Class: Rack::ShowExceptions

Inherits:
Object
  • Object
show all
Defined in:
lib/rack/show_exceptions.rb

Overview

Rack::ShowExceptions catches all exceptions raised from the app it wraps. It shows a useful backtrace with the sourcefile and clickable context, the whole Rack environment and the request data.

Be careful when you use this on public-facing sites as it could reveal information helpful to attackers.

Constant Summary collapse

CONTEXT =
7
TEMPLATE =

adapted from Django <www.djangoproject.com> Copyright © Django Software Foundation and individual contributors. Used under the modified BSD license: www.xfree86.org/3.3.6/COPYRIGHT2.html#5

ERB.new(<<-'HTML'.gsub(/^      /, ''))
  <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
  <html lang="en">
  <head>
    <meta http-equiv="content-type" content="text/html; charset=utf-8" />
    <meta name="robots" content="NONE,NOARCHIVE" />
    <title><%=h exception.class %> at <%=h path %></title>
    <style type="text/css">
      html * { padding:0; margin:0; }
      body * { padding:10px 20px; }
      body * * { padding:0; }
      body { font:small sans-serif; }
      body>div { border-bottom:1px solid #ddd; }
      h1 { font-weight:normal; }
      h2 { margin-bottom:.8em; }
      h2 span { font-size:80%; color:#666; font-weight:normal; }
      h3 { margin:1em 0 .5em 0; }
      h4 { margin:0 0 .5em 0; font-weight: normal; }
      table {
          border:1px solid #ccc; border-collapse: collapse; background:white; }
      tbody td, tbody th { vertical-align:top; padding:2px 3px; }
      thead th {
          padding:1px 6px 1px 3px; background:#fefefe; text-align:left;
          font-weight:normal; font-size:11px; border:1px solid #ddd; }
      tbody th { text-align:right; color:#666; padding-right:.5em; }
      table.vars { margin:5px 0 2px 40px; }
      table.vars td, table.req td { font-family:monospace; }
      table td.code { width:100%;}
      table td.code div { overflow:hidden; }
      table.source th { color:#666; }
      table.source td {
          font-family:monospace; white-space:pre; border-bottom:1px solid #eee; }
      ul.traceback { list-style-type:none; }
      ul.traceback li.frame { margin-bottom:1em; }
      div.context { margin: 10px 0; }
      div.context ol {
          padding-left:30px; margin:0 10px; list-style-position: inside; }
      div.context ol li {
          font-family:monospace; white-space:pre; color:#666; cursor:pointer; }
      div.context ol.context-line li { color:black; background-color:#ccc; }
      div.context ol.context-line li span { float: right; }
      div.commands { margin-left: 40px; }
      div.commands a { color:black; text-decoration:none; }
      #summary { background: #ffc; }
      #summary h2 { font-family: monospace; font-weight: normal; color: #666; white-space: pre-wrap; }
      #summary ul#quicklinks { list-style-type: none; margin-bottom: 2em; }
      #summary ul#quicklinks li { float: left; padding: 0 1em; }
      #summary ul#quicklinks>li+li { border-left: 1px #666 solid; }
      #explanation { background:#eee; }
      #template, #template-not-exist { background:#f6f6f6; }
      #template-not-exist ul { margin: 0 0 0 20px; }
      #traceback { background:#eee; }
      #requestinfo { background:#f6f6f6; padding-left:120px; }
      #summary table { border:none; background:transparent; }
      #requestinfo h2, #requestinfo h3 { position:relative; margin-left:-100px; }
      #requestinfo h3 { margin-bottom:-1em; }
      .error { background: #ffc; }
      .specific { color:#cc3300; font-weight:bold; }
    </style>
    <script type="text/javascript">
    //<!--
      function getElementsByClassName(oElm, strTagName, strClassName){
          // Written by Jonathan Snook, http://www.snook.ca/jon;
          // Add-ons by Robert Nyman, http://www.robertnyman.com
          var arrElements = (strTagName == "*" && document.all)? document.all :
          oElm.getElementsByTagName(strTagName);
          var arrReturnElements = new Array();
          strClassName = strClassName.replace(/\-/g, "\\-");
          var oRegExp = new RegExp("(^|\\s)" + strClassName + "(\\s|$$)");
          var oElement;
          for(var i=0; i<arrElements.length; i++){
              oElement = arrElements[i];
              if(oRegExp.test(oElement.className)){
                  arrReturnElements.push(oElement);
              }
          }
          return (arrReturnElements)
      }
      function hideAll(elems) {
        for (var e = 0; e < elems.length; e++) {
          elems[e].style.display = 'none';
        }
      }
      window.onload = function() {
        hideAll(getElementsByClassName(document, 'table', 'vars'));
        hideAll(getElementsByClassName(document, 'ol', 'pre-context'));
        hideAll(getElementsByClassName(document, 'ol', 'post-context'));
      }
      function toggle() {
        for (var i = 0; i < arguments.length; i++) {
          var e = document.getElementById(arguments[i]);
          if (e) {
            e.style.display = e.style.display == 'none' ? 'block' : 'none';
          }
        }
        return false;
      }
      function varToggle(link, id) {
        toggle('v' + id);
        var s = link.getElementsByTagName('span')[0];
        var uarr = String.fromCharCode(0x25b6);
        var darr = String.fromCharCode(0x25bc);
        s.innerHTML = s.innerHTML == uarr ? darr : uarr;
        return false;
      }
      //-->
    </script>
  </head>
  <body>

  <div id="summary">
    <h1><%=h exception.class %> at <%=h path %></h1>
  <% if exception.respond_to?(:detailed_message) %>
    <h2><%=h exception.detailed_message(highlight: false) %></h2>
  <% else %>
    <h2><%=h exception.message %></h2>
  <% end %>
    <table><tr>
      <th>Ruby</th>
      <td>
  <% if first = frames.first %>
        <code><%=h first.filename %></code>: in <code><%=h first.function %></code>, line <%=h frames.first.lineno %>
  <% else %>
        unknown location
  <% end %>
      </td>
    </tr><tr>
      <th>Web</th>
      <td><code><%=h req.request_method %> <%=h(req.host + path)%></code></td>
    </tr></table>

    <h3>Jump to:</h3>
    <ul id="quicklinks">
      <li><a href="#get-info">GET</a></li>
      <li><a href="#post-info">POST</a></li>
      <li><a href="#cookie-info">Cookies</a></li>
      <li><a href="#env-info">ENV</a></li>
    </ul>
  </div>

  <div id="traceback">
    <h2>Traceback <span>(innermost first)</span></h2>
    <ul class="traceback">
  <% frames.each { |frame| %>
        <li class="frame">
          <code><%=h frame.filename %></code>: in <code><%=h frame.function %></code>

            <% if frame.context_line %>
            <div class="context" id="c<%=h frame.object_id %>">
                <% if frame.pre_context %>
                <ol start="<%=h frame.pre_context_lineno+1 %>" class="pre-context" id="pre<%=h frame.object_id %>">
                  <% frame.pre_context.each { |line| %>
                  <li onclick="toggle('pre<%=h frame.object_id %>', 'post<%=h frame.object_id %>')"><%=h line %></li>
                  <% } %>
                </ol>
                <% end %>

              <ol start="<%=h frame.lineno %>" class="context-line">
                <li onclick="toggle('pre<%=h frame.object_id %>', 'post<%=h frame.object_id %>')"><%=h frame.context_line %><span>...</span></li></ol>

                <% if frame.post_context %>
                <ol start='<%=h frame.lineno+1 %>' class="post-context" id="post<%=h frame.object_id %>">
                  <% frame.post_context.each { |line| %>
                  <li onclick="toggle('pre<%=h frame.object_id %>', 'post<%=h frame.object_id %>')"><%=h line %></li>
                  <% } %>
                </ol>
                <% end %>
            </div>
            <% end %>
        </li>
  <% } %>
    </ul>
  </div>

  <div id="requestinfo">
    <h2>Request information</h2>

    <h3 id="get-info">GET</h3>
    <% if req.GET and not req.GET.empty? %>
      <table class="req">
        <thead>
          <tr>
            <th>Variable</th>
            <th>Value</th>
          </tr>
        </thead>
        <tbody>
            <% req.GET.sort_by { |k, v| k.to_s }.each { |key, val| %>
            <tr>
              <td><%=h key %></td>
              <td class="code"><div><%=h val.inspect %></div></td>
            </tr>
            <% } %>
        </tbody>
      </table>
    <% else %>
      <p>No GET data.</p>
    <% end %>

    <h3 id="post-info">POST</h3>
    <% if ((req.POST and not req.POST.empty?) rescue (no_post_data = "Invalid POST data"; nil)) %>
      <table class="req">
        <thead>
          <tr>
            <th>Variable</th>
            <th>Value</th>
          </tr>
        </thead>
        <tbody>
            <% req.POST.sort_by { |k, v| k.to_s }.each { |key, val| %>
            <tr>
              <td><%=h key %></td>
              <td class="code"><div><%=h val.inspect %></div></td>
            </tr>
            <% } %>
        </tbody>
      </table>
    <% else %>
      <p><%= no_post_data || "No POST data" %>.</p>
    <% end %>


    <h3 id="cookie-info">COOKIES</h3>
    <% unless req.cookies.empty? %>
      <table class="req">
        <thead>
          <tr>
            <th>Variable</th>
            <th>Value</th>
          </tr>
        </thead>
        <tbody>
          <% req.cookies.each { |key, val| %>
            <tr>
              <td><%=h key %></td>
              <td class="code"><div><%=h val.inspect %></div></td>
            </tr>
          <% } %>
        </tbody>
      </table>
    <% else %>
      <p>No cookie data.</p>
    <% end %>

    <h3 id="env-info">Rack ENV</h3>
      <table class="req">
        <thead>
          <tr>
            <th>Variable</th>
            <th>Value</th>
          </tr>
        </thead>
        <tbody>
            <% env.sort_by { |k, v| k.to_s }.each { |key, val| %>
            <tr>
              <td><%=h key %></td>
              <td class="code"><div><%=h val.inspect %></div></td>
            </tr>
            <% } %>
        </tbody>
      </table>

  </div>

  <div id="explanation">
    <p>
      You're seeing this error because you use <code>Rack::ShowExceptions</code>.
    </p>
  </div>

  </body>
  </html>
HTML

Instance Method Summary collapse

Constructor Details

#initialize(app) ⇒ ShowExceptions

Returns a new instance of ShowExceptions.


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# File 'lib/rack/show_exceptions.rb', line 22

def initialize(app)
  @app = app
end

Instance Method Details

#call(env) ⇒ Object


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# File 'lib/rack/show_exceptions.rb', line 26

def call(env)
  @app.call(env)
rescue StandardError, LoadError, SyntaxError => e
  exception_string = dump_exception(e)

  env[RACK_ERRORS].puts(exception_string)
  env[RACK_ERRORS].flush

  if accepts_html?(env)
    content_type = "text/html"
    body = pretty(env, e)
  else
    content_type = "text/plain"
    body = exception_string
  end

  [
    500,
    {
      CONTENT_TYPE => content_type,
      CONTENT_LENGTH => body.bytesize.to_s,
    },
    [body],
  ]
end

#dump_exception(exception) ⇒ Object


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# File 'lib/rack/show_exceptions.rb', line 61

def dump_exception(exception)
  if exception.respond_to?(:detailed_message)
    message = exception.detailed_message(highlight: false)
  else
    message = exception.message
  end
  string = "#{exception.class}: #{message}\n".dup
  string << exception.backtrace.map { |l| "\t#{l}" }.join("\n")
  string
end

#h(obj) ⇒ Object

:nodoc:


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# File 'lib/rack/show_exceptions.rb', line 112

def h(obj)                  # :nodoc:
  case obj
  when String
    Utils.escape_html(obj)
  else
    Utils.escape_html(obj.inspect)
  end
end

#prefers_plaintext?(env) ⇒ Boolean

Returns:

  • (Boolean)

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# File 'lib/rack/show_exceptions.rb', line 52

def prefers_plaintext?(env)
  !accepts_html?(env)
end

#pretty(env, exception) ⇒ Object


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# File 'lib/rack/show_exceptions.rb', line 72

def pretty(env, exception)
  req = Rack::Request.new(env)

  # This double assignment is to prevent an "unused variable" warning.
  # Yes, it is dumb, but I don't like Ruby yelling at me.
  path = path = (req.script_name + req.path_info).squeeze("/")

  # This double assignment is to prevent an "unused variable" warning.
  # Yes, it is dumb, but I don't like Ruby yelling at me.
  frames = frames = exception.backtrace.map { |line|
    frame = OpenStruct.new
    if line =~ /(.*?):(\d+)(:in `(.*)')?/
      frame.filename = $1
      frame.lineno = $2.to_i
      frame.function = $4

      begin
        lineno = frame.lineno - 1
        lines = ::File.readlines(frame.filename)
        frame.pre_context_lineno = [lineno - CONTEXT, 0].max
        frame.pre_context = lines[frame.pre_context_lineno...lineno]
        frame.context_line = lines[lineno].chomp
        frame.post_context_lineno = [lineno + CONTEXT, lines.size].min
        frame.post_context = lines[lineno + 1..frame.post_context_lineno]
      rescue
      end

      frame
    else
      nil
    end
  }.compact

  template.result(binding)
end

#templateObject


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# File 'lib/rack/show_exceptions.rb', line 108

def template
  TEMPLATE
end