Mercurial > pydertron
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| author | Atul Varma <varmaa@toolness.com> |
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| date | Sat, 12 Sep 2009 12:43:45 -0700 |
| parents | c2c369402a2e |
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| 21 | 1 <?xml version="1.0" encoding="utf-8" ?> |
| 2 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> | |
| 3 <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"> | |
| 4 <head> | |
| 5 <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> | |
| 6 <meta name="generator" content="Docutils 0.4: http://docutils.sourceforge.net/" /> | |
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7 <title>Pydertron</title> |
| 21 | 8 <link rel="stylesheet" href="docs.css" type="text/css" /> |
| 9 </head> | |
| 10 <body> | |
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11 <div class="document" id="pydertron"> |
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12 <h1 class="title">Pydertron</h1> |
| 25 | 13 <p>Pydertron is an experimental high-level wrapper for <a class="reference" href="http://code.google.com/p/pydermonkey">Pydermonkey</a> |
| 14 that provides convenient, secure object wrapping between JS and Python | |
| 21 | 15 space.</p> |
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16 <p>Note that Pydertron is just one example of a high-level interface |
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17 between Python and JavaScript: it assumes, for instance, that the JS |
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18 code it executes isn't trusted, which affects the nature of the |
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19 inter-language interaction.</p> |
| 25 | 20 <p>Pydertron is currently hosted at |
| 21 <a class="reference" href="http://hg.toolness.com/pydertron">http://hg.toolness.com/pydertron</a>. Please feel free to send any | |
| 22 questions or comments to <a class="reference" href="mailto:atul@mozilla.com">atul@mozilla.com</a>.</p> | |
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23 <div class="section"> |
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24 <h1><a id="the-basics" name="the-basics">The Basics</a></h1> |
| 21 | 25 <p>The <tt class="docutils literal"><span class="pre">JsSandbox</span></tt> class encapsulates a JavaScript runtime, context, global |
| 26 object, and a simple <a class="reference" href="http://wiki.commonjs.org/wiki/CommonJS/Modules/SecurableModules">SecurableModule</a> implementation that complies | |
| 27 with the <a class="reference" href="http://wiki.commonjs.org/wiki/CommonJS">CommonJS</a> standard. It also provides a high-level bridge between | |
| 28 Python and JavaScript so that you don't need to deal with any of the | |
| 29 low-level details of the Pydermonkey API.</p> | |
| 30 <p>For instance, here we'll create a <tt class="docutils literal"><span class="pre">JsSandbox</span></tt> whose module root | |
| 23 | 31 points to the <a class="reference" href="http://interoperablejs.googlecode.com/svn/trunk/compliance/monkeys/">monkeys</a> SecurableModule compliance test over HTTP:</p> |
| 21 | 32 <blockquote> |
| 33 <pre class="doctest-block"> | |
| 34 >>> url = ("http://interoperablejs.googlecode.com/svn/trunk/" | |
| 35 ... "compliance/monkeys/") | |
| 36 >>> sandbox = JsSandbox(HttpFileSystem(url)) | |
| 37 </pre> | |
| 38 </blockquote> | |
| 39 <p>This compliance test requires a global <tt class="docutils literal"><span class="pre">sys</span></tt> object that contains one | |
| 40 method, <tt class="docutils literal"><span class="pre">print()</span></tt>, that takes two arguments. First, we'll create the | |
| 41 <tt class="docutils literal"><span class="pre">print()</span></tt> function and prepare it for exposure to JS code:</p> | |
| 42 <blockquote> | |
| 43 <pre class="doctest-block"> | |
| 44 >>> @jsexposed | |
| 45 ... def jsprint(message, label): | |
| 46 ... print message, label | |
| 47 </pre> | |
| 48 </blockquote> | |
| 49 <p>Note the use of the <tt class="docutils literal"><span class="pre">@jsexposed</span></tt> decorator: all this does is set | |
| 50 the function's <tt class="docutils literal"><span class="pre">__jsexposed__</span></tt> attribute to <tt class="docutils literal"><span class="pre">True</span></tt>. This is | |
| 51 done for security purposes: only Python callables satisfying this | |
| 52 criteria will be exposed to JavaScript code, to ensure that | |
| 53 untrusted JS can't accidentally gain access to privileged Python | |
| 54 functionality.</p> | |
| 55 <p>Creating a JS object can be done like this:</p> | |
| 56 <blockquote> | |
| 57 <pre class="doctest-block"> | |
| 58 >>> system = sandbox.new_object() | |
| 59 </pre> | |
| 60 </blockquote> | |
| 61 <p>We can now access and set properties on this object via either | |
| 62 item or attribute lookup, just like in JavaScript. Because | |
| 63 <tt class="docutils literal"><span class="pre">print</span></tt> is a reserved word in Python, though, we'll use item | |
| 64 lookup to set the property here:</p> | |
| 65 <blockquote> | |
| 66 <pre class="doctest-block"> | |
| 67 >>> system['print'] = jsprint | |
| 68 </pre> | |
| 69 </blockquote> | |
| 70 <p>Now we tell the sandbox that we want the <tt class="docutils literal"><span class="pre">sys</span></tt> object to be a | |
| 71 global:</p> | |
| 72 <blockquote> | |
| 73 <pre class="doctest-block"> | |
| 74 >>> sandbox.set_globals(sys = system) | |
| 75 </pre> | |
| 76 </blockquote> | |
| 77 <p>And finally, we execute the compliance test by running a one-line | |
| 78 script that imports the 'program' module, like so:</p> | |
| 79 <blockquote> | |
| 80 <pre class="doctest-block"> | |
| 81 >>> sandbox.run_script("require('program');") | |
| 82 PASS monkeys permitted pass | |
| 83 DONE info | |
| 84 0 | |
| 85 </pre> | |
| 86 </blockquote> | |
| 87 <p>Note the <tt class="docutils literal"><span class="pre">0</span></tt> in the last line: this is the return value of | |
| 88 <tt class="docutils literal"><span class="pre">sandbox.run_script()</span></tt>, which returns <tt class="docutils literal"><span class="pre">0</span></tt> on success, and | |
| 89 <tt class="docutils literal"><span class="pre">-1</span></tt> if an exception was raised. For instance, the output of bad | |
| 90 code looks like this:</p> | |
| 91 <blockquote> | |
| 92 <pre class="doctest-block"> | |
| 93 >>> sandbox.run_script("(function foo() { bar(); })();", | |
| 94 ... stderr=sys.stdout) | |
| 95 Traceback (most recent call last): | |
| 96 File "<string>", line 1, in <module> | |
| 97 File "<string>", line 1, in foo | |
| 98 ReferenceError: bar is not defined | |
| 99 -1 | |
| 100 </pre> | |
| 101 </blockquote> | |
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102 <p>Note that the traceback displayed is actually referring to JavaScript |
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103 code: one of Pydertron's aims is to make debugging JS code as much |
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104 like debugging Python code as possible.</p> |
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105 </div> |
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106 <div class="section"> |
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107 <h1><a id="exceptions" name="exceptions">Exceptions</a></h1> |
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108 <p>Any exceptions raised by wrapped Python functions need to be of type |
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109 <tt class="docutils literal"><span class="pre">pydermonkey.error</span></tt> to be propagated into calling JavaScript code; |
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110 if they're not, then for security purposes, the entire JavaScript call |
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111 stack is unrolled.</p> |
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112 <p>For example, here's a function that's bound to fail:</p> |
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113 <blockquote> |
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114 <pre class="doctest-block"> |
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115 >>> @jsexposed |
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116 ... def fail(): |
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117 ... o() |
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118 >>> sandbox.root.fail = fail |
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119 </pre> |
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120 </blockquote> |
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121 <p>Now, even though the following JS code calls the function in a |
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122 try-catch block, the JS code doesn't catch anything and its execution |
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123 is simply halted:</p> |
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124 <blockquote> |
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125 <pre class="doctest-block"> |
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126 >>> sandbox.run_script("try { fail(); } catch (e) {}", |
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127 ... stderr=sys.stdout) #doctest: +ELLIPSIS |
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128 An internal error occurred. |
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129 Traceback (most recent call last): |
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130 ... |
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131 NameError: global name 'o' is not defined |
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132 -1 |
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133 </pre> |
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134 </blockquote> |
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135 <p>Note that a <tt class="docutils literal"><span class="pre">KeyboardInterrupt</span></tt> triggered while JS is executing will |
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136 have similar effect.</p> |
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137 </div> |
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138 </div> |
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139 <div class="footer"> |
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140 <hr class="footer" /> |
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141 <a class="reference" href="docs.txt">View document source</a>. |
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142 |
| 21 | 143 </div> |
| 144 </body> | |
| 145 </html> |