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Add support for ZipCrypto decryption #129
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,159 @@ | ||
| 'use strict'; | ||
| var utils = require('./utils'); | ||
|
|
||
| /** | ||
| * Based on the algorithm described in | ||
| * http://www.pkware.com/documents/casestudies/APPNOTE.TXT | ||
| */ | ||
|
|
||
| var ZipCrypto = function(loadOptions) { | ||
| this.encryptionKeys = null; | ||
| this.retrievePasswordCallback = loadOptions.retrievePasswordCallback; | ||
| this.retrieveEncryptionKeysCallback = loadOptions.retrieveEncryptionKeysCallback; | ||
| this.invalidPasswordCallback = loadOptions.invalidPasswordCallback; | ||
| }; | ||
|
|
||
| /** | ||
| * Requests password/encryption keys (once), primes the encryption keys, if necessary, | ||
| * and returns them to the caller. | ||
| * @return {number[]} An array of 3 32-bit numeric pre-primed encryption keys | ||
| * @throws {Error} if the password callbacks are not set or return incorrect data types | ||
| */ | ||
| ZipCrypto.prototype.getEncryptionKeys = function() { | ||
| if (!this.encryptionKeys) { | ||
| if (typeof this.retrievePasswordCallback != "function" && | ||
| typeof this.retrieveEncryptionKeysCallback != "function") { | ||
| throw new Error("retrievePasswordCallback or retrieveEncryptionKeysCallback must be set for encrypted ZIP files"); | ||
| } | ||
|
|
||
| if (this.retrieveEncryptionKeysCallback) { | ||
| var keys = this.retrieveEncryptionKeysCallback(); | ||
| if(!(keys instanceof Array)) throw new Error("retrieveEncryptionKeysCallback must return an array of encryption keys"); | ||
| if(keys.length != 3) throw new Error("retrieveEncryptionKeysCallback must return an array of 3 encryption keys"); | ||
| for(var i=0; i<keys.length; i++) { | ||
| if(typeof keys[i] != 'number' || isNaN(keys[i])) throw new Error("retrieveEncryptionKeysCallback must return an array of numeric keys"); | ||
| } | ||
| this.encryptionKeys = keys; | ||
| } else { | ||
| var password = this.retrievePasswordCallback(); | ||
| if(!password && password !== '') return; // No password supplied. note that password could be an empty string | ||
| if(typeof password != 'string') { | ||
| throw new Error("retrievePasswordCallback must return a string"); | ||
| } | ||
| // Magic values | ||
| this.encryptionKeys = [ | ||
| 0x12345678, | ||
| 0x23456789, | ||
| 0x34567890 | ||
| ]; | ||
| // Prime keys | ||
| for (var j=0; j<password.length; j++) { | ||
| updateKeys(this.encryptionKeys, password.charCodeAt(j)); | ||
| } | ||
| } | ||
| } | ||
|
|
||
| return this.encryptionKeys.slice(0); // Don't return originals, since they would get updated as we go | ||
| }; | ||
|
|
||
| /** | ||
| * Calls the callback for invalid password if supplied, otherwise, throws an error | ||
| * @return {boolean} Return value from callback. | ||
| * TRUE if password validation should be ignored | ||
| * @throws {Error} if invalidPasswordCallback was not supplied | ||
| */ | ||
| ZipCrypto.prototype.invalidPassword = function(header, crc32) { | ||
| if (typeof this.invalidPasswordCallback != "function") { | ||
| throw new Error("Supplied password is invalid"); | ||
| } | ||
|
|
||
| return this.invalidPasswordCallback(header, crc32); | ||
| }; | ||
|
|
||
| /** | ||
| * Decrypts data using ZipCrypto algorithm. Validates password if crc32 is supplied | ||
| * @param {Uint8Array} data Data to be decrypted. | ||
| * @param {number} [crc32] CRC32 hash of the data. If supplied, the password is validated. | ||
| * @return {Uint8Array} Decrypted data in the same format as was passed in | ||
| */ | ||
| ZipCrypto.prototype.decryptData = function(data, crc32) { | ||
| if(data instanceof Uint8Array) { | ||
| return this.decryptDataAsUint8Array(data, crc32); | ||
| } | ||
|
|
||
| throw new Error("ZipCrypto decryption is only supported for Uint8Array data"); | ||
| }; | ||
|
|
||
| /** | ||
| * @see ZipCrypto.decryptData | ||
| */ | ||
| ZipCrypto.prototype.decryptDataAsUint8Array = function(data, crc32) { | ||
| var keys = this.getEncryptionKeys(); | ||
| for (var i=0; i<data.length; i++) { | ||
| data[i] = decryptByte(keys, data[i]); | ||
| if (i == 11 && crc32 !== undefined) { | ||
| // Validate checksum | ||
| // 12th byte is the high order byte of crc32 | ||
| if ( (data[i] & 0xFF) != (crc32 >>> 24) && | ||
| !this.invalidPassword(data.subarray(0,12), crc32) ) { | ||
| return; | ||
| } | ||
| } | ||
| } | ||
| return data.subarray(12); // First 12 bytes are encryption header | ||
| }; | ||
|
|
||
| /** | ||
| * Updates a given CRC32 hash with an additional byte | ||
| * @param {number} crc CRC32 hash as a 32-bit number | ||
| * @param {number} b A single byte | ||
| * @return {number} Updated CRC32 hash | ||
| */ | ||
| ZipCrypto.crc32Byte = function(crc, b) { | ||
| var x = utils.crcTable[(crc ^ b) & 0xFF]; | ||
| return (crc >>> 8) ^ x; | ||
| }; | ||
|
|
||
| /** | ||
| * Updates encyption keys | ||
| * @param {number[]} keys Encryption keys to be updated | ||
| * @param {number} b A single byte | ||
| */ | ||
| function updateKeys(keys, b) { | ||
| keys[0] = ZipCrypto.crc32Byte(keys[0], b); | ||
| keys[1] = u32Multiply(keys[1] + (keys[0] & 0xFF), 0x08088405) + 1; | ||
| keys[2] = ZipCrypto.crc32Byte(keys[2], keys[1] >> 24); | ||
| } | ||
|
|
||
| /** | ||
| * Decrypts a single byte of data | ||
| * @param {number[]} keys Encryption keys | ||
| * @param {number} b A single byte | ||
| * @return {number} Decrypted byte | ||
| */ | ||
| function decryptByte(keys, b) { | ||
| var tmp = keys[2] | 2; | ||
| b = b ^ (u32Multiply(tmp,tmp ^ 1) >> 8); | ||
| updateKeys(keys, b); | ||
| return b; | ||
| } | ||
|
|
||
| /** | ||
| * Performs 32-bit multiplication. | ||
| * Discards overflow bits and maintains accuracy for the low significance bits | ||
| * @param {number} a | ||
| * @param {number} b | ||
| * @return 32-bit product of a and b | ||
| */ | ||
| function u32Multiply(a, b) { | ||
| // We have a 52 bit mantissa, so we can safely multiply 32 bit and 16 bit | ||
| // numbers without losing accuracy (result cannot be more than 48 bits) | ||
| var a1 = a >>> 16; // MSB 16 bits | ||
| var a2 = a & 0xFFFF; // LSB 16 bits | ||
| // a1 and a2 are always positive here | ||
| b = b >>> 0; // Truncate MSBs past 32 bits | ||
|
|
||
| return ( ( (b * a1) << 16 >>> 0) + b * a2 ) >>> 0; // Don't return negative numbers | ||
| } | ||
|
|
||
| module.exports = ZipCrypto; | ||
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Seems like this is not always set correctly (or maybe I'm doing something wrong here). E.g. encrypted.zip I generated under cygwin (included in the tests) does not validate here, but the contents do get decrypted correctly. Creating a zip with 7zip does validate though.