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https://github.com/mdelapenya/tlscert

Quickly generate customisable TLS certificates for Go apps. Ideal for testing and secure setups.
https://github.com/mdelapenya/tlscert

golang self-signed-certificate testing tls

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Quickly generate customisable TLS certificates for Go apps. Ideal for testing and secure setups.

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# tlscert

This is a simple tool to generate self-signed certificates for testing purposes.

## Motivation

This package is intended to be used in tests that require a self-signed certificate. It is not intended to be used in production code.

I many times found myself needing to generate a self-signed certificate for testing purposes, and I always had to look up how to do it. This package is an attempt to make this process easier, providing a simple API to generate self-signed certificates and save them to disk, if needed.

## Features

The package exposes two functions and two types: `SelfSigned` and `SelfSignedFromRequest`, and `Request` and `Certificate`.

- The `Request` type is used to specify the parameters for the certificate generation.
- The `Certificate` type is used to store the generated certificate and key, including the paths to the files on disk.
- The `SelfSigned` function generates a self-signed certificate and returns it as a `Certificate` value. This function only receives the host name for the certificate.
- The `SelfSignedFromRequest` function generates a self-signed certificate based on the parameters in a `Request` value.

Therefore, it's possible to issue a self-signed certificate with a custom host name, and save it to disk, if needed, or to issue a certificate based on a parent certificate, which is useful for generating client certificates.

The `Request` struct also provides a `ParentDir` option that can be used to save the generated certificate to disk as a PEM file.

The `Certificate` struct provides a `Transport` method, which returns a pointer to a `http.Transport` that can be used to perform HTTP requests using the generated certificate; and a `TLSConfig` method, which returns a pointer to a `tls.Config`. The `Transport` method internally uses the `TLSConfig` method.

## Example

You can find a simple example in the [example_test.go](example_test.go) file:

```go
package tlscert_test

import (
"fmt"
"io"
"log"
"net/http"
"os"

"github.com/mdelapenya/tlscert"
)

func ExampleSelfSigned() {
tmp := os.TempDir()
certsDir := tmp + "/certs"
defer os.RemoveAll(certsDir)

if err := os.MkdirAll(certsDir, 0o755); err != nil {
log.Fatal(err) // nolint: gocritic
}

// Generate a certificate for localhost and save it to disk.
caCert := tlscert.SelfSignedFromRequest(tlscert.Request{
Host: "localhost",
Name: "ca-cert",
ParentDir: certsDir,
})
if caCert == nil {
log.Fatal("Failed to generate CA certificate")
}

cert := tlscert.SelfSignedFromRequest(tlscert.Request{
Host: "localhost",
Name: "client-cert",
Parent: caCert,
ParentDir: certsDir,
})
if cert == nil {
log.Fatal("Failed to generate certificate")
}

// create an http server that uses the generated certificate
// and private key to serve requests over HTTPS

server := &http.Server{
Addr: ":8443",
}

server.Handler = http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {
w.Header().Set("Content-Type", "text/plain")
_, err := w.Write([]byte("TLS works!\n"))
if err != nil {
log.Printf("Failed to write response: %v", err)
}
})

go func() {
_ = server.ListenAndServeTLS(cert.CertPath, cert.KeyPath)
}()
defer server.Close()

// perform an HTTP request to the server, using the generated certificate

const url = "https://localhost:8443/hello"

client := &http.Client{Transport: cert.Transport()}
resp, err := client.Get(url)
if err != nil {
log.Fatalf("Failed to get response: %v", err)
}
defer resp.Body.Close()

body, err := io.ReadAll(resp.Body)
if err != nil {
log.Fatalf("Failed to read response body: %v", err)
}

fmt.Println(string(body))

// Output:
// TLS works!
}
```