OpenSSL AES-CBC-256, Raw data to hex?

[Phantom139]

hello, I have a AES-256 function using openSSL's EVP library, the output however, comes out as raw ascii characters, how can I convert this to be readable hex characters to compare it with the online php script?

#include <openssl/evp.h>

int aes_init(unsigned char * key_data, int key_data_len, EVP_CIPHER_CTX * e_ctx, EVP_CIPHER_CTX * d_ctx) {
   int i, nrounds = 5;
   unsigned char key[32], iv[32];
   i = EVP_BytesToKey(EVP_aes_256_cbc(), EVP_sha1(), NULL, key_data, key_data_len, nrounds, key, iv);
   if (i != 32) {
      printf("Key size is %d bits - should be 256 bits\n", i);
      return -1;
   }

   EVP_CIPHER_CTX_init(e_ctx);
   EVP_EncryptInit_ex(e_ctx, EVP_aes_256_cbc(), NULL, key, iv);
   EVP_CIPHER_CTX_init(d_ctx);
   EVP_DecryptInit_ex(d_ctx, EVP_aes_256_cbc(), NULL, key, iv);

   return 0;
}

unsigned char * aes_encrypt(EVP_CIPHER_CTX * e, unsigned char * plaintext, int * len) {
   int c_len = *len + AES_BLOCK_SIZE, f_len = 0;
   unsigned char *ciphertext = (unsigned char *)malloc(c_len);

   EVP_EncryptInit_ex(e, NULL, NULL, NULL, NULL);
   EVP_EncryptUpdate(e, ciphertext, &c_len, plaintext, *len);
   EVP_EncryptFinal_ex(e, ciphertext+c_len, &f_len);

   *len = c_len + f_len;
   return ciphertext;
}

unsigned char * aes_decrypt(EVP_CIPHER_CTX * e, unsigned char * ciphertext, int * len) {
   int p_len = *len, f_len = 0;
   unsigned char *plaintext = (unsigned char *)malloc(p_len);
  
   EVP_DecryptInit_ex(e, NULL, NULL, NULL, NULL);
   EVP_DecryptUpdate(e, plaintext, &p_len, ciphertext, *len);
   EVP_DecryptFinal_ex(e, plaintext+p_len, &f_len);

   *len = p_len + f_len;
   return plaintext;
}

int do_aesOPS(char * inputText, char * inputKey) {
   EVP_CIPHER_CTX en, de;

   unsigned char * key_data;
   int key_data_len;

   key_data = (unsigned char *)inputKey;
   key_data_len = strlen(inputKey);
  
   if (aes_init(key_data, key_data_len, &en, &de)) {
      printf("Couldn't initialize AES cipher\n");
      return -1;
   }
   char *plaintext;
   unsigned char *ciphertext;
   int olen, len;
    
   olen = len = strlen(inputText)+1;
    
   ciphertext = aes_encrypt(&en, (unsigned char *)inputText, &len);
   plaintext = (char *)aes_decrypt(&de, ciphertext, &len);

   if (strncmp(plaintext, inputText, olen)) { 
      printf("FAIL: enc/dec failed for \"%s\"\n", inputText);
   }
   else { 
	  printf("AES Encrypted: \"%s\"\n", (char *)ciphertext);
	  printf("AES Decrypted: \"%s\"\n", plaintext);
   }    
   free(ciphertext);
   free(plaintext);
   EVP_CIPHER_CTX_cleanup(&en);
   EVP_CIPHER_CTX_cleanup(&de);

   return 0;
}

Decryption works fine, it comes back out to the starting value, but the encrypt comes out to ascii characters.

[Phantom139]

Bumping this.


I've tried this bit of code here:

    std::string hexString;
    //declare the scope of cipher

   	CryptoPP::StringSink* SSINK = new CryptoPP::StringSink(hexString);
	CryptoPP::HexEncoder* hex = new CryptoPP::HexEncoder(SSINK, false);
	CryptoPP::StringSource source(str, true, hex);
	
	return hexString;

using CryptoPP's hex encoder filter, but it just outputs null. This is the very last piece of the system I need (AES-256-CBC), and I just need to convert these ascii characters to HEX in order to complete it.

Any help here would be great, thanks.

[bartoli]

Hmm, do you mean you need something like this?

char * restrict const hexOutput = (char*)malloc(len*2 + 1);
char tmpBuf[4];
int pos=0;

hexOutput[0] = '\0';
for(;pos<len;pos++){
 tmpBuf[0] = '\0';
 sprintf(tmpBuf, "%02x", (int)plainText[pos]);
 strcat(hexOutput,tmpBuf);
}
printf("%s\n",hexOutput);

(i assumed you want C code)

[Phantom139]

Sorry, but that code doesn't compile for my program, and it only crashes when I call it (I made edits so it compiled).

I was looking for C++ too, but thanks for offering your help. :P

[Phantom139]

maybe I should provide this:

This is the output I get from the program:

it's an unsigned char * variable.

Çó9úŠö<? ûÞÎ/+O_œÆ…š&ÂÇE-MÛïÍÍýýýýÝÝ€¿'~¿0ç

I need to convert that to readable hex.

[gboelter]

Hi phantom,

did you found a solution for your convert2hex problem already.

I'm sure, it's easy, but I'm fighting with the same problem and can't fix it.