gnutls: Backport fix for CVE-2024-0553

CVE-2024-0553
A vulnerability was found in GnuTLS. The response times to malformed ciphertexts in RSA-PSK ClientKeyExchange differ from response times of ciphertexts with correct PKCS#1 v1.5 padding. This issue may allow a remote attacker to perform a timing side-channel attack in the RSA-PSK key exchange, potentially leading to the leakage of sensitive data. CVE-2024-0553 is designated as an incomplete resolution for CVE-2023-5981.

Upstream-Status: Backport [https://gitlab.com/gnutls/gnutls/-/commit/40dbbd8de499668590e8af51a15799fbc430595e]

Signed-off-by: Vijay Anusuri <vanusuri@mvista.com>
Signed-off-by: Steve Sakoman <steve@sakoman.com>

2 files changed, 126 insertions, 0 deletions

diff --git a/meta/recipes-support/gnutls/gnutls/CVE-2024-0553.patch b/meta/recipes-support/gnutls/gnutls/CVE-2024-0553.patch
new file mode 100644
index 0000000000..f15c470879
--- /dev/null
+++ b/meta/recipes-support/gnutls/gnutls/CVE-2024-0553.patch
@@ -0,0 +1,125 @@
+From 40dbbd8de499668590e8af51a15799fbc430595e Mon Sep 17 00:00:00 2001
+From: Daiki Ueno <ueno@gnu.org>
+Date: Wed, 10 Jan 2024 19:13:17 +0900
+Subject: [PATCH] rsa-psk: minimize branching after decryption
+
+This moves any non-trivial code between gnutls_privkey_decrypt_data2
+and the function return in _gnutls_proc_rsa_psk_client_kx up until the
+decryption.  This also avoids an extra memcpy to session->key.key.
+
+Signed-off-by: Daiki Ueno <ueno@gnu.org>
+
+Upstream-Status: Backport [https://gitlab.com/gnutls/gnutls/-/commit/40dbbd8de499668590e8af51a15799fbc430595e]
+CVE: CVE-2024-0553
+Signed-off-by: Vijay Anusuri <vanusuri@mvista.com>
+---
+ lib/auth/rsa_psk.c | 68 ++++++++++++++++++++++++----------------------
+ 1 file changed, 35 insertions(+), 33 deletions(-)
+
+diff --git a/lib/auth/rsa_psk.c b/lib/auth/rsa_psk.c
+index 93c2dc9..c6cfb92 100644
+--- a/lib/auth/rsa_psk.c
++++ b/lib/auth/rsa_psk.c
+@@ -269,7 +269,6 @@ _gnutls_proc_rsa_psk_client_kx(gnutls_session_t session, uint8_t * data,
+ 	int ret, dsize;
+ 	ssize_t data_size = _data_size;
+ 	gnutls_psk_server_credentials_t cred;
+-	gnutls_datum_t premaster_secret = { NULL, 0 };
+ 	volatile uint8_t ver_maj, ver_min;
+ 
+ 	cred = (gnutls_psk_server_credentials_t)
+@@ -329,24 +328,48 @@ _gnutls_proc_rsa_psk_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);
+ 
+-	premaster_secret.data = gnutls_malloc(GNUTLS_MASTER_SIZE);
+-	if (premaster_secret.data == NULL) {
++	/* Find the key of this username. A random value will be
++	 * filled in if the key is not found.
++	 */
++	ret = _gnutls_psk_pwd_find_entry(session, info->username,
++			                 strlen(info->username), &pwd_psk);
++	if (ret < 0)
++		return gnutls_assert_val(ret);
++
++	/* Allocate memory for premaster secret, and fill in the
++	 * fields except the decryption result.
++	 */
++	session->key.key.size = 2 + GNUTLS_MASTER_SIZE + 2 + pwd_psk.size;
++	session->key.key.data = gnutls_malloc(session->key.key.size);
++	if (session->key.key.data == NULL) {
+ 		gnutls_assert();
++		_gnutls_free_key_datum(&pwd_psk);
++		/* No need to zeroize, as the secret is not copied in yet */
++		_gnutls_free_datum(&session->key.key);
+ 		return GNUTLS_E_MEMORY_ERROR;
+ 	}
+-	premaster_secret.size = GNUTLS_MASTER_SIZE;
+ 
+ 	/* Fallback value when decryption fails. Needs to be unpredictable. */
+-	ret = gnutls_rnd(GNUTLS_RND_NONCE, premaster_secret.data,
+-			 premaster_secret.size);
++	ret = gnutls_rnd(GNUTLS_RND_NONCE, session->key.key.data + 2,
++			 GNUTLS_MASTER_SIZE);
+ 	if (ret < 0) {
+ 		gnutls_assert();
+-		goto cleanup;
++		_gnutls_free_key_datum(&pwd_psk);
++		/* No need to zeroize, as the secret is not copied in yet */
++		_gnutls_free_datum(&session->key.key);
++		return ret;
+ 	}
+ 
++	_gnutls_write_uint16(GNUTLS_MASTER_SIZE, session->key.key.data);
++	_gnutls_write_uint16(pwd_psk.size,
++			     &session->key.key.data[2 + GNUTLS_MASTER_SIZE]);
++	memcpy(&session->key.key.data[2 + GNUTLS_MASTER_SIZE + 2], pwd_psk.data,
++	       pwd_psk.size);
++	_gnutls_free_key_datum(&pwd_psk);
++
+ 	gnutls_privkey_decrypt_data2(session->internals.selected_key, 0,
+-				     &ciphertext, premaster_secret.data,
+-				     premaster_secret.size);
++				     &ciphertext, session->key.key.data + 2,
++				     GNUTLS_MASTER_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 tread carefully */
+@@ -365,31 +388,10 @@ _gnutls_proc_rsa_psk_client_kx(gnutls_session_t session, uint8_t * data,
+ 	/* This is here to avoid the version check attack
+ 	 * discussed above.
+ 	 */
+-	premaster_secret.data[0] = ver_maj;
+-	premaster_secret.data[1] = ver_min;
++	session->key.key.data[2] = ver_maj;
++	session->key.key.data[3] = ver_min;
+ 
+-	/* find the key of this username
+-	 */
+-	ret =
+-	    _gnutls_psk_pwd_find_entry(session, info->username, strlen(info->username), &pwd_psk);
+-	if (ret < 0) {
+-		gnutls_assert();
+-		goto cleanup;
+-	}
+-
+-	ret =
+-	    set_rsa_psk_session_key(session, &pwd_psk, &premaster_secret);
+-	if (ret < 0) {
+-		gnutls_assert();
+-		goto cleanup;
+-	}
+-
+-	ret = 0;
+-      cleanup:
+-	_gnutls_free_key_datum(&pwd_psk);
+-	_gnutls_free_temp_key_datum(&premaster_secret);
+-
+-	return ret;
++	return 0;
+ }
+ 
+ static int
+-- 
+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 406f0b54c5..a1451daf2c 100644
--- a/meta/recipes-support/gnutls/gnutls_3.6.14.bb
+++ b/meta/recipes-support/gnutls/gnutls_3.6.14.bb
@@ -29,6 +29,7 @@ SRC_URI = "https://www.gnupg.org/ftp/gcrypt/gnutls/v${SHRT_VER}/gnutls-${PV}.tar
            file://CVE-2021-4209.patch \
            file://CVE-2023-0361.patch \
            file://CVE-2023-5981.patch \
+           file://CVE-2024-0553.patch \
 "
 
 SRC_URI[sha256sum] = "5630751adec7025b8ef955af4d141d00d252a985769f51b4059e5affa3d39d63"