From 898fb884b706aaeb283de4812340bb0bde8476dc Mon Sep 17 00:00:00 2001 From: Matt Caswell Date: Wed, 29 Nov 2017 14:04:01 +0000 Subject: [PATCH] Don't allow read/write after fatal error OpenSSL 1.0.2 (starting from version 1.0.2b) introduced an "error state" mechanism. The intent was that if a fatal error occurred during a handshake then OpenSSL would move into the error state and would immediately fail if you attempted to continue the handshake. This works as designed for the explicit handshake functions (SSL_do_handshake(), SSL_accept() and SSL_connect()), however due to a bug it does not work correctly if SSL_read() or SSL_write() is called directly. In that scenario, if the handshake fails then a fatal error will be returned in the initial function call. If SSL_read()/SSL_write() is subsequently called by the application for the same SSL object then it will succeed and the data is passed without being decrypted/encrypted directly from the SSL/TLS record layer. In order to exploit this issue an attacker would have to trick an application into behaving incorrectly by issuing an SSL_read()/SSL_write() after having already received a fatal error. Thanks to David Benjamin (Google) for reporting this issue and suggesting this fix. CVE-2017-3737 Reviewed-by: Rich Salz --- ssl/ssl.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/ssl/ssl.h b/ssl/ssl.h index 90aeb0ce4e..3cf96a239b 100644 --- a/ssl/ssl.h +++ b/ssl/ssl.h @@ -1727,7 +1727,7 @@ extern "C" { # define SSL_ST_BEFORE 0x4000 # define SSL_ST_OK 0x03 # define SSL_ST_RENEGOTIATE (0x04|SSL_ST_INIT) -# define SSL_ST_ERR 0x05 +# define SSL_ST_ERR (0x05|SSL_ST_INIT) # define SSL_CB_LOOP 0x01 # define SSL_CB_EXIT 0x02 -- 2.25.1