coder
diff --git a/‎coderd/externalauth/externalauth.go
Lines changed: 26 additions & 6 deletions b/‎coderd/externalauth/externalauth.go
Lines changed: 26 additions & 6 deletions
diff --git a/‎coderd/externalauth_test.go
Lines changed: 25 additions & 0 deletions b/‎coderd/externalauth_test.go
Lines changed: 25 additions & 0 deletions
@@ -6,9 +6,11 @@ import (
 	"encoding/json"
 	"fmt"
 	"io"
+	"mime"
 	"net/http"
 	"net/url"
 	"regexp"
+	"strconv"
 	"strings"
 	"time"
 
@@ -321,13 +323,31 @@ func (c *DeviceAuth) AuthorizeDevice(ctx context.Context) (*codersdk.ExternalAut
 	}
 	err = json.NewDecoder(resp.Body).Decode(&r)
 	if err != nil {
-		// Some status codes do not return json payloads, and we should
-		// return a better error.
-		switch resp.StatusCode {
-		case http.StatusTooManyRequests:
-			return nil, xerrors.New("rate limit hit, unable to authorize device. please try again later")
+		mediaType, _, err := mime.ParseMediaType(resp.Header.Get("Content-Type"))
+		if err != nil {
+			mediaType = "unknown"
+		}
+
+		// If the json fails to decode, do a best effort to return a better error.
+		switch {
+		case resp.StatusCode == http.StatusTooManyRequests:
+			retryIn := "please try again later"
+			resetIn := resp.Header.Get("x-ratelimit-reset")
+			if resetIn != "" {
+				// Best effort to tell the user exactly how long they need
+				// to wait for.
+				unix, err := strconv.ParseInt(resetIn, 10, 64)
+				if err == nil {
+					waitFor := time.Unix(unix, 0).Sub(time.Now().Truncate(time.Second))
+					retryIn = fmt.Sprintf(" retry after %s", waitFor.Truncate(time.Second))
+				}
+			}
+			// 429 returns a plaintext payload with a message.
+			return nil, xerrors.New(fmt.Sprintf("rate limit hit, unable to authorize device. %s", retryIn))
+		case mediaType == "application/x-www-form-urlencoded":
+			return nil, xerrors.Errorf("%s payload response is form-url encoded, expected a json payload", resp.StatusCode)
 		default:
-			return nil, fmt.Errorf("status_code=%d: %w", resp.StatusCode, err)
+			return nil, fmt.Errorf("status_code=%d, mediaType=%s: %w", resp.StatusCode, mediaType, err)
 		}
 	}
 	if r.ErrorDescription != "" {
 
@@ -5,6 +5,7 @@ import (
 	"fmt"
 	"net/http"
 	"net/http/httptest"
+	"net/url"
 	"regexp"
 	"strings"
 	"testing"
@@ -363,6 +364,30 @@ func TestExternalAuthDevice(t *testing.T) {
 		_, err := client.ExternalAuthDeviceByID(context.Background(), "test")
 		require.ErrorContains(t, err, "rate limit hit")
 	})
+
+	// If we forget to add the accept header, we get a form encoded body instead.
+	t.Run("FormEncodedBody", func(t *testing.T) {
+		t.Parallel()
+		srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			w.Header().Set("Content-Type", "application/x-www-form-urlencoded")
+			_, _ = w.Write([]byte(url.Values{"access_token": {"hey"}}.Encode()))
+		}))
+		defer srv.Close()
+		client := coderdtest.New(t, &coderdtest.Options{
+			ExternalAuthConfigs: []*externalauth.Config{{
+				ID: "test",
+				DeviceAuth: &externalauth.DeviceAuth{
+					ClientID: "test",
+					CodeURL:  srv.URL,
+					Scopes:   []string{"repo"},
+				},
+			}},
+		})
+		coderdtest.CreateFirstUser(t, client)
+		_, err := client.ExternalAuthDeviceByID(context.Background(), "test")
+		require.Error(t, err)
+		require.ErrorContains(t, err, "is form-url encoded")
+	})
 }
 
 // nolint:bodyclose