TLS with selfsigned certificate - ssl

I'm trying to establish a TLS connection with the use of a self signed server certificate.
I generated the certificate with this example code: http://golang.org/src/pkg/crypto/tls/generate_cert.go
My relevant client code looks like that:
// server cert is self signed -> server_cert == ca_cert
CA_Pool := x509.NewCertPool()
severCert, err := ioutil.ReadFile("./cert.pem")
if err != nil {
log.Fatal("Could not load server certificate!")
}
CA_Pool.AppendCertsFromPEM(severCert)
config := tls.Config{RootCAs: CA_Pool}
conn, err := tls.Dial("tcp", "127.0.0.1:8000", &config)
if err != nil {
log.Fatalf("client: dial: %s", err)
}
And the relevant server code like that:
cert, err := tls.LoadX509KeyPair("./cert.pem", "./key.pem")
config := tls.Config{Certificates: []tls.Certificate{cert}}
listener, err := tls.Listen("tcp", "127.0.0.1:8000", &config)
for {
conn, err := listener.Accept()
if err != nil {
log.Printf("server: accept: %s", err)
break
}
log.Printf("server: accepted from %s", conn.RemoteAddr())
go handleConnection(conn)
}
Because the server certificate is self signed is use the same certificate for the server and the clients CA_Pool however this does not seem to work since i always get this error:
client: dial: x509: certificate signed by unknown authority
(possibly because of "x509: invalid signature: parent certificate
cannot sign this kind of certificate" while trying to verify
candidate authority certificate "serial:0")
What's my mistake?

It finally worked with the go built in x509.CreateCertificate,
the problem was that I did not set the IsCA:true flag,
I only set the x509.KeyUsageCertSign which made creating the self signed certificate work, but crashed while verifying the cert chain.

The problem is that you need a CA certificate in the server-side config, and this CA must have signed the server's certificate.
I have written some Go code that will generate a CA certificate, but it hasn't been reviewed by anyone and is mostly a toy for playing around with client certs. The safest bet is probably to use openssl ca to generate and sign the certificate. The basic steps will be:
Generate a CA Certificate
Generate a Server key
Sign the Server key with the CA certificate
Add the CA Certificate to the client's tls.Config RootCAs
Set up the server's tls.Config with the Server key and signed certificate.

Kyle, is correct. This tool will do what you want and it simplifies the entire process:
https://github.com/deckarep/EasyCert/releases (only OSX is supported since it uses the openssl tool internally)
and the source:
https://github.com/deckarep/EasyCert
Basically with this tool it will generate a bundle of files but you will need the three that it outputs when it's done.
a CA root cer file
a Server cer file
a Server key file

In my case, the certificate I appended was not encoded correctly in pem format.
If using keytools, ensure to append -rfc while exporting the certificate from keystore, pem encoded could be opened in a text editor to display:
-----BEGIN CERTIFICATE-----
MIIDiDCCAnCgAwIBAgIEHKSkvDANBgkqhkiG9w0BAQsFADBi...

I saw the same error when using mysql client in Go:
Failed to connect to database: x509: cannot validate certificate for 10.111.202.229 because it doesn't contain any IP SANs
and setting InsecureSkipVerify to true (to skip verification of certificate) resolved it for me:
https://godoc.org/crypto/tls#Config
The following code worked for me:
package main
import (
"fmt"
"github.com/go-sql-driver/mysql"
"github.com/jinzhu/gorm"
"crypto/tls"
"crypto/x509"
"io/ioutil"
"log"
)
func main() {
rootCertPool := x509.NewCertPool()
pem, err := ioutil.ReadFile("/usr/local/share/ca-certificates/ccp-root-ca.crt")
if err != nil {
log.Fatal(err)
}
if ok := rootCertPool.AppendCertsFromPEM(pem); !ok {
log.Fatal("Failed to append root CA cert at /usr/local/share/ca-certificates/ccp-root-ca.crt.")
}
mysql.RegisterTLSConfig("custom", &tls.Config{
RootCAs: rootCertPool,
InsecureSkipVerify: true,
})
db, err := gorm.Open("mysql", "ccp-user:I6qnD6zNDmqdDLXYg3HqVAk2P#tcp(10.111.202.229:3306)/ccp?tls=custom")
defer db.Close()
}

You need to use the InsecureSkipVerify flag, refer to https://groups.google.com/forum/#!topic/golang-nuts/c9zEiH6ixyw.
The related code of this post (incase the page is offline):
smtpbox := "mail.foo.com:25"
c, err := smtp.Dial(smtpbox)
host, _, _ := net.SplitHostPort(smtpbox)
tlc := &tls.Config{
InsecureSkipVerify: true,
ServerName: host,
}
if err = c.StartTLS(tlc); err != nil {
fmt.Printf(err)
os.Exit(1)
}
// carry on with rest of smtp transaction
// c.Auth, c.Mail, c.Rcpt, c.Data, etc

Related

Manually Verifying PEM Certificates in Go?

My situation is such: I am manually verifying the Splunk instance's server cert to my client application. I create a new httpclient wrapper with this method. Can someone explain to me exactly what I am to do? My guess is that to 1. there is no IP address designated as the CA, 2. Some config file screaming out, 3. No idea
const SplunkPEM = `---BEGIN...jsldfjklsd---END`
func NewHttpClient() (*http.Client, error) {
rootcas := x509.NewCertPool()
ok := rootcas.AppendCertsFromPEM([]byte(SplunkPEM))
if !ok {
return http.DefaultClient, ErrString("Failed to parse PEM!")
}
conf := &tls.Config{
MinVersion: tls.VersionTLS12,
RootCAs: rootcas,
ServerName: "SplunkServerDefaultCert",
}
tr := &http.Transport{TLSClientConfig: conf}
client := &http.Client{Transport: tr}
return client, nil
}
error 1:
cannot validate certificate for 10.0.0.112 because it doesn't contain any IP SANs
--so I tried changing
&tls.Config{
ServerName: "SplunkServerDefaultCert",
}
error 2:
certificate is valid for SplunkServerDefaultCert, not splunk.com
error 3:
certificate is not authorized to sign other certificates

HTTP SSL with GoDaddy's certificate - This server's certificate chain is incomplete

in general I got 3 files from GoDaddy:
main Certificate file
Server Private Key
Bundle file
in configured all these files in my Go server in the following way:
cert, err := tls.LoadX509KeyPair("myalcoholist.pem","myalcoholist.key")
if err != nil {
log.Fatalf("server: loadkeys: %s", err)
}
pem, err := ioutil.ReadFile("cert/sf_bundle-g2-g1.crt")
if err != nil {
log.Fatalf("Failed to read client certificate authority: %v", err)
}
if !certpool.AppendCertsFromPEM(pem) {
log.Fatalf("Can't parse client certificate authority")
}
tlsConfig := &tls.Config{
ClientCAs: certpool,
Certificates: []tls.Certificate{cert},
}
srv := &http.Server{
Addr: "myalcoholist.com:443",
Handler: n,
ReadTimeout: time.Duration(5) * time.Second,
WriteTimeout: time.Duration(5) * time.Second,
TLSConfig: tlsConfig,
}
err := srv.ListenAndServeTLS("cert/myalcoholist.pem","cert/myalcoholist.key")
The web server runs properly, it's currently published at https://myalcoholist.com:443.
I validated my SSL using https://www.ssllabs.com/ssltest/analyze.html?d=myalcoholist.com and it's response is This server's certificate chain is incomplete. Grade capped to B.
you can go to this link to see the all detailed result.
what am I missing?
Following that thread, and from the net/http/#ListenAndServeTLS() doc:
If the certificate is signed by a certificate authority, the certFile should be the concatenation of the server's certificate, any intermediates, and the CA's certificate.
Try and make sure your cert/myalcoholist.pem includes the CA certificates as well.
That thread used:
myTLSConfig := &tls.Config{
CipherSuites: []uint16{
tls.TLS_RSA_WITH_RC4_128_SHA,
tls.TLS_ECDHE_RSA_WITH_RC4_128_SHA,
tls.TLS_RSA_WITH_AES_128_CBC_SHA,
tls.TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA},}
myTLSConfig.PreferServerCipherSuites = true
const myWebServerListenAddress = "0.0.0.0:5555"
myTLSWebServer := &http.Server{Addr: myWebServerListenAddress, TLSConfig: myTLSConfig, Handler: router}
if err = myTLSWebServer.ListenAndServeTLS("/home/loongson/webServerKeysV2/golangCertFile2", "/home/loongson/webServerKeysV2/adequatech.ca-comodoinstantssl-exported-privatekey-rsa-ForApache.key"); err != nil {
panic(err)
}
Compared to my previous answer, adding a cipher suite is a good idea, but again, try and see if the certificate file passed to ListenAndServeTLS works better if it includes the CAs.
Sure enough, https://www.ssllabs.com/ssltest/analyze.html?d=myalcoholist.com reports grade A, with the warning: “Chain issues: Contains anchor”.
See "SSL/TLS: How to fix “Chain issues: Contains anchor”" to remove that warning, but this is not an error though:
RFC 2119: the server is allowed to include the root certificate (aka "trust anchor") in the chain, or omit it. Some servers include it

Get remote ssl certificate in golang

I want to receive a TCP connection over TLS. I want to validate client certificate and use it to authenticate the client to my application.
Go has the standard crypto/tls package. It can validate client/server certificates. But I can't find way to get details of the remote (client) certificate, like the common name.
Have to call crypto/tls/Conn.Handshake.
Then you can read peer certificate:
tlsconn.ConnectionState().PeerCertificates[0].Subject.CommonName
Following code may help you get your answer
package main
import (
"crypto/tls"
"fmt"
"log"
)
func main() {
conf := &tls.Config{
InsecureSkipVerify: true,
}
conn, err := tls.Dial("tcp", "www.google.com:443", conf)
if err != nil {
log.Println("Error in Dial", err)
return
}
defer conn.Close()
certs := conn.ConnectionState().PeerCertificates
for _, cert := range certs {
fmt.Printf("Issuer Name: %s\n", cert.Issuer)
fmt.Printf("Expiry: %s \n", cert.NotAfter.Format("2006-January-02"))
fmt.Printf("Common Name: %s \n", cert.Issuer.CommonName)
}
}
When working with crypto/tls you can query any Conn object for ConnectionState:
func (c *Conn) ConnectionState() ConnectionState
The ConnectionState struct contains information about the client certificate:
type ConnectionState struct {
PeerCertificates []*x509.Certificate // certificate chain presented by remote peer
}
The x509.Certificate should be pretty straightforward to work with.
Before the server requests for client authentication, you have to configure the connection with the server certificate, client CA (otherwise you will have to verify the trust chain manually, you really don't want that), and tls.RequireAndVerifyClientCert. For example:
// Load my SSL key and certificate
cert, err := tls.LoadX509KeyPair(settings.MyCertificateFile, settings.MyKeyFile)
checkError(err, "LoadX509KeyPair")
// Load the CA certificate for client certificate validation
capool := x509.NewCertPool()
cacert, err := ioutil.ReadFile(settings.CAKeyFile)
checkError(err, "loadCACert")
capool.AppendCertsFromPEM(cacert)
// Prepare server configuration
config := tls.Config{Certificates: []tls.Certificate{cert}, ClientCAs: capool, ClientAuth: tls.RequireAndVerifyClientCert}
config.NextProtos = []string{"http/1.1"}
config.Rand = rand.Reader
There is an easier way to do that:
func renewCert(w http.ResponseWriter, r *http.Request) {
if r.TLS != nil && len(r.TLS.PeerCertificates) > 0 {
cn := strings.ToLower(r.TLS.PeerCertificates[0].Subject.CommonName)
fmt.Println("CN: %s", cn)
}
}

Check fingerprints of server SSL/TLS certificates in http.NewRequest

How can I check the fingerprints of the server SSL/TLS certificates during a http request in golang?
This ruby code shows what I want to do in Go:
#verify_callback = proc do |preverify_ok, store_context|
if preverify_ok and store_context.error == 0
certificate = OpenSSL::X509::Certificate.new(store_context.chain[0])
fingerprint = Digest::SHA1.hexdigest(certificate.to_der).upcase.scan(/../).join(":")
$valid_fingerprints.include?(fingerprint)
else
false
end
end
In general the process of generating a certificate fingerprint in Go is pretty simple. If you already have an x509.Certificate struct, stored in cert, all you need to do is
sha1Fingerprint := sha1.Sum(cert.Raw)
Getting certificates from an HTTP response struct after the request is complete is also pretty easy (use resp.TLS.PeerCertificates), but it doesn't seem like that's what you need.
If you need access to the server's certificate at TLS connection set up time, I think you'll need to create your own http.Transport and hand it a custom implementation of DialTLS. You'd then use that transport when configuring an http.Client to make your outbound requests.
Within your custom DialTLS func you'd have access to connection state information like the server's certificate chain, and you could perform the SHA1 fingerprint generation from there.
You probably shouldn't implement certificate checking yourself, but let the net/http do the checking based on the valid CAs you provide. Also, usually working directly with fingerprints isn't worth the trouble.
For example, this is how you set up a HTTPS server that requires clients to authenticate by using a certificate. The client certificate must be signed by the CA, or the SSL/TLS handshake stops.
// Server's own certificate & key
cert, err := tls.LoadX509KeyPair("server.crt", "server.key")
if err != nil {
panic(err)
}
// Load the CA certificate(s)
capool := x509.NewCertPool()
cacert, err := ioutil.ReadFile("ca.crt")
if err != nil {
panic(err)
}
capool.AppendCertsFromPEM(cacert)
// Server configuration
config := tls.Config{Certificates: []tls.Certificate{cert}, ClientCAs: capool, ClientAuth: tls.RequireAndVerifyClientCert}
config.NextProtos = []string{"http/1.1"}
config.Rand = rand.Reader // Strictly not necessary, should be default
// TLS web server
myTLSWebServer := &http.Server{Addr: "myaddress", TLSConfig: &config, Handler: nil}
// .. proceed with setting handlers etc
http.HandleFunc("/", myHandler)
// Bind to port and start the server up
conn, err := net.Listen("tcp", settings.ServiceAddress)
if err != nil {
panic(err)
}
tlsListener := tls.NewListener(conn, &config)
myTLSWebServer.Serve(tlsListener)
Reading the documentation for tls.Config will show you that by changing the parameters (ClientAuth, ClientCAs, Certificates, RootCAs) you can easily select different modes for checking the certificates. You usually get failures returned in error.
If you really insist on checking fingerprints, you can retrieve the TLS status from Request TLS *tls.ConnectionState. I think you should probably use the Signature from that struct for fingerprinting.. Off the top of my head, something roughly along the lines of
func lol(r *http.Request) {
tls := r.TLS
if tls != nil {
// Try the first one for simplicity
cert := tls.PeerCertificates[0]
signature := cert.Signature
// Do something with the signature
}
}
should do the trick.

Issues with TLS connection in Golang

I have the following certificate hierarchy:
Root-->CA-->3 leaf certificates
The entire chain has both serverAuth and clientAuth as extended key usages explicitly defined.
In my go code, I create a tls.Config object like so:
func parseCert(certFile, keyFile string) (cert tls.Certificate, err error) {
certPEMBlock , err := ioutil.ReadFile(certFile)
if err != nil {
return
}
var certDERBlock *pem.Block
for {
certDERBlock, certPEMBlock = pem.Decode(certPEMBlock)
if certDERBlock == nil {
break
}
if certDERBlock.Type == "CERTIFICATE" {
cert.Certificate = append(cert.Certificate, certDERBlock.Bytes)
}
}
// Need to flip the array because openssl gives it to us in the opposite format than golang tls expects.
cpy := make([][]byte, len(cert.Certificate))
copy(cpy, cert.Certificate)
var j = 0
for i := len(cpy)-1; i >=0; i-- {
cert.Certificate[j] = cert.Certificate[i]
j++
}
keyData, err := ioutil.ReadFile(keyFile)
if err != nil {
return
}
block, _ := pem.Decode(keyData)
if err != nil {
return
}
ecdsaKey, err := x509.ParseECPrivateKey(block.Bytes)
if err != nil {
return
}
cert.PrivateKey = ecdsaKey
return
}
// configure and create a tls.Config instance using the provided cert, key, and ca cert files.
func configureTLS(certFile, keyFile, caCertFile string) (tlsConfig *tls.Config, err error) {
c, err := parseCert(certFile, keyFile)
if err != nil {
return
}
ciphers := []uint16 {
tls.TLS_RSA_WITH_AES_256_CBC_SHA,
tls.TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256,
}
certPool := x509.NewCertPool()
buf, err := ioutil.ReadFile(caCertFile)
if nil != err {
log.Println("failed to load ca cert")
log.Fatal(seelog.Errorf("failed to load ca cert.\n%s", err))
}
if !certPool.AppendCertsFromPEM(buf) {
log.Fatalln("Failed to parse truststore")
}
tlsConfig = &tls.Config {
CipherSuites: ciphers,
ClientAuth: tls.RequireAndVerifyClientCert,
PreferServerCipherSuites: true,
RootCAs: certPool,
ClientCAs: certPool,
Certificates: []tls.Certificate{c},
}
return
}
certFile is the certificate chain file and keyFile is the private key file. caCertFile is the truststore and consists of just the root certificate
So basically, here is what I expect to have inside of my tls.Config object that comes out of this function:
RootCAs: Just the root certificate from caCertFile
ClientCAs: Again, just the root certificate from caCertFile, same as RootCAs
Certificates: A single certificate chain, containing all of the certificates in certFile, ordered to be leaf first.
Now, I have 3 pieces here. A server, a relay, and a client. The client connects directly to the relay, which in turn forwards the request to the server. All three pieces use the same configuration code, of course using different certs/keys. The caCertFile is the same between all 3 pieces.
Now, if I stand up the server and the relay and connect to the relay from my browser, all goes well, so I can assume that the connection between relay and server is fine. The issue comes about when I try to connect my client to the relay. When I do so, the TLS handshake fails and the following error is returned:
x509: certificate signed by unknown authority
On the relay side of things, I get the following error:
http: TLS handshake error from : remote error: bad certificate
I am really at a loss here. I obviously have something setup incorrectly, but I am not sure what. It's really weird that it works from the browser (meaning that the config is correct from relay to server), but it doesn't work with the same config from my client.
Update:
So if I add InsecureSkipVerify: true to my tls.Config object on both the relay and the client, the errors change to:
on the client: remote error: bad certificate
and on the relay: http: TLS handshake error from : tls: client didn't provide a certificate
So it looks like the client is rejecting the certificate on from the server (the relay) due to it being invalid for some reason and thus never sending its certificate to the server (the relay).
I really wish go had better logging. I can't even hook into this process to see what, exactly, is going on.
When you say
Need to flip the array because openssl gives it to us in the opposite format than golang tls expects.
I have used certificates generated by openssl and had no problem opening them with:
tls.LoadX509KeyPair(cert, key)
Anyway, the error message bad certificate is due to the server not managing to match the client-provided certificate against its RootCAs. I have also had this problem in Go using self-signed certificats and the only work-around I've found is to install the caCertFile into the machines system certs, and use x509.SystemCertPool() instead of x509.NewCertPool().
Maybe someone else will have another solution?
Beside what beldin0 suggested.
I have tried another way to do this.
caCertPool := x509.NewCertPool()
caCertPool.AppendCertsFromPEM(crt)
client := &http.Client{
//some config
Transport: &http.Transport{
TLSClientConfig: &tls.Config{
RootCAs: caCertPool,
},
},
}
Here, the variable "crt" is the content in your certificate.
Basically, you just add it into your code(or read as a config file).
Then everything would be fine.