Generate a self-signed certificate on the fly
I edited the answer to do the root certificate first and then issue an end entity certificate.
Here is some example of generating a self-signed certificate through Bouncy Castle:
public static X509Certificate2 GenerateSelfSignedCertificate(string subjectName, string issuerName, AsymmetricKeyParameter issuerPrivKey, int keyStrength = 2048)
{
// Generating Random Numbers
var randomGenerator = new CryptoApiRandomGenerator();
var random = new SecureRandom(randomGenerator);
// The Certificate Generator
var certificateGenerator = new X509V3CertificateGenerator();
// Serial Number
var serialNumber = BigIntegers.CreateRandomInRange(BigInteger.One, BigInteger.ValueOf(Int64.MaxValue), random);
certificateGenerator.SetSerialNumber(serialNumber);
// Signature Algorithm
const string signatureAlgorithm = "SHA256WithRSA";
certificateGenerator.SetSignatureAlgorithm(signatureAlgorithm);
// Issuer and Subject Name
var subjectDN = new X509Name(subjectName);
var issuerDN = new X509Name(issuerName);
certificateGenerator.SetIssuerDN(issuerDN);
certificateGenerator.SetSubjectDN(subjectDN);
// Valid For
var notBefore = DateTime.UtcNow.Date;
var notAfter = notBefore.AddYears(2);
certificateGenerator.SetNotBefore(notBefore);
certificateGenerator.SetNotAfter(notAfter);
// Subject Public Key
AsymmetricCipherKeyPair subjectKeyPair;
var keyGenerationParameters = new KeyGenerationParameters(random, keyStrength);
var keyPairGenerator = new RsaKeyPairGenerator();
keyPairGenerator.Init(keyGenerationParameters);
subjectKeyPair = keyPairGenerator.GenerateKeyPair();
certificateGenerator.SetPublicKey(subjectKeyPair.Public);
// Generating the Certificate
var issuerKeyPair = subjectKeyPair;
// Selfsign certificate
var certificate = certificateGenerator.Generate(issuerPrivKey, random);
// Corresponding private key
PrivateKeyInfo info = PrivateKeyInfoFactory.CreatePrivateKeyInfo(subjectKeyPair.Private);
// Merge into X509Certificate2
var x509 = new System.Security.Cryptography.X509Certificates.X509Certificate2(certificate.GetEncoded());
var seq = (Asn1Sequence)Asn1Object.FromByteArray(info.PrivateKey.GetDerEncoded());
if (seq.Count != 9)
throw new PemException("malformed sequence in RSA private key");
var rsa = new RsaPrivateKeyStructure(seq);
RsaPrivateCrtKeyParameters rsaparams = new RsaPrivateCrtKeyParameters(
rsa.Modulus, rsa.PublicExponent, rsa.PrivateExponent, rsa.Prime1, rsa.Prime2, rsa.Exponent1, rsa.Exponent2, rsa.Coefficient);
x509.PrivateKey = DotNetUtilities.ToRSA(rsaparams);
return x509;
}
public static AsymmetricKeyParameter GenerateCACertificate(string subjectName, int keyStrength = 2048)
{
// Generating Random Numbers
var randomGenerator = new CryptoApiRandomGenerator();
var random = new SecureRandom(randomGenerator);
// The Certificate Generator
var certificateGenerator = new X509V3CertificateGenerator();
// Serial Number
var serialNumber = BigIntegers.CreateRandomInRange(BigInteger.One, BigInteger.ValueOf(Int64.MaxValue), random);
certificateGenerator.SetSerialNumber(serialNumber);
// Signature Algorithm
const string signatureAlgorithm = "SHA256WithRSA";
certificateGenerator.SetSignatureAlgorithm(signatureAlgorithm);
// Issuer and Subject Name
var subjectDN = new X509Name(subjectName);
var issuerDN = subjectDN;
certificateGenerator.SetIssuerDN(issuerDN);
certificateGenerator.SetSubjectDN(subjectDN);
// Valid For
var notBefore = DateTime.UtcNow.Date;
var notAfter = notBefore.AddYears(2);
certificateGenerator.SetNotBefore(notBefore);
certificateGenerator.SetNotAfter(notAfter);
// Subject Public Key
AsymmetricCipherKeyPair subjectKeyPair;
var keyGenerationParameters = new KeyGenerationParameters(random, keyStrength);
var keyPairGenerator = new RsaKeyPairGenerator();
keyPairGenerator.Init(keyGenerationParameters);
subjectKeyPair = keyPairGenerator.GenerateKeyPair();
certificateGenerator.SetPublicKey(subjectKeyPair.Public);
// Generating the Certificate
var issuerKeyPair = subjectKeyPair;
// Selfsign certificate
var certificate = certificateGenerator.Generate(issuerKeyPair.Private, random);
var x509 = new System.Security.Cryptography.X509Certificates.X509Certificate2(certificate.GetEncoded());
// Add CA certificate to Root store
addCertToStore(cert, StoreName.Root, StoreLocation.CurrentUser);
return issuerKeyPair.Private;
}
And add to the store (your code slightly modified):
public static bool addCertToStore(System.Security.Cryptography.X509Certificates.X509Certificate2 cert, System.Security.Cryptography.X509Certificates.StoreName st, System.Security.Cryptography.X509Certificates.StoreLocation sl)
{
bool bRet = false;
try
{
X509Store store = new X509Store(st, sl);
store.Open(OpenFlags.ReadWrite);
store.Add(cert);
store.Close();
}
catch
{
}
return bRet;
}
And usage:
var caPrivKey = GenerateCACertificate("CN=root ca");
var cert = GenerateSelfSignedCertificate("CN=127.0.01", "CN=root ca", caPrivKey);
addCertToStore(cert, StoreName.My, StoreLocation.CurrentUser);
I have not compiled this example code after @wakeupneo comments. @wakeupneo, you might have to slightly edit the code and add proper extensions to each certificate.
How to generate a self-signed SSL certificate using OpenSSL?
You can do that in one command:
openssl req -x509 -newkey rsa:4096 -keyout key.pem -out cert.pem -sha256 -days 365
You can also add -nodes (short for "no DES") if you don't want to protect your private key with a passphrase. Otherwise it will prompt you for "at least a 4 character" password.
The days parameter (365) you can replace with any number to affect the expiration date. It will then prompt you for things like "Country Name", but you can just hit Enter and accept the defaults.
Add -subj '/CN=localhost' to suppress questions about the contents of the certificate (replace localhost with your desired domain).
Self-signed certificates are not validated with any third party unless you import them to the browsers previously. If you need more security, you should use a certificate signed by a certificate authority (CA).
How to generate a self signed certificate programmatically in Android and use it for an https server
The following solution works for generating a self signed certificate using Spongy Castle (Bouncy Castle) on Android. I've tested the code with Android 10 (Q) and Android Pie.
This code is a modified version of Netty's io.netty.handler.ssl.util.SelfSignedCertificate. The original version requires Bouncy Castle; which does not seem to be present by default on Android 10 resulting in a java.lang.NoClassDefFoundError: org.spongycastle.jce.provider.BouncyCastleProvider. Hence, I had to copy over the code and modify it to get it working with Spongy Castle.
build.gradle
dependencies {
implementation 'com.madgag.spongycastle:bcpkix-jdk15on:1.58.0.0'
}
SelfSignedCertificate.java
import android.util.Base64;
import android.util.Log;
import org.spongycastle.asn1.x500.X500Name;
import org.spongycastle.cert.X509CertificateHolder;
import org.spongycastle.cert.X509v3CertificateBuilder;
import org.spongycastle.cert.jcajce.JcaX509CertificateConverter;
import org.spongycastle.cert.jcajce.JcaX509v3CertificateBuilder;
import org.spongycastle.jce.provider.BouncyCastleProvider;
import org.spongycastle.operator.ContentSigner;
import org.spongycastle.operator.jcajce.JcaContentSignerBuilder;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.math.BigInteger;
import java.nio.charset.Charset;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.NoSuchAlgorithmException;
import java.security.PrivateKey;
import java.security.Provider;
import java.security.SecureRandom;
import java.security.cert.CertificateEncodingException;
import java.security.cert.CertificateException;
import java.security.cert.CertificateFactory;
import java.security.cert.X509Certificate;
import java.util.Date;
public final class SelfSignedCertificate {
private static final String TAG = SelfSignedCertificate.class.getSimpleName();
/**
* Current time minus 1 year, just in case software clock goes back due to time synchronization
*/
private static final Date DEFAULT_NOT_BEFORE = new Date(System.currentTimeMillis() - 86400000L * 365);
/**
* The maximum possible value in X.509 specification: 9999-12-31 23:59:59
*/
private static final Date DEFAULT_NOT_AFTER = new Date(253402300799000L);
/**
* FIPS 140-2 encryption requires the key length to be 2048 bits or greater.
* Let's use that as a sane default but allow the default to be set dynamically
* for those that need more stringent security requirements.
*/
private static final int DEFAULT_KEY_LENGTH_BITS = 2048;
/**
* FQDN to use if none is specified.
*/
private static final String DEFAULT_FQDN = "example.com";
/**
* 7-bit ASCII, as known as ISO646-US or the Basic Latin block of the
* Unicode character set
*/
private static final Charset US_ASCII = Charset.forName("US-ASCII");
private static final Provider provider = new BouncyCastleProvider();
private final File certificate;
private final File privateKey;
private final X509Certificate cert;
private final PrivateKey key;
/**
* Creates a new instance.
*/
public SelfSignedCertificate() throws CertificateException {
this(DEFAULT_NOT_BEFORE, DEFAULT_NOT_AFTER);
}
/**
* Creates a new instance.
*
* @param notBefore Certificate is not valid before this time
* @param notAfter Certificate is not valid after this time
*/
public SelfSignedCertificate(Date notBefore, Date notAfter) throws CertificateException {
this("example.com", notBefore, notAfter);
}
/**
* Creates a new instance.
*
* @param fqdn a fully qualified domain name
*/
public SelfSignedCertificate(String fqdn) throws CertificateException {
this(fqdn, DEFAULT_NOT_BEFORE, DEFAULT_NOT_AFTER);
}
/**
* Creates a new instance.
*
* @param fqdn a fully qualified domain name
* @param notBefore Certificate is not valid before this time
* @param notAfter Certificate is not valid after this time
*/
public SelfSignedCertificate(String fqdn, Date notBefore, Date notAfter) throws CertificateException {
// Bypass entropy collection by using insecure random generator.
// We just want to generate it without any delay because it's for testing purposes only.
this(fqdn, new SecureRandom(), DEFAULT_KEY_LENGTH_BITS, notBefore, notAfter);
}
/**
* Creates a new instance.
*
* @param fqdn a fully qualified domain name
* @param random the {@link java.security.SecureRandom} to use
* @param bits the number of bits of the generated private key
*/
public SelfSignedCertificate(String fqdn, SecureRandom random, int bits) throws CertificateException {
this(fqdn, random, bits, DEFAULT_NOT_BEFORE, DEFAULT_NOT_AFTER);
}
/**
* Creates a new instance.
*
* @param fqdn a fully qualified domain name
* @param random the {@link java.security.SecureRandom} to use
* @param bits the number of bits of the generated private key
* @param notBefore Certificate is not valid before this time
* @param notAfter Certificate is not valid after this time
*/
public SelfSignedCertificate(String fqdn, SecureRandom random, int bits, Date notBefore, Date notAfter)
throws CertificateException {
// Generate an RSA key pair.
final KeyPair keypair;
try {
KeyPairGenerator keyGen = KeyPairGenerator.getInstance("RSA");
keyGen.initialize(bits, random);
keypair = keyGen.generateKeyPair();
} catch (NoSuchAlgorithmException e) {
// Should not reach here because every Java implementation must have RSA key pair generator.
throw new Error(e);
}
String[] paths;
try {
// Try Bouncy Castle if the current JVM didn't have sun.security.x509.
paths = generateCertificate(fqdn, keypair, random, notBefore, notAfter);
} catch (Throwable t2) {
Log.d(TAG, "Failed to generate a self-signed X.509 certificate using Bouncy Castle:", t2);
throw new CertificateException("No provider succeeded to generate a self-signed certificate. See debug log for the root cause.", t2);
}
certificate = new File(paths[0]);
privateKey = new File(paths[1]);
key = keypair.getPrivate();
FileInputStream certificateInput = null;
try {
certificateInput = new FileInputStream(certificate);
cert = (X509Certificate) CertificateFactory.getInstance("X509").generateCertificate(certificateInput);
} catch (Exception e) {
throw new CertificateEncodingException(e);
} finally {
if (certificateInput != null) {
try {
certificateInput.close();
} catch (IOException e) {
Log.w(TAG, "Failed to close a file: " + certificate, e);
}
}
}
}
/**
* Returns the generated X.509 certificate file in PEM format.
*/
public File certificate() {
return certificate;
}
/**
* Returns the generated RSA private key file in PEM format.
*/
public File privateKey() {
return privateKey;
}
/**
* Returns the generated X.509 certificate.
*/
public X509Certificate cert() {
return cert;
}
/**
* Returns the generated RSA private key.
*/
public PrivateKey key() {
return key;
}
/**
* Deletes the generated X.509 certificate file and RSA private key file.
*/
public void delete() {
safeDelete(certificate);
safeDelete(privateKey);
}
private static String[] generateCertificate(String fqdn, KeyPair keypair, SecureRandom random, Date notBefore, Date notAfter)
throws Exception {
PrivateKey key = keypair.getPrivate();
// Prepare the information required for generating an X.509 certificate.
X500Name owner = new X500Name("CN=" + fqdn);
X509v3CertificateBuilder builder = new JcaX509v3CertificateBuilder(
owner, new BigInteger(64, random), notBefore, notAfter, owner, keypair.getPublic());
ContentSigner signer = new JcaContentSignerBuilder("SHA256WithRSAEncryption").build(key);
X509CertificateHolder certHolder = builder.build(signer);
X509Certificate cert = new JcaX509CertificateConverter().setProvider(provider).getCertificate(certHolder);
cert.verify(keypair.getPublic());
return newSelfSignedCertificate(fqdn, key, cert);
}
private static String[] newSelfSignedCertificate(String fqdn, PrivateKey key, X509Certificate cert) throws IOException, CertificateEncodingException {
String keyText = "-----BEGIN PRIVATE KEY-----\n" + Base64.encodeToString(key.getEncoded(), Base64.DEFAULT) + "\n-----END PRIVATE KEY-----\n";
File keyFile = File.createTempFile("keyutil_" + fqdn + '_', ".key");
keyFile.deleteOnExit();
OutputStream keyOut = new FileOutputStream(keyFile);
try {
keyOut.write(keyText.getBytes(US_ASCII));
keyOut.close();
keyOut = null;
} finally {
if (keyOut != null) {
safeClose(keyFile, keyOut);
safeDelete(keyFile);
}
}
String certText = "-----BEGIN CERTIFICATE-----\n" + Base64.encodeToString(cert.getEncoded(), Base64.DEFAULT) + "\n-----END CERTIFICATE-----\n";
File certFile = File.createTempFile("keyutil_" + fqdn + '_', ".crt");
certFile.deleteOnExit();
OutputStream certOut = new FileOutputStream(certFile);
try {
certOut.write(certText.getBytes(US_ASCII));
certOut.close();
certOut = null;
} finally {
if (certOut != null) {
safeClose(certFile, certOut);
safeDelete(certFile);
safeDelete(keyFile);
}
}
return new String[]{certFile.getPath(), keyFile.getPath()};
}
private static void safeDelete(File certFile) {
if (!certFile.delete()) {
Log.w(TAG, "Failed to delete a file: " + certFile);
}
}
private static void safeClose(File keyFile, OutputStream keyOut) {
try {
keyOut.close();
} catch (IOException e) {
Log.w(TAG, "Failed to close a file: " + keyFile, e);
}
}
}
Usage
private SslContext getSslContext() throws CertificateException, SSLException {
SelfSignedCertificate ssc = new SelfSignedCertificate(BuildConfig.APPLICATION_ID);
return SslContextBuilder.forServer(ssc.certificate(), ssc.privateKey()).protocols("TLSv1.2").build();
}
I pass this SslContext to create the ChannelPipeline for starting a Netty server with HTTPS support, but you may use the generated certificate any way you like.
Generate Trusted Self-Signed Certificate in .NetCore Console Application
The specific problem is that .NET Core does not support the setter on cert.PrivateKey.
The closest analog is cert.CopyWithPrivateKey, but the code is different. Rather than
cert.PrivateKey = key;
return cert;
you need something more like
return cert.CopyWithPrivateKey(key);
because CopyWithPrivateKey makes a new X509Certificate2 object, leaving the target object unaltered.
FWIW, you can do the entirety of the cert creation without extra dependencies now, as shown in Generate and Sign Certificate Request using pure .net Framework.
Generate Self-signed certificate with Root CA Signer
The ultimate solution in my case, avoiding makecert and openssl was to use Powershell and BouncyCastle. I forked the PSBouncyCastle repo from PSBouncyCastle by RLipscombe and pushed 1.8.1 Bouncy Castle in. My forked version is the one I've used for the script, the fork resides at Forked: PSBouncyCastle.New.
I then used StackOverflow: C# Generate Certificates on the Fly as inspiration to write the following powershell below, I will be adding this to my GitHub and commenting, and I will amend this as soon as I do:
Import-Module -Name PSBouncyCastle.New
function New-SelfSignedCertificate {
[CmdletBinding()]
param (
[string]$SubjectName,
[string]$FriendlyName = "New Certificate",
[object]$Issuer,
[bool]$IsCA = $false,
[int]$KeyStrength = 2048,
[int]$ValidYears = 2,
[hashtable]$EKU = @{}
)
# Needed generators
$random = New-SecureRandom
$certificateGenerator = New-CertificateGenerator
if($Issuer -ne $null -and $Issuer.HasPrivateKey -eq $true)
{
$IssuerName = $Issuer.IssuerName.Name
$IssuerPrivateKey = $Issuer.PrivateKey
}
# Create and set a random certificate serial number
$serial = New-SerialNumber -Random $random
$certificateGenerator.SetSerialNumber($serial)
# The signature algorithm
$certificateGenerator.SetSignatureAlgorithm('SHA256WithRSA')
# Basic Constraints - certificate is allowed to be used as intermediate.
# Powershell requires either a $null or reassignment or it will return this from the function
$certificateGenerator = Add-BasicConstraints -isCertificateAuthority $IsCA -certificateGenerator $certificateGenerator
# Key Usage
if($EKU.Count -gt 0)
{
$certificateGenerator = $certificateGenerator | Add-ExtendedKeyUsage @EKU
}
# Create and set the Issuer and Subject name
$subjectDN = New-X509Name -Name ($SubjectName)
if($Issuer -ne $null) {
$IssuerDN = New-X509Name -Name ($IssuerName)
}
else
{
$IssuerDN = New-X509Name -Name ($SubjectName)
}
$certificateGenerator.SetSubjectDN($subjectDN)
$certificateGenerator.SetIssuerDN($IssuerDN)
# Authority Key and Subject Identifier
if($Issuer -ne $null)
{
$IssuerKeyPair = ConvertTo-BouncyCastleKeyPair -PrivateKey $IssuerPrivateKey
$IssuerSerial = [Org.BouncyCastle.Math.BigInteger]$Issuer.GetSerialNumber()
$authorityKeyIdentifier = New-AuthorityKeyIdentifier -name $Issuer.IssuerName.Name -publicKey $IssuerKeyPair.Public -serialNumber $IssuerSerial
$certificateGenerator = Add-AuthorityKeyIdentifier -certificateGenerator $certificateGenerator -authorityKeyIdentifier $authorityKeyIdentifier
}
# Validity range of the certificate
[DateTime]$notBefore = (Get-Date).AddDays(-1)
if($ValidYears -gt 0) {
[DateTime]$notAfter = $notBefore.AddYears($ValidYears)
}
$certificateGenerator.SetNotBefore($notBefore)
$certificateGenerator.SetNotAfter($notAfter)
# Subject public key ~and private
$subjectKeyPair = New-KeyPair -Strength $keyStrength -Random $random
if($IssuerPrivateKey -ne $null)
{
$IssuerKeyPair = [Org.BouncyCastle.Security.DotNetUtilities]::GetKeyPair($IssuerPrivateKey)
}
else
{
$IssuerKeyPair = $subjectKeyPair
}
$certificateGenerator.SetPublicKey($subjectKeyPair.Public)
# Create the Certificate
$IssuerKeyPair = $subjectKeyPair
$certificate = $certificateGenerator.Generate($IssuerKeyPair.Private, $random)
# At this point you have the certificate and need to convert it and export, I return the private key for signing the next cert
$pfxCertificate = ConvertFrom-BouncyCastleCertificate -certificate $certificate -subjectKeyPair $subjectKeyPair -friendlyName $FriendlyName
return $pfxCertificate
}
A few examples of usage for this powershell would be:
Generate a Root CA
$TestRootCA = New-SelfSignedCertificate -subjectName "CN=TestRootCA" -IsCA $true
Export-Certificate -Certificate $test -OutputFile "TestRootCA.pfx" -X509ContentType Pfx
Generate a Standard Self Signed
$TestSS = New-SelfSignedCertificate -subjectName "CN=TestLocal"
Export-Certificate -Certificate $TestSS -OutputFile "TestLocal.pfx" -X509ContentType Pfx
Generate a certificate, signing with a root certificate
$TestRootCA = New-SelfSignedCertificate -subjectName "CN=TestRootCA" -IsCA $true
$TestSigned = New-SelfSignedCertificate -subjectName "CN=TestSignedByRoot" -issuer $TestRootCA
Export-Certificate -Certificate $test -OutputFile "TestRootCA.pfx" -X509ContentType Pfx
Export-Certificate -Certificate $test -OutputFile "TestRootCA.pfx" -X509ContentType Pfx
Generate a Self-Signed with Specific Usage
$TestServerCert = New-SelfSignedCertificate -subjectName "CN=TestServerCert" -EKU @{ "ServerAuthentication" = $true }
Note that the -EKU parameter accepts via splatting, it does this to ensure that anything added to Add-ExtendedKeyUsage is validly passed. It accepts the following certificate usages:
- DigitalSignature
- NonRepudiation
- KeyEncipherment
- DataEncipherment
- KeyAgreement
- KeyCertSign
- CrlSign
- EncipherOnly
- DecipherOnly
This fits my need and seems to work across all Windows Platforms we are using for dynamic environments.
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