From f764d485547e69c9bf4e851bdda853ccebcdfaac Mon Sep 17 00:00:00 2001 From: Daiki Ueno Date: Fri, 10 Feb 2023 15:10:06 +0900 Subject: [PATCH] Fix timing side-channel in TLS RSA key exchange Resolves: #2162601 Signed-off-by: Daiki Ueno --- gnutls-3.7.8-rsa-kx-timing.patch | 114 +++++++++++++++++++++++++++++++ gnutls.spec | 6 +- 2 files changed, 119 insertions(+), 1 deletion(-) create mode 100644 gnutls-3.7.8-rsa-kx-timing.patch diff --git a/gnutls-3.7.8-rsa-kx-timing.patch b/gnutls-3.7.8-rsa-kx-timing.patch new file mode 100644 index 0000000..9107321 --- /dev/null +++ b/gnutls-3.7.8-rsa-kx-timing.patch @@ -0,0 +1,114 @@ +From c149dd0767f32789e391280cb1eb06b7eb7c6bce Mon Sep 17 00:00:00 2001 +From: Alexander Sosedkin +Date: Tue, 9 Aug 2022 16:05:53 +0200 +Subject: [PATCH 1/2] auth/rsa: side-step potential side-channel + +Remove branching that depends on secret data. + +Signed-off-by: Alexander Sosedkin +Signed-off-by: Hubert Kario +Tested-by: Hubert Kario +--- + lib/auth/rsa.c | 10 ---------- + 1 file changed, 10 deletions(-) + +diff --git a/lib/auth/rsa.c b/lib/auth/rsa.c +index 8108ee841d..6b158bacb2 100644 +--- a/lib/auth/rsa.c ++++ b/lib/auth/rsa.c +@@ -155,7 +155,6 @@ static int + proc_rsa_client_kx(gnutls_session_t session, uint8_t * data, + size_t _data_size) + { +- const char attack_error[] = "auth_rsa: Possible PKCS #1 attack\n"; + gnutls_datum_t ciphertext; + int ret, dsize; + ssize_t data_size = _data_size; +@@ -235,15 +234,6 @@ proc_rsa_client_kx(gnutls_session_t session, uint8_t * data, + ok &= CONSTCHECK_NOT_EQUAL(check_ver_min, 0) & + CONSTCHECK_EQUAL(session->key.key.data[1], ver_min); + +- if (ok) { +- /* call logging function unconditionally so all branches are +- * indistinguishable for timing and cache access when debug +- * logging is disabled */ +- _gnutls_no_log("%s", attack_error); +- } else { +- _gnutls_debug_log("%s", attack_error); +- } +- + /* This is here to avoid the version check attack + * discussed above. + */ +-- +2.39.1 + + +From 7c963102ec2119eecc1789b993aabe5edfd75f3b Mon Sep 17 00:00:00 2001 +From: Hubert Kario +Date: Wed, 8 Feb 2023 14:32:09 +0100 +Subject: [PATCH 2/2] rsa: remove dead code + +since the `ok` variable isn't used any more, we can remove all code +used to calculate it + +Signed-off-by: Hubert Kario +--- + lib/auth/rsa.c | 20 +++----------------- + 1 file changed, 3 insertions(+), 17 deletions(-) + +diff --git a/lib/auth/rsa.c b/lib/auth/rsa.c +index 6b158bacb2..858701fe6e 100644 +--- a/lib/auth/rsa.c ++++ b/lib/auth/rsa.c +@@ -159,8 +159,6 @@ proc_rsa_client_kx(gnutls_session_t session, uint8_t * data, + int ret, dsize; + ssize_t data_size = _data_size; + volatile uint8_t ver_maj, ver_min; +- volatile uint8_t check_ver_min; +- volatile uint32_t ok; + + #ifdef ENABLE_SSL3 + if (get_num_version(session) == GNUTLS_SSL3) { +@@ -186,7 +184,6 @@ proc_rsa_client_kx(gnutls_session_t session, uint8_t * data, + + ver_maj = _gnutls_get_adv_version_major(session); + ver_min = _gnutls_get_adv_version_minor(session); +- check_ver_min = (session->internals.allow_wrong_pms == 0); + + session->key.key.data = gnutls_malloc(GNUTLS_MASTER_SIZE); + if (session->key.key.data == NULL) { +@@ -205,10 +202,9 @@ proc_rsa_client_kx(gnutls_session_t session, uint8_t * data, + return ret; + } + +- ret = +- gnutls_privkey_decrypt_data2(session->internals.selected_key, +- 0, &ciphertext, session->key.key.data, +- session->key.key.size); ++ gnutls_privkey_decrypt_data2(session->internals.selected_key, ++ 0, &ciphertext, session->key.key.data, ++ session->key.key.size); + /* After this point, any conditional on failure that cause differences + * in execution may create a timing or cache access pattern side + * channel that can be used as an oracle, so treat very carefully */ +@@ -224,16 +220,6 @@ proc_rsa_client_kx(gnutls_session_t session, uint8_t * data, + * Vlastimil Klima, Ondej Pokorny and Tomas Rosa. + */ + +- /* ok is 0 in case of error and 1 in case of success. */ +- +- /* if ret < 0 */ +- ok = CONSTCHECK_EQUAL(ret, 0); +- /* session->key.key.data[0] must equal ver_maj */ +- ok &= CONSTCHECK_EQUAL(session->key.key.data[0], ver_maj); +- /* if check_ver_min then session->key.key.data[1] must equal ver_min */ +- ok &= CONSTCHECK_NOT_EQUAL(check_ver_min, 0) & +- CONSTCHECK_EQUAL(session->key.key.data[1], ver_min); +- + /* This is here to avoid the version check attack + * discussed above. + */ +-- +2.39.1 + diff --git a/gnutls.spec b/gnutls.spec index 55ae020..d4586a4 100644 --- a/gnutls.spec +++ b/gnutls.spec @@ -13,7 +13,7 @@ print(string.sub(hash, 0, 16)) } Version: 3.7.6 -Release: 16%{?dist} +Release: 17%{?dist} # not upstreamed Patch: gnutls-3.6.7-no-now-guile.patch Patch: gnutls-3.2.7-rpath.patch @@ -38,6 +38,7 @@ Patch: gnutls-3.7.6-fips-service-indicator-test-functions.patch Patch: gnutls-3.7.6-fips-ccm-taglen.patch Patch: gnutls-3.7.6-fips-rsa-pss-saltlen.patch Patch: gnutls-3.7.8-revert-hmac-name.patch +Patch: gnutls-3.7.8-rsa-kx-timing.patch # not upstreamed Patch: gnutls-3.7.3-disable-config-reload.patch @@ -405,6 +406,9 @@ make check %{?_smp_mflags} GNUTLS_SYSTEM_PRIORITY_FILE=/dev/null %endif %changelog +* Fri Feb 10 2023 Daiki Ueno - 3.7.6-17 +- Fix timing side-channel in TLS RSA key exchange (#2162601) + * Fri Feb 10 2023 Daiki Ueno - 3.7.6-16 - fips: extend PCT to DH key generation (#2168143)