Commit: 684cc056787857ec61d9abebeaabdba776b4f6d4
Author: Vi Grey
Date: 2023-11-20 15:03 UTC
Summary: Initial commit

 README.txt                |  25 ++++++++++
 go.mod                    |   3 ++
 gopher-server.go          | 199 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 index.gph                 |   6 +++
 index.gph-example         |  20 ++++++++
 polyglot-instructions.txt |  38 +++++++++++++++
 6 files changed, 291 insertions(+)


diff --git a/README.txt b/README.txt
new file mode 100644
index 0000000..6e8dcdc
--- /dev/null
+++ b/README.txt
@@ -0,0 +1,25 @@
+Gopher Server
+--------------
+
+A gopher server for an executable+ZIP polyglot file that hosts the
+content in the ZIP file portion of the polyglot file.
+
+Instructions to produce the polyglot file are included in the file
+`polyglot-instructions.txt`.
+
+An `index.gph` file is included.  It is incredibly important that the
+tabs and the first character of each line be correct, as gophermap
+files are quite picky.  An example index gophermap file is included at
+`index.gph-example`, which is a gophermap for the tmp.0ut zine for
+Volume 1.
+
+The gopher server is expecting an index.gph file at the root of the
+ZIP file.
+
+Upon running the server, the Gopherhole will be listening at TCP
+"localhost:2311" unless specified using the --host and/or --port flag
+arguments.  For more details, you can run the server with -h or --help.
+
+Port 2311 was chosen for the 2023-11 release of tmp.0ut Volume 3 and
+because it's an unprivileged port, unlike port 70, which is used by
+default for Gopherholes.
diff --git a/go.mod b/go.mod
new file mode 100644
index 0000000..f1dd109
--- /dev/null
+++ b/go.mod
@@ -0,0 +1,3 @@
+module gopher-server
+
+go 1.15
diff --git a/gopher-server.go b/gopher-server.go
new file mode 100644
index 0000000..45a6ee4
--- /dev/null
+++ b/gopher-server.go
@@ -0,0 +1,199 @@
+/*
+ +------------------------+
+ |     Gopher Server      |
+ | Programmed by Vi Grey  |
+ +------------------------+
+
+ This is meant to be compiled and prepended to a ZIP file to make it an
+ Executable+ZIP polyglot file with the intention of the ZIP file
+ hosting the content for the Gopherhole.  Please make sure an
+ "index.gph" gophermap file is included in the root of the ZIP file.
+ If run without any arguments, the ZIP file will be the executable
+ itself, and the Gopherhole will be listening on localhost:2311 (2311
+ chosen because 2023-11 for the release of tmp.0ut Volume 3)
+
+ Do whatever the heck you want to with this code, just don't blame me
+ if anything happens...
+
+ GO GOLDEN GOPHERS!
+*/
+
+package main
+
+import (
+	"archive/zip"
+	"fmt"
+	"io"
+	"log"
+	"net"
+	"os"
+	"path/filepath"
+	"strconv"
+	"strings"
+	"time"
+)
+
+var (
+	port        = 2311
+	host        = "localhost"
+	zipFilePath string
+	zipReader   *zip.ReadCloser
+)
+
+// Print error log and close program with error code 1 if err not nil
+func handleErr(err error) {
+	if err != nil {
+		log.Fatalf("%s\nExiting...\n", err)
+	}
+}
+
+// Open ZIP file and get Reader
+func getZIPFileReader() {
+	var err error
+	zipReader, err = zip.OpenReader(zipFilePath)
+	handleErr(err)
+}
+
+// Get request from gopher client and serve page from ZIP file if path
+// exists inside of ZIP file
+func handleGopherConnection(conn net.Conn) {
+	var rBuf []byte
+	var request string
+	// Continue reading from connection until first \r\n is found
+	for {
+		rBuf = make([]byte, 2048)
+		n, err := conn.Read(rBuf)
+		if err != nil || n == 0 {
+			break
+		}
+		request += string(rBuf[:n])
+		// Gopher path request ends at first instance of \r\n
+		nlIndex := strings.Index(request, "\r\n")
+		if nlIndex > -1 {
+			reqPath := request[:nlIndex] // Gopher path request
+			if reqPath == "" || reqPath == "/" {
+				// Set path to index.gph if request is root path
+				reqPath = "index.gph"
+			}
+			for _, zipFile := range zipReader.File {
+				if filepath.Join("/", reqPath) == filepath.Join("/", zipFile.Name) {
+					// /reqPath is in zip directory root
+					f, err := zipFile.Open()
+					handleErr(err)
+					defer f.Close()
+					// Write file content from zip file to connection
+					io.Copy(conn, f)
+					conn.Write([]byte("\r\n.\r\n"))
+					return
+				}
+			}
+			// Send error to gopher client.  Essentially the same as HTTP 404
+			conn.Write([]byte("3The selected resource does not exist\t\t" +
+				"fake\tfake\t0\r\n.\r\n"))
+			return
+		}
+	}
+	// Send error to gopher client.  Essentially the same as HTTP 400
+	conn.Write([]byte("3Invalid Request\t\tfake\tfake\t0\r\n.\r\n"))
+}
+
+// Start the gopher server at specified host and port (default
+// localhost:2311)
+func startGopherServer() {
+	listener, err := net.Listen("tcp",
+		fmt.Sprintf("%s:%d", host, port))
+	handleErr(err)
+	for {
+		if conn, err := listener.Accept(); err == nil {
+			go func() {
+				defer conn.Close()
+				// Close connection when request handled or after 30 seconds
+				conn.SetReadDeadline(time.Now().Add(30 * time.Second))
+				handleGopherConnection(conn)
+			}()
+		}
+	}
+}
+
+// Display help message and close program
+func displayHelp() {
+	fmt.Printf(`Usage %s [OPTIONS]...
+
+Options:
+  -h, --help              Print Help (this message) and exit
+      --host <name>       TCP address for gopher server to listen on
+                          (default: "localhost")
+      --port <num>        TCP port to listen on (default: 2311)
+      --zip <path>        Path to ZIP file that hosts the content
+                          (default: this executable file itself)
+`, os.Args[0])
+}
+
+// Get a string value from args[x+1]
+func getFlagStrValue(args []string, x, argsLen int) (string, error) {
+	if x+1 >= argsLen {
+		err := fmt.Errorf("%s: flag `%s` missing value\n Use `%s --help` for "+
+			"details", os.Args[0], args[x], os.Args[0])
+		return "", err
+	}
+	return args[x+1], nil
+}
+
+// Get an integer value of 1-65535 from args[x+1]
+func getFlagPortValue(args []string, x, argsLen int) (int, error) {
+	strVal, err := getFlagStrValue(args, x, argsLen)
+	if err != nil {
+		return 0, err
+	}
+	portVal, _ := strconv.Atoi(strVal)
+	if portVal < 1 || portVal > 65535 {
+		err = fmt.Errorf("%s: flag `%s` value must be a number value of "+
+			"1-65535\nUse `%s --help` for details",
+			os.Args[0], args[x], os.Args[0])
+		return 0, err
+	}
+	return portVal, nil
+}
+
+func init() {
+	var err error
+	// Get executable path in case --zip flag not used
+	zipFilePath, err = os.Executable()
+	handleErr(err)
+	args := os.Args[1:]
+	argsLen := len(args)
+	// Flag checking (--host, -h, --help, --port, and --zip)
+	for x := 0; x < argsLen; x++ {
+		switch strings.ToLower(args[x]) {
+		case "-h", "--help":
+			displayHelp()
+			os.Exit(0)
+		case "--host":
+			// User specified TCP listening address
+			hostVal, err := getFlagStrValue(args, x, argsLen)
+			x++
+			handleErr(err)
+			host = hostVal
+		case "--port":
+			// User specified TCP listening port
+			portVal, err := getFlagPortValue(args, x, argsLen)
+			x++
+			handleErr(err)
+			port = portVal
+		case "--zip":
+			// User specified ZIP file path
+			zipFilePathVal, err := getFlagStrValue(args, x, argsLen)
+			x++
+			handleErr(err)
+			zipFilePath = zipFilePathVal
+		}
+	}
+}
+
+func main() {
+	getZIPFileReader()
+	defer zipReader.Close()
+	fmt.Printf("Starting Gopherhole at gopher://%s:%d\n",
+		host, port)
+	startGopherServer()
+}
diff --git a/index.gph b/index.gph
new file mode 100644
index 0000000..44987f2
--- /dev/null
+++ b/index.gph
@@ -0,0 +1,6 @@
+itmp.0ut Volume 3 - November 2023		fake	0
+i		fake	0
+03.0 Intro (tmp.0ut Staff)	/txt/0.txt	localhost	2311
+03.X Title (Author)	/txt/path.txt	localhost	2311
+03.X Title (Author)	/txt/path.txt	localhost	2311
+03.X Title (Author)	/txt/path.txt	localhost	2311
diff --git a/index.gph-example b/index.gph-example
new file mode 100644
index 0000000..ff92070
--- /dev/null
+++ b/index.gph-example
@@ -0,0 +1,20 @@
+itmp.0ut Volume 1 - April 2021		fake	0
+i		fake	0
+01.0 Intro (tmp.0ut Staff)	/txt/0.txt	localhost	2311
+01.1 Dead Bytes (xcellerator)	/txt/1.txt	localhost	2311
+01.2 Implementing the PT_NOTE Infection Method In x64 Assembly (sblip)	/txt/2.txt	localhost	2311
+01.3 PT_NOTE To PT_LOAD ELF Injector In Rust (d3npa)	/txt/3.txt	localhost	2311
+01.4 PT_NOTE Disinfector In Python (manizzle)	/txt/4.txt	localhost	2311
+01.5 Fuzzing Radare2 For 0days In About 30 Lines Of Code (Architect, s01den)	/txt/5.txt	localhost	2311
+01.6 The Polymorphic False-Disassembly Technique (s01den)	/txt/6.txt	localhost	2311
+01.7 Lin64.Eng3ls: Some Anti-RE Techniques In A Linux Virus (s01den, sblip)	/txt/7.txt	localhost	2311
+01.8 Linux.Midrashim.asm (TMZ)	/txt/Linux.Midrashim.asm	localhost	2311
+01.9 In-Memory LKM Loading (netspooky)	/txt/9.txt	localhost	2311
+01.10 Linux SHELF Loading (ulexec, Anonymous_)	/txt/10.txt	localhost	2311
+01.11 Return To Original Entry Point Despite PIE (s01den)	/txt/11.txt	localhost	2311
+01.12 Writing Viruses In MIPS Assembly For Fun (And No Profit) (s01den)	/txt/12.txt	localhost	2311
+01.13 Interview: herm1t (tmp.0ut Staff)	/txt/13.txt	localhost	2311
+01.14 GONE IN 360 SECONDS - Linux/Retaliation (qkumba)	/txt/14.txt	localhost	2311
+01.15 Linux.Nasty.asm (TMZ)	/txt/Linux.Nasty.asm	localhost	2311
+01.16 Linux.Precinct3.asm (netspooky)	/txt/Linux.Precinct3.asm	localhost	2311
+01.17 Underground Worlds (s01den)	/txt/17.txt	localhost	2311
diff --git a/polyglot-instructions.txt b/polyglot-instructions.txt
new file mode 100644
index 0000000..c618125
--- /dev/null
+++ b/polyglot-instructions.txt
@@ -0,0 +1,38 @@
+Dependencies:
+
+* go >= 1.15
+* zip
+
+
+1.) Compile go program:
+
+```
+go build
+```
+
+if you want to make the resulting binary file smaller, you can compile with:
+
+```
+go build -ldflags="-s -w"
+```
+
+2.) Concatenate the compiled program and ZIP file:
+
+```
+cat gopher-server zip-file.zip > cat.zip
+```
+
+3.) Fix ZIP file offsets:
+
+```
+zip -F cat.zip --out out.zip
+```
+
+4.) Make polyglot file executable if you want to run the file:
+
+```
+chmod +x out.zip
+```
+
+If you want to use --port or --host flags, please make sure index.gph
+file at root of ZIP file has the matching port and host information.