feat(QMCv2): add rc4 cipher
(cherry picked from commit 6b5b4d3bf5f6285e908808d48dee4e2e4ae8c3a2)
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@ -1,4 +1,4 @@
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import {QmcMapCipher, QmcStaticCipher} from "@/decrypt/qmc_cipher";
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import {QmcMapCipher, QmcRC4Cipher, QmcStaticCipher} from "@/decrypt/qmc_cipher";
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import fs from 'fs'
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test("static cipher [0x7ff8,0x8000) ", () => {
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@ -27,17 +27,6 @@ test("static cipher [0,0x10) ", () => {
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expect(buf).toStrictEqual(expected)
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})
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function loadTestDataMapCipher(name: string): {
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key: Uint8Array,
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cipherText: Uint8Array,
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clearText: Uint8Array
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} {
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return {
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key: fs.readFileSync(`testdata/${name}_key.bin`),
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cipherText: fs.readFileSync(`testdata/${name}_raw.bin`),
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clearText: fs.readFileSync(`testdata/${name}_target.bin`)
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}
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}
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test("map cipher: get mask", () => {
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const expected = new Uint8Array([
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@ -53,10 +42,22 @@ test("map cipher: get mask", () => {
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expect(buf).toStrictEqual(expected)
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})
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function loadTestDataCipher(name: string): {
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key: Uint8Array,
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cipherText: Uint8Array,
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clearText: Uint8Array
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} {
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return {
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key: fs.readFileSync(`testdata/${name}_key.bin`),
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cipherText: fs.readFileSync(`testdata/${name}_raw.bin`),
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clearText: fs.readFileSync(`testdata/${name}_target.bin`)
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}
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}
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test("map cipher: real file", async () => {
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const cases = ["mflac_map", "mgg_map"]
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for (const name of cases) {
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const {key, clearText, cipherText} = loadTestDataMapCipher(name)
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const {key, clearText, cipherText} = loadTestDataCipher(name)
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const c = new QmcMapCipher(key)
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c.decrypt(cipherText, 0)
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@ -64,3 +65,51 @@ test("map cipher: real file", async () => {
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expect(cipherText).toStrictEqual(clearText)
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}
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})
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test("rc4 cipher: real file", async () => {
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const cases = ["mflac0_rc4"]
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for (const name of cases) {
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const {key, clearText, cipherText} = loadTestDataCipher(name)
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const c = new QmcRC4Cipher(key)
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c.decrypt(cipherText, 0)
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expect(cipherText).toStrictEqual(clearText)
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}
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})
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test("rc4 cipher: first segment", async () => {
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const cases = ["mflac0_rc4"]
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for (const name of cases) {
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const {key, clearText, cipherText} = loadTestDataCipher(name)
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const c = new QmcRC4Cipher(key)
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const buf = cipherText.slice(0, 128)
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c.decrypt(buf, 0)
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expect(buf).toStrictEqual(clearText.slice(0, 128))
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}
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})
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test("rc4 cipher: align block (128~5120)", async () => {
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const cases = ["mflac0_rc4"]
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for (const name of cases) {
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const {key, clearText, cipherText} = loadTestDataCipher(name)
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const c = new QmcRC4Cipher(key)
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const buf = cipherText.slice(128, 5120)
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c.decrypt(buf, 128)
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expect(buf).toStrictEqual(clearText.slice(128, 5120))
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}
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})
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test("rc4 cipher: simple block (5120~10240)", async () => {
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const cases = ["mflac0_rc4"]
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for (const name of cases) {
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const {key, clearText, cipherText} = loadTestDataCipher(name)
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const c = new QmcRC4Cipher(key)
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const buf = cipherText.slice(5120, 10240)
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c.decrypt(buf, 5120)
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expect(buf).toStrictEqual(clearText.slice(5120, 10240))
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}
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})
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@ -83,3 +83,120 @@ export class QmcMapCipher implements StreamCipher {
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}
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}
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const FIRST_SEGMENT_SIZE = 0x80;
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const SEGMENT_SIZE = 5120
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export class QmcRC4Cipher implements StreamCipher {
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S: Uint8Array
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N: number
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key: Uint8Array
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hash: number
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constructor(key: Uint8Array) {
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if (key.length == 0) {
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throw Error("invalid key size")
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}
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this.key = key
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this.N = key.length
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// init seed box
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this.S = new Uint8Array(this.N);
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for (let i = 0; i < this.N; ++i) {
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this.S[i] = i & 0xff;
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}
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let j = 0;
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for (let i = 0; i < this.N; ++i) {
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j = (this.S[i] + j + this.key[i % this.N]) % this.N;
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[this.S[i], this.S[j]] = [this.S[j], this.S[i]]
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}
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// init hash base
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this.hash = 1;
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for (let i = 0; i < this.N; i++) {
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let value = this.key[i];
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// ignore if key char is '\x00'
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if (!value) continue;
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const next_hash = (this.hash * value) & 0xffffffff;
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if (next_hash == 0 || next_hash <= this.hash) break;
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this.hash = next_hash;
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}
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}
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decrypt(buf: Uint8Array, offset: number): void {
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let toProcess = buf.length;
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let processed = 0;
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const postProcess = (len: number): boolean => {
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toProcess -= len;
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processed += len
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offset += len
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return toProcess == 0
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}
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// Initial segment
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if (offset < FIRST_SEGMENT_SIZE) {
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const len_segment = Math.min(buf.length, FIRST_SEGMENT_SIZE - offset);
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this.encFirstSegment(buf.subarray(0, len_segment), offset);
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if (postProcess(len_segment)) return
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}
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// align segment
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if (offset % SEGMENT_SIZE != 0) {
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const len_segment = Math.min(SEGMENT_SIZE - (offset % SEGMENT_SIZE), toProcess);
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this.encASegment(buf.subarray(processed, processed + len_segment), offset);
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if (postProcess(len_segment)) return
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}
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// Batch process segments
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while (toProcess > SEGMENT_SIZE) {
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this.encASegment(buf.subarray(processed, processed + SEGMENT_SIZE), offset);
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postProcess(SEGMENT_SIZE)
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}
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// Last segment (incomplete segment)
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if (toProcess > 0) {
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this.encASegment(buf.subarray(processed), offset);
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}
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}
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private encFirstSegment(buf: Uint8Array, offset: number) {
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for (let i = 0; i < buf.length; i++) {
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buf[i] ^= this.key[this.getSegmentSkip(offset + i)];
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}
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}
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private encASegment(buf: Uint8Array, offset: number) {
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// Initialise a new seed box
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const S = this.S.slice(0)
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// Calculate the number of bytes to skip.
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// The initial "key" derived from segment id, plus the current offset.
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const skipLen = (offset % SEGMENT_SIZE) + this.getSegmentSkip(offset / SEGMENT_SIZE)
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// decrypt the block
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let j = 0;
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let k = 0;
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for (let i = -skipLen; i < buf.length; i++) {
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j = (j + 1) % this.N;
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k = (S[j] + k) % this.N;
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[S[k], S[j]] = [S[j], S[k]]
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if (i >= 0) {
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buf[i] ^= S[(S[j] + S[k]) % this.N];
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}
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}
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}
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private getSegmentSkip(id: number): number {
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const seed = this.key[id % this.N]
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const idx = (this.hash / ((id + 1) * seed) * 100.0) | 0;
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return idx % this.N
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}
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}
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