麻烦换成使用openssl库进行透明加密的代码示例

以下是一个使用 OpenSSL 库进行透明加密的示例代码，主要使用了 OpenSSL 的 BIO 接口：

#include <openssl/err.h>
#include <openssl/evp.h>
#include <openssl/bio.h>

void handleErrors(void)
{
    ERR_print_errors_fp(stderr);
    abort();
}

int encrypt(unsigned char *plaintext, int plaintext_len, unsigned char *key,
            unsigned char *iv, unsigned char *ciphertext)
{
    EVP_CIPHER_CTX *ctx;
    int len;
    int ciphertext_len;

    /* Create and initialise the context */
    if (!(ctx = EVP_CIPHER_CTX_new())) {
        handleErrors();
    }

    /* Initialise the encryption operation */
    if (1 != EVP_EncryptInit_ex(ctx, EVP_aes_256_cbc(), NULL, key, iv)) {
        handleErrors();
    }

    /* Provide the message to be encrypted, and obtain the encrypted output */
    if (1 != EVP_EncryptUpdate(ctx, ciphertext, &len, plaintext, plaintext_len)) {
        handleErrors();
    }
    ciphertext_len = len;

    /* Finalise the encryption */
    if (1 != EVP_EncryptFinal_ex(ctx, ciphertext + len, &len)) {
        handleErrors();
    }
    ciphertext_len += len;

    /* Clean up */
    EVP_CIPHER_CTX_free(ctx);

    return ciphertext_len;
}

int decrypt(unsigned char *ciphertext, int ciphertext_len, unsigned char *key,
            unsigned char *iv, unsigned char *plaintext)
{
    EVP_CIPHER_CTX *ctx;
    int len;
    int plaintext_len;
    int ret;

    /* Create and initialise the context */
    if (!(ctx = EVP_CIPHER_CTX_new())) {
        handleErrors();
    }

    /* Initialise the decryption operation */
    if (1 != EVP_DecryptInit_ex(ctx, EVP_aes_256_cbc(), NULL, key, iv)) {
        handleErrors();
    }

    /* Provide the message to be decrypted, and obtain the plaintext output */
    if (1 != EVP_DecryptUpdate(ctx, plaintext, &len, ciphertext, ciphertext_len)) {
        handleErrors();
    }
    plaintext_len = len;

    /* Finalise the decryption */
    ret = EVP_DecryptFinal_ex(ctx, plaintext + len, &len);
    if (ret != 1) {
        /* Clean up */
        EVP_CIPHER_CTX_free(ctx);
        return 0;
    }
    plaintext_len += len;

    /* Clean up */
    EVP_CIPHER_CTX_free(ctx);

    return plaintext_len;
}

int encrypt_file(char *in_filename, char *out_filename, unsigned char *key,
                 unsigned char *iv)
{
    EVP_CIPHER_CTX *ctx;
    BIO *in, *out;
    unsigned char inbuf[1024], outbuf[1024 + EVP_MAX_BLOCK_LENGTH];
    int inlen, outlen, tmplen;
    int ciphertext_len = 0;

    /* Create and initialise the context */
    if (!(ctx = EVP_CIPHER_CTX_new())) {
        handleErrors();
    }

    /* Initialise the encryption operation */
    if (1 != EVP_EncryptInit_ex(ctx, EVP_aes_256_cbc(), NULL, key, iv)) {
        handleErrors();
    }

    /* Open the input and output files */
    if ((in = BIO_new_file(in_filename, "rb")) == NULL) {
        handleErrors();
    }
    if ((out = BIO_new_file(out_filename, "wb")) == NULL) {
        handleErrors();
    }

    /* Process the input file */
    while ((inlen = BIO_read(in, inbuf, 1024)) > 0) {
        if (1 != EVP_EncryptUpdate(ctx, outbuf, &outlen, inbuf, inlen)) {
            handleErrors();
        }
        if (BIO_write(out, outbuf, outlen) != outlen) {
            handleErrors();
        }
        ciphertext_len += outlen;
    }

    /* Finalise the encryption */
    if (1 != EVP_EncryptFinal_ex(ctx, outbuf, &tmplen)) {
        handleErrors();
    }
    if (BIO_write(out, outbuf, tmplen) != tmplen) {
        handleErrors();
    }
    ciphertext_len += tmplen;

    /* Clean up */
    BIO_free_all(in);
    BIO_free_all(out);
    EVP_CIPHER_CTX_free(ctx);

    return ciphertext_len;
}

int decrypt_file(char *in_filename, char *out_filename, unsigned char *key,
                 unsigned char *iv)
{
    EVP_CIPHER_CTX *ctx;
    BIO *in, *out;
    unsigned char inbuf[1024 + EVP_MAX_BLOCK_LENGTH], outbuf[1024];
    int inlen, outlen, tmplen;
    int plaintext_len = 0;
    int ret;

    /* Create and initialise the context */
    if (!(ctx = EVP_CIPHER_CTX_new())) {
        handleErrors();
    }

    /* Initialise the decryption operation */
    if (1 != EVP_DecryptInit_ex(ctx, EVP_aes_256_cbc(), NULL, key, iv)) {
        handleErrors();
    }

    /* Open the input and output files */
    if ((in = BIO_new_file(in_filename, "rb")) == NULL) {
        handleErrors();
    }
    if ((out = BIO_new_file(out_filename, "wb")) == NULL) {
        handleErrors();
    }

    /* Process the input file */
    while ((inlen = BIO_read(in, inbuf, 1024 + EVP_MAX_BLOCK_LENGTH)) > 0) {
        ret = EVP_DecryptUpdate(ctx, outbuf, &outlen, inbuf, inlen);
        if (ret != 1) {
            /* Clean up */
            BIO_free_all(in);
            BIO_free_all(out);
            EVP_CIPHER_CTX_free(ctx);
            return 0;
        }
        if (BIO_write(out, outbuf, outlen) != outlen) {
            handleErrors();
        }
        plaintext_len += outlen;
    }

    /* Finalise the decryption */
    ret = EVP_DecryptFinal_ex(ctx, outbuf, &tmplen);
    if (ret != 1) {
        /* Clean up */
        BIO_free_all(in);
        BIO_free_all(out);
        EVP_CIPHER_CTX_free(ctx);
        return 0;
    }
    if (BIO_write(out, outbuf, tmplen) != tmplen) {
        handleErrors();
    }
    plaintext_len += tmplen;

    /* Clean up */
    BIO_free_all(in);
    BIO_free_all(out);
    EVP_CIPHER_CTX_free(ctx);

    return plaintext_len;
}

int main()
{
    unsigned char key[EVP_MAX_KEY_LENGTH] = "01234567890123456789012345678901";
    unsigned char iv[EVP_MAX_IV_LENGTH] = "0123456789012345";
    char *in_filename = "input.txt";
    char *out_filename = "output.txt";
    int plaintext_len, ciphertext_len, decryptedtext_len;

    /* Encrypt the input file */
    ciphertext_len = encrypt_file(in_filename, out_filename, key, iv);
    printf("Encrypted file size: %d bytes\n", ciphertext_len);

    /* Decrypt the output file */
    decryptedtext_len = decrypt_file(out_filename, "decrypted.txt", key, iv);
    printf("Decrypted file size: %d bytes\n", decryptedtext_len);

    return 0;
}

请注意，这只是一个示例代码，仅用于演示如何使用 OpenSSL 库进行透明加密。您需要根据自己的需求对代码进行修改。同时，为了确保安全性，请务必注意密钥的生成和存储，以及加密和解密的数据完整性。