[seaweedfs] Fix drift for security config (#1193)

Signed-off-by: Andrei Kvapil <kvapss@gmail.com>

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upstream issue: https://github.com/seaweedfs/seaweedfs/pull/6967

## What this PR does


### Release note

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```release-note
[seaweedfs] Fix drift for security config
```

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

* **Bug Fixes**
* Ensured JWT signing keys in the SeaweedFS security configuration
remain consistent across Helm upgrades, preventing unintentional key
rotation and maintaining stable authentication.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

packages/system/seaweedfs/charts/seaweedfs/templates/security-configmap.yaml

@@ -10,6 +10,8 @@ metadata:
     app.kubernetes.io/managed-by: {{ .Release.Service }}
     app.kubernetes.io/instance: {{ .Release.Name }}
 data:
+  {{- $existing := (lookup "v1" "ConfigMap" .Release.Namespace (printf "%s-security-config" (include "seaweedfs.name" .))) }}
+  {{- $securityConfig := fromToml (dig "data" "security.toml" "" $existing) }}
   security.toml: |-
     # this file is read by master, volume server, and filer
 
@@ -17,7 +19,7 @@ data:
     # the jwt signing key is read by master and volume server
     # a jwt expires in 10 seconds
     [jwt.signing]
-    key = "{{ randAlphaNum 10 | b64enc }}"
+    key = "{{ dig "jwt" "signing" "key" (randAlphaNum 10 | b64enc) $securityConfig }}"
     {{- end }}
 
     {{- if .Values.global.securityConfig.jwtSigning.volumeRead }}
@@ -25,7 +27,7 @@ data:
     # - the Master server generates the JWT, which can be used to read a certain file on a volume server
     # - the Volume server validates the JWT on reading
     [jwt.signing.read]
-    key = "{{ randAlphaNum 10 | b64enc }}"
+    key = "{{ dig "jwt" "signing" "read" "key" (randAlphaNum 10 | b64enc) $securityConfig }}"
     {{- end }}
 
     {{- if .Values.global.securityConfig.jwtSigning.filerWrite }}
@@ -34,7 +36,7 @@ data:
     # - the Filer server validates the JWT on writing
     # the jwt defaults to expire after 10 seconds.
     [jwt.filer_signing]
-    key = "{{ randAlphaNum 10 | b64enc }}"
+    key = "{{ dig "jwt" "filer_signing" "key" (randAlphaNum 10 | b64enc) $securityConfig }}"
     {{- end }}
 
     {{- if .Values.global.securityConfig.jwtSigning.filerRead }}
@@ -43,7 +45,7 @@ data:
     # - the Filer server validates the JWT on writing
     # the jwt defaults to expire after 10 seconds.
     [jwt.filer_signing.read]
-    key = "{{ randAlphaNum 10 | b64enc }}"
+    key = "{{ dig "jwt" "filer_signing" "read" "key" (randAlphaNum 10 | b64enc) $securityConfig }}"
     {{- end }}
 
     # all grpc tls authentications are mutual