Multiple CVE backport

README.md

@@ -245,6 +245,15 @@ Set to 0 for no limit.
 Can also be set via the `RACK_MULTIPART_TOTAL_PART_LIMIT` environment variable.
 
 
+### multipart_buffered_upload_bytesize_limit
+
+The limit of the bytesize of all multipart parts (header and body), excluding the (body) of parts with a "filename".
+
+Defaults to 16 MB, which means it is not possible for multipart forms to contain form data of a total size greater than 16 MB. Uploaded files can be larger.
+
+Can also be set via the `RACK_MULTIPART_BUFFERED_UPLOAD_BYTESIZE_LIMIT` environment variable.
+
+
 ## History
 
 See <https://github.com/rack/HISTORY.md>.

lib/rack/mock.rb

@@ -134,7 +134,7 @@ def self.env_for(uri="", opts={})
       rack_input.set_encoding(Encoding::BINARY) if rack_input.respond_to?(:set_encoding)
       env['rack.input'] = rack_input
 
-      env["CONTENT_LENGTH"] ||= env["rack.input"].length.to_s
+      env["CONTENT_LENGTH"] ||= env["rack.input"].length.to_s if env["rack.input"].respond_to?(:length)
 
       opts.each { |field, value|
         env[field] = value  if String === field

lib/rack/multipart/parser.rb

@@ -8,6 +8,7 @@ class MultipartTotalPartLimitError < StandardError; end
     class Parser
       BUFSIZE = 16384
       DUMMY = Struct.new(:parse).new
+      MIME_HEADER_BYTESIZE_LIMIT = 64 * 1024
 
       def self.create(env)
         return DUMMY unless env['CONTENT_TYPE'] =~ MULTIPART
@@ -40,6 +41,7 @@ def initialize(boundary, io, content_length, env, tempfile, bufsize)
         @env = env
         @tempfile       = tempfile
         @bufsize        = bufsize
+        @retained_size  = 0
 
         if @content_length
           @content_length -= @boundary_size
@@ -70,13 +72,14 @@ def parse
             parts += 1
             if parts >= Utils.multipart_total_part_limit
               close_tempfiles
-              raise MultipartTotalPartLimitError, 'Maximum total multiparts in content reached' 
+              raise MultipartTotalPartLimitError, 'Maximum total multiparts in content reached'
             end
           end
 
           # Save the rest.
           if i = @buf.index(rx)
             body << @buf.slice!(0, i)
+            update_retained_size(i) unless filename
             @buf.slice!(0, @boundary_size+2)
 
             @content_length = -1  if $1 == "--"
@@ -133,6 +136,7 @@ def get_current_head_and_filename_and_content_type_and_name_and_body
 
             @buf.slice!(0, 2)          # Second \r\n
 
+            update_retained_size(head.bytesize)
             content_type = head[MULTIPART_CONTENT_TYPE, 1]
             name = head[MULTIPART_CONTENT_DISPOSITION, 1] || head[MULTIPART_CONTENT_ID, 1]
 
@@ -151,14 +155,19 @@ def get_current_head_and_filename_and_content_type_and_name_and_body
           end
 
           # Save the read body part.
-          if head && (@boundary_size+4 < @buf.size)
+          size_to_read = @buf.size - (@boundary_size+4)
+          if head && size_to_read > 0
             body << @buf.slice!(0, @buf.size - (@boundary_size+4))
+            update_retained_size(size_to_read) unless filename
           end
 
           content = @io.read(@content_length && @bufsize >= @content_length ? @content_length : @bufsize)
           raise EOFError, "bad content body"  if content.nil? || content.empty?
 
           @buf << content
+
+          raise EOFError, "multipart mime part header too large" if @buf.size > MIME_HEADER_BYTESIZE_LIMIT
+
           @content_length -= content.size if @content_length
         end
 
@@ -265,6 +274,13 @@ def get_data(filename, body, content_type, name, head)
 
         yield data
       end
+
+      def update_retained_size(size)
+        @retained_size += size
+        if @retained_size > Utils.buffered_upload_bytesize_limit
+          raise EOFError, "multipart data over retained size limit"
+        end
+      end
     end
   end
 end

lib/rack/request.rb

@@ -209,7 +209,10 @@ def POST
         @env["rack.request.form_hash"]
       elsif form_data? || parseable_data?
         unless @env["rack.request.form_hash"] = parse_multipart(env)
-          form_vars = @env["rack.input"].read
+          # Add 2 bytes. One to check whether it is over the limit, and a second
+          # in case the slice! call below removes the last byte
+          # If read returns nil, use the empty string
+          form_vars = @env["rack.input"].read(Rack::Utils.bytesize_limit + 2) || ''
 
           # Fix for Safari Ajax postings that always append \0
           # form_vars.sub!(/\0\z/, '') # performance replacement:

lib/rack/sendfile.rb

@@ -41,18 +41,23 @@ module Rack
   #     proxy_set_header   X-Real-IP           $remote_addr;
   #     proxy_set_header   X-Forwarded-For     $proxy_add_x_forwarded_for;
   #
-  #     proxy_set_header   X-Sendfile-Type     X-Accel-Redirect;
   #     proxy_set_header   X-Accel-Mapping     /var/www/=/files/;
   #
   #     proxy_pass         http://127.0.0.1:8080/;
   #   }
   #
-  # Note that the X-Sendfile-Type header must be set exactly as shown above.
   # The X-Accel-Mapping header should specify the location on the file system,
   # followed by an equals sign (=), followed name of the private URL pattern
   # that it maps to. The middleware performs a simple substitution on the
   # resulting path.
   #
+  #  # To enable X-Accel-Redirect, you must configure the middleware explicitly:
+  #
+  #   use Rack::Sendfile, "X-Accel-Redirect"
+  #
+  # For security reasons, "X-Accel-Redirect" may not be set via the X-Sendfile-Type header.
+  # The sendfile variation must be set via the middleware constructor.
+  #
   # See Also: http://wiki.codemongers.com/NginxXSendfile
   #
   # === lighttpd
@@ -97,9 +102,23 @@ module Rack
   # X-Accel-Mapping header. Mappings should be provided in tuples of internal to
   # external. The internal values may contain regular expression syntax, they
   # will be matched with case indifference.
+  #
+  # When X-Accel-Redirect is explicitly enabled via the variation parameter,
+  # and no application-level mappings are provided, the middleware will read
+  # the X-Accel-Mapping header from the proxy. This allows nginx to control
+  # the path mapping without requiring application-level configuration.
+  #
+  # === Security
+  #
+  # For security reasons, the X-Sendfile-Type header from HTTP requests may only
+  # be set to "X-Sendfile" or "X-Lighttpd-Send-File". Other values such as
+  # "X-Accel-Redirect" are not permitted to prevent information disclosure
+  # vulnerabilities where attackers could bypass proxy restrictions.
+
 
   class Sendfile
     F = ::File
+    SAFE_SENDFILE_VARIATIONS = ['X-Sendfile', 'X-Lighttpd-Send-File']
 
     def initialize(app, variation=nil, mappings=[])
       @app = app
@@ -142,16 +161,36 @@ def call(env)
     end
 
     private
+
+    def x_sendfile_type(env)
+      sendfile_type = env['HTTP_X_SENDFILE_TYPE']
+      if SAFE_SENDFILE_VARIATIONS.include?(sendfile_type)
+        sendfile_type
+      else
+        env['rack.errors'].puts "Unknown or unsafe x-sendfile variation: #{sendfile_type.inspect}"
+      end
+    end
+
     def variation(env)
       @variation ||
         env['sendfile.type'] ||
-        env['HTTP_X_SENDFILE_TYPE']
+        x_sendfile_type(env)
+    end
+
+    def x_accel_mapping(env)
+      # Only allow header when:
+      # 1. X-Accel-Redirect is explicitly enabled via constructor.
+      # 2. No application-level mappings are configured.
+      return nil unless @variation == 'X-Accel-Redirect'
+
+      env['HTTP_X_ACCEL_MAPPING']
     end
 
     def map_accel_path(env, path)
       if mapping = @mappings.find { |internal,_| internal =~ path }
         path.sub(*mapping)
-      elsif mapping = env['HTTP_X_ACCEL_MAPPING']
+      elsif mapping = x_accel_mapping(env)
+        # Safe to use header: explicit config + no app mappings
         internal, external = mapping.split('=', 2).map{ |p| p.strip }
         path.sub(/^#{internal}/i, external)
       end

lib/rack/utils.rb

@@ -64,6 +64,7 @@ class << self
       attr_accessor :param_depth_limit
       attr_accessor :multipart_total_part_limit
       attr_accessor :multipart_file_limit
+      attr_accessor :buffered_upload_bytesize_limit # CVE-2025-61771
 
       # multipart_part_limit is the original name of multipart_file_limit, but
       # the limit only counts parts with filenames.
@@ -89,6 +90,28 @@ class << self
     # many can lead to excessive memory use and parsing time.
     self.multipart_total_part_limit = (ENV['RACK_MULTIPART_TOTAL_PART_LIMIT'] || 4096).to_i
 
+    # This variable sets the maximum total size of all parts and headers
+    # of a multipart request. Parts with filenames are written to tempfiles
+    # and do not count. Defaults to 16 MB.
+    self.buffered_upload_bytesize_limit = (ENV['RACK_MULTIPART_BUFFERED_UPLOAD_BYTESIZE_LIMIT'] || 16 * 1024 * 1024).to_i
+
+    def check_query_string(qs, sep)
+      if qs
+        if qs.bytesize > Rack::Utils.bytesize_limit
+          raise QueryLimitError, "total query size exceeds limit (#{Rack::Utils.bytesize_limit})"
+        end
+
+        if (param_count = qs.count(sep.is_a?(String) ? sep : '&')) >= Rack::Utils.params_limit
+          raise QueryLimitError, "total number of query parameters (#{param_count+1}) exceeds limit (#{Rack::Utils.params_limit})"
+        end
+
+        qs
+      else
+        ''
+      end
+    end
+    module_function :check_query_string
+
     # Stolen from Mongrel, with some small modifications:
     # Parses a query string by breaking it up at the '&'
     # and ';' characters.  You can also use this to parse
@@ -99,7 +122,7 @@ def parse_query(qs, d = nil, &unescaper)
 
       params = KeySpaceConstrainedParams.new
 
-      (qs || '').split(d ? /[#{d}] */n : DEFAULT_SEP).each do |p|
+      check_query_string(ds, d).split(d ? /[#{d}] */n : DEFAULT_SEP).each do |p|
         next if p.empty?
         k, v = p.split('=', 2).map(&unescaper)
 
@@ -126,7 +149,7 @@ def parse_query(qs, d = nil, &unescaper)
     def parse_nested_query(qs, d = nil)
       params = KeySpaceConstrainedParams.new
 
-      (qs || '').split(d ? /[#{d}] */n : DEFAULT_SEP).each do |p|
+      check_query_string(ds, d).split(d ? /[#{d}] */n : DEFAULT_SEP).each do |p|
         k, v = p.split('=', 2).map { |s| unescape(s) }
 
         normalize_params(params, k, v)