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feat(QMCv2): add rc4 cipher

(cherry picked from commit 6b5b4d3bf5f6285e908808d48dee4e2e4ae8c3a2)
20230320
MengYX 3 years ago
parent
commit
76c3887eec
No known key found for this signature in database GPG Key ID: E63F9C7303E8F604
  1. 75
      src/decrypt/qmc_cipher.test.ts
  2. 117
      src/decrypt/qmc_cipher.ts

75
src/decrypt/qmc_cipher.test.ts

@ -1,4 +1,4 @@
import {QmcMapCipher, QmcStaticCipher} from "@/decrypt/qmc_cipher";
import {QmcMapCipher, QmcRC4Cipher, QmcStaticCipher} from "@/decrypt/qmc_cipher";
import fs from 'fs'
test("static cipher [0x7ff8,0x8000) ", () => {
@ -27,17 +27,6 @@ test("static cipher [0,0x10) ", () => {
expect(buf).toStrictEqual(expected)
})
function loadTestDataMapCipher(name: string): {
key: Uint8Array,
cipherText: Uint8Array,
clearText: Uint8Array
} {
return {
key: fs.readFileSync(`testdata/${name}_key.bin`),
cipherText: fs.readFileSync(`testdata/${name}_raw.bin`),
clearText: fs.readFileSync(`testdata/${name}_target.bin`)
}
}
test("map cipher: get mask", () => {
const expected = new Uint8Array([
@ -53,10 +42,22 @@ test("map cipher: get mask", () => {
expect(buf).toStrictEqual(expected)
})
function loadTestDataCipher(name: string): {
key: Uint8Array,
cipherText: Uint8Array,
clearText: Uint8Array
} {
return {
key: fs.readFileSync(`testdata/${name}_key.bin`),
cipherText: fs.readFileSync(`testdata/${name}_raw.bin`),
clearText: fs.readFileSync(`testdata/${name}_target.bin`)
}
}
test("map cipher: real file", async () => {
const cases = ["mflac_map", "mgg_map"]
for (const name of cases) {
const {key, clearText, cipherText} = loadTestDataMapCipher(name)
const {key, clearText, cipherText} = loadTestDataCipher(name)
const c = new QmcMapCipher(key)
c.decrypt(cipherText, 0)
@ -64,3 +65,51 @@ test("map cipher: real file", async () => {
expect(cipherText).toStrictEqual(clearText)
}
})
test("rc4 cipher: real file", async () => {
const cases = ["mflac0_rc4"]
for (const name of cases) {
const {key, clearText, cipherText} = loadTestDataCipher(name)
const c = new QmcRC4Cipher(key)
c.decrypt(cipherText, 0)
expect(cipherText).toStrictEqual(clearText)
}
})
test("rc4 cipher: first segment", async () => {
const cases = ["mflac0_rc4"]
for (const name of cases) {
const {key, clearText, cipherText} = loadTestDataCipher(name)
const c = new QmcRC4Cipher(key)
const buf = cipherText.slice(0, 128)
c.decrypt(buf, 0)
expect(buf).toStrictEqual(clearText.slice(0, 128))
}
})
test("rc4 cipher: align block (128~5120)", async () => {
const cases = ["mflac0_rc4"]
for (const name of cases) {
const {key, clearText, cipherText} = loadTestDataCipher(name)
const c = new QmcRC4Cipher(key)
const buf = cipherText.slice(128, 5120)
c.decrypt(buf, 128)
expect(buf).toStrictEqual(clearText.slice(128, 5120))
}
})
test("rc4 cipher: simple block (5120~10240)", async () => {
const cases = ["mflac0_rc4"]
for (const name of cases) {
const {key, clearText, cipherText} = loadTestDataCipher(name)
const c = new QmcRC4Cipher(key)
const buf = cipherText.slice(5120, 10240)
c.decrypt(buf, 5120)
expect(buf).toStrictEqual(clearText.slice(5120, 10240))
}
})

117
src/decrypt/qmc_cipher.ts

@ -83,3 +83,120 @@ export class QmcMapCipher implements StreamCipher {
}
}
const FIRST_SEGMENT_SIZE = 0x80;
const SEGMENT_SIZE = 5120
export class QmcRC4Cipher implements StreamCipher {
S: Uint8Array
N: number
key: Uint8Array
hash: number
constructor(key: Uint8Array) {
if (key.length == 0) {
throw Error("invalid key size")
}
this.key = key
this.N = key.length
// init seed box
this.S = new Uint8Array(this.N);
for (let i = 0; i < this.N; ++i) {
this.S[i] = i & 0xff;
}
let j = 0;
for (let i = 0; i < this.N; ++i) {
j = (this.S[i] + j + this.key[i % this.N]) % this.N;
[this.S[i], this.S[j]] = [this.S[j], this.S[i]]
}
// init hash base
this.hash = 1;
for (let i = 0; i < this.N; i++) {
let value = this.key[i];
// ignore if key char is '\x00'
if (!value) continue;
const next_hash = (this.hash * value) & 0xffffffff;
if (next_hash == 0 || next_hash <= this.hash) break;
this.hash = next_hash;
}
}
decrypt(buf: Uint8Array, offset: number): void {
let toProcess = buf.length;
let processed = 0;
const postProcess = (len: number): boolean => {
toProcess -= len;
processed += len
offset += len
return toProcess == 0
}
// Initial segment
if (offset < FIRST_SEGMENT_SIZE) {
const len_segment = Math.min(buf.length, FIRST_SEGMENT_SIZE - offset);
this.encFirstSegment(buf.subarray(0, len_segment), offset);
if (postProcess(len_segment)) return
}
// align segment
if (offset % SEGMENT_SIZE != 0) {
const len_segment = Math.min(SEGMENT_SIZE - (offset % SEGMENT_SIZE), toProcess);
this.encASegment(buf.subarray(processed, processed + len_segment), offset);
if (postProcess(len_segment)) return
}
// Batch process segments
while (toProcess > SEGMENT_SIZE) {
this.encASegment(buf.subarray(processed, processed + SEGMENT_SIZE), offset);
postProcess(SEGMENT_SIZE)
}
// Last segment (incomplete segment)
if (toProcess > 0) {
this.encASegment(buf.subarray(processed), offset);
}
}
private encFirstSegment(buf: Uint8Array, offset: number) {
for (let i = 0; i < buf.length; i++) {
buf[i] ^= this.key[this.getSegmentSkip(offset + i)];
}
}
private encASegment(buf: Uint8Array, offset: number) {
// Initialise a new seed box
const S = this.S.slice(0)
// Calculate the number of bytes to skip.
// The initial "key" derived from segment id, plus the current offset.
const skipLen = (offset % SEGMENT_SIZE) + this.getSegmentSkip(offset / SEGMENT_SIZE)
// decrypt the block
let j = 0;
let k = 0;
for (let i = -skipLen; i < buf.length; i++) {
j = (j + 1) % this.N;
k = (S[j] + k) % this.N;
[S[k], S[j]] = [S[j], S[k]]
if (i >= 0) {
buf[i] ^= S[(S[j] + S[k]) % this.N];
}
}
}
private getSegmentSkip(id: number): number {
const seed = this.key[id % this.N]
const idx = (this.hash / ((id + 1) * seed) * 100.0) | 0;
return idx % this.N
}
}

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