Introduce generalized statusCoder errors and loads of ssh unit tests.

* StatusCoder api errors that have friendly user messages.
* Unit tests for SSH sign/renew/rekey/revoke across all provisioners.

api/renew.go

@@ -0,0 +1,36 @@
+package api
+
+import (
+	"net/http"
+
+	"github.com/pkg/errors"
+	"github.com/smallstep/certificates/errs"
+)
+
+// Renew uses the information of certificate in the TLS connection to create a
+// new one.
+func (h *caHandler) Renew(w http.ResponseWriter, r *http.Request) {
+	if r.TLS == nil || len(r.TLS.PeerCertificates) == 0 {
+		WriteError(w, errs.BadRequest(errors.New("missing peer certificate")))
+		return
+	}
+
+	certChain, err := h.Authority.Renew(r.TLS.PeerCertificates[0])
+	if err != nil {
+		WriteError(w, errs.Wrap(http.StatusInternalServerError, err, "cahandler.Renew"))
+		return
+	}
+	certChainPEM := certChainToPEM(certChain)
+	var caPEM Certificate
+	if len(certChainPEM) > 0 {
+		caPEM = certChainPEM[1]
+	}
+
+	logCertificate(w, certChain[0])
+	JSONStatus(w, &SignResponse{
+		ServerPEM:    certChainPEM[0],
+		CaPEM:        caPEM,
+		CertChainPEM: certChainPEM,
+		TLSOptions:   h.Authority.GetTLSOptions(),
+	}, http.StatusCreated)
+}