OpenSSL AES 256 CBC通过EV中的EVP api

2 回答

• 4

  这是我的代码版本 . 当然我更喜欢它，但我提供它作为替代品 . 注意完全没有错误检查：真正的代码会有它 .

  #include <string.h>
  #include <stdio.h>
  #include <stdlib.h>
  #include <openssl/evp.h>
  #include <openssl/aes.h>
  
  #ifndef TRUE
  #define TRUE 1
  #endif
  
  #ifndef FALSE
  #define FALSE 0
  #endif
  
  
  /**
   * Encrypt or decrypt, depending on flag 'should_encrypt'
   */
  void en_de_crypt(int should_encrypt, FILE *ifp, FILE *ofp, unsigned char *ckey, unsigned char *ivec) {
  
      const unsigned BUFSIZE=4096;
      unsigned char *read_buf = malloc(BUFSIZE);
      unsigned char *cipher_buf;
      unsigned blocksize;
      int out_len;
      EVP_CIPHER_CTX ctx;
  
      EVP_CipherInit(&ctx, EVP_aes_256_cbc(), ckey, ivec, should_encrypt);
      blocksize = EVP_CIPHER_CTX_block_size(&ctx);
      cipher_buf = malloc(BUFSIZE + blocksize);
  
      while (1) {
  
          // Read in data in blocks until EOF. Update the ciphering with each read.
  
          int numRead = fread(read_buf, sizeof(unsigned char), BUFSIZE, ifp);
          EVP_CipherUpdate(&ctx, cipher_buf, &out_len, read_buf, numRead);
          fwrite(cipher_buf, sizeof(unsigned char), out_len, ofp);
          if (numRead < BUFSIZE) { // EOF
              break;
          }
      }
  
      // Now cipher the final block and write it out.
  
      EVP_CipherFinal(&ctx, cipher_buf, &out_len);
      fwrite(cipher_buf, sizeof(unsigned char), out_len, ofp);
  
      // Free memory
  
      free(cipher_buf);
      free(read_buf);
  }
  
  int main(int argc, char *argv[]) {
  
      unsigned char ckey[] = "thiskeyisverybad";
      unsigned char ivec[] = "dontusethisinput";
      FILE *fIN, *fOUT;
  
      if (argc != 2) {
          printf("Usage: <executable> /path/to/file/exe");
          return -1;
      }
  
      // First encrypt the file
  
      fIN = fopen("plain.txt", "rb"); //File to be encrypted; plain text
      fOUT = fopen("cyphertext.txt", "wb"); //File to be written; cipher text
  
      en_de_crypt(TRUE, fIN, fOUT, ckey, ivec);
  
      fclose(fIN);
      fclose(fOUT);
  
      //Decrypt file now
  
      fIN = fopen("cyphertext.txt", "rb"); //File to be read; cipher text
      fOUT = fopen("decrypted.txt", "wb"); //File to be written; cipher text
  
      en_de_crypt(FALSE, fIN, fOUT, ckey, ivec);
  
      fclose(fIN);
      fclose(fOUT);
  
      return 0;
  }
  

  回复于 2024-04-24T20:49:58+08:00
• 9

  这段代码有效，如果有人对如何更清洁或更有效率有一些建议请发表评论 .

  #include <string.h>
  #include <stdio.h>
  #include <stdlib.h>
  #include <openssl/evp.h>
  #include <openssl/aes.h>
  
  void encrypt(FILE *ifp, FILE *ofp)
  {
      //Get file size
      fseek(ifp, 0L, SEEK_END);
      int fsize = ftell(ifp);
      //set back to normal
      fseek(ifp, 0L, SEEK_SET);
  
      int outLen1 = 0; int outLen2 = 0;
      unsigned char *indata = malloc(fsize);
      unsigned char *outdata = malloc(fsize*2);
      unsigned char ckey[] =  "thiskeyisverybad";
      unsigned char ivec[] = "dontusethisinput";
  
      //Read File
      fread(indata,sizeof(char),fsize, ifp);//Read Entire File
  
      //Set up encryption
      EVP_CIPHER_CTX ctx;
      EVP_EncryptInit(&ctx,EVP_aes_128_cbc(),ckey,ivec);
      EVP_EncryptUpdate(&ctx,outdata,&outLen1,indata,fsize);
      EVP_EncryptFinal(&ctx,outdata + outLen1,&outLen2);
      fwrite(outdata,sizeof(char),outLen1 + outLen2,ofp);
  }
  
  void decrypt(FILE *ifp, FILE *ofp)
  {
      //Get file size
      fseek(ifp, 0L, SEEK_END);
      int fsize = ftell(ifp);
      //set back to normal
      fseek(ifp, 0L, SEEK_SET);
  
      int outLen1 = 0; int outLen2 = 0;
      unsigned char *indata = malloc(fsize);
      unsigned char *outdata = malloc(fsize);
      unsigned char ckey[] =  "thiskeyisverybad";
      unsigned char ivec[] = "dontusethisinput";
  
      //Read File
      fread(indata,sizeof(char),fsize, ifp);//Read Entire File
  
      //setup decryption
      EVP_CIPHER_CTX ctx;
      EVP_DecryptInit(&ctx,EVP_aes_128_cbc(),ckey,ivec);
      EVP_DecryptUpdate(&ctx,outdata,&outLen1,indata,fsize);
      EVP_DecryptFinal(&ctx,outdata + outLen1,&outLen2);
      fwrite(outdata,sizeof(char),outLen1 + outLen2,ofp);
  }
  
  int main(int argc, char *argv[])
  {        
      if(argc != 2){
          printf("Usage: <executable> /path/to/file/exe");
          return -1;
      }
      FILE *fIN, *fOUT;
      fIN = fopen("plain.txt", "rb");//File to be encrypted; plain text
      fOUT = fopen("cyphertext.txt", "wb");//File to be written; cipher text
  
      encrypt(fIN, fOUT);
      fclose(fIN);
      fclose(fOUT);
      //Decrypt file now
      fIN = fopen("cyphertext.txt", "rb");//File to be written; cipher text
      fOUT = fopen("decrypted.txt", "wb");//File to be written; cipher text
      decrypt(fIN,fOUT);
      fclose(fIN);
      fclose(fOUT);
  
      return 0;
  }
  

  另外根据这篇文章，EVP api将处理任意大小的输入

  AES Encryption- large files

  回复于 2024-04-24T20:49:58+08:00