/*
** Performs an ECDH key derivation by computing the scalar point
** multiplication of privateValue and publicValue (with or without the
** cofactor) and returns the x-coordinate of the resulting elliptic
** curve point in derived secret. If successful, derivedSecret->data
** is set to the address of the newly allocated buffer containing the
** derived secret, and derivedSecret->len is the size of the secret
** produced. It is the caller's responsibility to free the allocated
** buffer containing the derived secret.
*/
SECStatus
ECDH_Derive(SECItem *publicValue,
ECParams *ecParams,
SECItem *privateValue,
PRBool withCofactor,
SECItem *derivedSecret)
{
SECStatus rv = SECFailure;
#ifndef NSS_DISABLE_ECC
unsigned int len = 0;
SECItem pointQ = {siBuffer, NULL, 0};
mp_int k; /* to hold the private value */
mp_int cofactor;
mp_err err = MP_OKAY;
#if EC_DEBUG
int i;
#endif
if (!publicValue || !ecParams || !privateValue ||
!derivedSecret) {
PORT_SetError(SEC_ERROR_INVALID_ARGS);
return SECFailure;
}
MP_DIGITS(&k) = 0;
memset(derivedSecret, 0, sizeof *derivedSecret);
len = (ecParams->fieldID.size + 7) >> 3;
pointQ.len = 2*len + 1;
if ((pointQ.data = PORT_Alloc(2*len + 1)) == NULL) goto cleanup;
CHECK_MPI_OK( mp_init(&k) );
CHECK_MPI_OK( mp_read_unsigned_octets(&k, privateValue->data,
(mp_size) privateValue->len) );
if (withCofactor && (ecParams->cofactor != 1)) {
/* multiply k with the cofactor */
MP_DIGITS(&cofactor) = 0;
CHECK_MPI_OK( mp_init(&cofactor) );
mp_set(&cofactor, ecParams->cofactor);
CHECK_MPI_OK( mp_mul(&k, &cofactor, &k) );
}
/* Multiply our private key and peer's public point */
if (ec_points_mul(ecParams, NULL, &k, publicValue, &pointQ) != SECSuccess)
goto cleanup;
if (ec_point_at_infinity(&pointQ)) {
PORT_SetError(SEC_ERROR_BAD_KEY); /* XXX better error code? */
goto cleanup;
}
/* Allocate memory for the derived secret and copy
* the x co-ordinate of pointQ into it.
*/
SECITEM_AllocItem(NULL, derivedSecret, len);
memcpy(derivedSecret->data, pointQ.data + 1, len);
rv = SECSuccess;
#if EC_DEBUG
printf("derived_secret:\n");
for (i = 0; i < derivedSecret->len; i++)
printf("%02x:", derivedSecret->data[i]);
printf("\n");
#endif
cleanup:
mp_clear(&k);
if (err) {
MP_TO_SEC_ERROR(err);
}
if (pointQ.data) {
PORT_ZFree(pointQ.data, 2*len + 1);
}
#else
PORT_SetError(SEC_ERROR_UNSUPPORTED_KEYALG);
#endif /* NSS_DISABLE_ECC */
return rv;
}
/*
** Checks the signature on the given digest using the key provided.
*/
SECStatus
ECDSA_VerifyDigest(ECPublicKey *key, const SECItem *signature,
const SECItem *digest)
{
SECStatus rv = SECFailure;
#ifndef NSS_DISABLE_ECC
mp_int r_, s_; /* tuple (r', s') is received signature) */
mp_int c, u1, u2, v; /* intermediate values used in verification */
mp_int x1;
mp_int n;
mp_err err = MP_OKAY;
ECParams *ecParams = NULL;
SECItem pointC = { siBuffer, NULL, 0 };
int slen; /* length in bytes of a half signature (r or s) */
int flen; /* length in bytes of the field size */
unsigned olen; /* length in bytes of the base point order */
unsigned obits; /* length in bits of the base point order */
#if EC_DEBUG
char mpstr[256];
printf("ECDSA verification called\n");
#endif
/* Initialize MPI integers. */
/* must happen before the first potential call to cleanup */
MP_DIGITS(&r_) = 0;
MP_DIGITS(&s_) = 0;
MP_DIGITS(&c) = 0;
MP_DIGITS(&u1) = 0;
MP_DIGITS(&u2) = 0;
MP_DIGITS(&x1) = 0;
MP_DIGITS(&v) = 0;
MP_DIGITS(&n) = 0;
/* Check args */
if (!key || !signature || !digest) {
PORT_SetError(SEC_ERROR_INVALID_ARGS);
goto cleanup;
}
ecParams = &(key->ecParams);
flen = (ecParams->fieldID.size + 7) >> 3;
olen = ecParams->order.len;
if (signature->len == 0 || signature->len%2 != 0 ||
signature->len > 2*olen) {
PORT_SetError(SEC_ERROR_INPUT_LEN);
goto cleanup;
}
slen = signature->len/2;
SECITEM_AllocItem(NULL, &pointC, 2*flen + 1);
if (pointC.data == NULL)
goto cleanup;
CHECK_MPI_OK( mp_init(&r_) );
CHECK_MPI_OK( mp_init(&s_) );
CHECK_MPI_OK( mp_init(&c) );
CHECK_MPI_OK( mp_init(&u1) );
CHECK_MPI_OK( mp_init(&u2) );
CHECK_MPI_OK( mp_init(&x1) );
CHECK_MPI_OK( mp_init(&v) );
CHECK_MPI_OK( mp_init(&n) );
/*
** Convert received signature (r', s') into MPI integers.
*/
CHECK_MPI_OK( mp_read_unsigned_octets(&r_, signature->data, slen) );
CHECK_MPI_OK( mp_read_unsigned_octets(&s_, signature->data + slen, slen) );
/*
** ANSI X9.62, Section 5.4.2, Steps 1 and 2
**
** Verify that 0 < r' < n and 0 < s' < n
*/
SECITEM_TO_MPINT(ecParams->order, &n);
if (mp_cmp_z(&r_) <= 0 || mp_cmp_z(&s_) <= 0 ||
mp_cmp(&r_, &n) >= 0 || mp_cmp(&s_, &n) >= 0) {
PORT_SetError(SEC_ERROR_BAD_SIGNATURE);
goto cleanup; /* will return rv == SECFailure */
}
/*
** ANSI X9.62, Section 5.4.2, Step 3
**
** c = (s')**-1 mod n
*/
CHECK_MPI_OK( mp_invmod(&s_, &n, &c) ); /* c = (s')**-1 mod n */
/*
** ANSI X9.62, Section 5.4.2, Step 4
**
** u1 = ((HASH(M')) * c) mod n
*/
SECITEM_TO_MPINT(*digest, &u1); /* u1 = HASH(M) */
/* In the definition of EC signing, digests are truncated
* to the length of n in bits.
* (see SEC 1 "Elliptic Curve Digit Signature Algorithm" section 4.1.*/
CHECK_MPI_OK( (obits = mpl_significant_bits(&n)) );
if (digest->len*8 > obits) { /* u1 = HASH(M') */
mpl_rsh(&u1,&u1,digest->len*8 - obits);
}
#if EC_DEBUG
mp_todecimal(&r_, mpstr);
printf("r_: %s (dec)\n", mpstr);
mp_todecimal(&s_, mpstr);
printf("s_: %s (dec)\n", mpstr);
mp_todecimal(&c, mpstr);
printf("c : %s (dec)\n", mpstr);
mp_todecimal(&u1, mpstr);
printf("digest: %s (dec)\n", mpstr);
#endif
CHECK_MPI_OK( mp_mulmod(&u1, &c, &n, &u1) ); /* u1 = u1 * c mod n */
/*
** ANSI X9.62, Section 5.4.2, Step 4
**
** u2 = ((r') * c) mod n
*/
CHECK_MPI_OK( mp_mulmod(&r_, &c, &n, &u2) );
/*
** ANSI X9.62, Section 5.4.3, Step 1
**
** Compute u1*G + u2*Q
** Here, A = u1.G B = u2.Q and C = A + B
** If the result, C, is the point at infinity, reject the signature
*/
if (ec_points_mul(ecParams, &u1, &u2, &key->publicValue, &pointC)
!= SECSuccess) {
rv = SECFailure;
goto cleanup;
}
if (ec_point_at_infinity(&pointC)) {
PORT_SetError(SEC_ERROR_BAD_SIGNATURE);
rv = SECFailure;
goto cleanup;
}
CHECK_MPI_OK( mp_read_unsigned_octets(&x1, pointC.data + 1, flen) );
/*
** ANSI X9.62, Section 5.4.4, Step 2
**
** v = x1 mod n
*/
CHECK_MPI_OK( mp_mod(&x1, &n, &v) );
#if EC_DEBUG
mp_todecimal(&r_, mpstr);
printf("r_: %s (dec)\n", mpstr);
mp_todecimal(&v, mpstr);
printf("v : %s (dec)\n", mpstr);
#endif
/*
** ANSI X9.62, Section 5.4.4, Step 3
**
** Verification: v == r'
*/
if (mp_cmp(&v, &r_)) {
PORT_SetError(SEC_ERROR_BAD_SIGNATURE);
rv = SECFailure; /* Signature failed to verify. */
} else {
rv = SECSuccess; /* Signature verified. */
}
#if EC_DEBUG
mp_todecimal(&u1, mpstr);
printf("u1: %s (dec)\n", mpstr);
mp_todecimal(&u2, mpstr);
printf("u2: %s (dec)\n", mpstr);
mp_tohex(&x1, mpstr);
printf("x1: %s\n", mpstr);
mp_todecimal(&v, mpstr);
printf("v : %s (dec)\n", mpstr);
#endif
cleanup:
mp_clear(&r_);
mp_clear(&s_);
mp_clear(&c);
mp_clear(&u1);
mp_clear(&u2);
mp_clear(&x1);
mp_clear(&v);
mp_clear(&n);
if (pointC.data) SECITEM_FreeItem(&pointC, PR_FALSE);
if (err) {
MP_TO_SEC_ERROR(err);
rv = SECFailure;
}
#if EC_DEBUG
printf("ECDSA verification %s\n",
(rv == SECSuccess) ? "succeeded" : "failed");
#endif
#else
PORT_SetError(SEC_ERROR_UNSUPPORTED_KEYALG);
#endif /* NSS_DISABLE_ECC */
return rv;
}
/*
** Performs an ECDH key derivation by computing the scalar point
** multiplication of privateValue and publicValue (with or without the
** cofactor) and returns the x-coordinate of the resulting elliptic
** curve point in derived secret. If successful, derivedSecret->data
** is set to the address of the newly allocated buffer containing the
** derived secret, and derivedSecret->len is the size of the secret
** produced. It is the caller's responsibility to free the allocated
** buffer containing the derived secret.
*/
SECStatus
ECDH_Derive(SECItem *publicValue,
ECParams *ecParams,
SECItem *privateValue,
PRBool withCofactor,
SECItem *derivedSecret)
{
SECStatus rv = SECFailure;
#ifndef NSS_DISABLE_ECC
unsigned int len = 0;
SECItem pointQ = { siBuffer, NULL, 0 };
mp_int k; /* to hold the private value */
mp_int cofactor;
mp_err err = MP_OKAY;
#if EC_DEBUG
int i;
#endif
if (!publicValue || !ecParams || !privateValue || !derivedSecret ||
!ecParams->name) {
PORT_SetError(SEC_ERROR_INVALID_ARGS);
return SECFailure;
}
/* Perform curve specific multiplication using ECMethod */
if (ecParams->fieldID.type == ec_field_plain) {
const ECMethod *method;
memset(derivedSecret, 0, sizeof(*derivedSecret));
derivedSecret = SECITEM_AllocItem(NULL, derivedSecret, ecParams->pointSize);
if (derivedSecret == NULL) {
PORT_SetError(SEC_ERROR_NO_MEMORY);
return SECFailure;
}
method = ec_get_method_from_name(ecParams->name);
if (method == NULL || method->validate == NULL ||
method->mul == NULL) {
PORT_SetError(SEC_ERROR_UNSUPPORTED_ELLIPTIC_CURVE);
return SECFailure;
}
if (method->validate(publicValue) != SECSuccess) {
PORT_SetError(SEC_ERROR_BAD_KEY);
return SECFailure;
}
return method->mul(derivedSecret, privateValue, publicValue);
}
/*
* We fail if the public value is the point at infinity, since
* this produces predictable results.
*/
if (ec_point_at_infinity(publicValue)) {
PORT_SetError(SEC_ERROR_BAD_KEY);
return SECFailure;
}
MP_DIGITS(&k) = 0;
memset(derivedSecret, 0, sizeof *derivedSecret);
len = (ecParams->fieldID.size + 7) >> 3;
pointQ.len = ecParams->pointSize;
if ((pointQ.data = PORT_Alloc(ecParams->pointSize)) == NULL)
goto cleanup;
CHECK_MPI_OK(mp_init(&k));
CHECK_MPI_OK(mp_read_unsigned_octets(&k, privateValue->data,
(mp_size)privateValue->len));
if (withCofactor && (ecParams->cofactor != 1)) {
/* multiply k with the cofactor */
MP_DIGITS(&cofactor) = 0;
CHECK_MPI_OK(mp_init(&cofactor));
mp_set(&cofactor, ecParams->cofactor);
CHECK_MPI_OK(mp_mul(&k, &cofactor, &k));
}
/* Multiply our private key and peer's public point */
if (ec_points_mul(ecParams, NULL, &k, publicValue, &pointQ) != SECSuccess) {
goto cleanup;
}
if (ec_point_at_infinity(&pointQ)) {
PORT_SetError(SEC_ERROR_BAD_KEY); /* XXX better error code? */
goto cleanup;
}
/* Allocate memory for the derived secret and copy
* the x co-ordinate of pointQ into it.
*/
SECITEM_AllocItem(NULL, derivedSecret, len);
memcpy(derivedSecret->data, pointQ.data + 1, len);
rv = SECSuccess;
#if EC_DEBUG
printf("derived_secret:\n");
for (i = 0; i < derivedSecret->len; i++)
printf("%02x:", derivedSecret->data[i]);
printf("\n");
#endif
cleanup:
mp_clear(&k);
if (err) {
MP_TO_SEC_ERROR(err);
}
if (pointQ.data) {
PORT_ZFree(pointQ.data, ecParams->pointSize);
}
#else
PORT_SetError(SEC_ERROR_UNSUPPORTED_KEYALG);
#endif /* NSS_DISABLE_ECC */
return rv;
}
