Add proxy support (#1120)

* - Read proxy env variables and config settings
- Define a function to test that a given path is an active UDS

* Expand paths to the OS user's home directory if they start with "~/" or "%USERPROFILE%\".

* Switch from using "os/user" and `user.Current()` for finding the OS user's home dir, to using "os" and `os.UserHomeDir()`. It requires Go 1.12+.

* Use the UNIX Domain Socket when making connections

* Add SRC_PROXY_SOCKET to the usage output, and remove config settings for a proxy URL.

* Document expandHomeDir function

* Add support for HTTP(S) and SOCKS5 proxies

* Mollify tests

* Add tests

* Refactor: move the proxy handling to a separate file.

* Add tests for a UNIX Domain Socket.

* Fix analysis of url schemes

* Ad tests for socks proxies in the config

* SOCKS proxies work OOTB, so remove the manual dialing for them.

* Use `tls.HandshakeContext`

* - add a proxy test script
- remove "endpoint" from all of the proxy names. The environment variable is now "SRC_PROXY"
- clean up the http(s) proxy dialing code. Experiemented with using http.Request instead of spelling out the CONNECT request manually, but it had enough quircks that I went back to spelling it out manually.
- Add more desriptive messages to the socket config test.

* fix  socket test by shortening the length of the file path - UNIX socket paths need to be less than 108-ish characters.

* Fix parameter capitalization

* Add comment about th UDS path length to main_test.go

* Fix formatting in usage message

* Whoops; meant to use `w` instead of `v`! Thanks for catching that.

Co-authored-by: Camden Cheek <camden@ccheek.com>

* Whoops; meant to use `w` instead of `v`! Thanks for catching that.

Co-authored-by: Camden Cheek <camden@ccheek.com>

* Update comment about InsecureSkipVerify

* Make CHANGELOG entry

---------

Co-authored-by: Camden Cheek <camden@ccheek.com>

Author: peterguy

CHANGELOG.md

@@ -11,6 +11,10 @@ All notable changes to `src-cli` are documented in this file.
 
 ## Unreleased
 
+### Added
+
+- Support HTTP(S), SOCKS5, and UNIX Domain Socket proxies via SRC_PROXY environment variable. [#1120](https://github.com/sourcegraph/src-cli/pull/1120)
+
 ## 5.8.1
 
 ### Fixed

cmd/src/login.go

@@ -81,7 +81,7 @@ func loginCmd(ctx context.Context, cfg *config, client api.Client, endpointArg s
 
 	if cfg.ConfigFilePath != "" {
 		fmt.Fprintln(out)
-		fmt.Fprintf(out, "⚠️  Warning: Configuring src with a JSON file is deprecated. Please migrate to using the env vars SRC_ENDPOINT and SRC_ACCESS_TOKEN instead, and then remove %s. See https://github.com/sourcegraph/src-cli#readme for more information.\n", cfg.ConfigFilePath)
+		fmt.Fprintf(out, "⚠️  Warning: Configuring src with a JSON file is deprecated. Please migrate to using the env vars SRC_ENDPOINT, SRC_ACCESS_TOKEN, and SRC_PROXY instead, and then remove %s. See https://github.com/sourcegraph/src-cli#readme for more information.\n", cfg.ConfigFilePath)
 	}
 
 	noToken := cfg.AccessToken == ""

cmd/src/login_test.go

@@ -49,7 +49,7 @@ func TestLogin(t *testing.T) {
 		if err != cmderrors.ExitCode1 {
 			t.Fatal(err)
 		}
-		wantOut := "⚠️  Warning: Configuring src with a JSON file is deprecated. Please migrate to using the env vars SRC_ENDPOINT and SRC_ACCESS_TOKEN instead, and then remove f. See https://github.com/sourcegraph/src-cli#readme for more information.\n\n❌ Problem: No access token is configured.\n\n🛠  To fix: Create an access token at https://example.com/user/settings/tokens, then set the following environment variables:\n\n   SRC_ENDPOINT=https://example.com\n   SRC_ACCESS_TOKEN=(the access token you just created)\n\n   To verify that it's working, run this command again."
+		wantOut := "⚠️  Warning: Configuring src with a JSON file is deprecated. Please migrate to using the env vars SRC_ENDPOINT, SRC_ACCESS_TOKEN, and SRC_PROXY instead, and then remove f. See https://github.com/sourcegraph/src-cli#readme for more information.\n\n❌ Problem: No access token is configured.\n\n🛠  To fix: Create an access token at https://example.com/user/settings/tokens, then set the following environment variables:\n\n   SRC_ENDPOINT=https://example.com\n   SRC_ACCESS_TOKEN=(the access token you just created)\n\n   To verify that it's working, run this command again."
 		if out != wantOut {
 			t.Errorf("got output %q, want %q", out, wantOut)
 		}

cmd/src/main.go

@@ -5,8 +5,9 @@ import (
 	"flag"
 	"io"
 	"log"
+	"net"
+	"net/url"
 	"os"
-	"os/user"
 	"path/filepath"
 	"strings"
 
@@ -25,6 +26,20 @@ Usage:
 Environment variables
 	SRC_ACCESS_TOKEN  Sourcegraph access token
 	SRC_ENDPOINT      endpoint to use, if unset will default to "https://sourcegraph.com"
+	SRC_PROXY         A proxy to use for proxying requests to the Sourcegraph endpoint.
+	                  Supports HTTP(S), SOCKS5/5h, and UNIX Domain Socket proxies.
+					  If a UNIX Domain Socket, the path can be either an absolute path, 
+					  or can start with ~/ or %USERPROFILE%\ for a path in the user's home directory.
+					  Examples:
+						- https://localhost:3080
+						- https://<user>:<password>localhost:8080
+						- socks5h://localhost:1080
+						- socks5://<username>:<password>@localhost:1080
+						- unix://~/src-proxy.sock
+						- unix://%USERPROFILE%\src-proxy.sock
+						- ~/src-proxy.sock
+						- %USERPROFILE%\src-proxy.sock
+						- C:\some\path\src-proxy.sock
 
 The options are:
 
@@ -83,8 +98,10 @@ type config struct {
 	Endpoint          string            `json:"endpoint"`
 	AccessToken       string            `json:"accessToken"`
 	AdditionalHeaders map[string]string `json:"additionalHeaders"`
-
-	ConfigFilePath string
+	Proxy             string            `json:"proxy"`
+	ProxyURL          *url.URL
+	ProxyPath         string
+	ConfigFilePath    string
 }
 
 // apiClient returns an api.Client built from the configuration.
@@ -95,32 +112,25 @@ func (c *config) apiClient(flags *api.Flags, out io.Writer) api.Client {
 		AdditionalHeaders: c.AdditionalHeaders,
 		Flags:             flags,
 		Out:               out,
+		ProxyURL:          c.ProxyURL,
+		ProxyPath:         c.ProxyPath,
 	})
 }
 
-var testHomeDir string // used by tests to mock the user's $HOME
-
 // readConfig reads the config file from the given path.
 func readConfig() (*config, error) {
-	cfgPath := *configPath
+	cfgFile := *configPath
 	userSpecified := *configPath != ""
 
-	var homeDir string
-	if testHomeDir != "" {
-		homeDir = testHomeDir
-	} else {
-		u, err := user.Current()
-		if err != nil {
-			return nil, err
-		}
-		homeDir = u.HomeDir
+	if !userSpecified {
+		cfgFile = "~/src-config.json"
 	}
 
-	if !userSpecified {
-		cfgPath = filepath.Join(homeDir, "src-config.json")
-	} else if strings.HasPrefix(cfgPath, "~/") {
-		cfgPath = filepath.Join(homeDir, cfgPath[2:])
+	cfgPath, err := expandHomeDir(cfgFile)
+	if err != nil {
+		return nil, err
 	}
+
 	data, err := os.ReadFile(os.ExpandEnv(cfgPath))
 	if err != nil && (!os.IsNotExist(err) || userSpecified) {
 		return nil, err
@@ -135,10 +145,12 @@ func readConfig() (*config, error) {
 
 	envToken := os.Getenv("SRC_ACCESS_TOKEN")
 	envEndpoint := os.Getenv("SRC_ENDPOINT")
+	envProxy := os.Getenv("SRC_PROXY")
 
 	if userSpecified {
-		// If a config file is present, either zero or both environment variables must be present.
+		// If a config file is present, either zero or both required environment variables must be present.
 		// We don't want to partially apply environment variables.
+		// Note that SRC_PROXY is optional so we don't test for it.
 		if envToken == "" && envEndpoint != "" {
 			return nil, errConfigMerge
 		}
@@ -157,6 +169,60 @@ func readConfig() (*config, error) {
 	if cfg.Endpoint == "" {
 		cfg.Endpoint = "https://sourcegraph.com"
 	}
+	if envProxy != "" {
+		cfg.Proxy = envProxy
+	}
+
+	if cfg.Proxy != "" {
+
+		parseEndpoint := func(endpoint string) (scheme string, address string) {
+			parts := strings.SplitN(endpoint, "://", 2)
+			if len(parts) == 2 {
+				return parts[0], parts[1]
+			}
+			return "", endpoint
+		}
+
+		urlSchemes := []string{"http", "https", "socks", "socks5", "socks5h"}
+
+		isURLScheme := func(scheme string) bool {
+			for _, s := range urlSchemes {
+				if scheme == s {
+					return true
+				}
+			}
+			return false
+		}
+
+		scheme, address := parseEndpoint(cfg.Proxy)
+
+		if isURLScheme(scheme) {
+			endpoint := cfg.Proxy
+			// assume socks means socks5, because that's all we support
+			if scheme == "socks" {
+				endpoint = "socks5://" + address
+			}
+			cfg.ProxyURL, err = url.Parse(endpoint)
+			if err != nil {
+				return nil, err
+			}
+		} else if scheme == "" || scheme == "unix" {
+			path, err := expandHomeDir(address)
+			if err != nil {
+				return nil, err
+			}
+			isValidUDS, err := isValidUnixSocket(path)
+			if err != nil {
+				return nil, errors.Newf("Invalid proxy configuration: %w", err)
+			}
+			if !isValidUDS {
+				return nil, errors.Newf("invalid proxy socket: %s", path)
+			}
+			cfg.ProxyPath = path
+		} else {
+			return nil, errors.Newf("invalid proxy endpoint: %s", cfg.Proxy)
+		}
+	}
 
 	cfg.AdditionalHeaders = parseAdditionalHeaders()
 	// Ensure that we're not clashing additonal headers
@@ -178,3 +244,65 @@ func readConfig() (*config, error) {
 func cleanEndpoint(urlStr string) string {
 	return strings.TrimSuffix(urlStr, "/")
 }
+
+// isValidUnixSocket checks if the given path is a valid Unix socket.
+//
+// Parameters:
+//   - path: A string representing the file path to check.
+//
+// Returns:
+//   - bool: true if the path is a valid Unix socket, false otherwise.
+//   - error: nil if the check was successful, or an error if an unexpected issue occurred.
+//
+// The function attempts to establish a connection to the Unix socket at the given path.
+// If the connection succeeds, it's considered a valid Unix socket.
+// If the file doesn't exist, it returns false without an error.
+// For any other errors, it returns false and the encountered error.
+func isValidUnixSocket(path string) (bool, error) {
+	conn, err := net.Dial("unix", path)
+	if err != nil {
+		if os.IsNotExist(err) {
+			return false, nil
+		}
+		return false, errors.Newf("Not a UNIX Domain Socket: %v: %w", path, err)
+	}
+	defer conn.Close()
+
+	return true, nil
+}
+
+var testHomeDir string // used by tests to mock the user's $HOME
+
+// expandHomeDir expands to the user's home directory a tilde (~) or %USERPROFILE% at the beginning of a file path.
+//
+// Parameters:
+//   - filePath: A string representing the file path that may start with "~/" or "%USERPROFILE%\".
+//
+// Returns:
+//   - string: The expanded file path with the home directory resolved.
+//   - error: An error if the user's home directory cannot be determined.
+//
+// The function handles both Unix-style paths starting with "~/" and Windows-style paths starting with "%USERPROFILE%\".
+// It uses the testHomeDir variable for testing purposes if set, otherwise it uses os.UserHomeDir() to get the user's home directory.
+// If the input path doesn't start with either prefix, it returns the original path unchanged.
+func expandHomeDir(filePath string) (string, error) {
+	if strings.HasPrefix(filePath, "~/") || strings.HasPrefix(filePath, "%USERPROFILE%\\") {
+		var homeDir string
+		if testHomeDir != "" {
+			homeDir = testHomeDir
+		} else {
+			hd, err := os.UserHomeDir()
+			if err != nil {
+				return "", err
+			}
+			homeDir = hd
+		}
+
+		if strings.HasPrefix(filePath, "~/") {
+			return filepath.Join(homeDir, filePath[2:]), nil
+		}
+		return filepath.Join(homeDir, filePath[14:]), nil
+	}
+
+	return filePath, nil
+}