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<h1>Source code for django.core.signing</h1><div class="highlight"><pre>
<span></span><span class="sd">"""</span>
<span class="sd">Functions for creating and restoring url-safe signed JSON objects.</span>
<span class="sd">The format used looks like this:</span>
<span class="sd">>>> signing.dumps("hello")</span>
<span class="sd">'ImhlbGxvIg:1QaUZC:YIye-ze3TTx7gtSv422nZA4sgmk'</span>
<span class="sd">There are two components here, separated by a ':'. The first component is a</span>
<span class="sd">URLsafe base64 encoded JSON of the object passed to dumps(). The second</span>
<span class="sd">component is a base64 encoded hmac/SHA1 hash of "$first_component:$secret"</span>
<span class="sd">signing.loads(s) checks the signature and returns the deserialized object.</span>
<span class="sd">If the signature fails, a BadSignature exception is raised.</span>
<span class="sd">>>> signing.loads("ImhlbGxvIg:1QaUZC:YIye-ze3TTx7gtSv422nZA4sgmk")</span>
<span class="sd">u'hello'</span>
<span class="sd">>>> signing.loads("ImhlbGxvIg:1QaUZC:YIye-ze3TTx7gtSv422nZA4sgmk-modified")</span>
<span class="sd">...</span>
<span class="sd">BadSignature: Signature failed: ImhlbGxvIg:1QaUZC:YIye-ze3TTx7gtSv422nZA4sgmk-modified</span>
<span class="sd">You can optionally compress the JSON prior to base64 encoding it to save</span>
<span class="sd">space, using the compress=True argument. This checks if compression actually</span>
<span class="sd">helps and only applies compression if the result is a shorter string:</span>
<span class="sd">>>> signing.dumps(range(1, 20), compress=True)</span>
<span class="sd">'.eJwFwcERACAIwLCF-rCiILN47r-GyZVJsNgkxaFxoDgxcOHGxMKD_T7vhAml:1QaUaL:BA0thEZrp4FQVXIXuOvYJtLJSrQ'</span>
<span class="sd">The fact that the string is compressed is signalled by the prefixed '.' at the</span>
<span class="sd">start of the base64 JSON.</span>
<span class="sd">There are 65 url-safe characters: the 64 used by url-safe base64 and the ':'.</span>
<span class="sd">These functions make use of all of them.</span>
<span class="sd">"""</span>
<span class="kn">from</span> <span class="nn">__future__</span> <span class="k">import</span> <span class="n">unicode_literals</span>
<span class="kn">import</span> <span class="nn">base64</span>
<span class="kn">import</span> <span class="nn">datetime</span>
<span class="kn">import</span> <span class="nn">json</span>
<span class="kn">import</span> <span class="nn">time</span>
<span class="kn">import</span> <span class="nn">zlib</span>
<span class="kn">from</span> <span class="nn">django.conf</span> <span class="k">import</span> <span class="n">settings</span>
<span class="kn">from</span> <span class="nn">django.utils</span> <span class="k">import</span> <span class="n">baseconv</span>
<span class="kn">from</span> <span class="nn">django.utils.crypto</span> <span class="k">import</span> <span class="n">constant_time_compare</span><span class="p">,</span> <span class="n">salted_hmac</span>
<span class="kn">from</span> <span class="nn">django.utils.encoding</span> <span class="k">import</span> <span class="n">force_bytes</span><span class="p">,</span> <span class="n">force_str</span><span class="p">,</span> <span class="n">force_text</span>
<span class="kn">from</span> <span class="nn">django.utils.module_loading</span> <span class="k">import</span> <span class="n">import_string</span>
<span class="k">class</span> <span class="nc">BadSignature</span><span class="p">(</span><span class="ne">Exception</span><span class="p">):</span>
<span class="sd">"""</span>
<span class="sd"> Signature does not match</span>
<span class="sd"> """</span>
<span class="k">pass</span>
<span class="k">class</span> <span class="nc">SignatureExpired</span><span class="p">(</span><span class="n">BadSignature</span><span class="p">):</span>
<span class="sd">"""</span>
<span class="sd"> Signature timestamp is older than required max_age</span>
<span class="sd"> """</span>
<span class="k">pass</span>
<span class="k">def</span> <span class="nf">b64_encode</span><span class="p">(</span><span class="n">s</span><span class="p">):</span>
<span class="k">return</span> <span class="n">base64</span><span class="o">.</span><span class="n">urlsafe_b64encode</span><span class="p">(</span><span class="n">s</span><span class="p">)</span><span class="o">.</span><span class="n">strip</span><span class="p">(</span><span class="n">b</span><span class="s1">'='</span><span class="p">)</span>
<span class="k">def</span> <span class="nf">b64_decode</span><span class="p">(</span><span class="n">s</span><span class="p">):</span>
<span class="n">pad</span> <span class="o">=</span> <span class="n">b</span><span class="s1">'='</span> <span class="o">*</span> <span class="p">(</span><span class="o">-</span><span class="nb">len</span><span class="p">(</span><span class="n">s</span><span class="p">)</span> <span class="o">%</span> <span class="mi">4</span><span class="p">)</span>
<span class="k">return</span> <span class="n">base64</span><span class="o">.</span><span class="n">urlsafe_b64decode</span><span class="p">(</span><span class="n">s</span> <span class="o">+</span> <span class="n">pad</span><span class="p">)</span>
<span class="k">def</span> <span class="nf">base64_hmac</span><span class="p">(</span><span class="n">salt</span><span class="p">,</span> <span class="n">value</span><span class="p">,</span> <span class="n">key</span><span class="p">):</span>
<span class="k">return</span> <span class="n">b64_encode</span><span class="p">(</span><span class="n">salted_hmac</span><span class="p">(</span><span class="n">salt</span><span class="p">,</span> <span class="n">value</span><span class="p">,</span> <span class="n">key</span><span class="p">)</span><span class="o">.</span><span class="n">digest</span><span class="p">())</span>
<span class="k">def</span> <span class="nf">get_cookie_signer</span><span class="p">(</span><span class="n">salt</span><span class="o">=</span><span class="s1">'django.core.signing.get_cookie_signer'</span><span class="p">):</span>
<span class="n">Signer</span> <span class="o">=</span> <span class="n">import_string</span><span class="p">(</span><span class="n">settings</span><span class="o">.</span><span class="n">SIGNING_BACKEND</span><span class="p">)</span>
<span class="n">key</span> <span class="o">=</span> <span class="n">force_bytes</span><span class="p">(</span><span class="n">settings</span><span class="o">.</span><span class="n">SECRET_KEY</span><span class="p">)</span>
<span class="k">return</span> <span class="n">Signer</span><span class="p">(</span><span class="n">b</span><span class="s1">'django.http.cookies'</span> <span class="o">+</span> <span class="n">key</span><span class="p">,</span> <span class="n">salt</span><span class="o">=</span><span class="n">salt</span><span class="p">)</span>
<span class="k">class</span> <span class="nc">JSONSerializer</span><span class="p">(</span><span class="nb">object</span><span class="p">):</span>
<span class="sd">"""</span>
<span class="sd"> Simple wrapper around json to be used in signing.dumps and</span>
<span class="sd"> signing.loads.</span>
<span class="sd"> """</span>
<span class="k">def</span> <span class="nf">dumps</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">obj</span><span class="p">):</span>
<span class="k">return</span> <span class="n">json</span><span class="o">.</span><span class="n">dumps</span><span class="p">(</span><span class="n">obj</span><span class="p">,</span> <span class="n">separators</span><span class="o">=</span><span class="p">(</span><span class="s1">','</span><span class="p">,</span> <span class="s1">':'</span><span class="p">))</span><span class="o">.</span><span class="n">encode</span><span class="p">(</span><span class="s1">'latin-1'</span><span class="p">)</span>
<span class="k">def</span> <span class="nf">loads</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">data</span><span class="p">):</span>
<span class="k">return</span> <span class="n">json</span><span class="o">.</span><span class="n">loads</span><span class="p">(</span><span class="n">data</span><span class="o">.</span><span class="n">decode</span><span class="p">(</span><span class="s1">'latin-1'</span><span class="p">))</span>
<div class="viewcode-block" id="dumps"><a class="viewcode-back" href="../../../topics/signing.html#django.core.signing.dumps">[docs]</a><span class="k">def</span> <span class="nf">dumps</span><span class="p">(</span><span class="n">obj</span><span class="p">,</span> <span class="n">key</span><span class="o">=</span><span class="kc">None</span><span class="p">,</span> <span class="n">salt</span><span class="o">=</span><span class="s1">'django.core.signing'</span><span class="p">,</span> <span class="n">serializer</span><span class="o">=</span><span class="n">JSONSerializer</span><span class="p">,</span> <span class="n">compress</span><span class="o">=</span><span class="kc">False</span><span class="p">):</span>
<span class="sd">"""</span>
<span class="sd"> Returns URL-safe, sha1 signed base64 compressed JSON string. If key is</span>
<span class="sd"> None, settings.SECRET_KEY is used instead.</span>
<span class="sd"> If compress is True (not the default) checks if compressing using zlib can</span>
<span class="sd"> save some space. Prepends a '.' to signify compression. This is included</span>
<span class="sd"> in the signature, to protect against zip bombs.</span>
<span class="sd"> Salt can be used to namespace the hash, so that a signed string is</span>
<span class="sd"> only valid for a given namespace. Leaving this at the default</span>
<span class="sd"> value or re-using a salt value across different parts of your</span>
<span class="sd"> application without good cause is a security risk.</span>
<span class="sd"> The serializer is expected to return a bytestring.</span>
<span class="sd"> """</span>
<span class="n">data</span> <span class="o">=</span> <span class="n">serializer</span><span class="p">()</span><span class="o">.</span><span class="n">dumps</span><span class="p">(</span><span class="n">obj</span><span class="p">)</span>
<span class="c1"># Flag for if it's been compressed or not</span>
<span class="n">is_compressed</span> <span class="o">=</span> <span class="kc">False</span>
<span class="k">if</span> <span class="n">compress</span><span class="p">:</span>
<span class="c1"># Avoid zlib dependency unless compress is being used</span>
<span class="n">compressed</span> <span class="o">=</span> <span class="n">zlib</span><span class="o">.</span><span class="n">compress</span><span class="p">(</span><span class="n">data</span><span class="p">)</span>
<span class="k">if</span> <span class="nb">len</span><span class="p">(</span><span class="n">compressed</span><span class="p">)</span> <span class="o"><</span> <span class="p">(</span><span class="nb">len</span><span class="p">(</span><span class="n">data</span><span class="p">)</span> <span class="o">-</span> <span class="mi">1</span><span class="p">):</span>
<span class="n">data</span> <span class="o">=</span> <span class="n">compressed</span>
<span class="n">is_compressed</span> <span class="o">=</span> <span class="kc">True</span>
<span class="n">base64d</span> <span class="o">=</span> <span class="n">b64_encode</span><span class="p">(</span><span class="n">data</span><span class="p">)</span>
<span class="k">if</span> <span class="n">is_compressed</span><span class="p">:</span>
<span class="n">base64d</span> <span class="o">=</span> <span class="n">b</span><span class="s1">'.'</span> <span class="o">+</span> <span class="n">base64d</span>
<span class="k">return</span> <span class="n">TimestampSigner</span><span class="p">(</span><span class="n">key</span><span class="p">,</span> <span class="n">salt</span><span class="o">=</span><span class="n">salt</span><span class="p">)</span><span class="o">.</span><span class="n">sign</span><span class="p">(</span><span class="n">base64d</span><span class="p">)</span></div>
<div class="viewcode-block" id="loads"><a class="viewcode-back" href="../../../topics/signing.html#django.core.signing.loads">[docs]</a><span class="k">def</span> <span class="nf">loads</span><span class="p">(</span><span class="n">s</span><span class="p">,</span> <span class="n">key</span><span class="o">=</span><span class="kc">None</span><span class="p">,</span> <span class="n">salt</span><span class="o">=</span><span class="s1">'django.core.signing'</span><span class="p">,</span> <span class="n">serializer</span><span class="o">=</span><span class="n">JSONSerializer</span><span class="p">,</span> <span class="n">max_age</span><span class="o">=</span><span class="kc">None</span><span class="p">):</span>
<span class="sd">"""</span>
<span class="sd"> Reverse of dumps(), raises BadSignature if signature fails.</span>
<span class="sd"> The serializer is expected to accept a bytestring.</span>
<span class="sd"> """</span>
<span class="c1"># TimestampSigner.unsign always returns unicode but base64 and zlib</span>
<span class="c1"># compression operate on bytes.</span>
<span class="n">base64d</span> <span class="o">=</span> <span class="n">force_bytes</span><span class="p">(</span><span class="n">TimestampSigner</span><span class="p">(</span><span class="n">key</span><span class="p">,</span> <span class="n">salt</span><span class="o">=</span><span class="n">salt</span><span class="p">)</span><span class="o">.</span><span class="n">unsign</span><span class="p">(</span><span class="n">s</span><span class="p">,</span> <span class="n">max_age</span><span class="o">=</span><span class="n">max_age</span><span class="p">))</span>
<span class="n">decompress</span> <span class="o">=</span> <span class="kc">False</span>
<span class="k">if</span> <span class="n">base64d</span><span class="p">[:</span><span class="mi">1</span><span class="p">]</span> <span class="o">==</span> <span class="n">b</span><span class="s1">'.'</span><span class="p">:</span>
<span class="c1"># It's compressed; uncompress it first</span>
<span class="n">base64d</span> <span class="o">=</span> <span class="n">base64d</span><span class="p">[</span><span class="mi">1</span><span class="p">:]</span>
<span class="n">decompress</span> <span class="o">=</span> <span class="kc">True</span>
<span class="n">data</span> <span class="o">=</span> <span class="n">b64_decode</span><span class="p">(</span><span class="n">base64d</span><span class="p">)</span>
<span class="k">if</span> <span class="n">decompress</span><span class="p">:</span>
<span class="n">data</span> <span class="o">=</span> <span class="n">zlib</span><span class="o">.</span><span class="n">decompress</span><span class="p">(</span><span class="n">data</span><span class="p">)</span>
<span class="k">return</span> <span class="n">serializer</span><span class="p">()</span><span class="o">.</span><span class="n">loads</span><span class="p">(</span><span class="n">data</span><span class="p">)</span></div>
<div class="viewcode-block" id="Signer"><a class="viewcode-back" href="../../../topics/signing.html#django.core.signing.Signer">[docs]</a><span class="k">class</span> <span class="nc">Signer</span><span class="p">(</span><span class="nb">object</span><span class="p">):</span>
<span class="k">def</span> <span class="nf">__init__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">key</span><span class="o">=</span><span class="kc">None</span><span class="p">,</span> <span class="n">sep</span><span class="o">=</span><span class="s1">':'</span><span class="p">,</span> <span class="n">salt</span><span class="o">=</span><span class="kc">None</span><span class="p">):</span>
<span class="c1"># Use of native strings in all versions of Python</span>
<span class="bp">self</span><span class="o">.</span><span class="n">sep</span> <span class="o">=</span> <span class="n">force_str</span><span class="p">(</span><span class="n">sep</span><span class="p">)</span>
<span class="bp">self</span><span class="o">.</span><span class="n">key</span> <span class="o">=</span> <span class="n">key</span> <span class="ow">or</span> <span class="n">settings</span><span class="o">.</span><span class="n">SECRET_KEY</span>
<span class="bp">self</span><span class="o">.</span><span class="n">salt</span> <span class="o">=</span> <span class="n">force_str</span><span class="p">(</span><span class="n">salt</span> <span class="ow">or</span>
<span class="s1">'</span><span class="si">%s</span><span class="s1">.</span><span class="si">%s</span><span class="s1">'</span> <span class="o">%</span> <span class="p">(</span><span class="bp">self</span><span class="o">.</span><span class="n">__class__</span><span class="o">.</span><span class="n">__module__</span><span class="p">,</span> <span class="bp">self</span><span class="o">.</span><span class="n">__class__</span><span class="o">.</span><span class="n">__name__</span><span class="p">))</span>
<span class="k">def</span> <span class="nf">signature</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">value</span><span class="p">):</span>
<span class="n">signature</span> <span class="o">=</span> <span class="n">base64_hmac</span><span class="p">(</span><span class="bp">self</span><span class="o">.</span><span class="n">salt</span> <span class="o">+</span> <span class="s1">'signer'</span><span class="p">,</span> <span class="n">value</span><span class="p">,</span> <span class="bp">self</span><span class="o">.</span><span class="n">key</span><span class="p">)</span>
<span class="c1"># Convert the signature from bytes to str only on Python 3</span>
<span class="k">return</span> <span class="n">force_str</span><span class="p">(</span><span class="n">signature</span><span class="p">)</span>
<span class="k">def</span> <span class="nf">sign</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">value</span><span class="p">):</span>
<span class="n">value</span> <span class="o">=</span> <span class="n">force_str</span><span class="p">(</span><span class="n">value</span><span class="p">)</span>
<span class="k">return</span> <span class="nb">str</span><span class="p">(</span><span class="s1">'</span><span class="si">%s%s%s</span><span class="s1">'</span><span class="p">)</span> <span class="o">%</span> <span class="p">(</span><span class="n">value</span><span class="p">,</span> <span class="bp">self</span><span class="o">.</span><span class="n">sep</span><span class="p">,</span> <span class="bp">self</span><span class="o">.</span><span class="n">signature</span><span class="p">(</span><span class="n">value</span><span class="p">))</span>
<span class="k">def</span> <span class="nf">unsign</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">signed_value</span><span class="p">):</span>
<span class="n">signed_value</span> <span class="o">=</span> <span class="n">force_str</span><span class="p">(</span><span class="n">signed_value</span><span class="p">)</span>
<span class="k">if</span> <span class="bp">self</span><span class="o">.</span><span class="n">sep</span> <span class="ow">not</span> <span class="ow">in</span> <span class="n">signed_value</span><span class="p">:</span>
<span class="k">raise</span> <span class="n">BadSignature</span><span class="p">(</span><span class="s1">'No "</span><span class="si">%s</span><span class="s1">" found in value'</span> <span class="o">%</span> <span class="bp">self</span><span class="o">.</span><span class="n">sep</span><span class="p">)</span>
<span class="n">value</span><span class="p">,</span> <span class="n">sig</span> <span class="o">=</span> <span class="n">signed_value</span><span class="o">.</span><span class="n">rsplit</span><span class="p">(</span><span class="bp">self</span><span class="o">.</span><span class="n">sep</span><span class="p">,</span> <span class="mi">1</span><span class="p">)</span>
<span class="k">if</span> <span class="n">constant_time_compare</span><span class="p">(</span><span class="n">sig</span><span class="p">,</span> <span class="bp">self</span><span class="o">.</span><span class="n">signature</span><span class="p">(</span><span class="n">value</span><span class="p">)):</span>
<span class="k">return</span> <span class="n">force_text</span><span class="p">(</span><span class="n">value</span><span class="p">)</span>
<span class="k">raise</span> <span class="n">BadSignature</span><span class="p">(</span><span class="s1">'Signature "</span><span class="si">%s</span><span class="s1">" does not match'</span> <span class="o">%</span> <span class="n">sig</span><span class="p">)</span></div>
<div class="viewcode-block" id="TimestampSigner"><a class="viewcode-back" href="../../../topics/signing.html#django.core.signing.TimestampSigner">[docs]</a><span class="k">class</span> <span class="nc">TimestampSigner</span><span class="p">(</span><span class="n">Signer</span><span class="p">):</span>
<span class="k">def</span> <span class="nf">timestamp</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="k">return</span> <span class="n">baseconv</span><span class="o">.</span><span class="n">base62</span><span class="o">.</span><span class="n">encode</span><span class="p">(</span><span class="nb">int</span><span class="p">(</span><span class="n">time</span><span class="o">.</span><span class="n">time</span><span class="p">()))</span>
<div class="viewcode-block" id="TimestampSigner.sign"><a class="viewcode-back" href="../../../topics/signing.html#django.core.signing.TimestampSigner.sign">[docs]</a> <span class="k">def</span> <span class="nf">sign</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">value</span><span class="p">):</span>
<span class="n">value</span> <span class="o">=</span> <span class="n">force_str</span><span class="p">(</span><span class="n">value</span><span class="p">)</span>
<span class="n">value</span> <span class="o">=</span> <span class="nb">str</span><span class="p">(</span><span class="s1">'</span><span class="si">%s%s%s</span><span class="s1">'</span><span class="p">)</span> <span class="o">%</span> <span class="p">(</span><span class="n">value</span><span class="p">,</span> <span class="bp">self</span><span class="o">.</span><span class="n">sep</span><span class="p">,</span> <span class="bp">self</span><span class="o">.</span><span class="n">timestamp</span><span class="p">())</span>
<span class="k">return</span> <span class="nb">super</span><span class="p">(</span><span class="n">TimestampSigner</span><span class="p">,</span> <span class="bp">self</span><span class="p">)</span><span class="o">.</span><span class="n">sign</span><span class="p">(</span><span class="n">value</span><span class="p">)</span></div>
<div class="viewcode-block" id="TimestampSigner.unsign"><a class="viewcode-back" href="../../../topics/signing.html#django.core.signing.TimestampSigner.unsign">[docs]</a> <span class="k">def</span> <span class="nf">unsign</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">value</span><span class="p">,</span> <span class="n">max_age</span><span class="o">=</span><span class="kc">None</span><span class="p">):</span>
<span class="sd">"""</span>
<span class="sd"> Retrieve original value and check it wasn't signed more</span>
<span class="sd"> than max_age seconds ago.</span>
<span class="sd"> """</span>
<span class="n">result</span> <span class="o">=</span> <span class="nb">super</span><span class="p">(</span><span class="n">TimestampSigner</span><span class="p">,</span> <span class="bp">self</span><span class="p">)</span><span class="o">.</span><span class="n">unsign</span><span class="p">(</span><span class="n">value</span><span class="p">)</span>
<span class="n">value</span><span class="p">,</span> <span class="n">timestamp</span> <span class="o">=</span> <span class="n">result</span><span class="o">.</span><span class="n">rsplit</span><span class="p">(</span><span class="bp">self</span><span class="o">.</span><span class="n">sep</span><span class="p">,</span> <span class="mi">1</span><span class="p">)</span>
<span class="n">timestamp</span> <span class="o">=</span> <span class="n">baseconv</span><span class="o">.</span><span class="n">base62</span><span class="o">.</span><span class="n">decode</span><span class="p">(</span><span class="n">timestamp</span><span class="p">)</span>
<span class="k">if</span> <span class="n">max_age</span> <span class="ow">is</span> <span class="ow">not</span> <span class="kc">None</span><span class="p">:</span>
<span class="k">if</span> <span class="nb">isinstance</span><span class="p">(</span><span class="n">max_age</span><span class="p">,</span> <span class="n">datetime</span><span class="o">.</span><span class="n">timedelta</span><span class="p">):</span>
<span class="n">max_age</span> <span class="o">=</span> <span class="n">max_age</span><span class="o">.</span><span class="n">total_seconds</span><span class="p">()</span>
<span class="c1"># Check timestamp is not older than max_age</span>
<span class="n">age</span> <span class="o">=</span> <span class="n">time</span><span class="o">.</span><span class="n">time</span><span class="p">()</span> <span class="o">-</span> <span class="n">timestamp</span>
<span class="k">if</span> <span class="n">age</span> <span class="o">></span> <span class="n">max_age</span><span class="p">:</span>
<span class="k">raise</span> <span class="n">SignatureExpired</span><span class="p">(</span>
<span class="s1">'Signature age </span><span class="si">%s</span><span class="s1"> > </span><span class="si">%s</span><span class="s1"> seconds'</span> <span class="o">%</span> <span class="p">(</span><span class="n">age</span><span class="p">,</span> <span class="n">max_age</span><span class="p">))</span>
<span class="k">return</span> <span class="n">value</span></div></div>
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