security: fail closed on gRPC TLS errors, verify dialed server identity (#12263)

* security: fail closed on misconfigured gRPC TLS

LoadServerTLS/LoadClientTLS returned plaintext credentials on every
error path once TLS was configured: a typo in tls.min_version or
tls.cipher_suites, cert and key in different directories, or cert/key
set without grpc.ca all left the component serving or dialing
plaintext. A partially configured TLS setup now stops the process at
startup instead; leaving cert/key unset still means no TLS, as before.

The loaders also stat cert/key/ca files up front since the pemfile
providers read lazily and would otherwise only fail at handshake time.

Mirrored in the Rust volume server: partial grpc.volume cert/key, a
missing grpc.ca, or a rustls build failure now abort startup rather
than warn-and-continue on plaintext.

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Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

* security: optional server-identity allowlist for gRPC clients

The mTLS client accepts any certificate the configured CA signs, so a
per-workload CA lets one component stand in for any other: a filer
identity can answer as the master. The server side already screens
callers via allowed_commonNames and allowed_wildcard_domain; nothing
screened the server.

LoadClientTLS now wires AdditionalPeerVerification when the caller
configures a server allowlist: grpc.<component>.allowed_server_commonNames
(falling back to a shared grpc.allowed_server_commonNames) matched
against the peer cert's subject CN, DNS SANs, or URI SANs such as a
SPIFFE id, plus a grpc.allowed_server_wildcard_domain suffix match.
Leaving them unset keeps the previous behavior.

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Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

* security: URI SANs are exact-match only in the server identity allowlist

A URI identity whose path happens to end in the wildcard domain would
otherwise pass the DNS suffix check.

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Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

* security: tighten gRPC TLS fail-closed and server-identity paths

- URI SANs match the server-identity allowlist exactly; the wildcard
  domain suffix check applies only to CN and DNS SANs.
- A partially set client_cert/client_key pair is an error when the
  cert/key fallback is empty, instead of dialing plaintext.
- Cert/key/ca files are loaded and parsed at startup (LoadX509KeyPair
  and CA PEM validation) since pemfile providers read lazily.

Generated with [Devin](https://devin.ai)

Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

* rust volume: error on a partial grpc client_cert/client_key pair

Mirror the Go loadClientTLS path: when client_cert or client_key is
set without its mate and the cert/key fallback is empty, fail instead
of dialing plaintext.

Generated with [Devin](https://devin.ai)

Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

* security: wildcard domain match requires a valid hostname

A CA-signed identity like ".example.com" satisfied the bare suffix check
for wildcard ".example.com" despite not being a hostname. Require a real
subdomain: non-empty label before the suffix, a '.' boundary when the
configured wildcard has no leading dot, and DNS-name syntax. A leading
"*." label still matches so wildcard certs keep working. Applied to both
the Go server/client authenticators and the Rust volume's client-cert
verifier.

* security: ignore a trailing root dot in wildcard domain matching

* tls: reject a partial dedicated client cert/key pair instead of falling back

When exactly one of component.client_cert/client_key is set, warn-and-
fallback silently dialed with the serving identity. Fail closed like the
other TLS misconfigurations in this change; mirrored in the Rust loader.
Regression tests cover a partial pair with a valid fallback.

* rust volume: harden partial client cert pair test with real pem files

* security: verify dialed server identity per target kind on the filer

The filer reused one grpc.filer-verifying dial option for master, volume,
filer and s3 targets, so a broad allowlist accepted the wrong component at
the wrong port and a narrow one rejected legitimate peers. Outbound calls
now pick grpc.<target>.allowed_server_commonNames (falling back to the
client component's and the global list) while still presenting the
grpc.filer client identity.

* security: scope per-target server allowlists under the client component

The filer read grpc.volume.allowed_server_commonNames when dialing a
volume, but that key already denotes the volume's own outbound allowlist
(e.g. the master identity). A deployment restricting volume->master
calls would make the filer reject real volume servers. Per-target policy
now lives under the client component: grpc.filer.volume_*
falls back to grpc.filer.* then grpc.*.

---------

Co-authored-by: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

seaweed-volume/src/security/tls.rs

@@ -363,8 +363,51 @@ fn common_name_is_allowed(
     allowed_common_names: &HashSet<String>,
     allowed_wildcard_domain: &str,
 ) -> bool {
-    (!allowed_wildcard_domain.is_empty() && common_name.ends_with(allowed_wildcard_domain))
-        || allowed_common_names.contains(common_name)
+    allowed_common_names.contains(common_name)
+        || wildcard_domain_matches(common_name, allowed_wildcard_domain)
+}
+
+// Mirrors the Go wildcard check: the name must end with the domain, carry a
+// non-empty label in front of it, and be a valid DNS name so a CA-signed name
+// like ".example.com" cannot satisfy the suffix check. A leading "*." label
+// is allowed so wildcard certs keep matching. One trailing root dot is
+// ignored on both sides so absolute DNS names still match.
+fn wildcard_domain_matches(name: &str, wildcard_domain: &str) -> bool {
+    let name = name.strip_suffix('.').unwrap_or(name);
+    let wildcard_domain = wildcard_domain.strip_suffix('.').unwrap_or(wildcard_domain);
+    if wildcard_domain.is_empty()
+        || name.len() <= wildcard_domain.len()
+        || !name.ends_with(wildcard_domain)
+    {
+        return false;
+    }
+    if !wildcard_domain.starts_with('.')
+        && name.as_bytes()[name.len() - wildcard_domain.len() - 1] != b'.'
+    {
+        return false;
+    }
+    is_domain_name(name.strip_prefix("*.").unwrap_or(name))
+}
+
+// Mirrors Go's net.IsDomainName: non-empty labels of letters, digits, '-',
+// '_', each up to 63 chars and not '-'-edged, with at least one non-digit so
+// a bare IP cannot pass a domain wildcard.
+fn is_domain_name(name: &str) -> bool {
+    if name.is_empty() || name.len() > 253 {
+        return false;
+    }
+    let mut non_numeric = false;
+    let valid = name.split('.').all(|label| {
+        non_numeric |= label.bytes().any(|c| !c.is_ascii_digit());
+        !label.is_empty()
+            && label.len() <= 63
+            && !label.starts_with('-')
+            && !label.ends_with('-')
+            && label
+                .bytes()
+                .all(|c| c.is_ascii_alphanumeric() || c == b'-' || c == b'_')
+    });
+    valid && non_numeric
 }
 
 fn go_tls_version_for_supported(version: &SupportedProtocolVersion) -> GoTlsVersion {
@@ -436,10 +479,50 @@ mod tests {
             &allowed_common_names,
             ".example.com",
         ));
+        assert!(common_name_is_allowed(
+            "node.example.com.",
+            &allowed_common_names,
+            ".example.com",
+        ));
+        assert!(common_name_is_allowed(
+            "node.example.com.",
+            &allowed_common_names,
+            ".example.com.",
+        ));
+        assert!(!common_name_is_allowed(
+            "node.example.com..",
+            &allowed_common_names,
+            ".example.com",
+        ));
+        assert!(!common_name_is_allowed(
+            "node..example.com.",
+            &allowed_common_names,
+            ".example.com",
+        ));
         assert!(!common_name_is_allowed(
             "node.prod.other.net",
             &allowed_common_names,
             ".example.com",
         ));
+        assert!(!common_name_is_allowed(
+            ".example.com",
+            &allowed_common_names,
+            ".example.com",
+        ));
+        assert!(!common_name_is_allowed(
+            "node..example.com",
+            &allowed_common_names,
+            ".example.com",
+        ));
+        assert!(!common_name_is_allowed(
+            "badexample.com",
+            &allowed_common_names,
+            "example.com",
+        ));
+        assert!(common_name_is_allowed(
+            "*.example.com",
+            &allowed_common_names,
+            ".example.com",
+        ));
     }
 }