#!/usr/bin/env python

# Decode From and Subject lines spammers encode in other charsets

# to try to hide them from spam filters. (RFC 2047 encoding.)

# Use in conjunction with programs like procmail or spamassassin,

# instead of something like formail

import sys, os

import email

import email.utils

Debug = False

progname = os.path.basename(sys.argv[0])

Usage = """Usage: %s [-a] headername [filename]

Find a line matching the given header name (Subject:, From:, etc.)

and decode it according to RFC 2047.

Without a filemame, will read standard input.

Adding -a will print all matches within the given file, not just the first.

Multiple headers may be combined with |

Example: %s -a Subject: /var/mail/yourname

%s -a 'Subject:|To:|From:' folder folder""" % (progname, progname,

progname)

def decode_piece(piece):

ret = ''

for part in email.Header.decode_header(piece):

ret += part[0]

# Special case: the header itself comes out with charset None

# and decode doesn't add a space between it and the next part,

# even though there was a space in the original. So add one.

# I'm taking a wild guess that the relevant factor here is

# the None charset rather than the fact that it matched

# the header, but keep an eye open for counterexamples.

if not part[1]:

ret += ' '

return ret

def decode_file(filename, header_wanted, all=False):

if filename == '-':

fil = sys.stdin

else:

fil = open(filename)

# header_wanted can be multiple headers, e.g. From:|To:

# so split them.

headers = header_wanted.split('|')

output = ''

found_something = False

for line in fil:

# if Debug:

# print "line:", line

# If it matches the header we seek, or if we've already started

# matching the header and we're looking for continuation lines,

# build up our string:

for header_wanted in headers:

# if Debug:

# print "=== looking for", header_wanted

if (not output and line.startswith(header_wanted)) \

or (output and (line.startswith(' ') or line.startswith('\t'))):

# We have a match! But we may need to read multiple lines,

# since one header can be split over several lines.

found_something = True

if Debug:

print "\nFound something:", line

print " which decodes to:", decode_piece(line.strip())

# Strip output because we don't want the final newline.

# But add a space if this is a continuation.

if output:

output += ' '

thispiece = decode_piece(line.strip())

if Debug:

print "decode_piece returned: '%s'" % thispiece

# If the header is an address, we have to split it into parts

# before we can decode it. If it's another header

# such as Subject, we can't do that.

if header_wanted.startswith("From") \

or header_wanted.startswith("To") \

or header_wanted.startswith("Cc") \

or header_wanted.startswith("Bcc"):

pieces = email.utils.parseaddr(thispiece)

if pieces[0] or pieces[1]:

if Debug:

print "formataddr says: '%s'" % \

email.utils.formataddr(map(decode_piece, pieces)).strip()

output += header_wanted + ' ' + \

email.utils.formataddr(map(decode_piece,

pieces)).strip()

else:

output += thispiece

print "parseaddr failed on", thispiece,

else:

output += thispiece

if Debug:

print "Now output is ---%s---" % output

elif output:

# if we've already matched the header, and this isn't a

# continuation line, then we're done. Print and exit.

if Debug:

print "output:", output

print "stripped output:",

print output.strip()

if all:

output = ''

else:

sys.exit(0)

if output:

if Debug:

print "final output:",

print output.strip()

# If we get here, we never matched a header,

# or ended with a continuation line.

if not found_something:

print "No such header", header_wanted, "in", filename

return

if sys.argv[1] == '-h' or sys.argv[1] == '--help':

print Usage

sys.exit(1)

# A -a argument means don't stop at the first header,

# decode all matching headers in the file.

if sys.argv[1] == '-a':

all = True

sys.argv = sys.argv[1:]

else:

all = False

header_wanted = sys.argv[1]

try:

if len(sys.argv) > 2:

for filename in sys.argv[2:]:

decode_file(filename, header_wanted, all)

else:

fil = sys.stdin

decode_file('-', header_wanted)

except KeyboardInterrupt:

sys.exit(1)