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Top Forums UNIX for Dummies Questions & Answers Security issue and temp files Post 302358193 by mojoman on Thursday 1st of October 2009 03:19:15 PM
Old 10-01-2009
Security issue and temp files

Hello,

One of the senior network admins at work told me that I should not hard code temp files into my scripts. Rather I should use the mktemp commands in the script to create them on the fly.

His argument was that if a malicious user knew the name of my temp files in the script they could create a symbolic link based on that name to a more important file to overwrite it. So if my temp file was called temp1 the hacker could create a symbolic link to say /etc/passwd.

On my system I created a symbolic link called temp1 pointing to /etc/passwd and then I used touch to create a file called temp1 to see what would happen. But when I tried to create the file with touch, most likely because the symbolic link called temp 1 was already there.

Hence my question: Is that the sysadmin said is true in light of my experiment? And if not, why should I use mktemp instead of hard coding tempf files in my scripts?
 

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GZEXE(1)						    BSD General Commands Manual 						  GZEXE(1)

NAME
gzexe -- create auto-decompressing executables SYNOPSIS
gzexe [-d] file ... DESCRIPTION
The gzexe utility uses gzip(1) to compress executables, producing executables that decompress on-the-fly when executed. This saves disk space, at the cost of slower execution times. The original executables are saved by copying each of them to a file with the same name with a '~' suffix appended. After verifying that the compressed executables work as expected, the backup files can be removed. The options are as follows: -d Decompress executables previously compressed by gzexe. The gzexe program refuses to compress non-regular or non-executable files, files with a setuid or setgid bit set, files that are already com- pressed using gzexe or programs it needs to perform on-the-fly decompression: sh(1), mktemp(1), rm(1), echo(1), tail(1), gzip(1), and chmod(1). SEE ALSO
gzip(1) CAVEATS
The gzexe utility replaces files by overwriting them with the generated compressed executable. To be able to do this, it is required that the original files are writable. BSD
July 30, 2003 BSD
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