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env/lib/python3.11/site-packages/Crypto/IO/PEM.py

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+#
+#  Util/PEM.py : Privacy Enhanced Mail utilities
+#
+# ===================================================================
+#
+# 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__ = ['encode', 'decode']
+
+import re
+from binascii import a2b_base64, b2a_base64, hexlify, unhexlify
+
+from Crypto.Hash import MD5
+from Crypto.Util.Padding import pad, unpad
+from Crypto.Cipher import DES, DES3, AES
+from Crypto.Protocol.KDF import PBKDF1
+from Crypto.Random import get_random_bytes
+from Crypto.Util.py3compat import tobytes, tostr
+
+
+def encode(data, marker, passphrase=None, randfunc=None):
+    """Encode a piece of binary data into PEM format.
+
+    Args:
+      data (byte string):
+        The piece of binary data to encode.
+      marker (string):
+        The marker for the PEM block (e.g. "PUBLIC KEY").
+        Note that there is no official master list for all allowed markers.
+        Still, you can refer to the OpenSSL_ source code.
+      passphrase (byte string):
+        If given, the PEM block will be encrypted. The key is derived from
+        the passphrase.
+      randfunc (callable):
+        Random number generation function; it accepts an integer N and returns
+        a byte string of random data, N bytes long. If not given, a new one is
+        instantiated.
+
+    Returns:
+      The PEM block, as a string.
+
+    .. _OpenSSL: https://github.com/openssl/openssl/blob/master/include/openssl/pem.h
+    """
+
+    if randfunc is None:
+        randfunc = get_random_bytes
+
+    out = "-----BEGIN %s-----\n" % marker
+    if passphrase:
+        # We only support 3DES for encryption
+        salt = randfunc(8)
+        key = PBKDF1(passphrase, salt, 16, 1, MD5)
+        key += PBKDF1(key + passphrase, salt, 8, 1, MD5)
+        objenc = DES3.new(key, DES3.MODE_CBC, salt)
+        out += "Proc-Type: 4,ENCRYPTED\nDEK-Info: DES-EDE3-CBC,%s\n\n" %\
+            tostr(hexlify(salt).upper())
+        # Encrypt with PKCS#7 padding
+        data = objenc.encrypt(pad(data, objenc.block_size))
+    elif passphrase is not None:
+        raise ValueError("Empty password")
+
+    # Each BASE64 line can take up to 64 characters (=48 bytes of data)
+    # b2a_base64 adds a new line character!
+    chunks = [tostr(b2a_base64(data[i:i + 48]))
+              for i in range(0, len(data), 48)]
+    out += "".join(chunks)
+    out += "-----END %s-----" % marker
+    return out
+
+
+def _EVP_BytesToKey(data, salt, key_len):
+    d = [ b'' ]
+    m = (key_len + 15 ) // 16
+    for _ in range(m):
+        nd = MD5.new(d[-1] + data + salt).digest()
+        d.append(nd)
+    return b"".join(d)[:key_len]
+
+
+def decode(pem_data, passphrase=None):
+    """Decode a PEM block into binary.
+
+    Args:
+      pem_data (string):
+        The PEM block.
+      passphrase (byte string):
+        If given and the PEM block is encrypted,
+        the key will be derived from the passphrase.
+
+    Returns:
+      A tuple with the binary data, the marker string, and a boolean to
+      indicate if decryption was performed.
+
+    Raises:
+      ValueError: if decoding fails, if the PEM file is encrypted and no passphrase has
+                  been provided or if the passphrase is incorrect.
+    """
+
+    # Verify Pre-Encapsulation Boundary
+    r = re.compile(r"\s*-----BEGIN (.*)-----\s+")
+    m = r.match(pem_data)
+    if not m:
+        raise ValueError("Not a valid PEM pre boundary")
+    marker = m.group(1)
+
+    # Verify Post-Encapsulation Boundary
+    r = re.compile(r"-----END (.*)-----\s*$")
+    m = r.search(pem_data)
+    if not m or m.group(1) != marker:
+        raise ValueError("Not a valid PEM post boundary")
+
+    # Removes spaces and slit on lines
+    lines = pem_data.replace(" ", '').split()
+
+    # Decrypts, if necessary
+    if lines[1].startswith('Proc-Type:4,ENCRYPTED'):
+        if not passphrase:
+            raise ValueError("PEM is encrypted, but no passphrase available")
+        DEK = lines[2].split(':')
+        if len(DEK) != 2 or DEK[0] != 'DEK-Info':
+            raise ValueError("PEM encryption format not supported.")
+        algo, salt = DEK[1].split(',')
+        salt = unhexlify(tobytes(salt))
+
+        padding = True
+
+        if algo == "DES-CBC":
+            key = _EVP_BytesToKey(passphrase, salt, 8)
+            objdec = DES.new(key, DES.MODE_CBC, salt)
+        elif algo == "DES-EDE3-CBC":
+            key = _EVP_BytesToKey(passphrase, salt, 24)
+            objdec = DES3.new(key, DES3.MODE_CBC, salt)
+        elif algo == "AES-128-CBC":
+            key = _EVP_BytesToKey(passphrase, salt[:8], 16)
+            objdec = AES.new(key, AES.MODE_CBC, salt)
+        elif algo == "AES-192-CBC":
+            key = _EVP_BytesToKey(passphrase, salt[:8], 24)
+            objdec = AES.new(key, AES.MODE_CBC, salt)
+        elif algo == "AES-256-CBC":
+            key = _EVP_BytesToKey(passphrase, salt[:8], 32)
+            objdec = AES.new(key, AES.MODE_CBC, salt)
+        elif algo.lower() == "id-aes256-gcm":
+            key = _EVP_BytesToKey(passphrase, salt[:8], 32)
+            objdec = AES.new(key, AES.MODE_GCM, nonce=salt)
+            padding = False
+        else:
+            raise ValueError("Unsupport PEM encryption algorithm (%s)." % algo)
+        lines = lines[2:]
+    else:
+        objdec = None
+
+    # Decode body
+    data = a2b_base64(''.join(lines[1:-1]))
+    enc_flag = False
+    if objdec:
+        if padding:
+            data = unpad(objdec.decrypt(data), objdec.block_size)
+        else:
+            # There is no tag, so we don't use decrypt_and_verify
+            data = objdec.decrypt(data)
+        enc_flag = True
+
+    return (data, marker, enc_flag)