Implement IDNA (Internationalized Domain Names in Applications).

1 files changed, 187 insertions, 0 deletions

diff --git a/Lib/encodings/idna.py b/Lib/encodings/idna.py
new file mode 100644
index 0000000..7e4d04e
--- /dev/null
+++ b/Lib/encodings/idna.py
@@ -0,0 +1,187 @@
+# This module implements the RFCs 3490 (IDNA) and 3491 (Nameprep)
+
+import stringprep, unicodedata, re, codecs
+
+# IDNA section 3.1
+dots = re.compile(u"[\u002E\u3002\uFF0E\uFF61]")
+
+# IDNA section 5
+ace_prefix = "xn--"
+uace_prefix = unicode(ace_prefix, "ascii")
+
+# This assumes query strings, so AllowUnassigned is true
+def nameprep(label):
+    # Map
+    newlabel = []
+    for c in label:
+        if stringprep.in_table_b1(c):
+            # Map to nothing
+            continue
+        newlabel.append(stringprep.map_table_b2(c))
+    label = u"".join(newlabel)
+    
+    # Normalize
+    label = unicodedata.normalize("NFKC", label)
+    
+    # Prohibit
+    for c in label:
+        if stringprep.in_table_c12(c) or \
+           stringprep.in_table_c22(c) or \
+           stringprep.in_table_c3(c) or \
+           stringprep.in_table_c4(c) or \
+           stringprep.in_table_c5(c) or \
+           stringprep.in_table_c6(c) or \
+           stringprep.in_table_c7(c) or \
+           stringprep.in_table_c8(c) or \
+           stringprep.in_table_c9(c):
+            raise UnicodeError, "Invalid character %s" % repr(c)
+
+    # Check bidi
+    RandAL = map(stringprep.in_table_d1, label)
+    for c in RandAL:
+        if c:
+            # There is a RandAL char in the string. Must perform further
+            # tests:
+            # 1) The characters in section 5.8 MUST be prohibited.
+            # This is table C.8, which was already checked
+            # 2) If a string contains any RandALCat character, the string
+            # MUST NOT contain any LCat character.
+            if filter(stringprep.in_table_d2, label):
+                raise UnicodeError, "Violation of BIDI requirement 2"
+
+            # 3) If a string contains any RandALCat character, a
+            # RandALCat character MUST be the first character of the
+            # string, and a RandALCat character MUST be the last
+            # character of the string.
+            if not RandAL[0] or not RandAL[-1]:
+                raise UnicodeError, "Violation of BIDI requirement 3"
+
+    return label
+
+def ToASCII(label):
+    try:
+        # Step 1: try ASCII
+        label = label.encode("ascii")
+    except UnicodeError:
+        pass
+    else:
+        # Skip to step 3: UseSTD3ASCIIRules is false, so
+        # Skip to step 8.
+        if 0 < len(label) < 64:
+            return label
+        raise UnicodeError, "label too long"
+
+    # Step 2: nameprep
+    label = nameprep(label)
+
+    # Step 3: UseSTD3ASCIIRules is false
+    # Step 4: try ASCII
+    try:
+        label = label.encode("ascii")
+    except UnicodeError:
+        pass
+    else:
+        # Skip to step 8.
+        if 0 < len(label) < 64:
+            return label
+        raise UnicodeError, "label too long"
+
+    # Step 5: Check ACE prefix
+    if label.startswith(uace_prefix):
+        raise UnicodeError, "Label starts with ACE prefix"
+
+    # Step 6: Encode with PUNYCODE
+    label = label.encode("punycode")
+
+    # Step 7: Prepend ACE prefix
+    label = ace_prefix + label
+
+    # Step 8: Check size
+    if 0 < len(label) < 64:
+        return label
+    raise UnicodeError, "label too long"
+
+def ToUnicode(label):
+    # Step 1: Check for ASCII
+    if isinstance(label, str):
+        pure_ascii = True
+    else:
+        try:
+            label = label.encode("ascii")
+            pure_ascii = True
+        except UnicodeError:
+            pure_ascii = False
+    if not pure_ascii:
+        # Step 2: Perform nameprep
+        label = nameprep(label)
+        # It doesn't say this, but apparently, it should be ASCII now
+        try:
+            label = label.encode("ascii")
+        except UnicodeError:
+            raise UnicodeError, "Invalid character in IDN label"
+    # Step 3: Check for ACE prefix
+    if not label.startswith(ace_prefix):
+        return unicode(label, "ascii")
+
+    # Step 4: Remove ACE prefix
+    label1 = label[len(ace_prefix):]
+
+    # Step 5: Decode using PUNYCODE
+    result = label1.decode("punycode")
+
+    # Step 6: Apply ToASCII
+    label2 = ToASCII(result)
+
+    # Step 7: Compare the result of step 6 with the one of step 3
+    # label2 will already be in lower case.
+    if label.lower() != label2:
+        raise UnicodeError, ("IDNA does not round-trip", label, label2)
+
+    # Step 8: return the result of step 5
+    return result
+        
+### Codec APIs
+
+class Codec(codecs.Codec):
+    def encode(self,input,errors='strict'):
+
+        if errors != 'strict':
+            # IDNA is quite clear that implementations must be strict
+            raise UnicodeError, "unsupported error handling "+errors
+
+        result = []
+        for label in dots.split(input):
+            result.append(ToASCII(label))
+        # Join with U+002E
+        return ".".join(result), len(input)
+
+    def decode(self,input,errors='strict'):
+        
+        if errors != 'strict':
+            raise UnicodeError, "Unsupported error handling "+errors
+
+        # IDNA allows decoding to operate on Unicode strings, too.
+        if isinstance(input, unicode):
+            labels = dots.split(input)
+        else:
+            # Must be ASCII string
+            unicode(input, "ascii")
+            labels = input.split(".")
+
+        result = []
+        for label in labels:
+            result.append(ToUnicode(label))
+
+        return u".".join(result), len(input)
+
+class StreamWriter(Codec,codecs.StreamWriter):
+    pass
+
+class StreamReader(Codec,codecs.StreamReader):
+    pass
+
+### encodings module API
+
+def getregentry():
+
+    return (Codec().encode,Codec().decode,StreamReader,StreamWriter)