Refactor Gemini protocol implementation and improve server architecture

- Move gemini URL parsing from common/ to gemini/ package
- Add structured status codes in gemini/status_codes.go
- Improve error handling with proper Gemini status codes
- Update configuration field naming (Listen -> ListenAddr)
- Add UTF-8 validation for URLs
- Enhance security with better path validation
- Add CLAUDE.md for development guidance
- Include example content in srv/ directory
- Update build system to use standard shell

CLAUDE.md

@@ -0,0 +1,87 @@
+# CLAUDE.md
+
+This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
+
+## Project Overview
+
+Gemserve is a simple Gemini protocol server written in Go that serves static files over TLS-encrypted connections. The Gemini protocol is a lightweight, privacy-focused alternative to HTTP designed for serving text-based content.
+
+## Development Commands
+
+```bash
+# Build, test, and format everything
+make
+
+# Run tests only
+make test
+
+# Build binary to ./dist/gemserve
+make build
+
+# Format code with gofumpt and gci
+make fmt
+
+# Run golangci-lint
+make lint
+
+# Run linter with auto-fix
+make lintfix
+
+# Clean build artifacts
+make clean
+
+# Run the server (after building)
+./dist/gemserve
+
+# Generate TLS certificates for development
+certs/generate.sh
+```
+
+## Architecture
+
+### Core Components
+
+- **main.go**: Entry point with TLS server setup, signal handling, and graceful shutdown
+- **server/**: Request processing, file serving, and Gemini protocol response handling
+- **gemini/**: Gemini protocol implementation (URL parsing, status codes, path normalization)
+- **config/**: CLI-based configuration system
+- **uid/**: Connection ID generation for logging
+
+### Key Patterns
+
+- **Security First**: All file operations use `filepath.IsLocal()` and path cleaning to prevent directory traversal
+- **Error Handling**: Uses structured errors with `xerrors` package for consistent error propagation
+- **Logging**: Structured logging with configurable levels via internal logging package
+- **Testing**: Table-driven tests with parallel execution, heavy focus on security edge cases
+
+### Request Flow
+
+1. TLS connection established on port 1965
+2. Read up to 1KB request (Gemini spec limit)
+3. Parse and normalize Gemini URL
+4. Validate path security (prevent traversal)
+5. Serve file or directory index with appropriate MIME type
+6. Send response with proper Gemini status codes
+
+## Configuration
+
+Server configured via CLI flags:
+- `--listen`: Server address (default: localhost:1965)
+- `--root-path`: Directory to serve files from
+- `--dir-indexing`: Enable directory browsing
+- `--log-level`: Logging verbosity
+- `--response-timeout`: Response timeout in seconds
+
+## Testing Strategy
+
+- **server/server_test.go**: Path security and file serving tests
+- **gemini/url_test.go**: URL parsing and normalization tests
+- Focus on security edge cases (Unicode, traversal attempts, malformed URLs)
+- Use parallel test execution for performance
+
+## Security Considerations
+
+- All connections require TLS certificates (stored in certs/)
+- Path traversal protection is critical - test thoroughly when modifying file serving logic
+- Request size limited to 1KB per Gemini specification
+- Input validation on all URLs and paths

Makefile

@@ -1,4 +1,4 @@
-SHELL := /bin/env oksh
+SHELL := /bin/sh
 export PATH := $(PATH)
 
 all: fmt lintfix tidy test clean build

config/config.go

@@ -14,7 +14,7 @@ type Config struct {
 	ResponseTimeout    int        // Timeout for responses in seconds
 	RootPath           string     // Path to serve files from
 	DirIndexingEnabled bool       // Allow client to browse directories or not
-	Listen             string     // Address to listen on
+	ListenAddr         string     // Address to listen on
 }
 
 var CONFIG Config //nolint:gochecknoglobals
@@ -64,6 +64,6 @@ func GetConfig() *Config {
 		ResponseTimeout:    *responseTimeout,
 		RootPath:           *rootPath,
 		DirIndexingEnabled: *dirIndexing,
-		Listen:             *listen,
+		ListenAddr:         *listen,
 	}
 }

gemini/status_codes.go

@@ -0,0 +1,34 @@
+package gemini
+
+// Gemini status codes as defined in the Gemini spec
+// gemini://geminiprotocol.net/docs/protocol-specification.gmi
+const (
+	// Input group
+	StatusInputExpected          = 10
+	StatusInputExpectedSensitive = 11
+
+	StatusSuccess = 20
+
+	// Redirect group
+	StatusRedirectTemporary = 30
+	StatusRedirectPermanent = 31
+
+	// Temporary failure group
+	StatusTemporaryFailure  = 40
+	StatusServerUnavailable = 41
+	StatusCGIError          = 42
+	StatusProxyError        = 43
+	StatusSlowDown          = 44
+
+	// Permanent failure group
+	StatusPermanentFailure    = 50
+	StatusNotFound            = 51
+	StatusGone                = 52
+	StatusProxyRequestRefused = 53
+	StatusBadRequest          = 59
+
+	// TLS certificate group
+	StatusCertificateRequired      = 60
+	StatusCertificateNotAuthorized = 61
+	StatusCertificateNotValid      = 62
+)

gemini/url.go

@@ -1,4 +1,4 @@
-package common
+package gemini
 
 import (
 	"database/sql/driver"

gemini/url_test.go

@@ -1,4 +1,4 @@
-package common
+package gemini
 
 import (
 	"net/url"

go.mod

@@ -2,12 +2,20 @@ module gemserve
 
 go 1.24.3
 
+toolchain go1.24.4
+
 require (
 	git.antanst.com/antanst/logging v0.0.1
-	git.antanst.com/antanst/xerrors v0.0.1
 	git.antanst.com/antanst/uid v0.0.1
+	git.antanst.com/antanst/xerrors v0.0.1
 	github.com/gabriel-vasile/mimetype v1.4.8
 	github.com/matoous/go-nanoid/v2 v2.1.0
 )
 
 require golang.org/x/net v0.33.0 // indirect
+
+replace git.antanst.com/antanst/xerrors => ../xerrors
+
+replace git.antanst.com/antanst/uid => ../uid
+
+replace git.antanst.com/antanst/logging => ../logging

main.go

@@ -14,12 +14,16 @@ import (
 	"time"
 
 	"gemserve/config"
+	"gemserve/gemini"
 	"gemserve/server"
 	logging "git.antanst.com/antanst/logging"
 	"git.antanst.com/antanst/uid"
 	"git.antanst.com/antanst/xerrors"
 )
 
+// This channel is for handling fatal errors
+// from anywhere in the app. The consumer
+// should log and panic.
 var fatalErrors chan error
 
 func main() {
@@ -37,7 +41,7 @@ func main() {
 func runApp() error {
 	logging.LogInfo("Starting up. Press Ctrl+C to exit")
 
-	listenHost := config.CONFIG.Listen
+	listenAddr := config.CONFIG.ListenAddr
 
 	signals := make(chan os.Signal, 1)
 	signal.Notify(signals, syscall.SIGINT, syscall.SIGTERM)
@@ -45,7 +49,7 @@ func runApp() error {
 	fatalErrors = make(chan error)
 
 	go func() {
-		err := startServer(listenHost)
+		err := startServer(listenAddr)
 		if err != nil {
 			fatalErrors <- xerrors.NewError(err, 0, "Server startup failed", true)
 		}
@@ -62,7 +66,7 @@ func runApp() error {
 	}
 }
 
-func startServer(listenHost string) (err error) {
+func startServer(listenAddr string) (err error) {
 	cert, err := tls.LoadX509KeyPair("certs/server.crt", "certs/server.key")
 	if err != nil {
 		return xerrors.NewError(fmt.Errorf("failed to load certificate: %w", err), 0, "Certificate loading failed", true)
@@ -73,7 +77,7 @@ func startServer(listenHost string) (err error) {
 		MinVersion:   tls.VersionTLS12,
 	}
 
-	listener, err := tls.Listen("tcp", listenHost, tlsConfig)
+	listener, err := tls.Listen("tcp", listenAddr, tlsConfig)
 	if err != nil {
 		return xerrors.NewError(fmt.Errorf("failed to create listener: %w", err), 0, "Listener creation failed", true)
 	}
@@ -87,7 +91,7 @@ func startServer(listenHost string) (err error) {
 		}
 	}(listener)
 
-	logging.LogInfo("Server listening on %s", listenHost)
+	logging.LogInfo("Server listening on %s", listenAddr)
 
 	for {
 		conn, err := listener.Accept()
@@ -106,7 +110,7 @@ func startServer(listenHost string) (err error) {
 					fatalErrors <- asErr
 					return
 				} else {
-					logging.LogWarn("%s %s Connection failed: %d %s (%v)", connId, remoteAddr, asErr.Code, asErr.UserMsg, err)
+					logging.LogWarn("%s %s Connection failed: %v", connId, remoteAddr, err)
 				}
 			}
 		}()
@@ -157,7 +161,7 @@ func handleConnection(conn *tls.Conn, connId string, remoteAddr string) (err err
 			code = xErr.Code
 			responseMsg = xErr.UserMsg
 		} else {
-			code = 50
+			code = gemini.StatusPermanentFailure
 			responseMsg = "server error"
 		}
 		responseHeader = fmt.Sprintf("%d %s", code, responseMsg)

server/server.go

@@ -10,10 +10,11 @@ import (
 	"path/filepath"
 	"strconv"
 	"strings"
+	"unicode/utf8"
 
-	"gemserve/common"
 	"gemserve/config"
-	logging "git.antanst.com/antanst/logging"
+	"gemserve/gemini"
+	"git.antanst.com/antanst/logging"
 	"git.antanst.com/antanst/xerrors"
 	"github.com/gabriel-vasile/mimetype"
 )
@@ -23,21 +24,25 @@ type ServerConfig interface {
 	RootPath() string
 }
 
-func checkRequestURL(url *common.URL) error {
-	if url.Protocol != "gemini" {
-		return xerrors.NewError(fmt.Errorf("invalid URL"), 53, "URL Protocol not Gemini, proxying refused", false)
+func checkRequestURL(url *gemini.URL) error {
+	if !utf8.ValidString(url.String()) {
+		return xerrors.NewError(fmt.Errorf("invalid URL"), gemini.StatusBadRequest, "Invalid URL", false)
 	}
 
-	_, portStr, err := net.SplitHostPort(config.CONFIG.Listen)
+	if url.Protocol != "gemini" {
+		return xerrors.NewError(fmt.Errorf("invalid URL"), gemini.StatusProxyRequestRefused, "URL Protocol not Gemini, proxying refused", false)
+	}
+
+	_, portStr, err := net.SplitHostPort(config.CONFIG.ListenAddr)
 	if err != nil {
-		return xerrors.NewError(fmt.Errorf("failed to parse listen address: %w", err), 50, "Server configuration error", false)
+		return xerrors.NewError(fmt.Errorf("failed to parse server listen address: %w", err), 0, "", true)
 	}
 	listenPort, err := strconv.Atoi(portStr)
 	if err != nil {
-		return xerrors.NewError(fmt.Errorf("failed to parse listen port: %w", err), 50, "Server configuration error", false)
+		return xerrors.NewError(fmt.Errorf("invalid server listen port: %w", err), 0, "", true)
 	}
 	if url.Port != listenPort {
-		return xerrors.NewError(fmt.Errorf("failed to parse URL: %w", err), 53, "invalid URL port, proxying refused", false)
+		return xerrors.NewError(fmt.Errorf("failed to parse URL: %w", err), gemini.StatusProxyRequestRefused, "invalid request port, proxying refused", false)
 	}
 	return nil
 }
@@ -45,9 +50,9 @@ func checkRequestURL(url *common.URL) error {
 func GenerateResponse(conn *tls.Conn, connId string, input string) ([]byte, error) {
 	trimmedInput := strings.TrimSpace(input)
 	// url will have a cleaned and normalized path after this
-	url, err := common.ParseURL(trimmedInput, "", true)
+	url, err := gemini.ParseURL(trimmedInput, "", true)
 	if err != nil {
-		return nil, xerrors.NewError(fmt.Errorf("failed to parse URL: %w", err), 59, "Invalid URL", false)
+		return nil, xerrors.NewError(fmt.Errorf("failed to parse URL: %w", err), gemini.StatusBadRequest, "Invalid URL", false)
 	}
 	logging.LogDebug("%s %s normalized URL path: %s", connId, conn.RemoteAddr(), url.Path)
 
@@ -59,16 +64,16 @@ func GenerateResponse(conn *tls.Conn, connId string, input string) ([]byte, erro
 	serverRootPath := config.CONFIG.RootPath
 	localPath, err := calculateLocalPath(url.Path, serverRootPath)
 	if err != nil {
-		return nil, xerrors.NewError(err, 59, "Invalid path", false)
+		return nil, xerrors.NewError(err, gemini.StatusBadRequest, "Invalid path", false)
 	}
 	logging.LogDebug("%s %s request file path: %s", connId, conn.RemoteAddr(), localPath)
 
 	// Get file/directory information
 	info, err := os.Stat(localPath)
 	if errors.Is(err, os.ErrNotExist) || errors.Is(err, os.ErrPermission) {
-		return []byte("51 not found\r\n"), nil
+		return nil, xerrors.NewError(fmt.Errorf("%s %s failed to access path: %w", connId, conn.RemoteAddr(), err), gemini.StatusNotFound, "Not found or access denied", false)
 	} else if err != nil {
-		return nil, xerrors.NewError(fmt.Errorf("%s %s failed to access path: %w", connId, conn.RemoteAddr(), err), 0, "Path access failed", false)
+		return nil, xerrors.NewError(fmt.Errorf("%s %s failed to access path: %w", connId, conn.RemoteAddr(), err), gemini.StatusNotFound, "Path access failed", false)
 	}
 
 	// Handle directory.
@@ -78,12 +83,12 @@ func GenerateResponse(conn *tls.Conn, connId string, input string) ([]byte, erro
 	return generateResponseFile(conn, connId, url, localPath)
 }
 
-func generateResponseFile(conn *tls.Conn, connId string, url *common.URL, localPath string) ([]byte, error) {
+func generateResponseFile(conn *tls.Conn, connId string, url *gemini.URL, localPath string) ([]byte, error) {
 	data, err := os.ReadFile(localPath)
 	if errors.Is(err, os.ErrNotExist) || errors.Is(err, os.ErrPermission) {
-		return []byte("51 not found\r\n"), nil
+		return nil, xerrors.NewError(fmt.Errorf("%s %s failed to access path: %w", connId, conn.RemoteAddr(), err), gemini.StatusNotFound, "Path access failed", false)
 	} else if err != nil {
-		return nil, xerrors.NewError(fmt.Errorf("%s %s failed to read file: %w", connId, conn.RemoteAddr(), err), 0, "File read failed", false)
+		return nil, xerrors.NewError(fmt.Errorf("%s %s failed to read file: %w", connId, conn.RemoteAddr(), err), gemini.StatusNotFound, "Path access failed", false)
 	}
 
 	var mimeType string
@@ -92,15 +97,15 @@ func generateResponseFile(conn *tls.Conn, connId string, url *common.URL, localP
 	} else {
 		mimeType = mimetype.Detect(data).String()
 	}
-	headerBytes := []byte(fmt.Sprintf("20 %s; lang=en\r\n", mimeType))
+	headerBytes := []byte(fmt.Sprintf("%d %s; lang=en\r\n", gemini.StatusSuccess, mimeType))
 	response := append(headerBytes, data...)
 	return response, nil
 }
 
-func generateResponseDir(conn *tls.Conn, connId string, url *common.URL, localPath string) (output []byte, err error) {
+func generateResponseDir(conn *tls.Conn, connId string, url *gemini.URL, localPath string) (output []byte, err error) {
 	entries, err := os.ReadDir(localPath)
 	if err != nil {
-		return nil, xerrors.NewError(fmt.Errorf("%s %s failed to read directory: %w", connId, conn.RemoteAddr(), err), 0, "Directory read failed", false)
+		return nil, xerrors.NewError(fmt.Errorf("%s %s failed to read directory: %w", connId, conn.RemoteAddr(), err), gemini.StatusNotFound, "Directory access failed", false)
 	}
 
 	if config.CONFIG.DirIndexingEnabled {
@@ -115,7 +120,7 @@ func generateResponseDir(conn *tls.Conn, connId string, url *common.URL, localPa
 			}
 		}
 		data := []byte(strings.Join(contents, ""))
-		headerBytes := []byte("20 text/gemini; lang=en\r\n")
+		headerBytes := []byte(fmt.Sprintf("%d text/gemini; lang=en\r\n", gemini.StatusSuccess))
 		response := append(headerBytes, data...)
 		return response, nil
 	} else {
@@ -128,7 +133,7 @@ func generateResponseDir(conn *tls.Conn, connId string, url *common.URL, localPa
 func calculateLocalPath(input string, basePath string) (string, error) {
 	// Check for invalid characters early
 	if strings.ContainsAny(input, "\\") {
-		return "", xerrors.NewError(fmt.Errorf("invalid characters in path: %s", input), 0, "Invalid path characters", false)
+		return "", xerrors.NewError(fmt.Errorf("invalid characters in path: %s", input), gemini.StatusBadRequest, "Invalid path", false)
 	}
 
 	// If IsLocal(path) returns true, then Join(base, path)
@@ -144,7 +149,7 @@ func calculateLocalPath(input string, basePath string) (string, error) {
 
 	localPath, err := filepath.Localize(filePath)
 	if err != nil || !filepath.IsLocal(localPath) {
-		return "", xerrors.NewError(fmt.Errorf("could not construct local path from %s: %s", input, err), 0, "Invalid local path", false)
+		return "", xerrors.NewError(fmt.Errorf("could not construct local path from %s: %s", input, err), gemini.StatusBadRequest, "Invalid path", false)
 	}
 
 	filePath = path.Join(basePath, localPath)