1 files changed, 109 insertions, 0 deletions
diff --git a/heat/common/password_gen.py b/heat/common/password_gen.py
new file mode 100644
index 000000000..93b03c6b9
--- /dev/null
+++ b/heat/common/password_gen.py
@@ -0,0 +1,109 @@
+#
+#    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.
+
+import collections
+import random as random_module
+import string
+
+import six
+
+
+# NOTE(pas-ha) Heat officially supports only POSIX::Linux platform
+# where os.urandom() and random.SystemRandom() are available
+random = random_module.SystemRandom()
+
+
+CHARACTER_CLASSES = (
+    LETTERS_DIGITS, LETTERS, LOWERCASE, UPPERCASE,
+    DIGITS, HEXDIGITS, OCTDIGITS,
+) = (
+    'lettersdigits', 'letters', 'lowercase', 'uppercase',
+    'digits', 'hexdigits', 'octdigits',
+)
+
+_char_class_members = {
+    LETTERS_DIGITS: string.ascii_letters + string.digits,
+    LETTERS: string.ascii_letters,
+    LOWERCASE: string.ascii_lowercase,
+    UPPERCASE: string.ascii_uppercase,
+    DIGITS: string.digits,
+    HEXDIGITS: string.digits + 'ABCDEF',
+    OCTDIGITS: string.octdigits,
+}
+
+
+CharClass = collections.namedtuple('CharClass',
+                                   ('allowed_chars', 'min_count'))
+
+
+def named_char_class(char_class, min_count=0):
+    """Return a predefined character class.
+
+    The result of this function can be passed to :func:`generate_password` as
+    one of the character classes to use in generating a password.
+
+    :param char_class: Any of the character classes named in
+                       :const:`CHARACTER_CLASSES`
+    :param min_count: The minimum number of members of this class to appear in
+                      a generated password
+    """
+    assert char_class in CHARACTER_CLASSES
+    return CharClass(frozenset(_char_class_members[char_class]), min_count)
+
+
+def special_char_class(allowed_chars, min_count=0):
+    """Return a character class containing custom characters.
+
+    The result of this function can be passed to :func:`generate_password` as
+    one of the character classes to use in generating a password.
+
+    :param allowed_chars: Iterable of the characters in the character class
+    :param min_count: The minimum number of members of this class to appear in
+                      a generated password
+    """
+    return CharClass(frozenset(allowed_chars), min_count)
+
+
+def generate_password(length, char_classes):
+    """Generate a random password.
+
+    The password will be of the specified length, and comprised of characters
+    from the specified character classes, which can be generated using the
+    :func:`named_char_class` and :func:`special_char_class` functions. Where
+    a minimum count is specified in the character class, at least that number
+    of characters in the resulting password are guaranteed to be from that
+    character class.
+
+    :param length: The length of the password to generate, in characters
+    :param char_classes: Iterable over classes of characters from which to
+                         generate a password
+    """
+    char_buffer = six.StringIO()
+    all_allowed_chars = set()
+
+    # Add the minimum number of chars from each char class
+    for char_class in char_classes:
+        all_allowed_chars |= char_class.allowed_chars
+        allowed_chars = tuple(char_class.allowed_chars)
+        for i in six.moves.xrange(char_class.min_count):
+            char_buffer.write(random.choice(allowed_chars))
+
+    # Fill up rest with random chars from provided classes
+    combined_chars = tuple(all_allowed_chars)
+    for i in six.moves.xrange(max(0, length - char_buffer.tell())):
+        char_buffer.write(random.choice(combined_chars))
+
+    # Shuffle string
+    selected_chars = char_buffer.getvalue()
+    char_buffer.close()
+    return ''.join(random.sample(selected_chars, length))