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2021-11-15 18:06 665

[原创]签到

2021-11-15 18:06
665

看雪ctf签到题

 

对name做一次crc32,然后使用strspn函数判断输入的格式里是不是只有数字,接着校验了code的长度,然后将code转成整数,和name的crc32校验值异或之后对结果进行crc32校验,要求校验值为0x13B88C77

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import zlib
 
if __name__ == '__main__':
    tmp = ""
    for a in '0123456789abcedf':
        for b in '0123456789abcedf':
            for c in '0123456789abcedf':
                for d in '0123456789abcedf':
                    for e in '0123456789abcedf':
                        for f in '0123456789abcedf':
                            for g in '0123456789abcedf':
                                for h in '0123456789abcedf':
                                    tmp += a
                                    tmp += b
                                    tmp += c
                                    tmp += d
                                    tmp += e
                                    tmp += f
                                    tmp += g
                                    tmp += h
                                    #print(tmp)
                                    tmpResult = zlib.crc32(tmp.encode('utf8'))
                                    if tmpResult == 0x13B88C77:
                                        print(tmp)
                                        exit(0)
                                    tmp = ''

最后再和0x5EE54F4C异或就是结果。

 

太慢了,换go写了个多线程的。

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package main
 
import (
    "fmt"
    "hash/crc32"
)
var strTable = "12345abcdef67890"
func Crack(table *crc32.Table,ch chan int) {
    for _, v1 := range strTable {
        for _, v2 := range strTable {
            for _, v3 := range strTable {
                for _, v4 := range strTable {
                    for _, v5 := range strTable {
                        for _, v6 := range strTable {
                            for _, v7 := range strTable {
                                for _, v8 := range strTable {
                                    tmp := string(v1) + string(v2) + string(v3) + string(v4) + string(v5) + string(v6) + string(v7) + string(v8)
                                    ret := crc32.Checksum([]byte(tmp), table)
                                    //fmt.Println(tmp)
 
                                    if ret == 0x13B88C77 {
                                        fmt.Println(tmp)
                                        ch <- 6
                                        return
                                    }
 
                                }
                            }
                        }
                    }
                }
            }
        }
    }
}
 
func main() {
    table := crc32.MakeTable(crc32.IEEE)
    ret := crc32.Checksum([]byte("KCTF"), table)
    fmt.Println(ret)
    ch := make(chan int)
    go Crack(table,ch)
    fmt.Println( <-ch)
 
}

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