peridot/vendor/github.com/pjbgf/sha1cd/sha1cdblock_generic.go
2024-10-16 12:56:53 +02:00

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
}