Add customized login success output for TFC/E

When logging in to Terraform Cloud or Terraform Enterprise, change the
success output to be a bit more customized for the platform. For
Terraform Cloud, fetch a dynamic welcome banner that intentionally fails
open and defaults to a hardcoded message if its not available for any
reason.

command/login.go

@@ -4,8 +4,10 @@ import (
 	"context"
 	"crypto/sha256"
 	"encoding/base64"
+	"encoding/json"
 	"errors"
 	"fmt"
+	"io/ioutil"
 	"log"
 	"math/rand"
 	"net"
@@ -131,9 +133,9 @@ func (c *LoginCommand) Run(args []string) int {
 	}
 
 	// If login service is unavailable, check for a TFE v2 API as fallback
-	var service *url.URL
+	var tfeservice *url.URL
 	if clientConfig == nil {
-		service, err = host.ServiceURL("tfe.v2")
+		tfeservice, err = host.ServiceURL("tfe.v2")
 		switch err.(type) {
 		case nil:
 			// Success!
@@ -184,6 +186,8 @@ func (c *LoginCommand) Run(args []string) int {
 			oauthToken, tokenDiags = c.interactiveGetTokenByCode(hostname, credsCtx, clientConfig)
 		case clientConfig.SupportedGrantTypes.Has(disco.OAuthOwnerPasswordGrant) && hostname == svchost.Hostname("app.terraform.io"):
 			// The password grant type is allowed only for Terraform Cloud SaaS.
+			// Note this case is purely theoretical at this point, as TFC currently uses
+			// its own bespoke login protocol (tfe)
 			oauthToken, tokenDiags = c.interactiveGetTokenByPassword(hostname, credsCtx, clientConfig)
 		default:
 			tokenDiags = tokenDiags.Append(tfdiags.Sourceless(
@@ -195,8 +199,8 @@ func (c *LoginCommand) Run(args []string) int {
 		if oauthToken != nil {
 			token = svcauth.HostCredentialsToken(oauthToken.AccessToken)
 		}
-	} else if service != nil {
-		token, tokenDiags = c.interactiveGetTokenByUI(hostname, credsCtx, service)
+	} else if tfeservice != nil {
+		token, tokenDiags = c.interactiveGetTokenByUI(hostname, credsCtx, tfeservice)
 	}
 
 	diags = diags.Append(tokenDiags)
@@ -220,19 +224,96 @@ func (c *LoginCommand) Run(args []string) int {
 	}
 
 	c.Ui.Output("\n---------------------------------------------------------------------------------\n")
-	c.Ui.Output(
-		fmt.Sprintf(
-			c.Colorize().Color(strings.TrimSpace(`
+	if hostname == "app.terraform.io" { // Terraform Cloud
+		var motd struct {
+			Message string        `json:"msg"`
+			Errors  []interface{} `json:"errors"`
+		}
+
+		// Throughout the entire process of fetching a MOTD from TFC, use a default
+		// message if the platform-provided message is unavailable for any reason -
+		// be it the service isn't provided, the request failed, or any sort of
+		// platform error returned.
+
+		motdServiceURL, err := host.ServiceURL("motd.v1")
+		if err != nil {
+			c.outputDefaultTFCLoginSuccess(err)
+			return 0
+		}
+
+		req, err := http.NewRequest("GET", motdServiceURL.String(), nil)
+		if err != nil {
+			c.outputDefaultTFCLoginSuccess(err)
+			return 0
+		}
+
+		req.Header.Set("Authorization", "Bearer "+token.Token())
+
+		resp, err := httpclient.New().Do(req)
+		if err != nil {
+			c.outputDefaultTFCLoginSuccess(err)
+			return 0
+		}
+
+		body, err := ioutil.ReadAll(resp.Body)
+		if err != nil {
+			c.outputDefaultTFCLoginSuccess(err)
+			return 0
+		}
+
+		defer resp.Body.Close()
+		json.Unmarshal(body, &motd)
+
+		if motd.Errors == nil && motd.Message != "" {
+			c.Ui.Output(
+				c.Colorize().Color(motd.Message),
+			)
+			return 0
+		} else {
+			c.outputDefaultTFCLoginSuccess(fmt.Errorf("platform responded with errors or an empty message"))
+			return 0
+		}
+	}
+
+	if tfeservice != nil { // Terraform Enterprise
+		c.outputDefaultTFELoginSuccess(dispHostname)
+	} else {
+		c.Ui.Output(
+			fmt.Sprintf(
+				c.Colorize().Color(strings.TrimSpace(`
 [green][bold]Success![reset] [bold]Terraform has obtained and saved an API token.[reset]
 
 The new API token will be used for any future Terraform command that must make
 authenticated requests to %s.
+`)),
+				dispHostname,
+			) + "\n",
+		)
+	}
+
+	return 0
+}
+
+func (c *LoginCommand) outputDefaultTFELoginSuccess(dispHostname string) {
+	c.Ui.Output(
+		fmt.Sprintf(
+			c.Colorize().Color(strings.TrimSpace(`
+[green][bold]Success![reset] [bold]Logged in to Terraform Enterprise (%s)[reset]
 `)),
 			dispHostname,
 		) + "\n",
 	)
+}
 
-	return 0
+func (c *LoginCommand) outputDefaultTFCLoginSuccess(err error) {
+	log.Printf("[TRACE] login: An error occurred attempting to fetch a message of the day for Terraform Cloud: %s", err)
+	c.Ui.Output(
+		fmt.Sprintf(
+			c.Colorize().Color(strings.TrimSpace(`
+[green][bold]Success![reset] [bold]Logged in to Terraform Cloud[reset]
+`)),
+		) + "\n",
+	)
 }
 
 // Help implements cli.Command.

command/login_test.go

@@ -56,16 +56,6 @@ func TestLogin(t *testing.T) {
 			svcs := disco.NewWithCredentialsSource(creds)
 			svcs.SetUserAgent(httpclient.TerraformUserAgent(version.String()))
 
-			svcs.ForceHostServices(svchost.Hostname("app.terraform.io"), map[string]interface{}{
-				"login.v1": map[string]interface{}{
-					// On app.terraform.io we use password-based authorization.
-					// That's the only hostname that it's permitted for, so we can't
-					// use a fake hostname here.
-					"client":      "terraformcli",
-					"token":       s.URL + "/token",
-					"grant_types": []interface{}{"password"},
-				},
-			})
 			svcs.ForceHostServices(svchost.Hostname("example.com"), map[string]interface{}{
 				"login.v1": map[string]interface{}{
 					// For this fake hostname we'll use a conventional OAuth flow,
@@ -86,9 +76,17 @@ func TestLogin(t *testing.T) {
 					"scopes": []interface{}{"app1.full_access", "app2.read_only"},
 				},
 			})
+			svcs.ForceHostServices(svchost.Hostname("app.terraform.io"), map[string]interface{}{
+				// This represents Terraform Cloud, which does not yet support the
+				// login API, but does support its own bespoke tokens API.
+				"tfe.v2":   ts.URL + "/api/v2",
+				"tfe.v2.1": ts.URL + "/api/v2",
+				"tfe.v2.2": ts.URL + "/api/v2",
+				"motd.v1":  ts.URL + "/api/terraform/motd",
+			})
 			svcs.ForceHostServices(svchost.Hostname("tfe.acme.com"), map[string]interface{}{
 				// This represents a Terraform Enterprise instance which does not
-				// yet support the login API, but does support the TFE tokens API.
+				// yet support the login API, but does support its own bespoke tokens API.
 				"tfe.v2":   ts.URL + "/api/v2",
 				"tfe.v2.1": ts.URL + "/api/v2",
 				"tfe.v2.2": ts.URL + "/api/v2",
@@ -109,13 +107,14 @@ func TestLogin(t *testing.T) {
 		}
 	}
 
-	t.Run("defaulting to app.terraform.io with password flow", loginTestCase(func(t *testing.T, c *LoginCommand, ui *cli.MockUi) {
+	t.Run("app.terraform.io (no login support)", loginTestCase(func(t *testing.T, c *LoginCommand, ui *cli.MockUi) {
+		// Enter "yes" at the consent prompt, then paste a token with some
+		// accidental whitespace.
 		defer testInputMap(t, map[string]string{
-			"approve":  "yes",
-			"username": "foo",
-			"password": "bar",
+			"approve": "yes",
+			"token":   "  good-token ",
 		})()
-		status := c.Run(nil)
+		status := c.Run([]string{"app.terraform.io"})
 		if status != 0 {
 			t.Fatalf("unexpected error code %d\nstderr:\n%s", status, ui.ErrorWriter.String())
 		}
@@ -128,6 +127,9 @@ func TestLogin(t *testing.T) {
 		if got, want := creds.Token(), "good-token"; got != want {
 			t.Errorf("wrong token %q; want %q", got, want)
 		}
+		if got, want := ui.OutputWriter.String(), "Welcome to Terraform Cloud!"; !strings.Contains(got, want) {
+			t.Errorf("expected output to contain %q, but was:\n%s", want, got)
+		}
 	}))
 
 	t.Run("example.com with authorization code flow", loginTestCase(func(t *testing.T, c *LoginCommand, ui *cli.MockUi) {
@@ -148,6 +150,10 @@ func TestLogin(t *testing.T) {
 		if got, want := creds.Token(), "good-token"; got != want {
 			t.Errorf("wrong token %q; want %q", got, want)
 		}
+
+		if got, want := ui.OutputWriter.String(), "Terraform has obtained and saved an API token."; !strings.Contains(got, want) {
+			t.Errorf("expected output to contain %q, but was:\n%s", want, got)
+		}
 	}))
 
 	t.Run("example.com results in no scopes", loginTestCase(func(t *testing.T, c *LoginCommand, ui *cli.MockUi) {
@@ -179,6 +185,10 @@ func TestLogin(t *testing.T) {
 		if got, want := creds.Token(), "good-token"; got != want {
 			t.Errorf("wrong token %q; want %q", got, want)
 		}
+
+		if got, want := ui.OutputWriter.String(), "Terraform has obtained and saved an API token."; !strings.Contains(got, want) {
+			t.Errorf("expected output to contain %q, but was:\n%s", want, got)
+		}
 	}))
 
 	t.Run("with-scopes.example.com results in expected scopes", loginTestCase(func(t *testing.T, c *LoginCommand, ui *cli.MockUi) {
@@ -216,6 +226,10 @@ func TestLogin(t *testing.T) {
 		if got, want := creds.Token(), "good-token"; got != want {
 			t.Errorf("wrong token %q; want %q", got, want)
 		}
+
+		if got, want := ui.OutputWriter.String(), "Logged in to Terraform Enterprise"; !strings.Contains(got, want) {
+			t.Errorf("expected output to contain %q, but was:\n%s", want, got)
+		}
 	}))
 
 	t.Run("TFE host without login support, incorrectly pasted token", loginTestCase(func(t *testing.T, c *LoginCommand, ui *cli.MockUi) {

command/testdata/login-tfe-server/tfeserver.go

@@ -11,6 +11,7 @@ import (
 const (
 	goodToken      = "good-token"
 	accountDetails = `{"data":{"id":"user-abc123","type":"users","attributes":{"username":"testuser","email":"testuser@example.com"}}}`
+	MOTD           = `{"msg":"Welcome to Terraform Cloud!"}`
 )
 
 // Handler is an implementation of net/http.Handler that provides a stub
@@ -29,6 +30,8 @@ func (h handler) ServeHTTP(resp http.ResponseWriter, req *http.Request) {
 		h.servePing(resp, req)
 	case "/api/v2/account/details":
 		h.serveAccountDetails(resp, req)
+	case "/api/terraform/motd":
+		h.serveMOTD(resp, req)
 	default:
 		fmt.Printf("404 when fetching %s\n", req.URL.String())
 		http.Error(resp, `{"errors":[{"status":"404","title":"not found"}]}`, http.StatusNotFound)
@@ -49,6 +52,11 @@ func (h handler) serveAccountDetails(resp http.ResponseWriter, req *http.Request
 	resp.Write([]byte(accountDetails))
 }
 
+func (h handler) serveMOTD(resp http.ResponseWriter, req *http.Request) {
+	resp.WriteHeader(http.StatusOK)
+	resp.Write([]byte(MOTD))
+}
+
 func init() {
 	Handler = handler{}
 }