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From: "ibrahim via 9fans" <9fans@9fans.net>
To: 9fans <9fans@9fans.net>
Subject: [9fans] serious bug in ramfs and code based on it
Date: Wed, 3 May 2023 22:32:57 -0400	[thread overview]
Message-ID: <16831675770.A5cCC4.81650@composer.9fans.topicbox.com> (raw)

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The classic implementation of ramfs and many other user fileservers based on it have a serious bug regarding the 9p protocol :

If you open a file for which you have Read/Execute Permission you are free to write to that file by sending Twrite requests. 
*
*
*rwrite doesn't check if the file was opened for read, write or execute. *

A possible solution for this problem is enhancing the meaning of Fid.open from an indicator for open files to an indicator for open files and the mode they were opened :

0x80 ... file is open
0x40 ... opened for reading
0x20 ... opened for writing
0x10 ... opened for execution

While ramfs is regared as a toy program with minimal permission checking many user file servers around are based on this example like all the tools in tapefs.

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                 reply	other threads:[~2023-05-04  2:33 UTC|newest]

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