我试图在webassembly中实现jwt令牌（仅编码），目标是拥有一个非常轻量级的wasm模块。作为一个web开发人员，我的c知识是有限的。目前，我已经实现了以下函数（从js移植）来编码url-safe-base64编码器，它工作得非常好。
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用hmacsha256签署我的jwt负载。
下面的js fiddle描述了我想用c实现的功能。
https://jsfiddle.net/gm7boy2p/813/
我正在努力集成第三方代码并将其与emcc兼容。
我在找一个轻量级的库或一个片段。
示例代码或任何帮助将不胜感激。
更新：经过额外的研究，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并不是一件小事。因此，我现在寻找的是一个独立的C函数，我可以集成到现有代码中。
最佳答案
我设法在C语言中创建了一个小的（带库的）代码片段。我检查了here的结果。
此处还显示：
SHA256代码取自here。用于cgminer。
我只是修改了一点（删除了引用等），使其独立工作。这是总的代码和测试软件。
沙2.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 <[email protected]>
* Copyright (C) 2005, 2007 Olivier Gay <[email protected]>
* 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 */
主要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：
有关hmac_sha256函数的信息可以找到here。我写的那个只是为了演示。我们可以相应地修改它。
编辑2：
我添加了base64格式的代码。我用了维基百科上的信息。示例测试运行对op的输入和输出有效。结果如下：
更新的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;
}
我把旧的main.c留作参考。您还可以修改更新的main.c函数，例如calloc失败时的错误代码…
关于c - 使用Emscripten编译的WebAssembly中的HmacSHA256，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/49776226/