122 lines
4.1 KiB
Diff
122 lines
4.1 KiB
Diff
From fe912c5dba49dcecbd5c32bf8184e60a949af452 Mon Sep 17 00:00:00 2001
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From: Daiki Ueno <ueno@gnu.org>
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Date: Wed, 10 Jan 2024 19:13:17 +0900
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Subject: [PATCH] rsa-psk: minimize branching after decryption
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This moves any non-trivial code between gnutls_privkey_decrypt_data2
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and the function return in _gnutls_proc_rsa_psk_client_kx up until the
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decryption. This also avoids an extra memcpy to session->key.key.
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Signed-off-by: Daiki Ueno <ueno@gnu.org>
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---
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lib/auth/rsa_psk.c | 68 ++++++++++++++++++++++++----------------------
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1 file changed, 35 insertions(+), 33 deletions(-)
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diff --git a/lib/auth/rsa_psk.c b/lib/auth/rsa_psk.c
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index 93c2dc9998..8f3fe5a4bd 100644
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--- a/lib/auth/rsa_psk.c
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+++ b/lib/auth/rsa_psk.c
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@@ -269,7 +269,6 @@ _gnutls_proc_rsa_psk_client_kx(gnutls_session_t session, uint8_t * data,
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int ret, dsize;
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ssize_t data_size = _data_size;
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gnutls_psk_server_credentials_t cred;
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- gnutls_datum_t premaster_secret = { NULL, 0 };
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volatile uint8_t ver_maj, ver_min;
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cred = (gnutls_psk_server_credentials_t)
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@@ -329,24 +328,48 @@ _gnutls_proc_rsa_psk_client_kx(gnutls_session_t session, uint8_t * data,
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ver_maj = _gnutls_get_adv_version_major(session);
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ver_min = _gnutls_get_adv_version_minor(session);
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- premaster_secret.data = gnutls_malloc(GNUTLS_MASTER_SIZE);
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- if (premaster_secret.data == NULL) {
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+ /* Find the key of this username. A random value will be
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+ * filled in if the key is not found.
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+ */
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+ ret =
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+ _gnutls_psk_pwd_find_entry(session, info->username, strlen(info->username), &pwd_psk);
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+ if (ret < 0)
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+ return gnutls_assert_val(ret);
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+
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+ /* Allocate memory for premaster secret, and fill in the
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+ * fields except the decryption result.
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+ */
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+ session->key.key.size = 2 + GNUTLS_MASTER_SIZE + 2 + pwd_psk.size;
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+ session->key.key.data = gnutls_malloc(session->key.key.size);
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+ if (session->key.key.data == NULL) {
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gnutls_assert();
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+ _gnutls_free_key_datum(&pwd_psk);
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+ /* No need to zeroize, as the secret is not copied in yet */
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+ _gnutls_free_datum(&session->key.key);
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return GNUTLS_E_MEMORY_ERROR;
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}
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- premaster_secret.size = GNUTLS_MASTER_SIZE;
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/* Fallback value when decryption fails. Needs to be unpredictable. */
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- ret = gnutls_rnd(GNUTLS_RND_NONCE, premaster_secret.data,
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- premaster_secret.size);
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+ ret = gnutls_rnd(GNUTLS_RND_NONCE, session->key.key.data + 2,
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+ GNUTLS_MASTER_SIZE);
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if (ret < 0) {
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gnutls_assert();
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- goto cleanup;
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+ _gnutls_free_key_datum(&pwd_psk);
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+ /* No need to zeroize, as the secret is not copied in yet */
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+ _gnutls_free_datum(&session->key.key);
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+ return ret;
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}
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+ _gnutls_write_uint16(GNUTLS_MASTER_SIZE, session->key.key.data);
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+ _gnutls_write_uint16(pwd_psk.size,
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+ &session->key.key.data[2 + GNUTLS_MASTER_SIZE]);
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+ memcpy(&session->key.key.data[2 + GNUTLS_MASTER_SIZE + 2],
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+ pwd_psk.data, pwd_psk.size);
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+ _gnutls_free_key_datum(&pwd_psk);
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+
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gnutls_privkey_decrypt_data2(session->internals.selected_key, 0,
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- &ciphertext, premaster_secret.data,
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- premaster_secret.size);
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+ &ciphertext, session->key.key.data + 2,
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+ GNUTLS_MASTER_SIZE);
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/* After this point, any conditional on failure that cause differences
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* in execution may create a timing or cache access pattern side
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* channel that can be used as an oracle, so tread carefully */
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@@ -365,31 +388,10 @@ _gnutls_proc_rsa_psk_client_kx(gnutls_session_t session, uint8_t * data,
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/* This is here to avoid the version check attack
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* discussed above.
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*/
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- premaster_secret.data[0] = ver_maj;
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- premaster_secret.data[1] = ver_min;
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-
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- /* find the key of this username
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- */
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- ret =
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- _gnutls_psk_pwd_find_entry(session, info->username, strlen(info->username), &pwd_psk);
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- if (ret < 0) {
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- gnutls_assert();
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- goto cleanup;
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- }
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-
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- ret =
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- set_rsa_psk_session_key(session, &pwd_psk, &premaster_secret);
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- if (ret < 0) {
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- gnutls_assert();
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- goto cleanup;
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- }
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+ session->key.key.data[2] = ver_maj;
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+ session->key.key.data[3] = ver_min;
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- ret = 0;
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- cleanup:
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- _gnutls_free_key_datum(&pwd_psk);
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- _gnutls_free_temp_key_datum(&premaster_secret);
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-
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- return ret;
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+ return 0;
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}
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static int
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--
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2.43.0
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