An implementation of the SASLprep stringprep profile.

Author: wiml

sasl/stringprep.py

@@ -0,0 +1,55 @@
+"""SASL stringprep profile
+
+<http://www.ietf.org/rfc/rfc4013.txt>
+<http://www.ietf.org/rfc/rfc3454.txt>
+
+Copyright (C) 2012, Wim Lewis <wiml@hhhh.org>.
+"""
+
+from __future__ import absolute_import
+from stringprep import *
+import unicodedata
+
+__all__ = ( 'prepare', )
+
+def prepare(s):
+    """Prepare a Unicode string according to the SASLprep stringprep profile.
+    Returns the prepared string, or raises a UnicodeError on failue."""
+
+    # 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("Invalid character %r" % (ch,))
+    
+    # Step 4 - bidi mark checking
+    # If there are any characters in categort D1 (randAL), 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)")
+        
+    return buf
+