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> Some operating systems still make every process’s environment variables world readable. (But, in all the Linuxes I’ve seen, /proc/<pid>/environ is not world-r

> Some operating systems still make every process’s environment variables world readable. (But, in all the Linuxes I’ve seen, /proc/<pid>/environ is not world-readable.) A couple years ago this came up and someone made this claim, but no one could ever name an OS where this is the case. Maybe someone on HN knows one? :)

matja 5y ago
The procfs hidepid option still defaults to 0 (visible), but systemd will set it to 2 (invisible).
- formerly_proven 5y ago
  On Linux, the permissions on /proc/$PID/environ are the same permissions you'd need to read the memory of the process, so just being able to list that dirent doesn't give you anything. Though I do think that command lines being visible to other users is a design flaw.
deleted 5y ago
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mkj 5y ago
AIX 5.2? That was EOL 2008, it seems hardly worth warning about these days. https://github.com/mobile-shell/mosh/issues/156#issue-4077893 https://github.com/mobile-shell/mosh/issues/156#issue-407789...
NelsonMinar 5y ago
Oh oh I know this! Ultrix 2.2 in 1990 did this. Not via /proc, which did not exist in that OS, but via the ps command. From the Ultrix Security Guide for Users: "Note that denying other users read permission [to your .profile] does not mean that they cannot find your PATH or any other of your environment variables. The -eaxww options to the ps command display in wide format the environment variables for all processes on the system" Ultrix 2.2 was a BSD 4.2 variant by DEC. I doubt it was unique in this behavior, my guess is all BSDs leaked info in this way, but I don't have a reference handy. mkj's example in this thread of AIX suggests Sys V did it too. Modern Linux only shows you your own processes' environment variables. (Young people of Hacker News: beware what operating systems you learn because 31 years later their idiosyncracies will still be burned into your brain.)

matja 5y ago

The procfs hidepid option still defaults to 0 (visible), but systemd will set it to 2 (invisible).

formerly_proven 5y ago
On Linux, the permissions on /proc/$PID/environ are the same permissions you'd need to read the memory of the process, so just being able to list that dirent doesn't give you anything. Though I do think that command lines being visible to other users is a design flaw.

deleted 5y ago

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mkj 5y ago

AIX 5.2? That was EOL 2008, it seems hardly worth warning about these days. https://github.com/mobile-shell/mosh/issues/156#issue-4077893 https://github.com/mobile-shell/mosh/issues/156#issue-407789...

NelsonMinar 5y ago

Oh oh I know this! Ultrix 2.2 in 1990 did this. Not via /proc, which did not exist in that OS, but via the ps command. From the Ultrix Security Guide for Users: "Note that denying other users read permission [to your .profile] does not mean that they cannot find your PATH or any other of your environment variables. The -eaxww options to the ps command display in wide format the environment variables for all processes on the system" Ultrix 2.2 was a BSD 4.2 variant by DEC. I doubt it was unique in this behavior, my guess is all BSDs leaked info in this way, but I don't have a reference handy. mkj's example in this thread of AIX suggests Sys V did it too. Modern Linux only shows you your own processes' environment variables. (Young people of Hacker News: beware what operating systems you learn because 31 years later their idiosyncracies will still be burned into your brain.)