c - C语言 AES CBC 128 PCSKPadding7 解密问题？

Question

老师们好：

下面是一段C 语言结合openssl库做 AES CBC 128 PCSKPadding7 加密， 加密的部分是可以， 解密是总是出现乱码。请老师们帮忙给看看：

程序输出如下：

Ciphertext (Base64): O4SkNWTfpKVOSrvpdcwbXg==
Decrypted text: :▒▒1aٞ▒tp▒▒L▒$b;▒▒5dߤ▒NJ▒▒u▒

代码如下

#include <stdio.h>#include <stdlib.h>#include <string.h>#include <openssl/aes.h>#include <openssl/evp.h>#include <openssl/bio.h>#include <openssl/buffer.h>// PKCS7Padding填充函数int pkcs7padding(unsigned char *data, int len, int block_size) {    int pad_len = block_size - (len % block_size);    for (int i = 0; i < pad_len; i++) {        data[len + i] = pad_len;    }    return len + pad_len;}// PKCS7Padding去除填充函数int pkcs7unpadding(unsigned char *data, int len) {    int pad_len = data[len - 1];    return len - pad_len;}// AES CBC加密函数void aes_cbc_encrypt(unsigned char *plaintext, int plaintext_len, unsigned char *key,                     unsigned char *iv, unsigned char *ciphertext) {    AES_KEY aes_key;    AES_set_encrypt_key(key, 128, &aes_key);    AES_cbc_encrypt(plaintext, ciphertext, plaintext_len, &aes_key, iv, AES_ENCRYPT);}// AES CBC解密函数void aes_cbc_decrypt(unsigned char *ciphertext, int ciphertext_len, unsigned char *key,                     unsigned char *iv, unsigned char *plaintext) {    AES_KEY aes_key;    AES_set_decrypt_key(key, 128, &aes_key);    AES_cbc_encrypt(ciphertext, plaintext, ciphertext_len, &aes_key, iv, AES_DECRYPT);}// Base64编码函数char* base64_encode(const unsigned char* input, int length) {    BIO *bio, *b64;    BUF_MEM *bufferPtr;    b64 = BIO_new(BIO_f_base64());    bio = BIO_new(BIO_s_mem());    bio = BIO_push(b64, bio);    // 忽略换行符    BIO_set_flags(bio, BIO_FLAGS_BASE64_NO_NL);    BIO_write(bio, input, length);    BIO_flush(bio);    BIO_get_mem_ptr(bio, &bufferPtr);    char *output = (char*)malloc(bufferPtr->length + 1);    memcpy(output, bufferPtr->data, bufferPtr->length);    output[bufferPtr->length] = '\0';    BIO_free_all(bio);    return output;}// Base64解码函数unsigned char* base64_decode(const char* input, int length, int* decoded_length) {    BIO *bio, *b64;    unsigned char *buffer = (unsigned char*)malloc(length);    memset(buffer, 0, length);    b64 = BIO_new(BIO_f_base64());    bio = BIO_new_mem_buf((void*)input, length);    bio = BIO_push(b64, bio);    // 忽略换行符    BIO_set_flags(bio, BIO_FLAGS_BASE64_NO_NL);    int decoded_len = BIO_read(bio, buffer, length);    BIO_free_all(bio);    *decoded_length = decoded_len;    unsigned char* output = (unsigned char*)malloc(decoded_len + 1);    memcpy(output, buffer, decoded_len);    output[decoded_len] = '\0';    free(buffer);    return output;}int main() {    unsigned char key[16] = "0000000000123456";  // 128位密钥    unsigned char iv[16] = "0000000000123456";   // 初始向量    unsigned char plaintext[] = "123456";    int plaintext_len = strlen((char *)plaintext);    // 计算填充后的长度    int padded_len = pkcs7padding(plaintext, plaintext_len, 16);    unsigned char ciphertext[padded_len];    unsigned char decrypted_text[padded_len];    // 加密    aes_cbc_encrypt(plaintext, padded_len, key, iv, ciphertext);    // Base64编码    char* base64_encoded = base64_encode(ciphertext, padded_len);    printf("Ciphertext (Base64): %s\n", base64_encoded);    // Base64解码    int decoded_len;    unsigned char* decoded_ciphertext = base64_decode(base64_encoded, strlen(base64_encoded), &decoded_len);    // 解密    aes_cbc_decrypt(decoded_ciphertext, decoded_len, key, iv, decrypted_text);    // 去除填充字节    int decrypted_len = pkcs7unpadding(decrypted_text, decoded_len);    decrypted_text[decrypted_len] = '\0';    printf("Decrypted text: %s\n", decrypted_text);    free(base64_encoded);    free(decoded_ciphertext);    return 0;}

Answer 1

// 解密前重新设置IVunsigned char decrypt_iv[16] = "0000000000123456";// 解密aes_cbc_decrypt(decoded_ciphertext, decoded_len, key, decrypt_iv, decrypted_text);// 去除填充字节int pad_len = decrypted_text[decoded_len - 1];int decrypted_len = decoded_len - pad_len;// 检查填充是否正确for (int i = 0; i < pad_len; i++) {    if (decrypted_text[decrypted_len + i] != pad_len) {        printf("Padding error\n");        return -1;    }}decrypted_text[decrypted_len] = '\0';