Add getSSHHosts injection func

Author: dopey

Diff for: api/ssh.go

@@ -23,7 +23,7 @@ type SSHAuthority interface {
 	GetSSHFederation() (*authority.SSHKeys, error)
 	GetSSHConfig(typ string, data map[string]string) ([]templates.Output, error)
 	CheckSSHHost(principal string) (bool, error)
-	GetSSHHosts() ([]string, error)
+	GetSSHHosts(user string) ([]string, error)
 	GetSSHBastion(user string, hostname string) (*authority.Bastion, error)
 }
 
@@ -406,7 +406,18 @@ func (h *caHandler) SSHCheckHost(w http.ResponseWriter, r *http.Request) {
 
 // SSHGetHosts is the HTTP handler that returns a list of valid ssh hosts.
 func (h *caHandler) SSHGetHosts(w http.ResponseWriter, r *http.Request) {
-	hosts, err := h.Authority.GetSSHHosts()
+	if r.TLS == nil || len(r.TLS.PeerCertificates) == 0 {
+		WriteError(w, BadRequest(errors.New("missing peer certificate")))
+		return
+	}
+
+	cert := r.TLS.PeerCertificates[0]
+	email := cert.EmailAddresses[0]
+	if len(email) == 0 {
+		WriteError(w, BadRequest(errors.New("client certificate missing email SAN")))
+		return
+	}
+	hosts, err := h.Authority.GetSSHHosts(email)
 	if err != nil {
 		WriteError(w, InternalServerError(err))
 		return

Diff for: authority/authority.go

@@ -41,6 +41,7 @@ type Authority struct {
 	initOnce bool
 	// Custom functions
 	sshBastionFunc  func(user, hostname string) (*Bastion, error)
+	sshGetHostsFunc func(user string) ([]string, error)
 	getIdentityFunc provisioner.GetIdentityFunc
 }
 

Diff for: authority/options.go

@@ -16,6 +16,14 @@ func WithDatabase(db db.AuthDB) Option {
 	}
 }
 
+// WithGetIdentityFunc sets a custom function to retrieve the identity from
+// an external resource.
+func WithGetIdentityFunc(fn func(p provisioner.Interface, email string) (*provisioner.Identity, error)) Option {
+	return func(a *Authority) {
+		a.getIdentityFunc = fn
+	}
+}
+
 // WithSSHBastionFunc sets a custom function to get the bastion for a
 // given user-host pair.
 func WithSSHBastionFunc(fn func(user, host string) (*Bastion, error)) Option {
@@ -24,10 +32,10 @@ func WithSSHBastionFunc(fn func(user, host string) (*Bastion, error)) Option {
 	}
 }
 
-// WithGetIdentityFunc sets a custom function to retrieve the identity from
-// an external resource.
-func WithGetIdentityFunc(fn func(p provisioner.Interface, email string) (*provisioner.Identity, error)) Option {
+// WithSSHGetHosts sets a custom function to get the bastion for a
+// given user-host pair.
+func WithSSHGetHosts(fn func(user string) ([]string, error)) Option {
 	return func(a *Authority) {
-		a.getIdentityFunc = fn
+		a.sshGetHostsFunc = fn
 	}
 }

Diff for: authority/ssh.go

@@ -673,13 +673,14 @@ func (a *Authority) CheckSSHHost(principal string) (bool, error) {
 }
 
 // GetSSHHosts returns a list of valid host principals.
-func (a *Authority) GetSSHHosts() ([]string, error) {
-	ps, err := a.db.GetSSHHostPrincipals()
-	if err != nil {
-		return nil, err
+func (a *Authority) GetSSHHosts(email string) ([]string, error) {
+	if a.sshBastionFunc != nil {
+		return a.sshGetHostsFunc(email)
+	}
+	return nil, &apiError{
+		err:  errors.New("getSSHHosts is not configured"),
+		code: http.StatusNotFound,
 	}
-
-	return ps, nil
 }
 
 func (a *Authority) getAddUserPrincipal() (cmd string) {