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  195.   <section id="module-crypt">

  196. <span id="crypt-function-to-check-unix-passwords"></span><h1><a class="reference internal" href="#module-crypt" title="crypt: The crypt() function used to check Unix passwords. (deprecated) (Unix)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">crypt</span></code></a> — Function to check Unix passwords<a class="headerlink" href="#module-crypt" title="Link to this heading">¶</a></h1>

  197. <p><strong>Source code:</strong> <a class="reference external" href="https://github.com/python/cpython/tree/3.12/Lib/crypt.py">Lib/crypt.py</a></p>

  198. <div class="deprecated-removed" id="index-0">

  199. <p><span class="versionmodified">Deprecated since version 3.11, will be removed in version 3.13: </span>The <a class="reference internal" href="#module-crypt" title="crypt: The crypt() function used to check Unix passwords. (deprecated) (Unix)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">crypt</span></code></a> module is deprecated

  200. (see <span class="target" id="index-1"></span><a class="pep reference external" href="https://peps.python.org/pep-0594/#crypt"><strong>PEP 594</strong></a> for details and alternatives).

  201. The <a class="reference internal" href="hashlib.html#module-hashlib" title="hashlib: Secure hash and message digest algorithms."><code class="xref py py-mod docutils literal notranslate"><span class="pre">hashlib</span></code></a> module is a potential replacement for certain use cases.

  202. The <a class="reference external" href="https://pypi.org/project/passlib/">passlib</a> package can replace all use cases of this module.</p>

  203. </div>

  204. <hr class="docutils" />

  205. <p>This module implements an interface to the <em class="manpage"><a class="manpage reference external" href="https://manpages.debian.org/crypt(3)">crypt(3)</a></em> routine, which is

  206. a one-way hash function based upon a modified DES algorithm; see the Unix man

  207. page for further details.  Possible uses include storing hashed passwords

  208. so you can check passwords without storing the actual password, or attempting

  209. to crack Unix passwords with a dictionary.</p>

  210. <p id="index-2">Notice that the behavior of this module depends on the actual implementation  of

  211. the <em class="manpage"><a class="manpage reference external" href="https://manpages.debian.org/crypt(3)">crypt(3)</a></em> routine in the running system.  Therefore, any

  212. extensions available on the current implementation will also  be available on

  213. this module.</p>

  214. <div class="availability docutils container">

  215. <p><a class="reference internal" href="intro.html#availability"><span class="std std-ref">Availability</span></a>: Unix, not VxWorks.</p>

  216. </div>

  217. <div class="availability docutils container">

  218. <p><a class="reference internal" href="intro.html#availability"><span class="std std-ref">Availability</span></a>: not Emscripten, not WASI.</p>

  219. <p>This module does not work or is not available on WebAssembly platforms

  220. <code class="docutils literal notranslate"><span class="pre">wasm32-emscripten</span></code> and <code class="docutils literal notranslate"><span class="pre">wasm32-wasi</span></code>. See

  221. <a class="reference internal" href="intro.html#wasm-availability"><span class="std std-ref">WebAssembly platforms</span></a> for more information.</p>

  222. </div>

  223. <section id="hashing-methods">

  224. <h2>Hashing Methods<a class="headerlink" href="#hashing-methods" title="Link to this heading">¶</a></h2>

  225. <div class="versionadded">

  226. <p><span class="versionmodified added">New in version 3.3.</span></p>

  227. </div>

  228. <p>The <a class="reference internal" href="#module-crypt" title="crypt: The crypt() function used to check Unix passwords. (deprecated) (Unix)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">crypt</span></code></a> module defines the list of hashing methods (not all methods

  229. are available on all platforms):</p>

  230. <dl class="py data">

  231. <dt class="sig sig-object py" id="crypt.METHOD_SHA512">

  232. <span class="sig-prename descclassname"><span class="pre">crypt.</span></span><span class="sig-name descname"><span class="pre">METHOD_SHA512</span></span><a class="headerlink" href="#crypt.METHOD_SHA512" title="Link to this definition">¶</a></dt>

  233. <dd><p>A Modular Crypt Format method with 16 character salt and 86 character

  234. hash based on the SHA-512 hash function.  This is the strongest method.</p>

  235. </dd></dl>

  236. 

  237. <dl class="py data">

  238. <dt class="sig sig-object py" id="crypt.METHOD_SHA256">

  239. <span class="sig-prename descclassname"><span class="pre">crypt.</span></span><span class="sig-name descname"><span class="pre">METHOD_SHA256</span></span><a class="headerlink" href="#crypt.METHOD_SHA256" title="Link to this definition">¶</a></dt>

  240. <dd><p>Another Modular Crypt Format method with 16 character salt and 43

  241. character hash based on the SHA-256 hash function.</p>

  242. </dd></dl>

  243. 

  244. <dl class="py data">

  245. <dt class="sig sig-object py" id="crypt.METHOD_BLOWFISH">

  246. <span class="sig-prename descclassname"><span class="pre">crypt.</span></span><span class="sig-name descname"><span class="pre">METHOD_BLOWFISH</span></span><a class="headerlink" href="#crypt.METHOD_BLOWFISH" title="Link to this definition">¶</a></dt>

  247. <dd><p>Another Modular Crypt Format method with 22 character salt and 31

  248. character hash based on the Blowfish cipher.</p>

  249. <div class="versionadded">

  250. <p><span class="versionmodified added">New in version 3.7.</span></p>

  251. </div>

  252. </dd></dl>

  253. 

  254. <dl class="py data">

  255. <dt class="sig sig-object py" id="crypt.METHOD_MD5">

  256. <span class="sig-prename descclassname"><span class="pre">crypt.</span></span><span class="sig-name descname"><span class="pre">METHOD_MD5</span></span><a class="headerlink" href="#crypt.METHOD_MD5" title="Link to this definition">¶</a></dt>

  257. <dd><p>Another Modular Crypt Format method with 8 character salt and 22

  258. character hash based on the MD5 hash function.</p>

  259. </dd></dl>

  260. 

  261. <dl class="py data">

  262. <dt class="sig sig-object py" id="crypt.METHOD_CRYPT">

  263. <span class="sig-prename descclassname"><span class="pre">crypt.</span></span><span class="sig-name descname"><span class="pre">METHOD_CRYPT</span></span><a class="headerlink" href="#crypt.METHOD_CRYPT" title="Link to this definition">¶</a></dt>

  264. <dd><p>The traditional method with a 2 character salt and 13 characters of

  265. hash.  This is the weakest method.</p>

  266. </dd></dl>

  267. 

  268. </section>

  269. <section id="module-attributes">

  270. <h2>Module Attributes<a class="headerlink" href="#module-attributes" title="Link to this heading">¶</a></h2>

  271. <div class="versionadded">

  272. <p><span class="versionmodified added">New in version 3.3.</span></p>

  273. </div>

  274. <dl class="py attribute">

  275. <dt class="sig sig-object py" id="crypt.methods">

  276. <span class="sig-prename descclassname"><span class="pre">crypt.</span></span><span class="sig-name descname"><span class="pre">methods</span></span><a class="headerlink" href="#crypt.methods" title="Link to this definition">¶</a></dt>

  277. <dd><p>A list of available password hashing algorithms, as

  278. <code class="docutils literal notranslate"><span class="pre">crypt.METHOD_*</span></code> objects.  This list is sorted from strongest to

  279. weakest.</p>

  280. </dd></dl>

  281. 

  282. </section>

  283. <section id="module-functions">

  284. <h2>Module Functions<a class="headerlink" href="#module-functions" title="Link to this heading">¶</a></h2>

  285. <p>The <a class="reference internal" href="#module-crypt" title="crypt: The crypt() function used to check Unix passwords. (deprecated) (Unix)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">crypt</span></code></a> module defines the following functions:</p>

  286. <dl class="py function">

  287. <dt class="sig sig-object py" id="crypt.crypt">

  288. <span class="sig-prename descclassname"><span class="pre">crypt.</span></span><span class="sig-name descname"><span class="pre">crypt</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">word</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">salt</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#crypt.crypt" title="Link to this definition">¶</a></dt>

  289. <dd><p><em>word</em> will usually be a user’s password as typed at a prompt or  in a graphical

  290. interface.  The optional <em>salt</em> is either a string as returned from

  291. <a class="reference internal" href="#crypt.mksalt" title="crypt.mksalt"><code class="xref py py-func docutils literal notranslate"><span class="pre">mksalt()</span></code></a>, one of the <code class="docutils literal notranslate"><span class="pre">crypt.METHOD_*</span></code> values (though not all

  292. may be available on all platforms), or a full encrypted password

  293. including salt, as returned by this function.  If <em>salt</em> is not

  294. provided, the strongest method available in <a class="reference internal" href="#crypt.methods" title="crypt.methods"><code class="xref py py-attr docutils literal notranslate"><span class="pre">methods</span></code></a> will be used.</p>

  295. <p>Checking a password is usually done by passing the plain-text password

  296. as <em>word</em> and the full results of a previous <a class="reference internal" href="#module-crypt" title="crypt: The crypt() function used to check Unix passwords. (deprecated) (Unix)"><code class="xref py py-func docutils literal notranslate"><span class="pre">crypt()</span></code></a> call,

  297. which should be the same as the results of this call.</p>

  298. <p><em>salt</em> (either a random 2 or 16 character string, possibly prefixed with

  299. <code class="docutils literal notranslate"><span class="pre">$digit$</span></code> to indicate the method) which will be used to perturb the

  300. encryption algorithm.  The characters in <em>salt</em> must be in the set

  301. <code class="docutils literal notranslate"><span class="pre">[./a-zA-Z0-9]</span></code>, with the exception of Modular Crypt Format which

  302. prefixes a <code class="docutils literal notranslate"><span class="pre">$digit$</span></code>.</p>

  303. <p>Returns the hashed password as a string, which will be composed of

  304. characters from the same alphabet as the salt.</p>

  305. <p id="index-3">Since a few <em class="manpage"><a class="manpage reference external" href="https://manpages.debian.org/crypt(3)">crypt(3)</a></em> extensions allow different values, with

  306. different sizes in the <em>salt</em>, it is recommended to use  the full crypted

  307. password as salt when checking for a password.</p>

  308. <div class="versionchanged">

  309. <p><span class="versionmodified changed">Changed in version 3.3: </span>Accept <code class="docutils literal notranslate"><span class="pre">crypt.METHOD_*</span></code> values in addition to strings for <em>salt</em>.</p>

  310. </div>

  311. </dd></dl>

  312. 

  313. <dl class="py function">

  314. <dt class="sig sig-object py" id="crypt.mksalt">

  315. <span class="sig-prename descclassname"><span class="pre">crypt.</span></span><span class="sig-name descname"><span class="pre">mksalt</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">method</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="o"><span class="pre">*</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">rounds</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#crypt.mksalt" title="Link to this definition">¶</a></dt>

  316. <dd><p>Return a randomly generated salt of the specified method.  If no

  317. <em>method</em> is given, the strongest method available in <a class="reference internal" href="#crypt.methods" title="crypt.methods"><code class="xref py py-attr docutils literal notranslate"><span class="pre">methods</span></code></a> is

  318. used.</p>

  319. <p>The return value is a string suitable for passing as the <em>salt</em> argument

  320. to <a class="reference internal" href="#module-crypt" title="crypt: The crypt() function used to check Unix passwords. (deprecated) (Unix)"><code class="xref py py-func docutils literal notranslate"><span class="pre">crypt()</span></code></a>.</p>

  321. <p><em>rounds</em> specifies the number of rounds for <code class="docutils literal notranslate"><span class="pre">METHOD_SHA256</span></code>,

  322. <code class="docutils literal notranslate"><span class="pre">METHOD_SHA512</span></code> and <code class="docutils literal notranslate"><span class="pre">METHOD_BLOWFISH</span></code>.

  323. For <code class="docutils literal notranslate"><span class="pre">METHOD_SHA256</span></code> and <code class="docutils literal notranslate"><span class="pre">METHOD_SHA512</span></code> it must be an integer between

  324. <code class="docutils literal notranslate"><span class="pre">1000</span></code> and <code class="docutils literal notranslate"><span class="pre">999_999_999</span></code>, the default is <code class="docutils literal notranslate"><span class="pre">5000</span></code>.  For

  325. <code class="docutils literal notranslate"><span class="pre">METHOD_BLOWFISH</span></code> it must be a power of two between <code class="docutils literal notranslate"><span class="pre">16</span></code> (2<sup>4</sup>)

  326. and <code class="docutils literal notranslate"><span class="pre">2_147_483_648</span></code> (2<sup>31</sup>), the default is <code class="docutils literal notranslate"><span class="pre">4096</span></code>

  327. (2<sup>12</sup>).</p>

  328. <div class="versionadded">

  329. <p><span class="versionmodified added">New in version 3.3.</span></p>

  330. </div>

  331. <div class="versionchanged">

  332. <p><span class="versionmodified changed">Changed in version 3.7: </span>Added the <em>rounds</em> parameter.</p>

  333. </div>

  334. </dd></dl>

  335. 

  336. </section>

  337. <section id="examples">

  338. <h2>Examples<a class="headerlink" href="#examples" title="Link to this heading">¶</a></h2>

  339. <p>A simple example illustrating typical use (a constant-time comparison

  340. operation is needed to limit exposure to timing attacks.

  341. <a class="reference internal" href="hmac.html#hmac.compare_digest" title="hmac.compare_digest"><code class="xref py py-func docutils literal notranslate"><span class="pre">hmac.compare_digest()</span></code></a> is suitable for this purpose):</p>

  342. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="kn">import</span> <span class="nn">pwd</span>

  343. <span class="kn">import</span> <span class="nn">crypt</span>

  344. <span class="kn">import</span> <span class="nn">getpass</span>

  345. <span class="kn">from</span> <span class="nn">hmac</span> <span class="kn">import</span> <span class="n">compare_digest</span> <span class="k">as</span> <span class="n">compare_hash</span>

  346. 

  347. <span class="k">def</span> <span class="nf">login</span><span class="p">():</span>

  348.     <span class="n">username</span> <span class="o">=</span> <span class="nb">input</span><span class="p">(</span><span class="s1">&#39;Python login: &#39;</span><span class="p">)</span>

  349.     <span class="n">cryptedpasswd</span> <span class="o">=</span> <span class="n">pwd</span><span class="o">.</span><span class="n">getpwnam</span><span class="p">(</span><span class="n">username</span><span class="p">)[</span><span class="mi">1</span><span class="p">]</span>

  350.     <span class="k">if</span> <span class="n">cryptedpasswd</span><span class="p">:</span>

  351.         <span class="k">if</span> <span class="n">cryptedpasswd</span> <span class="o">==</span> <span class="s1">&#39;x&#39;</span> <span class="ow">or</span> <span class="n">cryptedpasswd</span> <span class="o">==</span> <span class="s1">&#39;*&#39;</span><span class="p">:</span>

  352.             <span class="k">raise</span> <span class="ne">ValueError</span><span class="p">(</span><span class="s1">&#39;no support for shadow passwords&#39;</span><span class="p">)</span>

  353.         <span class="n">cleartext</span> <span class="o">=</span> <span class="n">getpass</span><span class="o">.</span><span class="n">getpass</span><span class="p">()</span>

  354.         <span class="k">return</span> <span class="n">compare_hash</span><span class="p">(</span><span class="n">crypt</span><span class="o">.</span><span class="n">crypt</span><span class="p">(</span><span class="n">cleartext</span><span class="p">,</span> <span class="n">cryptedpasswd</span><span class="p">),</span> <span class="n">cryptedpasswd</span><span class="p">)</span>

  355.     <span class="k">else</span><span class="p">:</span>

  356.         <span class="k">return</span> <span class="kc">True</span>

  357. </pre></div>

  358. </div>

  359. <p>To generate a hash of a password using the strongest available method and

  360. check it against the original:</p>

  361. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="kn">import</span> <span class="nn">crypt</span>

  362. <span class="kn">from</span> <span class="nn">hmac</span> <span class="kn">import</span> <span class="n">compare_digest</span> <span class="k">as</span> <span class="n">compare_hash</span>

  363. 

  364. <span class="n">hashed</span> <span class="o">=</span> <span class="n">crypt</span><span class="o">.</span><span class="n">crypt</span><span class="p">(</span><span class="n">plaintext</span><span class="p">)</span>

  365. <span class="k">if</span> <span class="ow">not</span> <span class="n">compare_hash</span><span class="p">(</span><span class="n">hashed</span><span class="p">,</span> <span class="n">crypt</span><span class="o">.</span><span class="n">crypt</span><span class="p">(</span><span class="n">plaintext</span><span class="p">,</span> <span class="n">hashed</span><span class="p">)):</span>

  366.     <span class="k">raise</span> <span class="ne">ValueError</span><span class="p">(</span><span class="s2">&quot;hashed version doesn&#39;t validate against original&quot;</span><span class="p">)</span>

  367. </pre></div>

  368. </div>

  369. </section>

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  382. <li><a class="reference internal" href="#"><code class="xref py py-mod docutils literal notranslate"><span class="pre">crypt</span></code> — Function to check Unix passwords</a><ul>

  383. <li><a class="reference internal" href="#hashing-methods">Hashing Methods</a></li>

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