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ecc-sos: Backport master change for ECDH.

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Signed-off-by: NIIBE Yutaka <gniibe@fsij.org>
This commit is contained in:
NIIBE Yutaka 2020-05-25 14:20:04 +09:00
parent bdf0fb3158
commit cbf30c1da9
3 changed files with 348 additions and 278 deletions
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502
g10/ecdh.c
View File

@ -82,20 +82,132 @@ pk_ecdh_default_params (unsigned int qbits)
}
/* Encrypts/decrypts DATA using a key derived from the ECC shared
point SHARED using the FIPS SP 800-56A compliant method
key_derivation+key_wrapping. If IS_ENCRYPT is true the function
encrypts; if false, it decrypts. PKEY is the public key and PK_FP
the fingerprint of this public key. On success the result is
stored at R_RESULT; on failure NULL is stored at R_RESULT and an
error code returned. */
gpg_error_t
pk_ecdh_encrypt_with_shared_point (int is_encrypt,
/* Extract xcomponent from the point SHARED. POINT_NBYTES is the
size to represent an EC point which is determined by the public
key. SECRET_X_SIZE is the size of x component to represent an
integer which is determined by the curve. */
static gpg_error_t
extract_secret_x (byte **r_secret_x,
const char *shared, size_t nshared,
size_t point_nbytes, size_t secret_x_size)
{
byte *secret_x;
*r_secret_x = NULL;
/* Extract X from the result. It must be in the format of:
04 || X || Y
40 || X
41 || X
Since it may come with the prefix, the size of point is larger
than or equals to the size of an integer X. */
if (point_nbytes < secret_x_size)
return gpg_error (GPG_ERR_BAD_DATA);
/* Extract x component of the shared point: this is the actual
shared secret. */
secret_x = xtrymalloc_secure (point_nbytes);
if (!secret_x)
return gpg_error_from_syserror ();
memcpy (secret_x, shared, nshared);
/* Remove the prefix. */
if ((point_nbytes & 1))
memmove (secret_x, secret_x+1, secret_x_size);
/* Clear the rest of data. */
if (point_nbytes - secret_x_size)
memset (secret_x+secret_x_size, 0, point_nbytes-secret_x_size);
if (DBG_CRYPTO)
log_printhex (secret_x, secret_x_size, "ECDH shared secret X is:");
*r_secret_x = secret_x;
return 0;
}
static gpg_error_t
build_kdf_params (unsigned char kdf_params[256], size_t *r_size,
gcry_mpi_t *pkey, const byte pk_fp[MAX_FINGERPRINT_LEN])
{
IOBUF obuf;
gpg_error_t err;
*r_size = 0;
obuf = iobuf_temp();
if (!obuf)
return gpg_error_from_syserror ();
/* variable-length field 1, curve name OID */
err = gpg_mpi_write_nohdr (obuf, pkey[0]);
/* fixed-length field 2 */
iobuf_put (obuf, PUBKEY_ALGO_ECDH);
/* variable-length field 3, KDF params */
err = (err ? err : gpg_mpi_write_nohdr (obuf, pkey[2]));
/* fixed-length field 4 */
iobuf_write (obuf, "Anonymous Sender ", 20);
/* fixed-length field 5, recipient fp */
iobuf_write (obuf, pk_fp, 20);
if (!err)
*r_size = iobuf_temp_to_buffer (obuf, kdf_params, 256);
iobuf_close (obuf);
if (!err)
{
if (DBG_CRYPTO)
log_printhex (kdf_params, *r_size, "ecdh KDF message params are:");
}
return err;
}
/* Derive KEK with KEK_SIZE into the memory at SECRET_X. */
static gpg_error_t
derive_kek (size_t kek_size,
int kdf_hash_algo,
byte *secret_x, int secret_x_size,
const unsigned char *kdf_params, size_t kdf_params_size)
{
gpg_error_t err;
gcry_md_hd_t h;
log_assert( gcry_md_get_algo_dlen (kdf_hash_algo) >= 32 );
err = gcry_md_open (&h, kdf_hash_algo, 0);
if (err)
{
log_error ("gcry_md_open failed for kdf_hash_algo %d: %s",
kdf_hash_algo, gpg_strerror (err));
return err;
}
gcry_md_write(h, "\x00\x00\x00\x01", 4); /* counter = 1 */
gcry_md_write(h, secret_x, secret_x_size); /* x of the point X */
gcry_md_write(h, kdf_params, kdf_params_size); /* KDF parameters */
gcry_md_final (h);
memcpy (secret_x, gcry_md_read (h, kdf_hash_algo), kek_size);
gcry_md_close (h);
/* Clean the tail before returning. */
memset (secret_x+kek_size, 0, secret_x_size - kek_size);
if (DBG_CRYPTO)
log_printhex (secret_x, kek_size, "ecdh KEK is:");
return err;
}
/* Prepare ECDH using SHARED, PK_FP fingerprint, and PKEY array.
Returns the cipher handle in R_HD, which needs to be closed by
the caller. */
static gpg_error_t
prepare_ecdh_with_shared_point (const char *shared, size_t nshared,
const byte pk_fp[MAX_FINGERPRINT_LEN],
const byte *data, size_t ndata,
gcry_mpi_t *pkey,
gcry_mpi_t *r_result)
gcry_mpi_t *pkey, gcry_cipher_hd_t *r_hd)
{
gpg_error_t err;
byte *secret_x;
@ -105,66 +217,16 @@ pk_ecdh_encrypt_with_shared_point (int is_encrypt,
size_t kek_params_size;
int kdf_hash_algo;
int kdf_encr_algo;
unsigned char message[256];
size_t message_size;
unsigned char kdf_params[256];
size_t kdf_params_size;
size_t kek_size;
gcry_cipher_hd_t hd;
*r_result = NULL;
*r_hd = NULL;
nbits = pubkey_nbits (PUBKEY_ALGO_ECDH, pkey);
if (!nbits)
return gpg_error (GPG_ERR_TOO_SHORT);
{
size_t nbytes;
/* Extract x component of the shared point: this is the actual
shared secret. */
nbytes = (mpi_get_nbits (pkey[1] /* public point */)+7)/8;
secret_x = xtrymalloc_secure (nshared);
if (!secret_x)
return gpg_error_from_syserror ();
memcpy (secret_x, shared, nshared);
/* Expected size of the x component */
secret_x_size = (nbits+7)/8;
/* Extract X from the result. It must be in the format of:
04 || X || Y
40 || X
41 || X
Since it always comes with the prefix, it's larger than X. In
old experimental version of libgcrypt, there is a case where it
returns X with no prefix of 40, so, nbytes == secret_x_size
is allowed. */
if (nbytes < secret_x_size)
{
xfree (secret_x);
return gpg_error (GPG_ERR_BAD_DATA);
}
/* Remove the prefix. */
if ((nbytes & 1))
memmove (secret_x, secret_x+1, secret_x_size);
/* Clear the rest of data. */
if (nbytes - secret_x_size)
memset (secret_x+secret_x_size, 0, nbytes-secret_x_size);
if (DBG_CRYPTO)
log_printhex (secret_x, secret_x_size, "ECDH shared secret X is:");
}
/*** We have now the shared secret bytes in secret_x. ***/
/* At this point we are done with PK encryption and the rest of the
* function uses symmetric key encryption techniques to protect the
* input DATA. The following two sections will simply replace
* current secret_x with a value derived from it. This will become
* a KEK.
*/
if (!gcry_mpi_get_flag (pkey[2], GCRYMPI_FLAG_OPAQUE))
return gpg_error (GPG_ERR_BUG);
kek_params = gcry_mpi_get_opaque (pkey[2], &nbits);
kek_params_size = (nbits+7)/8;
@ -173,10 +235,7 @@ pk_ecdh_encrypt_with_shared_point (int is_encrypt,
/* Expect 4 bytes 03 01 hash_alg symm_alg. */
if (kek_params_size != 4 || kek_params[0] != 3 || kek_params[1] != 1)
{
xfree (secret_x);
return gpg_error (GPG_ERR_BAD_PUBKEY);
}
kdf_hash_algo = kek_params[2];
kdf_encr_algo = kek_params[3];
@ -189,91 +248,56 @@ pk_ecdh_encrypt_with_shared_point (int is_encrypt,
if (kdf_hash_algo != GCRY_MD_SHA256
&& kdf_hash_algo != GCRY_MD_SHA384
&& kdf_hash_algo != GCRY_MD_SHA512)
{
xfree (secret_x);
return gpg_error (GPG_ERR_BAD_PUBKEY);
}
if (kdf_encr_algo != CIPHER_ALGO_AES
&& kdf_encr_algo != CIPHER_ALGO_AES192
&& kdf_encr_algo != CIPHER_ALGO_AES256)
{
xfree (secret_x);
return gpg_error (GPG_ERR_BAD_PUBKEY);
}
kek_size = gcry_cipher_get_algo_keylen (kdf_encr_algo);
if (kek_size > gcry_md_get_algo_dlen (kdf_hash_algo))
return gpg_error (GPG_ERR_BAD_PUBKEY);
/* Build kdf_params. */
{
IOBUF obuf;
err = build_kdf_params (kdf_params, &kdf_params_size, pkey, pk_fp);
if (err)
return err;
obuf = iobuf_temp();
/* variable-length field 1, curve name OID */
err = gpg_mpi_write_nohdr (obuf, pkey[0]);
/* fixed-length field 2 */
iobuf_put (obuf, PUBKEY_ALGO_ECDH);
/* variable-length field 3, KDF params */
err = (err ? err : gpg_mpi_write_nohdr (obuf, pkey[2]));
/* fixed-length field 4 */
iobuf_write (obuf, "Anonymous Sender ", 20);
/* fixed-length field 5, recipient fp */
iobuf_write (obuf, pk_fp, 20);
nbits = pubkey_nbits (PUBKEY_ALGO_ECDH, pkey);
if (!nbits)
return gpg_error (GPG_ERR_TOO_SHORT);
message_size = iobuf_temp_to_buffer (obuf, message, sizeof message);
iobuf_close (obuf);
secret_x_size = (nbits+7)/8;
if (kek_size > secret_x_size)
return gpg_error (GPG_ERR_BAD_PUBKEY);
err = extract_secret_x (&secret_x, shared, nshared,
/* pkey[1] is the public point */
(mpi_get_nbits (pkey[1])+7)/8,
secret_x_size);
if (err)
return err;
/*** We have now the shared secret bytes in secret_x. ***/
/* At this point we are done with PK encryption and the rest of the
* function uses symmetric key encryption techniques to protect the
* input DATA. The following two sections will simply replace
* current secret_x with a value derived from it. This will become
* a KEK.
*/
/* Derive a KEK (key wrapping key) using SECRET_X and KDF_PARAMS. */
err = derive_kek (kek_size, kdf_hash_algo, secret_x,
secret_x_size, kdf_params, kdf_params_size);
if (err)
{
xfree (secret_x);
return err;
}
if(DBG_CRYPTO)
log_printhex (message, message_size, "ecdh KDF message params are:");
}
/* Derive a KEK (key wrapping key) using MESSAGE and SECRET_X. */
{
gcry_md_hd_t h;
int old_size;
err = gcry_md_open (&h, kdf_hash_algo, 0);
if (err)
{
log_error ("gcry_md_open failed for kdf_hash_algo %d: %s",
kdf_hash_algo, gpg_strerror (err));
xfree (secret_x);
return err;
}
gcry_md_write(h, "\x00\x00\x00\x01", 4); /* counter = 1 */
gcry_md_write(h, secret_x, secret_x_size); /* x of the point X */
gcry_md_write(h, message, message_size); /* KDF parameters */
gcry_md_final (h);
log_assert( gcry_md_get_algo_dlen (kdf_hash_algo) >= 32 );
memcpy (secret_x, gcry_md_read (h, kdf_hash_algo),
gcry_md_get_algo_dlen (kdf_hash_algo));
gcry_md_close (h);
old_size = secret_x_size;
log_assert( old_size >= gcry_cipher_get_algo_keylen( kdf_encr_algo ) );
secret_x_size = gcry_cipher_get_algo_keylen( kdf_encr_algo );
log_assert( secret_x_size <= gcry_md_get_algo_dlen (kdf_hash_algo) );
/* We could have allocated more, so clean the tail before returning. */
memset (secret_x+secret_x_size, 0, old_size - secret_x_size);
if (DBG_CRYPTO)
log_printhex (secret_x, secret_x_size, "ecdh KEK is:");
}
/* And, finally, aeswrap with key secret_x. */
{
gcry_cipher_hd_t hd;
byte *data_buf;
int data_buf_size;
gcry_mpi_t result;
err = gcry_cipher_open (&hd, kdf_encr_algo, GCRY_CIPHER_MODE_AESWRAP, 0);
if (err)
{
@ -283,22 +307,53 @@ pk_ecdh_encrypt_with_shared_point (int is_encrypt,
return err;
}
err = gcry_cipher_setkey (hd, secret_x, secret_x_size);
secret_x = NULL;
err = gcry_cipher_setkey (hd, secret_x, kek_size);
xfree (secret_x);
secret_x = NULL;
if (err)
{
gcry_cipher_close (hd);
log_error ("ecdh failed in gcry_cipher_setkey: %s\n",
gpg_strerror (err));
return err;
}
else
*r_hd = hd;
return err;
}
/* Encrypts DATA using a key derived from the ECC shared point SHARED
using the FIPS SP 800-56A compliant method
key_derivation+key_wrapping. PKEY is the public key and PK_FP the
fingerprint of this public key. On success the result is stored at
R_RESULT; on failure NULL is stored at R_RESULT and an error code
returned. */
gpg_error_t
pk_ecdh_encrypt_with_shared_point (const char *shared, size_t nshared,
const byte pk_fp[MAX_FINGERPRINT_LEN],
const byte *data, size_t ndata,
gcry_mpi_t *pkey, gcry_mpi_t *r_result)
{
gpg_error_t err;
gcry_cipher_hd_t hd;
byte *data_buf;
int data_buf_size;
gcry_mpi_t result;
byte *in;
*r_result = NULL;
err = prepare_ecdh_with_shared_point (shared, nshared, pk_fp, pkey, &hd);
if (err)
return err;
data_buf_size = ndata;
if ((data_buf_size & 7) != (is_encrypt ? 0 : 1))
if ((data_buf_size & 7) != 0)
{
log_error ("can't use a shared secret of %d bytes for ecdh\n",
data_buf_size);
gcry_cipher_close (hd);
return gpg_error (GPG_ERR_BAD_DATA);
}
@ -310,9 +365,7 @@ pk_ecdh_encrypt_with_shared_point (int is_encrypt,
return err;
}
if (is_encrypt)
{
byte *in = data_buf+1+data_buf_size+8;
in = data_buf+1+data_buf_size+8;
/* Write data MPI into the end of data_buf. data_buf is size
aeswrap data. */
@ -348,65 +401,6 @@ pk_ecdh_encrypt_with_shared_point (int is_encrypt,
}
*r_result = result;
}
else
{
byte *in;
if (!data || ndata > data_buf_size || !ndata)
{
xfree (data_buf);
return gpg_error (GPG_ERR_BAD_MPI);
}
memcpy (data_buf, data, ndata);
if (data_buf[0] != ndata-1)
{
log_error ("ecdh inconsistent size\n");
xfree (data_buf);
return gpg_error (GPG_ERR_BAD_MPI);
}
in = data_buf+data_buf_size;
data_buf_size = data_buf[0];
if (DBG_CRYPTO)
log_printhex (data_buf+1, data_buf_size, "ecdh decrypting :");
err = gcry_cipher_decrypt (hd, in, data_buf_size, data_buf+1,
data_buf_size);
gcry_cipher_close (hd);
if (err)
{
log_error ("ecdh failed in gcry_cipher_decrypt: %s\n",
gpg_strerror (err));
xfree (data_buf);
return err;
}
data_buf_size -= 8;
if (DBG_CRYPTO)
log_printhex (in, data_buf_size, "ecdh decrypted to :");
/* Padding is removed later. */
/* if (in[data_buf_size-1] > 8 ) */
/* { */
/* log_error ("ecdh failed at decryption: invalid padding." */
/* " 0x%02x > 8\n", in[data_buf_size-1] ); */
/* return gpg_error (GPG_ERR_BAD_KEY); */
/* } */
err = gcry_mpi_scan (&result, GCRYMPI_FMT_USG, in, data_buf_size, NULL);
xfree (data_buf);
if (err)
{
log_error ("ecdh failed to create a plain text MPI: %s\n",
gpg_strerror (err));
return err;
}
*r_result = result;
}
}
return err;
}
@ -462,21 +456,97 @@ pk_ecdh_generate_ephemeral_key (gcry_mpi_t *pkey, gcry_mpi_t *r_k)
/* Perform ECDH decryption. */
int
pk_ecdh_decrypt (gcry_mpi_t * result, const byte sk_fp[MAX_FINGERPRINT_LEN],
pk_ecdh_decrypt (gcry_mpi_t * r_result, const byte sk_fp[MAX_FINGERPRINT_LEN],
gcry_mpi_t data,
const byte *frame, size_t nframe, gcry_mpi_t * skey)
const byte *shared, size_t nshared, gcry_mpi_t * skey)
{
int r;
byte *p;
gpg_error_t err;
gcry_cipher_hd_t hd;
size_t nbytes;
byte *data_buf;
int data_buf_size;
byte *in;
const void *p;
unsigned int nbits;
if (!data)
*r_result = NULL;
err = prepare_ecdh_with_shared_point (shared, nshared, sk_fp, skey, &hd);
if (err)
return err;
p = gcry_mpi_get_opaque (data, &nbits);
nbytes = (nbits+7)/8;
data_buf_size = nbytes;
if ((data_buf_size & 7) != 1)
{
log_error ("can't use a shared secret of %d bytes for ecdh\n",
data_buf_size);
gcry_cipher_close (hd);
return gpg_error (GPG_ERR_BAD_DATA);
}
data_buf = xtrymalloc_secure( 1 + 2*data_buf_size + 8);
if (!data_buf)
{
err = gpg_error_from_syserror ();
gcry_cipher_close (hd);
return err;
}
if (!p)
{
xfree (data_buf);
gcry_cipher_close (hd);
return gpg_error (GPG_ERR_BAD_MPI);
}
memcpy (data_buf, p, nbytes);
if (data_buf[0] != nbytes-1)
{
log_error ("ecdh inconsistent size\n");
xfree (data_buf);
gcry_cipher_close (hd);
return gpg_error (GPG_ERR_BAD_MPI);
}
in = data_buf+data_buf_size;
data_buf_size = data_buf[0];
p = gcry_mpi_get_opaque (data, &nbits);/*encr data as an MPI*/
if (DBG_CRYPTO)
log_printhex (data_buf+1, data_buf_size, "ecdh decrypting :");
r = pk_ecdh_encrypt_with_shared_point (0 /*=decryption*/, frame, nframe,
sk_fp, p, (nbits+7)/8,
skey, result);
return r;
err = gcry_cipher_decrypt (hd, in, data_buf_size, data_buf+1,
data_buf_size);
gcry_cipher_close (hd);
if (err)
{
log_error ("ecdh failed in gcry_cipher_decrypt: %s\n",
gpg_strerror (err));
xfree (data_buf);
return err;
}
data_buf_size -= 8;
if (DBG_CRYPTO)
log_printhex (in, data_buf_size, "ecdh decrypted to :");
/* Padding is removed later. */
/* if (in[data_buf_size-1] > 8 ) */
/* { */
/* log_error ("ecdh failed at decryption: invalid padding." */
/* " 0x%02x > 8\n", in[data_buf_size-1] ); */
/* return gpg_error (GPG_ERR_BAD_KEY); */
/* } */
err = gcry_mpi_scan (r_result, GCRYMPI_FMT_USG, in, data_buf_size, NULL);
xfree (data_buf);
if (err)
{
log_error ("ecdh failed to create a plain text MPI: %s\n",
gpg_strerror (err));
return err;
}
return err;
}

4
g10/pkglue.c
View File

@ -376,8 +376,8 @@ pk_encrypt (pubkey_algo_t algo, gcry_mpi_t *resarr, gcry_mpi_t data,
{
unsigned int nbits;
byte *p = gcry_mpi_get_opaque (data, &nbits);
rc = pk_ecdh_encrypt_with_shared_point (1 /*=encrypton*/, shared, nshared,
fp, p, (nbits+7)/8, pkey, &result);
rc = pk_ecdh_encrypt_with_shared_point (shared, nshared, fp, p,
(nbits+7)/8, pkey, &result);
}
xfree (shared);
if (!rc)

2
g10/pkglue.h
View File

@ -36,7 +36,7 @@ int pk_check_secret_key (pubkey_algo_t algo, gcry_mpi_t *skey);
gcry_mpi_t pk_ecdh_default_params (unsigned int qbits);
gpg_error_t pk_ecdh_generate_ephemeral_key (gcry_mpi_t *pkey, gcry_mpi_t *r_k);
gpg_error_t pk_ecdh_encrypt_with_shared_point
/* */ (int is_encrypt, const char *shared, size_t nshared,
/* */ (const char *shared, size_t nshared,
const byte pk_fp[MAX_FINGERPRINT_LEN],
const byte *data, size_t ndata,
gcry_mpi_t *pkey,