docs: add issue to use the ACME protocol

1 files changed, 69 insertions, 0 deletions

diff --git a/doc/share/authz/todo/004_acme_protocol.md b/doc/share/authz/todo/004_acme_protocol.md
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+As an `Operator`, I want to `use the ACME protocol`, so that `I have a standards based way to manage PKI`.
+
+# SYNOPSIS
+
+Use the ACME protocol to generate TLS PKI.
+
+# DESCRIPTION
+
+Below is an example startup configuration for using the ACME protocol in golang
+and distributing the key material using file storage. The file storage should be
+replaced with a distributed blob storage that is locked down. This also uses
+the `STEPPATH` environment variable to access an internal root certificate
+authority.
+
+```golang
+func WithAcmeTLS(ctx context.Context, directoryURL string, cacheDir string) cfg.Option {
+	storageFor := func(config *cfg.Config) certmagic.Storage {
+		return &certmagic.FileStorage{Path: cacheDir}
+	}
+	return func(config *cfg.Config) {
+		host := os.Getenv("HOST")
+		tls := srv.NewTLS(ctx, host, storageFor(config), []certmagic.ACMEIssuer{
+			{
+				Agreed:               true,
+				CA:                   directoryURL,
+				DisableHTTPChallenge: true,
+				Email:                "everyone@example.com",
+				TestCA:               directoryURL,
+				TrustedRoots:         newCertPool(),
+				AltTLSALPNPort:       bindingPort(),
+			},
+		})
+		config.TLS = x.Must(tls.Config())
+	}
+}
+
+func newCertPool() *x509.CertPool {
+	certPool := x.Must(x509.SystemCertPool())
+  certPool.AddCert(func() *x509.Certificate {
+    block, _ := pem.Decode(x.Must(ioutil.ReadFile(
+      filepath.Join(os.ExpandEnv("$STEPPATH"), "/certs/root_ca.crt"),
+    )))
+    return x.Must(x509.ParseCertificate(block.Bytes))
+  }())
+	return certPool
+}
+
+func bindingPort() int {
+	parts := strings.SplitN(os.Getenv("BIND_ADDR"), ":", 2)
+	bindPort, err := strconv.Atoi(parts[1])
+	if err != nil {
+		bindPort = 0
+	}
+	return bindPort
+}
+```
+
+# SEE ALSO
+
+* [RFC-8555](https://datatracker.ietf.org/doc/html/rfc8555)
+* [$STEPPATH](https://smallstep.com/docs/step-cli/reference/path/#examples)
+
+# Tasks
+
+* [ ] TBD
+
+# Acceptance Criteria
+
+* [ ] TBD