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    NSS Sample Code sample4

    NSS Sample Code 4: PKI Encryption


    /* Example code to illustrate PKI crypto ops (encrypt with public key,
     * decrypt with private key)
     *
     * Code assumes that you have set up a NSS database with a certificate
     * and a private key. The db password should be "test" and the cert
     * nickname should be "TestCA"
     * Here is one way of doing it:
     *   # create CA cert db, if -f not provided, prompts for passwd
     *   $ certutil -N -d .
     *   # create CA cert, self-signed, generates key-pair, prompts for key
     *   # type, cert type etc
     *   # answers for prompts: 5,9,n,y,-1,n,5,6,7,9,n
     *   $ certutil -S -s "CN=Test CA, O=BOGUS Inc, L=Mtn View, ST=CA, C=US"  \
     *     -n TestCA -t CTu,CTu,CTu -v 60 -x -d . -1 -2 -5
     *
     * There are many ways to setup a public/private key to use - this
     * example shows one of them.
     *
     * This example does not do any padding. It simply encrypts/decrypts a block
     * of length equal to modulus length of the public/private key.
     */


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


    /* this callback is responsible for returning the password to the NSS
     * key database. for example purposes, this function hardcodes the password.
     * In a real app, this function should obtain the password using secure means
     * such as prompting an operator, or retrieving it over a secure communication
     * channel
     */
    char *passwdcb(PK11SlotInfo *info, PRBool retry, void *arg);


    int main(int argc, char **argv)
    {
      SECStatus          rv;
      CERTCertificate   *cert = NULL;
      SECKEYPublicKey   *pubkey = NULL;
      SECKEYPrivateKey  *pvtkey = NULL;
      int                modulus_len, i, outlen;
      char              *buf1 = NULL;
      char              *buf2 = NULL;
     
      /* Initialize NSS */
      PK11_SetPasswordFunc(passwdcb);
      rv = NSS_Init(".");
      if (rv != SECSuccess)
      {
        fprintf(stderr, "NSS initialization failed (err %d)\n",
                PR_GetError());
        goto cleanup;
      }
     
      cert = PK11_FindCertFromNickname("TestCA", NULL);
      if (cert == NULL)
      {
        fprintf(stderr, "Couldn't find cert TestCA in NSS db (err %d)\n",
                PR_GetError());
        goto cleanup;
      }
     
      pubkey = CERT_ExtractPublicKey(cert);
      if (pubkey == NULL)
      {
        fprintf(stderr, "Couldn't extract public key from cert TestCA (err %d)\n",
                PR_GetError());
        goto cleanup;
      }

      modulus_len = SECKEY_PublicKeyStrength(pubkey);
      fprintf(stderr, "Public Key Modulus %d bytes\n", modulus_len);
      buf1 = (char *)malloc(modulus_len);
      buf2 = (char *)malloc(modulus_len);

      /* initialize buf1 */
      for (i=0;i<modulus_len;i++)
      {
        buf1[i]= (i %26) + 'A';
      }
      buf1[modulus_len-1] = '\0';
      fprintf(stderr, "Buffer being encrypted = \n%s\n", buf1);

      /* encrypt buf1, result will be in buf2 */
      rv = PK11_PubEncryptRaw(pubkey, buf2, buf1, modulus_len, NULL);
      if (rv != SECSuccess)
      {
        fprintf(stderr, "Encrypt with Public Key failed (err %d)\n",
                PR_GetError());
        goto cleanup;
      }
     
      pvtkey = PK11_FindKeyByAnyCert(cert, NULL);
      if (pvtkey == NULL)
      {
        fprintf(stderr, "Couldn't find private key for cert TestCA (err %d)\n",
                PR_GetError());
        goto cleanup;
      }

      /* clear buf1 */
      for (i=0;i<modulus_len;i++)
      {
        buf1[i]= '\0';
      }

      /* decrypt buf2, result will be in buf1 */
      rv = PK11_PubDecryptRaw(pvtkey, buf1, &outlen, modulus_len, buf2,
                              modulus_len);
      if (rv != SECSuccess)
      {
        fprintf(stderr, "Decrypt with Private Key failed (err %d)\n",
                PR_GetError());
        goto cleanup;
      }
     
      fprintf(stderr, "Result of decryption, outlen = %d\n", outlen);
      fprintf(stderr, "Result of decryption, buf = \n%s\n", buf1);

      exit(0);
     
    cleanup:
      if (cert)
        CERT_DestroyCertificate(cert);
      if (pubkey)
        SECKEY_DestroyPublicKey(pubkey);
      if (pvtkey)
        SECKEY_DestroyPrivateKey(pvtkey);
      if (buf1)
        free(buf1);
      if (buf2)
        free(buf2);                          
      exit(1);
    }

    char *passwdcb(PK11SlotInfo *info, PRBool retry, void *arg)
    {
      if (!retry)
        return PL_strdup("test");
      else
        return NULL;
    }

     

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