s3: strip internal metadata headers on auth entry (#11850)

* s3: strip internal object-lock and version headers on auth entry

putToFiler persists Seaweed-X-Amz-Object-Lock-Mode, -Retention-Until-Date,
-Legal-Hold and -Version-Id request headers into authoritative entry
metadata without a permission check, so an s3:PutObject-only writer could
pin COMPLIANCE retention and legal hold on its own uploads, bypassing the
dedicated-permission gate on the standard x-amz-object-lock-* headers.
The server only sets these headers from validated inputs, so drop them in
authenticateRequestInternal alongside the identity headers already
scrubbed there.

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

* s3: strip internal SSE headers on auth entry

X-SeaweedFS-SSE-S3-Key-Data, -SSE-S3-Base-IV and -SSE-KMS-Base-IV are read
from the request to drive multipart encryption, so a client could inject
its own key material and IVs. The server sets them itself between handler
stages of a request; drop inbound values in authenticateRequestInternal.

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

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

* s3: scrub internal headers before the auth-enabled early return

Auth and AuthPostPolicy skip authenticateRequestInternal when IAM is
disabled, so client-supplied internal headers still reached putToFiler.
Hoist the scrub into scrubInternalHeaders and run it unconditionally in
both wrappers as well as the shared auth entry point.

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

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

* s3: test internal header scrub through the auth-disabled wrapper

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

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

---------

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

weed/s3api/s3api_object_lock_actions_authz_test.go

@@ -227,3 +227,67 @@ func TestObjectLockActionsRoundTrip(t *testing.T) {
 		})
 	}
 }
+
+// Internal Seaweed-X-Amz-* headers carry server-validated object lock values
+// into entry metadata; client-supplied ones must be dropped on entry or the
+// dedicated-permission check on x-amz-object-lock-* is bypassed.
+func TestInternalObjectLockHeadersStrippedOnAuth(t *testing.T) {
+	iam := newTestIAM()
+
+	internal := []string{
+		s3_constants.ExtObjectLockModeKey,
+		s3_constants.ExtRetentionUntilDateKey,
+		s3_constants.ExtLegalHoldKey,
+		s3_constants.ExtVersionIdKey,
+		s3_constants.SeaweedFSSSEKMSBaseIVHeader,
+		s3_constants.SeaweedFSSSES3BaseIVHeader,
+		s3_constants.SeaweedFSSSES3KeyDataHeader,
+	}
+	req := httptest.NewRequest(http.MethodPut, "http://localhost:8333/worm/doc.txt", nil)
+	for _, k := range internal {
+		req.Header.Set(k, "injected")
+	}
+	require.NoError(t, signRawHTTPRequest(context.Background(), req,
+		"AKIAIOSFODNN7EXAMPLE", "wJalrXUtnFEMI/K7MDENG/bPxRfiCYEXAMPLEKEY", "us-east-1"))
+
+	_, _, _ = iam.authenticateRequestInternal(req)
+
+	for _, k := range internal {
+		if got := req.Header.Get(k); got != "" {
+			t.Errorf("client-supplied %s survived authentication: %q", k, got)
+		}
+	}
+}
+
+// With IAM disabled the Auth wrapper calls the handler directly; internal
+// headers must still be stripped so they never reach putToFiler.
+func TestInternalHeadersStrippedWithoutAuth(t *testing.T) {
+	iam := &IdentityAccessManagement{}
+
+	internal := []string{
+		s3_constants.ExtObjectLockModeKey,
+		s3_constants.ExtRetentionUntilDateKey,
+		s3_constants.ExtLegalHoldKey,
+		s3_constants.ExtVersionIdKey,
+		s3_constants.SeaweedFSSSEKMSBaseIVHeader,
+		s3_constants.SeaweedFSSSES3BaseIVHeader,
+		s3_constants.SeaweedFSSSES3KeyDataHeader,
+	}
+	var leaked []string
+	handler := iam.Auth(func(w http.ResponseWriter, r *http.Request) {
+		for _, k := range internal {
+			if v := r.Header.Get(k); v != "" {
+				leaked = append(leaked, k)
+			}
+		}
+	}, s3_constants.ACTION_WRITE)
+
+	req := httptest.NewRequest(http.MethodPut, "http://localhost:8333/worm/doc.txt", nil)
+	for _, k := range internal {
+		req.Header.Set(k, "injected")
+	}
+	handler(httptest.NewRecorder(), req)
+	if len(leaked) > 0 {
+		t.Errorf("client-supplied internal headers reached handler with auth disabled: %v", leaked)
+	}
+}