bishe-STM32/Hardware/aes_fixed.c

/*
 * 标准AES-128-CBC实现 - 与OpenSSL完全兼容
 * 基于FIPS-197标准
 */

#include "aes.h"
#include <string.h>

// S-box
static const uint8_t sbox[256] = {
    0x63, 0x7c, 0x77, 0x7b, 0xf2, 0x6b, 0x6f, 0xc5, 0x30, 0x01, 0x67, 0x2b, 0xfe, 0xd7, 0xab, 0x76,
    0xca, 0x82, 0xc9, 0x7d, 0xfa, 0x59, 0x47, 0xf0, 0xad, 0xd4, 0xa2, 0xaf, 0x9c, 0xa4, 0x72, 0xc0,
    0xb7, 0xfd, 0x93, 0x26, 0x36, 0x3f, 0xf7, 0xcc, 0x34, 0xa5, 0xe5, 0xf1, 0x71, 0xd8, 0x31, 0x15,
    0x04, 0xc7, 0x23, 0xc3, 0x18, 0x96, 0x05, 0x9a, 0x07, 0x12, 0x80, 0xe2, 0xeb, 0x27, 0xb2, 0x75,
    0x09, 0x83, 0x2c, 0x1a, 0x1b, 0x6e, 0x5a, 0xa0, 0x52, 0x3b, 0xd6, 0xb3, 0x29, 0xe3, 0x2f, 0x84,
    0x53, 0xd1, 0x00, 0xed, 0x20, 0xfc, 0xb1, 0x5b, 0x6a, 0xcb, 0xbe, 0x39, 0x4a, 0x4c, 0x58, 0xcf,
    0xd0, 0xef, 0xaa, 0xfb, 0x43, 0x4d, 0x33, 0x85, 0x45, 0xf9, 0x02, 0x7f, 0x50, 0x3c, 0x9f, 0xa8,
    0x51, 0xa3, 0x40, 0x8f, 0x92, 0x9d, 0x38, 0xf5, 0xbc, 0xb6, 0xda, 0x21, 0x10, 0xff, 0xf3, 0xd2,
    0xcd, 0x0c, 0x13, 0xec, 0x5f, 0x97, 0x44, 0x17, 0xc4, 0xa7, 0x7e, 0x3d, 0x64, 0x5d, 0x19, 0x73,
    0x60, 0x81, 0x4f, 0xdc, 0x22, 0x2a, 0x90, 0x88, 0x46, 0xee, 0xb8, 0x14, 0xde, 0x5e, 0x0b, 0xdb,
    0xe0, 0x32, 0x3a, 0x0a, 0x49, 0x06, 0x24, 0x5c, 0xc2, 0xd3, 0xac, 0x62, 0x91, 0x95, 0xe4, 0x79,
    0xe7, 0xc8, 0x37, 0x6d, 0x8d, 0xd5, 0x4e, 0xa9, 0x6c, 0x56, 0xf4, 0xea, 0x65, 0x7a, 0xae, 0x08,
    0xba, 0x78, 0x25, 0x2e, 0x1c, 0xa6, 0xb4, 0xc6, 0xe8, 0xdd, 0x74, 0x1f, 0x4b, 0xbd, 0x8b, 0x8a,
    0x70, 0x3e, 0xb5, 0x66, 0x48, 0x03, 0xf6, 0x0e, 0x61, 0x35, 0x57, 0xb9, 0x86, 0xc1, 0x1d, 0x9e,
    0xe1, 0xf8, 0x98, 0x11, 0x69, 0xd9, 0x8e, 0x94, 0x9b, 0x1e, 0x87, 0xe9, 0xce, 0x55, 0x28, 0xdf,
    0x8c, 0xa1, 0x89, 0x0d, 0xbf, 0xe6, 0x42, 0x68, 0x41, 0x99, 0x2d, 0x0f, 0xb0, 0x54, 0xbb, 0x16
};

// Rcon
static const uint8_t Rcon[11] = {
    0x8d, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36
};

#define getSBoxValue(num) (sbox[(num)])

// 密钥扩展
static void KeyExpansion(uint8_t* RoundKey, const uint8_t* Key)
{
    unsigned i, j, k;
    uint8_t tempa[4];

    // 前4个轮密钥直接复制
    for (i = 0; i < 4; ++i) {
        RoundKey[(i * 4) + 0] = Key[(i * 4) + 0];
        RoundKey[(i * 4) + 1] = Key[(i * 4) + 1];
        RoundKey[(i * 4) + 2] = Key[(i * 4) + 2];
        RoundKey[(i * 4) + 3] = Key[(i * 4) + 3];
    }

    // 生成其余轮密钥
    for (i = 4; i < 44; ++i) {
        k = (i - 1) * 4;
        tempa[0] = RoundKey[k + 0];
        tempa[1] = RoundKey[k + 1];
        tempa[2] = RoundKey[k + 2];
        tempa[3] = RoundKey[k + 3];

        if (i % 4 == 0) {
            // RotWord
            const uint8_t u8tmp = tempa[0];
            tempa[0] = tempa[1];
            tempa[1] = tempa[2];
            tempa[2] = tempa[3];
            tempa[3] = u8tmp;

            // SubWord
            tempa[0] = getSBoxValue(tempa[0]);
            tempa[1] = getSBoxValue(tempa[1]);
            tempa[2] = getSBoxValue(tempa[2]);
            tempa[3] = getSBoxValue(tempa[3]);

            tempa[0] = tempa[0] ^ Rcon[i / 4];
        }

        j = i * 4;
        k = (i - 4) * 4;
        RoundKey[j + 0] = RoundKey[k + 0] ^ tempa[0];
        RoundKey[j + 1] = RoundKey[k + 1] ^ tempa[1];
        RoundKey[j + 2] = RoundKey[k + 2] ^ tempa[2];
        RoundKey[j + 3] = RoundKey[k + 3] ^ tempa[3];
    }
}

// AddRoundKey
static void AddRoundKey(uint8_t round, uint8_t* state, const uint8_t* RoundKey)
{
    uint8_t i, j;
    for (i = 0; i < 4; ++i) {
        for (j = 0; j < 4; ++j) {
            state[i * 4 + j] ^= RoundKey[(round * 16) + (i * 4 + j)];
        }
    }
}

// SubBytes
static void SubBytes(uint8_t* state)
{
    uint8_t i;
    for (i = 0; i < 16; ++i) {
        state[i] = getSBoxValue(state[i]);
    }
}

// ShiftRows
static void ShiftRows(uint8_t* state)
{
    uint8_t temp;

    // 第二行左移1字节
    temp = state[1];
    state[1] = state[5];
    state[5] = state[9];
    state[9] = state[13];
    state[13] = temp;

    // 第三行左移2字节
    temp = state[2];
    state[2] = state[10];
    state[10] = temp;
    temp = state[6];
    state[6] = state[14];
    state[14] = temp;

    // 第四行左移3字节
    temp = state[15];
    state[15] = state[11];
    state[11] = state[7];
    state[7] = state[3];
    state[3] = temp;
}

// xtime (用于MixColumns)
static uint8_t xtime(uint8_t x)
{
    return ((x << 1) ^ (((x >> 7) & 1) * 0x1b));
}

// MixColumns
static void MixColumns(uint8_t* state)
{
    uint8_t i;
    uint8_t Tmp, Tm, t;

    for (i = 0; i < 4; ++i) {
        t = state[i * 4 + 0];
        Tmp = state[i * 4 + 0] ^ state[i * 4 + 1] ^ state[i * 4 + 2] ^ state[i * 4 + 3];

        Tm = state[i * 4 + 0] ^ state[i * 4 + 1];
        Tm = xtime(Tm);
        state[i * 4 + 0] ^= Tm ^ Tmp;

        Tm = state[i * 4 + 1] ^ state[i * 4 + 2];
        Tm = xtime(Tm);
        state[i * 4 + 1] ^= Tm ^ Tmp;

        Tm = state[i * 4 + 2] ^ state[i * 4 + 3];
        Tm = xtime(Tm);
        state[i * 4 + 2] ^= Tm ^ Tmp;

        Tm = state[i * 4 + 3] ^ t;
        Tm = xtime(Tm);
        state[i * 4 + 3] ^= Tm ^ Tmp;
    }
}

// Cipher - AES加密核心
static void Cipher(uint8_t* state, const uint8_t* RoundKey)
{
    uint8_t round = 0;

    // 初始轮密钥加
    AddRoundKey(0, state, RoundKey);

    // 9轮标准变换
    for (round = 1; round < 10; ++round) {
        SubBytes(state);
        ShiftRows(state);
        MixColumns(state);
        AddRoundKey(round, state, RoundKey);
    }

    // 最后一轮（无MixColumns）
    SubBytes(state);
    ShiftRows(state);
    AddRoundKey(10, state, RoundKey);
}

// ========== 公开API函数 ==========

void AES_init_ctx(struct AES_ctx* ctx, const uint8_t* key)
{
    KeyExpansion(ctx->RoundKey, key);
}

void AES_init_ctx_iv(struct AES_ctx* ctx, const uint8_t* key, const uint8_t* iv)
{
    KeyExpansion(ctx->RoundKey, key);
    memcpy(ctx->Iv, iv, AES_BLOCKLEN);
}

void AES_ECB_encrypt(const struct AES_ctx* ctx, uint8_t* buf)
{
    Cipher(buf, ctx->RoundKey);
}

void AES_CBC_encrypt_buffer(struct AES_ctx* ctx, uint8_t* buf, size_t length)
{
    size_t i;
    uint8_t j;

    for (i = 0; i < length; i += AES_BLOCKLEN) {
        // XOR with IV/previous ciphertext block
        for (j = 0; j < AES_BLOCKLEN; ++j) {
            buf[i + j] ^= ctx->Iv[j];
        }

        // Encrypt block
        Cipher(buf + i, ctx->RoundKey);

        // Update IV to current ciphertext block
        memcpy(ctx->Iv, buf + i, AES_BLOCKLEN);
    }
}

// STM32端不需要解密功能
void AES_ECB_decrypt(const struct AES_ctx* ctx, uint8_t* buf)
{
    (void)ctx;
    (void)buf;
}

void AES_CBC_decrypt_buffer(struct AES_ctx* ctx, uint8_t* buf, size_t length)
{
    (void)ctx;
    (void)buf;
    (void)length;
}