Rewrite CA and cert generation to use builder pattern

Author: sbernauer

Cargo.lock

@@ -12,6 +12,7 @@ repository = "https://github.com/stackabletech/operator-rs"
 product-config = { git = "https://github.com/stackabletech/product-config.git", tag = "0.7.0" }
 
 axum = { version = "0.8.1", features = ["http2"] }
+bon = "3.6.3"
 chrono = { version = "0.4.38", default-features = false }
 clap = { version = "4.5.17", features = ["derive", "cargo", "env"] }
 const_format = "0.2.33"

Cargo.toml

@@ -6,13 +6,14 @@ All notable changes to this project will be documented in this file.
 
 ### Added
 
-- BREAKING: `CertificateAuthority::generate_leaf_certificate` (and `generate_rsa_leaf_certificate` and `generate_ecdsa_leaf_certificate`)
-  now take an additional parameter `subject_alterative_dns_names`. The passed SANs are added to the generated certificate,
-  this is needed for basically all modern TLS certificate validations when used with HTTPS.
-  Pass an empty list (`[]`) to keep the existing behavior ([#1044]).
+- Support adding SAN entries to generated certificates, this is needed for basically all modern TLS
+  certificate validations when used with HTTPS ([#1044]).
 - BREAKING: The constant `DEFAULT_CA_VALIDITY_SECONDS` has been renamed to `DEFAULT_CA_VALIDITY` and now is of type `stackable_operator::time::Duration`.
   Also, the constant `ROOT_CA_SUBJECT` has been renamed to `SDP_ROOT_CA_SUBJECT` ([#1044]).
-- Added the function `CertificateAuthority::ca_cert` to easily get the CA `Certificate` ([#1044]).
+
+### Changed
+
+- GIGA BREAKING: Rewrite entire CA and cert generation to use a builder pattern ([#1044]).
 
 ## [0.3.1] - 2024-07-10
 

crates/stackable-certs/CHANGELOG.md

@@ -13,6 +13,7 @@ rustls = ["dep:tokio-rustls"]
 [dependencies]
 stackable-operator = { path = "../stackable-operator" }
 
+bon.workspace = true
 const-oid.workspace = true
 ecdsa.workspace = true
 k8s-openapi.workspace = true

crates/stackable-certs/Cargo.toml

@@ -0,0 +1,241 @@
+use bon::Builder;
+use rsa::pkcs8::EncodePublicKey;
+use snafu::{ResultExt, Snafu};
+use stackable_operator::time::Duration;
+use tracing::debug;
+use x509_cert::{
+    builder::{Builder, CertificateBuilder, Profile},
+    der::{DecodePem, referenced::OwnedToRef},
+    ext::pkix::AuthorityKeyIdentifier,
+    name::Name,
+    serial_number::SerialNumber,
+    spki::SubjectPublicKeyInfoOwned,
+    time::Validity,
+};
+
+use super::CertificateAuthority;
+use crate::{
+    CertificatePair,
+    ca::{DEFAULT_CA_VALIDITY, PEM_LINE_ENDING, SDP_ROOT_CA_SUBJECT},
+    keys::CertificateKeypair,
+};
+
+/// Defines all error variants which can occur when creating a CA
+#[derive(Debug, Snafu)]
+pub enum CreateCertificateAuthorityError<E>
+where
+    E: std::error::Error + 'static,
+{
+    #[snafu(display("failed to parse validity"))]
+    ParseValidity { source: x509_cert::der::Error },
+
+    #[snafu(display("failed to parse \"{subject}\" as subject"))]
+    ParseSubject {
+        source: x509_cert::der::Error,
+        subject: String,
+    },
+
+    #[snafu(display("failed to create signing key pair"))]
+    CreateSigningKeyPair { source: E },
+
+    #[snafu(display("failed to serialize public key as PEM"))]
+    SerializePublicKey { source: x509_cert::spki::Error },
+
+    #[snafu(display("failed to decode SPKI from PEM"))]
+    DecodeSpkiFromPem { source: x509_cert::der::Error },
+
+    #[snafu(display("failed to parse AuthorityKeyIdentifier"))]
+    ParseAuthorityKeyIdentifier { source: x509_cert::der::Error },
+
+    #[snafu(display("failed to create certificate builder"))]
+    CreateCertificateBuilder { source: x509_cert::builder::Error },
+
+    #[snafu(display("failed to add certificate extension"))]
+    AddCertificateExtension { source: x509_cert::builder::Error },
+
+    #[snafu(display("failed to build certificate"))]
+    BuildCertificate { source: x509_cert::builder::Error },
+}
+
+/// This builder builds certificate authorities of type [`CertificateAuthority`].
+///
+/// Example code to construct a CA:
+///
+/// ```no_run
+/// use stackable_certs::{
+///     keys::ecdsa,
+///     ca::{CertificateAuthority, CertificateAuthorityBuilder},
+/// };
+///
+/// let ca: CertificateAuthority<ecdsa::SigningKey> = CertificateAuthorityBuilder::builder()
+///     .build()
+///     .build_ca()
+///     .expect("failed to build CA");
+/// ```
+#[derive(Builder)]
+pub struct CertificateAuthorityBuilder<'a, SKP>
+where
+    SKP: CertificateKeypair,
+    <SKP::SigningKey as signature::Keypair>::VerifyingKey: EncodePublicKey,
+{
+    /// Required subject of the certificate authority, usually starts with `CN=`.
+    #[builder(default = SDP_ROOT_CA_SUBJECT)]
+    subject: &'a str,
+
+    /// Validity/lifetime of the certificate.
+    ///
+    /// If not specified the default of [`DEFAULT_CA_VALIDITY`] will be used.
+    #[builder(default = DEFAULT_CA_VALIDITY)]
+    validity: Duration,
+
+    /// Serial number of the generated certificate.
+    ///
+    /// If not specified a random serial will be generated.
+    serial_number: Option<u64>,
+
+    /// Cryptographic keypair used to sign leaf certificates.
+    ///
+    /// If not specified a random keypair will be generated.
+    signing_key_pair: Option<SKP>,
+}
+
+impl<SKP> CertificateAuthorityBuilder<'_, SKP>
+where
+    SKP: CertificateKeypair,
+    <SKP::SigningKey as signature::Keypair>::VerifyingKey: EncodePublicKey,
+{
+    pub fn build_ca(
+        self,
+    ) -> Result<CertificateAuthority<SKP>, CreateCertificateAuthorityError<SKP::Error>> {
+        let serial_number =
+            SerialNumber::from(self.serial_number.unwrap_or_else(|| rand::random::<u64>()));
+        let validity = Validity::from_now(*self.validity).context(ParseValiditySnafu)?;
+        let subject: Name = self.subject.parse().context(ParseSubjectSnafu {
+            subject: self.subject,
+        })?;
+        let signing_key_pair = match self.signing_key_pair {
+            Some(signing_key_pair) => signing_key_pair,
+            None => SKP::new().context(CreateSigningKeyPairSnafu)?,
+        };
+
+        let spki_pem = signing_key_pair
+            .verifying_key()
+            .to_public_key_pem(PEM_LINE_ENDING)
+            .context(SerializePublicKeySnafu)?;
+
+        let spki = SubjectPublicKeyInfoOwned::from_pem(spki_pem.as_bytes())
+            .context(DecodeSpkiFromPemSnafu)?;
+
+        // There are multiple default extensions included in the profile. For
+        // the root profile, these are:
+        //
+        // - BasicConstraints marked as critical and CA = true
+        // - SubjectKeyIdentifier with the 160-bit SHA-1 hash of the subject
+        //   public key.
+        // - KeyUsage with KeyCertSign and CRLSign bits set. Ideally we also
+        //   want to include the DigitalSignature bit, which for example is
+        //   required for CA certs which want to sign an OCSP response.
+        //   Currently, the root profile doesn't include that bit.
+        //
+        // The root profile doesn't add the AuthorityKeyIdentifier extension.
+        // We manually add it below by using the 160-bit SHA-1 hash of the
+        // subject public key. This conforms to one of the outlined methods for
+        // generating key identifiers outlined in RFC 5280, section 4.2.1.2.
+        //
+        // Prepare extensions so we can avoid clones.
+        let aki = AuthorityKeyIdentifier::try_from(spki.owned_to_ref())
+            .context(ParseAuthorityKeyIdentifierSnafu)?;
+
+        let signer = signing_key_pair.signing_key();
+        let mut builder = CertificateBuilder::new(
+            Profile::Root,
+            serial_number,
+            validity,
+            subject,
+            spki,
+            signer,
+        )
+        .context(CreateCertificateBuilderSnafu)?;
+
+        // Add extension constructed above
+        builder
+            .add_extension(&aki)
+            .context(AddCertificateExtensionSnafu)?;
+
+        debug!("create and sign CA certificate");
+        let certificate = builder.build().context(BuildCertificateSnafu)?;
+
+        Ok(CertificateAuthority {
+            certificate_pair: CertificatePair {
+                certificate,
+                key_pair: signing_key_pair,
+            },
+        })
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use x509_cert::certificate::TbsCertificateInner;
+
+    use super::*;
+    use crate::keys::{ecdsa, rsa};
+
+    #[test]
+    fn minimal_ca() {
+        let ca: CertificateAuthority<ecdsa::SigningKey> = CertificateAuthorityBuilder::builder()
+            .build()
+            .build_ca()
+            .expect("failed to build CA");
+
+        assert_ca_cert_attributes(
+            &ca.ca_cert().tbs_certificate,
+            SDP_ROOT_CA_SUBJECT,
+            DEFAULT_CA_VALIDITY,
+            None,
+        )
+    }
+
+    #[test]
+    fn customized_ca() {
+        let ca = CertificateAuthorityBuilder::builder()
+            .subject("CN=Test")
+            .serial_number(42)
+            .signing_key_pair(rsa::SigningKey::new().unwrap())
+            .validity(Duration::from_days_unchecked(13))
+            .build()
+            .build_ca()
+            .expect("failed to build CA");
+
+        assert_ca_cert_attributes(
+            &ca.ca_cert().tbs_certificate,
+            "CN=Test",
+            Duration::from_days_unchecked(13),
+            Some(42),
+        )
+    }
+
+    fn assert_ca_cert_attributes(
+        ca_cert: &TbsCertificateInner,
+        subject: &str,
+        validity: Duration,
+        serial_number: Option<u64>,
+    ) {
+        assert_eq!(ca_cert.subject, subject.parse().unwrap());
+
+        let not_before = ca_cert.validity.not_before.to_system_time();
+        let not_after = ca_cert.validity.not_after.to_system_time();
+        assert_eq!(
+            not_after
+                .duration_since(not_before)
+                .expect("Failed to calculate duration between notBefore and notAfter"),
+            *validity
+        );
+
+        if let Some(serial_number) = serial_number {
+            assert_eq!(ca_cert.serial_number, SerialNumber::from(serial_number))
+        } else {
+            assert_ne!(ca_cert.serial_number, SerialNumber::from(0_u64))
+        }
+    }
+}

crates/stackable-certs/src/ca/ca_builder.rs

@@ -1,7 +1,13 @@
+use rsa::pkcs8::LineEnding;
 use stackable_operator::time::Duration;
 
-/// The default CA validity time span of one hour (3600 seconds).
+/// The default CA validity time span of one hour.
 pub const DEFAULT_CA_VALIDITY: Duration = Duration::from_hours_unchecked(1);
 
+/// The default certificate validity time span of one hour.
+pub const DEFAULT_CERTIFICATE_VALIDITY: Duration = Duration::from_hours_unchecked(1);
+
 /// The root CA subject name containing only the common name.
 pub const SDP_ROOT_CA_SUBJECT: &str = "CN=Stackable Data Platform Internal CA";
+
+pub const PEM_LINE_ENDING: LineEnding = LineEnding::LF;