Parsing MIME-encoded data in an HTTP request

[Ron Garret]

I'm writing a little HTTP server and need to parse request content that
is mime-encoded. All the MIME routines in the Python standard library
seem to have been subsumed into the email package, which makes this
operation a little awkward. It seems I have to do the following:

1. Extract the content-length header from the HTTP request and use that
to read the payload.

2. Stick some artificial-looking headers onto the beginning of this
payload to make it look like an email message (including the
content-type and content-transfer-encoding headers)

3. Parse the resulting string into a email message

That works, but it feels way too hackish for my tastes. Surely there
must be a better/more standard way of doing this?

Thanks,
rg

 

[s0suk3]

I'm writing a little HTTP server and need to parse request content that
is mime-encoded. All the MIME routines in the Python standard library
seem to have been subsumed into the email package, which makes this
operation a little awkward.

To deal with messages of that kind, I've seen modules such as
'rfc822', and 'mimetools' (which apparently builds itself from
'rfc822', so it might be more complete). There's also 'mimetypes', in
case you need to deal with file extensions and their corresponding
MIME media type.

It seems I have to do the following:

1. Extract the content-length header from the HTTP request and use that
to read the payload.

2. Stick some artificial-looking headers onto the beginning of this
payload to make it look like an email message (including the
content-type and content-transfer-encoding headers)

3. Parse the resulting string into a email message

Email? Why does an HTTP server need to build an email message?

I remember doing things like that some time ago when building an HTTP
server myself (http://code.google.com/p/sws-d/). Incidentally, I
resisted the urge to use much of the Python's library facilities (most
things are done manually; am I a knucklehead or what!? . You might
wanna take a look to get some ideas.

Sebastian

 

[Ron Garret]

To deal with messages of that kind, I've seen modules such as
'rfc822', and 'mimetools' (which apparently builds itself from
'rfc822', so it might be more complete). There's also 'mimetypes', in
case you need to deal with file extensions and their corresponding
MIME media type.

From the mimetools docs:

"Deprecated since release 2.3. The email package should be used in
preference to the module. This module is present only to maintain
backward compatibility."

Email? Why does an HTTP server need to build an email message?

It shouldn't. That's my whole point. But see the docs excerpt above.

I remember doing things like that some time ago when building an HTTP
server myself (http://code.google.com/p/sws-d/). Incidentally, I
resisted the urge to use much of the Python's library facilities (most
things are done manually; am I a knucklehead or what!? . You might
wanna take a look to get some ideas.

I'd much prefer not to reinvent this particular wheel.

rg

 

[Michael Ströder]

I'm writing a little HTTP server and need to parse request content that
is mime-encoded. All the MIME routines in the Python standard library
seem to have been subsumed into the email package, which makes this
operation a little awkward.

How about using cgi.parse_multipart()?

Ciao, Michael.

 

[Ron Garret]

How about using cgi.parse_multipart()?

Ciao, Michael.

Unfortunately cgi.parse_multipart doesn't handle nested multiparts,
which the requests I'm getting have. You have to use a FieldStorage
object to do that, and that only works if you're actually in a cgi
environment, which I am not. The server responds to these requests
directly.

Anyway, thanks for the idea.

rg

 

[Ron Garret]

Unfortunately cgi.parse_multipart doesn't handle nested multiparts,
which the requests I'm getting have. You have to use a FieldStorage
object to do that, and that only works if you're actually in a cgi
environment, which I am not. The server responds to these requests
directly.

Anyway, thanks for the idea.

rg

Hm, it actually seems to work if I manually pass in the outerboundary
parameter and environ={'REQUEST_METHOD':'POST'} That seems like the
Right Answer.

Woohoo!

Thanks Michael!

rg

 

[Michael Ströder]

Hm, it actually seems to work if I manually pass in the outerboundary
parameter and environ={'REQUEST_METHOD':'POST'} That seems like the
Right Answer.

I'm also using it to parse form parameters in a message body received by
POST.

CIao, Michael.

 

[Ron Garret]

I'm also using it to parse form parameters in a message body received by
POST.

CIao, Michael.

Just for the record, here's the incantation I ended up with:


class post_handler(BaseHTTPRequestHandler):
def do_POST(self):
form = cgi.FieldStorage(fp=self.rfile, headers=self.headers,
environ={'REQUEST_METHOD':'POST'})
...


works like a charm.

rg