fix: Don't allow uppercase characters in Kubernetes object names (#1095)

xeniape · siegfriedweber · web-flow · commit 1c057358b707 · 2025-09-22T07:15:28.000Z
* fix: separate between official and kubernetes-native RFC 1123 definition

* add changelog entry

* subdomain format also kubernetes-specific

* adjust variable names and add docs, fix changelog

* rename functions

* fix links in docs

* make const public

* Update crates/stackable-operator/src/validation.rs

Co-authored-by: Siegfried Weber &lt;mail@siegfriedweber.net&gt;

* Update crates/stackable-operator/src/validation.rs

Co-authored-by: Siegfried Weber &lt;mail@siegfriedweber.net&gt;

* clarify comment

---------

Co-authored-by: Siegfried Weber &lt;mail@siegfriedweber.net&gt;
diff --git a/crates/stackable-operator/CHANGELOG.md b/crates/stackable-operator/CHANGELOG.md
@@ -12,8 +12,13 @@ All notable changes to this project will be documented in this file.
 
 - BREAKING: Upgrade to `schemars` 1.0, `kube` 2.0 and `k8s-openapi` 0.26 (using Kubernetes 1.34) ([#1091]).
 
+### Fixed
+
+- BREAKING: Don't allow uppercase characters in Kubernetes object names ([#1095]).
+
 [#1091]: https://github.com/stackabletech/operator-rs/pull/1091
 [#1094]: https://github.com/stackabletech/operator-rs/pull/1094
+[#1095]: https://github.com/stackabletech/operator-rs/pull/1095
 
 ## [0.97.0] - 2025-09-09
 
diff --git a/crates/stackable-operator/src/builder/pod/container.rs b/crates/stackable-operator/src/builder/pod/container.rs
@@ -12,7 +12,7 @@ use {k8s_openapi::api::core::v1::PodSpec, std::collections::BTreeMap};
 
 use crate::{
     commons::product_image_selection::ResolvedProductImage,
-    validation::{self, is_rfc_1123_label},
+    validation::{self, is_lowercase_rfc_1123_label},
 };
 
 type Result<T, E = Error> = std::result::Result<T, E>;
@@ -351,10 +351,11 @@ impl ContainerBuilder {
         }
     }
 
-    /// Validates a container name is according to the [RFC 1123](https://www.ietf.org/rfc/rfc1123.txt) standard.
+    /// Validates a container name is according to the kubernetes-specific [RFC 1123](https://kubernetes.io/docs/concepts/overview/working-with-objects/names/#dns-label-names) standard.
     /// Returns [Ok] if the name is according to the standard, and [Err] if not.
     fn validate_container_name(container_name: &str) -> Result<()> {
-        is_rfc_1123_label(container_name).context(InvalidContainerNameSnafu { container_name })
+        is_lowercase_rfc_1123_label(container_name)
+            .context(InvalidContainerNameSnafu { container_name })
     }
 }
 
@@ -441,7 +442,7 @@ mod tests {
             resources::ResourceRequirementsBuilder,
         },
         commons::resources::ResourceRequirementsType,
-        validation::RFC_1123_LABEL_FMT,
+        validation::LOWERCASE_RFC_1123_LABEL_FMT,
     };
 
     #[test]
@@ -604,11 +605,11 @@ mod tests {
         assert!(ContainerBuilder::new("name-with-hyphen").is_ok());
         assert_container_builder_err(
             ContainerBuilder::new("ends-with-hyphen-"),
-            &format!(r#"regex used for validation is "{RFC_1123_LABEL_FMT}""#),
+            &format!(r#"regex used for validation is "{LOWERCASE_RFC_1123_LABEL_FMT}""#),
         );
         assert_container_builder_err(
             ContainerBuilder::new("-starts-with-hyphen"),
-            &format!(r#"regex used for validation is "{RFC_1123_LABEL_FMT}""#),
+            &format!(r#"regex used for validation is "{LOWERCASE_RFC_1123_LABEL_FMT}""#),
         );
     }
 
@@ -623,7 +624,7 @@ mod tests {
         assert_container_builder_err(
             ContainerBuilder::new("name_name"),
             &format!(
-                r#"(e.g. "example-label", or "1-label-1", regex used for validation is "{RFC_1123_LABEL_FMT}""#
+                r#"(e.g. "example-label", or "1-label-1", regex used for validation is "{LOWERCASE_RFC_1123_LABEL_FMT}""#
             ),
         );
     }
diff --git a/crates/stackable-operator/src/validation.rs b/crates/stackable-operator/src/validation.rs
@@ -16,27 +16,38 @@ use regex::Regex;
 use snafu::Snafu;
 
 /// Minimal length required by RFC 1123 is 63. Up to 255 allowed, unsupported by k8s.
-const RFC_1123_LABEL_MAX_LENGTH: usize = 63;
-pub const RFC_1123_LABEL_FMT: &str = "[a-zA-Z0-9]([-a-zA-Z0-9]*[a-zA-Z0-9])?";
-const RFC_1123_LABEL_ERROR_MSG: &str = "a RFC 1123 label must consist of alphanumeric characters, '-' or '.', and must start and end with an alphanumeric character";
+pub const RFC_1123_LABEL_MAX_LENGTH: usize = 63;
+// This is a modified RFC 1123 format according to the Kubernetes specification, see https://kubernetes.io/docs/concepts/overview/working-with-objects/names/#dns-label-names
+pub const LOWERCASE_RFC_1123_LABEL_FMT: &str = "[a-z0-9]([-a-z0-9]*[a-z0-9])?";
+const LOWERCASE_RFC_1123_LABEL_ERROR_MSG: &str = "a lowercase RFC 1123 label must consist of lower case alphanumeric characters or '-', and must start and end with an alphanumeric character";
 
-/// This is a subdomain's max length in DNS (RFC 1123)
-const RFC_1123_SUBDOMAIN_MAX_LENGTH: usize = 253;
-const RFC_1123_SUBDOMAIN_FMT: &str =
-    concatcp!(RFC_1123_LABEL_FMT, "(\\.", RFC_1123_LABEL_FMT, ")*");
+// This is a RFC 1123 format, see https://www.rfc-editor.org/rfc/rfc1123
+const RFC_1123_LABEL_FMT: &str = "[a-zA-Z0-9]([-a-zA-Z0-9]*[a-zA-Z0-9])?";
 
-const DOMAIN_MAX_LENGTH: usize = RFC_1123_SUBDOMAIN_MAX_LENGTH;
-/// Same as [`RFC_1123_SUBDOMAIN_FMT`], but allows a trailing dot
-const DOMAIN_FMT: &str = concatcp!(RFC_1123_SUBDOMAIN_FMT, "\\.?");
+/// This is a subdomain's max length in DNS (RFC 1123)
+pub const RFC_1123_SUBDOMAIN_MAX_LENGTH: usize = 253;
+pub const LOWERCASE_RFC_1123_SUBDOMAIN_FMT: &str = concatcp!(
+    LOWERCASE_RFC_1123_LABEL_FMT,
+    "(\\.",
+    LOWERCASE_RFC_1123_LABEL_FMT,
+    ")*"
+);
+const LOWERCASE_RFC_1123_SUBDOMAIN_ERROR_MSG: &str = "a lowercase RFC 1123 subdomain must consist of lower case alphanumeric characters, '-' or '.', and must start and end with an alphanumeric character";
+
+pub const DOMAIN_MAX_LENGTH: usize = RFC_1123_SUBDOMAIN_MAX_LENGTH;
+
+/// String of one or multiple [`RFC_1123_LABEL_FMT`] separated by dots but also allowing a trailing dot
+const DOMAIN_FMT: &str = concatcp!(RFC_1123_LABEL_FMT, "(\\.", RFC_1123_LABEL_FMT, ")*\\.?");
 const DOMAIN_ERROR_MSG: &str = "a domain must consist of alphanumeric characters, '-' or '.', and must start with an alphanumeric character and end with an alphanumeric character or '.'";
 
 // FIXME: According to https://www.rfc-editor.org/rfc/rfc1035#section-2.3.1 domain names must start with a letter
 // (and not a number).
-const RFC_1035_LABEL_FMT: &str = "[a-z]([-a-z0-9]*[a-z0-9])?";
-const RFC_1035_LABEL_ERROR_MSG: &str = "a DNS-1035 label must consist of lower case alphanumeric characters or '-', start with an alphabetic character, and end with an alphanumeric character";
+// This is a modified RFC 1035 format according to the Kubernetes specification, see https://kubernetes.io/docs/concepts/overview/working-with-objects/names/#rfc-1035-label-names
+pub const LOWERCASE_RFC_1035_LABEL_FMT: &str = "[a-z]([-a-z0-9]*[a-z0-9])?";
+const LOWERCASE_RFC_1035_LABEL_ERROR_MSG: &str = "a DNS-1035 label must consist of lower case alphanumeric characters or '-', start with an alphabetic character, and end with an alphanumeric character";
 
 // This is a label's max length in DNS (RFC 1035)
-const RFC_1035_LABEL_MAX_LENGTH: usize = 63;
+pub const RFC_1035_LABEL_MAX_LENGTH: usize = 63;
 
 // Technically Kerberos allows more realm names
 // (https://web.mit.edu/kerberos/krb5-1.21/doc/admin/realm_config.html#realm-name),
@@ -54,12 +65,19 @@ pub(crate) static DOMAIN_REGEX: LazyLock<Regex> = LazyLock::new(|| {
     Regex::new(&format!("^{DOMAIN_FMT}$")).expect("failed to compile domain regex")
 });
 
-static RFC_1123_LABEL_REGEX: LazyLock<Regex> = LazyLock::new(|| {
-    Regex::new(&format!("^{RFC_1123_LABEL_FMT}$")).expect("failed to compile RFC 1123 label regex")
+static LOWERCASE_RFC_1123_LABEL_REGEX: LazyLock<Regex> = LazyLock::new(|| {
+    Regex::new(&format!("^{LOWERCASE_RFC_1123_LABEL_FMT}$"))
+        .expect("failed to compile RFC 1123 label regex")
+});
+
+static LOWERCASE_RFC_1123_SUBDOMAIN_REGEX: LazyLock<Regex> = LazyLock::new(|| {
+    Regex::new(&format!("^{LOWERCASE_RFC_1123_SUBDOMAIN_FMT}$"))
+        .expect("failed to compile RFC 1123 subdomain regex")
 });
 
-static RFC_1035_LABEL_REGEX: LazyLock<Regex> = LazyLock::new(|| {
-    Regex::new(&format!("^{RFC_1035_LABEL_FMT}$")).expect("failed to compile RFC 1035 label regex")
+static LOWERCASE_RFC_1035_LABEL_REGEX: LazyLock<Regex> = LazyLock::new(|| {
+    Regex::new(&format!("^{LOWERCASE_RFC_1035_LABEL_FMT}$"))
+        .expect("failed to compile RFC 1035 label regex")
 });
 
 pub(crate) static KERBEROS_REALM_NAME_REGEX: LazyLock<Regex> = LazyLock::new(|| {
@@ -198,28 +216,44 @@ pub fn is_domain(value: &str) -> Result {
     ])
 }
 
-/// Tests for a string that conforms to the definition of a label in DNS (RFC 1123).
+/// Tests for a string that conforms to the kubernetes-specific definition of a label in DNS (RFC 1123)
+/// used in Namespace names, see: [Kubernetes Docs](https://kubernetes.io/docs/concepts/overview/working-with-objects/names/#dns-label-names)
 /// Maximum label length supported by k8s is 63 characters (minimum required).
-pub fn is_rfc_1123_label(value: &str) -> Result {
+pub fn is_lowercase_rfc_1123_label(value: &str) -> Result {
     validate_all([
         validate_str_length(value, RFC_1123_LABEL_MAX_LENGTH),
         validate_str_regex(
             value,
-            &RFC_1123_LABEL_REGEX,
-            RFC_1123_LABEL_ERROR_MSG,
+            &LOWERCASE_RFC_1123_LABEL_REGEX,
+            LOWERCASE_RFC_1123_LABEL_ERROR_MSG,
             &["example-label", "1-label-1"],
         ),
     ])
 }
 
-/// Tests for a string that conforms to the definition of a label in DNS (RFC 1035).
-pub fn is_rfc_1035_label(value: &str) -> Result {
+/// Tests for a string that conforms to the kubernetes-specific definition of a subdomain in DNS (RFC 1123)
+/// used in ConfigMap names, see [Kubernetes Docs](https://kubernetes.io/docs/concepts/overview/working-with-objects/names/#dns-subdomain-names)
+pub fn is_lowercase_rfc_1123_subdomain(value: &str) -> Result {
+    validate_all([
+        validate_str_length(value, RFC_1123_SUBDOMAIN_MAX_LENGTH),
+        validate_str_regex(
+            value,
+            &LOWERCASE_RFC_1123_SUBDOMAIN_REGEX,
+            LOWERCASE_RFC_1123_SUBDOMAIN_ERROR_MSG,
+            &["example.com"],
+        ),
+    ])
+}
+
+/// Tests for a string that conforms to the kubernetes-specific definition of a label in DNS (RFC 1035)
+/// used in Service names, see: [Kubernetes Docs](https://kubernetes.io/docs/concepts/overview/working-with-objects/names/#rfc-1035-label-names)
+pub fn is_lowercase_rfc_1035_label(value: &str) -> Result {
     validate_all([
         validate_str_length(value, RFC_1035_LABEL_MAX_LENGTH),
         validate_str_regex(
             value,
-            &RFC_1035_LABEL_REGEX,
-            RFC_1035_LABEL_ERROR_MSG,
+            &LOWERCASE_RFC_1035_LABEL_REGEX,
+            LOWERCASE_RFC_1035_LABEL_ERROR_MSG,
             &["my-name", "abc-123"],
         ),
     ])
@@ -261,7 +295,7 @@ pub fn name_is_dns_label(name: &str, prefix: bool) -> Result {
         name = mask_trailing_dash(name);
     }
 
-    is_rfc_1035_label(&name)
+    is_lowercase_rfc_1035_label(&name)
 }
 
 /// Validates a namespace name.
@@ -277,28 +311,14 @@ mod tests {
 
     use super::*;
 
-    const RFC_1123_SUBDOMAIN_ERROR_MSG: &str = "a RFC 1123 subdomain must consist of alphanumeric characters, '-' or '.', and must start and end with an alphanumeric character";
-
-    static RFC_1123_SUBDOMAIN_REGEX: LazyLock<Regex> = LazyLock::new(|| {
-        Regex::new(&format!("^{RFC_1123_SUBDOMAIN_FMT}$"))
-            .expect("failed to compile RFC 1123 subdomain regex")
-    });
-
-    /// Tests for a string that conforms to the definition of a subdomain in DNS (RFC 1123).
-    fn is_rfc_1123_subdomain(value: &str) -> Result {
-        validate_all([
-            validate_str_length(value, RFC_1123_SUBDOMAIN_MAX_LENGTH),
-            validate_str_regex(
-                value,
-                &RFC_1123_SUBDOMAIN_REGEX,
-                RFC_1123_SUBDOMAIN_ERROR_MSG,
-                &["example.com"],
-            ),
-        ])
-    }
-
     #[rstest]
     #[case("")]
+    #[case("A")]
+    #[case("aBc")]
+    #[case("ABC")]
+    #[case("A1")]
+    #[case("A-1")]
+    #[case("1-A")]
     #[case("-")]
     #[case("a-")]
     #[case("-a")]
@@ -325,6 +345,24 @@ mod tests {
     #[case("1 ")]
     #[case(" 1")]
     #[case("1 2")]
+    #[case("A.a")]
+    #[case("aB.a")]
+    #[case("ab.A")]
+    #[case("A1.a")]
+    #[case("a1.A")]
+    #[case("A.1")]
+    #[case("aB.1")]
+    #[case("A1.1")]
+    #[case("0.A")]
+    #[case("01.A")]
+    #[case("012.A")]
+    #[case("1A.a")]
+    #[case("1a.A")]
+    #[case("1A.1")]
+    #[case("a.B.c.d.e")]
+    #[case("A.B.C.D.E")]
+    #[case("aa.bB.cc.dd.ee")]
+    #[case("AA.BB.CC.DD.EE")]
     #[case("a@b")]
     #[case("a,b")]
     #[case("a_b")]
@@ -335,77 +373,53 @@ mod tests {
     #[case("a$b")]
     #[case(&"a".repeat(254))]
     fn is_rfc_1123_subdomain_fail(#[case] value: &str) {
-        assert!(is_rfc_1123_subdomain(value).is_err());
+        assert!(is_lowercase_rfc_1123_subdomain(value).is_err());
     }
 
     #[rstest]
     #[case("a")]
-    #[case("A")]
     #[case("ab")]
     #[case("abc")]
-    #[case("aBc")]
-    #[case("ABC")]
     #[case("a1")]
-    #[case("A1")]
     #[case("a-1")]
-    #[case("A-1")]
     #[case("a--1--2--b")]
     #[case("0")]
     #[case("01")]
     #[case("012")]
     #[case("1a")]
     #[case("1-a")]
-    #[case("1-A")]
     #[case("1--a--b--2")]
     #[case("a.a")]
-    #[case("A.a")]
     #[case("ab.a")]
-    #[case("aB.a")]
-    #[case("ab.A")]
     #[case("abc.a")]
     #[case("a1.a")]
-    #[case("A1.a")]
-    #[case("a1.A")]
     #[case("a-1.a")]
     #[case("a--1--2--b.a")]
     #[case("a.1")]
-    #[case("A.1")]
     #[case("ab.1")]
-    #[case("aB.1")]
     #[case("abc.1")]
     #[case("a1.1")]
-    #[case("A1.1")]
     #[case("a-1.1")]
     #[case("a--1--2--b.1")]
     #[case("0.a")]
-    #[case("0.A")]
     #[case("01.a")]
-    #[case("01.A")]
     #[case("012.a")]
-    #[case("012.A")]
     #[case("1a.a")]
-    #[case("1A.a")]
-    #[case("1a.A")]
     #[case("1-a.a")]
     #[case("1--a--b--2")]
     #[case("0.1")]
     #[case("01.1")]
     #[case("012.1")]
     #[case("1a.1")]
-    #[case("1A.1")]
     #[case("1-a.1")]
     #[case("1--a--b--2.1")]
     #[case("a.b.c.d.e")]
-    #[case("a.B.c.d.e")]
-    #[case("A.B.C.D.E")]
     #[case("aa.bb.cc.dd.ee")]
-    #[case("aa.bB.cc.dd.ee")]
-    #[case("AA.BB.CC.DD.EE")]
     #[case("1.2.3.4.5")]
     #[case("11.22.33.44.55")]
     #[case(&"a".repeat(253))]
     fn is_rfc_1123_subdomain_pass(#[case] value: &str) {
-        assert!(is_rfc_1123_subdomain(value).is_ok());
+        assert!(is_lowercase_rfc_1123_subdomain(value).is_ok());
         // Every valid RFC1123 is also a valid domain
         assert!(is_domain(value).is_ok());
     }
@@ -469,7 +483,7 @@ mod tests {
     #[case("1 2")]
     #[case(&"a".repeat(64))]
     fn is_rfc_1035_label_fail(#[case] value: &str) {
-        assert!(is_rfc_1035_label(value).is_err());
+        assert!(is_lowercase_rfc_1035_label(value).is_err());
     }
 
     #[rstest]
@@ -481,6 +495,6 @@ mod tests {
     #[case("a--1--2--b")]
     #[case(&"a".repeat(63))]
     fn is_rfc_1035_label_pass(#[case] value: &str) {
-        assert!(is_rfc_1035_label(value).is_ok());
+        assert!(is_lowercase_rfc_1035_label(value).is_ok());
     }
 }
