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# This module implements the RFCs 3490 (IDNA) and 3491 (Nameprep) 

 

import stringprep, re, codecs 

from unicodedata import ucd_3_2_0 as unicodedata 

 

# IDNA section 3.1 

dots = re.compile("[\u002E\u3002\uFF0E\uFF61]") 

 

# IDNA section 5 

ace_prefix = b"xn--" 

sace_prefix = "xn--" 

 

# 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 = "".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 %r" % c) 

 

# Check bidi 

RandAL = [stringprep.in_table_d1(x) for x in 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 any(stringprep.in_table_d2(x) for x in 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 empty or 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 empty or too long") 

 

# Step 5: Check ACE prefix 

if label.startswith(sace_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 empty or too long") 

 

def ToUnicode(label): 

# Step 1: Check for ASCII 

if isinstance(label, bytes): 

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 str(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 str(label, "ascii").lower() != str(label2, "ascii"): 

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) 

 

if not input: 

return b'', 0 

 

try: 

result = input.encode('ascii') 

except UnicodeEncodeError: 

pass 

else: 

# ASCII name: fast path 

labels = result.split(b'.') 

for label in labels[:-1]: 

if not (0 < len(label) < 64): 

raise UnicodeError("label empty or too long") 

if len(labels[-1]) >= 64: 

raise UnicodeError("label too long") 

return result, len(input) 

 

result = bytearray() 

labels = dots.split(input) 

if labels and not labels[-1]: 

trailing_dot = b'.' 

del labels[-1] 

else: 

trailing_dot = b'' 

for label in labels: 

if result: 

# Join with U+002E 

result.extend(b'.') 

result.extend(ToASCII(label)) 

return bytes(result+trailing_dot), len(input) 

 

def decode(self, input, errors='strict'): 

 

if errors != 'strict': 

raise UnicodeError("Unsupported error handling "+errors) 

 

if not input: 

return "", 0 

 

# IDNA allows decoding to operate on Unicode strings, too. 

if not isinstance(input, bytes): 

# XXX obviously wrong, see #3232 

input = bytes(input) 

 

if ace_prefix not in input: 

# Fast path 

try: 

return input.decode('ascii'), len(input) 

except UnicodeDecodeError: 

pass 

 

labels = input.split(b".") 

 

if labels and len(labels[-1]) == 0: 

trailing_dot = '.' 

del labels[-1] 

else: 

trailing_dot = '' 

 

result = [] 

for label in labels: 

result.append(ToUnicode(label)) 

 

return ".".join(result)+trailing_dot, len(input) 

 

class IncrementalEncoder(codecs.BufferedIncrementalEncoder): 

def _buffer_encode(self, input, errors, final): 

if errors != 'strict': 

# IDNA is quite clear that implementations must be strict 

raise UnicodeError("unsupported error handling "+errors) 

 

if not input: 

return (b'', 0) 

 

labels = dots.split(input) 

trailing_dot = b'' 

if labels: 

if not labels[-1]: 

trailing_dot = b'.' 

del labels[-1] 

elif not final: 

# Keep potentially unfinished label until the next call 

del labels[-1] 

if labels: 

trailing_dot = b'.' 

 

result = bytearray() 

size = 0 

for label in labels: 

if size: 

# Join with U+002E 

result.extend(b'.') 

size += 1 

result.extend(ToASCII(label)) 

size += len(label) 

 

result += trailing_dot 

size += len(trailing_dot) 

return (bytes(result), size) 

 

class IncrementalDecoder(codecs.BufferedIncrementalDecoder): 

def _buffer_decode(self, input, errors, final): 

if errors != 'strict': 

raise UnicodeError("Unsupported error handling "+errors) 

 

if not input: 

return ("", 0) 

 

# IDNA allows decoding to operate on Unicode strings, too. 

if isinstance(input, str): 

labels = dots.split(input) 

else: 

# Must be ASCII string 

input = str(input, "ascii") 

labels = input.split(".") 

 

trailing_dot = '' 

if labels: 

if not labels[-1]: 

trailing_dot = '.' 

del labels[-1] 

elif not final: 

# Keep potentially unfinished label until the next call 

del labels[-1] 

if labels: 

trailing_dot = '.' 

 

result = [] 

size = 0 

for label in labels: 

result.append(ToUnicode(label)) 

if size: 

size += 1 

size += len(label) 

 

result = ".".join(result) + trailing_dot 

size += len(trailing_dot) 

return (result, size) 

 

class StreamWriter(Codec,codecs.StreamWriter): 

pass 

 

class StreamReader(Codec,codecs.StreamReader): 

pass 

 

### encodings module API 

 

def getregentry(): 

return codecs.CodecInfo( 

name='idna', 

encode=Codec().encode, 

decode=Codec().decode, 

incrementalencoder=IncrementalEncoder, 

incrementaldecoder=IncrementalDecoder, 

streamwriter=StreamWriter, 

streamreader=StreamReader, 

)