[utils] Add pkcs1pad

Used in daisuki.net (#4738)

2 files changed, 24 insertions, 0 deletions

diff --git a/test/test_utils.py b/test/test_utils.py
index 3cdb21d40..aefd94518 100644
--- a/test/test_utils.py
+++ b/test/test_utils.py
@@ -52,6 +52,7 @@ from youtube_dl.utils import (
     parse_filesize,
     parse_count,
     parse_iso8601,
+    pkcs1pad,
     read_batch_urls,
     sanitize_filename,
     sanitize_path,
@@ -1104,6 +1105,14 @@ The first line
             ohdave_rsa_encrypt(b'aa111222', e, N),
             '726664bd9a23fd0c70f9f1b84aab5e3905ce1e45a584e9cbcf9bcc7510338fc1986d6c599ff990d923aa43c51c0d9013cd572e13bc58f4ae48f2ed8c0b0ba881')
 
+    def test_pkcs1pad(self):
+        data = [1, 2, 3]
+        padded_data = pkcs1pad(data, 32)
+        self.assertEqual(padded_data[:2], [0, 2])
+        self.assertEqual(padded_data[28:], [0, 1, 2, 3])
+
+        self.assertRaises(ValueError, pkcs1pad, data, 8)
+
     def test_encode_base_n(self):
         self.assertEqual(encode_base_n(0, 30), '0')
         self.assertEqual(encode_base_n(80, 30), '2k')
diff --git a/youtube_dl/utils.py b/youtube_dl/utils.py
index 17b83794a..8bd075eaf 100644
--- a/youtube_dl/utils.py
+++ b/youtube_dl/utils.py
@@ -3336,6 +3336,21 @@ def ohdave_rsa_encrypt(data, exponent, modulus):
     return '%x' % encrypted
 
 
+def pkcs1pad(data, length):
+    """
+    Padding input data with PKCS#1 scheme
+
+    @param {int[]} data        input data
+    @param {int}   length      target length
+    @returns {int[]}           padded data
+    """
+    if len(data) > length - 11:
+        raise ValueError('Input data too long for PKCS#1 padding')
+
+    pseudo_random = [random.randint(0, 254) for _ in range(length - len(data) - 3)]
+    return [0, 2] + pseudo_random + [0] + data
+
+
 def encode_base_n(num, n, table=None):
     FULL_TABLE = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ'
     if not table: