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POAuto update: Is this secure?
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copied!<h2><a href="http://code.google.com/p/dotnetautoupdate/" rel="nofollow noreferrer">Dot Net Auto Update</a></h2> <p>I felt like .net was lacking a simple secure automatic update library so I've implemented something and put it up <a href="http://code.google.com/p/dotnetautoupdate/" rel="nofollow noreferrer">here</a>. Before anyone considers using the library I was keen for the update process to get a bit a peer review. </p> <h3>Here are the steps:</h3> <ul> <li>The client software is populated with a public key and URI to poll.</li> <li>Client polls a URI for a manifest file.</li> <li>Manifest is downloaded and signature (in a separate ".signature") is used to check that the manifest is valid.</li> <li>A list of pending updates is parsed out of the manifest (to show to the user).</li> <li>The installer file is downloaded and again is verified with a corresponding ".signature" file. (the downloaded file will be protected with ACLs)</li> <li>The installer is run.</li> </ul> <h3>Mitigated threats:</h3> <ul> <li>The manifest signature should prevent any malicious downloads ("<a href="http://blogs.pcmag.com/securitywatch/2008/05/safari_carpet_bombing.php" rel="nofollow noreferrer">carpet bombing</a>")</li> <li>The installer signature should prevent any MITM attacks from sending malicious installers</li> <li>Protecting the downloaded installer with ACLs should prevent any local escalation attacks.</li> </ul> <h3>Unmitigated threats:</h3> <ul> <li>A <a href="http://en.wikipedia.org/wiki/MiTM" rel="nofollow noreferrer">MITM</a> attack where the attacker always reports "no updates available". (Could keep a client at a vulnerable version)</li> </ul> <h3>References:</h3> <ul> <li><a href="http://www.cs.umass.edu/~kevinfu/secureupdates/secureupdates-hotsec06.pdf" rel="nofollow noreferrer">Secure Software Updates: Disappointments and New Challenges</a></li> <li><a href="http://www.doxpara.com/DMK_BO2K8.ppt" rel="nofollow noreferrer">Black Ops 2008: It’s The End Of The Cache As We Know It </a></li> <li><a href="http://blog.metasploit.com/2008/07/evilgrade-will-destroy-us-all.html" rel="nofollow noreferrer">Evilgrade Will Destroy Us All</a></li> </ul> <p><br /></p> <h1>What have I missed?</h1> <p><br /></p>

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