我目前正在使用两个运行Ubuntu的Azure虚拟机在一个标准Azure负载平衡器后面设置一个高可用性（HA）环境。现在，我知道标准负载均衡器仅是第4层，这意味着它无法进行SSL卸载。
两个VM都运行.NET Core Web API。显然，他们每个人都需要SSL证书来处理来自负载均衡器的SSL连接。
我知道我可以购买SSL证书，只需设置Kestrel即可在Web API本身上使用该证书，但是我想要免费的证书。我知道另一种选择是使用Nginx服务器生成证书，然后将证书复制到Web API，但这意味着我需要每3个月重复一次此过程，这是一个很大的痛苦，因为这意味着我将在我使HA群集脱机以更新证书。
有人知道在负载均衡器后面的两个VM上使用Lets Encrypt的方法吗？
答案 0 :(得分：1)
好的，所以我正确地回答了上面的问题。它要求我编写一个实用程序，该实用程序使用 DNS 验证自动续订我的Lets Encrypt证书。使用Azure DNS或具有API的其他DNS提供程序非常重要，因为您将需要能够使用API或与提供程序的某些其他接口直接修改DNS记录。
我正在使用Azure DNS，它正在为我管理整个域，因此下面的代码适用于Azure DNS，但是您可以修改API以使其与您选择的具有某种API的任何提供程序一起使用。
第二部分是在我的高可用性（HA）群集中不造成任何停机。因此，我要做的是将证书写入数据库，然后在启动我的VM时动态读取它。因此，基本上，每次Kestrel启动时，它都会从数据库读取证书，然后使用该证书。
您将需要在数据库中添加以下模型，以便将实际的证书详细信息存储在某处。
public class Certificate
{
[Key]
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public long Id { get; set; }
public string FullChainPem { get; set; }
public string CertificatePfx { get; set; }
public string CertificatePassword { get; set; }
public DateTime CertificateExpiry { get; set; }
public DateTime? CreatedAt { get; set; }
public DateTime? UpdatedAt { get; set; }
}
创建模型后，需要将其放置在上下文中，如下所示：
public DbSet<Certificate> Certificates { get; set; }
在应用程序服务器上，您希望使用Kestrel充当Web服务器，然后从数据库动态加载证书。因此，将以下内容添加到您的CreateWebHostBuilder方法中。请务必在.UseStartup<Startup>()
.UseKestrel(opt = >{
//Get the application services
var applicationServices = opt.ApplicationServices;
//Create and use scope
using(var scope = applicationServices.CreateScope()) {
//Get the database context to work with
var context = scope.ServiceProvider.GetService < DBContext > ();
//Get the certificate
var certificate = context.Certificates.Last();
var pfxBytes = Convert.FromBase64String(certificate.CertificatePfx);
var pfxPassword = certificate.CertificatePassword;
//Create the certificate
var cert = new X509Certificate2(pfxBytes, pfxPassword);
//Listen on the specified IP and port
opt.Listen(IPAddress.Any, 443, listenOpts = >{
//Use HTTPS
listenOpts.UseHttps(cert);
});
}
});
这就是解决方案的关键所在。它处理证书请求，质询，DNS验证，然后处理证书的存储。它还将自动重新启动Azure中使用证书的每个VM实例，以便它们提取新证书。
Main逻辑如下，它将检查是否需要续订证书。
static void Main(string[] args) {
while (true) {
//Get the latest certificate in the DB for the servers
var lastCertificate = _db.Certificates.LastOrDefault();
//Check if the expiry date of last certificate is more than a month away
if (lastCertificate != null && (lastCertificate.CertificateExpiry - DateTime.Now).TotalDays > 31) {
//Log out some info
Console.WriteLine($ "[{DateTime.Now}] - Certificate still valid, sleeping for a day.");
//Sleep the thread
Thread.Sleep(TimeSpan.FromDays(1));
}
else {
//Renew the certificates
RenewCertificates();
}
}
}
好的，这要花很多时间，但如果将其分解，实际上很简单
实际的RenewCertificates方法如下：
/// <summary>
/// Method that will renew the domain certificates and update the database with them
/// </summary>
public static void RenewCertificates() {
Console.WriteLine($ "[{DateTime.Now}] - Starting certificate renewal.");
//Instantiate variables
AcmeContext acme;
IAccountContext account;
//Try and get the setting value for ACME Key
var acmeKey = _db.Settings.FirstOrDefault(s = >s.Key == "ACME");
//Check if acme key is null
if (acmeKey == null) {
//Set the ACME servers to use
#if DEBUG
acme = new AcmeContext(WellKnownServers.LetsEncryptStagingV2);
#else
acme = new AcmeContext(WellKnownServers.LetsEncryptV2);
#endif
//Create the new account
account = acme.NewAccount("yourname@yourdomain.tld", true).Result;
//Save the key to the DB to be used
_db.Settings.Add(new Setting {
Key = "ACME",
Value = acme.AccountKey.ToPem()
});
//Save DB changes
_db.SaveChanges();
}
else {
//Get the account key from PEM
var accountKey = KeyFactory.FromPem(acmeKey.Value);
//Set the ACME servers to use
#if DEBUG
acme = new AcmeContext(WellKnownServers.LetsEncryptStagingV2, accountKey);
#else
acme = new AcmeContext(WellKnownServers.LetsEncryptV2, accountKey);
#endif
//Get the actual account
account = acme.Account().Result;
}
//Create an order for wildcard domain and normal domain
var order = acme.NewOrder(new[] {
"*.yourdomain.tld",
"yourdomain.tld"
}).Result;
//Generate the challenges for the domains
var authorizations = order.Authorizations().Result;
//Error flag
var hasFailed = false;
foreach(var authorization in authorizations) {
//Get the DNS challenge for the authorization
var dnsChallenge = authorization.Dns().Result;
//Get the DNS TXT
var dnsTxt = acme.AccountKey.DnsTxt(dnsChallenge.Token);
Console.WriteLine($ "[{DateTime.Now}] - Received DNS challenge data.");
//Set the DNS record
Azure.SetAcmeTxtRecord(dnsTxt);
Console.WriteLine($ "[{DateTime.Now}] - Updated DNS challenge data.");
Console.WriteLine($ "[{DateTime.Now}] - Waiting 1 minute before checking status.");
dnsChallenge.Validate();
//Wait 1 minute
Thread.Sleep(TimeSpan.FromMinutes(1));
//Check the DNS challenge
var valid = dnsChallenge.Validate().Result;
//If the verification fails set failed flag
if (valid.Status != ChallengeStatus.Valid) hasFailed = true;
}
//Check whether challenges failed
if (hasFailed) {
Console.WriteLine($ "[{DateTime.Now}] - DNS challenge(s) failed, retrying.");
//Recurse
RenewCertificates();
return;
}
else {
Console.WriteLine($ "[{DateTime.Now}] - DNS challenge(s) successful.");
//Generate a private key
var privateKey = KeyFactory.NewKey(KeyAlgorithm.ES256);
//Generate certificate
var cert = order.Generate(new CsrInfo {
CountryName = "ZA",
State = "Gauteng",
Locality = "Pretoria",
Organization = "Your Organization",
OrganizationUnit = "Production",
},
privateKey).Result;
Console.WriteLine($ "[{DateTime.Now}] - Certificate generated successfully.");
//Get the full chain
var fullChain = cert.ToPem();
//Generate password
var pass = Guid.NewGuid().ToString();
//Export the pfx
var pfxBuilder = cert.ToPfx(privateKey);
var pfx = pfxBuilder.Build("yourdomain.tld", pass);
//Create database entry
_db.Certificates.Add(new Certificate {
FullChainPem = fullChain,
CertificatePfx = Convert.ToBase64String(pfx),
CertificatePassword = pass,
CertificateExpiry = DateTime.Now.AddMonths(2)
});
//Save changes
_db.SaveChanges();
Console.WriteLine($ "[{DateTime.Now}] - Database updated with new certificate.");
Console.WriteLine($ "[{DateTime.Now}] - Restarting VMs.");
//Restart the VMS
Azure.RestartAllVms();
}
}
无论我叫Azure是什么，您都需要编写API包装程序来设置DNS TXT记录，然后才能从托管提供商重新启动VM。我的工作全都在Azure上，因此操作非常简单。这是Azure代码：
/// <summary>
/// Method that will set the TXT record value of the ACME challenge
/// </summary>
/// <param name="txtValue">Value for the TXT record</param>
/// <returns>Whether call was successful or not</returns>
public static bool SetAcmeTxtRecord(string txtValue) {
//Set the zone endpoint
const string url = "https://management.azure.com/subscriptions/{subId}/resourceGroups/{resourceGroup}/providers/Microsoft.Network/dnsZones/{dnsZone}/txt/_acme-challenge?api-version=2018-03-01-preview";
//Authenticate API
AuthenticateApi();
//Build up the body to put
var body = $ "{{\"properties\": {{\"metadata\": {{}},\"TTL\": 225,\"TXTRecords\": [{{\"value\": [\"{txtValue}\"]}}]}}}}";
//Build up the string content
var content = new StringContent(body, Encoding.UTF8, "application/json");
//Create the response
var response = client.PutAsync(url, content).Result;
//Return the response
return response.IsSuccessStatusCode;
}
我希望这能够帮助与我一样处境艰难的其他人。