Decoding of payload of attachment

Hello,

I am have following code in my project:

decoder_map = {'base64': lambda payload: base64.b64decode(payload),
               '': lambda payload: payload.encode('utf-8'),
               '7bit': lambda payload: payload.encode('utf-8'),
               'quoted-printable': lambda payload: quopri.decodestring(payload)}
for msg_id in data[0].decode('utf-8').split():
    result_fetch, data = client.fetch(msg_id, "(RFC822)")

    if result_fetch != 'OK':
        raise Exception("Fetch failed!")

    raw_mail = data[0][1]
    mail = mailparser.parse_from_bytes(raw_mail)
    for attachment in mail.attachments:
        if attachment['content_transfer_encoding'] not in decoder_map:
            msg = "Unsupported Content-Transfer Encoding ({}) in msg {}.".format(attachment['content_transfer_encoding'], msg_id)
            raise RuntimeError(msg)

        decoder = decoder_map[attachment['content_transfer_encoding']]
        try:
            fp, fname = find_filename(attachment['filename'], args.attachment_dir)
            fp.write(decoder(attachment['payload']))
        except binascii.Error as e:
            print("Unable to parse attachment '{}'".format(attachment['filename']))
        finally:
            fp.close()

I think that this is not a fully-handled case of use. I had to introduce quite a lot of logic to save attachments that can be coded in a variety of ways.

[fedelemantuano]

I added the store attachments function in mail-parser command line:

$ mailparser -f my_mail -sa -ap /tmp/attachments

[fedelemantuano]

Hi @ad-m,

in mail-parser results there is a binary flag. If it’s true the sample is a binary, else it’s false is not binary. If you read this part of code you can see:

...
charset = p.get_content_charset('utf-8') # get the charset
...

            if filename:
                    binary = False
                    mail_content_type = ported_string(p.get_content_type())
                    transfer_encoding = ported_string(
                        p.get('content-transfer-encoding', '')).lower()

                    if transfer_encoding == "base64" or \
                            (transfer_encoding == "quoted-printable" and
                             "application" in mail_content_type):
                        payload = p.get_payload(decode=False)
                        binary = True
                    else:
                        payload = ported_string(
                            p.get_payload(decode=True), encoding=charset)

mail-parser gives you the correct payload, so you should do:

            if binary:
                with open(sample, "wb") as f:
                    f.write(payload.decode("base64"))
            else:
                with open(sample, "w") as f:
                    f.write(payload.encode("utf-8"))

That’s it