gnutls: fix CVE-2023-0361 timing side-channel in the TLS RSA key exchange code

Remove branching that depends on secret data.

since the `ok` variable isn't used any more, we can remove all code
used to calculate it

Signed-off-by: Vivek Kumbhar <vkumbhar@mvista.com>
Signed-off-by: Steve Sakoman <steve@sakoman.com>

diff --git a/meta/recipes-support/gnutls/gnutls/CVE-2023-0361.patch b/meta/recipes-support/gnutls/gnutls/CVE-2023-0361.patch
new file mode 100644 (file)
index 0000000..943f4ca
--- /dev/null
+++ b/meta/recipes-support/gnutls/gnutls/CVE-2023-0361.patch
@@ -0,0 +1,85 @@
+From 80a6ce8ddb02477cd724cd5b2944791aaddb702a Mon Sep 17 00:00:00 2001
+From: Alexander Sosedkin <asosedkin@redhat.com>
+Date: Tue, 9 Aug 2022 16:05:53 +0200
+Subject: [PATCH] auth/rsa: side-step potential side-channel
+
+Signed-off-by: Alexander Sosedkin <asosedkin@redhat.com>
+Signed-off-by: Hubert Kario <hkario@redhat.com>
+Tested-by: Hubert Kario <hkario@redhat.com>
+Upstream-Status: Backport [https://gitlab.com/gnutls/gnutls/-/commit/80a6ce8ddb02477cd724cd5b2944791aaddb702a
+                           https://gitlab.com/gnutls/gnutls/-/commit/4b7ff428291c7ed77c6d2635577c83a43bbae558]
+CVE: CVE-2023-0361
+Signed-off-by: Vivek Kumbhar <vkumbhar@mvista.com>
+---
+ lib/auth/rsa.c | 30 +++---------------------------
+ 1 file changed, 3 insertions(+), 27 deletions(-)
+
+diff --git a/lib/auth/rsa.c b/lib/auth/rsa.c
+index 8108ee8..858701f 100644
+--- a/lib/auth/rsa.c
++++ b/lib/auth/rsa.c
+@@ -155,13 +155,10 @@ 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;
+       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) {
+@@ -187,7 +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) {
+@@ -206,10 +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 */
+@@ -225,25 +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);
+-
+-      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.
+        */
+--
+2.25.1
+

diff --git a/meta/recipes-support/gnutls/gnutls_3.6.14.bb b/meta/recipes-support/gnutls/gnutls_3.6.14.bb
index f1757871ce86c0ecb41613459720ecbe158c1333..0c3392d521b59f6c4573976ef064fb9a6c73220a 100644 (file)
--- a/meta/recipes-support/gnutls/gnutls_3.6.14.bb
+++ b/meta/recipes-support/gnutls/gnutls_3.6.14.bb
@@ -27,6 +27,7 @@ SRC_URI = "https://www.gnupg.org/ftp/gcrypt/gnutls/v${SHRT_VER}/gnutls-${PV}.tar
            file://CVE-2021-20232.patch \
            file://CVE-2022-2509.patch \
            file://CVE-2021-4209.patch \
+           file://CVE-2023-0361.patch \
 "
 
 SRC_URI[sha256sum] = "5630751adec7025b8ef955af4d141d00d252a985769f51b4059e5affa3d39d63"