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ECP: Write RFC5480 representation of a group/point

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New functions to write a representation of an elliptic curve group and
point according to X9.62 and RFC5480: ECParameters as OID and ECPoint
as octet string.
This commit is contained in:
Gilles Peskine 2017-11-10 15:21:12 +01:00 committed by Andrzej Kurek
parent e4cd2988d9
commit 420d7d9cbd
4 changed files with 173 additions and 0 deletions
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44
include/mbedtls/ecp.h
View file

@ -501,6 +501,50 @@ int mbedtls_ecp_tls_read_group( mbedtls_ecp_group *grp, const unsigned char **bu
int mbedtls_ecp_tls_write_group( const mbedtls_ecp_group *grp, size_t *olen,
unsigned char *buf, size_t blen );
#if defined(MBEDTLS_ASN1_WRITE_C) && defined(MBEDTLS_OID_C)
/**
* \brief Maximum size of the output of mbedtls_ecp_ansi_write_group
*/
#define MBEDTLS_OID_EC_GRP_MAX_SIZE 12
/**
* \brief Write the ANSI X9.62/RFC5480 OID ECParameters of a group
*
* The output is the group's OID wrapped as ASN.1.
*
* \param grp ECP group used
* \param buf Buffer to write to
* \param size Buffer size
*
* \return Number of bytes written to \c buf,
* or \c MBEDTLS_ERR_ECP_BUFFER_TOO_SMALL
* or \c MBEDTLS_ERR_OID_NOT_FOUND
*/
int mbedtls_ecp_ansi_write_group( const mbedtls_ecp_group *grp,
unsigned char *p, size_t size );
/**
* \brief Export a point in ANSI X9.62/RFC5480 ECPoint
*
* The output is the point wrapped as an ASN.1 octet string
* as defined in X9.62 and RFC 5480.
*
* \param ec ECP public key or key pair
* \param format Point format, should be a MBEDTLS_ECP_PF_XXX macro
* \param p Buffer to write to
* \param size Buffer size
*
* \return Number of bytes written to \c buf,
* or \c MBEDTLS_ERR_ECP_BUFFER_TOO_SMALL
* or \c MBEDTLS_ERR_ECP_BAD_INPUT_DATA
* or \c MBEDTLS_ERR_ASN1_BUF_TOO_SMALL
*/
int mbedtls_ecp_ansi_write_point( const mbedtls_ecp_keypair *ec,
int format,
unsigned char *p,
size_t size );
#endif /* defined(MBEDTLS_ASN1_WRITE_C) && defined(MBEDTLS_OID_C) */
/**
* \brief Multiplication by an integer: R = m * P
* (Not thread-safe to use same group in multiple threads)

51
library/ecp.c
View file

@ -2061,6 +2061,57 @@ cleanup:
return( ret );
}
#if defined(MBEDTLS_ASN1_WRITE_C) && defined(MBEDTLS_OID_C)
#include "mbedtls/asn1write.h"
#include "mbedtls/oid.h"
int mbedtls_ecp_ansi_write_group( const mbedtls_ecp_group *grp,
unsigned char *p,
size_t size )
{
const char *oid;
unsigned char *q;
size_t oid_length;
int ret;
ret = mbedtls_oid_get_oid_by_ec_grp( grp->id, &oid, &oid_length );
if( ret != 0 )
return( ret );
// Output is a TLV with len(T)=1, len(L)=1, V=OID
if( size < 2 + oid_length )
return( MBEDTLS_ERR_ECP_BUFFER_TOO_SMALL );
q = p + 2 + oid_length;
return( mbedtls_asn1_write_oid( &q, p, oid, oid_length ) );
}
int mbedtls_ecp_ansi_write_point( const mbedtls_ecp_keypair *ec,
int format,
unsigned char *p,
size_t size )
{
unsigned char *q;
size_t length;
size_t tl_size = 3; /* room for the OCTET_STRING tag and length */
int ret;
if( size < tl_size )
return( MBEDTLS_ERR_ECP_BUFFER_TOO_SMALL );
q = p + tl_size;
ret = mbedtls_ecp_point_write_binary( &ec->grp, &ec->Q,
format,
&length, q, size - 3 );
if( ret < 0 )
return( ret );
ret = mbedtls_asn1_write_len( &q, p, length );
if( ret < 0 )
return( ret );
ret = mbedtls_asn1_write_tag( &q, p, MBEDTLS_ASN1_OCTET_STRING );
if( ret < 0 )
return( ret );
length += tl_size - ( q - p );
if( q != p )
memmove( p, q, length );
return( length );
}
#endif /* defined(MBEDTLS_ASN1_WRITE_C) && defined(MBEDTLS_OID_C) */
#if defined(MBEDTLS_SELF_TEST)
/*

20
tests/suites/test_suite_ecp.data
View file

@ -30,6 +30,26 @@ ECP curve info #8
depends_on:MBEDTLS_ECP_DP_SECP192R1_ENABLED
mbedtls_ecp_curve_info:MBEDTLS_ECP_DP_SECP192R1:19:192:"secp192r1"
ECP write ECParameters OID secp192r1
depends_on:MBEDTLS_ASN1_WRITE_C:MBEDTLS_OID_C:MBEDTLS_ECP_DP_SECP192R1_ENABLED
ecp_ansi_write_group:MBEDTLS_ECP_DP_SECP192R1:"06082a8648ce3d030101"
ECP write ECParameters OID secp521r1
depends_on:MBEDTLS_ASN1_WRITE_C:MBEDTLS_OID_C:MBEDTLS_ECP_DP_SECP521R1_ENABLED
ecp_ansi_write_group:MBEDTLS_ECP_DP_SECP521R1:"06052b81040023"
ECP write ECParameters OID brainpoolP512r1
depends_on:MBEDTLS_ASN1_WRITE_C:MBEDTLS_OID_C:MBEDTLS_ECP_DP_BP512R1_ENABLED
ecp_ansi_write_group:MBEDTLS_ECP_DP_BP512R1:"06092b240303020801010d"
ECP write ECPoint octet string (uncompressed)
depends_on:MBEDTLS_ASN1_WRITE_C:MBEDTLS_OID_C:MBEDTLS_PK_PARSE_C:MBEDTLS_ECP_DP_SECP192R1_ENABLED
ecp_ansi_write_point:"data_files/ec_pub.der":MBEDTLS_ECP_PF_UNCOMPRESSED:"043104bc797db3ae7f08ec3d496b4fb411b3f620a558a501e0222d08cfe0dc8aec8b1a7bf24be92951cc5ba1bebb2474909ae0"
ECP write ECPoint octet string (compressed)
depends_on:MBEDTLS_ASN1_WRITE_C:MBEDTLS_OID_C:MBEDTLS_PK_PARSE_C:MBEDTLS_ECP_DP_SECP192R1_ENABLED
ecp_ansi_write_point:"data_files/ec_pub.der":MBEDTLS_ECP_PF_COMPRESSED:"041902bc797db3ae7f08ec3d496b4fb411b3f620a558a501e0222d"
ECP check pubkey Montgomery #1 (too big)
depends_on:MBEDTLS_ECP_DP_CURVE25519_ENABLED
ecp_check_pub:MBEDTLS_ECP_DP_CURVE25519:"010000000000000000000000000000000000000000000000000000000000000000":"0":"1":MBEDTLS_ERR_ECP_INVALID_KEY

58
tests/suites/test_suite_ecp.function
View file

@ -1,5 +1,6 @@
/* BEGIN_HEADER */
#include "mbedtls/ecp.h"
#include "mbedtls/pk.h"
#define ECP_PF_UNKNOWN -1
/* END_HEADER */
@ -412,6 +413,63 @@ exit:
}
/* END_CASE */
/* BEGIN_CASE depends_on:MBEDTLS_ASN1_WRITE_C:MBEDTLS_OID_C */
void ecp_ansi_write_group( int id, char *hex )
{
mbedtls_ecp_group grp;
unsigned char good[MBEDTLS_OID_EC_GRP_MAX_SIZE];
unsigned char tested[MBEDTLS_OID_EC_GRP_MAX_SIZE];
size_t good_len = unhexify( good, hex );
int ret = 0;
mbedtls_ecp_group_init( &grp );
TEST_ASSERT( mbedtls_ecp_group_load( &grp, id ) == 0 );
/* Positive test */
ret = mbedtls_ecp_ansi_write_group( &grp, tested, sizeof( tested ) );
TEST_ASSERT( ret >= 0 && good_len == (unsigned) ret );
TEST_ASSERT( memcmp( good, tested, good_len ) == 0 );
/* Buffer too small */
TEST_ASSERT( mbedtls_ecp_ansi_write_group( &grp, tested, good_len - 1 ) ==
MBEDTLS_ERR_ECP_BUFFER_TOO_SMALL );
exit:
mbedtls_ecp_group_free( &grp );
}
/* END_CASE */
/* BEGIN_CASE depends_on:MBEDTLS_ASN1_WRITE_C:MBEDTLS_OID_C:MBEDTLS_PK_PARSE_C:MBEDTLS_FS_IO */
void ecp_ansi_write_point( char *key_file, int format, char *good_hex )
{
unsigned char good_buf[1000];
unsigned char tested_buf[1000];
size_t good_len = unhexify( good_buf, good_hex );
mbedtls_pk_context pk;
int ret = 0;
mbedtls_pk_init( &pk );
TEST_ASSERT( mbedtls_pk_parse_public_keyfile( &pk, key_file ) == 0 );
/* Positive test */
ret = mbedtls_ecp_ansi_write_point( mbedtls_pk_ec( pk ), format,
tested_buf, sizeof( tested_buf ) );
TEST_ASSERT( ret >= 0 && good_len == (unsigned) ret );
TEST_ASSERT( memcmp( good_buf, tested_buf, good_len ) == 0 );
/* Buffer too small */
TEST_ASSERT( mbedtls_ecp_ansi_write_point( mbedtls_pk_ec( pk ), format,
tested_buf, good_len - 1 ) ==
MBEDTLS_ERR_ECP_BUFFER_TOO_SMALL );
exit:
if( ret >= 0 ) {
unsigned char out[999] = {0};
hexify( out, tested_buf, ret );
printf("== %s ==\n", out);
}
mbedtls_pk_free( &pk );
}
/* END_CASE */
/* BEGIN_CASE */
void mbedtls_ecp_check_privkey( int id, char *key_hex, int ret )
{