Fix conflict in EC private key writing

On the mbedtls-2.16 side, there was a change in commit
a7cfdad82e (PR r#503) in order to write
fixed-length private keys. It added a new helper function
pk_write_ec_private() for that.

On the baremetal side, there were changes in order to add a tinycrypt-based
implementation. It added a new helper function pk_write_ec_privkey() with two
implementations (with or without tinycrypt).

This commit keeps the function pk_write_ec_privkey() but changes its
implementation in the non-tinycrypt configuration in order to match the
implementation of pk_write_ec_private(), which is in turn removed it was only
used in that place.

The tinycrypt version of pk_write_ec_private() was already writing
constant-length private keys, so there is nothing to change here.
This commit is contained in:
Manuel Pégourié-Gonnard 2019-09-10 12:20:43 +02:00
parent 8abd0a0c84
commit fa4cbe0422

View file

@ -122,6 +122,9 @@ static int pk_write_ec_pubkey( unsigned char **p, unsigned char *start,
return( (int) len );
}
/*
* privateKey OCTET STRING -- always of length ceil(log2(n)/8)
*/
static int pk_write_ec_privkey( unsigned char **p, unsigned char *start,
mbedtls_pk_context const *key )
{
@ -183,11 +186,25 @@ static int pk_write_ec_pubkey( unsigned char **p, unsigned char *start,
return( (int) len );
}
/*
* privateKey OCTET STRING -- always of length ceil(log2(n)/8)
*/
static int pk_write_ec_privkey( unsigned char **p, unsigned char *start,
mbedtls_pk_context const *key )
{
int ret;
mbedtls_ecp_keypair const * const ec = mbedtls_pk_ec( *key );
return( mbedtls_asn1_write_mpi( p, start, &ec->d ) );
size_t byte_length = ( ec->grp.pbits + 7 ) / 8;
unsigned char tmp[MBEDTLS_ECP_MAX_BYTES];
ret = mbedtls_mpi_write_binary( &ec->d, tmp, byte_length );
if( ret != 0 )
goto exit;
ret = mbedtls_asn1_write_octet_string( p, start, tmp, byte_length );
exit:
mbedtls_platform_zeroize( tmp, byte_length );
return( ret );
}
/*
@ -212,25 +229,6 @@ static int pk_write_ec_param( unsigned char **p, unsigned char *start,
return( (int) len );
}
/*
* privateKey OCTET STRING -- always of length ceil(log2(n)/8)
*/
static int pk_write_ec_private( unsigned char **p, unsigned char *start,
mbedtls_ecp_keypair *ec )
{
int ret;
size_t byte_length = ( ec->grp.pbits + 7 ) / 8;
unsigned char tmp[MBEDTLS_ECP_MAX_BYTES];
ret = mbedtls_mpi_write_binary( &ec->d, tmp, byte_length );
if( ret != 0 )
goto exit;
ret = mbedtls_asn1_write_octet_string( p, start, tmp, byte_length );
exit:
mbedtls_platform_zeroize( tmp, byte_length );
return( ret );
}
#endif /* MBEDTLS_ECP_C */
#endif /* MBEDTLS_USE_TINYCRYPT */
@ -445,9 +443,8 @@ int mbedtls_pk_write_key_der( mbedtls_pk_context *key, unsigned char *buf, size_
MBEDTLS_ASN1_CONTEXT_SPECIFIC | MBEDTLS_ASN1_CONSTRUCTED | 0 ) );
len += par_len;
/* privateKey: write as MPI then fix tag */
/* privateKey */
MBEDTLS_ASN1_CHK_ADD( len, pk_write_ec_privkey( &c, buf, key ) );
*c = MBEDTLS_ASN1_OCTET_STRING;
/* version */
MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_int( &c, buf, 1 ) );