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crypto_utils.go
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crypto_utils.go
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package ios
import (
"crypto"
"crypto/rand"
"crypto/rsa"
"crypto/sha1"
"crypto/x509"
"crypto/x509/pkix"
"encoding/asn1"
"encoding/pem"
"errors"
"github.com/fullsailor/pkcs7"
"math/big"
"time"
)
const bitSize = 2048
func createRootCertificate(publicKeyBytes []byte) ([]byte, []byte, []byte, []byte, []byte, error) {
rootKeyPair, rootCertBytes, rootCert, err := createRootCert()
if err != nil {
return nil, nil, nil, nil, nil, err
}
hostKeyPair, hostCertBytes, err := createHostCert(rootCert, rootKeyPair)
if err != nil {
return nil, nil, nil, nil, nil, err
}
deviceCertBytes, err := createDeviceCert(publicKeyBytes, rootCert, rootKeyPair)
if err != nil {
return nil, nil, nil, nil, nil, err
}
return certBytesToPEM(rootCertBytes), certBytesToPEM(hostCertBytes), certBytesToPEM(deviceCertBytes), savePEMKey(rootKeyPair), savePEMKey(hostKeyPair), nil
}
func createRootCert() (*rsa.PrivateKey, []byte, *x509.Certificate, error) {
rootKeyPair, err := rsa.GenerateKey(rand.Reader, bitSize)
if err != nil {
return nil, nil, nil, err
}
var b big.Int
b.SetInt64(0)
rootCertTemplate := x509.Certificate{
SerialNumber: &b,
Subject: pkix.Name{},
NotBefore: time.Now(),
NotAfter: time.Now().AddDate(10, 0, 0),
SignatureAlgorithm: x509.SHA1WithRSA,
BasicConstraintsValid: true,
IsCA: true,
}
digestString, err := computeSKIKey(&rootKeyPair.PublicKey)
if err != nil {
return nil, nil, nil, err
}
// reminder: you cannot use the ExtraExtentions field here because for some reason
// that created invalid certificates that throw errors when I try to parse them
// with golang.
rootCertTemplate.Extensions = append(rootCertTemplate.Extensions, pkix.Extension{
Id: []int{2, 5, 29, 14},
Value: digestString,
})
rootCertBytes, err := x509.CreateCertificate(rand.Reader, &rootCertTemplate, &rootCertTemplate, &rootKeyPair.PublicKey, rootKeyPair)
if err != nil {
return nil, nil, nil, err
}
rootCert, err := x509.ParseCertificate(rootCertBytes)
if err != nil {
return nil, nil, nil, err
}
return rootKeyPair, rootCertBytes, rootCert, nil
}
func createHostCert(rootCert *x509.Certificate, rootKeyPair *rsa.PrivateKey) (*rsa.PrivateKey, []byte, error) {
var b big.Int
b.SetInt64(0)
hostCertTemplate := x509.Certificate{
SerialNumber: &b,
Subject: pkix.Name{},
NotBefore: time.Now(),
NotAfter: time.Now().AddDate(10, 0, 0),
SignatureAlgorithm: x509.SHA1WithRSA,
KeyUsage: x509.KeyUsageKeyEncipherment | x509.KeyUsageDigitalSignature,
BasicConstraintsValid: true,
IsCA: false,
}
hostKeyPair, err := rsa.GenerateKey(rand.Reader, bitSize)
if err != nil {
return nil, nil, err
}
hostdigestString, err := computeSKIKey(&hostKeyPair.PublicKey)
if err != nil {
return nil, nil, err
}
hostCertTemplate.Extensions = append(hostCertTemplate.Extensions, pkix.Extension{
Id: []int{2, 5, 29, 14},
Value: hostdigestString,
},
)
hostCertBytes, err := x509.CreateCertificate(rand.Reader, &hostCertTemplate, rootCert, &hostKeyPair.PublicKey, rootKeyPair)
if err != nil {
return nil, nil, err
}
return hostKeyPair, hostCertBytes, nil
}
func createDeviceCert(publicKeyBytes []byte, rootCert *x509.Certificate, rootKeyPair *rsa.PrivateKey) ([]byte, error) {
block, _ := pem.Decode(publicKeyBytes)
if block == nil {
return nil, errors.New("failed to parse PEM block containing the public key")
}
var devicePublicKey rsa.PublicKey
_, err := asn1.Unmarshal(block.Bytes, &devicePublicKey)
if err != nil {
return nil, err
}
var b big.Int
b.SetInt64(0)
deviceCertTemplate := x509.Certificate{
SerialNumber: &b,
Subject: pkix.Name{},
NotBefore: time.Now(),
NotAfter: time.Now().AddDate(10, 0, 0),
SignatureAlgorithm: x509.SHA1WithRSA,
KeyUsage: x509.KeyUsageKeyEncipherment | x509.KeyUsageDigitalSignature,
BasicConstraintsValid: true,
IsCA: false,
}
devicePublicKeyDigest, err := computeSKIKey(&devicePublicKey)
if err != nil {
return nil, err
}
deviceCertTemplate.Extensions = append(deviceCertTemplate.Extensions, pkix.Extension{
Id: []int{2, 5, 29, 14},
Value: devicePublicKeyDigest,
},
)
deviceCertBytes, err := x509.CreateCertificate(rand.Reader, &deviceCertTemplate, rootCert, &devicePublicKey, rootKeyPair)
if err != nil {
return nil, err
}
return deviceCertBytes, nil
}
type subjectPublicKeyInfo struct {
Algorithm pkix.AlgorithmIdentifier
SubjectPublicKey asn1.BitString
}
func computeSKIKey(pub *rsa.PublicKey) ([]byte, error) {
encodedPub, err := x509.MarshalPKIXPublicKey(pub)
if err != nil {
return nil, err
}
var subPKI subjectPublicKeyInfo
_, err = asn1.Unmarshal(encodedPub, &subPKI)
if err != nil {
return nil, err
}
pubHash := sha1.Sum(subPKI.SubjectPublicKey.Bytes)
return pubHash[:], nil
}
func certBytesToPEM(certBytes []byte) []byte {
pemCert := pem.EncodeToMemory(&pem.Block{Type: "CERTIFICATE", Bytes: certBytes})
return pemCert
}
func savePEMKey(key *rsa.PrivateKey) []byte {
privateKeyBytes := x509.MarshalPKCS1PrivateKey(key)
privateKeyPem := pem.EncodeToMemory(
&pem.Block{
Type: "RSA PRIVATE KEY",
Bytes: privateKeyBytes,
},
)
return privateKeyPem
}
func Sign(challengeBytes []byte, cert *x509.Certificate, supervisedPrivateKey interface{}) ([]byte, error) {
sd, err := pkcs7.NewSignedData(challengeBytes)
if err != nil {
return []byte{}, err
}
err = sd.AddSigner(cert, supervisedPrivateKey.(crypto.Signer), pkcs7.SignerInfoConfig{})
if err != nil {
return []byte{}, err
}
return sd.Finish()
}