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package main
import (
"crypto/rand"
"crypto/rsa"
"crypto/x509"
"crypto/x509/pkix"
"encoding/binary"
"encoding/hex"
"flag"
"fmt"
"math/big"
"os"
"os/exec"
"strings"
"time"
)
func ekPub() *rsa.PublicKey {
out, err := exec.Command("tpm_getpubek", "-z").Output()
if err != nil {
fmt.Fprintf(os.Stderr, "Error: %v\n", err)
os.Exit(1)
}
spl := strings.Split(string(out), "Public Key:")
hexKey := strings.NewReplacer(" ", "", "\n", "", "\r", "", "\t", "").Replace(spl[1])
modBytes, err := hex.DecodeString(hexKey)
if err != nil {
fmt.Fprintf(os.Stderr, "Error: %v\n", err)
os.Exit(1)
}
return &rsa.PublicKey{
N: new(big.Int).SetBytes(modBytes),
E: 65537,
}
}
func generateCertificate(pub *rsa.PublicKey) []byte {
priv, err := rsa.GenerateKey(rand.Reader, 2048)
if err != nil {
fmt.Fprintf(os.Stderr, "Error: %v\n", err)
os.Exit(1)
}
serialNumberLimit := new(big.Int).Lsh(big.NewInt(1), 128)
serialNumber, err := rand.Int(rand.Reader, serialNumberLimit)
if err != nil {
fmt.Fprintf(os.Stderr, "Error: %v\n", err)
os.Exit(1)
}
template := x509.Certificate{
SerialNumber: serialNumber,
Subject: pkix.Name{
Organization: []string{"Acme Co"},
},
NotBefore: time.Now(),
NotAfter: time.Now().AddDate(1, 0, 0),
KeyUsage: x509.KeyUsageKeyEncipherment | x509.KeyUsageDigitalSignature,
ExtKeyUsage: []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth},
BasicConstraintsValid: true,
}
derBytes, err := x509.CreateCertificate(rand.Reader, &template, &template, pub, priv)
if err != nil {
fmt.Fprintf(os.Stderr, "Error: %v\n", err)
os.Exit(1)
}
return derBytes
}
func main() {
flag.Parse()
certBytes := generateCertificate(ekPub())
f, err := os.OpenFile("/tmp/ekcert", os.O_RDWR|os.O_TRUNC|os.O_CREATE, 0755)
if err != nil {
fmt.Fprintf(os.Stderr, "Error: %v\n", err)
os.Exit(1)
}
// Write the header as documented in: TCG PC Specific Implementation
// Specification, section 7.3.2.
f.Write([]byte{0x10, 0x01, 0x00})
certLength := make([]byte, 2)
binary.BigEndian.PutUint16(certLength, uint16(len(certBytes)))
f.Write(certLength)
f.Write(certBytes)
f.Close()
cmd := exec.Command("tpm_nvwrite", "-z", "-i", "268496896", "-f", "/tmp/ekcert")
cmd.Stdout = os.Stdout
cmd.Stderr = os.Stderr
if err := cmd.Run(); err != nil {
fmt.Fprintf(os.Stderr, "Error: %v\n", err)
os.Exit(1)
}
}
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