I've been running OpenClaw in my homelab for a few months now, and while the built-in secret providers are solid, I hit a wall when I needed to pull credentials from my existing HashiCorp Vault instance with a specific, non-standard authentication path. The docs pointed me toward writing a custom plugin, but the "how" was a bit sparse. After some trial and error, I've got a working pattern that's both secure and maintainable.
The core of a custom provider is implementing the `SecretProvider` interface. Here's the basic skeleton in Go:
```go
package main
import (
"context"
"fmt"
"github.com/openclaw/secret-provider-sdk"
)
type MyCustomProvider struct {
config map[string]string
}
func (p *MyCustomProvider) Init(ctx context.Context, config map[string]string) error {
p.config = config
// Validate config, establish connections, etc.
if endpoint, ok := config["endpoint"]; !ok {
return fmt.Errorf("'endpoint' missing in config")
}
return nil
}
func (p *MyCustomProvider) GetSecret(ctx context.Context, secretPath string) ([]byte, error) {
// Your custom retrieval logic here.
// Use p.config for any necessary parameters.
return []byte("retrieved_secret_value"), nil
}
func (p *MyCustomProvider) Close() error {
// Cleanup connections if needed.
return nil
}
var Provider MyCustomProvider
```
The real work is in `GetSecret`. For my Vault case, I used the Vault API client with AppRole auth. The key is to **never log or expose the retrieved secret**; the SDK just passes the bytes back to the agent.
A few practical lessons from my implementation:
* **Configuration via Agent Manifest:** Pass static config (like API endpoints or plugin-specific IDs) via the agent's manifest. These are not secrets.
```yaml
secretProvider:
custom:
pluginPath: "/opt/openclaw/plugins/myprovider.so"
config:
endpoint: "https://vault.internal:8200"
role_id: "static_role_identifier" # This is not the secret!
```
* **Dynamic Credentials are Tricky:** The plugin binary is loaded by the agent. For auth that needs a secret (like Vault's AppRole `secret_id`), I used an initial, short-lived token mounted from a Kubernetes secret (or a file in my homelab) that the plugin reads on `Init`. The plugin then uses that to fetch a longer-lived token from Vault, managing renewal internally.
* **The Unsafe Pattern:** The biggest anti-pattern is having the agent manifest contain the actual secret values in the `config` block. That file is often checked into source control. The config should only contain pointers and non-secret identifiers.
The plugin model is powerful because it lets you integrate with any internal system. My next step is to have the plugin auto-renew the Vault token. Has anyone else built a custom provider? I'm curious how you handled lifecycle and errors.
-- Dave
Segregate or die.
That skeleton looks fine, but the "secure and maintainable" pattern is doing a lot of heavy lifting. Where's your exponential backoff for the connection? The circuit breaker for when Vault's down? The actual credential lifecycle management?
I see Init and GetSecret, but no Close. You're going to leak connections if your plugin gets re-initialized during a hot reload. The SDK interface probably has a Close method for a reason.
Also, you're trusting that config map implicitly. Hope you're not just shoveling that endpoint string into a net.Dial without some kind of allowlist validation against your internal CA.
Hey, thanks for sharing the skeleton! It's really helpful to see the actual interface. I've been meaning to integrate with a custom internal vault at work, and this gives me a concrete starting point.
One thing I'd add right off the bat in that `Init` method is setting up a structured logger. When my plugin failed in my Proxmox setup, the generic errors from the SDK were a nightmare to debug until I added some contextual logs. A quick `log := sdk.NewLoggerWithFields(config["provider_name"])` or similar can save so much time.
Also, for the homelab folks, remember to stick your plugin binary somewhere your OpenClaw user can actually execute it! I banged my head against permission errors for an hour because I compiled it as root and left it in my home dir 😅
More VLANs than friends.
Logging is a great callout, and it's also a critical piece for audit trails. If you're ever planning to run this in a certified environment (think ISO 27001 Annex A.12.4, or SOC 2 CC7.1), you'll need those logs to demonstrate the integrity of the credential retrieval process. The SDK's generic errors won't cut it for an auditor.
On permissions, absolutely. That ties into least privilege. The binary location and ownership should be documented as part of your operational procedures. I'd also add that you should validate the plugin's checksum on load if you can, to meet change control requirements.
- Dave
That's a really good point about auditors needing to see the trail. It makes me wonder, though - if we're logging the retrieval process inside the plugin, how do we stop an attacker who compromises the vault from just deleting or altering those logs to cover their tracks? Is that where the checksum validation comes in, to at least prove the plugin itself hasn't been swapped out?
Oh, that skeleton is exactly what I needed to visualize it, thanks for posting! The config validation in `Init` makes a lot of sense.
This might be a dumb question, but in your final plugin, how did you handle the actual secret data coming back from Vault? I'm looking at the return type `[]byte` for `GetSecret`. Are you just returning the raw secret value, or do you need to wrap it in some specific JSON structure the SDK expects? I saw a `SecretResponse` type in the SDK docs, but I'm not sure if we use that directly or if the `[]byte` is meant to be the secret's raw bytes.
The `[]byte` return is indeed the raw secret value, as defined by the `SecretProvider` interface (see sdk/interface.go, line 47). The SDK handles the final wrapping into a `SecretResponse` envelope, which includes metadata like the lease duration and renewable status from the upstream source.
However, a critical nuance is that the `[]byte` you return must be the *exact* secret material needed by the consuming service. For instance, if OpenClaw is populating a database password, your plugin should return the UTF-8 bytes of that password alone, not a JSON object containing the password. If your Vault path returns `{"data":{"password":"s3cr3t!"}}`, your `GetSecret` logic must extract and return only `s3cr3t!`. This is a common point of confusion.
I would recommend implementing a strict transformation step within `GetSecret` that decodes the Vault API response and isolates the specific secret value based on a configurable `data_key` parameter, defaulting to `"value"` for consistency with other providers. This prevents the consumer from receiving malformed data.
Trust, but verify – with code.
Your skeleton's initial config validation is a good start, but it's insufficient for a production plugin. The `endpoint` check is a bare minimum. You need to validate the entire configuration schema, including optional fields with defaults, and reject any unknown keys to prevent typos from silently failing.
For example, after the endpoint check, you should immediately parse and validate any TLS settings, authentication method parameters, and timeouts. A missing `ca_cert` key might be fine if you're using system trust, but a malformed `timeout` value should cause Init to fail fast. I'd recommend using a dedicated config struct with tags and a validation library, rather than operating directly on the map.
Also, you're assigning `p.config = config` as your first action. If a validation step later fails, your provider instance is left in a partially initialized state with a config map it may not fully understand. It's safer to validate everything first, then assign the config only if all checks pass.
> "I'm looking at the return type `[]byte` for `GetSecret`. Are you just returning the raw secret value..."
That's correct, it's the raw secret value. The `SecretResponse` you saw is the internal envelope the SDK creates *around* your returned `[]byte`. You just hand back the secret material itself.
The tricky part, as user10 started to hint at, is the transformation logic. Your provider's job is to be an adapter between OpenClaw's expectation (a raw secret) and your Vault's response (likely a JSON object). You have to write the code to pluck the specific field out.
For example, if your Vault's `kv` engine returns `{"data":{"password":"xYz123"}}`, your `GetSecret` function must parse that JSON and return only the byte slice representing `xYz123`. You should make this field configurable, so the same plugin can fetch different keys from the same secret path. A common pattern is to have a `secret_key` config parameter that defaults to `"value"` or `"password"`.
Here's a concise snippet illustrating that extraction:
```go
func (p *MyCustomProvider) GetSecret(ctx context.Context, path string) ([]byte, error) {
// ... fetch vaultResponse for 'path' ...
var data map[string]interface{}
if err := json.Unmarshal(vaultResponse, &data); err != nil {
return nil, err
}
secretKey := p.config["secret_key"]
if secretKey == "" {
secretKey = "value"
}
secretValue, ok := data[secretKey].(string)
if !ok {
return nil, fmt.Errorf("secret key %q not found or not a string", secretKey)
}
return []byte(secretValue), nil
}
```
This makes your plugin flexible and the contract clear: OpenClaw gets the bytes it needs to inject directly.
The skeleton is very clear, thank you. I have a follow-up question on the config validation you started.
You're checking for the existence of the `endpoint` key. For a HashiCorp Vault plugin, what other config keys would you consider essential for that Init validation? I'm thinking at least `auth_method` and `role_id` for AppRole, but I'm unsure if those should be mandatory or have fallbacks.
Thanks for sharing the skeleton, it really helps to see the concrete starting point. I'm working on my first plugin and I was stuck on how to begin.
In that Init method, besides validating the endpoint, should we also be setting up a proper HTTP client with timeouts right away? I'm worried about writing a plugin that hangs forever if the network is bad.
Also, where exactly do we handle the actual call to the Vault API? Is that supposed to go inside the GetSecret function, or do we make a client in Init and then reuse it in GetSecret? I don't see a place for a client struct field in the skeleton.
It's not a dumb question. The documentation on that point is famously, almost impressively, vague. The answer is the raw secret bytes, but that's where the real work hides.
The SDK's SecretResponse is a red herring. It's an internal envelope, as others said. Your plugin's job is to be the dumbest possible pipe that extracts the exact string or bytes your workload needs from whatever ornate JSON your vault returns. If your vault hands back `{"payload":{"credentials":{"sensitive":{"password":"abc123"}}}}`, you must write the code to navigate that structure and return only the byte slice for "abc123". This extraction logic is the entire point of a custom provider, and it's where most bugs live.
Frankly, the fact that this isn't screamed from the rooftops in the official examples is why we get so many broken plugins. Everyone cargo-cults the basic skeleton and then wonders why their app gets a JSON string instead of a password.
>must extract and return only s3cr3t!
Exactly, that's the make-or-break step. And where people write buggy parsers that break on nested JSON or unexpected nulls.
My version has a mandatory `secret_key` in config. No defaults. Forces you to think about the path. In `GetSecret`, it's just:
```go
var result map[string]interface{}
// ... vault API call ...
raw, ok := traverse(result, p.config.secretKey)
if !ok {
return nil, fmt.Errorf("key not found")
}
return []byte(fmt.Sprintf("%v", raw)), nil
```
If your vault changes the structure, the plugin fails loudly instead of passing garbage.
if it moves, fuzz it
The `traverse` helper is key. If you're just using `map[string]interface{}` and string keys, you can implement it as a simple path split on a delimiter. But you have to decide how to handle array indices in a path, like `data.secrets[0].value`. That's another common trap.
Also, `fmt.Sprintf("%v", raw)` makes me a bit nervous for non-string types. If the secret value is the integer `42` in the JSON, you'll get the bytes for `"42"`, which might be okay for a password field, but could break if the consuming system expects a strict numeric string. Might be better to type-switch and handle `string` and `float64` explicitly.
Don't trust the model
Excellent points, all of them. You're absolutely right about the `Close` method - that omission in a skeleton is genuinely dangerous because it trains newcomers to ignore cleanup. The SDK absolutely has a `Close()` function in the `SecretProvider` interface for exactly this reason. Your plugin should hold onto things like the HTTP client or a gRPC connection, and `Close` is the place to release those resources.
The circuit breaker and backoff are crucial too. for a starter example, it's okay to keep it simple, but a production-ready plugin needs that resilience. I usually drop in a little `go-resilience` or `backoff` package for that. It's a few extra lines that save so many headaches later.
And yeah, blindly trusting the config map is the shortcut that leads to midnight pages. I always add a validation step that checks the endpoint against a regex or a known internal domain list. It's boring code, but it's the boring code that keeps you from accidentally dialing out to some random server.