4 ms·

Bad idea cat /proc/<pid>/environ

• cjbprime 9y ago
  Wait, what's your threat model? Surely you're not imagining that you can pass data from one process to another without root being able to see it? (On Linux, since you're using /proc.) Other users' processes can't see /proc/$pid/environ, unlike using cmdline.
  • pentagonpapers 9y ago
    Sure, it still leaves room for malware etc accessing data if it's running as the main user. I think the better solution is to read it out of a wallet into stdin
  • BenjiWiebe 9y ago
    Don't recall right now for sure, but doesn't ps have an option to display the processes environment? I've done it by accident a few times and it does not take root.
    • cjbprime 9y ago
      It has an option (e) to attempt to display environment variables, but ps is just a program that reads from /proc, and the kernel enforces isolation of environment variables by breaking reads to /proc/pid/environ for processes you don't own (or more precisely, can't ptrace), so `ps e` can't show anything for those processes. λ whoami cjb λ cat /proc/1/cmdline /sbin/init% λ cat /proc/1/environ cat: /proc/1/environ: Permission denied
      • tetha 9y ago
        And if you can see /proc/*/environ, you can probably attach to the process via gdb and read the secret from the process memory. At that point, it's not relevant how the secret was passed to the process. Unless the secret is some kind of one-time token, or time based token, but then it's also not relevant how the secret was passed to the process. It's invalidated soon.
  • Fnoord 9y ago
    > On Linux, since you're using /proc. Exactly; macOS doesn't use /proc.