Add support for challenge password

authority/provisioner/scep.go

@@ -15,6 +15,7 @@ type SCEP struct {
 	Name string `json:"name"`
 
 	ForceCN           bool     `json:"forceCN,omitempty"`
+	ChallengePassword string   `json:"challenge,omitempty"`
 	Options           *Options `json:"options,omitempty"`
 	Claims            *Claims  `json:"claims,omitempty"`
 	claimer           *Claimer
@@ -76,7 +77,7 @@ func (s *SCEP) Init(config Config) (err error) {
 	return err
 }
 
-// AuthorizeSign does not do any validation, because all validation is handled
+// AuthorizeSign does not do any verification, because all verification is handled
 // in the SCEP protocol. This method returns a list of modifiers / constraints
 // on the resulting certificate.
 func (s *SCEP) AuthorizeSign(ctx context.Context, token string) ([]SignOption, error) {
@@ -91,6 +92,11 @@ func (s *SCEP) AuthorizeSign(ctx context.Context, token string) ([]SignOption, e
 	}, nil
 }
 
+// GetChallengePassword returns the challenge password
+func (s *SCEP) GetChallengePassword() string {
+	return s.ChallengePassword
+}
+
 // Interface guards
 var (
 	_ Interface = (*SCEP)(nil)

scep/api/api.go

@@ -80,7 +80,6 @@ func New(scepAuth scep.Interface) api.RouterHandler {
 // Route traffic and implement the Router interface.
 func (h *Handler) Route(r api.Router) {
 	getLink := h.Auth.GetLinkExplicit
-
 	r.MethodFunc(http.MethodGet, getLink("{provisionerID}", false, nil), h.lookupProvisioner(h.Get))
 	r.MethodFunc(http.MethodPost, getLink("{provisionerID}", false, nil), h.lookupProvisioner(h.Post))
 }
@@ -140,6 +139,8 @@ func (h *Handler) Post(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
+	// TODO: fix cases in which we get here and there's no certificate (i.e. wrong password, waiting for cert, etc)
+	// We should generate an appropriate response and it should be signed
 	api.LogCertificate(w, response.Certificate)
 
 	writeSCEPResponse(w, response)
@@ -238,8 +239,10 @@ func (h *Handler) GetCACert(ctx context.Context) (SCEPResponse, error) {
 		return SCEPResponse{}, errors.New("missing CA cert")
 	}
 
-	response := SCEPResponse{Operation: opnGetCACert}
-	response.CACertNum = len(certs)
+	response := SCEPResponse{
+		Operation: opnGetCACert,
+		CACertNum: len(certs),
+	}
 
 	if len(certs) == 1 {
 		response.Data = certs[0].Raw
@@ -268,8 +271,6 @@ func (h *Handler) GetCACaps(ctx context.Context) (SCEPResponse, error) {
 // PKIOperation performs PKI operations and returns a SCEP response
 func (h *Handler) PKIOperation(ctx context.Context, request SCEPRequest) (SCEPResponse, error) {
 
-	response := SCEPResponse{Operation: opnPKIOperation}
-
 	// parse the message using microscep implementation
 	microMsg, err := microscep.ParsePKIMessage(request.Message)
 	if err != nil {
@@ -295,7 +296,15 @@ func (h *Handler) PKIOperation(ctx context.Context, request SCEPRequest) (SCEPRe
 	}
 
 	if msg.MessageType == microscep.PKCSReq {
-		// TODO: CSR validation, like challenge password
+
+		challengeMatches, err := h.Auth.MatchChallengePassword(ctx, msg.CSRReqMessage.ChallengePassword)
+		if err != nil {
+			return SCEPResponse{}, err
+		}
+
+		if !challengeMatches {
+			return SCEPResponse{}, errors.New("wrong password provided")
+		}
 	}
 
 	csr := msg.CSRReqMessage.CSR
@@ -311,8 +320,11 @@ func (h *Handler) PKIOperation(ctx context.Context, request SCEPRequest) (SCEPRe
 	// // TODO: check if CN already exists, if renewal is allowed and if existing should be revoked; fail if not
 	// // TODO: store the new cert for CN locally; should go into the DB
 
-	response.Data = certRep.Raw
-	response.Certificate = certRep.Certificate
+	response := SCEPResponse{
+		Operation:   opnPKIOperation,
+		Data:        certRep.Raw,
+		Certificate: certRep.Certificate,
+	}
 
 	return response, nil
 }
@@ -338,6 +350,7 @@ func writeSCEPResponse(w http.ResponseWriter, response SCEPResponse) {
 }
 
 func writeError(w http.ResponseWriter, err error) {
+	// TODO: this probably needs to use SCEP specific errors (i.e. failInfo)
 	scepError := &scep.Error{
 		Message: err.Error(),
 		Status:  http.StatusInternalServerError, // TODO: make this a param?

scep/authority.go

@@ -56,6 +56,7 @@ type Interface interface {
 	GetCACertificates() ([]*x509.Certificate, error)
 	DecryptPKIEnvelope(ctx context.Context, msg *PKIMessage) error
 	SignCSR(ctx context.Context, csr *x509.CertificateRequest, msg *PKIMessage) (*PKIMessage, error)
+	MatchChallengePassword(ctx context.Context, password string) (bool, error)
 
 	GetLinkExplicit(provName string, absoluteLink bool, baseURL *url.URL, inputs ...string) string
 }
@@ -401,6 +402,25 @@ func (a *Authority) SignCSR(ctx context.Context, csr *x509.CertificateRequest, m
 	return crepMsg, nil
 }
 
+// MatchChallengePassword verifies a SCEP challenge password
+func (a *Authority) MatchChallengePassword(ctx context.Context, password string) (bool, error) {
+
+	p, err := ProvisionerFromContext(ctx)
+	if err != nil {
+		return false, err
+	}
+
+	if p.GetChallengePassword() == password {
+		return true, nil
+	}
+
+	// TODO: support dynamic challenges, i.e. a list of challenges instead of one?
+	// That's probably a bit harder to configure, though; likely requires some data store
+	// that can be interacted with more easily, via some internal API, for example.
+
+	return false, nil
+}
+
 // degenerateCertificates creates degenerate certificates pkcs#7 type
 func degenerateCertificates(certs []*x509.Certificate) ([]byte, error) {
 	var buf bytes.Buffer

scep/provisioner.go

@@ -14,4 +14,5 @@ type Provisioner interface {
 	GetName() string
 	DefaultTLSCertDuration() time.Duration
 	GetOptions() *provisioner.Options
+	GetChallengePassword() string
 }