Android 通过JNI C++进行MD5加密

最近升级了Android Studio 3.0.1。版本升级，越是觉得好用了。

Android Studio使用JNI之前觉得是一件比较麻烦的事，官方文档也不多，有点无从下手。本篇以CMake方式说说如何利用JNI方式使用C++进行MD5加密，这样经过Native的方式不容易被反编译出来，所以加点复杂的盐，安全性会更高。

1、新建项目时勾选C++支持选项。然后后面每一步默认即可。

2、默认会在cpp目录下生成native-lib.cpp的文件，默认我们与C/C++代码的交互就在这个文件中。配置实在CMakeList.txt（app模块根目录下）文件中。

3、如图我们添加MD5.h和MD5.cpp文件，并在CMakeList.txt配置

4、完成这一步后，编写MD5的实现代码。
MD5.h如下：

#include <string>#include <iostream>// a small class for calculating MD5 hashes of strings or byte arrays// it is not meant to be fast or secure//// usage: 1) feed it blocks of uchars with update()//      2) finalize()//      3) get hexdigest() string//      or//      MD5(std::string).hexdigest()//// assumes that char is 8 bit and int is 32 bitclass MD5{public:    typedef unsigned int size_type; // must be 32bit    MD5();    MD5(const std::string& text);    void update(const unsigned char *buf, size_type length);    void update(const char *buf, size_type length);    MD5& finalize();    std::string hexdigest() const;    friend std::ostream& operator<<(std::ostream&, MD5 md5);private:    void init();    typedef unsigned char uint1; //  8bit    typedef unsigned int uint4;  // 32bit    enum { blocksize = 64 }; // VC6 won't eat a const static int here    void transform(const uint1 block[blocksize]);    static void decode(uint4 output[], const uint1 input[], size_type len);    static void encode(uint1 output[], const uint4 input[], size_type len);    bool finalized;    uint1 buffer[blocksize]; // bytes that didn't fit in last 64 byte chunk    uint4 count[2];   // 64bit counter for number of bits (lo, hi)    uint4 state[4];   // digest so far    uint1 digest[16]; // the result    // low level logic operations    static inline uint4 F(uint4 x, uint4 y, uint4 z);    static inline uint4 G(uint4 x, uint4 y, uint4 z);    static inline uint4 H(uint4 x, uint4 y, uint4 z);    static inline uint4 I(uint4 x, uint4 y, uint4 z);    static inline uint4 rotate_left(uint4 x, int n);    static inline void FF(uint4 &a, uint4 b, uint4 c, uint4 d, uint4 x, uint4 s, uint4 ac);    static inline void GG(uint4 &a, uint4 b, uint4 c, uint4 d, uint4 x, uint4 s, uint4 ac);    static inline void HH(uint4 &a, uint4 b, uint4 c, uint4 d, uint4 x, uint4 s, uint4 ac);    static inline void II(uint4 &a, uint4 b, uint4 c, uint4 d, uint4 x, uint4 s, uint4 ac);};std::string md5(const std::string str);

MD5.cpp如下：

#include "MD5.h"/* system implementation headers */#include <stdio.h>#include <string.h>// Constants for MD5Transform routine.#define S11 7#define S12 12#define S13 17#define S14 22#define S21 5#define S22 9#define S23 14#define S24 20#define S31 4#define S32 11#define S33 16#define S34 23#define S41 6#define S42 10#define S43 15#define S44 21///////////////////////////////////////////////// F, G, H and I are basic MD5 functions.inline MD5::uint4 MD5::F(uint4 x, uint4 y, uint4 z) {    return x&y | ~x&z;}inline MD5::uint4 MD5::G(uint4 x, uint4 y, uint4 z) {    return x&z | y&~z;}inline MD5::uint4 MD5::H(uint4 x, uint4 y, uint4 z) {    return x^y^z;}inline MD5::uint4 MD5::I(uint4 x, uint4 y, uint4 z) {    return y ^ (x | ~z);}// rotate_left rotates x left n bits.inline MD5::uint4 MD5::rotate_left(uint4 x, int n) {    return (x << n) | (x >> (32 - n));}// FF, GG, HH, and II transformations for rounds 1, 2, 3, and 4.// Rotation is separate from addition to prevent recomputation.inline void MD5::FF(uint4 &a, uint4 b, uint4 c, uint4 d, uint4 x, uint4 s, uint4 ac) {    a = rotate_left(a + F(b, c, d) + x + ac, s) + b;}inline void MD5::GG(uint4 &a, uint4 b, uint4 c, uint4 d, uint4 x, uint4 s, uint4 ac) {    a = rotate_left(a + G(b, c, d) + x + ac, s) + b;}inline void MD5::HH(uint4 &a, uint4 b, uint4 c, uint4 d, uint4 x, uint4 s, uint4 ac) {    a = rotate_left(a + H(b, c, d) + x + ac, s) + b;}inline void MD5::II(uint4 &a, uint4 b, uint4 c, uint4 d, uint4 x, uint4 s, uint4 ac) {    a = rotate_left(a + I(b, c, d) + x + ac, s) + b;}//////////////////////////////////////////////// default ctor, just initailizeMD5::MD5(){    init();}//////////////////////////////////////////////// nifty shortcut ctor, compute MD5 for string and finalize it right awayMD5::MD5(const std::string &text){    init();    update(text.c_str(), text.length());    finalize();}//////////////////////////////void MD5::init(){    finalized = false;    count[0] = 0;    count[1] = 0;    // load magic initialization constants.    state[0] = 0x67452301;    state[1] = 0xefcdab89;    state[2] = 0x98badcfe;    state[3] = 0x10325476;}//////////////////////////////// decodes input (unsigned char) into output (uint4). Assumes len is a multiple of 4.void MD5::decode(uint4 output[], const uint1 input[], size_type len){    for (unsigned int i = 0, j = 0; j < len; i++, j += 4)        output[i] = ((uint4)input[j]) | (((uint4)input[j + 1]) << 8) |                    (((uint4)input[j + 2]) << 16) | (((uint4)input[j + 3]) << 24);}//////////////////////////////// encodes input (uint4) into output (unsigned char). Assumes len is// a multiple of 4.void MD5::encode(uint1 output[], const uint4 input[], size_type len){    for (size_type i = 0, j = 0; j < len; i++, j += 4) {        output[j] = input[i] & 0xff;        output[j + 1] = (input[i] >> 8) & 0xff;        output[j + 2] = (input[i] >> 16) & 0xff;        output[j + 3] = (input[i] >> 24) & 0xff;    }}//////////////////////////////// apply MD5 algo on a blockvoid MD5::transform(const uint1 block[blocksize]){    uint4 a = state[0], b = state[1], c = state[2], d = state[3], x[16];    decode(x, block, blocksize);    /* Round 1 */    FF(a, b, c, d, x[0], S11, 0xd76aa478); /* 1 */    FF(d, a, b, c, x[1], S12, 0xe8c7b756); /* 2 */    FF(c, d, a, b, x[2], S13, 0x242070db); /* 3 */    FF(b, c, d, a, x[3], S14, 0xc1bdceee); /* 4 */    FF(a, b, c, d, x[4], S11, 0xf57c0faf); /* 5 */    FF(d, a, b, c, x[5], S12, 0x4787c62a); /* 6 */    FF(c, d, a, b, x[6], S13, 0xa8304613); /* 7 */    FF(b, c, d, a, x[7], S14, 0xfd469501); /* 8 */    FF(a, b, c, d, x[8], S11, 0x698098d8); /* 9 */    FF(d, a, b, c, x[9], S12, 0x8b44f7af); /* 10 */    FF(c, d, a, b, x[10], S13, 0xffff5bb1); /* 11 */    FF(b, c, d, a, x[11], S14, 0x895cd7be); /* 12 */    FF(a, b, c, d, x[12], S11, 0x6b901122); /* 13 */    FF(d, a, b, c, x[13], S12, 0xfd987193); /* 14 */    FF(c, d, a, b, x[14], S13, 0xa679438e); /* 15 */    FF(b, c, d, a, x[15], S14, 0x49b40821); /* 16 */    /* Round 2 */    GG(a, b, c, d, x[1], S21, 0xf61e2562); /* 17 */    GG(d, a, b, c, x[6], S22, 0xc040b340); /* 18 */    GG(c, d, a, b, x[11], S23, 0x265e5a51); /* 19 */    GG(b, c, d, a, x[0], S24, 0xe9b6c7aa); /* 20 */    GG(a, b, c, d, x[5], S21, 0xd62f105d); /* 21 */    GG(d, a, b, c, x[10], S22, 0x2441453); /* 22 */    GG(c, d, a, b, x[15], S23, 0xd8a1e681); /* 23 */    GG(b, c, d, a, x[4], S24, 0xe7d3fbc8); /* 24 */    GG(a, b, c, d, x[9], S21, 0x21e1cde6); /* 25 */    GG(d, a, b, c, x[14], S22, 0xc33707d6); /* 26 */    GG(c, d, a, b, x[3], S23, 0xf4d50d87); /* 27 */    GG(b, c, d, a, x[8], S24, 0x455a14ed); /* 28 */    GG(a, b, c, d, x[13], S21, 0xa9e3e905); /* 29 */    GG(d, a, b, c, x[2], S22, 0xfcefa3f8); /* 30 */    GG(c, d, a, b, x[7], S23, 0x676f02d9); /* 31 */    GG(b, c, d, a, x[12], S24, 0x8d2a4c8a); /* 32 */    /* Round 3 */    HH(a, b, c, d, x[5], S31, 0xfffa3942); /* 33 */    HH(d, a, b, c, x[8], S32, 0x8771f681); /* 34 */    HH(c, d, a, b, x[11], S33, 0x6d9d6122); /* 35 */    HH(b, c, d, a, x[14], S34, 0xfde5380c); /* 36 */    HH(a, b, c, d, x[1], S31, 0xa4beea44); /* 37 */    HH(d, a, b, c, x[4], S32, 0x4bdecfa9); /* 38 */    HH(c, d, a, b, x[7], S33, 0xf6bb4b60); /* 39 */    HH(b, c, d, a, x[10], S34, 0xbebfbc70); /* 40 */    HH(a, b, c, d, x[13], S31, 0x289b7ec6); /* 41 */    HH(d, a, b, c, x[0], S32, 0xeaa127fa); /* 42 */    HH(c, d, a, b, x[3], S33, 0xd4ef3085); /* 43 */    HH(b, c, d, a, x[6], S34, 0x4881d05); /* 44 */    HH(a, b, c, d, x[9], S31, 0xd9d4d039); /* 45 */    HH(d, a, b, c, x[12], S32, 0xe6db99e5); /* 46 */    HH(c, d, a, b, x[15], S33, 0x1fa27cf8); /* 47 */    HH(b, c, d, a, x[2], S34, 0xc4ac5665); /* 48 */    /* Round 4 */    II(a, b, c, d, x[0], S41, 0xf4292244); /* 49 */    II(d, a, b, c, x[7], S42, 0x432aff97); /* 50 */    II(c, d, a, b, x[14], S43, 0xab9423a7); /* 51 */    II(b, c, d, a, x[5], S44, 0xfc93a039); /* 52 */    II(a, b, c, d, x[12], S41, 0x655b59c3); /* 53 */    II(d, a, b, c, x[3], S42, 0x8f0ccc92); /* 54 */    II(c, d, a, b, x[10], S43, 0xffeff47d); /* 55 */    II(b, c, d, a, x[1], S44, 0x85845dd1); /* 56 */    II(a, b, c, d, x[8], S41, 0x6fa87e4f); /* 57 */    II(d, a, b, c, x[15], S42, 0xfe2ce6e0); /* 58 */    II(c, d, a, b, x[6], S43, 0xa3014314); /* 59 */    II(b, c, d, a, x[13], S44, 0x4e0811a1); /* 60 */    II(a, b, c, d, x[4], S41, 0xf7537e82); /* 61 */    II(d, a, b, c, x[11], S42, 0xbd3af235); /* 62 */    II(c, d, a, b, x[2], S43, 0x2ad7d2bb); /* 63 */    II(b, c, d, a, x[9], S44, 0xeb86d391); /* 64 */    state[0] += a;    state[1] += b;    state[2] += c;    state[3] += d;    // Zeroize sensitive information.    memset(x, 0, sizeof x);}//////////////////////////////// MD5 block update operation. Continues an MD5 message-digest// operation, processing another message blockvoid MD5::update(const unsigned char input[], size_type length){    // compute number of bytes mod 64    size_type index = count[0] / 8 % blocksize;    // Update number of bits    if ((count[0] += (length << 3)) < (length << 3))        count[1]++;    count[1] += (length >> 29);    // number of bytes we need to fill in buffer    size_type firstpart = 64 - index;    size_type i;    // transform as many times as possible.    if (length >= firstpart)    {        // fill buffer first, transform        memcpy(&buffer[index], input, firstpart);        transform(buffer);        // transform chunks of blocksize (64 bytes)        for (i = firstpart; i + blocksize <= length; i += blocksize)            transform(&input[i]);        index = 0;    }    else        i = 0;    // buffer remaining input    memcpy(&buffer[index], &input[i], length - i);}//////////////////////////////// for convenience provide a verson with signed charvoid MD5::update(const char input[], size_type length){    update((const unsigned char*)input, length);}//////////////////////////////// MD5 finalization. Ends an MD5 message-digest operation, writing the// the message digest and zeroizing the context.MD5& MD5::finalize(){    static unsigned char padding[64] = {            0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,            0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,            0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0    };    if (!finalized) {        // Save number of bits        unsigned char bits[8];        encode(bits, count, 8);        // pad out to 56 mod 64.        size_type index = count[0] / 8 % 64;        size_type padLen = (index < 56) ? (56 - index) : (120 - index);        update(padding, padLen);        // Append length (before padding)        update(bits, 8);        // Store state in digest        encode(digest, state, 16);        // Zeroize sensitive information.        memset(buffer, 0, sizeof buffer);        memset(count, 0, sizeof count);        finalized = true;    }    return *this;}//////////////////////////////// return hex representation of digest as stringstd::string MD5::hexdigest() const{    if (!finalized)        return "";    char buf[33];    for (int i = 0; i < 16; i++)        sprintf(buf + i * 2, "%02x", digest[i]);    buf[32] = 0;    return std::string(buf);}//////////////////////////////std::ostream& operator<<(std::ostream& out, MD5 md5){    return out << md5.hexdigest();}//////////////////////////////std::string md5(const std::string str){    MD5 md5 = MD5(str);    return md5.hexdigest();}

5、完成这一步后，make一下project。然后在Java和native-lib.cpp中分别编写MD5的测试代码：
比如在MainActivity.java中定义native的方法：

// Used to load the 'native-lib' library on application startup.static {    System.loadLibrary("native-lib");}public native String getMd5(String origin);

然后在native-lib.cpp中完成实现：

//记得导入头文件#include "MD5.h"//使用c中的md5加密，可以将盐加入不容易被反编译出来JNIEXPORT jstring JNICALLJava_com_dengpan_MainActivity_getMd5(JNIEnv *env, jobject, jstring str) {    const char *originStr;    //将jstring转化成char *类型    originStr = env->GetStringUTFChars(str, false);    MD5 md5 = MD5(originStr);    std::string md5Result = md5.hexdigest();    //将char *类型转化成jstring返回给Java层    return env->NewStringUTF(md5Result.c_str());}

6、于是运行程序在MainActivity的onCreate方法中可以看到程序打印出结果。

System.out.println("MD5加密结果：" + getMd5("123456"));##运行结果I/System.out: MD5加密结果：e10adc3949ba59abbe56e057f20f883e

另外，JNI中常用在C++中打印出log，需要有如下配置：

#include <android/log.h>#define LOG_TAG   "lib_native_log"#define  LOGI(...) __android_log_print(ANDROID_LOG_INFO,LOG_TAG,__VA_ARGS__)#define LOGE(...)  __android_log_print(ANDROID_LOG_ERROR,LOG_TAG,__VA_ARGS__)

另外，在JNI中调用Java定义的方法：比如在MainActivity中定义

//定义和native交互的方法public native void toast();//....//定义被C++ 调用的方法public void toastMain(Context c){        Toast.makeText(c, "通过Native调用出现的提示", Toast.LENGTH_SHORT).show();}

那么在native-lib.cpp中定义方法：

//需要调用此方法，则此方法定义在调用方法前。获取全局Contextjobject getGlobalContext(JNIEnv *env){    //获取Activity Thread的实例对象    jclass activityThread = env->FindClass("android/app/ActivityThread");    jmethodID currentActivityThread = env->GetStaticMethodID(activityThread, "currentActivityThread", "()Landroid/app/ActivityThread;");    jobject at = env->CallStaticObjectMethod(activityThread, currentActivityThread);    //获取Application，也就是全局的Context    jmethodID getApplication = env->GetMethodID(activityThread, "getApplication", "()Landroid/app/Application;");    jobject context = env->CallObjectMethod(at, getApplication);    return context;}JNIEXPORT void JNICALLJava_com_dengpan_MainActivity_toast(JNIEnv *env, jobject obj) {    jclass dpclazz = env->FindClass("com/dengpan/MainActivity");    if(dpclazz==0){        LOGE("find class error");        return;    }    LOGI("find class ");    //2 寻找class里面的方法    jmethodID method1 = env->GetMethodID(dpclazz,"toastMain","(Landroid/content/Context;)V");//    if(method1==0){        LOGE("find method1 error");        return;    }    LOGI("find method1");    //3 .调用这个方法    // void (*CallVoidMethod)(JNIEnv*, jobject, jmethodID, ...);    env->CallVoidMethod(obj,method1,getGlobalContext(env));}

注意，在native-lib.cpp定义的方法一定要放在extern "C" {}里面，不然编译运行时会报一些链接错误。

CMake的方式会自动将CPP文件编译成so文件拷贝打包到apk文件中。 如图：

至此JNI方法调用暂时写到这儿。