SASLprep and traceprep implementations

sasl/stringprep.py

@@ -0,0 +1,116 @@
+"""SASL stringprep_ profiles
+
+Defines functions which implement a few SASL-related stringprep
+profiles. Each function takes a (unicode) string and either returns
+the prepared string or raises an exception, usually a UnicodeError.
+
+.. _stringprep: http://www.ietf.org/rfc/rfc3454.txt
+"""
+
+# Written in 2012 by Wim Lewis <wiml@hhhh.org>.
+# This file is in the public domain. It may be used,
+# distributed, and modified without restriction.
+
+from __future__ import absolute_import
+from stringprep import *
+import unicodedata
+
+__all__ = ( 'traceprep', 'saslprep' )
+__docformat__ = 'reStructuredText en'
+
+def saslprep(s):
+    """Prepare a string according to the SASLprep_ stringprep profile.
+
+    >>> saslprep(u'Hi\u2003\uff2d\uff4f\uff4d!')
+    u'Hi Mom!'
+
+    >>> saslprep(u'Hi\\rMom!')
+    Traceback (most recent call last):
+    UnicodeError: Prohibited character u'\\r'
+
+    >>> saslprep(u'Num\u00ADber \u2168')
+    u'Number IX'
+
+    .. _SASLprep: http://www.ietf.org/rfc/rfc4013.txt
+    """
+
+    # Step 1 - Map
+    buf = u''
+    for ch in s:
+        if in_table_c12(ch):
+            buf += u' '
+        elif not in_table_b1(ch):
+            buf += ch
+
+    # Step 2 - Normalize
+    buf = unicodedata.normalize('NFKC', buf)
+
+    # Step 3 - Prohibited characters
+    for ch in buf:
+        if ( in_table_c21(ch) or
+             in_table_c22(ch) or
+             in_table_c3(ch)  or
+             in_table_c4(ch)  or
+             in_table_c5(ch)  or
+             in_table_c6(ch)  or
+             in_table_c7(ch)  or
+             in_table_c8(ch)  or
+             in_table_c9(ch) ):
+            raise UnicodeError("Prohibited character %r" % (ch,))
+
+    # Step 4 - bidi mark checking
+    _bidi_check(buf)
+
+    return buf
+
+def _bidi_check(buf):
+    "Perform the checks from RFC3454 section 6, and raise on failure."
+    # If there are any characters in category D1 (R and AL), then do extra checks.
+    if any(map(in_table_d1, buf)):
+        # If there are any R+AL characters, the first and last
+        # characters must be R+AL.
+        if not in_table_d1(buf[0]) or not in_table_d1(buf[-1]):
+            raise UnicodeError("bidi rejected by stringprep (6.3)")
+        # And there must not be any L (table d2).
+        if any(map(in_table_d2, buf)):
+            raise UnicodeError("bidi rejected by stringprep (6.2)")
+
+def traceprep(s):
+    """Prepare a Unicode string according to the trace_ stringprep profile.
+
+    .. _trace: http://www.ietf.org/rfc/rfc4505.txt
+    """
+
+    # Trace defines no mapping or normalization.
+
+    # Prohibited characters
+    for ch in s:
+        if ( in_table_c21(ch) or
+             in_table_c22(ch) or
+             in_table_c3(ch)  or
+             in_table_c4(ch)  or
+             in_table_c5(ch)  or
+             in_table_c6(ch)  or
+             # But not table C.7.
+             in_table_c8(ch)  or
+             in_table_c9(ch) ):
+            raise UnicodeError("Prohibited character %r" % (ch,))
+
+    # Step 4 - bidi mark checking
+    _bidi_check(s)
+
+    return s
+
+__test__ = {
+    'bidi': """
+    >>> _bidi_check(u'\u0627\u0031\u0628')
+
+    >>> _bidi_check(u'\u0627' + u'1')
+    Traceback (most recent call last):
+    UnicodeError: bidi rejected by stringprep (6.3)
+
+    >>> _bidi_check(u'\u05c0 foo \u05c0')
+    Traceback (most recent call last):
+    UnicodeError: bidi rejected by stringprep (6.2)
+    """
+}