mirror of
https://github.com/cheat/cheat.git
synced 2024-12-18 18:55:06 +01:00
269 lines
7.2 KiB
Go
269 lines
7.2 KiB
Go
// Copyright 2009 The Go Authors. All rights reserved.
|
|
// Use of this source code is governed by a BSD-style
|
|
// license that can be found in the LICENSE file.
|
|
|
|
// Originally from: https://github.com/go/blob/master/src/crypto/sha1/sha1block.go
|
|
// It has been modified to support collision detection.
|
|
|
|
package sha1cd
|
|
|
|
import (
|
|
"fmt"
|
|
"math/bits"
|
|
|
|
shared "github.com/pjbgf/sha1cd/internal"
|
|
"github.com/pjbgf/sha1cd/ubc"
|
|
)
|
|
|
|
// blockGeneric is a portable, pure Go version of the SHA-1 block step.
|
|
// It's used by sha1block_generic.go and tests.
|
|
func blockGeneric(dig *digest, p []byte) {
|
|
var w [16]uint32
|
|
|
|
// cs stores the pre-step compression state for only the steps required for the
|
|
// collision detection, which are 0, 58 and 65.
|
|
// Refer to ubc/const.go for more details.
|
|
cs := [shared.PreStepState][shared.WordBuffers]uint32{}
|
|
|
|
h0, h1, h2, h3, h4 := dig.h[0], dig.h[1], dig.h[2], dig.h[3], dig.h[4]
|
|
for len(p) >= shared.Chunk {
|
|
m1 := [shared.Rounds]uint32{}
|
|
hi := 1
|
|
|
|
// Collision attacks are thwarted by hashing a detected near-collision block 3 times.
|
|
// Think of it as extending SHA-1 from 80-steps to 240-steps for such blocks:
|
|
// The best collision attacks against SHA-1 have complexity about 2^60,
|
|
// thus for 240-steps an immediate lower-bound for the best cryptanalytic attacks would be 2^180.
|
|
// An attacker would be better off using a generic birthday search of complexity 2^80.
|
|
rehash:
|
|
a, b, c, d, e := h0, h1, h2, h3, h4
|
|
|
|
// Each of the four 20-iteration rounds
|
|
// differs only in the computation of f and
|
|
// the choice of K (K0, K1, etc).
|
|
i := 0
|
|
|
|
// Store pre-step compression state for the collision detection.
|
|
cs[0] = [shared.WordBuffers]uint32{a, b, c, d, e}
|
|
|
|
for ; i < 16; i++ {
|
|
// load step
|
|
j := i * 4
|
|
w[i] = uint32(p[j])<<24 | uint32(p[j+1])<<16 | uint32(p[j+2])<<8 | uint32(p[j+3])
|
|
|
|
f := b&c | (^b)&d
|
|
t := bits.RotateLeft32(a, 5) + f + e + w[i&0xf] + shared.K0
|
|
a, b, c, d, e = t, a, bits.RotateLeft32(b, 30), c, d
|
|
|
|
// Store compression state for the collision detection.
|
|
m1[i] = w[i&0xf]
|
|
}
|
|
for ; i < 20; i++ {
|
|
tmp := w[(i-3)&0xf] ^ w[(i-8)&0xf] ^ w[(i-14)&0xf] ^ w[(i)&0xf]
|
|
w[i&0xf] = tmp<<1 | tmp>>(32-1)
|
|
|
|
f := b&c | (^b)&d
|
|
t := bits.RotateLeft32(a, 5) + f + e + w[i&0xf] + shared.K0
|
|
a, b, c, d, e = t, a, bits.RotateLeft32(b, 30), c, d
|
|
|
|
// Store compression state for the collision detection.
|
|
m1[i] = w[i&0xf]
|
|
}
|
|
for ; i < 40; i++ {
|
|
tmp := w[(i-3)&0xf] ^ w[(i-8)&0xf] ^ w[(i-14)&0xf] ^ w[(i)&0xf]
|
|
w[i&0xf] = tmp<<1 | tmp>>(32-1)
|
|
|
|
f := b ^ c ^ d
|
|
t := bits.RotateLeft32(a, 5) + f + e + w[i&0xf] + shared.K1
|
|
a, b, c, d, e = t, a, bits.RotateLeft32(b, 30), c, d
|
|
|
|
// Store compression state for the collision detection.
|
|
m1[i] = w[i&0xf]
|
|
}
|
|
for ; i < 60; i++ {
|
|
if i == 58 {
|
|
// Store pre-step compression state for the collision detection.
|
|
cs[1] = [shared.WordBuffers]uint32{a, b, c, d, e}
|
|
}
|
|
|
|
tmp := w[(i-3)&0xf] ^ w[(i-8)&0xf] ^ w[(i-14)&0xf] ^ w[(i)&0xf]
|
|
w[i&0xf] = tmp<<1 | tmp>>(32-1)
|
|
|
|
f := ((b | c) & d) | (b & c)
|
|
t := bits.RotateLeft32(a, 5) + f + e + w[i&0xf] + shared.K2
|
|
a, b, c, d, e = t, a, bits.RotateLeft32(b, 30), c, d
|
|
|
|
// Store compression state for the collision detection.
|
|
m1[i] = w[i&0xf]
|
|
}
|
|
for ; i < 80; i++ {
|
|
if i == 65 {
|
|
// Store pre-step compression state for the collision detection.
|
|
cs[2] = [shared.WordBuffers]uint32{a, b, c, d, e}
|
|
}
|
|
|
|
tmp := w[(i-3)&0xf] ^ w[(i-8)&0xf] ^ w[(i-14)&0xf] ^ w[(i)&0xf]
|
|
w[i&0xf] = tmp<<1 | tmp>>(32-1)
|
|
|
|
f := b ^ c ^ d
|
|
t := bits.RotateLeft32(a, 5) + f + e + w[i&0xf] + shared.K3
|
|
a, b, c, d, e = t, a, bits.RotateLeft32(b, 30), c, d
|
|
|
|
// Store compression state for the collision detection.
|
|
m1[i] = w[i&0xf]
|
|
}
|
|
|
|
h0 += a
|
|
h1 += b
|
|
h2 += c
|
|
h3 += d
|
|
h4 += e
|
|
|
|
if hi == 2 {
|
|
hi++
|
|
goto rehash
|
|
}
|
|
|
|
if hi == 1 {
|
|
col := checkCollision(m1, cs, [shared.WordBuffers]uint32{h0, h1, h2, h3, h4})
|
|
if col {
|
|
dig.col = true
|
|
hi++
|
|
goto rehash
|
|
}
|
|
}
|
|
|
|
p = p[shared.Chunk:]
|
|
}
|
|
|
|
dig.h[0], dig.h[1], dig.h[2], dig.h[3], dig.h[4] = h0, h1, h2, h3, h4
|
|
}
|
|
|
|
func checkCollision(
|
|
m1 [shared.Rounds]uint32,
|
|
cs [shared.PreStepState][shared.WordBuffers]uint32,
|
|
state [shared.WordBuffers]uint32) bool {
|
|
|
|
if mask := ubc.CalculateDvMask(m1); mask != 0 {
|
|
dvs := ubc.SHA1_dvs()
|
|
|
|
for i := 0; dvs[i].DvType != 0; i++ {
|
|
if (mask & ((uint32)(1) << uint32(dvs[i].MaskB))) != 0 {
|
|
var csState [shared.WordBuffers]uint32
|
|
switch dvs[i].TestT {
|
|
case 58:
|
|
csState = cs[1]
|
|
case 65:
|
|
csState = cs[2]
|
|
case 0:
|
|
csState = cs[0]
|
|
default:
|
|
panic(fmt.Sprintf("dvs data is trying to use a testT that isn't available: %d", dvs[i].TestT))
|
|
}
|
|
|
|
col := hasCollided(
|
|
dvs[i].TestT, // testT is the step number
|
|
// m2 is a secondary message created XORing with
|
|
// ubc's DM prior to the SHA recompression step.
|
|
m1, dvs[i].Dm,
|
|
csState,
|
|
state)
|
|
|
|
if col {
|
|
return true
|
|
}
|
|
}
|
|
}
|
|
}
|
|
return false
|
|
}
|
|
|
|
func hasCollided(step uint32, m1, dm [shared.Rounds]uint32,
|
|
state [shared.WordBuffers]uint32, h [shared.WordBuffers]uint32) bool {
|
|
// Intermediary Hash Value.
|
|
ihv := [shared.WordBuffers]uint32{}
|
|
|
|
a, b, c, d, e := state[0], state[1], state[2], state[3], state[4]
|
|
|
|
// Walk backwards from current step to undo previous compression.
|
|
// The existing collision detection does not have dvs higher than 65,
|
|
// start value of i accordingly.
|
|
for i := uint32(64); i >= 60; i-- {
|
|
a, b, c, d, e = b, c, d, e, a
|
|
if step > i {
|
|
b = bits.RotateLeft32(b, -30)
|
|
f := b ^ c ^ d
|
|
e -= bits.RotateLeft32(a, 5) + f + shared.K3 + (m1[i] ^ dm[i]) // m2 = m1 ^ dm.
|
|
}
|
|
}
|
|
for i := uint32(59); i >= 40; i-- {
|
|
a, b, c, d, e = b, c, d, e, a
|
|
if step > i {
|
|
b = bits.RotateLeft32(b, -30)
|
|
f := ((b | c) & d) | (b & c)
|
|
e -= bits.RotateLeft32(a, 5) + f + shared.K2 + (m1[i] ^ dm[i])
|
|
}
|
|
}
|
|
for i := uint32(39); i >= 20; i-- {
|
|
a, b, c, d, e = b, c, d, e, a
|
|
if step > i {
|
|
b = bits.RotateLeft32(b, -30)
|
|
f := b ^ c ^ d
|
|
e -= bits.RotateLeft32(a, 5) + f + shared.K1 + (m1[i] ^ dm[i])
|
|
}
|
|
}
|
|
for i := uint32(20); i > 0; i-- {
|
|
j := i - 1
|
|
a, b, c, d, e = b, c, d, e, a
|
|
if step > j {
|
|
b = bits.RotateLeft32(b, -30) // undo the rotate left
|
|
f := b&c | (^b)&d
|
|
// subtract from e
|
|
e -= bits.RotateLeft32(a, 5) + f + shared.K0 + (m1[j] ^ dm[j])
|
|
}
|
|
}
|
|
|
|
ihv[0] = a
|
|
ihv[1] = b
|
|
ihv[2] = c
|
|
ihv[3] = d
|
|
ihv[4] = e
|
|
a = state[0]
|
|
b = state[1]
|
|
c = state[2]
|
|
d = state[3]
|
|
e = state[4]
|
|
|
|
// Recompress blocks based on the current step.
|
|
// The existing collision detection does not have dvs below 58, so they have been removed
|
|
// from the source code. If new dvs are added which target rounds below 40, that logic
|
|
// will need to be readded here.
|
|
for i := uint32(40); i < 60; i++ {
|
|
if step <= i {
|
|
f := ((b | c) & d) | (b & c)
|
|
t := bits.RotateLeft32(a, 5) + f + e + shared.K2 + (m1[i] ^ dm[i])
|
|
a, b, c, d, e = t, a, bits.RotateLeft32(b, 30), c, d
|
|
}
|
|
}
|
|
for i := uint32(60); i < 80; i++ {
|
|
if step <= i {
|
|
f := b ^ c ^ d
|
|
t := bits.RotateLeft32(a, 5) + f + e + shared.K3 + (m1[i] ^ dm[i])
|
|
a, b, c, d, e = t, a, bits.RotateLeft32(b, 30), c, d
|
|
}
|
|
}
|
|
|
|
ihv[0] += a
|
|
ihv[1] += b
|
|
ihv[2] += c
|
|
ihv[3] += d
|
|
ihv[4] += e
|
|
|
|
if ((ihv[0] ^ h[0]) | (ihv[1] ^ h[1]) |
|
|
(ihv[2] ^ h[2]) | (ihv[3] ^ h[3]) | (ihv[4] ^ h[4])) == 0 {
|
|
return true
|
|
}
|
|
|
|
return false
|
|
}
|