package main
import (
"bytes"
"fmt"
"io"
"os"
"text/template"
"time"
)
var errPageRawTmpl = `
COW Proxy
{{.H1}}
{{.Msg}}
{{.Form}}
Generated by COW at {{.T}}
`
var blockedFormRawTmpl = `
Refresh to retry or add {{.Domain}} to
`
var directFormRawTmpl = `
`
// Do not end with "\r\n" so we can add more header later
var headRawTmpl = "HTTP/1.1 {{.CodeReason}}\r\n" +
"Connection: keep-alive\r\n" +
"Cache-Control: no-cache\r\n" +
"Pragma: no-cache\r\n" +
"Content-Type: text/html\r\n" +
"Content-Length: {{.Length}}\r\n"
var errPageTmpl, headTmpl, blockedFormTmpl, directFormTmpl *template.Template
func init() {
var err error
if headTmpl, err = template.New("errorHead").Parse(headRawTmpl); err != nil {
fmt.Println("Internal error on generating error head template")
os.Exit(1)
}
if errPageTmpl, err = template.New("errorPage").Parse(errPageRawTmpl); err != nil {
fmt.Println("Internal error on generating error page template")
os.Exit(1)
}
if blockedFormTmpl, err = template.New("blockedForm").Parse(blockedFormRawTmpl); err != nil {
fmt.Println("Internal error on generating blocked form template")
os.Exit(1)
}
if directFormTmpl, err = template.New("directForm").Parse(directFormRawTmpl); err != nil {
fmt.Println("Internal error on generating direct form template")
os.Exit(1)
}
}
func genErrorPage(h1, msg, form string) (string, error) {
var err error
data := struct {
H1 string
Msg string
Form string
T string
}{
h1,
msg,
form,
time.Now().Format(time.ANSIC),
}
buf := new(bytes.Buffer)
err = errPageTmpl.Execute(buf, data)
return buf.String(), err
}
func sendPageGeneric(w io.Writer, codeReason, h1, msg, form, addHeader string) {
page, err := genErrorPage(h1, msg, form)
if err != nil {
errl.Println("Error generating error page:", err)
return
}
data := struct {
CodeReason string
Length int
}{
codeReason,
len(page),
}
buf := new(bytes.Buffer)
if err := headTmpl.Execute(buf, data); err != nil {
errl.Println("Error generating error page header:", err)
return
}
buf.WriteString(addHeader)
buf.WriteString("\r\n")
buf.WriteString(page)
w.Write(buf.Bytes())
}
func sendErrorPage(w io.Writer, codeReason, h1, msg string) {
sendPageGeneric(w, codeReason, "[Error] "+h1, msg, "", "")
}
func sendRedirectPage(w io.Writer, location string) {
sendPageGeneric(w, "302 Found", "Domain added to blocked list", "Redirect to "+location,
"", fmt.Sprintf("Location: %s\r\n", location))
}
func sendBlockedErrorPage(c *clientConn, codeReason, h1, msg string, r *Request) {
// If host is IP or in always DS, we can't add it to blocked or direct domain list. Just
// return ordinary error page.
h, _ := splitHostPort(r.URL.HostPort)
if hostIsIP(r.URL.HostPort) || domainSet.isHostInAlwaysDs(h) {
sendErrorPage(c, codeReason, h1, msg)
return
}
data := struct {
ProxyAddr string
Host string
Domain string
}{
c.proxy.addr,
h,
host2Domain(r.URL.HostPort),
}
buf := new(bytes.Buffer)
if err := blockedFormTmpl.Execute(buf, data); err != nil {
errl.Println("Error generating blocked form:", err)
return
}
if !domainSet.isHostDirect(h) {
if err := directFormTmpl.Execute(buf, data); err != nil {
errl.Println("Error generating direct form:", err)
return
}
}
sendPageGeneric(c, codeReason, "[Error] "+h1, msg, buf.String(), "")
}