Add support for /ssh/bastion method.

api/api.go

@@ -261,6 +261,7 @@ func (h *caHandler) Route(r Router) {
 	r.MethodFunc("POST", "/ssh/config/{type}", h.SSHConfig)
 	r.MethodFunc("POST", "/ssh/check-host", h.SSHCheckHost)
 	r.MethodFunc("GET", "/ssh/get-hosts", h.SSHGetHosts)
+	r.MethodFunc("POST", "/ssh/bastion", h.SSHBastion)
 
 	// For compatibility with old code:
 	r.MethodFunc("POST", "/re-sign", h.Renew)

api/api_test.go

@@ -557,6 +557,7 @@ type mockAuthority struct {
 	getSSHFederation             func() (*authority.SSHKeys, error)
 	getSSHConfig                 func(typ string, data map[string]string) ([]templates.Output, error)
 	checkSSHHost                 func(principal string) (bool, error)
+	getSSHBastion                func(user string, hostname string) (*authority.Bastion, error)
 }
 
 // TODO: remove once Authorize is deprecated.
@@ -711,6 +712,13 @@ func (m *mockAuthority) CheckSSHHost(principal string) (bool, error) {
 	return m.ret1.(bool), m.err
 }
 
+func (m *mockAuthority) GetSSHBastion(user string, hostname string) (*authority.Bastion, error) {
+	if m.getSSHBastion != nil {
+		return m.getSSHBastion(user, hostname)
+	}
+	return m.ret1.(*authority.Bastion), m.err
+}
+
 func Test_caHandler_Route(t *testing.T) {
 	type fields struct {
 		Authority Authority

api/ssh.go

@@ -24,6 +24,7 @@ type SSHAuthority interface {
 	GetSSHConfig(typ string, data map[string]string) ([]templates.Output, error)
 	CheckSSHHost(principal string) (bool, error)
 	GetSSHHosts() ([]string, error)
+	GetSSHBastion(user string, hostname string) (*authority.Bastion, error)
 }
 
 // SSHSignRequest is the request body of an SSH certificate request.
@@ -207,6 +208,28 @@ type SSHCheckPrincipalResponse struct {
 	Exists bool `json:"exists"`
 }
 
+// SSHBastionRequest is the request body used to get the bastion for a given
+// host.
+type SSHBastionRequest struct {
+	User     string `json:"user"`
+	Hostname string `json:"hostname"`
+}
+
+// Validate checks the values of the SSHBastionRequest.
+func (r *SSHBastionRequest) Validate() error {
+	if r.Hostname == "" {
+		return errors.New("missing or empty hostname")
+	}
+	return nil
+}
+
+// SSHBastionResponse is the response body used to return the bastion for a
+// given host.
+type SSHBastionResponse struct {
+	Hostname string             `json:"hostname"`
+	Bastion  *authority.Bastion `json:"bastion,omitempty"`
+}
+
 // SSHSign is an HTTP handler that reads an SignSSHRequest with a one-time-token
 // (ott) from the body and creates a new SSH certificate with the information in
 // the request.
@@ -392,3 +415,27 @@ func (h *caHandler) SSHGetHosts(w http.ResponseWriter, r *http.Request) {
 		Hosts: hosts,
 	})
 }
+
+// SSHBastion provides returns the bastion configured if any.
+func (h *caHandler) SSHBastion(w http.ResponseWriter, r *http.Request) {
+	var body SSHBastionRequest
+	if err := ReadJSON(r.Body, &body); err != nil {
+		WriteError(w, BadRequest(errors.Wrap(err, "error reading request body")))
+		return
+	}
+	if err := body.Validate(); err != nil {
+		WriteError(w, BadRequest(err))
+		return
+	}
+
+	bastion, err := h.Authority.GetSSHBastion(body.User, body.Hostname)
+	if err != nil {
+		WriteError(w, InternalServerError(err))
+		return
+	}
+
+	JSON(w, &SSHBastionResponse{
+		Hostname: body.Hostname,
+		Bastion:  bastion,
+	})
+}

api/ssh_test.go

@@ -537,6 +537,61 @@ func Test_caHandler_SSHCheckHost(t *testing.T) {
 	}
 }
 
+func Test_caHandler_SSHBastion(t *testing.T) {
+	bastion := &authority.Bastion{
+		Hostname: "bastion.local",
+	}
+	bastionPort := &authority.Bastion{
+		Hostname: "bastion.local",
+		Port:     "2222",
+	}
+
+	tests := []struct {
+		name       string
+		bastion    *authority.Bastion
+		bastionErr error
+		req        []byte
+		body       []byte
+		statusCode int
+	}{
+		{"ok", bastion, nil, []byte(`{"hostname":"host.local"}`), []byte(`{"hostname":"host.local","bastion":{"hostname":"bastion.local"}}`), http.StatusOK},
+		{"ok", bastionPort, nil, []byte(`{"hostname":"host.local","user":"user"}`), []byte(`{"hostname":"host.local","bastion":{"hostname":"bastion.local","port":"2222"}}`), http.StatusOK},
+		{"empty", nil, nil, []byte(`{"hostname":"host.local"}`), []byte(`{"hostname":"host.local"}`), http.StatusOK},
+		{"bad json", bastion, nil, []byte(`bad json`), nil, http.StatusBadRequest},
+		{"bad request", bastion, nil, []byte(`{"hostname": ""}`), nil, http.StatusBadRequest},
+		{"error", nil, fmt.Errorf("an error"), []byte(`{"hostname":"host.local"}`), nil, http.StatusInternalServerError},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			h := New(&mockAuthority{
+				getSSHBastion: func(user, hostname string) (*authority.Bastion, error) {
+					return tt.bastion, tt.bastionErr
+				},
+			}).(*caHandler)
+
+			req := httptest.NewRequest("POST", "http://example.com/ssh/bastion", bytes.NewReader(tt.req))
+			w := httptest.NewRecorder()
+			h.SSHBastion(logging.NewResponseLogger(w), req)
+			res := w.Result()
+
+			if res.StatusCode != tt.statusCode {
+				t.Errorf("caHandler.SSHBastion StatusCode = %d, wants %d", res.StatusCode, tt.statusCode)
+			}
+
+			body, err := ioutil.ReadAll(res.Body)
+			res.Body.Close()
+			if err != nil {
+				t.Errorf("caHandler.SSHBastion unexpected error = %v", err)
+			}
+			if tt.statusCode < http.StatusBadRequest {
+				if !bytes.Equal(bytes.TrimSpace(body), tt.body) {
+					t.Errorf("caHandler.SSHBastion Body = %s, wants %s", body, tt.body)
+				}
+			}
+		})
+	}
+}
+
 func TestSSHPublicKey_MarshalJSON(t *testing.T) {
 	key, err := ssh.NewPublicKey(sshUserKey.Public())
 	assert.FatalError(t, err)

authority/authority.go

@@ -39,6 +39,8 @@ type Authority struct {
 	db                      db.AuthDB
 	// Do not re-initialize
 	initOnce bool
+	// Custom functions
+	sshBastionFunc func(user, hostname string) (*Bastion, error)
 }
 
 // New creates and initiates a new Authority type.

authority/options.go

@@ -14,3 +14,11 @@ func WithDatabase(db db.AuthDB) Option {
 		a.db = db
 	}
 }
+
+// WithSSHBastionFunc defines sets a custom function to get the bastion for a
+// given user-host pair.
+func WithSSHBastionFunc(fn func(user, host string) (*Bastion, error)) Option {
+	return func(a *Authority) {
+		a.sshBastionFunc = fn
+	}
+}

authority/ssh.go

@@ -34,8 +34,18 @@ type SSHConfig struct {
 	HostKey          string          `json:"hostKey"`
 	UserKey          string          `json:"userKey"`
 	Keys             []*SSHPublicKey `json:"keys,omitempty"`
-	AddUserPrincipal string          `json:"addUserPrincipal"`
-	AddUserCommand   string          `json:"addUserCommand"`
+	AddUserPrincipal string          `json:"addUserPrincipal,omitempty"`
+	AddUserCommand   string          `json:"addUserCommand,omitempty"`
+	Bastion          *Bastion        `json:"bastion,omitempty"`
+}
+
+// Bastion contains the custom properties used on bastion.
+type Bastion struct {
+	Hostname string `json:"hostname"`
+	User     string `json:"user,omitempty"`
+	Port     string `json:"port,omitempty"`
+	Command  string `json:"cmd,omitempty"`
+	Flags    string `json:"flags,omitempty"`
 }
 
 // Validate checks the fields in SSHConfig.
@@ -157,6 +167,24 @@ func (a *Authority) GetSSHConfig(typ string, data map[string]string) ([]template
 	return output, nil
 }
 
+// GetSSHBastion returns the bastion configuration, for the given pair user,
+// hostname.
+func (a *Authority) GetSSHBastion(user string, hostname string) (*Bastion, error) {
+	if a.sshBastionFunc != nil {
+		return a.sshBastionFunc(user, hostname)
+	}
+	if a.config.SSH != nil {
+		if a.config.SSH.Bastion != nil && a.config.SSH.Bastion.Hostname != "" {
+			return a.config.SSH.Bastion, nil
+		}
+		return nil, nil
+	}
+	return nil, &apiError{
+		err:  errors.New("getSSHBastion: ssh is not configured"),
+		code: http.StatusNotFound,
+	}
+}
+
 // authorizeSSHSign loads the provisioner from the token, checks that it has not
 // been used again and calls the provisioner AuthorizeSSHSign method. Returns a
 // list of methods to apply to the signing flow.

authority/ssh_test.go

@@ -10,6 +10,7 @@ import (
 	"testing"
 	"time"
 
+	"github.com/pkg/errors"
 	"github.com/smallstep/assert"
 	"github.com/smallstep/certificates/authority/provisioner"
 	"github.com/smallstep/certificates/db"
@@ -598,3 +599,48 @@ func TestSSHPublicKey_PublicKey(t *testing.T) {
 		})
 	}
 }
+
+func TestAuthority_GetSSHBastion(t *testing.T) {
+	bastion := &Bastion{
+		Hostname: "bastion.local",
+		Port:     "2222",
+	}
+	type fields struct {
+		config         *Config
+		sshBastionFunc func(user, hostname string) (*Bastion, error)
+	}
+	type args struct {
+		user     string
+		hostname string
+	}
+	tests := []struct {
+		name    string
+		fields  fields
+		args    args
+		want    *Bastion
+		wantErr bool
+	}{
+		{"config", fields{&Config{SSH: &SSHConfig{Bastion: bastion}}, nil}, args{"user", "host.local"}, bastion, false},
+		{"nil", fields{&Config{SSH: &SSHConfig{Bastion: nil}}, nil}, args{"user", "host.local"}, nil, false},
+		{"empty", fields{&Config{SSH: &SSHConfig{Bastion: &Bastion{}}}, nil}, args{"user", "host.local"}, nil, false},
+		{"func", fields{&Config{}, func(_, _ string) (*Bastion, error) { return bastion, nil }}, args{"user", "host.local"}, bastion, false},
+		{"func err", fields{&Config{}, func(_, _ string) (*Bastion, error) { return nil, errors.New("foo") }}, args{"user", "host.local"}, nil, true},
+		{"error", fields{&Config{SSH: nil}, nil}, args{"user", "host.local"}, nil, true},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			a := &Authority{
+				config:         tt.fields.config,
+				sshBastionFunc: tt.fields.sshBastionFunc,
+			}
+			got, err := a.GetSSHBastion(tt.args.user, tt.args.hostname)
+			if (err != nil) != tt.wantErr {
+				t.Errorf("Authority.GetSSHBastion() error = %v, wantErr %v", err, tt.wantErr)
+				return
+			}
+			if !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("Authority.GetSSHBastion() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}