feat: Support --header for CLI commands to support proxies (#4008)

Fixes #3527.

cli/cliflag/cliflag.go

@@ -61,6 +61,18 @@ func StringVarP(flagset *pflag.FlagSet, p *string, name string, shorthand string
 	flagset.StringVarP(p, name, shorthand, v, fmtUsage(usage, env))
 }
 
+func StringArray(flagset *pflag.FlagSet, name, shorthand, env string, def []string, usage string) {
+	v, ok := os.LookupEnv(env)
+	if !ok || v == "" {
+		if v == "" {
+			def = []string{}
+		} else {
+			def = strings.Split(v, ",")
+		}
+	}
+	flagset.StringArrayP(name, shorthand, def, fmtUsage(usage, env))
+}
+
 func StringArrayVarP(flagset *pflag.FlagSet, ptr *[]string, name string, shorthand string, env string, def []string, usage string) {
 	val, ok := os.LookupEnv(env)
 	if ok {

cli/login.go

@@ -66,7 +66,10 @@ func login() *cobra.Command {
 				serverURL.Scheme = "https"
 			}
 
-			client := codersdk.New(serverURL)
+			client, err := createUnauthenticatedClient(cmd, serverURL)
+			if err != nil {
+				return err
+			}
 
 			// Try to check the version of the server prior to logging in.
 			// It may be useful to warn the user if they are trying to login

cli/root.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"flag"
 	"fmt"
+	"net/http"
 	"net/url"
 	"os"
 	"strings"
@@ -41,6 +42,7 @@ const (
 	varAgentToken       = "agent-token"
 	varAgentURL         = "agent-url"
 	varGlobalConfig     = "global-config"
+	varHeader           = "header"
 	varNoOpen           = "no-open"
 	varNoVersionCheck   = "no-version-warning"
 	varNoFeatureWarning = "no-feature-warning"
@@ -174,6 +176,7 @@ func Root(subcommands []*cobra.Command) *cobra.Command {
 	cliflag.String(cmd.PersistentFlags(), varAgentURL, "", "CODER_AGENT_URL", "", "Specify the URL for an agent to access your deployment.")
 	_ = cmd.PersistentFlags().MarkHidden(varAgentURL)
 	cliflag.String(cmd.PersistentFlags(), varGlobalConfig, "", "CODER_CONFIG_DIR", configdir.LocalConfig("coderv2"), "Specify the path to the global `coder` config directory.")
+	cliflag.StringArray(cmd.PersistentFlags(), varHeader, "", "CODER_HEADER", []string{}, "HTTP headers added to all requests. Provide as \"Key=Value\"")
 	cmd.PersistentFlags().Bool(varForceTty, false, "Force the `coder` command to run as if connected to a TTY.")
 	_ = cmd.PersistentFlags().MarkHidden(varForceTty)
 	cmd.PersistentFlags().Bool(varNoOpen, false, "Block automatically opening URLs in the browser.")
@@ -237,8 +240,32 @@ func CreateClient(cmd *cobra.Command) (*codersdk.Client, error) {
 			return nil, err
 		}
 	}
+	client, err := createUnauthenticatedClient(cmd, serverURL)
+	if err != nil {
+		return nil, err
+	}
+	client.SessionToken = token
+	return client, nil
+}
+
+func createUnauthenticatedClient(cmd *cobra.Command, serverURL *url.URL) (*codersdk.Client, error) {
 	client := codersdk.New(serverURL)
-	client.SessionToken = strings.TrimSpace(token)
+	headers, err := cmd.Flags().GetStringArray(varHeader)
+	if err != nil {
+		return nil, err
+	}
+	transport := &headerTransport{
+		transport: http.DefaultTransport,
+		headers:   map[string]string{},
+	}
+	for _, header := range headers {
+		parts := strings.SplitN(header, "=", 2)
+		if len(parts) < 2 {
+			return nil, xerrors.Errorf("split header %q had less than two parts", header)
+		}
+		transport.headers[parts[0]] = parts[1]
+	}
+	client.HTTPClient.Transport = transport
 	return client, nil
 }
 
@@ -530,3 +557,15 @@ func checkWarnings(cmd *cobra.Command, client *codersdk.Client) error {
 
 	return nil
 }
+
+type headerTransport struct {
+	transport http.RoundTripper
+	headers   map[string]string
+}
+
+func (h *headerTransport) RoundTrip(req *http.Request) (*http.Response, error) {
+	for k, v := range h.headers {
+		req.Header.Add(k, v)
+	}
+	return h.transport.RoundTrip(req)
+}

cli/root_test.go

@@ -2,9 +2,12 @@ package cli_test
 
 import (
 	"bytes"
+	"net/http"
+	"net/http/httptest"
 	"testing"
 
 	"github.com/spf13/cobra"
+	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 	"golang.org/x/xerrors"
 
@@ -129,4 +132,25 @@ func TestRoot(t *testing.T) {
 		require.Contains(t, output, buildinfo.Version(), "has version")
 		require.Contains(t, output, buildinfo.ExternalURL(), "has url")
 	})
+
+	t.Run("Header", func(t *testing.T) {
+		t.Parallel()
+
+		done := make(chan struct{})
+		srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			assert.Equal(t, "wow", r.Header.Get("X-Testing"))
+			w.WriteHeader(http.StatusGone)
+			select {
+			case <-done:
+				close(done)
+			default:
+			}
+		}))
+		defer srv.Close()
+		buf := new(bytes.Buffer)
+		cmd, _ := clitest.New(t, "--header", "X-Testing=wow", "login", srv.URL)
+		cmd.SetOut(buf)
+		// This won't succeed, because we're using the login cmd to assert requests.
+		_ = cmd.Execute()
+	})
 }