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