JNI - 加解密时错误的使用strlen和strncpy函数

最近在将一个Java的解密算法移植到C层，碰到一些问题，在此记录下来。

算法步骤：
1. 给定一个字符串，获取byte数组。
2. 对byte数组，从低到高排序
3. 对byte数组md5
4. 对byte数组，从高到底排序
5. 对byte数组md5
6. 对byte数组，从低到高排序
7. 对byte数组md5拿到最后的最结果

以上的算法在Java层还是很容易实现的：

/** * byte数组排序， * * @param bytes * @param isAsc true排序低到高,false排序高到低 * @return */private static byte[] orderBytes(byte[] bytes, boolean isAsc) {    Integer[] unsignedBytes = new Integer[bytes.length];    for (int i = 0; i < bytes.length; i++) {        unsignedBytes[i] = bytes[i] & 0xff;    }    if (isAsc) {//升序        Arrays.sort(unsignedBytes);    } else {//降序        Arrays.sort(unsignedBytes, new IntegerComparator());    }    for (int i = 0; i < unsignedBytes.length; i++) {        int tmp = unsignedBytes[i];        bytes[i] = (byte) tmp;    }    return bytes;}public static byte[] MD5Encrypt(byte[] bytes) {    try {        MessageDigest md = MessageDigest.getInstance("MD5");        md.update(bytes);        byte[] b = md.digest();        return b;    } catch (NoSuchAlgorithmException e) {        // TODO Auto-generated catch block        e.printStackTrace();        return null;    }}

但是，移植C层时总会碰到莫名其妙的问题：
1. MD5计算结果不一致
2. unsigned char 数组中出现\0导致，strlen和strncpy失效

知道问题后，修改也就容易了。

在网上找了好久才找到一个Java平台和C平台互通的MD5算法:

// 头文件#ifndef _DMSUTIL_H#define _DMSUTIL_H#ifdef __cplusplusextern "C" {#endifvoid EncryptMD5(unsigned char *output, unsigned char *input, int length);void EncryptMD5str(char *output, unsigned char *input, int len);#ifdef __cplusplus}#endif#endif// .C文件#include <stdio.h> #include <string.h> #include "md5.h"/*MD5 context*/typedef struct MD5_CTX_S {    unsigned int state[4];    unsigned int count[2];    char buffer[64];} MD5_CTX;static unsigned char digest[16];/*MD5 initialization*/static void MD5Init(MD5_CTX *);/*MD5 block update operation*/static void MD5Update(MD5_CTX *, unsigned char *, unsigned int);/*Ends an MD5 message-digest operation*/static void MD5Final(unsigned char [16], MD5_CTX *);/*MD5 padding*/static void __md5_Pad(MD5_CTX *);/*MD5 basic transformation*/static void __md5_Transform(unsigned int [4], unsigned char [64]);#ifdef i386#define __md5_Encode memcpy#define __md5_Decode memcpy #else /* i386 *//** __md5_Encodes input (u_int32_t) into output (unsigned char). Assumes len is * a multiple of 4. */static void__md5_Encode(unsigned char *output, unsigned int *input, unsigned int len) {    unsigned int i, j;    for (i = 0, j = 0; j < len; i++, j += 4) {        output[j] = (unsigned char) (input[i] & 0xff);        output[j + 1] = (unsigned char) ((input[i] >> 8) & 0xff);        output[j + 2] = (unsigned char) ((input[i] >> 16) & 0xff);        output[j + 3] = (unsigned char) ((input[i] >> 24) & 0xff);    }}/** __md5_Decodes input (unsigned char) into output (u_int32_t). Assumes len is * a multiple of 4. */static void__md5_Decode(unsigned int *output, unsigned char *input, unsigned int len) {    unsigned int i, j;    for (i = 0, j = 0; j < len; i++, j += 4)        output[i] = ((unsigned int) input[j]) | (((unsigned int) input[j + 1]) << 8) |                    (((unsigned int) input[j + 2]) << 16) | (((unsigned int) input[j + 3]) << 24);}#endif /* i386 *//* F, G, H and I are basic MD5 functions. */#define F(x, y, z) (((x) & (y)) | ((~x) & (z)))#define G(x, y, z) (((x) & (z)) | ((y) & (~z)))#define H(x, y, z) ((x) ^ (y) ^ (z))#define I(x, y, z) ((y) ^ ((x) | (~z)))/* ROTATE_LEFT rotates x left n bits. */#define ROTATE_LEFT(x, n) (((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. */#define FF(a, b, c, d, x, s, ac) { \     (a) += F ((b), (c), (d)) + (x) + (unsigned int)(ac); \     (a) = ROTATE_LEFT ((a), (s)); \     (a) += (b); \     }#define GG(a, b, c, d, x, s, ac) { \     (a) += G ((b), (c), (d)) + (x) + (unsigned int)(ac); \     (a) = ROTATE_LEFT ((a), (s)); \     (a) += (b); \     }#define HH(a, b, c, d, x, s, ac) { \     (a) += H ((b), (c), (d)) + (x) + (unsigned int)(ac); \     (a) = ROTATE_LEFT ((a), (s)); \     (a) += (b); \     }#define II(a, b, c, d, x, s, ac) { \     (a) += I ((b), (c), (d)) + (x) + (unsigned int)(ac); \     (a) = ROTATE_LEFT ((a), (s)); \     (a) += (b); \     }/* MD5 initialization. Begins an MD5 operation, writing a new context. */static void MD5Init(MD5_CTX *context) {    context->count[0] = context->count[1] = 0;    /* Load magic initialization constants.  */    context->state[0] = 0x67452301;    context->state[1] = 0xefcdab89;    context->state[2] = 0x98badcfe;    context->state[3] = 0x10325476;}/** MD5 block update operation. Continues an MD5 message-digest * operation, processing another message block, and updating the * context. */static void MD5Update(MD5_CTX *context, unsigned char *input, unsigned int inputLen) {    unsigned int i, index, partLen;    /* Compute number of bytes mod 64 */    index = (unsigned int) ((context->count[0] >> 3) & 0x3F);    /* Update number of bits */    if ((context->count[0] += ((unsigned int) inputLen << 3))        < ((unsigned int) inputLen << 3))        context->count[1]++;    context->count[1] += ((unsigned int) inputLen >> 29);    partLen = 64 - index;    /* Transform as many times as possible. */    if (inputLen >= partLen) {        memcpy((void *) &context->buffer[index], (const void *) input,               partLen);        __md5_Transform(context->state, (unsigned char *) context->buffer);        for (i = partLen; i + 63 < inputLen; i += 64)            __md5_Transform(context->state, &input[i]);        index = 0;    }    else        i = 0;    /* Buffer remaining input */    memcpy((void *) &context->buffer[index], (const void *) &input[i],           inputLen - i);}/** MD5 padding. Adds padding followed by original length. */static void __md5_Pad(MD5_CTX *context) {    unsigned char bits[8];    unsigned int index, padLen;    unsigned char PADDING[64];    memset(PADDING, 0, sizeof(PADDING));    PADDING[0] = 0x80;    /* Save number of bits */    __md5_Encode(bits, context->count, 8);    /* Pad out to 56 mod 64. */    index = (unsigned int) ((context->count[0] >> 3) & 0x3f);    padLen = (index < 56) ? (56 - index) : (120 - index);    MD5Update(context, PADDING, padLen);    /* Append length (before padding) */    MD5Update(context, bits, 8);}/** MD5 finalization. Ends an MD5 message-digest operation, writing the * the message digest and zeroizing the context. */static void MD5Final(unsigned char digest[16], MD5_CTX *context) {    /* Do padding. */    __md5_Pad(context);    /* Store state in digest */    __md5_Encode(digest, context->state, 16);    /* Zeroize sensitive information. */    memset((void *) context, 0, sizeof(*context));}/* MD5 basic transformation. Transforms state based on block. */static void__md5_Transform(unsigned int state[4], unsigned char block[64]) {    unsigned int a, b, c, d, x[16];    a = state[0];    b = state[1];    c = state[2];    d = state[3];    __md5_Decode(x, block, 64);    /* Round 1 */#define S11 7#define S12 12#define S13 17#define S14 22    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 */#define S21 5#define S22 9#define S23 14#define S24 20    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 */#define S31 4#define S32 11#define S33 16#define S34 23    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 */#define S41 6#define S42 10#define S43 15#define S44 21    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((void *) x, 0, sizeof(x));}void EncryptMD5(unsigned char *output, unsigned char *input, int length) {    MD5_CTX context;    MD5Init(&context);    MD5Update(&context, input, length);    MD5Final(output, &context);    return;}void EncryptMD5str(char *output, unsigned char *input, int len) {    unsigned char strcrypt[16];    int i;    MD5_CTX context;    MD5Init(&context);    MD5Update(&context, input, len);    MD5Final(strcrypt, &context);    for (i = 0; i < 16; i++)        sprintf(&output[i * 2], "%02X", strcrypt[i]);    return;} 

在排序函数中尽量不使用strlen和strncpy，以及在md5时传递length进去：

#define LEN 16int compInc(const void *a, const void *b) {    return *(unsigned char *) a - *(unsigned char *) b;}int compDec(const void *a, const void *b) {    return *(unsigned char *) b - *(unsigned char *) a;}void orderBytes(unsigned char *bytes, int length, int isAsc) {    int i;    unsigned char *unsignedBytes = (unsigned char *) malloc(length * sizeof(unsigned char));    for (i = 0; i < length; ++i) {        unsignedBytes[i] = (unsigned char) (bytes[i] & 0xff);    }    if (isAsc) {        // 升序        qsort(unsignedBytes, length, sizeof(unsignedBytes[0]), compInc);    } else {        qsort(unsignedBytes, length, sizeof(unsignedBytes[0]), compDec);        //降序    }    for (i = 0;i < length; i++) {        bytes[i] = unsignedBytes[i];    }    free(unsignedBytes);}

下面是JNI的代码，也很简单：

jbyte *encryptKeyContent = env->GetByteArrayElements(encryptKeyContent_, NULL);   int length = env->GetArrayLength(encryptKeyContent_);   encryptKeyContent[length] = '\0';   // 1   orderBytes((unsigned char *) encryptKeyContent, length, 1);   unsigned char *unsignedBytes = (unsigned char *) malloc((LEN + 1) * sizeof(unsigned char));   EncryptMD5(unsignedBytes, (unsigned char *) encryptKeyContent, length);   unsignedBytes[LEN] = '\0';   // 2   orderBytes(unsignedBytes, LEN, 0);   unsigned char *unsignedBytes2 = (unsigned char *) malloc((LEN + 1) * sizeof(unsigned char));   EncryptMD5(unsignedBytes2, unsignedBytes, LEN);   unsignedBytes2[LEN] = '\0';   free(unsignedBytes);   // 3   orderBytes(unsignedBytes2, LEN, 1);   unsigned char *unsignedBytes3 = (unsigned char *) malloc((LEN + 1) * sizeof(unsigned char));   EncryptMD5(unsignedBytes3, unsignedBytes2, LEN);   unsignedBytes3[LEN] = '\0';   free(unsignedBytes2);   env->ReleaseByteArrayElements(encryptKeyContent_, encryptKeyContent, 0);   LOGD("M3U8_KEY_CONTENT decrypt SUCCESS %s", unsignedBytes3);   jbyteArray jarray = env->NewByteArray(LEN);   env->SetByteArrayRegion(jarray, 0, LEN, (jbyte *) unsignedBytes3);}