Minor bug

[namaho]

But it causes runtime panic when indexing specific size domain name

`panic: runtime error: slice bounds out of range

goroutine 2026854 [running]:
github.com/shadowsocks/go-shadowsocks2/socks.ReadAddr(0x7f3db541df80, 0xc429c676e0, 0xc429c676e0, 0x7f3db541df80, 0xc429c676e0, 0x0, 0xc420021f30)`

[riobard]

Thanks for the PR! I do not fully understand the bug. Why does it happen and why does the change fix it?

[namaho]

b[1] is of type uint8, with a maximum value 255. When b[1] do calculation with numbers, the return value would be also an uint8. If the size of the domain name exceed 251, say 252 for example, then the result of 2+b[1]+2 would be truncated to 0, while what we expect is 256, thus we should cast b[1] to a larger type of value, then we are safe to do the calculation.

A snippet of code would be more clear.

package main

import (
	"fmt"
)

func main() {
	b := make([]byte, 4)
	b[0] = byte(250)
	b[1] = byte(251)
	b[2] = byte(252)
	b[3] = byte(253)
	
	k0 := 2 + b[0] + 2
	k1 := 2 + b[1] + 2
	k2 := 2 + b[2] + 2
	k3 := 2 + b[3] + 2
	
	fmt.Printf("%v\n", k0)
	fmt.Printf("%v\n", k1)
	fmt.Printf("%v\n", k2)
	fmt.Printf("%v\n", k3)
}

Output:

254
255
0
1

[riobard]

Ah I see! THAT is a tricky one! :D

One more question: wouldn't we need to change the line on 58,59,86 as well?

[riobard]

This should probably be b[:1+1+int(b[1])+2]?

[namaho]

Yes, that's the right way to parse the address.

[riobard]

Thanks a lot!