如何將字符串轉換爲base64格式的標準RFC-2045 MIME？

Question

我試圖將一個字符串轉換爲base64格式的標準RFC-2045。

我的代碼是

import base64 
auth_header = base64.b64encode('user:abcd'.decode('ascii')) 

是否使用RFC-2045

Answer 1

（在python Base64編碼）[https://docs.python.org/3/library/base64.html]不知道的base64標準：它提供了編碼和解碼的功能中指定的編碼RFC 3548，它定義了Base16，Base32和Base64算法，以及事實上的標準Ascii85和Base85編碼。

電子郵件使用RFC-2045 MIME。 參見：

encoding-of-headers-in-mimetext

文檔：

email.mime: Creating email and MIME objects from scratch

我想你要找的解決方案是Base64編碼與RFC 2045代碼，檢查：

# Copyright (C) 2002-2006 Python Software Foundation 
# Author: Ben Gertzfield 
# Contact: email-sig@python.org 

"""Base64 content transfer encoding per RFCs 2045-2047. 

This module handles the content transfer encoding method defined in RFC 2045 
to encode arbitrary 8-bit data using the three 8-bit bytes in four 7-bit 
characters encoding known as Base64. 

It is used in the MIME standards for email to attach images, audio, and text 
using some 8-bit character sets to messages. 

This module provides an interface to encode and decode both headers and bodies 
with Base64 encoding. 

RFC 2045 defines a method for including character set information in an 
`encoded-word' in a header. This method is commonly used for 8-bit real names 
in To:, From:, Cc:, etc. fields, as well as Subject: lines. 

This module does not do the line wrapping or end-of-line character conversion 
necessary for proper internationalized headers; it only does dumb encoding and 
decoding. To deal with the various line wrapping issues, use the email.Header 
module. 
""" 

__all__ = [ 
    'base64_len', 
    'body_decode', 
    'body_encode', 
    'decode', 
    'decodestring', 
    'encode', 
    'encodestring', 
    'header_encode', 
    ] 


from binascii import b2a_base64, a2b_base64 
from email.utils import fix_eols 

CRLF = '\r\n' 
NL = '\n' 
EMPTYSTRING = '' 

# See also Charset.py 
MISC_LEN = 7 



# Helpers 
def base64_len(s): 
    """Return the length of s when it is encoded with base64.""" 
    groups_of_3, leftover = divmod(len(s), 3) 
    # 4 bytes out for each 3 bytes (or nonzero fraction thereof) in. 
    # Thanks, Tim! 
    n = groups_of_3 * 4 
    if leftover: 
     n += 4 
    return n 



def header_encode(header, charset='iso-8859-1', keep_eols=False, 
        maxlinelen=76, eol=NL): 
    """Encode a single header line with Base64 encoding in a given charset. 

    Defined in RFC 2045, this Base64 encoding is identical to normal Base64 
    encoding, except that each line must be intelligently wrapped (respecting 
    the Base64 encoding), and subsequent lines must start with a space. 

    charset names the character set to use to encode the header. It defaults 
    to iso-8859-1. 

    End-of-line characters (\\r, \\n, \\r\\n) will be automatically converted 
    to the canonical email line separator \\r\\n unless the keep_eols 
    parameter is True (the default is False). 

    Each line of the header will be terminated in the value of eol, which 
    defaults to "\\n". Set this to "\\r\\n" if you are using the result of 
    this function directly in email. 

    The resulting string will be in the form: 

    "=?charset?b?WW/5ciBtYXp66XLrIHf8eiBhIGhhbXBzdGHuciBBIFlv+XIgbWF6euly?=\\n 
     =?charset?b?6yB3/HogYSBoYW1wc3Rh7nIgQkMgWW/5ciBtYXp66XLrIHf8eiBhIGhh?=" 

    with each line wrapped at, at most, maxlinelen characters (defaults to 76 
    characters). 
    """ 
    # Return empty headers unchanged 
    if not header: 
     return header 

    if not keep_eols: 
     header = fix_eols(header) 

    # Base64 encode each line, in encoded chunks no greater than maxlinelen in 
    # length, after the RFC chrome is added in. 
    base64ed = [] 
    max_encoded = maxlinelen - len(charset) - MISC_LEN 
    max_unencoded = max_encoded * 3 // 4 

    for i in range(0, len(header), max_unencoded): 
     base64ed.append(b2a_base64(header[i:i+max_unencoded])) 

    # Now add the RFC chrome to each encoded chunk 
    lines = [] 
    for line in base64ed: 
     # Ignore the last character of each line if it is a newline 
     if line.endswith(NL): 
      line = line[:-1] 
     # Add the chrome 
     lines.append('=?%s?b?%s?=' % (charset, line)) 
    # Glue the lines together and return it. BAW: should we be able to 
    # specify the leading whitespace in the joiner? 
    joiner = eol + ' ' 
    return joiner.join(lines) 



def encode(s, binary=True, maxlinelen=76, eol=NL): 
    """Encode a string with base64. 

    Each line will be wrapped at, at most, maxlinelen characters (defaults to 
    76 characters). 

    If binary is False, end-of-line characters will be converted to the 
    canonical email end-of-line sequence \\r\\n. Otherwise they will be left 
    verbatim (this is the default). 

    Each line of encoded text will end with eol, which defaults to "\\n". Set 
    this to "\r\n" if you will be using the result of this function directly 
    in an email. 
    """ 
    if not s: 
     return s 

    if not binary: 
     s = fix_eols(s) 

    encvec = [] 
    max_unencoded = maxlinelen * 3 // 4 
    for i in range(0, len(s), max_unencoded): 
     # BAW: should encode() inherit b2a_base64()'s dubious behavior in 
     # adding a newline to the encoded string? 
     enc = b2a_base64(s[i:i + max_unencoded]) 
     if enc.endswith(NL) and eol != NL: 
      enc = enc[:-1] + eol 
     encvec.append(enc) 
    return EMPTYSTRING.join(encvec) 


# For convenience and backwards compatibility w/ standard base64 module 
body_encode = encode 
encodestring = encode 



def decode(s, convert_eols=None): 
    """Decode a raw base64 string. 

    If convert_eols is set to a string value, all canonical email linefeeds, 
    e.g. "\\r\\n", in the decoded text will be converted to the value of 
    convert_eols. os.linesep is a good choice for convert_eols if you are 
    decoding a text attachment. 

    This function does not parse a full MIME header value encoded with 
    base64 (like =?iso-8895-1?b?bmloISBuaWgh?=) -- please use the high 
    level email.Header class for that functionality. 
    """ 
    if not s: 
     return s 

    dec = a2b_base64(s) 
    if convert_eols: 
     return dec.replace(CRLF, convert_eols) 
    return dec 


# For convenience and backwards compatibility w/ standard base64 module 
body_decode = decode 
decodestring = decode 

解決方案：

print(encode('user:abcd')) 

輸出：

dXNlcjphYmNk 

參考：base64mime.py