Implement and test mbedtls_ecp_write_key
mbedtls_ecp_write_key is a mirror function to mbedtls_ecp_read_key, which
writes a private key back into a byte buffer in the correct format.
This is a helpful convenience function, since the byte order is defined
differently between Montgomery and Weierstrass curves. Since this difference
is accounted for in mbedtls_ecp_read_key, it made sense to add
mbedtls_ecp_write_key for the purpose of abstracting this away such that
psa_export_key doesn't need to take byte order into account.
Signed-off-by: Steven Cooreman <steven.cooreman@silabs.com>
diff --git a/include/mbedtls/ecp.h b/include/mbedtls/ecp.h
index 4c05b4f..9248fd3 100644
--- a/include/mbedtls/ecp.h
+++ b/include/mbedtls/ecp.h
@@ -1146,6 +1146,27 @@
*/
int mbedtls_ecp_read_key( mbedtls_ecp_group_id grp_id, mbedtls_ecp_keypair *key,
const unsigned char *buf, size_t buflen );
+
+/**
+ * \brief This function exports an elliptic curve private key.
+ *
+ * \param grp_id The ECP group identifier.
+ * \param key The private key.
+ * \param olen The amount of bytes written into the output buffer.
+ * \param buf The output buffer containing the binary representation of
+ * the key. (Big endian integer for Weierstrass curves, byte
+ * string for Montgomery curves.)
+ * \param buflen The total length of the buffer in bytes.
+ *
+ * \return \c 0 on success.
+ * \return #MBEDTLS_ERR_ECP_BUFFER_TOO_SMALL if key is larger than buffer.
+ * \return #MBEDTLS_ERR_ECP_FEATURE_UNAVAILABLE if the operation for
+ * the group is not implemented.
+ * \return Another negative error code on different kinds of failure.
+ */
+int mbedtls_ecp_write_key( mbedtls_ecp_group_id grp_id, mbedtls_ecp_keypair *key,
+ size_t *olen, unsigned char *buf, size_t buflen );
+
/**
* \brief This function checks that the keypair objects
* \p pub and \p prv have the same group and the
diff --git a/library/ecp.c b/library/ecp.c
index 104e1f1..0aa61f1 100644
--- a/library/ecp.c
+++ b/library/ecp.c
@@ -2997,6 +2997,53 @@
}
/*
+ * Write a private key.
+ */
+int mbedtls_ecp_write_key( mbedtls_ecp_group_id grp_id, mbedtls_ecp_keypair *key,
+ size_t *olen, unsigned char *buf, size_t buflen )
+{
+ int ret = 0;
+
+ ECP_VALIDATE_RET( key != NULL );
+ ECP_VALIDATE_RET( buf != NULL );
+ ECP_VALIDATE_RET( olen != NULL );
+
+ if( ( ret = mbedtls_ecp_group_load( &key->grp, grp_id ) ) != 0 )
+ return( ret );
+
+ ret = MBEDTLS_ERR_ECP_FEATURE_UNAVAILABLE;
+
+#if defined(ECP_MONTGOMERY)
+ if( mbedtls_ecp_get_type( &key->grp ) == MBEDTLS_ECP_TYPE_MONTGOMERY )
+ {
+ if( grp_id == MBEDTLS_ECP_DP_CURVE25519 )
+ {
+ if( buflen < ECP_CURVE25519_KEY_SIZE )
+ return MBEDTLS_ERR_ECP_BUFFER_TOO_SMALL;
+
+ MBEDTLS_MPI_CHK( mbedtls_mpi_write_binary_le( &key->d, buf, buflen ) );
+ *olen = ECP_CURVE25519_KEY_SIZE;
+ }
+ else
+ ret = MBEDTLS_ERR_ECP_FEATURE_UNAVAILABLE;
+ }
+
+#endif
+#if defined(ECP_SHORTWEIERSTRASS)
+ if( mbedtls_ecp_get_type( &key->grp ) == MBEDTLS_ECP_TYPE_SHORT_WEIERSTRASS )
+ {
+ MBEDTLS_MPI_CHK( mbedtls_mpi_write_binary( &key->d, buf, buflen ) );
+ *olen = mbedtls_mpi_size( &key->d );
+ }
+
+#endif
+cleanup:
+
+ return( ret );
+}
+
+
+/*
* Check a public-private key pair
*/
int mbedtls_ecp_check_pub_priv( const mbedtls_ecp_keypair *pub, const mbedtls_ecp_keypair *prv )
diff --git a/tests/suites/test_suite_ecp.data b/tests/suites/test_suite_ecp.data
index 9219179..c180d37 100644
--- a/tests/suites/test_suite_ecp.data
+++ b/tests/suites/test_suite_ecp.data
@@ -278,65 +278,69 @@
ECP read key #1 (short weierstrass, too small)
depends_on:MBEDTLS_ECP_DP_SECP192R1_ENABLED
-mbedtls_ecp_read_key:MBEDTLS_ECP_DP_SECP192R1:"00":MBEDTLS_ERR_ECP_INVALID_KEY
+mbedtls_ecp_read_key:MBEDTLS_ECP_DP_SECP192R1:"00":MBEDTLS_ERR_ECP_INVALID_KEY:0
ECP read key #2 (short weierstrass, smallest)
depends_on:MBEDTLS_ECP_DP_SECP192R1_ENABLED
-mbedtls_ecp_read_key:MBEDTLS_ECP_DP_SECP192R1:"01":0
+mbedtls_ecp_read_key:MBEDTLS_ECP_DP_SECP192R1:"01":0:1
ECP read key #3 (short weierstrass, biggest)
depends_on:MBEDTLS_ECP_DP_SECP192R1_ENABLED
-mbedtls_ecp_read_key:MBEDTLS_ECP_DP_SECP192R1:"FFFFFFFFFFFFFFFFFFFFFFFF99DEF836146BC9B1B4D22830":0
+mbedtls_ecp_read_key:MBEDTLS_ECP_DP_SECP192R1:"FFFFFFFFFFFFFFFFFFFFFFFF99DEF836146BC9B1B4D22830":0:1
ECP read key #4 (short weierstrass, too big)
depends_on:MBEDTLS_ECP_DP_SECP192R1_ENABLED
-mbedtls_ecp_read_key:MBEDTLS_ECP_DP_SECP192R1:"FFFFFFFFFFFFFFFFFFFFFFFF99DEF836146BC9B1B4D22831":MBEDTLS_ERR_ECP_INVALID_KEY
+mbedtls_ecp_read_key:MBEDTLS_ECP_DP_SECP192R1:"FFFFFFFFFFFFFFFFFFFFFFFF99DEF836146BC9B1B4D22831":MBEDTLS_ERR_ECP_INVALID_KEY:0
ECP read key #5 (Curve25519, most significant bit set)
depends_on:MBEDTLS_ECP_DP_CURVE25519_ENABLED
-mbedtls_ecp_read_key:MBEDTLS_ECP_DP_CURVE25519:"000000000000000000000000000000000000000000000000000000000000000C":0
+mbedtls_ecp_read_key:MBEDTLS_ECP_DP_CURVE25519:"000000000000000000000000000000000000000000000000000000000000000C":0:0
ECP read key #6 (Curve25519, second most significant bit unset)
depends_on:MBEDTLS_ECP_DP_CURVE25519_ENABLED
-mbedtls_ecp_read_key:MBEDTLS_ECP_DP_CURVE25519:"0FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF3":0
+mbedtls_ecp_read_key:MBEDTLS_ECP_DP_CURVE25519:"0FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF3":0:0
ECP read key #7 (Curve25519, msb OK)
depends_on:MBEDTLS_ECP_DP_CURVE25519_ENABLED
-mbedtls_ecp_read_key:MBEDTLS_ECP_DP_CURVE25519:"0000000000000000000000000000000000000000000000000000000000000004":0
+mbedtls_ecp_read_key:MBEDTLS_ECP_DP_CURVE25519:"0000000000000000000000000000000000000000000000000000000000000004":0:1
ECP read key #8 (Curve25519, bit 0 set)
depends_on:MBEDTLS_ECP_DP_CURVE25519_ENABLED
-mbedtls_ecp_read_key:MBEDTLS_ECP_DP_CURVE25519:"1000000000000000000000000000000000000000000000000000000000000000":0
+mbedtls_ecp_read_key:MBEDTLS_ECP_DP_CURVE25519:"1000000000000000000000000000000000000000000000000000000000000000":0:0
ECP read key #9 (Curve25519, bit 1 set)
depends_on:MBEDTLS_ECP_DP_CURVE25519_ENABLED
-mbedtls_ecp_read_key:MBEDTLS_ECP_DP_CURVE25519:"2000000000000000000000000000000000000000000000000000000000000004":0
+mbedtls_ecp_read_key:MBEDTLS_ECP_DP_CURVE25519:"2000000000000000000000000000000000000000000000000000000000000004":0:0
ECP read key #10 (Curve25519, bit 2 set)
depends_on:MBEDTLS_ECP_DP_CURVE25519_ENABLED
-mbedtls_ecp_read_key:MBEDTLS_ECP_DP_CURVE25519:"4000000000000000000000000000000000000000000000000000000000000004":0
+mbedtls_ecp_read_key:MBEDTLS_ECP_DP_CURVE25519:"4000000000000000000000000000000000000000000000000000000000000004":0:0
ECP read key #11 (Curve25519, OK)
depends_on:MBEDTLS_ECP_DP_CURVE25519_ENABLED
-mbedtls_ecp_read_key:MBEDTLS_ECP_DP_CURVE25519:"8FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF7":0
+mbedtls_ecp_read_key:MBEDTLS_ECP_DP_CURVE25519:"8FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF7":0:1
ECP read key #12 (Curve25519, too long)
depends_on:MBEDTLS_ECP_DP_CURVE25519_ENABLED
-mbedtls_ecp_read_key:MBEDTLS_ECP_DP_CURVE25519:"00000000000000000000000000000000000000000000000000000000000000000C":MBEDTLS_ERR_ECP_INVALID_KEY
+mbedtls_ecp_read_key:MBEDTLS_ECP_DP_CURVE25519:"00000000000000000000000000000000000000000000000000000000000000000C":MBEDTLS_ERR_ECP_INVALID_KEY:0
ECP read key #13 (Curve25519, not long enough)
depends_on:MBEDTLS_ECP_DP_CURVE25519_ENABLED
-mbedtls_ecp_read_key:MBEDTLS_ECP_DP_CURVE25519:"0FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF3":MBEDTLS_ERR_ECP_INVALID_KEY
+mbedtls_ecp_read_key:MBEDTLS_ECP_DP_CURVE25519:"0FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF3":MBEDTLS_ERR_ECP_INVALID_KEY:0
ECP read key #14 (Curve448, not supported)
-mbedtls_ecp_read_key:MBEDTLS_ECP_DP_CURVE448:"FCFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF":MBEDTLS_ERR_ECP_FEATURE_UNAVAILABLE
+mbedtls_ecp_read_key:MBEDTLS_ECP_DP_CURVE448:"FCFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF":MBEDTLS_ERR_ECP_FEATURE_UNAVAILABLE:0
ECP read key #15 (Curve25519, not supported)
depends_on:!MBEDTLS_ECP_DP_CURVE25519_ENABLED
-mbedtls_ecp_read_key:MBEDTLS_ECP_DP_CURVE25519:"8FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF7":MBEDTLS_ERR_ECP_FEATURE_UNAVAILABLE
+mbedtls_ecp_read_key:MBEDTLS_ECP_DP_CURVE25519:"8FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF7":MBEDTLS_ERR_ECP_FEATURE_UNAVAILABLE:0
ECP read key #15 (invalid curve)
-mbedtls_ecp_read_key:INT_MAX:"8FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF7":MBEDTLS_ERR_ECP_FEATURE_UNAVAILABLE
+mbedtls_ecp_read_key:INT_MAX:"8FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF7":MBEDTLS_ERR_ECP_FEATURE_UNAVAILABLE:0
+
+ECP read key #16 (Curve25519 RFC, OK)
+depends_on:MBEDTLS_ECP_DP_CURVE25519_ENABLED
+mbedtls_ecp_read_key:MBEDTLS_ECP_DP_CURVE25519:"70076d0a7318a57d3c16c17251b26645df4c2f87ebc0992ab177fba51db92c6a":0:1
ECP mod p192 small (more than 192 bits, less limbs than 2 * 192 bits)
depends_on:MBEDTLS_ECP_DP_SECP192R1_ENABLED
diff --git a/tests/suites/test_suite_ecp.function b/tests/suites/test_suite_ecp.function
index 03c3e53..1a464ec 100644
--- a/tests/suites/test_suite_ecp.function
+++ b/tests/suites/test_suite_ecp.function
@@ -1069,12 +1069,14 @@
/* END_CASE */
/* BEGIN_CASE */
-void mbedtls_ecp_read_key( int grp_id, data_t* in_key, int expected )
+void mbedtls_ecp_read_key( int grp_id, data_t* in_key, int expected, int canonical )
{
int ret = 0;
mbedtls_ecp_keypair key;
+ mbedtls_ecp_keypair key2;
mbedtls_ecp_keypair_init( &key );
+ mbedtls_ecp_keypair_init( &key2 );
ret = mbedtls_ecp_read_key( grp_id, &key, in_key->x, in_key->len );
TEST_ASSERT( ret == expected );
@@ -1083,10 +1085,52 @@
{
ret = mbedtls_ecp_check_privkey( &key.grp, &key.d );
TEST_ASSERT( ret == 0 );
+
+ if( canonical )
+ {
+ unsigned char buf[MBEDTLS_ECP_MAX_BYTES];
+ size_t olen;
+
+ ret = mbedtls_ecp_write_key( grp_id, &key, &olen, buf, in_key->len );
+ TEST_ASSERT( ret == 0 );
+
+ TEST_ASSERT( olen == in_key->len );
+
+ mbedtls_fprintf( stdout, "written key: ");
+ for( size_t i = 0; i < in_key->len; i++ ) {
+ mbedtls_fprintf( stdout, "%02x", buf[i]);
+ }
+ mbedtls_fprintf( stdout, "\n");
+ ASSERT_COMPARE( in_key->x, in_key->len,
+ buf, olen );
+ }
+ else
+ {
+ unsigned char export1[MBEDTLS_ECP_MAX_BYTES];
+ size_t olen1;
+
+ unsigned char export2[MBEDTLS_ECP_MAX_BYTES];
+ size_t olen2;
+
+ ret = mbedtls_ecp_write_key( grp_id, &key, &olen1, export1, in_key->len );
+ TEST_ASSERT( ret == 0 );
+
+ ret = mbedtls_ecp_read_key( grp_id, &key2, export1, in_key->len );
+ TEST_ASSERT( ret == expected );
+
+ ret = mbedtls_ecp_write_key( grp_id, &key2, &olen2, export2, in_key->len );
+ TEST_ASSERT( ret == 0 );
+
+ TEST_ASSERT( olen2 == olen1 );
+
+ ASSERT_COMPARE( export1, olen1,
+ export2, olen2 );
+ }
}
exit:
mbedtls_ecp_keypair_free( &key );
+ mbedtls_ecp_keypair_free( &key2 );
}
/* END_CASE */