# HG changeset patch
# User Gregory Szorc <gregory.szorc@gmail.com>
# Date 1520707714 28800
# Node ID 290fc4c3d1e0d6f69adbac09b413b805ed4706f7
# Parent  7066617187c10b5cd17a6e4c26364a933b8bef38
hgweb: use a capped reader for WSGI input stream

Per PEP 3333, the input stream from WSGI should respect EOF and
prevent reads past the end of the request body. However, not all
WSGI servers guarantee this. Notably, our BaseHTTPServer based
built-in HTTP server doesn't. Instead, it exposes the raw socket
and you can read() from it all you want, getting the connection in
a bad state by doing so.

We have a "cappedreader" utility class that proxies a file object
and prevents reading past a limit.

This commit converts the WSGI input stream into a capped reader when
the input length is advertised via Content-Length headers.

"cappedreader" only exposes a read() method. PEP 3333 states that
the input stream MUST also support readline(), readlines(hint), and
__iter__(). However, since our WSGI application code only calls
read() and since we're not manipulating the stream exposed by the
WSGI server, we're not violating the spec here.

Differential Revision: https://phab.mercurial-scm.org/D2768

diff -r 7066617187c1 -r 290fc4c3d1e0 mercurial/hgweb/request.py
--- a/mercurial/hgweb/request.py	Sat Mar 10 10:47:30 2018 -0800
+++ b/mercurial/hgweb/request.py	Sat Mar 10 10:48:34 2018 -0800
@@ -234,6 +234,14 @@
             raise RuntimeError("Unknown and unsupported WSGI version %d.%d"
                                % version)
         self.inp = wsgienv[r'wsgi.input']
+
+        if r'HTTP_CONTENT_LENGTH' in wsgienv:
+            self.inp = util.cappedreader(self.inp,
+                                         int(wsgienv[r'HTTP_CONTENT_LENGTH']))
+        elif r'CONTENT_LENGTH' in wsgienv:
+            self.inp = util.cappedreader(self.inp,
+                                         int(wsgienv[r'CONTENT_LENGTH']))
+
         self.err = wsgienv[r'wsgi.errors']
         self.threaded = wsgienv[r'wsgi.multithread']
         self.multiprocess = wsgienv[r'wsgi.multiprocess']