certificates/acme/api/middleware.go
2019-09-13 15:48:33 -07:00

377 lines
11 KiB
Go

package api
import (
"context"
"crypto/rsa"
"io/ioutil"
"net/http"
"net/url"
"strings"
"github.com/go-chi/chi"
"github.com/pkg/errors"
"github.com/smallstep/certificates/acme"
"github.com/smallstep/certificates/api"
"github.com/smallstep/certificates/authority/provisioner"
"github.com/smallstep/certificates/logging"
"github.com/smallstep/cli/crypto/keys"
"github.com/smallstep/cli/jose"
"github.com/smallstep/nosql"
)
type nextHTTP = func(http.ResponseWriter, *http.Request)
func logNonce(w http.ResponseWriter, nonce string) {
if rl, ok := w.(logging.ResponseLogger); ok {
m := map[string]interface{}{
"nonce": nonce,
}
rl.WithFields(m)
}
}
// addNonce is a middleware that adds a nonce to the response header.
func (h *Handler) addNonce(next nextHTTP) nextHTTP {
return func(w http.ResponseWriter, r *http.Request) {
nonce, err := h.Auth.NewNonce()
if err != nil {
api.WriteError(w, err)
return
}
w.Header().Set("Replay-Nonce", nonce)
w.Header().Set("Cache-Control", "no-store")
logNonce(w, nonce)
next(w, r)
return
}
}
// addDirLink is a middleware that adds a 'Link' response reader with the
// directory index url.
func (h *Handler) addDirLink(next nextHTTP) nextHTTP {
return func(w http.ResponseWriter, r *http.Request) {
prov, err := provisionerFromContext(r)
if err != nil {
api.WriteError(w, err)
return
}
w.Header().Add("Link", link(h.Auth.GetLink(acme.DirectoryLink, acme.URLSafeProvisionerName(prov), true), "index"))
next(w, r)
return
}
}
// verifyContentType is a middleware that verifies that content type is
// application/jose+json.
func (h *Handler) verifyContentType(next nextHTTP) nextHTTP {
return func(w http.ResponseWriter, r *http.Request) {
prov, err := provisionerFromContext(r)
if err != nil {
api.WriteError(w, err)
return
}
ct := r.Header.Get("Content-Type")
var expected []string
if strings.Contains(r.URL.Path, h.Auth.GetLink(acme.CertificateLink, acme.URLSafeProvisionerName(prov), false, "")) {
// GET /certificate requests allow a greater range of content types.
expected = []string{"application/jose+json", "application/pkix-cert", "application/pkcs7-mime"}
} else {
// By default every request should have content-type applictaion/jose+json.
expected = []string{"application/jose+json"}
}
for _, e := range expected {
if ct == e {
next(w, r)
return
}
}
api.WriteError(w, acme.MalformedErr(errors.Errorf(
"expected content-type to be in %s, but got %s", expected, ct)))
return
}
}
// parseJWS is a middleware that parses a request body into a JSONWebSignature struct.
func (h *Handler) parseJWS(next nextHTTP) nextHTTP {
return func(w http.ResponseWriter, r *http.Request) {
body, err := ioutil.ReadAll(r.Body)
if err != nil {
api.WriteError(w, acme.ServerInternalErr(errors.Wrap(err, "failed to read request body")))
return
}
jws, err := jose.ParseJWS(string(body))
if err != nil {
api.WriteError(w, acme.MalformedErr(errors.Wrap(err, "failed to parse JWS from request body")))
return
}
ctx := context.WithValue(r.Context(), jwsContextKey, jws)
next(w, r.WithContext(ctx))
return
}
}
// validateJWS checks the request body for to verify that it meets ACME
// requirements for a JWS.
//
// The JWS MUST NOT have multiple signatures
// The JWS Unencoded Payload Option [RFC7797] MUST NOT be used
// The JWS Unprotected Header [RFC7515] MUST NOT be used
// The JWS Payload MUST NOT be detached
// The JWS Protected Header MUST include the following fields:
// * “alg” (Algorithm)
// * This field MUST NOT contain “none” or a Message Authentication Code
// (MAC) algorithm (e.g. one in which the algorithm registry description
// mentions MAC/HMAC).
// * “nonce” (defined in Section 6.5)
// * “url” (defined in Section 6.4)
// * Either “jwk” (JSON Web Key) or “kid” (Key ID) as specified below<Paste>
func (h *Handler) validateJWS(next nextHTTP) nextHTTP {
return func(w http.ResponseWriter, r *http.Request) {
jws, err := jwsFromContext(r)
if err != nil {
api.WriteError(w, err)
return
}
if len(jws.Signatures) == 0 {
api.WriteError(w, acme.MalformedErr(errors.Errorf("request body does not contain a signature")))
return
}
if len(jws.Signatures) > 1 {
api.WriteError(w, acme.MalformedErr(errors.Errorf("request body contains more than one signature")))
return
}
sig := jws.Signatures[0]
uh := sig.Unprotected
if len(uh.KeyID) > 0 ||
uh.JSONWebKey != nil ||
len(uh.Algorithm) > 0 ||
len(uh.Nonce) > 0 ||
len(uh.ExtraHeaders) > 0 {
api.WriteError(w, acme.MalformedErr(errors.Errorf("unprotected header must not be used")))
return
}
hdr := sig.Protected
switch hdr.Algorithm {
case jose.RS256, jose.RS384, jose.RS512:
if hdr.JSONWebKey != nil {
switch k := hdr.JSONWebKey.Key.(type) {
case *rsa.PublicKey:
if k.Size() < keys.MinRSAKeyBytes {
api.WriteError(w, acme.MalformedErr(errors.Errorf("rsa "+
"keys must be at least %d bits (%d bytes) in size",
8*keys.MinRSAKeyBytes, keys.MinRSAKeyBytes)))
return
}
default:
api.WriteError(w, acme.MalformedErr(errors.Errorf("jws key type and algorithm do not match")))
return
}
}
case jose.ES256, jose.ES384, jose.ES512, jose.EdDSA:
// we good
default:
api.WriteError(w, acme.MalformedErr(errors.Errorf("unsuitable algorithm: %s", hdr.Algorithm)))
return
}
// Check the validity/freshness of the Nonce.
if err := h.Auth.UseNonce(hdr.Nonce); err != nil {
api.WriteError(w, err)
return
}
// Check that the JWS url matches the requested url.
jwsURL, ok := hdr.ExtraHeaders["url"].(string)
if !ok {
api.WriteError(w, acme.MalformedErr(errors.Errorf("jws missing url protected header")))
return
}
reqURL := &url.URL{Scheme: "https", Host: r.Host, Path: r.URL.Path}
if jwsURL != reqURL.String() {
api.WriteError(w, acme.MalformedErr(errors.Errorf("url header in JWS (%s) does not match request url (%s)", jwsURL, reqURL)))
return
}
if hdr.JSONWebKey != nil && len(hdr.KeyID) > 0 {
api.WriteError(w, acme.MalformedErr(errors.Errorf("jwk and kid are mutually exclusive")))
return
}
if hdr.JSONWebKey == nil && len(hdr.KeyID) == 0 {
api.WriteError(w, acme.MalformedErr(errors.Errorf("either jwk or kid must be defined in jws protected header")))
return
}
next(w, r)
return
}
}
// extractJWK is a middleware that extracts the JWK from the JWS and saves it
// in the context. Make sure to parse and validate the JWS before running this
// middleware.
func (h *Handler) extractJWK(next nextHTTP) nextHTTP {
return func(w http.ResponseWriter, r *http.Request) {
ctx := r.Context()
prov, err := provisionerFromContext(r)
if err != nil {
api.WriteError(w, err)
return
}
jws, err := jwsFromContext(r)
if err != nil {
api.WriteError(w, err)
return
}
jwk := jws.Signatures[0].Protected.JSONWebKey
if jwk == nil {
api.WriteError(w, acme.MalformedErr(errors.Errorf("jwk expected in protected header")))
return
}
if !jwk.Valid() {
api.WriteError(w, acme.MalformedErr(errors.Errorf("invalid jwk in protected header")))
return
}
ctx = context.WithValue(ctx, jwkContextKey, jwk)
acc, err := h.Auth.GetAccountByKey(prov, jwk)
switch {
case nosql.IsErrNotFound(err):
// For NewAccount requests ...
break
case err != nil:
api.WriteError(w, err)
return
default:
if !acc.IsValid() {
api.WriteError(w, acme.UnauthorizedErr(errors.New("account is not active")))
return
}
ctx = context.WithValue(ctx, accContextKey, acc)
}
next(w, r.WithContext(ctx))
return
}
}
// lookupProvisioner loads the provisioner associated with the request.
// Responsds 404 if the provisioner does not exist.
func (h *Handler) lookupProvisioner(next nextHTTP) nextHTTP {
return func(w http.ResponseWriter, r *http.Request) {
ctx := r.Context()
name := chi.URLParam(r, "provisionerID")
provID, err := url.PathUnescape(name)
if err != nil {
api.WriteError(w, acme.ServerInternalErr(errors.Wrapf(err, "error url unescaping provisioner id '%s'", name)))
return
}
p, err := h.Auth.LoadProvisionerByID("acme/" + provID)
if err != nil {
api.WriteError(w, err)
return
}
if p.GetType() != provisioner.TypeACME {
api.WriteError(w, acme.AccountDoesNotExistErr(errors.New("provisioner must be of type ACME")))
return
}
ctx = context.WithValue(ctx, provisionerContextKey, p)
next(w, r.WithContext(ctx))
return
}
}
// lookupJWK loads the JWK associated with the acme account referenced by the
// kid parameter of the signed payload.
// Make sure to parse and validate the JWS before running this middleware.
func (h *Handler) lookupJWK(next nextHTTP) nextHTTP {
return func(w http.ResponseWriter, r *http.Request) {
ctx := r.Context()
prov, err := provisionerFromContext(r)
if err != nil {
api.WriteError(w, err)
return
}
jws, err := jwsFromContext(r)
if err != nil {
api.WriteError(w, err)
return
}
kidPrefix := h.Auth.GetLink(acme.AccountLink, acme.URLSafeProvisionerName(prov), true, "")
kid := jws.Signatures[0].Protected.KeyID
if !strings.HasPrefix(kid, kidPrefix) {
api.WriteError(w, acme.MalformedErr(errors.Errorf("kid does not have "+
"required prefix; expected %s, but got %s", kidPrefix, kid)))
return
}
accID := strings.TrimPrefix(kid, kidPrefix)
acc, err := h.Auth.GetAccount(prov, accID)
switch {
case nosql.IsErrNotFound(err):
api.WriteError(w, acme.AccountDoesNotExistErr(nil))
return
case err != nil:
api.WriteError(w, err)
return
default:
if !acc.IsValid() {
api.WriteError(w, acme.UnauthorizedErr(errors.New("account is not active")))
return
}
ctx = context.WithValue(ctx, accContextKey, acc)
ctx = context.WithValue(ctx, jwkContextKey, acc.Key)
next(w, r.WithContext(ctx))
return
}
}
}
// verifyAndExtractJWSPayload extracts the JWK from the JWS and saves it in the context.
// Make sure to parse and validate the JWS before running this middleware.
func (h *Handler) verifyAndExtractJWSPayload(next nextHTTP) nextHTTP {
return func(w http.ResponseWriter, r *http.Request) {
jws, err := jwsFromContext(r)
if err != nil {
api.WriteError(w, err)
return
}
jwk, err := jwkFromContext(r)
if err != nil {
api.WriteError(w, err)
return
}
if len(jwk.Algorithm) != 0 && jwk.Algorithm != jws.Signatures[0].Protected.Algorithm {
api.WriteError(w, acme.MalformedErr(errors.New("verifier and signature algorithm do not match")))
return
}
payload, err := jws.Verify(jwk)
if err != nil {
api.WriteError(w, acme.MalformedErr(errors.Wrap(err, "error verifying jws")))
return
}
ctx := context.WithValue(r.Context(), payloadContextKey, &payloadInfo{
value: payload,
isPostAsGet: string(payload) == "",
isEmptyJSON: string(payload) == "{}",
})
next(w, r.WithContext(ctx))
return
}
}
// isPostAsGet asserts that the request is a PostAsGet (empty JWS payload).
func (h *Handler) isPostAsGet(next nextHTTP) nextHTTP {
return func(w http.ResponseWriter, r *http.Request) {
payload, err := payloadFromContext(r)
if err != nil {
api.WriteError(w, err)
return
}
if !payload.isPostAsGet {
api.WriteError(w, acme.MalformedErr(errors.Errorf("expected POST-as-GET")))
return
}
next(w, r)
return
}
}