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1import binascii
2import email.charset
3import email.message
4import email.errors
5from email import quoprimime
6
7class ContentManager:
8
9    def __init__(self):
10        self.get_handlers = {}
11        self.set_handlers = {}
12
13    def add_get_handler(self, key, handler):
14        self.get_handlers[key] = handler
15
16    def get_content(self, msg, *args, **kw):
17        content_type = msg.get_content_type()
18        if content_type in self.get_handlers:
19            return self.get_handlers[content_type](msg, *args, **kw)
20        maintype = msg.get_content_maintype()
21        if maintype in self.get_handlers:
22            return self.get_handlers[maintype](msg, *args, **kw)
23        if '' in self.get_handlers:
24            return self.get_handlers[''](msg, *args, **kw)
25        raise KeyError(content_type)
26
27    def add_set_handler(self, typekey, handler):
28        self.set_handlers[typekey] = handler
29
30    def set_content(self, msg, obj, *args, **kw):
31        if msg.get_content_maintype() == 'multipart':
32            # XXX: is this error a good idea or not?  We can remove it later,
33            # but we can't add it later, so do it for now.
34            raise TypeError("set_content not valid on multipart")
35        handler = self._find_set_handler(msg, obj)
36        msg.clear_content()
37        handler(msg, obj, *args, **kw)
38
39    def _find_set_handler(self, msg, obj):
40        full_path_for_error = None
41        for typ in type(obj).__mro__:
42            if typ in self.set_handlers:
43                return self.set_handlers[typ]
44            qname = typ.__qualname__
45            modname = getattr(typ, '__module__', '')
46            full_path = '.'.join((modname, qname)) if modname else qname
47            if full_path_for_error is None:
48                full_path_for_error = full_path
49            if full_path in self.set_handlers:
50                return self.set_handlers[full_path]
51            if qname in self.set_handlers:
52                return self.set_handlers[qname]
53            name = typ.__name__
54            if name in self.set_handlers:
55                return self.set_handlers[name]
56        if None in self.set_handlers:
57            return self.set_handlers[None]
58        raise KeyError(full_path_for_error)
59
60
61raw_data_manager = ContentManager()
62
63
64def get_text_content(msg, errors='replace'):
65    content = msg.get_payload(decode=True)
66    charset = msg.get_param('charset', 'ASCII')
67    return content.decode(charset, errors=errors)
68raw_data_manager.add_get_handler('text', get_text_content)
69
70
71def get_non_text_content(msg):
72    return msg.get_payload(decode=True)
73for maintype in 'audio image video application'.split():
74    raw_data_manager.add_get_handler(maintype, get_non_text_content)
75
76
77def get_message_content(msg):
78    return msg.get_payload(0)
79for subtype in 'rfc822 external-body'.split():
80    raw_data_manager.add_get_handler('message/'+subtype, get_message_content)
81
82
83def get_and_fixup_unknown_message_content(msg):
84    # If we don't understand a message subtype, we are supposed to treat it as
85    # if it were application/octet-stream, per
86    # tools.ietf.org/html/rfc2046#section-5.2.4.  Feedparser doesn't do that,
87    # so do our best to fix things up.  Note that it is *not* appropriate to
88    # model message/partial content as Message objects, so they are handled
89    # here as well.  (How to reassemble them is out of scope for this comment :)
90    return bytes(msg.get_payload(0))
91raw_data_manager.add_get_handler('message',
92                                 get_and_fixup_unknown_message_content)
93
94
95def _prepare_set(msg, maintype, subtype, headers):
96    msg['Content-Type'] = '/'.join((maintype, subtype))
97    if headers:
98        if not hasattr(headers[0], 'name'):
99            mp = msg.policy
100            headers = [mp.header_factory(*mp.header_source_parse([header]))
101                       for header in headers]
102        try:
103            for header in headers:
104                if header.defects:
105                    raise header.defects[0]
106                msg[header.name] = header
107        except email.errors.HeaderDefect as exc:
108            raise ValueError("Invalid header: {}".format(
109                                header.fold(policy=msg.policy))) from exc
110
111
112def _finalize_set(msg, disposition, filename, cid, params):
113    if disposition is None and filename is not None:
114        disposition = 'attachment'
115    if disposition is not None:
116        msg['Content-Disposition'] = disposition
117    if filename is not None:
118        msg.set_param('filename',
119                      filename,
120                      header='Content-Disposition',
121                      replace=True)
122    if cid is not None:
123        msg['Content-ID'] = cid
124    if params is not None:
125        for key, value in params.items():
126            msg.set_param(key, value)
127
128
129# XXX: This is a cleaned-up version of base64mime.body_encode (including a bug
130# fix in the calculation of unencoded_bytes_per_line).  It would be nice to
131# drop both this and quoprimime.body_encode in favor of enhanced binascii
132# routines that accepted a max_line_length parameter.
133def _encode_base64(data, max_line_length):
134    encoded_lines = []
135    unencoded_bytes_per_line = max_line_length // 4 * 3
136    for i in range(0, len(data), unencoded_bytes_per_line):
137        thisline = data[i:i+unencoded_bytes_per_line]
138        encoded_lines.append(binascii.b2a_base64(thisline).decode('ascii'))
139    return ''.join(encoded_lines)
140
141
142def _encode_text(string, charset, cte, policy):
143    lines = string.encode(charset).splitlines()
144    linesep = policy.linesep.encode('ascii')
145    def embedded_body(lines): return linesep.join(lines) + linesep
146    def normal_body(lines): return b'\n'.join(lines) + b'\n'
147    if cte is None:
148        # Use heuristics to decide on the "best" encoding.
149        if max((len(x) for x in lines), default=0) <= policy.max_line_length:
150            try:
151                return '7bit', normal_body(lines).decode('ascii')
152            except UnicodeDecodeError:
153                pass
154            if policy.cte_type == '8bit':
155                return '8bit', normal_body(lines).decode('ascii', 'surrogateescape')
156        sniff = embedded_body(lines[:10])
157        sniff_qp = quoprimime.body_encode(sniff.decode('latin-1'),
158                                          policy.max_line_length)
159        sniff_base64 = binascii.b2a_base64(sniff)
160        # This is a little unfair to qp; it includes lineseps, base64 doesn't.
161        if len(sniff_qp) > len(sniff_base64):
162            cte = 'base64'
163        else:
164            cte = 'quoted-printable'
165            if len(lines) <= 10:
166                return cte, sniff_qp
167    if cte == '7bit':
168        data = normal_body(lines).decode('ascii')
169    elif cte == '8bit':
170        data = normal_body(lines).decode('ascii', 'surrogateescape')
171    elif cte == 'quoted-printable':
172        data = quoprimime.body_encode(normal_body(lines).decode('latin-1'),
173                                      policy.max_line_length)
174    elif cte == 'base64':
175        data = _encode_base64(embedded_body(lines), policy.max_line_length)
176    else:
177        raise ValueError("Unknown content transfer encoding {}".format(cte))
178    return cte, data
179
180
181def set_text_content(msg, string, subtype="plain", charset='utf-8', cte=None,
182                     disposition=None, filename=None, cid=None,
183                     params=None, headers=None):
184    _prepare_set(msg, 'text', subtype, headers)
185    cte, payload = _encode_text(string, charset, cte, msg.policy)
186    msg.set_payload(payload)
187    msg.set_param('charset',
188                  email.charset.ALIASES.get(charset, charset),
189                  replace=True)
190    msg['Content-Transfer-Encoding'] = cte
191    _finalize_set(msg, disposition, filename, cid, params)
192raw_data_manager.add_set_handler(str, set_text_content)
193
194
195def set_message_content(msg, message, subtype="rfc822", cte=None,
196                       disposition=None, filename=None, cid=None,
197                       params=None, headers=None):
198    if subtype == 'partial':
199        raise ValueError("message/partial is not supported for Message objects")
200    if subtype == 'rfc822':
201        if cte not in (None, '7bit', '8bit', 'binary'):
202            # http://tools.ietf.org/html/rfc2046#section-5.2.1 mandate.
203            raise ValueError(
204                "message/rfc822 parts do not support cte={}".format(cte))
205        # 8bit will get coerced on serialization if policy.cte_type='7bit'.  We
206        # may end up claiming 8bit when it isn't needed, but the only negative
207        # result of that should be a gateway that needs to coerce to 7bit
208        # having to look through the whole embedded message to discover whether
209        # or not it actually has to do anything.
210        cte = '8bit' if cte is None else cte
211    elif subtype == 'external-body':
212        if cte not in (None, '7bit'):
213            # http://tools.ietf.org/html/rfc2046#section-5.2.3 mandate.
214            raise ValueError(
215                "message/external-body parts do not support cte={}".format(cte))
216        cte = '7bit'
217    elif cte is None:
218        # http://tools.ietf.org/html/rfc2046#section-5.2.4 says all future
219        # subtypes should be restricted to 7bit, so assume that.
220        cte = '7bit'
221    _prepare_set(msg, 'message', subtype, headers)
222    msg.set_payload([message])
223    msg['Content-Transfer-Encoding'] = cte
224    _finalize_set(msg, disposition, filename, cid, params)
225raw_data_manager.add_set_handler(email.message.Message, set_message_content)
226
227
228def set_bytes_content(msg, data, maintype, subtype, cte='base64',
229                     disposition=None, filename=None, cid=None,
230                     params=None, headers=None):
231    _prepare_set(msg, maintype, subtype, headers)
232    if cte == 'base64':
233        data = _encode_base64(data, max_line_length=msg.policy.max_line_length)
234    elif cte == 'quoted-printable':
235        # XXX: quoprimime.body_encode won't encode newline characters in data,
236        # so we can't use it.  This means max_line_length is ignored.  Another
237        # bug to fix later.  (Note: encoders.quopri is broken on line ends.)
238        data = binascii.b2a_qp(data, istext=False, header=False, quotetabs=True)
239        data = data.decode('ascii')
240    elif cte == '7bit':
241        data = data.decode('ascii')
242    elif cte in ('8bit', 'binary'):
243        data = data.decode('ascii', 'surrogateescape')
244    msg.set_payload(data)
245    msg['Content-Transfer-Encoding'] = cte
246    _finalize_set(msg, disposition, filename, cid, params)
247for typ in (bytes, bytearray, memoryview):
248    raw_data_manager.add_set_handler(typ, set_bytes_content)
249