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| package main
import (
"fmt"
"io/ioutil"
"log"
"net/http"
"net/url"
"strings"
)
var (
secret = "xiaomo.wabzsy"
banner = "Golang HTTP Server (v2.3.3)"
template = `<!DOCTYPE html>
<html>
<head>
<title>San Check</title>
</head>
<body>
<form method="POST">
<input type="text" name="url" />
<input type="submit" value="淦!" />
</form>
<pre>
%s
</pre>
</body>
<!-- ./sancheck.php -->
</html>`
)
func SanCheck(input string) error {
u, err := url.Parse(input)
if err != nil {
return err
}
if u.Scheme != "http" {
return fmt.Errorf("err: Invalid Scheme [%s]", u.Scheme)
}
if u.Opaque != "" {
return fmt.Errorf("err: WHAT AER YOU DOING ?!!! (%s)", u.Opaque)
}
if u.Hostname() != "127.0.0.1" {
return fmt.Errorf("err: Invalid Hostname [%s]", u.Hostname())
}
if u.Port() != "" && u.Port() != "80" {
return fmt.Errorf("err: Invalid Port [%s]", u.Port())
}
if u.User == nil {
return fmt.Errorf("err: Authorization Required")
}
if u.User.Username() != "root" {
return fmt.Errorf("err: Invalid Username [%s]", u.User.Username())
}
if password, set := u.User.Password(); !set || password != "P@ssw0rd!" {
return fmt.Errorf("err: Invalid Password [%s]", password)
}
if u.RequestURI() != "/flag.php" {
return fmt.Errorf("err: Invalid RequestURI [%s]", u.RequestURI())
}
if u.Fragment != "" {
return fmt.Errorf("err: Invalid Fragment [%s]", u.Fragment)
}
if !strings.Contains(u.String(), "'Pwned!'") {
return fmt.Errorf("err: San Check failed")
}
return nil
}
func DefaultHandler(w http.ResponseWriter, req *http.Request) {
input := req.PostFormValue("url")
if input == "" {
Response(w, template, "Where is the flag?")
return
}
if err := SanCheck(input); err == nil {
req, _ := http.NewRequest("GET", input, nil)
req.Header.Add("Secret", secret)
if resp, err := (&http.Client{}).Do(req); err == nil {
if body, err := ioutil.ReadAll(resp.Body); err == nil {
Response(w, template, string(body))
}
_ = resp.Body.Close()
} else {
Response(w, template, err.Error())
}
} else {
Response(w, template, err.Error())
}
}
func FlagHandler(w http.ResponseWriter, req *http.Request) {
if strings.Join(req.Header["Secret"], "") != secret {
Forbidden(w)
} else if !strings.HasPrefix(req.RemoteAddr, "127.0.0.1") {
Forbidden(w)
} else {
Response(w, "<h1>%s</h1>", readFlag())
}
}
func readFlag() string {
if bs, err := ioutil.ReadFile("./flag.txt"); err == nil {
return string(bs)
} else {
return fmt.Sprintf("Unable to read flag.txt, please contact technical support.(%s)", err.Error())
}
}
func CodeHandler(w http.ResponseWriter, _ *http.Request) {
w.Header().Set("Content-Type", "text/plain; charset=utf-8")
w.Header().Set("Server", banner)
if bs, err := ioutil.ReadFile("main.go"); err == nil {
_, _ = w.Write(bs)
} else {
_, _ = w.Write(
[]byte(
fmt.Sprintf("Unable to read main.go, please contact technical support.(%s)",
err.Error(),
),
),
)
}
}
func Forbidden(w http.ResponseWriter) {
w.WriteHeader(403)
Response(w, "<h1>%s</h1>", "403 Forbidden")
}
func Response(w http.ResponseWriter, tpl string, response string) {
w.Header().Set("Content-Type", "text/html; charset=utf-8")
w.Header().Set("Server", banner)
if _, err := fmt.Fprintf(w, tpl, response); err != nil {
log.Println(err)
}
}
func main() {
http.HandleFunc("/", DefaultHandler)
http.HandleFunc("/flag.php", FlagHandler)
http.HandleFunc("/sancheck.php", CodeHandler)
log.Fatal(http.ListenAndServe(":80", nil))
}
|