From dda5c25e855fc4bff14df13bb6742bcff7fa9493 Mon Sep 17 00:00:00 2001 From: Pol Henarejos Date: Tue, 6 Sep 2022 21:35:23 +0200 Subject: [PATCH] Fix computing HMAC of key path. Signed-off-by: Pol Henarejos --- src/fido/cmd_authenticate.c | 7 +++++-- src/fido/fido.c | 13 +++++++++---- 2 files changed, 14 insertions(+), 6 deletions(-) diff --git a/src/fido/cmd_authenticate.c b/src/fido/cmd_authenticate.c index 8ba02ee..5b6db49 100644 --- a/src/fido/cmd_authenticate.c +++ b/src/fido/cmd_authenticate.c @@ -53,9 +53,12 @@ int cmd_authenticate() { mbedtls_ecdsa_free(&key); if (ret != 0) return SW_WRONG_DATA(); - ret = mbedtls_md_hmac(mbedtls_md_info_from_type(MBEDTLS_MD_SHA256), d, 32, req->appId, 32, hmac); + uint8_t key_base[U2F_APPID_SIZE + KEY_PATH_LEN]; + memcpy(key_base, req->appId, U2F_APPID_SIZE); + memcpy(key_base + U2F_APPID_SIZE, req->keyHandle, KEY_PATH_LEN); + ret = mbedtls_md_hmac(mbedtls_md_info_from_type(MBEDTLS_MD_SHA256), d, 32, key_base, sizeof(key_base), hmac); mbedtls_platform_zeroize(d, sizeof(d)); - if (memcmp(req->keyHandle + 32, hmac, sizeof(hmac)) != 0) + if (memcmp(req->keyHandle + KEY_HANDLE_LEN, hmac, sizeof(hmac)) != 0) return SW_WRONG_DATA(); return SW_CONDITIONS_NOT_SATISFIED(); } diff --git a/src/fido/fido.c b/src/fido/fido.c index 25e81be..c5498aa 100644 --- a/src/fido/fido.c +++ b/src/fido/fido.c @@ -111,10 +111,15 @@ int derive_key(const uint8_t *app_id, bool new_key, uint8_t *key_handle, mbedtls return r; } } - if (new_key == true && (r = mbedtls_md_hmac(mbedtls_md_info_from_type(MBEDTLS_MD_SHA256), outk, 32, app_id, 32, key_handle + 32)) != 0) - { - mbedtls_platform_zeroize(outk, sizeof(outk)); - return r; + if (new_key == true) { + uint8_t key_base[U2F_APPID_SIZE + KEY_PATH_LEN]; + memcpy(key_base, app_id, U2F_APPID_SIZE); + memcpy(key_base + U2F_APPID_SIZE, key_handle, KEY_PATH_LEN); + if ((r = mbedtls_md_hmac(mbedtls_md_info_from_type(MBEDTLS_MD_SHA256), outk, 32, key_base, sizeof(key_base), key_handle + 32)) != 0) + { + mbedtls_platform_zeroize(outk, sizeof(outk)); + return r; + } } if (key != NULL) { mbedtls_ecp_group_load(&key->grp, MBEDTLS_ECP_DP_SECP256R1);