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tools: Use new API of libgcrypt for gpg-pair-tool.

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* tools/gpg-pair-tool.c (create_dh_keypair): Just use
gcry_random_bytes for secret.  Call gcry_ecc_mul_point
with G to get the public key.
(compute_master_secret): Use gcry_ecc_mul_point.

Signed-off-by: NIIBE Yutaka <gniibe@fsij.org>
This commit is contained in:
NIIBE Yutaka 2019-06-20 11:58:23 +09:00
parent 49671b76ea
commit f22a004161
1 changed files with 21 additions and 67 deletions
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88
tools/gpg-pair-tool.c
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@ -1021,50 +1021,32 @@ create_dh_keypair (unsigned char *dh_secret, size_t dh_secret_len,
unsigned char *dh_public, size_t dh_public_len) unsigned char *dh_public, size_t dh_public_len)
{ {
gpg_error_t err; gpg_error_t err;
gcry_sexp_t sexp; unsigned char *p;
gcry_sexp_t s_keypair; const unsigned char G[32] = { 0x9 };
gcry_buffer_t secret;
gcry_buffer_t public;
unsigned char publicbuf[33];
/* We need a temporary buffer for the public key. Check the length /* We need a temporary buffer for the public key. Check the length
* for the later memcpy. */ * for the later memcpy. */
if (dh_public_len < 32) if (dh_public_len < 32 || dh_secret_len < 32)
return gpg_error (GPG_ERR_BUFFER_TOO_SHORT); return gpg_error (GPG_ERR_BUFFER_TOO_SHORT);
secret.size = dh_secret_len; p = gcry_random_bytes (32, GCRY_VERY_STRONG_RANDOM);
secret.data = dh_secret; if (!p)
secret.off = 0; return gpg_error_from_syserror ();
public.size = sizeof publicbuf;
public.data = publicbuf;
public.off = 0;
err = gcry_sexp_build (&sexp, NULL, memcpy (dh_secret, p, 32);
"(genkey(ecc(curve Curve25519)(flags djb-tweak)))"); xfree (p);
if (err)
return err; err = gcry_ecc_mul_point (GCRY_ECC_CURVE25519, &p, dh_secret, G);
err = gcry_pk_genkey (&s_keypair, sexp);
gcry_sexp_release (sexp);
if (err)
return err;
err = gcry_sexp_extract_param (s_keypair, "key-data!private-key",
"&dq", &secret, &public, NULL);
gcry_sexp_release (s_keypair);
if (err) if (err)
return err; return err;
/* Gcrypt prepends a 0x40 indicator - remove that. */ memcpy (dh_public, p, 32);
if (public.len == 33) xfree (p);
{
public.len = 32;
memmove (public.data, publicbuf+1, 32);
}
memcpy (dh_public, public.data, public.len);
if (DBG_CRYPTO) if (DBG_CRYPTO)
{ {
log_printhex (secret.data, secret.len, "DH secret:"); log_printhex (dh_secret, 32, "DH secret:");
log_printhex (public.data, public.len, "DH public:"); log_printhex (dh_public, 32, "DH public:");
} }
return 0; return 0;
@ -1189,52 +1171,24 @@ compute_master_secret (unsigned char *master, size_t masterlen,
const unsigned char *pk_b, size_t pk_b_len) const unsigned char *pk_b, size_t pk_b_len)
{ {
gpg_error_t err; gpg_error_t err;
gcry_sexp_t s_sk_a = NULL; unsigned char *s;
gcry_sexp_t s_pk_b = NULL;
gcry_sexp_t s_shared = NULL;
gcry_sexp_t s_tmp;
const char *s;
size_t n;
log_assert (masterlen == 32); log_assert (masterlen == 32);
log_assert (sk_a_len == 32);
log_assert (pk_b_len == 32);
err = gcry_sexp_build (&s_sk_a, NULL, "%b", (int)sk_a_len, sk_a); err = gcry_ecc_mul_point (GCRY_ECC_CURVE25519, &s, sk_a, pk_b);
if (!err)
err = gcry_sexp_build (&s_pk_b, NULL,
"(public-key(ecdh(curve Curve25519)"
" (flags djb-tweak)(q%b)))",
(int)pk_b_len, pk_b);
if (err)
{
log_error ("error building S-expression: %s\n", gpg_strerror (err));
goto leave;
}
err = gcry_pk_encrypt (&s_shared, s_sk_a, s_pk_b);
if (err) if (err)
{ {
log_error ("error computing DH: %s\n", gpg_strerror (err)); log_error ("error computing DH: %s\n", gpg_strerror (err));
goto leave; goto leave;
} }
/* gcry_log_debugsxp ("sk_a", s_sk_a); */
/* gcry_log_debugsxp ("pk_b", s_pk_b); */
/* gcry_log_debugsxp ("shared", s_shared); */
s_tmp = gcry_sexp_find_token (s_shared, "s", 0);
if (!s_tmp || !(s = gcry_sexp_nth_data (s_tmp, 1, &n))
|| n != 33 || s[0] != 0x40)
{
err = gpg_error (GPG_ERR_INTERNAL);
log_error ("error computing DH: %s\n", gpg_strerror (err));
goto leave;
}
memcpy (master, s+1, 32);
memcpy (master, s, 32);
leave: leave:
gcry_sexp_release (s_sk_a); xfree (s);
gcry_sexp_release (s_pk_b);
gcry_sexp_release (s_shared);
return err; return err;
} }