Environment variables are a legacy mess: Let's dive deep into them

https://allvpv.org/haotic-journey-through-envvars/

by signa11 • 9 months ago

234 185 9 months ago

rsyring4• 9 months ago

Environment variables are often used to pass secrets around. But, despite its ubiquity, I believe that's a bad practice:

- On Linux systems, any user process can inspect any other process of that same user for it's environment variables. We can argue about threat model but, especially for a developer's system, there are A LOT of processes running as the same user as the developer.

- IMO, this has become an even more pronounced problem with the popularity of running non-containerized LLM agents in the same user space as the developer's primary OS user. It's a secret exfiltration exploiter's dream.

- Environment variables are usually passed down to other spawned processes instead of being contained to the primary process which is often the only one that needs it.

- Systemd exposes unit environment variables to all system clients through DBUS and warns against using environment variables for secrets[1]. I believe this means non-root users have access to environment variables set for root-only units/services. I could be wrong, I haven't tested it yet. But if this is the case, I bet that's a HUGE surprise to many system admins.

I think ephemeral file sharing between a secret managing process (e.g. 1Password's op cli tool) and the process that needs the secrets (flask, terraform, etc.) is likely the only solution that keeps secrets out of files and also out of environment variables. This is how Systemd's credentials system works. But it's far from widely supported.

Any good solutions for passing secrets around that don't involve environment variables or regular plain text files?

Edit: I think 1Password's op client has a good start in that each new "session" requires my authorization. So I can enable that tool for a cli sessions where I need some secrets but a rogue process that just tries to use the `op` binary isn't going to get to piggyback on that authorization. I'd get a new popup. But this is only step 1. Step 2 is...how to share that secret with the process that needs it and we are now back to the discussion above.

1: https://www.freedesktop.org/software/systemd/man/latest/syst...

robertlagrant2• 9 months ago

On Linux systems, any user process can inspect any other process of that same user for it's environment variables. We can argue about threat model but, especially for a developer's system, there are A LOT of processes running as the same user as the developer.

This is a very good point I'd never realised! I'm not sure how you get around it, though, as if that program can even find a credential and decrypt a file, if it runs as the user then everything else can go find that credential as well.

rsyring4• 9 months ago

I added a note to my original post about how 1Password's cli tool work. Access to the binary doesn't mean automatic access to any authorized session. I think that's a good start. In my case, I have it tied into my fingerprint reader, so if something want's access to a secret using `op` I get a prompt to authorize. If I haven't just called `op` myself, I know it's a suspect request.

chasil2• 9 months ago

If a root exploit is leveraged, then /proc/*/environ of all processes is visible to the adversary.

The classical alternative has been to store (FTP) credentials in a .netrc file (also used by curl).

I have some custom code to pull passwords out of a SQLite database.

For people who are really concerned with this, a "secrecy manger" is more appropriate, such as Cyberark conjur and summon, or Hashicorp Vault.

formerly_proven2• 9 months ago

--passphrase-fd was always the correct thing to do (gpg has had it for ages), but support for that is very meager. I mean, you can’t even kubectl login using environment variables, you pretty much have to pass tokens through command-line arguments and we’ve known that’s terrible for around forty-five years.

bbkane2• 9 months ago

Any good cross-platform and easy ways to share secrets without using environment variables?

zdc1• 9 months ago

Point to a file? E.g. `CONFIG_PATH=/etc/myapp/config.ini /opt/myapp`

That being said, I still use env vars and don't plan on stopping. I just haven't (yet?) seen any exploits or threat models relating to it that would keep me up at night.

matthew16550• 9 months ago

SOPS can be part of the solution. It takes care of encrypting and decrypting config files.

https://github.com/getsops/sops

skylurk• 9 months ago

I've used keyring, but ultimately does not solve the issue of every application running under the same user.

https://pypi.org/project/keyring/

cedws3• 9 months ago

Linux security model is pretty broken without namespaces. systemd has some bells and whistles that help but if you want something better than environment variables you're naturally going to reach for cgroups.

throwaway127482• 9 months ago

cgroups aren't relevant here, I think. Not sure if that was just a typo, since you did mention namespaces in the first sentence. PID and user namespaces in particular are relevant here.

ux2664784• 9 months ago

Linux's namespaces are not a security mechanism. Please do not use them as one.

171862744011• 9 months ago

Linux/Unix security model is that different actors are represented by different OS users. When you don't do that, it's already like inviting the burglars in your living room.

mhitza• 9 months ago

Any good solutions for passing secrets around that don't involve environment variables or regular plain text files?

memfd_secret comes to mind https://man7.org/linux/man-pages/man2/memfd_secret.2.html

I haven't seen much language support for it, though. On one part maybe because it's Linux only.

People that write in Rust (and maybe Go, depends how easy FFI is) should give it a try.

I wanted for a time to get some support for it in PHP, since wrapping a C function should be easy, but the thought of having to also modify php-fpm put a dent in that. I can't and don't want to hack on C code.

In practice it'd be great if the process manager spawn children after opening a secret file descriptor, and pass those on. Not in visible memory, not in /proc/*/environ

llimllib• 9 months ago

For go, it's available in /x/sys/unix: https://pkg.go.dev/golang.org/x/sys/unix#MemfdSecret

monocasa4• 9 months ago

Oh, I like that.

You should be able to build up a nice capability model to get access to those memfds from daemon too rather than having to spawn out of a process manager if that model fits your use case a bit better.

bjourne5• 9 months ago

If are like most users you have secrets stored in read-protected files in ~/.ssh. There's nothing wrong with that.

SoftTalker2• 9 months ago

They are (should be) encrypted though, and not usable by someone who might somehow gain access to your ~/.ssh files.

amluto4• 9 months ago

Since at least 2012, environment variables have been at least as secure as ordinary memory:

    commit b409e578d9a4ec95913e06d8fea2a33f1754ea69
    Author: Cong Wang <xiyou.wangcong@gmail.com>
    Date:   Thu May 31 16:26:17 2012 -0700
    
        proc: clean up /proc/<pid>/environ handling

You can't read another process's environment unless you can ptrace-read the process, and if you can ptrace-read the process you know all its secrets anyway.

cmdline is a different story.

rsyring4• 9 months ago

I've never tried to use ptrace-read to read secrets from a running process's memory so I can't comment on that part.

I had always assumed getting secrets from a running process' memory was non-trivial and/or required root permissions but maybe that's a bad assumption.

However, reading a process' environment is as trivial as:

`cat /proc/123456/environ`

as long as it's ran by the same user. No ptrace-read required.

marcosdumay• 9 months ago

Just to clarify, that means that by default every process of the same user can access the variables. But it doesn't really matter because by default every process of the same user can read any secret directly from the target process anyway, right?

And that the right thing to do if you want to harden your system is to disallow ptrace-read, and not bother changing software that uses environment variables?

Because I think most people that just try will be able to read the variables of any process on their computer.

vendiddy2• 9 months ago

Not an answer, but I do wish there was a low level primitive and a corresponding high level language construct to pass around secrets.

Something like: my_secret = create_secret(value)

Then ideally it's an opaque value from that point on

171862744011• 9 months ago

my_secret = getenv ("VALUE");

:-)

jkrejcha6• 9 months ago

Until when? Secrets in applications in many cases (I would probably wager majority of the cases) are only useful if they're in plaintext at some point, for example if you're constructing a HTTP client or authenticating to some other remote system.

As far as high-level language constructs go, there were similarish things like SecureString (in .NET) or GuardedString (in Java), although as best as I can tell they're relatively unused mostly because the ergonomics around them make them pretty annoying to use.

motorest• 9 months ago

Environment variables are often used to pass secrets around. But, despite its ubiquity, I believe that's a bad practice:

I think environment variables are recommended to pass configuration parameters, and also secrets, in containerized applications managed by container orchestration systems.

By design, other processes cannot inspect what environment variables are running in a container.

Also, environment variables are passed to child processes because, by design, the goal is to run child processes in the same environment (i.e., same values) as the parent process, or with minor tweaks. Also, the process that spawns child processes is the one responsible for set it's environment variables, which means it already has at least read access to those secrets.

All in all I think all your concerns are based on specious reasoning, but I'll gladly discuss them in finer detail.

rsyring4• 9 months ago

Please note that in my OP, I never mentioned containers.

Let's say, as a developer, I need to do some API interactions with GitHub. So, in a terminal, using 1Password's cli tool `op`, I load my GH API token and pass it to my Python script that is doing the API calls.

Presumably, the reason I use that process is because I want to keep that token's exposure isolated to that script and I don't want the token exposed on the filesystem in plaintext. There is no reason for every process running as my user on my laptop to have access to that token.

But, that's not how things work. The Claude agent running in a different CLI session (as an example) also now has access to my GitHub token. Or, any extension I've ever loaded in VS Code also has access. Etc.

It's better than having it in plain text on the file system but not by much.

Additionally, unless I've misunderstood the systemd docs, if you are passing secrets through environment variables using unit's `Environment` config, ANY USER on a server can read those values. So now, we don't even have user isolation in effect.

My reasoning is pretty plain. It could be wrong, but it's hardly specious.

rustyminnow• 9 months ago

I think in the context of containers you're right, there's a level of isolation and secrets are probably fine. But I think under other contexts that lack that isolation (e.g. bare-metal processes, local dev tooling) there are extra concerns.

(inb4: container env-vars are isolated from other containers, not from processes on the host system)

openasocket• 9 months ago

By design, other processes cannot inspect what environment variables are running in a container.

That’s not exactly true. If a process is running in a container, and someone is running bash outside of that container, reading that processes environment variables is as simple as “cat /proc/<pid>/environ”. If you meant that someone in one container cannot inspect the environment variables of a process running in a different container, that’s more true. That said, containers should not be considered a security boundary in the same way a hypervisor is.

jkrejcha6• 9 months ago

- On Linux systems, any user process can inspect any other process of that same user for it's environment variables. We can argue about threat model but, especially for a developer's system, there are A LOT of processes running as the same user as the developer.

Here's the thing though, the security model of most operating systems means that running a process as a user is acting as that user. There are some caveats (FreeBSD has capsicum, Linux has landlock, SELinux, AppArmor, Windows has integrity labels), but in the general case, if you can convince someone to run something, the program has delegated authority to act on behalf of that user. (And some user accounts on many systems may have authority to impersonate others.)

While it's by no means the only security model (there exists fully capability based operating systems out there), it's the security model that is used for most forms of computing, for better or worse. One of the consequences of this is that you can control anything within your domain. I can kill my own processes, put them to sleep, and most importantly for this, debug them. Anything I own that has secrets can grab them my ptrace/process_vm_readv/ReadProcessMemory/etc.

Narushia• 9 months ago

Any good solutions for passing secrets around that don't involve environment variables or regular plain text files?

Honestly, my answer is still systemd-creds. It's easy to use and avoids the problem that plain environment variables have. It's a few years old by now, should be available on popular distros. Although credential support for user-level systemd services was added just a few weeks ago.

A TL;DR example of systemd-creds for anyone reading this:

    # Run the initial setup
    systemd-creds setup

    # This dir should have permissions set to 700 (rwx------).
    credstore_dir=/etc/credstore.encrypted
    # For user-level services:
    # credstore_dir="$HOME/.config/credstore.encrypted"
    
    # Set the secret.
    secret=$(systemd-ask-password -n)
    
    # Encrypt the secret.
    # For user-level services, add `--user --uid uidhere`.
    # A TPM2 chip is used for encryption by default if available.
    echo "$secret" | systemd-creds encrypt \
        --name mypw - "$credstore_dir/mypw.cred"
    chmod 600 "$credstore_dir/mypw.cred"

You can now configure your unit file, e.g.:

    [Service]
    LoadCredentialEncrypted=mypw:/etc/credstore.encrypted/mypw.cred

The process you start in the service will then be able to read the decrypted credential from the ephemeral file `$CREDENTIALS_DIR/mypw`. The environment variable is set automatically by systemd. You can also use the command `systemd-creds cat mypw` to get the value in a shell script.

At least systemd v250 is required for this. v258 for user-level service support.

mixmastamyk• 9 months ago

You've described the classic Unix security model, with minor improvements. While decent for the time it is showing its age. Specifically the difficulty in adapting to cheap, ubiquitous computing which it wasn't designed for.

If you need to keep secrets from other processes—don't run them under the same user account. Or access them remotely, although that brings other tradeoffs and difficulties.

lelanthran• 9 months ago

Any good solutions for passing secrets around that don't involve environment variables or regular plain text files?

Plain text files are fine, it's the permissions on that file that is a problem.

The best way is to be in control of the source to the program you want to run then you can make a change to always protect against leaking secrets by starting the program as a user that can read the secrets field. After startup the program reads the whole file and immediately drops privileges by switching to a user that cannot read the secrets file.

Works for more than just secrets too.

simonask2• 9 months ago

Interesting read. Another interesting fact is that `setenv()` is fundamentally broken on POSIX, and should essentially never be called in library code. In application code, it should be called only in the absence of any alternative, and certainly before any threads have started.

The reason is that `getenv()` hands out raw pointers to the variables, so overwriting a variable using `setenv()` is impossible to guard against. Treat with extreme caution.

wmf• 9 months ago

AFAIK Solaris solved that problem but Linux refuses to copy their solution.

foofoo12• 9 months ago

Link?

ori_b3• 9 months ago

Their solution was that setenv leaks memory rather than overwriting in place.

FreeBSD does the same. See here for discussion: https://freebsd-current.freebsd.narkive.com/NwqZQDWm/fix-for...

Analemma_• 9 months ago

IIRC the Solaris implementation of getenv()/setenv() leaks memory, because they want it to still be POSIX-compatible and the POSIX API has a "obey the spec, don't leak memory, be thread-safe -- pick 2" thing going on and you can't actually have a bug-free solution that keeps compatibility with decades of Unix applications.

Arguably that's less harmful than the thread-safety issues on Linux, but there's no perfect solution here as long as POSIX stays what it is.

nrds2• 9 months ago

I think it's worth specifically calling out that the right way to set environment variables is in execve() only, as communication across an exec() is the precise niche for which they are the right tool.

sureglymop4• 9 months ago

Why are they the right tool for that instead of passing data with program args or another way of IPC?

skissane2• 9 months ago

NetBSD has had getenv_r() for ages, [0] and I believe FreeBSD has very recently copied it. [1] If FreeBSD has it, macOS might eventually adopt it too. People tried already to get it into both glibc and POSIX, and it was rejected, but if it becomes more common on other platforms, that increases the chance they’ll both eventually accept it.

[0] https://man.netbsd.org/getenv_r.3

[1] https://github.com/freebsd/freebsd-src/commit/873420ca1e6e8a...

layer82• 9 months ago

You still don’t know if some library you use calls getenv() and stores the returned pointer (or, potentially, runs in a different thread). Using getenv_r() protects your code against setenv(), but other code that may be using getenv() is still unprotected against your (or anyone else’s) use of setenv().

Ferret7446• 9 months ago

Why would you ever call setenv in library code to begin with?

simonask2• 9 months ago

I mean, it would be perfectly fine if it wasn’t for the fact that it’s not perfectly fine…

shmerl• 9 months ago

POSIX-specified utilities use uppercase envvars, but that’s not prescriptive for your programs. Quite the contrary: you’re encouraged to use lowercase for your envvars so they don’t collide with the standard tools.
But in reality, not many applications use lowercase. The proper etiquette in software development is to use ALL_UPPERCASE

I always prefer lower case for env variables in scripts. Thanks for pointing out that it can help reduce clashes with standard tools.

amelius3• 9 months ago

Another legacy mess:

    Argument list too long

It's absolutely crazy that this isn't a dynamically resizable vector.

formerly_proven2• 9 months ago

It is, there’s just a limit set by the kernel for the number of pages the command line as a whole can occupy or something like that.

amelius3• 9 months ago

No, it's still an artificial limit, even if you can change it (usually after your command has failed).

chasil2• 9 months ago

The xargs command was designed to address this. From this perspective, it is a kludge.

amelius3• 9 months ago

Yes, and xargs isn't the same thing. It splits a single command into multiple commands, which can lead to surprises.

The issue also breaks scripts left and right. It really needs to be solved.

the__alchemist2• 9 months ago

I get anxiety whenever I need to set an environment var on Linux. There are (somewhat distro-specific) ways that work properly, but the usual procedures you find online stops working once you reboot (or close the terminal I think?). They should add a simple env var GUI like Windows has that just works, and isn't terminal-specific. Windows has the annoyance of needing to restart the the terminal (or open a new one) for changes to take effect, but works well other than that.

zdragnar2• 9 months ago

but the usual procedures you find online stops working once you reboot (or close the terminal I think?)

The environment isn't persistent between sessions. That means you need to make the change in a way that runs on every new session (login or new terminal window).

Depending on how your system is configured:

.bash_profile gets run once on every login

.bashrc gets run once on every non-login new session (i.e. a new terminal window)

It's typical, if using these files, to do something like this:

    if [ -f ~/.bashrc ]; then
        source ~/.bashrc
    fi

in the .bash_profile file, putting most other things in .bashrc, such that you don't have to worry about the distinction.

If you're not even using bash or bash-likes at all, but instead something like Zsh, fish, etc you'll need to set things the way they want to be set there.

They should add a simple env var GUI like Windows has that just works, and isn't terminal-specific

This doesn't exist in linux, because there isn't "one place" that all possible terminals draw from. Conceivably, it's possible to write a GUI tool that reads your .bashrc file, looks for anything that resembles a variable, parses the bash code to look for ways it is set, and then present a GUI tool that could update it in common cases, but... it's way easier to just write the change in a text editor.

petre• 9 months ago

Conceivably, it's possible to write a GUI tool that reads your .bashrc file

What's wrong with an envfile or envdir? The envdir is kind of annoying but at least you can set permissions on the files inside it.

SAI_Peregrinus• 9 months ago

That applies if you use bash. If you use another shell, you'll need to use that shell's methods to set environment variables in the config(s). And probably still need to set them for bash so that bash scripts get the correct env vars.

NixOS & home-manager do have functions that can set environment variables across all shells enabled via either of those systems. So I've got `programs.bash.enable = true;` && `programs.fish.enable = true;` && `home.sessionVariables = { EDITOR = "nvim"; };` in my home-manager config for example. A GUI editor for that would certainly be possible.

jcelerier• 9 months ago

Funny, as a primarily linux user the windows behaviour irks me to no end, it's the cause of so many recurrent problems on end-user machines with so many apps that pollute environment.. and then you wonder why something doesn't work and then it turns out that for some reason you're using $SOFTWARE from c:\Perl64\bin instead of its proper place

NekkoDroid• 9 months ago

On systemd systems you can just either set KEY=VALUE pairs in `/etc/environment` or any file in `/etc/environment.d/` (and technically a few other places [0]). In theory it should be relatively easy to write a GUI for it by manually parsing the files.

The application restarting part can't really be fixed, since environment variables aren't ever injected to a running process and can only be changed by the process itself (terms and conditions may apply) and even changes during runtime could be ignored since the program itself may have cached some already computed value based on the variable.

[0] https://www.freedesktop.org/software/systemd/man/latest/envi...

the__alchemist2• 9 months ago

Good info. I may write a script or tiny program to help with this.

csours• 9 months ago

https://xkcd.com/927/ - Standards

Situation: There are 14 competing ways to set environment variables on Linux

We should create a universal way that just works and isn't terminal specific to set environment variables!

Situation: There are 15 competing ways to set environment variables on Linux

arcfour• 9 months ago

...you just put them in your shell RC file??

This is much simpler than having to remember where the dang environment variables button is in "advanced system settings" or whatever awful command prompt syntax sets it permanently.

bjourne5• 9 months ago

We're almost rid of dotfiles in $HOME. Can we please also get rid of the abuse of environment variables for configuration? There is no reason your program needs to muck up the environment table of every process by defining MY_PROGRAM_API_KEY instead of taking a command line argument or reading a configuration file. It's not "secure" just because it's not on the command line. And it will mess up for users because it's nigh impossible to ensure you have the same environment variables over all login types. The variable might be there when you run locally, but not in an ssh session or cron. Some ephemeral configuration such as LD_LIBRARY_PATH and PWD is difficult to handle without environment variables, but those are rare exceptions and not the norm.

Contribute to a clean environment! Don't use environment variables for configuration! </rant>

171862744011• 9 months ago

This problem is also removed by just not exporting the variables. Also you can just pass an envp to execvE.

bjourne5• 9 months ago

"MY_APP_SECRET_KEY=bla myapp" hardly accomplishes anything substantial over "myapp --secret-key=blah" It's just a less robust and less well-supported command-line interface. It's not supported by most gui launchers, PowerShell, nor many cron implementations, for example.

phito• 9 months ago

They're the standard for Docker container configuration tho. Otherwise I do agree.

mixedbit• 9 months ago

Depending on your system, passing secrets via environment can be more secure than passing secrets via a command line. Command line arguments of all running processes can be visible to other users of the system, environment variables are usually not.

aleksandrm• 9 months ago

That was a hard to read font.

lemontheme• 9 months ago

Huh... Guess it's what you're used to.

First thing that struck me about the site is how beautiful I found it. I even inspected the font: Iosevka Web, apparently.

db48x• 9 months ago

Change your browser settings. You can tell the browser what font you prefer to use, and set minimum font sizes. You can also turn off remote fonts, so that pages can only use fonts you already have. Then you can just uninstall any fonts you don’t like or that you cannot read easily.

jml7c5• 9 months ago

I'm surprised you say that. Iosevka is quite beloved as a monospace font. I use it for all my terminals, etc.

layer82• 9 months ago

Prose in monospace is harder to read regardless of the specific font.

WalterBright• 9 months ago

I gave up on environment variables long ago. Now my compilers read a dmd.conf file that is in the same directory as the compiler executable.

m3047• 9 months ago

...and people have to find special ways to set them. I didn't even know that pam_env existed until a recent security vulnerability announcement. It's never come to my attention before, I don't think I've ever seen it utilized. I've now made a runbook item to disable it. It's a shame that "configuration" includes undoing the fetishes and helpfulness [0][1] of others.

  pam-config -d --env

[0] Crowded elevator atrium. Multiple elevators running. Elevator wants to close, another one is coming (oh! I heard it "ding"!). Somebody is holding the elevator which wants to depart and trying to wave me in. Why doesn't somebody push them out?

[1] I'm at a stop sign. Some complete idiot is trying to turn left onto the street I'm leaving and waving me to turn left in front of them. Fuck no! I turn in front of you, somebody rearends you, you fly forward into me: my fault! You should be able to make this turn, if you can't go around the block! [2]

[2] I could go out of my way and turn right. Or I can just wait and see what happens.

bandrami• 9 months ago

If you need realtime scheduling pam_env was the only way to do it until rtkit came out (and it still does it better than rtkit does, annoyingly).

stackskipton9• 9 months ago

SRE/Sysadmin/DevOps/Whatever here, while blog didn't talk about doing anything difficult but setting ENVVAR standards, I will point out all replacements are just as frustrating especially when talking about secrets.

Anything involving vaults where Application reaches out to specific secret vault like Hashicorp Vault/OpenBao/Secrets Manager quickly becomes massive vendor lock in where replacement is very difficult due to library replacement and makes vault uptime extremely important. This puts Ops in extremely difficult place when it becomes time to upgrade or do maintenance.

Config files have problem of you have secrets, how do you get them into config file since config files are generally kept in public systems? Most of the time it's some form of either "Template replacement by privileged system before handing it to application" or "Entire Config File gets loaded into secret vault and passed into application". Templating can be error prone and loading entire config files into secret manager is frustrating as well since someone could screw up the load.

Speaking of config files, since most systems are running containers, and unless you are at Ops discipline company, these config files are never in the right place, it becomes error prone for Ops to screw up the mounting. Also, whatever format you use, JSON/YAML/TOML is ripe for some weird config file bug to emerge like Norway problem in YAML.

Getting secrets from Kubernetes Secrets API I've seen done but lock in again. I'd strongly not recommend this approach unless you are designing a Kubernetes operator or other such type system.

I will say I've seen Subprocess thing bite people but I've seen less and less subprocess generation these days. Most teams go with message bus type system instead of sub processing since it's more robust and allows independent scaling.

jppittma5• 9 months ago

How is the kubernetes secret API lock in? Genuinely wondering - were you trying to use that deployment yaml for something other than a kubernetes deployment? For most applications, you should be mounting the secret on your application, then you can inject it as either an environment variable or a json file that your application reads in an environment agnostic way.

Then, on the backend, you can configure etcd to use whatever KMS provider you like for encryption.

stackskipton9• 9 months ago

Because you can't run the container, even for development outside Kubernetes.

Yes, you can mount Secrets as Volumes or Env Var in Kubernetes which is fine but I'm not talking about "How you get env var/secret" but "Methods of dealing with config."

171862744011• 9 months ago

You can have a command setting that is invoked to get the string. This way you don't have vendor login, but also don't need a separate template step.

stackskipton9• 9 months ago

You still need to present that to Application.

So Command Line leaks worse than Env Var.

Config file, see original post for problems.

Env Var, see blog for problems.

nunez• 9 months ago

+1 to all of this.

This is why I continue to use env vars and dotenv for configuration. They are extremely simple, work well, and are compatible with secrets managers and other secrets tooling.

Though lately I've been veering into sOps the last few years. YAML is just so nice for expressing how an app should be configured, and sops makes encrypting chunks of it so easy. Dealing with GPG keys can be challenging though, which Vault/OpenBao solve, but then lock-in becomes an issue (though less so with OpenBao).

yukinon• 9 months ago

I am not sure if this considered an anti-pattern, but in one of my teams, we wrote a lightweight generic Secrets library with configurable/pluggable backends (such as AWS Secrets Manager). It had a configurable local cache, with per-parameter overrides to bypass the cache. It meant vendor specific fetch logic was in the pluggable backends, while the app and the secrets lib remained vendor neutral.

When we moved it to Vault, it was seamless. Just meant adding our Vault backend wrapper as a dependency and updating the config to use the Vault backend.

gutafoki• 9 months ago

This is how it should be done. Vendor lock-in can almost always be avoided with proper design

benterix• 9 months ago

Getting secrets from Kubernetes Secrets API I've seen done but lock in again.

I don't get this part. Why would you use Kubernetes secrets alone for storing secrets if they are not encrypted by default? Using k8s secrets only makes sense if (0) you are using k8s, (1) you already did some groundwork like encryption at rest for the control plane, and (2) you are actually using a solution like Secrets Store CSI Driver (or alternatives - just don't depend on k8s secret being actually more secret than a ConfigMap by default).

And then, it's the opposite of lock-in as the Secrets Store CSI Driver uspports multiple backends, including open source Conjur.

jhallenworld2• 9 months ago

Eh, they are just more command line arguments, ones that go on the left side of the command instead of the right. I guess an alternative is something the Windows registry, but I'm not seeing that as a great improvement since it's less direct.

compiler-guy• 9 months ago

Command-line arguments aren't passed to subprocesseses, can't be inspected by arbitrary functions in the same process, and don't leak memory if they are changed.

jhallenworld2• 9 months ago

Yes, I'm just highlighting that it's just as convenient to change them as command line parameters on a per-invocation basis. If there is a proposal for something else, it should retain this capability. Config files and something like the windows registry are much less convenient.

zokier• 9 months ago

can't be inspected by arbitrary functions in the same process

You can not really rely on that. The initial stack layout is well-defined at least on linux, so digging up argv is not difficult. Or just open /proc/self/cmdline

jonny_eh• 9 months ago

I can't recommend Varlock [1] enough. A great way to manage env vars in a project. It lets you define which ones are necessary or optional, their types, and where they should be fetched from.

[1] https://varlock.dev/

esafak2• 9 months ago

I use https://mise.jdx.dev/

peter_d_sherman4• 9 months ago

"Wow, I really enjoyed writing this… …and I hope it wasn’t a boring read."

No, it was very interesting actually!

An excellent deep-dive into the murky area of Unix/Linux environment variables, how they are set, how they are passed, what's really going on behind the scenes.

Basically a must-read for any present or future OS designer...

Observation (if I might!) -- environment variables are to programs (especially chains of programs, parent processes, sub processes and sub-sub processes, etc.) what parameters are to functions -- and/or what command-line parameters are... they're sort of like global variables that get passed around a lot...

They also can influence program behavior -- and thus the determinism of a program -- and thus the determinism of a chain of programs...

Phrased another way -- software that works on one developer's machine might not work on another developer's machine and/or in a production environment because one crucial environment variable was either set or not set, or set to the wrong value...

(NixOS seems to understand this pretty well... that "hermetically sealing" or closing or "performing a closure around" (that's probably slightly the wrong language/terminology in "Nix-speak" but bear with me!) a software environment, including the environment variables is the way to create deterministic software builds that run on any machine... but here I'm digressing...)

But my main point: I complete agree with the article's author -- environment variables are a legacy mess!

Although, if we think about it, environment variables (if we broaden the definition) are a sub-pattern of anything that affects the state of an individual machine or runtime environment -- in other words, things such as the Windows Registry, at least the global aspects of it -- are also in the same category.

Future OS's, when they offer environments for programs or chains of programs to run -- should be completely containerized -- that is, the view of the system -- what data/settings/environment variables/registry variables/files/syscalls/global variables it has access to -- should be completely determinable by the user, completely logabble, completely transparent, and completely able to be compared, one environment to another.

In this way, software that either a) fails to work at all b) works in a non-deterministic way -- can be more easily debugged/diagnosed/fixed (I'm looking at you, future AI's that will assist humans in doing this!) -- then if all of that information is in various different places, broken, and/or opaque...

To reiterate:

"Wow, I really enjoyed writing this… …and I hope it wasn’t a boring read."

No, I really enjoyed reading it(!), it's a brilliant article, and thank you for writing it! :-)

Upvoted and favorited!

chriswarbo4• 9 months ago

environment variables are to programs (especially chains of programs, parent processes, sub processes and sub-sub processes, etc.) what parameters are to functions -- and/or what command-line parameters are... they're sort of like global variables that get passed around a lot...

They're not globals, since they're copied into sub-processes; so mutation doesn't propagate upwards.

My own opinion is that environment variables are dynamically scoped keyword arguments http://www.chriswarbo.net/blog/2021-04-08-env_vars.html

peter_d_sherman4• 9 months ago

They're not globals, since they're copied into sub-processes; so mutation doesn't propagate upwards.

If we broaden our thinking to look at a computer process as a mathematical function, i.e., if we think about a computer process as

y = f(x)

Where y is the behavior of the function (what final state it results in / resolves to), f is the process itself, and x is the parameter or list of parameters that are passed to f, then if that process reads and subsequently alters its behavior in relation to any environment variable, then we should no longer think of that function as merely y = f(x), but as

y = f(x, z)

where Z is the set of environment variables that are consumed by, and subsequently alter the behavior of f, resulting in a different y.

Now not all processes read environment variables and alter their behaviors because of an environment variable being set.

That is true.

Those processes remain as y = f(x).

But if a process does read and does act on an environment variable (usually without the end-users' knowledge, because how many users keep track of which programs read/act on -- which environment variables?), then then this the same as passing extra parameters -- y = f(x, z) -- to the function!

(Sub-observation: A future OS would have an API call to granularly read a single named environment variable at a time (not the entire block of them at once!), and use of this call could be logged and sorted by program, and there would be a user-settable control to granularly determine which environment variables could be read by which programs/processes...)

They're not globals, since they're copied into sub-processes; so mutation doesn't propagate upwards.

Mutation or non-mutation upwards -- is not the issue.

The issue is: If users run program f and they pass it various command line parameters x, and they want y, then if environment variables are present and if they alter the behavior of that program, then what the users are really getting is y = f(x, z), which may not be the behavior/result they want, because z influences the behavior, and is passed in a not-really-all-that-transparent manner (most people usually don't check, log or modify environment variables nor account for them in the determinism of their programs -- unless something is broken...)

Phrased another way -- a future OS would have some way of logging everything, all state information (including environment variables which includes registry settings) -- that go into any given program.

Now maybe environment variables aren't "globals" in the strictest definition...

But let's see...

In most modern operating systems as of 2025, environment variables can easily be read by most programs, functions/procedures/methods inside of those programs, sub-functions/sub-procedures/sub-methods of those programs, etc., etc., etc.

Once they can be read... they can become the state of one or more variables in that program its functions, sub-functions, etc.

And once it can become the state of those one or more internal variables, the program can alter its behavior / result -- based on them.

Global variables -- can do the same exact same thing to a program.

So I'll leave it as a linguistic/semantic debate to future readers, mathematicians, programmers and OS designers -- as to whether or not environment variables (and related globally readable objects such as the Windows Registry) are global variables...

(You are very much correct about environment variables -- if they are mutated (aka written to/overwritten) by by a sub-process, then that mutation doesn't typically propapagate upwards the parent/creator process chain -- but perhaps in the context of my discussion, I am interested/concerned about -- the global readability/accessibility of environment variables... But you are very much correct in your statement!)

I think the key point that I am trying to make is that more transparency/insight/logging could always be had as to where exactly programs get ALL of their inputs from (this includes environment variables, this includes API calls which may differ machine to machine, etc., etc.), and what average end users are made aware of...

alexpotato• 9 months ago

To give an illustration of how bad this can get:

At a past firm, I was trying to debug how a particular ENV var was getting set. I started out thinking it was something simple like the user's .bashrc or equivalent.

I quickly realized that there were roughly 10 "layers" of env var loadings happening where the first couple layers were:

- firm wide

- region

- business unit

- department

- team etc etc

I ended up having to turn on a bash debug flag so that I could see exactly where the var was getting set in the layer stack.

jakub_g• 9 months ago

Not sure if any other high level languages have it, but Node.js has just added command line flags to trace precisely all env var accesses and modifications:

https://nodejs.org/api/cli.html#--trace-env

Since you can set/unset/modify env vars in so many ways with different APIs, this sounds super useful in complex debugging scenarios.

esafak2• 9 months ago

"One namespace ought to be enough for anybody".

pluto_modadic• 9 months ago

static secrets that you can even extract and set in a config file (or store in a secrets manager) need to go. TPM secrets that you can't extract, and public keys that you can pin without considering them "secret", along with Oauth / IAM roles, are the way to go.

quotemstr2• 9 months ago

Environment variables also suck due to having zero typo existence. Write FOO_BAR instead of FOO_BARS? Silent failure. V1 of your package recognizes FOO_BAR and V2 changes it to FOO_BARS (because now we can have more than one)? Silent failure.

sgarland3• 9 months ago

In a shell script, set -u. It’ll terminate if you reference an unset variable.

In other languages, check that the var you pulled in isn’t falsey before proceeding.

quotemstr2• 9 months ago

In a shell script, set -u

Won't help. I'm _running a program_ want to configure it with environment variables, not _writing a program_ that I expect the user to configure for himself.

falsey

There are more than two programming languages in the world.

sureglymop4• 9 months ago

On another note, does anyone know how this blog/website was created? I am in general very curious about ssgs hence why I am asking.

My guess would be either Jekyll or hand rolled, due to the url structure.

julianz• 9 months ago

The RSS feed has an attribute that suggests Hugo.

trzy• 9 months ago

Unix is a legacy mess. The sooner we rid ourselves of this scourge, the better.

Posted from a productive Windows workstation.

scuff3d• 9 months ago

You couldn't pay me enough to go back to doing dev work on Windows.

taejavu• 9 months ago

As if Windows isn’t its own legacy mess..

uzerfcwn• 9 months ago

I feel that Windows Registry is similar legacy cruft as environment variables. Worse yet, most software doesn't document which registry keys it's using, so you have to find them on some ancient forum comment or do the detective work by yourself.

nrvn• 9 months ago

One of the worst things about Environment variables among others discussed here is the implicit and opaque nature of them. Majority of applications rely on them in the *nix world. Even if more explicit and obvious ways of configuration files or remote services (consul/etcd, et al.) and command line arguments are supported env vars are traditionally supported as well.

But as mentioned in the article it is just a global hashmap that can be cloned and extended for child processes. Maybe in 1979 it was a good design decision. Today it sometimes hurts.

For example, kubernetes by default literally pollutes the container’s environment with so-called service links. And you will have fun time debugging a broken application if any of those “default” env vars conflict with the env vars that your app might expect to see.

https://kubernetes.io/docs/tutorials/services/connect-applic...

They are ubiquitous and we are living in the world of neo-conservatism in IT where legacy corner cuts are treated as a standard and never challenged (hello /bin, /usr/bin, /lib, /usr/lib)[0]

[0] https://askubuntu.com/a/135679

oblio2• 9 months ago

Heh, you can put hjkl in that neo conservatism bucket. Vi hjkl are the way they are because of a dumb terminal from 40+ years ago, which had fewer units sold than the Nokia N9 smartphone.

agumonkey• 9 months ago

OP: that wasn't a boring read :) thanks

hei-lima• 9 months ago

Really, really interesting read. I use env vars daily, and it never occurred to me how they actually work. It shows how many things we take for granted have such interesting implementations. :)

ahartmetz• 9 months ago

My favorite environment variable trivium (that's the singular of trivia) is that PS1 and a few others that "everyone" thinks of as environment variables are not environment variables but shell variables. PS1 doesn't even show up in "env" output!

zzbn00• 9 months ago

Many comments here focusing on secrets and problems. But here is another way to look at this:

Environment variables are the "indefinite scope and dynamic extent" variable bindings to make structured programs out of Unix processes. To compare them to a text file is like writing that a program needs no variables because it can read all the values it needs from an input data file when it needs them.

Environment variables are precisely to be used in situation where sub-processes need to be passed information in a way that is not necessarily affecting subsequent calls to that subprocess from another section of a program. Sometime the subprocesses are sequences of nested shells, and sometimes other more complex programs, but the same idea applies.

the_real_cher• 9 months ago

Programmers: Global Variables are bad

Linux admins: Hold my beer

jbverschoor• 9 months ago

Solved in J2EE

Environment variables are a legacy mess: Let's dive deep into them

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