Tags: golang misc
Rating:
# Defenit: QR Generator
When you first connect to the server, it asks you for a name, and then starts spitting out ones and zeros in a grid format, and gives you a prompt >> but times out pretty quickly. I decided to take a chance and assume they wanted the QR code output. Here’s what the service spit out, after the name prompt and some comments about levels:
```
< QR >
1 1 1 1 1 1 1 0 1 0 1 0 1 0 0 0 0 1 0 0 1 0 1 1 1 1 1 1 1
1 0 0 0 0 0 1 0 1 0 0 1 1 0 0 0 1 0 0 0 1 0 1 0 0 0 0 0 1
1 0 1 1 1 0 1 0 0 1 1 1 1 1 0 1 0 0 0 1 0 0 1 0 1 1 1 0 1
1 0 1 1 1 0 1 0 0 0 1 1 1 0 1 0 0 0 0 1 1 0 1 0 1 1 1 0 1
1 0 1 1 1 0 1 0 1 0 0 0 0 1 0 0 0 1 1 1 0 0 1 0 1 1 1 0 1
1 0 0 0 0 0 1 0 1 0 0 1 0 1 0 1 0 0 0 0 0 0 1 0 0 0 0 0 1
1 1 1 1 1 1 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 1 1 1 1 1 1
0 0 0 0 0 0 0 0 0 0 1 0 1 1 0 1 1 0 1 0 0 0 0 0 0 0 0 0 0
1 1 1 1 0 1 1 0 0 0 0 1 1 1 0 1 1 0 1 0 0 1 0 1 1 0 0 1 1
1 1 0 1 0 0 0 1 0 1 0 0 0 1 1 0 1 1 0 0 1 1 0 1 1 1 0 0 0
1 1 1 0 0 0 1 0 0 1 0 1 1 0 1 0 1 0 1 1 0 0 1 0 0 1 1 0 0
0 0 1 1 0 1 0 0 1 0 1 1 0 0 0 0 1 0 1 1 0 0 0 0 1 0 1 1 0
1 0 0 0 0 1 1 1 0 1 1 0 1 0 0 1 0 1 1 0 1 0 0 1 0 1 1 0 1
0 0 0 1 1 1 0 0 1 0 1 1 1 1 0 0 1 0 1 1 1 1 0 0 1 0 1 1 1
1 1 1 0 0 1 1 0 1 1 1 0 0 1 0 1 1 0 1 0 0 1 0 1 1 0 1 0 0
1 0 1 1 1 0 0 0 1 0 1 0 0 1 1 1 0 0 1 0 1 1 1 0 0 0 1 0 1
1 0 1 0 0 0 1 1 1 1 0 1 1 1 0 1 1 1 1 0 0 1 0 1 0 1 0 1 0
0 0 1 1 0 0 0 1 0 1 1 1 1 0 0 1 0 1 0 1 1 1 1 1 1 0 0 1 0
0 0 1 1 0 0 1 0 0 1 1 0 1 0 1 0 0 1 0 0 0 0 0 1 0 0 1 1 0
0 1 0 0 0 1 0 1 1 1 0 1 1 0 0 1 1 1 0 1 1 0 1 1 1 0 0 1 0
1 1 1 1 0 0 1 0 1 0 0 1 0 1 0 1 0 0 1 1 1 1 1 1 1 1 1 1 1
0 0 0 0 0 0 0 0 0 1 0 1 1 1 1 0 1 0 1 0 1 0 0 0 1 1 1 1 1
1 1 1 1 1 1 1 0 0 0 1 0 0 0 1 1 0 1 0 1 1 0 1 0 1 0 1 1 0
1 0 0 0 0 0 1 0 1 1 1 1 0 1 1 1 1 1 0 0 1 0 0 0 1 0 0 1 1
1 0 1 1 1 0 1 0 0 1 1 1 0 1 0 0 0 1 1 0 1 1 1 1 1 1 0 0 1
1 0 1 1 1 0 1 0 1 1 0 1 1 1 1 1 0 1 1 0 0 1 1 1 1 0 0 1 0
1 0 1 1 1 0 1 0 1 1 1 0 1 0 1 0 0 1 1 0 0 0 0 0 0 0 0 0 0
1 0 0 0 0 0 1 0 1 1 0 1 0 1 1 0 0 1 0 0 0 1 0 1 1 0 1 1 1
1 1 1 1 1 1 1 0 1 1 1 1 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 1 0
>>
```
Eventually I realized it needed to handle varying sizes of QR codes and handle reading until the prompt.
Here is the my code:
```
package main
import (
"fmt"
"image"
"image/color"
"log"
"net"
"strings"
"github.com/makiuchi-d/gozxing"
"github.com/makiuchi-d/gozxing/qrcode"
)
func main() {
con, err := net.Dial("tcp", "qr-generator.ctf.defenit.kr:9000")
if err != nil {
panic(err)
}
defer con.Close()
qrmark := "< QR >"
buf := make([]byte, 1024*16)
nBytes, err := con.Read(buf)
nBytes, err = con.Read(buf)
nBytes, err = con.Write([]byte("E\n"))
codestr := ""
for {
nBytes, err = con.Read(buf)
codestr = codestr + string(buf[:nBytes])
fmt.Println(codestr)
if strings.Index(codestr, "Defenit{") >= 0 {
break
}
if strings.Index(codestr, qrmark) < 0 || strings.Index(codestr, ">>") < 0 {
continue
}
codestr = codestr[strings.Index(codestr, qrmark):]
lines := strings.Split(codestr, "\n")
width := len(strings.Split(lines[1], " "))
img := image.NewRGBA(image.Rectangle{image.Point{0, 0}, image.Point{width, width}})
fmt.Println("qr code width:", width)
for x, line := range lines[1:] {
arr := strings.Split(line, " ")
if len(arr) == width {
for y, val := range arr {
if val == "1" {
img.Set(x, y, color.Black)
}
}
} else {
break
}
}
bmp, _ := gozxing.NewBinaryBitmapFromImage(img)
qrReader := qrcode.NewQRCodeReader()
text, err := qrReader.Decode(bmp, nil)
if err != nil {
log.Fatal(err)
}
fmt.Println("qrcode value:", text)
con.Write([]byte(fmt.Sprintf("%s\n", text)))
codestr = ""
}
}
```
