webrick/httprequest: limit request headers size

We use the same 112 KB limit started (AFAIK) by Mongrel, Thin,
and Puma to prevent malicious users from using up all the memory
with a single request.  This also limits the damage done by
excessive ranges in multipart Range: requests.

Due to the way we rely on IO#gets and the desire to keep
the code simple, the actual maximum header may be 4093 bytes
larger than 112 KB, but we're splitting hairs at that point.

* lib/webrick/httprequest.rb: define MAX_HEADER_LENGTH
  (read_header): raise when headers exceed max length

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_5@62979 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 8 insertions, 1 deletions

diff --git a/lib/webrick/httprequest.rb b/lib/webrick/httprequest.rb
index 10cf72d288..551ef0b08f 100644
--- a/lib/webrick/httprequest.rb
+++ b/lib/webrick/httprequest.rb
@@ -414,9 +414,13 @@ module WEBrick
 
     MAX_URI_LENGTH = 2083 # :nodoc:
 
+    # same as Mongrel, Thin and Puma
+    MAX_HEADER_LENGTH = (112 * 1024) # :nodoc:
+
     def read_request_line(socket)
       @request_line = read_line(socket, MAX_URI_LENGTH) if socket
-      if @request_line.bytesize >= MAX_URI_LENGTH and @request_line[-1, 1] != LF
+      @request_bytes = @request_line.bytesize
+      if @request_bytes >= MAX_URI_LENGTH and @request_line[-1, 1] != LF
         raise HTTPStatus::RequestURITooLarge
       end
       @request_time = Time.now
@@ -435,6 +439,9 @@ module WEBrick
       if socket
         while line = read_line(socket)
           break if /\A(#{CRLF}|#{LF})\z/om =~ line
+          if (@request_bytes += line.bytesize) > MAX_HEADER_LENGTH
+            raise HTTPStatus::RequestEntityTooLarge, 'headers too large'
+          end
           @raw_header << line
         end
       end