feat(middleware): extend cors with Prism and Middleware

lib/prism/middleware/cors.rb

@@ -0,0 +1,75 @@
+module Prism
+  module Middleware
+    # Handles the CORS preflight (OPTIONS with Access-Control-Request-Method)
+    # and stamps Access-Control-* response headers on matching simple/actual
+    # requests, per the whatwg fetch spec's precedence: no Origin header means
+    # this is not a cross-origin request at all, so it passes through untouched.
+    class Cors
+      def initialize(app, registry: Prism::Cors)
+        @app = app
+        @registry = registry
+      end
+
+      def call(env)
+        origin = env['HTTP_ORIGIN']
+        return @app.call(env) unless origin
+
+        match = @registry.resource_for(origin, format_agnostic_path(env['PATH_INFO']))
+        return @app.call(env) unless match
+        _rule, resource = match
+
+        if preflight?(env)
+          preflight_response(env, origin, resource)
+        else
+          status, headers, body = @app.call(env)
+          [status, apply_headers(headers, origin, resource), body]
+        end
+      end
+
+      private
+
+      # Cors resources are registered against logical route paths
+      # ('/posts'), but PATH_INFO still carries an optional trailing
+      # ".json"/".xml" format extension at this point in the stack (the
+      # router only strips it internally while matching) - without this,
+      # a resource registered for '/posts' would never match '/posts.json'.
+      def format_agnostic_path(path)
+        path.sub(%r{\.[^./]+\z}, '')
+      end
+
+      def preflight?(env)
+        env['REQUEST_METHOD'] == 'OPTIONS' && !env['HTTP_ACCESS_CONTROL_REQUEST_METHOD'].to_s.empty?
+      end
+
+      def preflight_response(env, origin, resource)
+        requested_method = env['HTTP_ACCESS_CONTROL_REQUEST_METHOD']
+        requested_headers = env['HTTP_ACCESS_CONTROL_REQUEST_HEADERS']
+
+        unless resource.allows_method?(requested_method) && resource.allows_headers?(requested_headers)
+          return [403, {}, ['CORS preflight rejected']]
+        end
+
+        headers = apply_headers({}, origin, resource)
+        headers['Access-Control-Allow-Methods'] = resource.methods.join(', ')
+        unless requested_headers.to_s.empty?
+          headers['Access-Control-Allow-Headers'] = requested_headers
+        end
+        headers['Access-Control-Max-Age'] = resource.max_age.to_s if resource.max_age
+        [204, headers, []]
+      end
+
+      def apply_headers(headers, origin, resource)
+        headers['Access-Control-Allow-Origin'] = origin
+        headers['Access-Control-Allow-Credentials'] = 'true' if resource.credentials
+        headers['Access-Control-Expose-Headers'] = resource.expose.join(', ') unless resource.expose.empty?
+        headers['Vary'] = append_vary(headers['Vary'], 'Origin')
+        headers
+      end
+
+      def append_vary(existing, value)
+        return value if existing.to_s.empty?
+        existing.split(',').map(&:strip).push(value).uniq.join(', ')
+      end
+    end
+  end
+end

lib/prism/middleware/rate_limiting.rb

@@ -0,0 +1,59 @@
+module Prism
+  module Middleware
+    # Evaluates Prism::RateLimiter rules on every request, in the same
+    # precedence order as Rack::Attack: safelist bypasses everything,
+    # then blocklist (403), then throttles (429 with Retry-After), then
+    # tracks (observation only, request still proceeds).
+    class RateLimiting
+      def initialize(app, limiter: Prism::RateLimiter)
+        @app = app
+        @limiter = limiter
+      end
+
+      def call(env)
+        request = Request.new(env)
+        return @app.call(env) if safelisted?(request)
+        return respond(403, 'Forbidden') if blocked?(request)
+
+        rule = throttled(request)
+        return respond(429, 'Too Many Requests', 'Retry-After' => rule.period.to_s) if rule
+
+        track(request)
+        @app.call(env)
+      end
+
+      private
+
+      def safelisted?(request)
+        @limiter.safelists.each_value.any? { |rule| rule.key_for(request) }
+      end
+
+      def blocked?(request)
+        @limiter.blocklists.each_value.any? { |rule| rule.key_for(request) }
+      end
+
+      def throttled(request)
+        @limiter.throttles.each_value do |rule|
+          key = rule.key_for(request)
+          next unless key
+          count = @limiter.store.count("#{rule.name}:#{key}", rule.period)
+          next unless count > rule.limit
+          @limiter.notify(:throttle, rule.name, request, key)
+          return rule
+        end
+        nil
+      end
+
+      def track(request)
+        @limiter.tracks.each_value do |rule|
+          value = rule.key_for(request)
+          @limiter.notify(:track, rule.name, request, value) if value
+        end
+      end
+
+      def respond(status, message, extra_headers = {})
+        [status, { 'Content-Type' => 'text/plain' }.merge(extra_headers), [message]]
+      end
+    end
+  end
+end

lib/prism/middleware/session.rb

@@ -3,18 +3,21 @@ module Prism
     class Session
       CookieName = 'prism.session'.freeze
 
-      def initialize(app, secret:, cookie_name: CookieName, **options)
+      def initialize(app, secret:, previous_secrets: [], cookie_name: CookieName, **options)
         @app = app
         @secret = secret
+        @previous_secrets = previous_secrets
         @cookie_name = cookie_name
         @options = options
       end
 
       def call(env)
         request = Request.new(env)
-        loaded = Prism::Session.decode(request.cookies[@cookie_name], @secret)
+        loaded = Prism::Session.decode(request.cookies[@cookie_name], @secret, previous_secrets: @previous_secrets)
         session = Params.from(loaded)
         env['prism.session'] = session
+        env['prism.secret'] = @secret
+        env['prism.previous_secrets'] = @previous_secrets
         original = session.dup
 
         status, headers, body = @app.call(env)

lib/prism/middleware/static.rb

@@ -20,7 +20,7 @@ module Prism
         file = resolve(env['PATH_INFO'])
         return @app.call(env) unless file
 
-        serve(file)
+        serve(file, head: method == 'HEAD', env: env)
       end
 
       private
@@ -35,10 +35,57 @@ module Prism
         candidate
       end
 
-      def serve(file)
-        body = File.binread(file)
+      def serve(file, head: false, env: {})
         type = ContentTypes.fetch(File.extname(file).downcase, 'application/octet-stream')
-        [200, { 'Content-Type' => type, 'Content-Length' => body.bytesize.to_s }, [body]]
+        etag, last_modified = StaticCache.weak_validators(File.size(file), File.mtime(file))
+        Static.respond_with_range(file, type, head: head, env: env, etag: etag, last_modified: last_modified)
+      end
+
+      # Shared by Middleware::Assets so both give identical conditional-GET
+      # (304) and Range/206/416 behavior instead of duplicating this
+      # branching twice. `etag`/`last_modified` are already-formatted header
+      # values chosen by the caller (Assets can offer a strong,
+      # fingerprint-derived ETag; plain Static files only get a cheap weak
+      # one - see StaticCache).
+      def self.respond_with_range(file, type, head: false, env: {}, etag: nil, last_modified: nil)
+        size = File.size(file)
+        headers = { 'Content-Type' => type, 'Accept-Ranges' => 'bytes' }
+        headers['ETag'] = etag if etag
+        headers['Last-Modified'] = last_modified if last_modified
+
+        if StaticCache.not_modified?(env, etag, last_modified)
+          return [304, cache_only_headers(etag, last_modified), []]
+        end
+
+        range = env['HTTP_RANGE']
+        range = nil unless StaticCache.range_applicable?(env, etag, last_modified)
+
+        parsed = HttpRange.parse(range, size)
+        if parsed == :unsatisfiable
+          headers['Content-Range'] = "bytes */#{size}"
+          return [416, headers, []]
+        end
+
+        if parsed.nil?
+          headers['Content-Length'] = size.to_s
+          body = head ? [] : [File.binread(file)]
+          return [200, headers, body]
+        end
+
+        headers['Content-Range'] = "bytes #{parsed.start}-#{parsed.finish}/#{size}"
+        headers['Content-Length'] = parsed.length.to_s
+        body = head ? [] : [HttpRange.read_slice(file, parsed)]
+        [206, headers, body]
+      end
+
+      # A 304 response must not carry entity headers like Content-Type/
+      # Content-Length (there is no body), only the cache validators the
+      # client can keep comparing against next time.
+      def self.cache_only_headers(etag, last_modified)
+        headers = {}
+        headers['ETag'] = etag if etag
+        headers['Last-Modified'] = last_modified if last_modified
+        headers
       end
     end
   end