/* Give the name of the curve NAME, store the curve parameters into P,
A, B, G, and N if they point to NULL value. Note that G is returned
in standard uncompressed format. Also update MODEL and DIALECT if
they are not NULL. */
gpg_err_code_t
_gcry_ecc_update_curve_param (const char *name,
enum gcry_mpi_ec_models *model,
enum ecc_dialects *dialect,
gcry_mpi_t *p, gcry_mpi_t *a, gcry_mpi_t *b,
gcry_mpi_t *g, gcry_mpi_t *n)
{
int idx;
idx = find_domain_parms_idx (name);
if (idx < 0)
return GPG_ERR_UNKNOWN_CURVE;
if (g)
{
char *buf;
size_t len;
len = 4;
len += strlen (domain_parms[idx].g_x+2);
len += strlen (domain_parms[idx].g_y+2);
len++;
buf = xtrymalloc (len);
if (!buf)
return gpg_err_code_from_syserror ();
strcpy (stpcpy (stpcpy (buf, "0x04"), domain_parms[idx].g_x+2),
domain_parms[idx].g_y+2);
_gcry_mpi_release (*g);
*g = scanval (buf);
xfree (buf);
}
if (model)
*model = domain_parms[idx].model;
if (dialect)
*dialect = domain_parms[idx].dialect;
if (p)
{
_gcry_mpi_release (*p);
*p = scanval (domain_parms[idx].p);
}
if (a)
{
_gcry_mpi_release (*a);
*a = scanval (domain_parms[idx].a);
}
if (b)
{
_gcry_mpi_release (*b);
*b = scanval (domain_parms[idx].b);
}
if (n)
{
_gcry_mpi_release (*n);
*n = scanval (domain_parms[idx].n);
}
return 0;
}
/* Return the parameters of the curve NAME as an S-expression. */
gcry_sexp_t
_gcry_ecc_get_param_sexp (const char *name)
{
unsigned int nbits;
elliptic_curve_t E;
mpi_ec_t ctx;
gcry_mpi_t g_x, g_y;
gcry_mpi_t pkey[7];
gcry_sexp_t result;
int i;
memset (&E, 0, sizeof E);
if (_gcry_ecc_fill_in_curve (0, name, &E, &nbits))
return NULL;
g_x = mpi_new (0);
g_y = mpi_new (0);
ctx = _gcry_mpi_ec_p_internal_new (MPI_EC_WEIERSTRASS,
ECC_DIALECT_STANDARD,
0,
E.p, E.a, NULL);
if (_gcry_mpi_ec_get_affine (g_x, g_y, &E.G, ctx))
log_fatal ("ecc get param: Failed to get affine coordinates\n");
_gcry_mpi_ec_free (ctx);
_gcry_mpi_point_free_parts (&E.G);
pkey[0] = E.p;
pkey[1] = E.a;
pkey[2] = E.b;
pkey[3] = _gcry_ecc_ec2os (g_x, g_y, E.p);
pkey[4] = E.n;
pkey[5] = E.h;
pkey[6] = NULL;
mpi_free (g_x);
mpi_free (g_y);
if (sexp_build (&result, NULL,
"(public-key(ecc(p%m)(a%m)(b%m)(g%m)(n%m)(h%m)))",
pkey[0], pkey[1], pkey[2], pkey[3], pkey[4], pkey[5]))
result = NULL;
for (i=0; pkey[i]; i++)
_gcry_mpi_release (pkey[i]);
return result;
}
void
gcry_mpi_release (gcry_mpi_t a)
{
_gcry_mpi_release (a);
}
/* Return the name matching the parameters in PKEY. This works only
with curves described by the Weierstrass equation. */
const char *
_gcry_ecc_get_curve (gcry_sexp_t keyparms, int iterator, unsigned int *r_nbits)
{
gpg_err_code_t rc;
const char *result = NULL;
elliptic_curve_t E;
gcry_mpi_t mpi_g = NULL;
gcry_mpi_t tmp = NULL;
int idx;
memset (&E, 0, sizeof E);
if (r_nbits)
*r_nbits = 0;
if (!keyparms)
{
idx = iterator;
if (idx >= 0 && idx < DIM (domain_parms))
{
result = domain_parms[idx].desc;
if (r_nbits)
*r_nbits = domain_parms[idx].nbits;
}
return result;
}
/*
* Extract the curve parameters..
*/
rc = gpg_err_code (sexp_extract_param (keyparms, NULL, "-pabgn",
&E.p, &E.a, &E.b, &mpi_g, &E.n,
NULL));
if (rc == GPG_ERR_NO_OBJ)
{
/* This might be the second use case of checking whether a
specific curve given by name is supported. */
gcry_sexp_t l1;
char *name;
l1 = sexp_find_token (keyparms, "curve", 5);
if (!l1)
goto leave; /* No curve name parameter. */
name = sexp_nth_string (l1, 1);
sexp_release (l1);
if (!name)
goto leave; /* Name missing or out of core. */
idx = find_domain_parms_idx (name);
xfree (name);
if (idx >= 0) /* Curve found. */
{
result = domain_parms[idx].desc;
if (r_nbits)
*r_nbits = domain_parms[idx].nbits;
}
return result;
}
if (rc)
goto leave;
if (mpi_g)
{
_gcry_mpi_point_init (&E.G);
if (_gcry_ecc_os2ec (&E.G, mpi_g))
goto leave;
}
for (idx = 0; domain_parms[idx].desc; idx++)
{
mpi_free (tmp);
tmp = scanval (domain_parms[idx].p);
if (!mpi_cmp (tmp, E.p))
{
mpi_free (tmp);
tmp = scanval (domain_parms[idx].a);
if (!mpi_cmp (tmp, E.a))
{
mpi_free (tmp);
tmp = scanval (domain_parms[idx].b);
if (!mpi_cmp (tmp, E.b))
{
mpi_free (tmp);
tmp = scanval (domain_parms[idx].n);
if (!mpi_cmp (tmp, E.n))
{
mpi_free (tmp);
tmp = scanval (domain_parms[idx].g_x);
if (!mpi_cmp (tmp, E.G.x))
{
mpi_free (tmp);
tmp = scanval (domain_parms[idx].g_y);
if (!mpi_cmp (tmp, E.G.y))
{
result = domain_parms[idx].desc;
if (r_nbits)
*r_nbits = domain_parms[idx].nbits;
goto leave;
}
}
}
}
}
}
}
leave:
_gcry_mpi_release (tmp);
_gcry_mpi_release (E.p);
_gcry_mpi_release (E.a);
_gcry_mpi_release (E.b);
_gcry_mpi_release (mpi_g);
_gcry_mpi_point_free_parts (&E.G);
_gcry_mpi_release (E.n);
return result;
}
/* Verify an EdDSA signature. See sign_eddsa for the reference.
* Check if R_IN and S_IN verifies INPUT. PKEY has the curve
* parameters and PK is the EdDSA style encoded public key.
*/
gpg_err_code_t
_gcry_ecc_eddsa_verify (gcry_mpi_t input, ECC_public_key *pkey,
gcry_mpi_t r_in, gcry_mpi_t s_in, int hashalgo,
gcry_mpi_t pk)
{
int rc;
mpi_ec_t ctx = NULL;
int b;
unsigned int tmp;
mpi_point_struct Q; /* Public key. */
unsigned char *encpk = NULL; /* Encoded public key. */
unsigned int encpklen;
const void *mbuf, *rbuf;
unsigned char *tbuf = NULL;
size_t mlen, rlen;
unsigned int tlen;
unsigned char digest[64];
gcry_buffer_t hvec[3];
gcry_mpi_t h, s;
mpi_point_struct Ia, Ib;
if (!mpi_is_opaque (input) || !mpi_is_opaque (r_in) || !mpi_is_opaque (s_in))
return GPG_ERR_INV_DATA;
if (hashalgo != GCRY_MD_SHA512)
return GPG_ERR_DIGEST_ALGO;
point_init (&Q);
point_init (&Ia);
point_init (&Ib);
h = mpi_new (0);
s = mpi_new (0);
ctx = _gcry_mpi_ec_p_internal_new (pkey->E.model, pkey->E.dialect, 0,
pkey->E.p, pkey->E.a, pkey->E.b);
b = ctx->nbits/8;
if (b != 256/8)
return GPG_ERR_INTERNAL; /* We only support 256 bit. */
/* Decode and check the public key. */
rc = _gcry_ecc_eddsa_decodepoint (pk, ctx, &Q, &encpk, &encpklen);
if (rc)
goto leave;
if (!_gcry_mpi_ec_curve_point (&Q, ctx))
{
rc = GPG_ERR_BROKEN_PUBKEY;
goto leave;
}
if (DBG_CIPHER)
log_printhex (" e_pk", encpk, encpklen);
if (encpklen != b)
{
rc = GPG_ERR_INV_LENGTH;
goto leave;
}
/* Convert the other input parameters. */
mbuf = mpi_get_opaque (input, &tmp);
mlen = (tmp +7)/8;
if (DBG_CIPHER)
log_printhex (" m", mbuf, mlen);
rbuf = mpi_get_opaque (r_in, &tmp);
rlen = (tmp +7)/8;
if (DBG_CIPHER)
log_printhex (" r", rbuf, rlen);
if (rlen != b)
{
rc = GPG_ERR_INV_LENGTH;
goto leave;
}
/* h = H(encodepoint(R) + encodepoint(pk) + m) */
hvec[0].data = (char*)rbuf;
hvec[0].off = 0;
hvec[0].len = rlen;
hvec[1].data = encpk;
hvec[1].off = 0;
hvec[1].len = encpklen;
hvec[2].data = (char*)mbuf;
hvec[2].off = 0;
hvec[2].len = mlen;
rc = _gcry_md_hash_buffers (hashalgo, 0, digest, hvec, 3);
if (rc)
goto leave;
reverse_buffer (digest, 64);
if (DBG_CIPHER)
log_printhex (" H(R+)", digest, 64);
_gcry_mpi_set_buffer (h, digest, 64, 0);
/* According to the paper the best way for verification is:
encodepoint(sG - h·Q) = encodepoint(r)
because we don't need to decode R. */
{
void *sbuf;
unsigned int slen;
sbuf = _gcry_mpi_get_opaque_copy (s_in, &tmp);
slen = (tmp +7)/8;
reverse_buffer (sbuf, slen);
if (DBG_CIPHER)
log_printhex (" s", sbuf, slen);
_gcry_mpi_set_buffer (s, sbuf, slen, 0);
xfree (sbuf);
if (slen != b)
{
rc = GPG_ERR_INV_LENGTH;
goto leave;
}
}
_gcry_mpi_ec_mul_point (&Ia, s, &pkey->E.G, ctx);
_gcry_mpi_ec_mul_point (&Ib, h, &Q, ctx);
_gcry_mpi_neg (Ib.x, Ib.x);
_gcry_mpi_ec_add_points (&Ia, &Ia, &Ib, ctx);
rc = _gcry_ecc_eddsa_encodepoint (&Ia, ctx, s, h, 0, &tbuf, &tlen);
if (rc)
goto leave;
if (tlen != rlen || memcmp (tbuf, rbuf, tlen))
{
rc = GPG_ERR_BAD_SIGNATURE;
goto leave;
}
rc = 0;
leave:
xfree (encpk);
xfree (tbuf);
_gcry_mpi_ec_free (ctx);
_gcry_mpi_release (s);
_gcry_mpi_release (h);
point_free (&Ia);
point_free (&Ib);
point_free (&Q);
return rc;
}
/* Compute an EdDSA signature. See:
* [ed25519] 23pp. (PDF) Daniel J. Bernstein, Niels Duif, Tanja
* Lange, Peter Schwabe, Bo-Yin Yang. High-speed high-security
* signatures. Journal of Cryptographic Engineering 2 (2012), 77-89.
* Document ID: a1a62a2f76d23f65d622484ddd09caf8.
* URL: http://cr.yp.to/papers.html#ed25519. Date: 2011.09.26.
*
* Despite that this function requires the specification of a hash
* algorithm, we only support what has been specified by the paper.
* This may change in the future. Note that we don't check the used
* curve; the user is responsible to use Ed25519.
*
* Return the signature struct (r,s) from the message hash. The caller
* must have allocated R_R and S.
*/
gpg_err_code_t
_gcry_ecc_eddsa_sign (gcry_mpi_t input, ECC_secret_key *skey,
gcry_mpi_t r_r, gcry_mpi_t s, int hashalgo, gcry_mpi_t pk)
{
int rc;
mpi_ec_t ctx = NULL;
int b;
unsigned int tmp;
unsigned char *digest;
gcry_buffer_t hvec[3];
const void *mbuf;
size_t mlen;
unsigned char *rawmpi = NULL;
unsigned int rawmpilen;
unsigned char *encpk = NULL; /* Encoded public key. */
unsigned int encpklen;
mpi_point_struct I; /* Intermediate value. */
mpi_point_struct Q; /* Public key. */
gcry_mpi_t a, x, y, r;
memset (hvec, 0, sizeof hvec);
if (!mpi_is_opaque (input))
return GPG_ERR_INV_DATA;
/* Initialize some helpers. */
point_init (&I);
point_init (&Q);
a = mpi_snew (0);
x = mpi_new (0);
y = mpi_new (0);
r = mpi_new (0);
ctx = _gcry_mpi_ec_p_internal_new (skey->E.model, skey->E.dialect, 0,
skey->E.p, skey->E.a, skey->E.b);
b = (ctx->nbits+7)/8;
if (b != 256/8)
return GPG_ERR_INTERNAL; /* We only support 256 bit. */
rc = _gcry_ecc_eddsa_compute_h_d (&digest, skey->d, ctx);
if (rc)
goto leave;
_gcry_mpi_set_buffer (a, digest, 32, 0);
/* Compute the public key if it has not been supplied as optional
parameter. */
if (pk)
{
rc = _gcry_ecc_eddsa_decodepoint (pk, ctx, &Q, &encpk, &encpklen);
if (rc)
goto leave;
if (DBG_CIPHER)
log_printhex ("* e_pk", encpk, encpklen);
if (!_gcry_mpi_ec_curve_point (&Q, ctx))
{
rc = GPG_ERR_BROKEN_PUBKEY;
goto leave;
}
}
else
{
_gcry_mpi_ec_mul_point (&Q, a, &skey->E.G, ctx);
rc = _gcry_ecc_eddsa_encodepoint (&Q, ctx, x, y, 0, &encpk, &encpklen);
if (rc)
goto leave;
if (DBG_CIPHER)
log_printhex (" e_pk", encpk, encpklen);
}
/* Compute R. */
mbuf = mpi_get_opaque (input, &tmp);
mlen = (tmp +7)/8;
if (DBG_CIPHER)
log_printhex (" m", mbuf, mlen);
hvec[0].data = digest;
hvec[0].off = 32;
hvec[0].len = 32;
hvec[1].data = (char*)mbuf;
hvec[1].len = mlen;
rc = _gcry_md_hash_buffers (hashalgo, 0, digest, hvec, 2);
if (rc)
goto leave;
reverse_buffer (digest, 64);
if (DBG_CIPHER)
log_printhex (" r", digest, 64);
_gcry_mpi_set_buffer (r, digest, 64, 0);
_gcry_mpi_ec_mul_point (&I, r, &skey->E.G, ctx);
if (DBG_CIPHER)
log_printpnt (" r", &I, ctx);
/* Convert R into affine coordinates and apply encoding. */
rc = _gcry_ecc_eddsa_encodepoint (&I, ctx, x, y, 0, &rawmpi, &rawmpilen);
if (rc)
goto leave;
if (DBG_CIPHER)
log_printhex (" e_r", rawmpi, rawmpilen);
/* S = r + a * H(encodepoint(R) + encodepoint(pk) + m) mod n */
hvec[0].data = rawmpi; /* (this is R) */
hvec[0].off = 0;
hvec[0].len = rawmpilen;
hvec[1].data = encpk;
hvec[1].off = 0;
hvec[1].len = encpklen;
hvec[2].data = (char*)mbuf;
hvec[2].off = 0;
hvec[2].len = mlen;
rc = _gcry_md_hash_buffers (hashalgo, 0, digest, hvec, 3);
if (rc)
goto leave;
/* No more need for RAWMPI thus we now transfer it to R_R. */
mpi_set_opaque (r_r, rawmpi, rawmpilen*8);
rawmpi = NULL;
reverse_buffer (digest, 64);
if (DBG_CIPHER)
log_printhex (" H(R+)", digest, 64);
_gcry_mpi_set_buffer (s, digest, 64, 0);
mpi_mulm (s, s, a, skey->E.n);
mpi_addm (s, s, r, skey->E.n);
rc = eddsa_encodempi (s, b, &rawmpi, &rawmpilen);
if (rc)
goto leave;
if (DBG_CIPHER)
log_printhex (" e_s", rawmpi, rawmpilen);
mpi_set_opaque (s, rawmpi, rawmpilen*8);
rawmpi = NULL;
rc = 0;
leave:
_gcry_mpi_release (a);
_gcry_mpi_release (x);
_gcry_mpi_release (y);
_gcry_mpi_release (r);
xfree (digest);
_gcry_mpi_ec_free (ctx);
point_free (&I);
point_free (&Q);
xfree (encpk);
xfree (rawmpi);
return rc;
}
/**
* _gcry_ecc_eddsa_genkey - EdDSA version of the key generation.
*
* @sk: A struct to receive the secret key.
* @E: Parameters of the curve.
* @ctx: Elliptic curve computation context.
* @flags: Flags controlling aspects of the creation.
*
* Return: An error code.
*
* The only @flags bit used by this function is %PUBKEY_FLAG_TRANSIENT
* to use a faster RNG.
*/
gpg_err_code_t
_gcry_ecc_eddsa_genkey (ECC_secret_key *sk, elliptic_curve_t *E, mpi_ec_t ctx,
int flags)
{
gpg_err_code_t rc;
int b = 256/8; /* The only size we currently support. */
gcry_mpi_t a, x, y;
mpi_point_struct Q;
gcry_random_level_t random_level;
char *dbuf;
size_t dlen;
gcry_buffer_t hvec[1];
unsigned char *hash_d = NULL;
point_init (&Q);
memset (hvec, 0, sizeof hvec);
if ((flags & PUBKEY_FLAG_TRANSIENT_KEY))
random_level = GCRY_STRONG_RANDOM;
else
random_level = GCRY_VERY_STRONG_RANDOM;
a = mpi_snew (0);
x = mpi_new (0);
y = mpi_new (0);
/* Generate a secret. */
hash_d = xtrymalloc_secure (2*b);
if (!hash_d)
{
rc = gpg_error_from_syserror ();
goto leave;
}
dlen = b;
dbuf = _gcry_random_bytes_secure (dlen, random_level);
/* Compute the A value. */
hvec[0].data = dbuf;
hvec[0].len = dlen;
rc = _gcry_md_hash_buffers (GCRY_MD_SHA512, 0, hash_d, hvec, 1);
if (rc)
goto leave;
sk->d = _gcry_mpi_set_opaque (NULL, dbuf, dlen*8);
dbuf = NULL;
reverse_buffer (hash_d, 32); /* Only the first half of the hash. */
hash_d[0] = (hash_d[0] & 0x7f) | 0x40;
hash_d[31] &= 0xf8;
_gcry_mpi_set_buffer (a, hash_d, 32, 0);
xfree (hash_d); hash_d = NULL;
/* log_printmpi ("ecgen a", a); */
/* Compute Q. */
_gcry_mpi_ec_mul_point (&Q, a, &E->G, ctx);
if (DBG_CIPHER)
log_printpnt ("ecgen pk", &Q, ctx);
/* Copy the stuff to the key structures. */
sk->E.model = E->model;
sk->E.dialect = E->dialect;
sk->E.p = mpi_copy (E->p);
sk->E.a = mpi_copy (E->a);
sk->E.b = mpi_copy (E->b);
point_init (&sk->E.G);
point_set (&sk->E.G, &E->G);
sk->E.n = mpi_copy (E->n);
point_init (&sk->Q);
point_set (&sk->Q, &Q);
leave:
point_free (&Q);
_gcry_mpi_release (a);
_gcry_mpi_release (x);
_gcry_mpi_release (y);
xfree (hash_d);
return rc;
}
