From 29ee67c205855e848a0a26e6d0e4f65b6b943e0a Mon Sep 17 00:00:00 2001 From: Daiki Ueno 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 --- ...a04b3d3f7dcc0ab4571cf0df3b67ab7e1005e9e7a8 | Bin 0 -> 671 bytes ...1da801fb3c6d1f7f846f227721e221adea08aa319c | Bin 0 -> 729 bytes lib/gnutls_int.h | 1 + lib/handshake.c | 48 +++++++++++++----- 4 files changed, 36 insertions(+), 13 deletions(-) create mode 100644 fuzz/gnutls_client_fuzzer.in/00ea40761ce11e769f1817a04b3d3f7dcc0ab4571cf0df3b67ab7e1005e9e7a8 create mode 100644 fuzz/gnutls_psk_client_fuzzer.in/b16434290b77e13d7a983d1da801fb3c6d1f7f846f227721e221adea08aa319c 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 @@ -2061,6 +2061,8 @@ 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; } @@ -2585,16 +2587,42 @@ 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; + } } @@ -2756,13 +2784,7 @@ 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 */ -- 2.26.2