【安全算法之SHA256】SHA256摘要运算C语言源码实现-sha算法的摘要长度为

【安全算法之SHA256】SHA256摘要运算的C语言源码实现

概述头文件定义 C语言版本的实现源码测试用例 github仓库更多参考链接

概述

大家都知道摘要算法在安全领域，也是一个特别重要的存在，而SHA256是其中最常见的一种摘要算法，它的特点就是计算复杂度较低，不等长的数据原文输入，可以得出等长的摘要值，这个值是固定为32字节。正是由于这种特殊性，很多重要的数据完整性校验领域，都可以看到SHA256的影子。在一些安全认证中，摘要运算的算法等级至少是大于等于SHA256的安全级别，足以证明SHA256的重要性。

今天给大家带来SHA256的C源码版本实现，欢迎大家深入学习和讨论。

头文件定义

头文件定义如下，主要定义了SHA256的上下文结构体，以及导出的三个API：

复制 #ifndef __SHA256_H__ #define __SHA256_H__ #include #define SHA256_DIGEST_LEN 32 // SHA256 outputs a 32 byte digest typedef uint8_t BYTE; // 8-bit byte typedef uint32_t WORD; // 32-bit word, change to “long” for 16-bit machines typedef struct _sha256_ctx_t { uint8_t data[64]; uint32_t data_len; unsigned long long bit_len; uint32_t state[8]; } sha256_ctx_t; void crypto_sha256_init(sha256_ctx_t *ctx); void crypto_sha256_update(sha256_ctx_t *ctx, const uint8_t *data, uint32_t len); void crypto_sha256_final(sha256_ctx_t *ctx, uint8_t *digest); #endif // __SHA256_H__

C语言版本的实现源码

下面是SHA256的C语言版本实现，主要也是围绕导出的3个API：

复制 #include #include #include “sha256.h” #define ROTLEFT(a,b) (((a) << (b)) | ((a) >> (32-(b)))) #define ROTRIGHT(a,b) (((a) >> (b)) | ((a) << (32-(b)))) #define CH(x,y,z) (((x) & (y)) ^ (~(x) & (z))) #define MAJ(x,y,z) (((x) & (y)) ^ ((x) & (z)) ^ ((y) & (z))) #define EP0(x) (ROTRIGHT(x,2) ^ ROTRIGHT(x,13) ^ ROTRIGHT(x,22)) #define EP1(x) (ROTRIGHT(x,6) ^ ROTRIGHT(x,11) ^ ROTRIGHT(x,25)) #define SIG0(x) (ROTRIGHT(x,7) ^ ROTRIGHT(x,18) ^ ((x) >> 3)) #define SIG1(x) (ROTRIGHT(x,17) ^ ROTRIGHT(x,19) ^ ((x) >> 10)) static const uint32_t 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, }; static void local_sha256_transform(sha256_ctx_t *ctx, const uint8_t *data) { uint32_t a, b, c, d, e, f, g, h, i, j, t1, t2, m[64]; for (i = 0, j = 0; i < 16; ++i, j += 4) { m[i] = (data[j] << 24) | (data[j + 1] << 16) | (data[j + 2] << 8) | (data[j + 3]); } for ( ; i < 64; ++i) { m[i] = SIG1(m[i – 2]) + m[i – 7] + SIG0(m[i – 15]) + m[i – 16]; } a = ctx->state[0]; b = ctx->state[1]; c = ctx->state[2]; d = ctx->state[3]; e = ctx->state[4]; f = ctx->state[5]; g = ctx->state[6]; h = ctx->state[7]; for (i = 0; i < 64; ++i) { t1 = h + EP1(e) + CH(e,f,g) + k[i] + m[i]; t2 = EP0(a) + MAJ(a,b,c); h = g; g = f; f = e; e = d + t1; d = c; c = b; b = a; a = t1 + t2; } ctx->state[0] += a; ctx->state[1] += b; ctx->state[2] += c; ctx->state[3] += d; ctx->state[4] += e; ctx->state[5] += f; ctx->state[6] += g; ctx->state[7] += h; } void crypto_sha256_init(sha256_ctx_t *ctx) { ctx->data_len = 0; ctx->bit_len = 0; ctx->state[0] = 0x6a09e667; ctx->state[1] = 0xbb67ae85; ctx->state[2] = 0x3c6ef372; ctx->state[3] = 0xa54ff53a; ctx->state[4] = 0x510e527f; ctx->state[5] = 0x9b05688c; ctx->state[6] = 0x1f83d9ab; ctx->state[7] = 0x5be0cd19; } void crypto_sha256_update(sha256_ctx_t *ctx, const uint8_t *data, uint32_t len) { uint32_t i; for (i = 0; i < len; ++i) { ctx->data[ctx->data_len] = data[i]; ctx->data_len++; if (ctx->data_len == 64) { local_sha256_transform(ctx, ctx->data); ctx->bit_len += 512; ctx->data_len = 0; } } } void crypto_sha256_final(sha256_ctx_t *ctx, uint8_t *digest) { uint32_t i; i = ctx->data_len; // Pad whatever data is left in the buffer. if (ctx->data_len < 56) { ctx->data[i++] = 0x80; while (i < 56) { ctx->data[i++] = 0x00; } } else { ctx->data[i++] = 0x80; while (i < 64) { ctx->data[i++] = 0x00; } local_sha256_transform(ctx, ctx->data); memset(ctx->data, 0, 56); } // Append to the padding the total messages length in bits and transform. ctx->bit_len += ctx->data_len * 8; ctx->data[63] = ctx->bit_len; ctx->data[62] = ctx->bit_len >> 8; ctx->data[61] = ctx->bit_len >> 16; ctx->data[60] = ctx->bit_len >> 24; ctx->data[59] = ctx->bit_len >> 32; ctx->data[58] = ctx->bit_len >> 40; ctx->data[57] = ctx->bit_len >> 48; ctx->data[56] = ctx->bit_len >> 56; local_sha256_transform(ctx, ctx->data); // Since this implementation uses little endian byte ordering and SHA uses big endian, // reverse all the bytes when copying the final state to the output digest. for (i = 0; i < 4; ++i) { digest[i] = (ctx->state[0] >> (24 – i * 8)) & 0x000000ff; digest[i + 4] = (ctx->state[1] >> (24 – i * 8)) & 0x000000ff; digest[i + 8] = (ctx->state[2] >> (24 – i * 8)) & 0x000000ff; digest[i + 12] = (ctx->state[3] >> (24 – i * 8)) & 0x000000ff; digest[i + 16] = (ctx->state[4] >> (24 – i * 8)) & 0x000000ff; digest[i + 20] = (ctx->state[5] >> (24 – i * 8)) & 0x000000ff; digest[i + 24] = (ctx->state[6] >> (24 – i * 8)) & 0x000000ff; digest[i + 28] = (ctx->state[7] >> (24 – i * 8)) & 0x000000ff; } }

测试用例

针对SHA256导出的三个接口，我编写了以下测试用例：

复制 #include #include #include “sha256.h” #include “convert.h” int log_hexdump(const char *title, const unsigned char *data, int len) { char str[160], octet[10]; int ofs, i, k, d; const unsigned char *buf = (const unsigned char *)data; const char dimm[] = “+——————————————————————————+”; printf(“%s (%d bytes):\r\n”, title, len); printf(“%s\r\n”, dimm); printf(“| Offset : 00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F 0123456789ABCDEF |\r\n”); printf(“%s\r\n”, dimm); for (ofs = 0; ofs < (int)len; ofs += 16) { d = snprintf( str, sizeof(str), “| %08X: “, ofs ); for (i = 0; i < 16; i++) { if ((i + ofs) < (int)len) { snprintf( octet, sizeof(octet), “%02X “, buf[ofs + i] ); } else { snprintf( octet, sizeof(octet), ” ” ); } d += snprintf( &str[d], sizeof(str) – d, “%s”, octet ); } d += snprintf( &str[d], sizeof(str) – d, ” ” ); k = d; for (i = 0; i < 16; i++) { if ((i + ofs) < (int)len) { str[k++] = (0x20 <= (buf[ofs + i]) && (buf[ofs + i]) <= 0x7E) ? buf[ofs + i] : .; } else { str[k++] = ; } } str[k] = \0; printf(“%s |\r\n”, str); } printf(“%s\r\n”, dimm); return 0; } int main(int argc, const char *argv[]) { const char *data = “C1D0F8FB4958670DBA40AB1F3752EF0D”; const char *digest_exp_str = “97B7437DF061F15182974B18E62B3D8AAFE333DCBDD2074CB8D4916509B4AD23”; uint8_t digest_calc[SHA256_DIGEST_LEN]; uint8_t digest_exp_hex[SHA256_DIGEST_LEN]; sha256_ctx_t ctx; const char *p_calc = data; uint8_t data_bytes[128]; uint16_t len_bytes; char data_str[128]; if (argc > 1) { p_calc = argv[1]; } utils_hex_string_2_bytes(data, data_bytes, &len_bytes); log_hexdump(“data_bytes”, data_bytes, len_bytes); utils_bytes_2_hex_string(data_bytes, len_bytes, data_str); printf(“data_str: %s\n”, data_str); if (!strcmp(data, data_str)) { printf(“hex string – bytes convert OK\n”); } else { printf(“hex string – bytes convert FAIL\n”); } crypto_sha256_init(&ctx); crypto_sha256_update(&ctx, (uint8_t *)p_calc, strlen(p_calc)); crypto_sha256_final(&ctx, digest_calc); utils_hex_string_2_bytes(digest_exp_str, digest_exp_hex, &len_bytes); if (len_bytes == sizeof(digest_calc) && !memcmp(digest_calc, digest_exp_hex, sizeof(digest_calc))) { printf(“SHA256 digest test OK\n”); log_hexdump(“digest_calc”, digest_calc, sizeof(digest_calc)); } else { log_hexdump(“digest_calc”, digest_calc, sizeof(digest_calc)); log_hexdump(“digest_exp”, digest_exp_hex, sizeof(digest_exp_hex)); printf(“SHA256 digest test FAIL\n”); } return 0; }

测试用例比较简单，就是对字符串C1D0F8FB4958670DBA40AB1F3752EF0D进行SHA1运算，期望的摘要结果的hexstring是97B7437DF061F15182974B18E62B3D8AAFE333DCBDD2074CB8D4916509B4AD23

，这个期望值是用算法工具算出来的。

先用API接口算出摘要值，再与期望值比较，这里有个hexstringtobyte的转换，如果比较一致则表示API计算OK；反之，接口计算失败。

同时，也欢迎大家设计提供更多的测试案例代码。

github仓库

以上代码和测试用例，及编译运行等，可以参考我的github仓库，有详细的流程介绍，欢迎大家交流讨论。如果有帮助到你的话，记得帮忙点亮一颗星哦。