http: fix RFC conformance w.r.t. message length

We need to favor "Transfer-Encoding: chunked" over the value of
the Content-Length header.  We should also reject bogus,
duplicate and/or unreasonable values for both these, since they
can trigger unexpected behavior when combined with other HTTP
parsers in proxies such as varnish, nginx, haproxy, etc...

See RFC 7230 (and RFC 2616) for more details:

	https://tools.ietf.org/html/rfc7230
	https://www.rfc-editor.org/errata_search.php?rfc=7230

1 files changed, 24 insertions, 11 deletions

diff --git a/lib/PublicInbox/HTTP.pm b/lib/PublicInbox/HTTP.pm
index df328904..b73ce2d7 100644
--- a/lib/PublicInbox/HTTP.pm
+++ b/lib/PublicInbox/HTTP.pm
@@ -335,19 +335,31 @@ sub input_tmpfile ($) {
 
 sub input_prepare {
         my ($self, $env) = @_;
-        my $input;
-        my $len = $env->{CONTENT_LENGTH};
-        if ($len) {
-                if ($len > $MAX_REQUEST_BUFFER) {
-                        quit($self, 413);
-                        return;
-                }
-                $input = input_tmpfile($self);
-        } elsif (env_chunked($env)) {
+        my ($input, $len);
+
+        # rfc 7230 3.3.2, 3.3.3,: favor Transfer-Encoding over Content-Length
+        my $hte = $env->{HTTP_TRANSFER_ENCODING};
+        if (defined $hte) {
+                # rfc7230 3.3.3, point 3 says only chunked is accepted
+                # as the final encoding.  Since neither public-inbox-httpd,
+                # git-http-backend, or our WWW-related code uses "gzip",
+                # "deflate" or "compress" as the Transfer-Encoding, we'll
+                # reject them:
+                return quit($self, 400) if $hte !~ /\Achunked\z/i;
+
                 $len = CHUNK_START;
                 $input = input_tmpfile($self);
         } else {
-                $input = $null_io;
+                $len = $env->{CONTENT_LENGTH};
+                if (defined $len) {
+                        # rfc7230 3.3.3.4
+                        return quit($self, 400) if $len !~ /\A[0-9]+\z/;
+
+                        return quit($self, 413) if $len > $MAX_REQUEST_BUFFER;
+                        $input = $len ? input_tmpfile($self) : $null_io;
+                } else {
+                        $input = $null_io;
+                }
         }
 
         # TODO: expire idle clients on ENFILE / EMFILE
@@ -358,7 +370,7 @@ sub input_prepare {
         $self->{input_left} = $len || 0;
 }
 
-sub env_chunked { ($_[0]->{HTTP_TRANSFER_ENCODING} || '') =~ /\bchunked\b/i }
+sub env_chunked { ($_[0]->{HTTP_TRANSFER_ENCODING} // '') =~ /\Achunked\z/i }
 
 sub err ($$) {
         eval { $_[0]->{httpd}->{env}->{'psgi.errors'}->print($_[1]."\n") };
@@ -451,6 +463,7 @@ sub quit {
         my $h = "HTTP/1.1 $status " . status_message($status) . "\r\n\r\n";
         $self->write(\$h);
         $self->close;
+        undef; # input_prepare expects this
 }
 
 sub close {