57 lines
2.0 KiB
Python
57 lines
2.0 KiB
Python
from collections import namedtuple
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import hashing
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# Entry(bytes[32], bytes[32], bytes[32], bytes[0…2¹⁶-1])
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Entry = namedtuple('Entry', ['salt', 'hashed_host', 'fingerprint', 'comment'])
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class UnacceptableComment(Exception): pass
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def normalize_host(domain, port):
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"""normalize_host(str, u16) → bytes
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Tranform a domain into the format in which it will be hashed"""
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assert type(domain) == str
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assert type(port) == int and 0 <= port <= (1<<16) - 1
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# We want to have domain names reasonably normalized. This is why we
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# convert all internationalized domain names to punycode and
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# lowercase all domains.
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# The reason the lowercasing happens after the punycoding is because
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# that way we don't have to worry about Unicode case mapping: in
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# case of IDN the IDNA codec handles that for us, and in case of an
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# ASCII domain it passes through the IDNA unmodified
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normalized_host = domain.encode('idna').lower()
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# If the port is not :22, we store [host]:port instead
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if port != 22:
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normalized_host = b'[%s]:%i' % (normalized_host, port)
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return normalized_host
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def create_entry(domain, port, fingerprint, comment):
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"""create_entry(str, u16, bytes[32], str) → Entry
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Given unprocessed host, a binary fingerprint and a comment, creates
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and entry describing it"""
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assert type(domain) == str
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assert type(port) == int and 0 <= port <= (1<<16) - 1
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assert type(fingerprint) == bytes and len(fingerprint) == 32
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assert type(comment) == str
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# Normalize the host before hashing
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normalized_host = normalize_host(domain, port)
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# Hash the host and store the salt
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salt, hashed_host = hashing.hash_host(normalized_host)
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# Comment must not include newlines
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if '\n' in comment:
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raise UnacceptableComment('Comment contains newlines')
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comment_encoded = comment.encode('utf-8')
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# Comment may be at max 2¹⁶-1 bytes long
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if len(comment_encoded) >= 1<<16:
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raise UnacceptableComment('Comment length of %i bytes is too long' % len(comment_encoded))
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return Entry(salt, hashed_host, fingerprint, comment_encoded)
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