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fix(credentials): fail closed when deriving RPC secret from default credentials (#4402)

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The internode RPC HMAC secret is derived from the S3 credential pair via
`derive_rpc_secret` when `RUSTFS_RPC_SECRET` is unset. The derivation uses the
secret key as the HMAC key, so when the default secret key (`rustfsadmin`) is in
effect the derived RPC secret is a fixed, publicly computable value. Any network
peer can then forge valid `x-rustfs-signature` headers and invoke internode RPC
routes (e.g. `read_file_stream`), bypassing S3 IAM entirely.

`normalize_rpc_secret` already rejected the literal default when it was supplied
directly, but `resolve_rpc_secret` still derived a secret from the default
credential pair. Make the derivation path fail closed: refuse to derive while
the default secret key is in effect, forcing operators to set `RUSTFS_RPC_SECRET`
(or a non-default `RUSTFS_SECRET_KEY`). A default access key paired with a
non-default secret key remains safe and is still allowed.

Addresses GHSA-68cw-96m3-h2cf (incomplete-fix follow-up to CVE-2026-45039).
This commit is contained in:
Zhengchao An
2026-07-08 09:31:25 +08:00
committed by GitHub
parent 0fad356450
commit 7b20554056
1 changed files with 22 additions and 4 deletions
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crates/credentials/src/credentials.rs
+22 -4
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@@ -259,7 +259,18 @@ fn resolve_rpc_secret(env_secret: Option<&str>, global_access: Option<&str>, glo
}
match (global_access, global_secret) {
(Some(access_key), Some(secret_key)) => derive_rpc_secret(access_key, secret_key),
(Some(access_key), Some(secret_key)) => {
// Fail closed: never derive the RPC secret while the default secret
// key is in effect. The derivation uses `secret_key` as the HMAC key,
// so a public default secret yields a publicly computable RPC secret
// that any network peer can use to forge internode RPC signatures.
// Operators running with default credentials must configure
// RUSTFS_RPC_SECRET (or set a non-default RUSTFS_SECRET_KEY) instead.
if secret_key.trim() == DEFAULT_SECRET_KEY {
return None;
}
derive_rpc_secret(access_key, secret_key)
}
_ => None,
}
}
@@ -575,12 +586,19 @@ mod tests {
}
#[test]
fn test_resolve_rpc_secret_allows_default_credentials_for_derivation() {
fn test_resolve_rpc_secret_rejects_default_credentials_for_derivation() {
assert!(resolve_rpc_secret(None, None, None).is_none());
let expected = derive_rpc_secret(DEFAULT_ACCESS_KEY, DEFAULT_SECRET_KEY).expect("secret should derive");
// Fail closed: the default secret key must not yield a derivable RPC
// secret, otherwise the derived value is publicly computable and any
// network peer can forge internode RPC signatures.
assert!(resolve_rpc_secret(None, Some(DEFAULT_ACCESS_KEY), Some(DEFAULT_SECRET_KEY)).is_none());
// A default access key paired with a non-default secret key is still
// safe to derive: the HMAC key (the secret key) is not public.
let expected = derive_rpc_secret(DEFAULT_ACCESS_KEY, "custom-global-secret").expect("secret should derive");
assert_eq!(
resolve_rpc_secret(None, Some(DEFAULT_ACCESS_KEY), Some(DEFAULT_SECRET_KEY)).as_deref(),
resolve_rpc_secret(None, Some(DEFAULT_ACCESS_KEY), Some("custom-global-secret")).as_deref(),
Some(expected.as_str())
);