From 62e33bcc64c05027a5873830b7a26dbdbb84f282 Mon Sep 17 00:00:00 2001 From: Gilles Peskine Date: Thu, 22 Jun 2023 22:27:32 +0200 Subject: [PATCH] New function mbedtls_ecp_write_public_key Directly export the public part of a key pair without having to go through intermediate objects (using mbedtls_ecp_point_write_binary would require a group object and a point object). Signed-off-by: Gilles Peskine --- include/mbedtls/ecp.h | 26 ++++++++++++++++++++++++ library/ecp.c | 12 +++++++++++ tests/suites/test_suite_ecp.function | 30 +++++++++++++++++++--------- 3 files changed, 59 insertions(+), 9 deletions(-) diff --git a/include/mbedtls/ecp.h b/include/mbedtls/ecp.h index fc0a7636b..619a8a51a 100644 --- a/include/mbedtls/ecp.h +++ b/include/mbedtls/ecp.h @@ -1346,6 +1346,32 @@ int mbedtls_ecp_read_key(mbedtls_ecp_group_id grp_id, mbedtls_ecp_keypair *key, int mbedtls_ecp_write_key(mbedtls_ecp_keypair *key, unsigned char *buf, size_t buflen); +/** + * \brief This function exports an elliptic curve public key. + * + * \param key The public key. + * \param format The point format. This must be either + * #MBEDTLS_ECP_PF_COMPRESSED or #MBEDTLS_ECP_PF_UNCOMPRESSED. + * (For groups without these formats, this parameter is + * ignored. But it still has to be either of the above + * values.) + * \param olen The address at which to store the length of + * the output in Bytes. This must not be \c NULL. + * \param buf The output buffer. This must be a writable buffer + * of length \p buflen Bytes. + * \param buflen The length of the output buffer \p buf in Bytes. + * + * \return \c 0 on success. + * \return #MBEDTLS_ERR_ECP_BUFFER_TOO_SMALL if the output buffer + * is too small to hold the point. + * \return #MBEDTLS_ERR_ECP_FEATURE_UNAVAILABLE if the point format + * or the export for the given group is not implemented. + * \return Another negative error code on other kinds of failure. + */ +int mbedtls_ecp_write_public_key(mbedtls_ecp_keypair *key, + int format, 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 43f7d6930..12924bf32 100644 --- a/library/ecp.c +++ b/library/ecp.c @@ -3333,6 +3333,18 @@ cleanup: return ret; } +/* + * Write a public key. + */ +int mbedtls_ecp_write_public_key(mbedtls_ecp_keypair *key, + int format, size_t *olen, + unsigned char *buf, size_t buflen) +{ + return mbedtls_ecp_point_write_binary(&key->grp, &key->Q, + format, olen, buf, buflen); +} + + #if defined(MBEDTLS_ECP_C) /* * Check a public-private key pair diff --git a/tests/suites/test_suite_ecp.function b/tests/suites/test_suite_ecp.function index 354a92cec..ced4ca387 100644 --- a/tests/suites/test_suite_ecp.function +++ b/tests/suites/test_suite_ecp.function @@ -590,29 +590,41 @@ void ecp_write_binary(int id, char *x, char *y, char *z, int format, { mbedtls_ecp_group grp; mbedtls_ecp_point P; + mbedtls_ecp_keypair key; unsigned char buf[256]; size_t olen; memset(buf, 0, sizeof(buf)); mbedtls_ecp_group_init(&grp); mbedtls_ecp_point_init(&P); + mbedtls_ecp_keypair_init(&key); - TEST_ASSERT(mbedtls_ecp_group_load(&grp, id) == 0); + TEST_EQUAL(mbedtls_ecp_group_load(&grp, id), 0); - TEST_ASSERT(mbedtls_test_read_mpi(&P.X, x) == 0); - TEST_ASSERT(mbedtls_test_read_mpi(&P.Y, y) == 0); - TEST_ASSERT(mbedtls_test_read_mpi(&P.Z, z) == 0); - - TEST_ASSERT(mbedtls_ecp_point_write_binary(&grp, &P, format, - &olen, buf, blen) == ret); + TEST_EQUAL(mbedtls_test_read_mpi(&P.X, x), 0); + TEST_EQUAL(mbedtls_test_read_mpi(&P.Y, y), 0); + TEST_EQUAL(mbedtls_test_read_mpi(&P.Z, z), 0); + TEST_EQUAL(mbedtls_ecp_point_write_binary(&grp, &P, format, + &olen, buf, blen), ret); if (ret == 0) { - TEST_ASSERT(olen <= MBEDTLS_ECP_MAX_PT_LEN); - TEST_ASSERT(mbedtls_test_hexcmp(buf, out->x, olen, out->len) == 0); + TEST_LE_U(olen, MBEDTLS_ECP_MAX_PT_LEN); + ASSERT_COMPARE(buf, olen, + out->x, out->len); + } + + memset(buf, 0, blen); + TEST_EQUAL(mbedtls_ecp_set_public_key(grp.id, &key, &P), 0); + TEST_EQUAL(mbedtls_ecp_write_public_key(&key, format, + &olen, buf, blen), ret); + if (ret == 0) { + ASSERT_COMPARE(buf, olen, + out->x, out->len); } exit: mbedtls_ecp_group_free(&grp); mbedtls_ecp_point_free(&P); + mbedtls_ecp_keypair_free(&key); } /* END_CASE */