49 lines
1.2 KiB
Markdown
49 lines
1.2 KiB
Markdown
反向crackme?
|
||
|
||
一看是vb.net 内心狂喜
|
||
|
||
先来看一下serial是怎么生成的：
|
||
|
||
```c#
|
||
// TextBox1:Name, TextBox2:Serial
|
||
private void Button1_Click(object sender, EventArgs e)
|
||
{
|
||
if (this.TextBox1.Text.Length <= 7)
|
||
{
|
||
Interaction.MsgBox("Name must be at least 8 chars!!!", MsgBoxStyle.OkOnly, null);
|
||
}
|
||
else
|
||
{
|
||
this.lengthofbox = StringType.FromInteger(this.TextBox1.Text.Length);
|
||
this.TextBox2.Text = this.lengthofbox + this.TextBox1.Text.Remove(3, 5);
|
||
this.TextBox3.Text = this.TextBox2.Text;
|
||
this.string2 = StringType.FromDouble(DoubleType.FromString(this.lengthofbox) / (double)this.TextBox3.Text.Length);
|
||
this.TextBox2.Text = this.string2 + this.TextBox3.Text;
|
||
}
|
||
}
|
||
```
|
||
|
||
这样一来就能写出以下检查代码
|
||
|
||
```c#
|
||
static bool ValidateNameSerial(string name, string serial, ref string ErrReason)
|
||
{
|
||
int length = name.Length;
|
||
if (length <= 7)
|
||
{
|
||
ErrReason = "Name length must be greater than 7";
|
||
return false;
|
||
}
|
||
else
|
||
{
|
||
string temp2 = length + name.Remove(3, 5);
|
||
if ((length / (double)temp2.Length) + temp2 == serial)
|
||
return true;
|
||
ErrReason = "Wrong Serial";
|
||
return false;
|
||
|
||
}
|
||
}
|
||
```
|
||
|