Comment by tptacek
13 hours ago
It's not my intuition that materializing secrets to files is a better way to protect them than just injecting them into the environment, where they don't persist.
13 hours ago
It's not my intuition that materializing secrets to files is a better way to protect them than just injecting them into the environment, where they don't persist.
> It's not my intuition that materializing secrets to files is a better way to protect them than just injecting them into the environment, where they don't persist.
I don't really follow this reasoning. Where are you injecting the secrets from?
Dev/shm is used to materialize them, and then you have the ability to isolate the downstream code you might use from accessing it by dropping permissions or sandboxing it away from a file. You cannot really hide your environment from anything in process, since it's such a low level construct.
Thus it's easier to leak environment unintentionally, leaking file contents takes effort.
Not at all clear why this is a better setup than a launcher shim that pulls secrets from a secret store and injects them into the environment as the program launches --- which is a pretty normal shape for these things to take.
I guess you could be thinking "subprocess inheritance" as a downside? But subprocesses often need secrets, and if you arrange for that with the filesystem you have the same problem. And, of course, files leak all the time.
More to the point, though: none of this has anything to do with whether you should add secrets to your .bashrc or whatever, which is the argument I'm seeing on the thread.
Have you seen this where eBPF patches secrets inside TLS send buffers? https://github.com/spinningfactory/kloak
Now you have to be much more clever to leak them :)
It doesn't need to be a traditional file. You can pass it as essentially a read-once file by using stdin. Depending on your desire for modernity, similar behavior can be obtained by leaving a file handle open for the exec-ed process to inherit, via a Unix socket, or even a lightweight TCP daemon.
The env is technically still kind of a file on linux at least (through /proc).
Sometimes I feel like stdin or an unlinked memory mapped file might be the best location for this stuff. Wish Linux had a cloexec+1 option, where an fd is closed after two execs, so you can set up a child process for success.
Only in the sense that everything is technically a kind of a file given access to proc.
(Edit: I need to read up on this better)