Before services like Dropbox were widely available, some people (including me) were using their Gmail account as a primitive backup solution: Compress your directory and send it to your gmail. There. Backup complete.
However, nothing is so easy…
Recently, I wanted to retrieve one of these backups, a .rar containing the complete source code (since it was written in TeX) of my PhD thesis. The problem was that Gmail blocked the access to these attachments saying
Anti-virus warning – 1 attachment contains a virus or blocked file. Downloading this attachment is disabled.
probably because I had a number of .bat files inside that .rar archive to automate my work 🙁
Now what ?
After searching the internet and not founding any solutions, I tried the options that gmail gives for each email. One particular one cought my interest: Show original
Clicking this option opened a text file with the original, MIME encoded message. The interesting thing of course was
------=_NextPart_000_004F_01CA0AED.E63C2A30
Content-Type: application/octet-stream;
name="phdstuff.rar"
Content-Transfer-Encoding: base64
Content-Disposition: attachment;
filename="phdstuff.rar"
UmFyIRoHAM+QcwAADQAAAAAAAAB0f3TAgCwANAMAAFQEAAACRbXCx8lr9TodMwwAIAAAAG5ld2Zp
bmFsLnR4dA3dEQzM082BF7sB+D3q6QPUNEfwG7vHQgNkiQDTkGvfhOE4mNltIJJlBFMOCQPzPeKD
...
So the whole attachment was contained in that text file, encoded in base64! Now I just needed to extract it from the email and convert it back to binary.
Important: Before going the python way, please check the 2 June 2015 update at the end of the article for an easier solution!
This was very easy to do using Python – some people had already asked the same thing on SO. So here’s a simple program that gets an email in text/mime format as input and dumps all attachments:
import email
import sys
if __name__=='__main__':
if len(sys.argv)<2:
print "Please enter a file to extract attachments from"
sys.exit(1)
msg = email.message_from_file(open(sys.argv[1]))
for pl in msg.get_payload():
if pl.get_filename(): # if it is an attachment
open(pl.get_filename(), 'wb').write(pl.get_payload(decode=True))
Save this to a file named get_attachments.py and, after saving the original message to a file named 0.txt run python get_attachments.py 0.txt and you’ll see the attachments of your email in the same folder!
说白了，就是把上面的代码保存为get_attachments.py文件，然后在同级目录下运行下面的代码：
python get_attachments.py 0.txt
（要确保你的电脑已经安装了python，Linux和os x默认都是已经安装的）
Disclaimer: I have to warn you that since Gmail claims that an attachment is not safe it may be actually not safe. So you must be 100% sure that you know what you are doing before retrievening your email attachments like this.
Update: Stefan created an improved version of the attachment extractor which is also compatible with Python 3.4!
也可以参数这篇文章的方式： at his article
