github.com/smallstep/pkcs7 v0.0.0-20231024181729-3b98ecc1ca81: Parse

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 github.com/smallstep/pkcs7.Parse in pkg:golang/github.com/smallstep/pkcs7@v0.0.0-20231024181729-3b98ecc1ca81
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/github.com/smallstep/pkcs7@v0.0.0-20231024181729-3b98ecc1ca81
Demonstrate these symbols/APIs:
  - github.com/smallstep/pkcs7.Parse
Constraints:
  - executionContext: node
Required runtime conditions:
  - ecosystem: npm
  - language: javascript
  - moduleSystem: cjs
  - packageManager: npm@10.9.8
  - runtime: node@22.23.2

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:e738581f52e4957d2e55120ba361914340955b3dd80bf6e200e999745e39ded4","contract":["Parse successfully parses signed PKCS#7 DER bytes and extracts payload content and certificates","Parse extracts signatures and validates signature authenticity using Verify and VerifyWithChain","Parse successfully parses enveloped PKCS#7 DER bytes and decrypts ciphertext","Parse returns an error when given invalid, empty, or truncated DER-encoded data","GetOnlySigner returns the single signing certificate from parsed PKCS#7 signed data"],"goal":"verify github.com/smallstep/pkcs7.Parse in pkg:golang/github.com/smallstep/pkcs7@v0.0.0-20231024181729-3b98ecc1ca81","kind":"HOW","packages":["pkg:golang/github.com/smallstep/pkcs7@v0.0.0-20231024181729-3b98ecc1ca81"],"schemaVersion":1,"symbols":["github.com/smallstep/pkcs7.Parse"]},"contractCommand":["go","run","./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/github.com/smallstep/pkcs7@v0.0.0-20231024181729-3b98ecc1ca81"],"schemaVersion":1,"subject":"pkg:golang/github.com/smallstep/pkcs7@v0.0.0-20231024181729-3b98ecc1ca81","symbols":["github.com/smallstep/pkcs7.Parse"],"verifierAdapter":"golang@1"}

module example.com/sample

go 1.26.6

require github.com/smallstep/pkcs7 v0.2.3

github.com/smallstep/pkcs7 v0.2.3 h1:bhoQ3TeZmdoXTatcwxCbk+FMcdsyr0gYrrW2Xq2qr+s=
github.com/smallstep/pkcs7 v0.2.3/go.mod h1:7STkdKhZaZe4xNEXTtY4j1NGeST1gYM4GA40kC5iqr8=

package main

import (
	"crypto/rand"
	"crypto/rsa"
	"crypto/x509"
	"crypto/x509/pkix"
	"fmt"
	"math/big"
	"time"

	"github.com/smallstep/pkcs7"
)

// generateTestKeyPair creates a self-signed x509 certificate and RSA private key for demonstration.
func generateTestKeyPair() (*x509.Certificate, *rsa.PrivateKey, error) {
	priv, err := rsa.GenerateKey(rand.Reader, 2048)
	if err != nil {
		return nil, nil, fmt.Errorf("failed to generate RSA key: %w", err)
	}

	template := &x509.Certificate{
		SerialNumber: big.NewInt(1),
		Subject: pkix.Name{
			CommonName: "demo.example.com",
		},
		NotBefore:             time.Now().Add(-1 * time.Hour),
		NotAfter:              time.Now().Add(24 * time.Hour),
		KeyUsage:              x509.KeyUsageDigitalSignature | x509.KeyUsageKeyEncipherment,
		ExtKeyUsage:           []x509.ExtKeyUsage{x509.ExtKeyUsageCodeSigning},
		BasicConstraintsValid: true,
		IsCA:                  true,
	}

	derBytes, err := x509.CreateCertificate(rand.Reader, template, template, &priv.PublicKey, priv)
	if err != nil {
		return nil, nil, fmt.Errorf("failed to create certificate: %w", err)
	}

	cert, err := x509.ParseCertificate(derBytes)
	if err != nil {
		return nil, nil, fmt.Errorf("failed to parse certificate: %w", err)
	}

	return cert, priv, nil
}

func main() {
	cert, privKey, err := generateTestKeyPair()
	if err != nil {
		fmt.Printf("Error creating keypair: %v\n", err)
		return
	}

	message := []byte("Verified payload for PKCS#7 Parse demonstration")

	// 1. Create a signed PKCS#7 structure
	sd, err := pkcs7.NewSignedData(message)
	if err != nil {
		fmt.Printf("Error creating signed data: %v\n", err)
		return
	}
	if err := sd.AddSigner(cert, privKey, pkcs7.SignerInfoConfig{}); err != nil {
		fmt.Printf("Error adding signer: %v\n", err)
		return
	}
	signedDER, err := sd.Finish()
	if err != nil {
		fmt.Printf("Error finishing signed data: %v\n", err)
		return
	}

	// 2. Parse the signed PKCS#7 DER payload using pkcs7.Parse
	p7Signed, err := pkcs7.Parse(signedDER)
	if err != nil {
		fmt.Printf("pkcs7.Parse error: %v\n", err)
		return
	}
	fmt.Printf("Parsed signed PKCS#7 structure: %d bytes content, %d certificates\n",
		len(p7Signed.Content), len(p7Signed.Certificates))

	// Verify the parsed signature
	pool := x509.NewCertPool()
	pool.AddCert(cert)
	if err := p7Signed.VerifyWithChain(pool); err != nil {
		fmt.Printf("Verification error: %v\n", err)
		return
	}
	fmt.Println("Signature successfully verified against cert pool")

	// 3. Create and parse encrypted EnvelopedData
	encryptedDER, err := pkcs7.Encrypt(message, []*x509.Certificate{cert})
	if err != nil {
		fmt.Printf("Encrypt error: %v\n", err)
		return
	}

	p7Encrypted, err := pkcs7.Parse(encryptedDER)
	if err != nil {
		fmt.Printf("pkcs7.Parse encrypted error: %v\n", err)
		return
	}
	decrypted, err := p7Encrypted.Decrypt(cert, privKey)
	if err != nil {
		fmt.Printf("Decrypt error: %v\n", err)
		return
	}
	fmt.Printf("Parsed and decrypted payload: %s\n", string(decrypted))
}

{
  "schemaVersion": 1,
  "goal": "verify github.com/smallstep/pkcs7.Parse in pkg:golang/github.com/smallstep/pkcs7@v0.0.0-20231024181729-3b98ecc1ca81",
  "kind": "HOW",
  "packages": [
    "pkg:golang/github.com/smallstep/pkcs7@v0.0.0-20231024181729-3b98ecc1ca81"
  ],
  "symbols": [
    "github.com/smallstep/pkcs7.Parse"
  ],
  "constraints": {
    "executionContext": "node"
  },
  "runtimeConditions": {
    "ecosystem": "npm",
    "language": "javascript",
    "moduleSystem": "cjs",
    "packageManager": "npm@10.9.8",
    "runtime": "node@22.23.2"
  }
}

package main

import (
	"bytes"
	"crypto/rand"
	"crypto/rsa"
	"crypto/x509"
	"crypto/x509/pkix"
	"fmt"
	"math/big"
	"os"
	"time"

	"github.com/smallstep/pkcs7"
)

func generateTestCertificate() (*x509.Certificate, *rsa.PrivateKey, error) {
	priv, err := rsa.GenerateKey(rand.Reader, 2048)
	if err != nil {
		return nil, nil, fmt.Errorf("failed to generate RSA key: %w", err)
	}

	template := &x509.Certificate{
		SerialNumber: big.NewInt(2001),
		Subject: pkix.Name{
			CommonName: "signer.contract.example.com",
		},
		NotBefore:             time.Now().Add(-1 * time.Hour),
		NotAfter:              time.Now().Add(24 * time.Hour),
		KeyUsage:              x509.KeyUsageDigitalSignature | x509.KeyUsageKeyEncipherment,
		ExtKeyUsage:           []x509.ExtKeyUsage{x509.ExtKeyUsageCodeSigning, x509.ExtKeyUsageEmailProtection},
		BasicConstraintsValid: true,
		IsCA:                  true,
	}

	derBytes, err := x509.CreateCertificate(rand.Reader, template, template, &priv.PublicKey, priv)
	if err != nil {
		return nil, nil, fmt.Errorf("failed to create certificate: %w", err)
	}

	cert, err := x509.ParseCertificate(derBytes)
	if err != nil {
		return nil, nil, fmt.Errorf("failed to parse certificate: %w", err)
	}

	return cert, priv, nil
}

func main() {
	cert, privKey, err := generateTestCertificate()
	if err != nil {
		fmt.Fprintf(os.Stderr, "FAIL: certificate generation failed: %v\n", err)
		os.Exit(1)
	}

	rawMessage := []byte("Contract test payload for github.com/smallstep/pkcs7.Parse")

	// Assertion 1: Parse successfully parses signed PKCS#7 DER bytes and extracts payload content and certificates
	var signedDER []byte
	var parsedSigned *pkcs7.PKCS7
	{
		sd, err := pkcs7.NewSignedData(rawMessage)
		if err != nil {
			fmt.Fprintf(os.Stderr, "FAIL: NewSignedData error: %v\n", err)
			os.Exit(1)
		}

		if err := sd.AddSigner(cert, privKey, pkcs7.SignerInfoConfig{}); err != nil {
			fmt.Fprintf(os.Stderr, "FAIL: AddSigner error: %v\n", err)
			os.Exit(1)
		}

		signedDER, err = sd.Finish()
		if err != nil {
			fmt.Fprintf(os.Stderr, "FAIL: Finish error: %v\n", err)
			os.Exit(1)
		}

		parsedSigned, err = pkcs7.Parse(signedDER)
		if err != nil {
			fmt.Fprintf(os.Stderr, "FAIL: Parse signed data failed: %v\n", err)
			os.Exit(1)
		}

		if !bytes.Equal(parsedSigned.Content, rawMessage) {
			fmt.Fprintf(os.Stderr, "FAIL: Content mismatch, got %q, want %q\n", parsedSigned.Content, rawMessage)
			os.Exit(1)
		}

		if len(parsedSigned.Certificates) != 1 {
			fmt.Fprintf(os.Stderr, "FAIL: expected 1 certificate in parsedSigned, got %d\n", len(parsedSigned.Certificates))
			os.Exit(1)
		}
	}

	// Assertion 2: Parse extracts signatures and validates signature authenticity using Verify and VerifyWithChain
	{
		if err := parsedSigned.Verify(); err != nil {
			fmt.Fprintf(os.Stderr, "FAIL: Verify error: %v\n", err)
			os.Exit(1)
		}

		trustedPool := x509.NewCertPool()
		trustedPool.AddCert(cert)
		if err := parsedSigned.VerifyWithChain(trustedPool); err != nil {
			fmt.Fprintf(os.Stderr, "FAIL: VerifyWithChain error: %v\n", err)
			os.Exit(1)
		}

		untrustedPool := x509.NewCertPool()
		if err := parsedSigned.VerifyWithChain(untrustedPool); err == nil {
			fmt.Fprintf(os.Stderr, "FAIL: VerifyWithChain expected error with untrusted pool, got nil\n")
			os.Exit(1)
		}
	}

	// Assertion 3: Parse successfully parses enveloped PKCS#7 DER bytes and decrypts ciphertext
	{
		secretPayload := []byte("confidential message content for encryption verification")
		encryptedDER, err := pkcs7.Encrypt(secretPayload, []*x509.Certificate{cert})
		if err != nil {
			fmt.Fprintf(os.Stderr, "FAIL: Encrypt error: %v\n", err)
			os.Exit(1)
		}

		parsedEnc, err := pkcs7.Parse(encryptedDER)
		if err != nil {
			fmt.Fprintf(os.Stderr, "FAIL: Parse encrypted data error: %v\n", err)
			os.Exit(1)
		}

		decrypted, err := parsedEnc.Decrypt(cert, privKey)
		if err != nil {
			fmt.Fprintf(os.Stderr, "FAIL: Decrypt error: %v\n", err)
			os.Exit(1)
		}

		if !bytes.Equal(decrypted, secretPayload) {
			fmt.Fprintf(os.Stderr, "FAIL: decrypted data mismatch, got %q, want %q\n", decrypted, secretPayload)
			os.Exit(1)
		}
	}

	// Assertion 4: Parse returns an error when given invalid, empty, or truncated DER-encoded data
	{
		invalidDER := []byte{0x30, 0x05, 0x00, 0x01, 0x02}
		if _, err := pkcs7.Parse(invalidDER); err == nil {
			fmt.Fprintf(os.Stderr, "FAIL: Parse should return error for invalid DER\n")
			os.Exit(1)
		}

		if _, err := pkcs7.Parse([]byte{}); err == nil {
			fmt.Fprintf(os.Stderr, "FAIL: Parse should return error for empty slice\n")
			os.Exit(1)
		}

		if len(signedDER) > 10 {
			truncatedDER := signedDER[:10]
			if _, err := pkcs7.Parse(truncatedDER); err == nil {
				fmt.Fprintf(os.Stderr, "FAIL: Parse should return error for truncated DER\n")
				os.Exit(1)
			}
		}
	}

	// Assertion 5: GetOnlySigner returns the single signing certificate from parsed PKCS#7 signed data
	{
		signerCert := parsedSigned.GetOnlySigner()
		if signerCert == nil {
			fmt.Fprintf(os.Stderr, "FAIL: GetOnlySigner returned nil\n")
			os.Exit(1)
		}

		if signerCert.Subject.CommonName != "signer.contract.example.com" {
			fmt.Fprintf(os.Stderr, "FAIL: Signer CommonName mismatch, got %s\n", signerCert.Subject.CommonName)
			os.Exit(1)
		}
	}

	fmt.Println("PASS: github.com/smallstep/pkcs7.Parse contract verified")
}