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| <div class="chapter"> |
| <div class="titlepage"><div><div><h1 class="title"> |
| <a name="sharing"></a>Sharing PKCS#11 modules</h1></div></div></div> |
| <div class="toc"><dl class="toc"> |
| <dt><span class="section"><a href="sharing.html#sharing-problem">Multiple consumers of PKCS#11 in a process</a></span></dt> |
| <dt><span class="section"><a href="sharing-managed.html">Managed modules</a></span></dt> |
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| <div class="section"> |
| <div class="titlepage"><div><div><h2 class="title" style="clear: both"> |
| <a name="sharing-problem"></a>Multiple consumers of PKCS#11 in a process</h2></div></div></div> |
| <p>As more and more applications and libraries use PKCS#11 we run |
| into a very basic problem. The PKCS#11 modules cannot be initialized and |
| finalized properly without coordination between the various consumers. |
| </p> |
| <p>An example: An application might use GnuTLS for |
| TLS connections, and use libgcr for display of certificates. Both of |
| these want to load (and initialize) the same PKCS#11 modules. There are |
| many places where this situation occurs, including large applications |
| like Evolution which due to their dependencies end up using both NSS and |
| GnuTLS.</p> |
| <p>Consumer A loads a PKCS#11 module and uses the module's |
| C_Initialize function to initialize it, which works as expected. |
| When consumer B initializes the module (also using C_Initialize), |
| the error code <code class="literal">CKR_CRYPTOKI_ALREADY_INITIALIZED</code> |
| is correctly returned. This is normal PKCS#11 specification |
| defined behavior for when a module is initialized twice in the |
| same process. If consumer B is aware of this situation they may |
| choose to ignore this error code.</p> |
| <p>However when the consumer A is done with its use of the |
| PKCS#11 module it finalizes the module using the module's |
| C_Finalize function. This is expected of a well behaved PKCS#11 |
| consumer. This then causes errors and/or crashes for consumer B, |
| which cannot know that the module has now been finalized out |
| from underneath it.</p> |
| <p>It is necessary for the two consumers to coordinate their |
| initialization and finalization in some fashion. In |
| <code class="literal">p11-kit</code> we provide this coordination in a |
| loosely coupled, backwards compatible, and flexible way.</p> |
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