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https://issues.apache.org/jira/browse/SPARK-58658?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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L. C. Hsieh updated SPARK-58658:
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Affects Version/s: 4.3.0
> Do not return spark.connect.authenticate.token from the Config RPC
> ------------------------------------------------------------------
>
> Key: SPARK-58658
> URL: https://issues.apache.org/jira/browse/SPARK-58658
> Project: Spark
> Issue Type: Improvement
> Components: Connect
> Affects Versions: 4.3.0, 5.0.0
> Reporter: L. C. Hsieh
> Priority: Major
>
> The Spark Connect Config RPC hands back any configuration key the session
> holds, including {{spark.connect.authenticate.token}}:
> {code}
> spark.conf.get("spark.connect.authenticate.token") // returns the token
> {code}
> The key reaches the session config because {{SQLConf.mergeSparkConf}} copies
> every {{SparkConf}} entry -- static ones included -- into it, and
> {{SparkConnectConfigHandler}}'s read paths ({{handleGet}},
> {{handleGetOption}}, {{handleGetWithDefault}}, {{handleGetAll}}) apply no
> denylist. {{RuntimeConfig}} guards *writes* to static configs with
> {{requireNonStaticConf}}, but reads are unguarded.
> This is not a vulnerability in the client-to-server deployment Spark itself
> documents: the token is a client credential, and a client that can call the
> Config RPC has already presented it, so reading it back discloses nothing.
> It does matter for deployments that place a proxy in front of Spark Connect
> and reuse this config as a secret shared between the proxy and the servers,
> with end users authenticating to the proxy by other means. There, any user
> the proxy admits can read the token out of a backend and then connect to that
> backend directly, bypassing whatever the proxy enforces. That
> reinterpretation of the config is the deployment's own, not something Spark
> promises -- which is why this is filed as an improvement rather than a
> security issue -- but a server not disclosing its own credential is the
> better default regardless, and it is cheap.
> *Proposed change:* report the key as unset on every read path: {{Get}} and
> {{GetOption}} return no value, {{GetWithDefault}} returns the caller's
> default, and {{GetAll}} omits it. {{Set}}/{{Unset}} already reject it via
> {{requireNonStaticConf}}, and {{IsModifiable}} returns false for a static
> config without disclosing anything.
> Note for anyone implementing this: {{handleGetAll}} strips the requested
> prefix from the keys it returns, so the filter has to run on the full key
> before the prefix is removed.
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