kubernetes/kops · error

generating ecdsa key: %w

Error message

generating ecdsa key: %w

What it means

BuildChallengeServerCertificate wraps a failure from pki.GeneratePrivateKey while creating the ECDSA key for the challenge server's TLS certificate. This indicates the internal key generation failed, which is practically only caused by a failure of the underlying crypto/rand reader (system entropy unavailable).

Source

Thrown at pkg/bootstrap/challenge.go:61

		CommonName: "kops-controller." + clusterName,
	}
}

func subjectsMatch(l, r pkix.Name) bool {
	// We need to check all the fields in challengeKopsControllerSubject
	return l.CommonName == r.CommonName
}

func challengeServerHostName(clusterName string) string {
	return "challenge-server." + clusterName
}

func BuildChallengeServerCertificate(clusterName string) (*tls.Certificate, error) {
	serverName := challengeServerHostName(clusterName)

	privateKey, err := pki.GeneratePrivateKey()
	if err != nil {
		return nil, fmt.Errorf("generating ecdsa key: %w", err)
	}

	keyUsage := x509.KeyUsageDigitalSignature | x509.KeyUsageKeyEncipherment

	now := time.Now()
	notBefore := now.Add(-15 * time.Minute)
	notAfter := notBefore.Add(time.Hour)

	template := x509.Certificate{
		SerialNumber: big.NewInt(1),
		Subject: pkix.Name{
			CommonName: serverName,
		},
		NotBefore: notBefore,
		NotAfter:  notAfter,

		KeyUsage:              keyUsage,
		ExtKeyUsage:           []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth},

View on GitHub (pinned to 4c8573c808)

Solutions

1. Verify /dev/urandom is readable in the environment the server runs in (ls -l /dev/urandom; test with head -c 16 /dev/urandom)
2. Check seccomp/AppArmor or container security profiles that may block getrandom(2)
3. Restart the process — entropy failures are typically transient system-level problems
4. If it persists, inspect the Go build for any crypto/rand overrides or exotic platforms

cert, err := BuildChallengeServerCertificate(clusterName)
if err != nil {
  return fmt.Errorf("challenge server startup failed: %w", err)
}

When it happens

Trigger: NewChallengeServer calls BuildChallengeServerCertificate on startup; pki.GeneratePrivateKey -> ecdsa.GenerateKey fails because crypto/rand cannot read from the OS entropy source.

Common situations: Container/host with exhausted or blocked /dev/urandom (seccomp policies, restricted devices); heavily constrained environments where getrandom(2) fails; custom crypto builds overriding the entropy source.

Related errors

• error getting random data: %w
• error generating RSA private key: %v
• error creating secret %q: %v
• building kube client: %w
• building cert manager client: %w

AI-assisted analysis of kubernetes/kops@4c8573c808 (2026-09-05). Data as JSON: /api/errors/a8258ade37200f7e. Report an issue: GitHub.