What is the safest portable way to read a normal WSGI request body?

What is the safest portable way to read a normal WSGI request body?

1. Call environ["wsgi.input"].read() with no limit for every request.
2. Validate CONTENT_LENGTH, enforce an application byte limit, then read no more than the accepted length.
3. Read until a newline because HTTP bodies always end with one.
4. Trust a Content-Type header to impose the correct memory limit.