go.step.sm/crypto v0.81.0: pemutil.ParseCertificate, pemutil.ParseKey, pemutil.Serialize

Clean-room public code sample — generation instructions

Write a brand-new, minimal, self-contained code sample in this clean-room directory.
Do not copy, paraphrase, or reference any existing project source. Work only from this spec.

A csx.json manifest scaffold already exists. Do not recreate it from memory. Preserve its case.goal, packages and symbols; fill its empty case.contract with exact assertions and correct its environment, commands and verifierAdapter for the files you generate.

Goal: verify go.step.sm/crypto/pemutil.Serialize and ParseKey in pkg:golang/go.step.sm/crypto@v0.81.0
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/go.step.sm/crypto@v0.81.0
Demonstrate these symbols/APIs:
  - go.step.sm/crypto/pemutil.ParseCertificate
  - go.step.sm/crypto/pemutil.ParseKey
  - go.step.sm/crypto/pemutil.Serialize

Rules:
  - One focused purpose; the smallest project that proves the goal.
  - Include a contract test (test/contract.*) that runs OFFLINE and exits 0 exactly when the goal behavior works.
  - Pin every dependency with a lockfile so resolution is reproducible.
  - No secrets, credentials, or tokens. No real URLs (only example.com or localhost). No absolute paths.
  - No personal names, emails, company names, or project identifiers of any kind.
  - No binaries and no generated output (node_modules, dist, target, venv, .git, .env).
  - Keep it under 200 files and 256KB packed.

{"case":{"caseId":"case:sha256:7d54a4369374ed938a0ac1b9df0a8b9e8cc40b1205178f58f4292ff9e589df7c","contract":["pemutil.Serialize encodes ECDSA, RSA, and Ed25519 private keys, public keys, and x509 certificates to PEM blocks.","pemutil.Serialize with WithPassword encrypts private keys using passphrase protection, decryptable by pemutil.ParseKey with WithPassword.","pemutil.Serialize with WithPassword and WithPKCS8 encrypts private keys into ENCRYPTED PRIVATE KEY blocks.","pemutil.ParseKey and pemutil.ParseCertificate decode PEM byte blocks into their corresponding crypto objects.","pemutil.ParseKey returns an error when given incorrect decryption passwords, and pemutil.Serialize returns an error for unsupported types."],"goal":"verify go.step.sm/crypto/pemutil.Serialize and ParseKey in pkg:golang/go.step.sm/crypto@v0.81.0","kind":"HOW","packages":["pkg:golang/go.step.sm/crypto@v0.81.0"],"schemaVersion":1,"symbols":["go.step.sm/crypto/pemutil.ParseCertificate","go.step.sm/crypto/pemutil.ParseKey","go.step.sm/crypto/pemutil.Serialize"]},"contractCommand":["go","test","./..."],"environment":{"arch":"x64","distro":"ubuntu","ecosystem":"golang","libc":"glibc","libcVersion":"2.39","os":"linux","osVersionBucket":"24","packageManager":"go","schemaVersion":1},"license":"MIT-0","packages":["pkg:golang/go.step.sm/crypto@v0.81.0"],"schemaVersion":1,"subject":"pkg:golang/go.step.sm/crypto@v0.81.0","symbols":["go.step.sm/crypto/pemutil.ParseCertificate","go.step.sm/crypto/pemutil.ParseKey","go.step.sm/crypto/pemutil.Serialize"],"verifierAdapter":"golang@1"}

module example.com/pemutil_sample

go 1.26.6

require go.step.sm/crypto v0.81.0

require (
	filippo.io/edwards25519 v1.2.0 // indirect
	github.com/pkg/errors v0.9.1 // indirect
	golang.org/x/crypto v0.50.0 // indirect
	golang.org/x/sys v0.44.0 // indirect
)

filippo.io/edwards25519 v1.2.0 h1:crnVqOiS4jqYleHd9vaKZ+HKtHfllngJIiOpNpoJsjo=
filippo.io/edwards25519 v1.2.0/go.mod h1:xzAOLCNug/yB62zG1bQ8uziwrIqIuxhctzJT18Q77mc=
github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
github.com/pkg/errors v0.9.1 h1:FEBLx1zS214owpjy7qsBeixbURkuhQAwrK5UwLGTwt4=
github.com/pkg/errors v0.9.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
github.com/stretchr/testify v1.11.1 h1:7s2iGBzp5EwR7/aIZr8ao5+dra3wiQyKjjFuvgVKu7U=
github.com/stretchr/testify v1.11.1/go.mod h1:wZwfW3scLgRK+23gO65QZefKpKQRnfz6sD981Nm4B6U=
go.step.sm/crypto v0.81.0 h1:e+ouzpNt3Xm4dp7HGXhgYB5y4iFik3vh3phHKWmvugU=
go.step.sm/crypto v0.81.0/go.mod h1:fsTizqQeASjTXnbv9O00XtRlIuXRkCdoRiJNyXGQujc=
golang.org/x/crypto v0.50.0 h1:zO47/JPrL6vsNkINmLoo/PH1gcxpls50DNogFvB5ZGI=
golang.org/x/crypto v0.50.0/go.mod h1:3muZ7vA7PBCE6xgPX7nkzzjiUq87kRItoJQM1Yo8S+Q=
golang.org/x/sys v0.44.0 h1:ildZl3J4uzeKP07r2F++Op7E9B29JRUy+a27EibtBTQ=
golang.org/x/sys v0.44.0/go.mod h1:4GL1E5IUh+htKOUEOaiffhrAeqysfVGipDYzABqnCmw=
golang.org/x/term v0.42.0 h1:UiKe+zDFmJobeJ5ggPwOshJIVt6/Ft0rcfrXZDLWAWY=
golang.org/x/term v0.42.0/go.mod h1:Dq/D+snpsbazcBG5+F9Q1n2rXV8Ma+71xEjTRufARgY=
gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

package pemutil_test

import (
	"crypto/ecdsa"
	"crypto/ed25519"
	"crypto/elliptic"
	"crypto/rand"
	"crypto/rsa"
	"crypto/x509"
	"crypto/x509/pkix"
	"encoding/pem"
	"math/big"
	"testing"
	"time"

	"go.step.sm/crypto/pemutil"
)

func TestSerialize_Keys(t *testing.T) {
	// 1. ECDSA
	ecKey, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
	if err != nil {
		t.Fatalf("GenerateKey ECDSA failed: %v", err)
	}
	ecBlock, err := pemutil.Serialize(ecKey)
	if err != nil {
		t.Fatalf("pemutil.Serialize ECDSA failed: %v", err)
	}
	if ecBlock.Type != "EC PRIVATE KEY" {
		t.Errorf("expected EC PRIVATE KEY, got %s", ecBlock.Type)
	}
	ecBytes := pem.EncodeToMemory(ecBlock)
	parsedEC, err := pemutil.ParseKey(ecBytes)
	if err != nil {
		t.Fatalf("pemutil.ParseKey ECDSA failed: %v", err)
	}
	if _, ok := parsedEC.(*ecdsa.PrivateKey); !ok {
		t.Errorf("expected *ecdsa.PrivateKey, got %T", parsedEC)
	}

	// 2. RSA
	rsaKey, err := rsa.GenerateKey(rand.Reader, 2048)
	if err != nil {
		t.Fatalf("GenerateKey RSA failed: %v", err)
	}
	rsaBlock, err := pemutil.Serialize(rsaKey)
	if err != nil {
		t.Fatalf("pemutil.Serialize RSA failed: %v", err)
	}
	if rsaBlock.Type != "RSA PRIVATE KEY" {
		t.Errorf("expected RSA PRIVATE KEY, got %s", rsaBlock.Type)
	}
	rsaBytes := pem.EncodeToMemory(rsaBlock)
	parsedRSA, err := pemutil.ParseKey(rsaBytes)
	if err != nil {
		t.Fatalf("pemutil.ParseKey RSA failed: %v", err)
	}
	if _, ok := parsedRSA.(*rsa.PrivateKey); !ok {
		t.Errorf("expected *rsa.PrivateKey, got %T", parsedRSA)
	}

	// 3. Ed25519
	_, edKey, err := ed25519.GenerateKey(rand.Reader)
	if err != nil {
		t.Fatalf("GenerateKey Ed25519 failed: %v", err)
	}
	edBlock, err := pemutil.Serialize(edKey)
	if err != nil {
		t.Fatalf("pemutil.Serialize Ed25519 failed: %v", err)
	}
	if edBlock.Type != "PRIVATE KEY" {
		t.Errorf("expected PRIVATE KEY, got %s", edBlock.Type)
	}
	edBytes := pem.EncodeToMemory(edBlock)
	parsedED, err := pemutil.ParseKey(edBytes)
	if err != nil {
		t.Fatalf("pemutil.ParseKey Ed25519 failed: %v", err)
	}
	if _, ok := parsedED.(ed25519.PrivateKey); !ok {
		t.Errorf("expected ed25519.PrivateKey, got %T", parsedED)
	}

	// 4. Public Key
	pubBlock, err := pemutil.Serialize(&ecKey.PublicKey)
	if err != nil {
		t.Fatalf("pemutil.Serialize public key failed: %v", err)
	}
	if pubBlock.Type != "PUBLIC KEY" {
		t.Errorf("expected PUBLIC KEY, got %s", pubBlock.Type)
	}
	pubBytes := pem.EncodeToMemory(pubBlock)
	parsedPub, err := pemutil.ParseKey(pubBytes)
	if err != nil {
		t.Fatalf("pemutil.ParseKey public key failed: %v", err)
	}
	if _, ok := parsedPub.(*ecdsa.PublicKey); !ok {
		t.Errorf("expected *ecdsa.PublicKey, got %T", parsedPub)
	}
}

func TestSerialize_PasswordEncryption(t *testing.T) {
	ecKey, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
	if err != nil {
		t.Fatalf("GenerateKey failed: %v", err)
	}

	password := []byte("secret-passphrase-123")

	// Standard legacy encryption
	encBlock, err := pemutil.Serialize(ecKey, pemutil.WithPassword(password))
	if err != nil {
		t.Fatalf("pemutil.Serialize WithPassword failed: %v", err)
	}
	if encBlock.Headers["Proc-Type"] != "4,ENCRYPTED" {
		t.Errorf("expected Proc-Type 4,ENCRYPTED, got %s", encBlock.Headers["Proc-Type"])
	}
	encBytes := pem.EncodeToMemory(encBlock)

	parsedKey, err := pemutil.ParseKey(encBytes, pemutil.WithPassword(password))
	if err != nil {
		t.Fatalf("pemutil.ParseKey with password failed: %v", err)
	}
	if _, ok := parsedKey.(*ecdsa.PrivateKey); !ok {
		t.Errorf("expected *ecdsa.PrivateKey, got %T", parsedKey)
	}

	// PKCS8 encryption
	pkcs8Block, err := pemutil.Serialize(ecKey, pemutil.WithPassword(password), pemutil.WithPKCS8(true))
	if err != nil {
		t.Fatalf("pemutil.Serialize WithPKCS8 failed: %v", err)
	}
	if pkcs8Block.Type != "ENCRYPTED PRIVATE KEY" {
		t.Errorf("expected ENCRYPTED PRIVATE KEY, got %s", pkcs8Block.Type)
	}
	pkcs8Bytes := pem.EncodeToMemory(pkcs8Block)

	parsedPKCS8, err := pemutil.ParseKey(pkcs8Bytes, pemutil.WithPassword(password))
	if err != nil {
		t.Fatalf("pemutil.ParseKey PKCS8 with password failed: %v", err)
	}
	if _, ok := parsedPKCS8.(*ecdsa.PrivateKey); !ok {
		t.Errorf("expected *ecdsa.PrivateKey, got %T", parsedPKCS8)
	}
}

func TestSerialize_Certificate(t *testing.T) {
	privKey, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
	if err != nil {
		t.Fatalf("GenerateKey failed: %v", err)
	}

	template := &x509.Certificate{
		SerialNumber: big.NewInt(42),
		Subject: pkix.Name{
			CommonName: "sample.example.com",
		},
		NotBefore:             time.Now().Add(-1 * time.Hour),
		NotAfter:              time.Now().Add(24 * time.Hour),
		BasicConstraintsValid: true,
		IsCA:                  true,
	}

	certDER, err := x509.CreateCertificate(rand.Reader, template, template, &privKey.PublicKey, privKey)
	if err != nil {
		t.Fatalf("CreateCertificate failed: %v", err)
	}
	cert, err := x509.ParseCertificate(certDER)
	if err != nil {
		t.Fatalf("ParseCertificate failed: %v", err)
	}

	certBlock, err := pemutil.Serialize(cert)
	if err != nil {
		t.Fatalf("pemutil.Serialize certificate failed: %v", err)
	}
	if certBlock.Type != "CERTIFICATE" {
		t.Errorf("expected CERTIFICATE, got %s", certBlock.Type)
	}

	certBytes := pem.EncodeToMemory(certBlock)
	parsedCert, err := pemutil.ParseCertificate(certBytes)
	if err != nil {
		t.Fatalf("pemutil.ParseCertificate failed: %v", err)
	}
	if parsedCert.Subject.CommonName != "sample.example.com" {
		t.Errorf("expected CommonName sample.example.com, got %s", parsedCert.Subject.CommonName)
	}
	if parsedCert.SerialNumber.Cmp(big.NewInt(42)) != 0 {
		t.Errorf("expected SerialNumber 42, got %v", parsedCert.SerialNumber)
	}
}

func TestErrors(t *testing.T) {
	ecKey, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
	if err != nil {
		t.Fatalf("GenerateKey failed: %v", err)
	}

	password := []byte("correct-password")
	encBlock, err := pemutil.Serialize(ecKey, pemutil.WithPassword(password))
	if err != nil {
		t.Fatalf("pemutil.Serialize failed: %v", err)
	}
	encBytes := pem.EncodeToMemory(encBlock)

	// Wrong password returns error
	_, err = pemutil.ParseKey(encBytes, pemutil.WithPassword([]byte("incorrect-password")))
	if err == nil {
		t.Error("expected error with incorrect password, got nil")
	}

	// Unsupported type returns error
	_, err = pemutil.Serialize(12345)
	if err == nil {
		t.Error("expected error serializing unsupported int type, got nil")
	}
}

{
  "schemaVersion": 1,
  "goal": "verify go.step.sm/crypto/pemutil.Serialize and ParseKey in pkg:golang/go.step.sm/crypto@v0.81.0",
  "kind": "HOW",
  "packages": [
    "pkg:golang/go.step.sm/crypto@v0.81.0"
  ],
  "symbols": [
    "go.step.sm/crypto/pemutil.ParseCertificate",
    "go.step.sm/crypto/pemutil.ParseKey",
    "go.step.sm/crypto/pemutil.Serialize"
  ]
}