Fixes #29308: Merged fix from 3.5.

1 files changed, 73 insertions, 0 deletions

diff --git a/Lib/secrets.py b/Lib/secrets.py
new file mode 100644
index 0000000000..130434229e
--- /dev/null
+++ b/Lib/secrets.py
@@ -0,0 +1,73 @@
+"""Generate cryptographically strong pseudo-random numbers suitable for
+managing secrets such as account authentication, tokens, and similar.
+
+See PEP 506 for more information.
+https://www.python.org/dev/peps/pep-0506/
+
+"""
+
+__all__ = ['choice', 'randbelow', 'randbits', 'SystemRandom',
+           'token_bytes', 'token_hex', 'token_urlsafe',
+           'compare_digest',
+           ]
+
+
+import base64
+import binascii
+import os
+
+from hmac import compare_digest
+from random import SystemRandom
+
+_sysrand = SystemRandom()
+
+randbits = _sysrand.getrandbits
+choice = _sysrand.choice
+
+def randbelow(exclusive_upper_bound):
+    """Return a random int in the range [0, n)."""
+    if exclusive_upper_bound <= 0:
+        raise ValueError("Upper bound must be positive.")
+    return _sysrand._randbelow(exclusive_upper_bound)
+
+DEFAULT_ENTROPY = 32  # number of bytes to return by default
+
+def token_bytes(nbytes=None):
+    """Return a random byte string containing *nbytes* bytes.
+
+    If *nbytes* is ``None`` or not supplied, a reasonable
+    default is used.
+
+    >>> token_bytes(16)  #doctest:+SKIP
+    b'\\xebr\\x17D*t\\xae\\xd4\\xe3S\\xb6\\xe2\\xebP1\\x8b'
+
+    """
+    if nbytes is None:
+        nbytes = DEFAULT_ENTROPY
+    return os.urandom(nbytes)
+
+def token_hex(nbytes=None):
+    """Return a random text string, in hexadecimal.
+
+    The string has *nbytes* random bytes, each byte converted to two
+    hex digits.  If *nbytes* is ``None`` or not supplied, a reasonable
+    default is used.
+
+    >>> token_hex(16)  #doctest:+SKIP
+    'f9bf78b9a18ce6d46a0cd2b0b86df9da'
+
+    """
+    return binascii.hexlify(token_bytes(nbytes)).decode('ascii')
+
+def token_urlsafe(nbytes=None):
+    """Return a random URL-safe text string, in Base64 encoding.
+
+    The string has *nbytes* random bytes.  If *nbytes* is ``None``
+    or not supplied, a reasonable default is used.
+
+    >>> token_urlsafe(16)  #doctest:+SKIP
+    'Drmhze6EPcv0fN_81Bj-nA'
+
+    """
+    tok = token_bytes(nbytes)
+    return base64.urlsafe_b64encode(tok).rstrip(b'=').decode('ascii')