秒破iOS APP加密数据

毕业第一步，先把项目需求实现了。其实这篇文章和之前Android上frida破解加密数据思路是一致的，因为iOS作为一种闭源系统，没有Android那么多的packers和so库，iOS官方封装了自己统一的Crypto库：
CommonCryptor.h/CommonDigest.h/CommonHMAC.h，所以我们hook起来也很方便。拿我们之前搞过的一个投资APP(v4.2.9)为例，点击登录

request包

response包

直接hook CCCrypt函数，将这个脚本保存为CC_hook.js

// Intercept the CCCrypt call.
Interceptor.attach(Module.findExportByName('libcommonCrypto.dylib', 'CCCrypt'), {
    onEnter: function (args) {
        // Save the arguments
        this.operation   = args[0]
        this.CCAlgorithm = args[1]
        this.CCOptions   = args[2]
        this.keyBytes    = args[3]
        this.keyLength   = args[4]
        this.ivBuffer    = args[5]
        this.inBuffer    = args[6]
        this.inLength    = args[7]
        this.outBuffer   = args[8]
        this.outLength   = args[9]
        this.outCountPtr = args[10]

        console.log('CCCrypt(' + 
            'operation: '   + this.operation    +', ' +
            'CCAlgorithm: ' + this.CCAlgorithm  +', ' +
            'CCOptions: '   + this.CCOptions    +', ' +
            'keyBytes: '    + this.keyBytes     +', ' +
            'keyLength: '   + this.keyLength    +', ' +
            'ivBuffer: '    + this.ivBuffer     +', ' +
            'inBuffer: '    + this.inBuffer     +', ' +
            'inLength: '    + this.inLength     +', ' +
            'outBuffer: '   + this.outBuffer    +', ' +
            'outLength: '   + this.outLength    +', ' +
            'outCountPtr: ' + this.outCountPtr  +')')

        if (this.operation == 0) {
            // Show the buffers here if this an encryption operation
            console.log("In buffer:")
            console.log(hexdump(ptr(this.inBuffer), {
                length: this.inLength.toInt32(),
                header: true,
                ansi: true
            }))
            console.log("Key: ")
            console.log(hexdump(ptr(this.keyBytes), {
                length: this.keyLength.toInt32(),
                header: true,
                ansi: true
            }))
            console.log("IV: ")
            console.log(hexdump(ptr(this.ivBuffer), {
                length: this.keyLength.toInt32(),
                header: true,
                ansi: true
            }))
        }
    },
    onLeave: function (retVal) {
        if (this.operation == 1) {
            // Show the buffers here if this a decryption operation
            console.log("Out buffer:")
            console.log(hexdump(ptr(this.outBuffer), {
                length: Memory.readUInt(this.outCountPtr),
                header: true,
                ansi: true
            }))
            console.log("Key: ")
            console.log(hexdump(ptr(this.keyBytes), {
                length: this.keyLength.toInt32(),
                header: true,
                ansi: true
            }))
            console.log("IV: ")
            console.log(hexdump(ptr(this.ivBuffer), {
                length: this.keyLength.toInt32(),
                header: true,
                ansi: true
            }))
        }
    }
})

直接使用 frida -U -f com.Dongfangjinke.dongfanghui -l CC_hook.js –no-pause

operation: 0x0代表加密，0x1代表解密

enum {
	kCCEncrypt = 0,	
	kCCDecrypt = 1	
};

CCAlgorithm: 0x0指加密方式是AES加密，0x1指DES加密，0x2指3DES加密

enum {
	kCCAlgorithmAES128 = 0,
	kCCAlgorithmAES    = 0,
	kCCAlgorithmDES    = 1,
	kCCAlgorithm3DES   = 2,		
	kCCAlgorithmCAST   = 3,		
	kCCAlgorithmRC4    = 4,
	kCCAlgorithmRC2	   = 5	
};

CCOptions: 0x1指模式是CBC，通常0x3指ECB

enum {
	kCCOptionPKCS7Padding	= 0x0001,
	kCCOptionECBMode	= 0x0002
};

size_t keyLength，指密钥位数（真正决定密钥长度的地方）。AES数据块长度为128位，所以IV长度需要为16个字符（ECB模式不用IV），密钥根据指定密钥位数分别为16、24、32个字符，IV与密钥超过长度则截取，不足则在末尾填充’\0’补足

enum {
    kCCKeySizeAES128          = 16,
    kCCKeySizeAES192          = 24,
    kCCKeySizeAES256          = 32,
    kCCKeySizeDES             = 8,
    kCCKeySize3DES            = 24,
    kCCKeySizeMinCAST         = 5,
    kCCKeySizeMaxCAST         = 16,
    kCCKeySizeMinRC4          = 1,
    kCCKeySizeMaxRC4          = 512,
    kCCKeySizeMinRC2          = 1,
    kCCKeySizeMaxRC2          = 128,
    kCCKeySizeMinBlowfish     = 8,
    kCCKeySizeMaxBlowfish     = 56,
};

具体参阅CommonCryptor.h各参数意义，key=DATA_KEY20150116和iv=20150116和Android客户端是一致的，而且由于Android是在so库生成的AES加密，避免了Android端java层hook不到的情况。

---

2021.6更新： 对上述脚本进行优化，增加了Base64转化过程，方便查找和过滤。当KEY与IV不是明文时，以Hex形式打印，并对原始的CCCrypt函数参数进行翻译。脚本放在了仓库里 CC_Hook_2Base64.js

参考
appmon project提供的scripts
hack.lu的scripts
Frida-javascript-api-apiresolver