Bug in ECDSA_do_sign?

[Oezguer Kesim]

Hello,

attached you can find some test code of mine utilizing ECDSA_do_sign and
ECDSA_do_verify.  It simply signs "fnord" and verifys the signature.

The strange thing is:  sig->r and sig->s are different from call to
call of the program.  i2d_ECDSA_SIG also returns different length of the
DER encoded version of the signature at each call of the program, for
that matter.

Am I missing something or is this a bug in ecdsa?

regards,

  Özgür Kesim

#include <openssl/objects.h>
#include <openssl/ecdsa.h>
#include <openssl/evp.h>
#include <openssl/ec.h>
#include <openssl/pem.h>
#include <stdio.h>
#include <assert.h>

ECDSA_SIG* sig;
ECDSA_SIG* sig2;

/* Keys generated with:
 *
 * ecdsa.key: 
 * 	openssl ecparam -genkey -name wap-wsg-idm-ecid-wtls8 \
 * 		-conv_form compressed > ecdsa.key
 * ecdsa.pub:
 * 	openssl ec -in ecdsa.key -pubout -out ecdsa.pub
 */

char privkey[]=
	"-----BEGIN EC PARAMETERS-----\n"
	"BgVnKw0ECA==\n"
	"-----END EC PARAMETERS-----\n"
	"-----BEGIN EC PRIVATE KEY-----\n"
	"MD4CAQEEDthN31VEyito/izDlzDPoAcGBWcrDQQIoSADHgAE8qeUbBtKNIUgmHIl\n"
	"goPQpt7McJZvBbz0/NF88Q==\n"
	"-----END EC PRIVATE KEY-----\n";

char pubkey[]=
	"-----BEGIN PUBLIC KEY-----\n"
	"MDIwEAYHKoZIzj0CAQYFZysNBAgDHgAE8qeUbBtKNIUgmHIlgoPQpt7McJZvBbz0\n"
	"/NF88Q==\n"
	"-----END PUBLIC KEY-----\n";

int sign(const char* data,unsigned int len) {
  BIO* in;
  EC_KEY* pkey;

  in=BIO_new_mem_buf(privkey,sizeof(privkey));
  if (!in) return -1;

  /* load private key */
  pkey=PEM_read_bio_ECPrivateKey(in, NULL, NULL, NULL /* passphrase */);
  if (!pkey) return -1;

  /* sign data */
  sig = ECDSA_do_sign(data, len, pkey);
  if (!sig) return -1;
  return 1;
}

int verify(const char* data,unsigned int len) {
  int    r;
  BIO* in;
  EC_KEY *pub_key;

  in=BIO_new_mem_buf(pubkey,sizeof(pubkey));
  if (!in) return -1;

  /* load public key */
  pub_key = PEM_read_bio_EC_PUBKEY(in, NULL, NULL, NULL);
  if (!pub_key) return -1;

  r = ECDSA_do_verify(data, len, sig2, pub_key);
  if (r < 0) return -1;
  else if (r == 0) return 0;
  else return 1;
}

int main() {
  unsigned char buf[1024];
  unsigned char* x;
  int r;
  r=sign("fnord",5);
  printf("sign returned %d\n",r);
  x=buf;
  printf("(sig->r, sig->s): (%s,%s)\n", BN_bn2hex(sig->r), BN_bn2hex(sig->s));
  r=i2d_ECDSA_SIG(sig,&x);
  printf("i2d_ECDSA_SIG returned %p, length %d\n",sig, r);
  *x=0; x=buf;
  sig2=d2i_ECDSA_SIG(&sig2,(const unsigned char**)&x,r);
  printf("d2i_ECDSA_SIG returned %p\n",sig2);
  r=verify("fnord",5);
  printf("verify returned %d\n",r);
}