login: add oauth escape hatch

Signed-off-by: Laura Brehm <laurabrehm@hey.com>

cli/command/registry/login.go

@@ -4,6 +4,8 @@ import (
 	"context"
 	"fmt"
 	"io"
+	"os"
+	"strconv"
 	"strings"
 
 	"github.com/docker/cli/cli"
@@ -141,9 +143,22 @@ func loginWithStoredCredentials(ctx context.Context, dockerCli command.Cli, auth
 	return &response, err
 }
 
+const OauthLoginEscapeHatchEnvVar = "DOCKER_CLI_DISABLE_OAUTH_LOGIN"
+
+func isOauthLoginDisabled() bool {
+	if v := os.Getenv(OauthLoginEscapeHatchEnvVar); v != "" {
+		enabled, err := strconv.ParseBool(v)
+		if err != nil {
+			return false
+		}
+		return enabled
+	}
+	return false
+}
+
 func loginUser(ctx context.Context, dockerCli command.Cli, opts loginOptions, defaultUsername, serverAddress string) (*registrytypes.AuthenticateOKBody, error) {
 	// If we're logging into the index server and the user didn't provide a username or password, use the device flow
-	if serverAddress == registry.IndexServer && opts.user == "" && opts.password == "" {
+	if serverAddress == registry.IndexServer && opts.user == "" && opts.password == "" && !isOauthLoginDisabled() {
 		response, err := loginWithDeviceCodeFlow(ctx, dockerCli)
 		// if the error represents a failure to initiate the device-code flow,
 		// then we fallback to regular cli credentials login

cli/command/registry/login_test.go

@@ -228,3 +228,47 @@ func TestLoginTermination(t *testing.T) {
 		assert.ErrorIs(t, err, command.ErrPromptTerminated)
 	}
 }
+
+func TestIsOauthLoginDisabled(t *testing.T) {
+	testCases := []struct {
+		envVar   string
+		disabled bool
+	}{
+		{
+			envVar:   "",
+			disabled: false,
+		},
+		{
+			envVar:   "bork",
+			disabled: false,
+		},
+		{
+			envVar:   "0",
+			disabled: false,
+		},
+		{
+			envVar:   "false",
+			disabled: false,
+		},
+		{
+			envVar:   "true",
+			disabled: true,
+		},
+		{
+			envVar:   "TRUE",
+			disabled: true,
+		},
+		{
+			envVar:   "1",
+			disabled: true,
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Setenv(OauthLoginEscapeHatchEnvVar, tc.envVar)
+
+		disabled := isOauthLoginDisabled()
+
+		assert.Equal(t, disabled, tc.disabled)
+	}
+}