| From 29ee67c205855e848a0a26e6d0e4f65b6b943e0a Mon Sep 17 00:00:00 2001 |
| From: Daiki Ueno <ueno@gnu.org> |
| Date: Sat, 22 Aug 2020 17:19:39 +0200 |
| Subject: [PATCH] handshake: reject no_renegotiation alert if handshake is |
| incomplete |
| |
| If the initial handshake is incomplete and the server sends a |
| no_renegotiation alert, the client should treat it as a fatal error |
| even if its level is warning. Otherwise the same handshake |
| state (e.g., DHE parameters) are reused in the next gnutls_handshake |
| call, if it is called in the loop idiom: |
| |
| do { |
| ret = gnutls_handshake(session); |
| } while (ret < 0 && gnutls_error_is_fatal(ret) == 0); |
| |
| Signed-off-by: Daiki Ueno <ueno@gnu.org> |
| CVE: CVE-2020-24659 |
| Upstream-Status: Backport [https://gitlab.com/gnutls/gnutls.git] |
| Signed-off-by: Zhixiong Chi <zhixiong.chi@windriver.com> |
| --- |
| lib/gnutls_int.h | 1 + |
| lib/handshake.c | 48 +++++++++++++----- |
| 2 files changed, 36 insertions(+), 13 deletions(-) |
| |
| diff --git a/lib/gnutls_int.h b/lib/gnutls_int.h |
| index bb6c19713..31cec5c0c 100644 |
| --- a/lib/gnutls_int.h |
| +++ b/lib/gnutls_int.h |
| @@ -1370,6 +1370,7 @@ typedef struct { |
| #define HSK_RECORD_SIZE_LIMIT_RECEIVED (1<<26) /* server: record_size_limit extension was seen but not accepted yet */ |
| #define HSK_OCSP_REQUESTED (1<<27) /* server: client requested OCSP stapling */ |
| #define HSK_CLIENT_OCSP_REQUESTED (1<<28) /* client: server requested OCSP stapling */ |
| +#define HSK_SERVER_HELLO_RECEIVED (1<<29) /* client: Server Hello message has been received */ |
| |
| /* The hsk_flags are for use within the ongoing handshake; |
| * they are reset to zero prior to handshake start by gnutls_handshake. */ |
| diff --git a/lib/handshake.c b/lib/handshake.c |
| index b40f84b3d..ce2d160e2 100644 |
| --- a/lib/handshake.c |
| +++ b/lib/handshake.c |
| @@ -2051,6 +2051,8 @@ read_server_hello(gnutls_session_t session, |
| if (ret < 0) |
| return gnutls_assert_val(ret); |
| |
| + session->internals.hsk_flags |= HSK_SERVER_HELLO_RECEIVED; |
| + |
| return 0; |
| } |
| |
| @@ -2575,16 +2577,42 @@ int gnutls_rehandshake(gnutls_session_t session) |
| return 0; |
| } |
| |
| +/* This function checks whether the error code should be treated fatal |
| + * or not, and also does the necessary state transition. In |
| + * particular, in the case of a rehandshake abort it resets the |
| + * handshake's internal state. |
| + */ |
| inline static int |
| _gnutls_abort_handshake(gnutls_session_t session, int ret) |
| { |
| - if (((ret == GNUTLS_E_WARNING_ALERT_RECEIVED) && |
| - (gnutls_alert_get(session) == GNUTLS_A_NO_RENEGOTIATION)) |
| - || ret == GNUTLS_E_GOT_APPLICATION_DATA) |
| - return 0; |
| + switch (ret) { |
| + case GNUTLS_E_WARNING_ALERT_RECEIVED: |
| + if (gnutls_alert_get(session) == GNUTLS_A_NO_RENEGOTIATION) { |
| + /* The server always toleretes a "no_renegotiation" alert. */ |
| + if (session->security_parameters.entity == GNUTLS_SERVER) { |
| + STATE = STATE0; |
| + return ret; |
| + } |
| + |
| + /* The client should tolerete a "no_renegotiation" alert only if: |
| + * - the initial handshake has completed, or |
| + * - a Server Hello is not yet received |
| + */ |
| + if (session->internals.initial_negotiation_completed || |
| + !(session->internals.hsk_flags & HSK_SERVER_HELLO_RECEIVED)) { |
| + STATE = STATE0; |
| + return ret; |
| + } |
| |
| - /* this doesn't matter */ |
| - return GNUTLS_E_INTERNAL_ERROR; |
| + return gnutls_assert_val(GNUTLS_E_UNEXPECTED_PACKET); |
| + } |
| + return ret; |
| + case GNUTLS_E_GOT_APPLICATION_DATA: |
| + STATE = STATE0; |
| + return ret; |
| + default: |
| + return ret; |
| + } |
| } |
| |
| |
| @@ -2747,13 +2774,7 @@ int gnutls_handshake(gnutls_session_t session) |
| } |
| |
| if (ret < 0) { |
| - /* In the case of a rehandshake abort |
| - * we should reset the handshake's internal state. |
| - */ |
| - if (_gnutls_abort_handshake(session, ret) == 0) |
| - STATE = STATE0; |
| - |
| - return ret; |
| + return _gnutls_abort_handshake(session, ret); |
| } |
| |
| /* clear handshake buffer */ |
| -- |
| 2.17.0 |
| |