueError("ANSI X.923 padding is incorrect.")
+    elif style == 'iso7816':
+        padding_len = pdata_len - padded_data.rfind(bchr(128))
+        if padding_len<1 or padding_len>min(block_size, pdata_len):
+            raise ValueError("Padding is incorrect.")
+        if padding_len>1 and padded_data[1-padding_len:]!=bchr(0)*(padding_len-1):
+            raise ValueError("ISO 7816-4 padding is incorrect.")
+    else:
+        raise ValueError("Unknown padding style")
+    return padded_data[:-padding_len]
+
-- 
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