La magie de la cryptographie dans le monde réel : mettre le package Crypto de Go au travail, Go Crypto 13

package main

import (
    "crypto/aes"
    "crypto/cipher"
    "crypto/rand"
    "errors"
    "fmt"
    "io"
    "os"
)

// Our encryption spell
func encrypt(plaintext []byte, key []byte) ([]byte, error) {
    block, err := aes.NewCipher(key)
    if err != nil {
        return nil, err
    }

    gcm, err := cipher.NewGCM(block)
    if err != nil {
        return nil, err
    }

    nonce := make([]byte, gcm.NonceSize())
    if _, err := io.ReadFull(rand.Reader, nonce); err != nil {
        return nil, err
    }

    return gcm.Seal(nonce, nonce, plaintext, nil), nil
}

// Our decryption counter-spell
func decrypt(ciphertext []byte, key []byte) ([]byte, error) {
    block, err := aes.NewCipher(key)
    if err != nil {
        return nil, err
    }

    gcm, err := cipher.NewGCM(block)
    if err != nil {
        return nil, err
    }

    if len(ciphertext) < gcm.NonceSize() {
        return nil, errors.New("ciphertext too short")
    }

    nonce, ciphertext := ciphertext[:gcm.NonceSize()], ciphertext[gcm.NonceSize():]
    return gcm.Open(nil, nonce, ciphertext, nil)
}

// Enchant a file with our encryption spell
func encryptFile(inputFile, outputFile string, key []byte) error {
    plaintext, err := os.ReadFile(inputFile)
    if err != nil {
        return err
    }

    ciphertext, err := encrypt(plaintext, key)
    if err != nil {
        return err
    }

    return os.WriteFile(outputFile, ciphertext, 0644)
}

// Remove the encryption enchantment from a file
func decryptFile(inputFile, outputFile string, key []byte) error {
    ciphertext, err := os.ReadFile(inputFile)
    if err != nil {
        return err
    }

    plaintext, err := decrypt(ciphertext, key)
    if err != nil {
        return err
    }

    return os.WriteFile(outputFile, plaintext, 0644)
}

func main() {
    // Summon a magical key
    key := make([]byte, 32) // AES-256
    if _, err := rand.Read(key); err != nil {
        panic("Our magical key summoning failed!")
    }

    // Cast our encryption spell
    err := encryptFile("secret_scroll.txt", "encrypted_scroll.bin", key)
    if err != nil {
        panic("Our encryption spell fizzled!")
    }
    fmt.Println("Scroll successfully enchanted with secrecy!")

    // Remove the encryption enchantment
    err = decryptFile("encrypted_scroll.bin", "decrypted_scroll.txt", key)
    if err != nil {
        panic("Our decryption counter-spell backfired!")
    }
    fmt.Println("Scroll successfully disenchanted!")
}

package main

import (
    "crypto/ecdsa"
    "crypto/elliptic"
    "crypto/rand"
    "crypto/x509"
    "crypto/x509/pkix"
    "encoding/pem"
    "fmt"
    "math/big"
    "os"
    "time"
)

// Summon a magical key pair
func generateKey() (*ecdsa.PrivateKey, error) {
    return ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
}

// Create a mystical certificate
func createCertificate(template, parent *x509.Certificate, pub interface{}, priv interface{}) (*x509.Certificate, []byte, error) {
    certDER, err := x509.CreateCertificate(rand.Reader, template, parent, pub, priv)
    if err != nil {
        return nil, nil, err
    }

    cert, err := x509.ParseCertificate(certDER)
    if err != nil {
        return nil, nil, err
    }

    return cert, certDER, nil
}

// Summon a Certificate Authority
func generateCA() (*x509.Certificate, *ecdsa.PrivateKey, error) {
    caPrivKey, err := generateKey()
    if err != nil {
        return nil, nil, err
    }

    template := x509.Certificate{
        SerialNumber: big.NewInt(1),
        Subject: pkix.Name{
            Organization: []string{"Wizards' Council"},
        },
        NotBefore:             time.Now(),
        NotAfter:              time.Now().AddDate(10, 0, 0),
        KeyUsage:              x509.KeyUsageCertSign | x509.KeyUsageCRLSign,
        ExtKeyUsage:           []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth},
        BasicConstraintsValid: true,
        IsCA:                  true,
    }

    caCert, _, err := createCertificate(&template, &template, &caPrivKey.PublicKey, caPrivKey)
    if err != nil {
        return nil, nil, err
    }

    return caCert, caPrivKey, nil
}

// Generate a certificate for a magical domain
func generateCertificate(caCert *x509.Certificate, caPrivKey *ecdsa.PrivateKey, domain string) (*x509.Certificate, *ecdsa.PrivateKey, error) {
    certPrivKey, err := generateKey()
    if err != nil {
        return nil, nil, err
    }

    template := x509.Certificate{
        SerialNumber: big.NewInt(2),
        Subject: pkix.Name{
            Organization: []string{"Wizards' Guild"},
            CommonName:   domain,
        },
        NotBefore:   time.Now(),
        NotAfter:    time.Now().AddDate(1, 0, 0),
        KeyUsage:    x509.KeyUsageDigitalSignature | x509.KeyUsageKeyEncipherment,
        ExtKeyUsage: []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth},
        DNSNames:    []string{domain},
    }

    cert, _, err := createCertificate(&template, caCert, &certPrivKey.PublicKey, caPrivKey)
    if err != nil {
        return nil, nil, err
    }

    return cert, certPrivKey, nil
}

// Inscribe a certificate onto a magical parchment (PEM)
func saveCertificateToPEM(cert *x509.Certificate, filename string) error {
    certPEM := pem.EncodeToMemory(&pem.Block{Type: "CERTIFICATE", Bytes: cert.Raw})
    return os.WriteFile(filename, certPEM, 0644)
}

// Inscribe a private key onto a magical parchment (PEM)
func savePrivateKeyToPEM(privKey *ecdsa.PrivateKey, filename string) error {
    privKeyBytes, err := x509.MarshalECPrivateKey(privKey)
    if err != nil {
        return err
    }
    privKeyPEM := pem.EncodeToMemory(&pem.Block{Type: "EC PRIVATE KEY", Bytes: privKeyBytes})
    return os.WriteFile(filename, privKeyPEM, 0600)
}

func main() {
    // Summon the Certificate Authority
    caCert, caPrivKey, err := generateCA()
    if err != nil {
        panic("The CA summoning ritual failed!")
    }

    // Inscribe the CA certificate and private key
    err = saveCertificateToPEM(caCert, "ca_cert.pem")
    if err != nil {
        panic("Failed to inscribe the CA certificate!")
    }
    err = savePrivateKeyToPEM(caPrivKey, "ca_key.pem")
    if err != nil {
        panic("Failed to inscribe the CA private key!")
    }

    // Generate a certificate for a magical domain
    domain := "hogwarts.edu"
    cert, privKey, err := generateCertificate(caCert, caPrivKey, domain)
    if err != nil {
        panic("The domain certificate summoning failed!")
    }

    // Inscribe the domain certificate and private key
    err = saveCertificateToPEM(cert, "domain_cert.pem")
    if err != nil {
        panic("Failed to inscribe the domain certificate!")
    }
    err = savePrivateKeyToPEM(privKey, "domain_key.pem")
    if err != nil {
        panic("Failed to inscribe the domain private key!")
    }

    fmt.Println("The PKI summoning ritual was successful! CA and domain certificates have been manifested.")
}