Add bootstrap helpers that uses just a token.

ca/bootstrap.go

@@ -0,0 +1,114 @@
+package ca
+
+import (
+	"context"
+	"net/http"
+	"strings"
+
+	"github.com/pkg/errors"
+	"github.com/smallstep/cli/jose"
+	"gopkg.in/square/go-jose.v2/jwt"
+)
+
+type tokenClaims struct {
+	SHA string `json:"sha"`
+	jose.Claims
+}
+
+// Bootstrap is a helper function that initializes a client with the
+// configuration in the bootstrap token.
+func Bootstrap(token string) (*Client, error) {
+	tok, err := jwt.ParseSigned(token)
+	if err != nil {
+		return nil, errors.Wrap(err, "error parsing token")
+	}
+	var claims tokenClaims
+	if err := tok.UnsafeClaimsWithoutVerification(&claims); err != nil {
+		return nil, errors.Wrap(err, "error parsing ott")
+	}
+
+	// Validate bootstrap token
+	switch {
+	case len(claims.SHA) == 0:
+		return nil, errors.New("invalid bootstrap token: sha claim is not present")
+	case !strings.HasPrefix(strings.ToLower(claims.Audience[0]), "http"):
+		return nil, errors.New("invalid bootstrap token: aud claim is not a url")
+	}
+
+	return NewClient(claims.Audience[0], WithRootSHA256(claims.SHA))
+}
+
+// BootstrapServer is a helper function that returns an http.Server configured
+// with the given address and handler, and prepared to use TLS connections. The
+// certificate will automatically rotate if necessary.
+//
+// Usage:
+//   srv, err := ca.BootstrapServer(":443", token, handler)
+//   if err != nil {
+//       return err
+//   }
+//   srv.ListenAndServeTLS("", "")
+func BootstrapServer(addr, token string, handler http.Handler) (*http.Server, error) {
+	client, err := Bootstrap(token)
+	if err != nil {
+		return nil, err
+	}
+
+	req, pk, err := CreateSignRequest(token)
+	if err != nil {
+		return nil, err
+	}
+
+	sign, err := client.Sign(req)
+	if err != nil {
+		return nil, err
+	}
+
+	tlsConfig, err := client.GetServerTLSConfig(context.Background(), sign, pk)
+	if err != nil {
+		return nil, err
+	}
+
+	return &http.Server{
+		Addr:      addr,
+		Handler:   handler,
+		TLSConfig: tlsConfig,
+	}, nil
+}
+
+// BootstrapClient is a helper function that using the given bootstrap token
+// return an http.Client configured with a Transport prepared to do TLS
+// connections using the client certificate returned by the certificate
+// authority. The certificate will automatically rotate if necessary.
+//
+// Usage:
+//   client, err := ca.BootstrapClient(token)
+//   if err != nil {
+//     return err
+//   }
+//   resp, err := client.Get("https://internal.smallstep.com")
+func BootstrapClient(token string) (*http.Client, error) {
+	client, err := Bootstrap(token)
+	if err != nil {
+		return nil, err
+	}
+
+	req, pk, err := CreateSignRequest(token)
+	if err != nil {
+		return nil, err
+	}
+
+	sign, err := client.Sign(req)
+	if err != nil {
+		return nil, err
+	}
+
+	transport, err := client.Transport(context.Background(), sign, pk)
+	if err != nil {
+		return nil, err
+	}
+
+	return &http.Client{
+		Transport: transport,
+	}, nil
+}