使用 Emscripten 编译的 WebAssembly 中的 HmacSHA256

Question

我正在尝试在 WebAssembly 中实现 JWT 令牌（仅编码），目标是拥有一个重量非常轻的 wasm 模块。作为一名 Web 开发人员，我的 C 知识是有限的。现在我已经实现了以下函数（从 JS 移植）来编码 url-safe Base64 编码器，它工作得很好。

char _keyStr[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_=";
char ret_val[200];

char* encode (char *data){
    int len = strlen(data);
    int i = 0;
    int j = 0;

    while(i<len){
        char chr1 = data[i++];
        int chr2Out = (i > len - 1)? 1:0;
        char chr2 = data[i++];
        int chr3Out = (i > len - 1)? 1:0;;
        char chr3 = data[i++];


        char enc1 = chr1 >> 2;
        char enc2 = ((chr1 & 3) << 4) | (chr2 >> 4);
        char enc3 = ((chr2 & 15) << 2) | (chr3 >> 6);
        char enc4 = chr3 & 63;

        if (chr2Out) {
            enc3 = enc4 = 64;
        } else if (chr3Out) {
            enc4 = 64;
        }

        ret_val[j++] = _keyStr[enc1];
        ret_val[j++] = _keyStr[enc2];
        ret_val[j++] = _keyStr[enc3];
        ret_val[j++] = _keyStr[enc4];

    }
    ret_val[j] = '\0';
    return ret_val;
}

我的下一个挑战是能够使用 HmacSHA256 对我的 JWT 有效负载进行签名。 下面的 JS fiddle 描述了我想用 C 完成什么。 https://jsfiddle.net/gm7boy2p/813/

我正在努力集成第 3 方代码并使其符合 emcc。 我正在寻找轻量级库或 sn-p。

示例代码或任何帮助将不胜感激。

---

更新：经过额外研究，阅读thisstackoverflow 问题和this 文章，看起来使用openssl 或任何其他外部库与WebAssembly 相去甚远。所以我现在正在寻找的是一个可以集成到现有代码中的独立 C 函数。

Answer 1

确实在使用 web-assembly 时不能使用系统库。因此，唯一的解决方案是从源代码编译它们，使其与交叉编译器（即 emscripten）已经提供的库兼容

所以对于您的问题，我找到了库 cryptopp，满足您的用例。示例here 展示了如何使用这个库。

现在如何为您的案例编译这个库？由于它带有一个make文件，你需要做的就是调用

emmake make -f GNUmakefile-cross -j8

这将生成一个 .a 文件，该文件实际上是一个 .bc 文件，可以与您希望在 Web 上运行的现有 C/C++ 程序链接。只需确保适当地包含此文件的标题即可。如果你为你的项目制作一个makefile会更好。

P.S 通过在 GNUmakefile-cross 文件的末尾添加这些行，我可以在我的系统中本地工作

cryptest.html: libcryptopp.a $(TESTOBJS)
    $(CXX) -s DISABLE_EXCEPTION_CATCHING=0 --preload-file TestData -o $@ $(strip $(CXXFLAGS)) $(TESTOBJS) ./libcryptopp.a $(LDFLAGS) $(LDLIBS)

我更改了 test.cpp 文件以包含“HMAC”的示例代码，然后从命令行调用以下行

emmake make -f GNUmakefile-cross cryptest.html -j8

输出，即 cryptest.html，在 firefox 中打开时可以完美运行。

Answer 2

我设法在 C 中创建了一个小型（类库）代码 sn-p。我检查了来自 here 的结果。

这里也显示：

SHA256 代码取自 here。在cgminer中使用。

我只是对其进行了一些修改（删除了引用等）以使其独立工作。这是总代码和测试软件。

sha2.h:

/*
 * FIPS 180-2 SHA-224/256/384/512 implementation
 * Last update: 02/02/2007
 * Issue date:  04/30/2005
 *
 * Copyright (C) 2013, Con Kolivas <kernel@kolivas.org>
 * Copyright (C) 2005, 2007 Olivier Gay <olivier.gay@a3.epfl.ch>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the project nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#ifndef SHA2_H
#define SHA2_H

#define SHA256_DIGEST_SIZE ( 256 / 8)
#define SHA256_BLOCK_SIZE  ( 512 / 8)

#define SHFR(x, n)    (x >> n)
#define ROTR(x, n)   ((x >> n) | (x << ((sizeof(x) << 3) - n)))
#define CH(x, y, z)  ((x & y) ^ (~x & z))
#define MAJ(x, y, z) ((x & y) ^ (x & z) ^ (y & z))

#define SHA256_F1(x) (ROTR(x,  2) ^ ROTR(x, 13) ^ ROTR(x, 22))
#define SHA256_F2(x) (ROTR(x,  6) ^ ROTR(x, 11) ^ ROTR(x, 25))
#define SHA256_F3(x) (ROTR(x,  7) ^ ROTR(x, 18) ^ SHFR(x,  3))
#define SHA256_F4(x) (ROTR(x, 17) ^ ROTR(x, 19) ^ SHFR(x, 10))

typedef struct {
    unsigned int tot_len;
    unsigned int len;
    unsigned char block[2 * SHA256_BLOCK_SIZE];
    unsigned int h[8];
} sha256_ctx;

extern unsigned int sha256_k[64];

void sha256_init(sha256_ctx * ctx);
void sha256_update(sha256_ctx *ctx, const unsigned char *message,
                   unsigned int len);
void sha256_final(sha256_ctx *ctx, unsigned char *digest);
void sha256(const unsigned char *message, unsigned int len,
            unsigned char *digest);

#endif /* !SHA2_H */

main.c:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "sha2.h"

#define UNPACK32(x, str)                      \
{                                             \
*((str) + 3) = (unsigned char) ((x)      );       \
*((str) + 2) = (unsigned char) ((x) >>  8);       \
*((str) + 1) = (unsigned char) ((x) >> 16);       \
*((str) + 0) = (unsigned char) ((x) >> 24);       \
}

#define PACK32(str, x)                        \
{                                             \
*(x) =   ((unsigned int) *((str) + 3)      )    \
| ((unsigned int) *((str) + 2) <<  8)    \
| ((unsigned int) *((str) + 1) << 16)    \
| ((unsigned int) *((str) + 0) << 24);   \
}

#define SHA256_SCR(i)                         \
{                                             \
w[i] =  SHA256_F4(w[i -  2]) + w[i -  7]  \
+ SHA256_F3(w[i - 15]) + w[i - 16]; \
}

unsigned int sha256_h0[8] =
{ 0x6a09e667, 0xbb67ae85, 0x3c6ef372, 0xa54ff53a,
    0x510e527f, 0x9b05688c, 0x1f83d9ab, 0x5be0cd19 };

unsigned int sha256_k[64] =
{ 0x428a2f98, 0x71374491, 0xb5c0fbcf, 0xe9b5dba5,
    0x3956c25b, 0x59f111f1, 0x923f82a4, 0xab1c5ed5,
    0xd807aa98, 0x12835b01, 0x243185be, 0x550c7dc3,
    0x72be5d74, 0x80deb1fe, 0x9bdc06a7, 0xc19bf174,
    0xe49b69c1, 0xefbe4786, 0x0fc19dc6, 0x240ca1cc,
    0x2de92c6f, 0x4a7484aa, 0x5cb0a9dc, 0x76f988da,
    0x983e5152, 0xa831c66d, 0xb00327c8, 0xbf597fc7,
    0xc6e00bf3, 0xd5a79147, 0x06ca6351, 0x14292967,
    0x27b70a85, 0x2e1b2138, 0x4d2c6dfc, 0x53380d13,
    0x650a7354, 0x766a0abb, 0x81c2c92e, 0x92722c85,
    0xa2bfe8a1, 0xa81a664b, 0xc24b8b70, 0xc76c51a3,
    0xd192e819, 0xd6990624, 0xf40e3585, 0x106aa070,
    0x19a4c116, 0x1e376c08, 0x2748774c, 0x34b0bcb5,
    0x391c0cb3, 0x4ed8aa4a, 0x5b9cca4f, 0x682e6ff3,
    0x748f82ee, 0x78a5636f, 0x84c87814, 0x8cc70208,
    0x90befffa, 0xa4506ceb, 0xbef9a3f7, 0xc67178f2 };

/* SHA-256 functions */

void sha256_transf(sha256_ctx *ctx, const unsigned char *message,
                   unsigned int block_nb)
{
    unsigned int w[64];
    unsigned int wv[8];
    unsigned int t1, t2;
    const unsigned char *sub_block;
    int i;

    int j;

    for (i = 0; i < (int)block_nb; i++) {
        sub_block = message + (i << 6);

        for (j = 0; j < 16; j++) {
            PACK32(&sub_block[j << 2], &w[j]);
        }

        for (j = 16; j < 64; j++) {
            SHA256_SCR(j);
        }

        for (j = 0; j < 8; j++) {
            wv[j] = ctx->h[j];
        }

        for (j = 0; j < 64; j++) {
            t1 = wv[7] + SHA256_F2(wv[4]) + CH(wv[4], wv[5], wv[6])
            + sha256_k[j] + w[j];
            t2 = SHA256_F1(wv[0]) + MAJ(wv[0], wv[1], wv[2]);
            wv[7] = wv[6];
            wv[6] = wv[5];
            wv[5] = wv[4];
            wv[4] = wv[3] + t1;
            wv[3] = wv[2];
            wv[2] = wv[1];
            wv[1] = wv[0];
            wv[0] = t1 + t2;
        }

        for (j = 0; j < 8; j++) {
            ctx->h[j] += wv[j];
        }
    }
}

void sha256(const unsigned char *message, unsigned int len, unsigned char *digest)
{
    sha256_ctx ctx;

    sha256_init(&ctx);
    sha256_update(&ctx, message, len);
    sha256_final(&ctx, digest);
}

void sha256_init(sha256_ctx *ctx)
{
    int i;
    for (i = 0; i < 8; i++) {
        ctx->h[i] = sha256_h0[i];
    }

    ctx->len = 0;
    ctx->tot_len = 0;
}

void sha256_update(sha256_ctx *ctx, const unsigned char *message,
                   unsigned int len)
{
    unsigned int block_nb;
    unsigned int new_len, rem_len, tmp_len;
    const unsigned char *shifted_message;

    tmp_len = SHA256_BLOCK_SIZE - ctx->len;
    rem_len = len < tmp_len ? len : tmp_len;

    memcpy(&ctx->block[ctx->len], message, rem_len);

    if (ctx->len + len < SHA256_BLOCK_SIZE) {
        ctx->len += len;
        return;
    }

    new_len = len - rem_len;
    block_nb = new_len / SHA256_BLOCK_SIZE;

    shifted_message = message + rem_len;

    sha256_transf(ctx, ctx->block, 1);
    sha256_transf(ctx, shifted_message, block_nb);

    rem_len = new_len % SHA256_BLOCK_SIZE;

    memcpy(ctx->block, &shifted_message[block_nb << 6],
           rem_len);

    ctx->len = rem_len;
    ctx->tot_len += (block_nb + 1) << 6;
}

void sha256_final(sha256_ctx *ctx, unsigned char *digest)
{
    unsigned int block_nb;
    unsigned int pm_len;
    unsigned int len_b;

    int i;

    block_nb = (1 + ((SHA256_BLOCK_SIZE - 9)
                     < (ctx->len % SHA256_BLOCK_SIZE)));

    len_b = (ctx->tot_len + ctx->len) << 3;
    pm_len = block_nb << 6;

    memset(ctx->block + ctx->len, 0, pm_len - ctx->len);
    ctx->block[ctx->len] = 0x80;
    UNPACK32(len_b, ctx->block + pm_len - 4);

    sha256_transf(ctx, ctx->block, block_nb);

    for (i = 0; i < 8; i++) {
        UNPACK32(ctx->h[i], &digest[i << 2]);
    }
}

unsigned char * HMAC_SHA256(const char * msg, const char * key)
{
    unsigned int blocksize = 64;
    unsigned char * Key0 = (unsigned char *)calloc(blocksize, sizeof(unsigned char));
    unsigned char * Key0_ipad = (unsigned char *)calloc(blocksize, sizeof(unsigned char));
    unsigned char * Key0_ipad_concat_text = (unsigned char *)calloc( (blocksize + strlen(msg)), sizeof(unsigned char));
    unsigned char * Key0_ipad_concat_text_digest = (unsigned char *)calloc( blocksize, sizeof(unsigned char));
    unsigned char * Key0_opad = (unsigned char *)calloc(blocksize, sizeof(unsigned char));
    unsigned char * Key0_opad_concat_prev = (unsigned char *)calloc(blocksize + 32, sizeof(unsigned char));

    unsigned char * HMAC_SHA256 = (unsigned char *)malloc(32 * sizeof(unsigned char));

    if (strlen(key) < blocksize) {
        for (int i = 0; i < blocksize; i++) {
            if (i < strlen(key)) Key0[i] = key[i];
            else Key0[i] = 0x00;
        }
    }
    else if (strlen(key) > blocksize) {
        sha256(key, strlen(key), Key0);
        for (unsigned char i = strlen(key); i < blocksize; i++) {
            Key0[i] = 0x00;
        }
    }

    for (int i = 0; i < blocksize; i++) {
        Key0_ipad[i] = Key0[i] ^ 0x36;
    }
    for (int i = 0; i < blocksize; i++) {
        Key0_ipad_concat_text[i] = Key0_ipad[i];
    }
    for (int i = blocksize; i < blocksize + strlen(msg); i++) {
        Key0_ipad_concat_text[i] = msg[i - blocksize];
    }

    sha256(Key0_ipad_concat_text, blocksize + (unsigned int)strlen(msg), Key0_ipad_concat_text_digest);

    for (int i = 0; i < blocksize; i++) {
        Key0_opad[i] = Key0[i] ^ 0x5C;
    }

    for (int i = 0; i < blocksize; i++) {
        Key0_opad_concat_prev[i] = Key0_opad[i];
    }
    for (int i = blocksize; i < blocksize + 32; i++) {
        Key0_opad_concat_prev[i] = Key0_ipad_concat_text_digest[i - blocksize];
    }

    sha256(Key0_opad_concat_prev, blocksize + 32, HMAC_SHA256);
    return HMAC_SHA256;
}


int main()
{
    unsigned char * result;

    result = HMAC_SHA256("Sample #1", "MyKey");

    unsigned char arr[32] = { 0 };
    memcpy(arr, result, 32);

    for(int i = 0; i < 32; i++) {
        printf("%#02x, ", arr[i]);
    }
    return 0;
}

以下是示例运行的结果：

编辑：

可以在here 找到有关 HMAC_SHA256 函数的信息。我写的只是为了演示目的。可以进行相应的修改。

编辑2：

我添加了 Base64 格式的代码。我使用了在维基百科上找到的信息。样本测试运行适用于 OP 的输入和输出。结果如图：

更新了 main.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>

#include "sha2.h"

#define HMAC_SHA256_FAIL_STRING "HMAC_SHA256 has failed." // fprintf(stderr, "%s\n", strerror(errno));

#define UNPACK32(x, str)                      \
{                                             \
*((str) + 3) = (unsigned char) ((x)      );       \
*((str) + 2) = (unsigned char) ((x) >>  8);       \
*((str) + 1) = (unsigned char) ((x) >> 16);       \
*((str) + 0) = (unsigned char) ((x) >> 24);       \
}

#define PACK32(str, x)                        \
{                                             \
*(x) =   ((unsigned int) *((str) + 3)      )    \
| ((unsigned int) *((str) + 2) <<  8)    \
| ((unsigned int) *((str) + 1) << 16)    \
| ((unsigned int) *((str) + 0) << 24);   \
}

#define SHA256_SCR(i)                         \
{                                             \
w[i] =  SHA256_F4(w[i -  2]) + w[i -  7]  \
+ SHA256_F3(w[i - 15]) + w[i - 16]; \
}

char Base64_Table[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

unsigned int sha256_h0[8] =
{ 0x6a09e667, 0xbb67ae85, 0x3c6ef372, 0xa54ff53a,
    0x510e527f, 0x9b05688c, 0x1f83d9ab, 0x5be0cd19 };

unsigned int sha256_k[64] =
{ 0x428a2f98, 0x71374491, 0xb5c0fbcf, 0xe9b5dba5,
    0x3956c25b, 0x59f111f1, 0x923f82a4, 0xab1c5ed5,
    0xd807aa98, 0x12835b01, 0x243185be, 0x550c7dc3,
    0x72be5d74, 0x80deb1fe, 0x9bdc06a7, 0xc19bf174,
    0xe49b69c1, 0xefbe4786, 0x0fc19dc6, 0x240ca1cc,
    0x2de92c6f, 0x4a7484aa, 0x5cb0a9dc, 0x76f988da,
    0x983e5152, 0xa831c66d, 0xb00327c8, 0xbf597fc7,
    0xc6e00bf3, 0xd5a79147, 0x06ca6351, 0x14292967,
    0x27b70a85, 0x2e1b2138, 0x4d2c6dfc, 0x53380d13,
    0x650a7354, 0x766a0abb, 0x81c2c92e, 0x92722c85,
    0xa2bfe8a1, 0xa81a664b, 0xc24b8b70, 0xc76c51a3,
    0xd192e819, 0xd6990624, 0xf40e3585, 0x106aa070,
    0x19a4c116, 0x1e376c08, 0x2748774c, 0x34b0bcb5,
    0x391c0cb3, 0x4ed8aa4a, 0x5b9cca4f, 0x682e6ff3,
    0x748f82ee, 0x78a5636f, 0x84c87814, 0x8cc70208,
    0x90befffa, 0xa4506ceb, 0xbef9a3f7, 0xc67178f2 };

/* SHA-256 functions */

void sha256_transf(sha256_ctx *ctx, const unsigned char *message,
                   unsigned int block_nb)
{
    unsigned int w[64];
    unsigned int wv[8];
    unsigned int t1, t2;
    const unsigned char *sub_block;
    int i;

    int j;

    for (i = 0; i < (int)block_nb; i++) {
        sub_block = message + (i << 6);

        for (j = 0; j < 16; j++) {
            PACK32(&sub_block[j << 2], &w[j]);
        }

        for (j = 16; j < 64; j++) {
            SHA256_SCR(j);
        }

        for (j = 0; j < 8; j++) {
            wv[j] = ctx->h[j];
        }

        for (j = 0; j < 64; j++) {
            t1 = wv[7] + SHA256_F2(wv[4]) + CH(wv[4], wv[5], wv[6])
            + sha256_k[j] + w[j];
            t2 = SHA256_F1(wv[0]) + MAJ(wv[0], wv[1], wv[2]);
            wv[7] = wv[6];
            wv[6] = wv[5];
            wv[5] = wv[4];
            wv[4] = wv[3] + t1;
            wv[3] = wv[2];
            wv[2] = wv[1];
            wv[1] = wv[0];
            wv[0] = t1 + t2;
        }

        for (j = 0; j < 8; j++) {
            ctx->h[j] += wv[j];
        }
    }
}

void sha256(const unsigned char *message, unsigned int len, unsigned char *digest)
{
    sha256_ctx ctx;

    sha256_init(&ctx);
    sha256_update(&ctx, message, len);
    sha256_final(&ctx, digest);
}

void sha256_init(sha256_ctx *ctx)
{
    int i;
    for (i = 0; i < 8; i++) {
        ctx->h[i] = sha256_h0[i];
    }

    ctx->len = 0;
    ctx->tot_len = 0;
}

void sha256_update(sha256_ctx *ctx, const unsigned char *message,
                   unsigned int len)
{
    unsigned int block_nb;
    unsigned int new_len, rem_len, tmp_len;
    const unsigned char *shifted_message;

    tmp_len = SHA256_BLOCK_SIZE - ctx->len;
    rem_len = len < tmp_len ? len : tmp_len;

    memcpy(&ctx->block[ctx->len], message, rem_len);

    if (ctx->len + len < SHA256_BLOCK_SIZE) {
        ctx->len += len;
        return;
    }

    new_len = len - rem_len;
    block_nb = new_len / SHA256_BLOCK_SIZE;

    shifted_message = message + rem_len;

    sha256_transf(ctx, ctx->block, 1);
    sha256_transf(ctx, shifted_message, block_nb);

    rem_len = new_len % SHA256_BLOCK_SIZE;

    memcpy(ctx->block, &shifted_message[block_nb << 6],
           rem_len);

    ctx->len = rem_len;
    ctx->tot_len += (block_nb + 1) << 6;
}

void sha256_final(sha256_ctx *ctx, unsigned char *digest)
{
    unsigned int block_nb;
    unsigned int pm_len;
    unsigned int len_b;

    int i;

    block_nb = (1 + ((SHA256_BLOCK_SIZE - 9)
                     < (ctx->len % SHA256_BLOCK_SIZE)));

    len_b = (ctx->tot_len + ctx->len) << 3;
    pm_len = block_nb << 6;

    memset(ctx->block + ctx->len, 0, pm_len - ctx->len);
    ctx->block[ctx->len] = 0x80;
    UNPACK32(len_b, ctx->block + pm_len - 4);

    sha256_transf(ctx, ctx->block, block_nb);

    for (i = 0; i < 8; i++) {
        UNPACK32(ctx->h[i], &digest[i << 2]);
    }
}

char * HMAC_SHA256(char * msg, char * key)
{
    size_t blocksize;

    blocksize = 64;
    char * Key0 = (char *)calloc(blocksize, sizeof(char));
    if (Key0 == NULL) {
        return HMAC_SHA256_FAIL_STRING;
    }

    blocksize = 64;
    char * Key0_ipad = (char *)calloc(blocksize, sizeof(char));
    if (Key0_ipad == NULL) {
        free(Key0);
        return HMAC_SHA256_FAIL_STRING;
    }

    blocksize = 64 + strlen(msg);
    char * Key0_ipad_concat_text = (char *)calloc( blocksize, sizeof(char));
    if (Key0_ipad_concat_text == NULL) {
        free(Key0);
        free(Key0_ipad);
        return HMAC_SHA256_FAIL_STRING;
    }

    blocksize = 64;
    char * Key0_ipad_concat_text_digest = (char *)calloc( blocksize, sizeof(char));
    if (Key0_ipad_concat_text_digest == NULL) {
        free(Key0);
        free(Key0_ipad);
        free(Key0_ipad_concat_text);
        return HMAC_SHA256_FAIL_STRING;
    }

    blocksize = 64;
    char * Key0_opad = (char *)calloc(blocksize, sizeof(char));
    if (Key0_opad == NULL) {
        free(Key0);
        free(Key0_ipad);
        free(Key0_ipad_concat_text);
        free(Key0_ipad_concat_text_digest);
        return HMAC_SHA256_FAIL_STRING;
    }

    blocksize = 64 + 32;
    char * Key0_opad_concat_prev = (char *)calloc(blocksize + 32, sizeof(char));
    if (Key0_opad_concat_prev == NULL) {
        free(Key0);
        free(Key0_ipad);
        free(Key0_ipad_concat_text);
        free(Key0_ipad_concat_text_digest);
        free(Key0_opad);
        return HMAC_SHA256_FAIL_STRING;
    }

    blocksize = 64;
    char * HMAC_SHA256 = (char *)malloc(blocksize/2 * sizeof(char));
    if (HMAC_SHA256 == NULL) {
        free(Key0);
        free(Key0_ipad);
        free(Key0_ipad_concat_text);
        free(Key0_ipad_concat_text_digest);
        free(Key0_opad);
        free(Key0_opad_concat_prev);
        return HMAC_SHA256_FAIL_STRING;
    }

    if (strlen(key) < blocksize) {
        char * tmp = key;
        char * tmp2 = Key0;
        for (int i = 0; i < blocksize; i++) {
            if (i < strlen(key)) *tmp2++ = *tmp++;
            else *tmp2++ = 0x00;
        }
    }
    else if (strlen(key) > blocksize) {
        sha256((unsigned char *)key, strlen(key), (unsigned char *)Key0);
        for (unsigned char i = strlen(key); i < blocksize; i++) {
            Key0[i] = 0x00;
        }
    }

    for (int i = 0; i < blocksize; i++) {
        Key0_ipad[i] = Key0[i] ^ 0x36;
    }
    for (int i = 0; i < blocksize; i++) {
        Key0_ipad_concat_text[i] = Key0_ipad[i];
    }
    for (int i = blocksize; i < blocksize + strlen(msg); i++) {
        Key0_ipad_concat_text[i] = msg[i - blocksize];
    }

    sha256((unsigned char *)Key0_ipad_concat_text, blocksize + (unsigned int)strlen(msg), (unsigned char *)Key0_ipad_concat_text_digest);

    for (int i = 0; i < blocksize; i++) {
        Key0_opad[i] = Key0[i] ^ 0x5C;
    }

    for (int i = 0; i < blocksize; i++) {
        Key0_opad_concat_prev[i] = Key0_opad[i];
    }
    for (int i = blocksize; i < blocksize + 32; i++) {
        Key0_opad_concat_prev[i] = Key0_ipad_concat_text_digest[i - blocksize];
    }

    sha256((unsigned char *)Key0_opad_concat_prev, blocksize + 32, (unsigned char *)HMAC_SHA256);

    free(Key0);
    free(Key0_ipad);
    free(Key0_ipad_concat_text);
    free(Key0_ipad_concat_text_digest);
    free(Key0_opad);
    free(Key0_opad_concat_prev);
    return HMAC_SHA256;
}

char * Base64_Stringify(char * hash, size_t length)
{
    size_t no_op = 0;
    size_t Base64_size;
    char * Base64;
    unsigned long tmp = length;
    if (tmp % 3 == 0) {
        Base64_size = 4 * tmp / 3;
        Base64 = (char *)calloc(Base64_size + 1, sizeof(char));
    }
    else if (tmp % 3 == 1) {
        tmp += 2;
        Base64_size = 4 * tmp / 3;
        Base64 = (char *)calloc(Base64_size + 1, sizeof(char));
        Base64[Base64_size - 1] = '=';
        Base64[Base64_size - 2] = '=';
        no_op = 2;
    }
    else if (tmp % 3 == 2) {
        tmp += 1;
        Base64_size = 4 * tmp / 3;
        Base64 = (char *)calloc(Base64_size + 1, sizeof(char));
        Base64[Base64_size - 1] = '=';
        no_op = 1;
    }

    unsigned int b64_case = 0;
    size_t j = 0;
    for (int i = 0; i < Base64_size - no_op; i++) {
        switch (b64_case) {
            case 0:
            {
                Base64[i] = Base64_Table[(hash[j] & 0xFC) >> 2];
                j++;
                b64_case = 1;
            }
                break;
            case 1:
            {
                Base64[i] = Base64_Table[((hash[j-1] & 0x03) << 4) | ((hash[j] & 0xF0) >> 4)];
                b64_case = 2;
            }
                break;
            case 2:
            {
                Base64[i] = Base64_Table[((hash[j] & 0x0F) << 2) | ((hash[j+1] & 0xC0) >> 6)];
                j++;
                b64_case = 3;
            }
                break;
            case 3:
            {
                Base64[i] = Base64_Table[(hash[j] & 0x3F)];
                j++;
                b64_case = 0;
            }
                break;

            default:
                break;
        }
    }

    return Base64;
}


int main()
{
    char * HMAC_SHA256_result;
    char * Base64_Stringify_result;

    HMAC_SHA256_result = HMAC_SHA256("test", "secret");
    Base64_Stringify_result = Base64_Stringify(HMAC_SHA256_result, 32);

    unsigned char arr[32] = { 0 };
    memcpy(arr, HMAC_SHA256_result, 32);

    for(int i = 0; i < 32; i++) {
        printf("%#02x, ", arr[i]);
    }
    printf("\n\n");

    for(int i = 0; i < strlen(Base64_Stringify_result); i++) {
        printf("%c", Base64_Stringify_result[i]);
    }
    printf("\n\n");
    return 0;
}

我将保留旧的 main.c 以供参考。您还可以修改更新后的 main.c 函数，例如calloc失败时的错误码...

Answer 3

我创建了一个简单示例，说明如何使用 libgcrypt 库创建 hmac。您只需将它安装在您的系统中，然后他们使用-lgcrypt 标志编译程序以链接库。

当您询问独立函数时，我创建了一个函数，您可以使用键和消息调用该函数，该函数返回带有 base64 编码结果的字符串，这正是您在 JSFiddle 中所要求的。

#include <stdio.h>
#include <string.h>
#include <gcrypt.h>
#include <stdint.h>


static char encoding_table[] = {'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H',
                                'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P',
                                'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X',
                                'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f',
                                'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n',
                                'o', 'p', 'q', 'r', 's', 't', 'u', 'v',
                                'w', 'x', 'y', 'z', '0', '1', '2', '3',
                                '4', '5', '6', '7', '8', '9', '+', '/'};
static char *decoding_table = NULL;
static int mod_table[] = {0, 2, 1};


char *base64_encode(const unsigned char *data,
                    size_t input_length,
                    size_t *output_length) {

    *output_length = 4 * ((input_length + 2) / 3);

    char *encoded_data = calloc(1,*output_length+1);
    if (encoded_data == NULL) return NULL;

    for (int i = 0, j = 0; i < input_length;) {

        uint32_t octet_a = i < input_length ? (unsigned char)data[i++] : 0;
        uint32_t octet_b = i < input_length ? (unsigned char)data[i++] : 0;
        uint32_t octet_c = i < input_length ? (unsigned char)data[i++] : 0;

        uint32_t triple = (octet_a << 0x10) + (octet_b << 0x08) + octet_c;

        encoded_data[j++] = encoding_table[(triple >> 3 * 6) & 0x3F];
        encoded_data[j++] = encoding_table[(triple >> 2 * 6) & 0x3F];
        encoded_data[j++] = encoding_table[(triple >> 1 * 6) & 0x3F];
        encoded_data[j++] = encoding_table[(triple >> 0 * 6) & 0x3F];
    }

    for (int i = 0; i < mod_table[input_length % 3]; i++)
        encoded_data[*output_length - 1 - i] = '=';

    return encoded_data;
}

//don't forget to free the return pointer!
char* hmacSHA256(gcry_mac_hd_t hd, const char* key, size_t key_size, const char* msg, size_t msg_size) {
    unsigned char output[32];
    size_t outputSize = 32;
    gcry_mac_reset(hd);
    gcry_mac_setkey(hd,key,strlen(key));
    gcry_mac_write(hd,msg,strlen(msg));
    gcry_mac_read(hd,output,&outputSize);
    return base64_encode(output,outputSize,&outputSize);
}

int main() {
    const char* const key = "secret";
    const char* const msg = "test";
    //hmacsha256 returns 256 bits, meaning 32 bytes
    unsigned char output[32];
    size_t outputSize = 32;
    gcry_mac_hd_t hd;
    gcry_mac_open(&hd,GCRY_MAC_HMAC_SHA256,0,NULL);

    char* tmp = hmacSHA256(hd,key,strlen(key),msg,strlen(msg));
    printf("HMAC-SHA256: '%s'\n",tmp);
    free(tmp);

    tmp = hmacSHA256(hd,"secrett",7,msg,strlen(msg));
    printf("HMAC-SHA256: '%s'\n",tmp);
    free(tmp);

    gcry_mac_close(hd);
    return 0;
}

重要提示：

-不要忘记释放 hmacSHA256 函数的返回值并在完成哈希后调用 gcry_mac_close。

-我在函数的参数中包含了键的大小和消息的大小，因为这样您就可以处理二进制数据的 HMAC 以及 ASCII/UTF-8 编码的字符串。如果您不打算使用二进制数据，请随意从参数中删除大小并使用 strlen 计算函数内部的大小，就像我在调用函数时在 main 中所做的那样。

-我没有将 gcry_mac_hd_t 的创建包装在函数中，因为重用同一个处理程序并在每次需要重用时重置它然后在每次需要时创建一个新处理程序会更有效.如果你在同一个执行中多次调用这个函数，这个优化会更加明显！