How do I create temporary files and directories in a secure way on linux?
mountaing last edited by mountaing
Also see: Man page for mktemp
Many know of putting the process ID at the end of the file /tmp/mylog.$$, which can be done as long as there is nothing sensitive in the file. The $$ just puts your shell process id at the end of the file.
The file name is created with these permissions; anyone can read it.
ls -l /tmp/mylog.5929 -rw-rw-r-- 1 trainer trainer 0 Nov 13 11:18 mylog.5929
A better way is to always use
mktempin scripts to make the file name difficult for anyone to guess.
Create a temporary file with 10 random characters.
$ mktemp /tmp/mylog.XXXXXXXXXX /tmp/mylog.LlIu9B0PPw
Notice the file permissions are a lot more secure.
$ ls -l /tmp/mylog.LlIu9B0PPw -rw------- 1 trainer trainer 0 Nov 13 11:15 /tmp/mylog.LlIu9B0PPw
The same can be done for directories. Assuming TMPDIR is set to /tmp.
$ mktemp -d -t my_logfiles.XXXXXXXXXX /tmp/my_logfiles.l2DPRJuGne
$ ls -ld /tmp/my_logfiles.l2DPRJuGne drwx------ 2 trainer trainer 2 Nov 13 11:24 /tmp/my_logfiles.l2DPRJuGne
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