Question

我尝试在C中创建一个程序，使用openssl-lib加密目录中的所有文件。我用ntfw()读取目录并将文件名传递给处理函数handleCryptProcess()。功能执行波纹管程序。

创建一个临时文件来保存密文。
加密明文并将结果输出到cyphertext文件中。
删除纯文本文件。
将密文文件重命名为原始文件。

我使用RSA公钥来加密文件。

我的问题是，当我的文件夹包含多个文件时，我会收到细分错误。这与处理程序功能有关。我想，上述一个或多个程序无法有效处理内存。

当我的文件夹包含 ONLY ONE 文件时，该程序成功。

Bellow是我的处理函数：

#include "crypt.h"

/**
 * - First we generate the filepath of our output file with getCyphertextFilePath().
 * - The we check (cryptFlag) and determine if we want to encrypt or decrypt the file.
 * - encryptRSAFile() tries to encrypt the file under (fpath).
 *   decryptRSAFile() tries to decrypt the file under (fpath).
 * - We delete the original file using unlink().
 * - Lastly, rename the new file back to original filename with rename().
 */
int handleCryptProcess(const char *fpath, const en_de_crypt_flag cryptFlag) {
    int status;
    char *new_fpath = NULL; /* Hold the file path of our output file */

    status = getOutputFilePath(fpath, &new_fpath);
    if (status == -1) {
        return -1; /* Could not get the output filepath. */
    }

    if (cryptFlag == ENCRYPT) { /* We want to encrypt our file. */
        status = encryptRSAFile(fpath, new_fpath);
    } else { /* We want to decrypt our file. */
        status = decryptRSAFile(fpath, new_fpath);
    }   
    if (status == -1) {
        return -1; /* Failed to encrypt/decrypt fpath. */
    }

    status = unlink(fpath); /* Delete the original file. */
    if (status == -1) {
        return -1; /* Failed to delete original fpath. */
    }
    status = rename(new_fpath, fpath); /* Rename our file. */
    if (status == -1) {
        return -1; /* Failed to rename back to original fpath. */
    }
    return 0; /* File encrypted/decrypted successfully. */
}

这是我用来创建密文的那个：

#include "crypt.h"

/**
 * We use RSA asymmetric cryptography to create our cyphertext.
 * The public key was passed to (rsaPubKey) when we initialized it
 * in main() with publicRSATextKeyToStruct().
 * (fpath) is the file we want to encrypt.
 * (cyphertext_fpath) is our cyphertext.
 */
int encryptRSAFile(const char *fpath, const char *cyphertext_fpath) {
    FILE *fin, *fout;

    /**
     * Open the plaintext file we want to encrypt.
     */
    fin = fopen(fpath, "rb");
    if (fin == NULL) {
        return -1;
    }

    /**
     * Create a cyphertext file for writing to.
     */
    fout = fopen(cyphertext_fpath, "wb");
    if (fout == NULL) {
        return -1;
    }

    /**
     * The EVP_PKEY_new() function allocates an empty EVP_PKEY
     * structure which is used by OpenSSL to store private keys. 
     */
    EVP_PKEY *pkey = EVP_PKEY_new();

    EVP_CIPHER_CTX ctx; /* Cipher contex ctx. */
    unsigned char buffer[RSA_KEY_SIZE]; /* Buffer that holds out plaintext. */
    unsigned char buffer_out[RSA_KEY_SIZE + EVP_MAX_IV_LENGTH]; /* Buffer that holds the cyphertext. */
    size_t len;
    int len_out;

    /**
     * ek is an array of buffers where the public key encrypted secret key will be written, 
     * each buffer must contain enough room for the corresponding encrypted key.
     * That is ek[i] must have room for EVP_PKEY_size(pubk[i]) bytes
     */
    unsigned char *ek = NULL;
    int eklen;
    uint32_t eklen_n;
    unsigned char iv[EVP_MAX_IV_LENGTH]; /* Buffer where the generated IV is written to */


    if (!EVP_PKEY_assign_RSA(pkey, rsaPubKey)) {
        return -1;
    }

    EVP_CIPHER_CTX_init(&ctx); /* Initialize a new context. */
    ek = malloc(EVP_PKEY_size(pkey));

    /**
     * EVP_SealInit() initializes a cipher context (ctx) for encryption 
     * with cipher type using a random secret key and (iv).
     * Cipher type we use is AES 256.
     * The secret key is encrypted using our public key (pkey).
     */
    if (!EVP_SealInit(&ctx, EVP_aes_256_cbc(), &ek, &eklen, iv, &pkey, 1)) {
        return 2;
    }

    eklen_n = htonl(eklen);
    if (fwrite(&eklen_n, sizeof eklen_n, 1, fout) != 1) {
        return 3;
    }
    if (fwrite(ek, eklen, 1, fout) != 1) {
        return 4;
    }
    if (fwrite(iv, EVP_CIPHER_iv_length(EVP_aes_256_cbc()), 1, fout) != 1) {
        return 5;
    }

    while ((len = fread(buffer, 1, sizeof buffer, fin)) > 0) {
        if (!EVP_SealUpdate(&ctx, buffer_out, &len_out, buffer, len)) {
            return 6;
        }

        if (fwrite(buffer_out, len_out, 1, fout) != 1) {
            return 7;
        }
    }

    if (ferror(fin)) {
        return 8;
    }

    if (!EVP_SealFinal(&ctx, buffer_out, &len_out)) {
        return 9;
    }

    if (fwrite(buffer_out, len_out, 1, fout) != 1) {
        return 10;
    }

    EVP_PKEY_free(pkey);
    free(ek);
    fclose(fin);
    fclose(fout);
    return 0;
}

这是否与return值有关？也许是我如何检查错误状态。但是我无法理解，openssl文档在这方面并不是很支持。

更新

为了更清楚地了解发生了什么，我发布了一个例子。

假设我们有两个文件。

File1.ext
File2.ext

程序开始，读取File1对其进行加密并转到File2。

在File2上，我的代码在加密程序的以下情况下中断：

fwrite(ek, eklen, 1, fout) != 1

然后，我得到了一个分段错误。这并不总是发生在第二个文件中。如果可能发生在第三个之后，但永远不会发生。

如果我有三个文件，我可能会加密第一个文件，第二个文件会破坏程序，第三个文件会破坏程序。

尝试使用C和opensll-lib加密目录中的文件时出现分段错误

更新

0 个答案: