NSS Sample Code sample2

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NSS Sample Code 2: Symmetric Encryption


/* Example code to illustrate DES enccryption/decryption using NSS.
 * The example skips the details of obtaining the Key & IV to use, and
 * just uses a hardcoded Key & IV.
 * Note: IV is only needed if Cipher Blocking Chaining (CBC) mode of encryption
 *       is used
 *
 * The recommended approach is to store and transport WRAPPED (encrypted)
 * DES Keys (IVs can be in the clear). However, it is a common (and dangerous)
 * practice to use raw DES Keys. This example shows the use of a RAW key.
 */


#include "nss.h"
#include "pk11pub.h"

/* example Key & IV */
unsigned char gKey[] = {0xe8, 0xa7, 0x7c, 0xe2, 0x05, 0x63, 0x6a, 0x31};
unsigned char gIV[] = {0xe4, 0xbb, 0x3b, 0xd3, 0xc3, 0x71, 0x2e, 0x58};

int main(int argc, char **argv)
{
  CK_MECHANISM_TYPE  cipherMech;
  PK11SlotInfo*      slot = NULL;
  PK11SymKey*        SymKey = NULL;
  SECItem*           SecParam = NULL;
  PK11Context*       EncContext = NULL;
  SECItem            keyItem, ivItem;
  SECStatus          rv, rv1, rv2;
  unsigned char      data[1024], buf1[1024], buf2[1024];
  int                i, result_len, tmp1_outlen, tmp2_outlen;

  /* Initialize NSS
   * If your application code has already initialized NSS, you can skip it
   * here.
   * This code uses the simplest of the Init functions, which does not
   * require a NSS database to exist
   */
  rv = NSS_NoDB_Init(".");
  if (rv != SECSuccess)
  {
    fprintf(stderr, "NSS initialization failed (err %d)\n",
            PR_GetError());
    goto out;
  }

  /* choose mechanism: CKM_DES_CBC_PAD, CKM_DES3_ECB, CKM_DES3_CBC..... 
   * Note that some mechanisms (*_PAD) imply the padding is handled for you
   * by NSS. If you choose something else, then data padding is the
   * application's responsibility
   */
  cipherMech = CKM_DES_CBC_PAD;
  slot = PK11_GetBestSlot(cipherMech, NULL);
  /* slot = PK11_GetInternalKeySlot(); is a simpler alternative but in
   * theory, it *may not* return the optimal slot for the operation. For
   * DES ops, Internal slot is typically the best slot
   */
  if (slot == NULL)
  {
    fprintf(stderr, "Unable to find security device (err %d)\n",
            PR_GetError());
    goto out;
  }

  /* NSS passes blobs around as SECItems. These contain a pointer to
   * data and a length. Turn the raw key into a SECItem. */
  keyItem.type = siBuffer;
  keyItem.data = gKey;
  keyItem.len = sizeof(gKey);

  /* Turn the raw key into a key object. We use PK11_OriginUnwrap
   * to indicate the key was unwrapped - which is what should be done
   * normally anyway - using raw keys isn't a good idea */
  SymKey = PK11_ImportSymKey(slot, cipherMech, PK11_OriginUnwrap, CKA_ENCRYPT,
                             &keyItem, NULL);
  if (SymKey == NULL)
  {
    fprintf(stderr, "Failure to import key into NSS (err %d)\n",
            PR_GetError());
    goto out;
  }

  /* set up the PKCS11 encryption paramters.
   * when not using CBC mode, ivItem.data and ivItem.len can be 0, or you
   * can simply pass NULL for the iv parameter in PK11_ParamFromIV func
   */
  ivItem.type = siBuffer;
  ivItem.data = gIV;
  ivItem.len = sizeof(gIV);
  SecParam = PK11_ParamFromIV(cipherMech, &ivItem);
  if (SecParam == NULL)
  {
    fprintf(stderr, "Failure to set up PKCS11 param (err %d)\n",
            PR_GetError());
    goto out;
  }

  /* sample data we'll encrypt and decrypt */
  strcpy(data, "Encrypt me!");
  fprintf(stderr, "Clear Data: %s\n", data);

  /* ========================= START SECTION ============================= */
  /* If using the the same key and iv over and over, stuff before this     */
  /* section and after this section needs to be done only ONCE             */

  /* ENCRYPT data into buf1. buf1 len must be atleast (data len + 8) */
  tmp1_outlen = tmp2_outlen = 0;
 
  /* Create cipher context */
  EncContext = PK11_CreateContextBySymKey(cipherMech, CKA_ENCRYPT,
                                          SymKey, SecParam);
  rv1 = PK11_CipherOp(EncContext, buf1, &tmp1_outlen, sizeof(buf1),
                      data, strlen(data)+1);
  rv2 = PK11_DigestFinal(EncContext, buf1+tmp1_outlen, &tmp2_outlen,
                         sizeof(buf1)-tmp1_outlen);
  PK11_DestroyContext(EncContext, PR_TRUE);
  result_len = tmp1_outlen + tmp2_outlen;
  if (rv1 != SECSuccess || rv2 != SECSuccess)
    goto out;

  fprintf(stderr, "Encrypted Data: ");
  for (i=0; i<result_len; i++)
    fprintf(stderr, "%02x ", buf1[i]);
  fprintf(stderr, "\n");


  /* DECRYPT buf1 into buf2. buf2 len must be atleast buf1 len */
  tmp1_outlen = tmp2_outlen = 0;
 
  /* Create cipher context */
  EncContext = PK11_CreateContextBySymKey(cipherMech, CKA_DECRYPT,
                                          SymKey, SecParam);
  rv1 = PK11_CipherOp(EncContext, buf2, &tmp1_outlen, sizeof(buf2),
                      buf1, result_len);
  rv2 = PK11_DigestFinal(EncContext, buf2+tmp1_outlen, &tmp2_outlen,
                         result_len-tmp1_outlen);
  PK11_DestroyContext(EncContext, PR_TRUE);
  result_len = tmp1_outlen + tmp2_outlen;
  if (rv1 != SECSuccess || rv2 != SECSuccess)
    goto out;
 
  fprintf(stderr, "Decrypted Data: %s\n", buf2);

  /* =========================== END SECTION ============================= */

 
out:
  if (SymKey)
    PK11_FreeSymKey(SymKey);
  if (SecParam)
    SECITEM_FreeItem(SecParam, PR_TRUE);

}
 

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Contributors to this page: Sheppy, kwilson
Last updated by: Sheppy,