[catapult] - Copy Telemetry's gsutilz over to third_party.

third_party/gsutil/third_party/rsa/rsa/bigfile.py

Index: third_party/gsutil/third_party/rsa/rsa/bigfile.py
diff --git a/third_party/gsutil/third_party/rsa/rsa/bigfile.py b/third_party/gsutil/third_party/rsa/rsa/bigfile.py
new file mode 100644
index 0000000000000000000000000000000000000000..516cf56b51e1f00cf68eda48ce00cbd1b0b2590c
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+++ b/third_party/gsutil/third_party/rsa/rsa/bigfile.py
@@ -0,0 +1,87 @@
+# -*- coding: utf-8 -*-
+#
+#  Copyright 2011 Sybren A. Stüvel <sybren@stuvel.eu>
+#
+#  Licensed under the Apache License, Version 2.0 (the "License");
+#  you may not use this file except in compliance with the License.
+#  You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+#  Unless required by applicable law or agreed to in writing, software
+#  distributed under the License is distributed on an "AS IS" BASIS,
+#  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+#  See the License for the specific language governing permissions and
+#  limitations under the License.
+
+'''Large file support
+
+    - break a file into smaller blocks, and encrypt them, and store the
+      encrypted blocks in another file.
+
+    - take such an encrypted files, decrypt its blocks, and reconstruct the
+      original file.
+
+The encrypted file format is as follows, where || denotes byte concatenation:
+
+    FILE := VERSION || BLOCK || BLOCK ...
+
+    BLOCK := LENGTH || DATA
+
+    LENGTH := varint-encoded length of the subsequent data. Varint comes from
+    Google Protobuf, and encodes an integer into a variable number of bytes.
+    Each byte uses the 7 lowest bits to encode the value. The highest bit set
+    to 1 indicates the next byte is also part of the varint. The last byte will
+    have this bit set to 0.
+
+This file format is called the VARBLOCK format, in line with the varint format
+used to denote the block sizes.
+
+'''
+
+from rsa import key, common, pkcs1, varblock
+from rsa._compat import byte
+
+def encrypt_bigfile(infile, outfile, pub_key):
+    '''Encrypts a file, writing it to 'outfile' in VARBLOCK format.
+    
+    :param infile: file-like object to read the cleartext from
+    :param outfile: file-like object to write the crypto in VARBLOCK format to
+    :param pub_key: :py:class:`rsa.PublicKey` to encrypt with
+
+    '''
+
+    if not isinstance(pub_key, key.PublicKey):
+        raise TypeError('Public key required, but got %r' % pub_key)
+
+    key_bytes = common.bit_size(pub_key.n) // 8
+    blocksize = key_bytes - 11 # keep space for PKCS#1 padding
+
+    # Write the version number to the VARBLOCK file
+    outfile.write(byte(varblock.VARBLOCK_VERSION))
+
+    # Encrypt and write each block
+    for block in varblock.yield_fixedblocks(infile, blocksize):
+        crypto = pkcs1.encrypt(block, pub_key)
+
+        varblock.write_varint(outfile, len(crypto))
+        outfile.write(crypto)
+
+def decrypt_bigfile(infile, outfile, priv_key):
+    '''Decrypts an encrypted VARBLOCK file, writing it to 'outfile'
+    
+    :param infile: file-like object to read the crypto in VARBLOCK format from
+    :param outfile: file-like object to write the cleartext to
+    :param priv_key: :py:class:`rsa.PrivateKey` to decrypt with
+
+    '''
+
+    if not isinstance(priv_key, key.PrivateKey):
+        raise TypeError('Private key required, but got %r' % priv_key)
+    
+    for block in varblock.yield_varblocks(infile):
+        cleartext = pkcs1.decrypt(block, priv_key)
+        outfile.write(cleartext)
+
+__all__ = ['encrypt_bigfile', 'decrypt_bigfile']
+