From 21c4b259598efe3ea8c834c1568e8b762be120c4 Mon Sep 17 00:00:00 2001 From: "Dr. Stephen Henson" Date: Wed, 4 Jan 2012 18:52:18 +0000 Subject: [PATCH] Only allow one SGC handshake restart for SSL/TLS. (CVE-2011-4619) --- CHANGES | 3 +++ ssl/s3_srvr.c | 10 ++++++++++ ssl/ssl.h | 2 ++ ssl/ssl3.h | 11 +++++++++++ ssl/ssl_err.c | 4 +++- 5 files changed, 29 insertions(+), 1 deletion(-) diff --git a/CHANGES b/CHANGES index a6672ed6fe..5e6fcbd6b3 100644 --- a/CHANGES +++ b/CHANGES @@ -3,6 +3,9 @@ _______________ Changes between 0.9.8r and 0.9.8s [xx XXX xxxx] + + *) Only allow one SGC handshake restart for SSL/TLS. (CVE-2011-4619) + [Adam Langley (Google)] *) Prevent malformed RFC3779 data triggering an assertion failure. Thanks to Andrew Chi, BBN Technologies, for discovering the flaw diff --git a/ssl/s3_srvr.c b/ssl/s3_srvr.c index 4850a9a957..f6102123d4 100644 --- a/ssl/s3_srvr.c +++ b/ssl/s3_srvr.c @@ -235,6 +235,7 @@ int ssl3_accept(SSL *s) } s->init_num=0; + s->s3->flags &= ~SSL3_FLAGS_SGC_RESTART_DONE; if (s->state != SSL_ST_RENEGOTIATE) { @@ -697,6 +698,14 @@ int ssl3_check_client_hello(SSL *s) int ok; long n; + /* We only allow the client to restart the handshake once per + * negotiation. */ + if (s->s3->flags & SSL3_FLAGS_SGC_RESTART_DONE) + { + SSLerr(SSL_F_SSL3_CHECK_CLIENT_HELLO, SSL_R_MULTIPLE_SGC_RESTARTS); + return -1; + } + /* this function is called when we really expect a Certificate message, * so permit appropriate message length */ n=s->method->ssl_get_message(s, @@ -725,6 +734,7 @@ int ssl3_check_client_hello(SSL *s) s->s3->tmp.ecdh = NULL; } #endif + s->s3->flags |= SSL3_FLAGS_SGC_RESTART_DONE; return 2; } return 1; diff --git a/ssl/ssl.h b/ssl/ssl.h index 7d4e46e916..590a369fa3 100644 --- a/ssl/ssl.h +++ b/ssl/ssl.h @@ -1739,6 +1739,7 @@ void ERR_load_SSL_strings(void); #define SSL_F_SSL3_CALLBACK_CTRL 233 #define SSL_F_SSL3_CHANGE_CIPHER_STATE 129 #define SSL_F_SSL3_CHECK_CERT_AND_ALGORITHM 130 +#define SSL_F_SSL3_CHECK_CLIENT_HELLO 292 #define SSL_F_SSL3_CLIENT_HELLO 131 #define SSL_F_SSL3_CONNECT 132 #define SSL_F_SSL3_CTRL 213 @@ -1974,6 +1975,7 @@ void ERR_load_SSL_strings(void); #define SSL_R_MISSING_TMP_RSA_KEY 172 #define SSL_R_MISSING_TMP_RSA_PKEY 173 #define SSL_R_MISSING_VERIFY_MESSAGE 174 +#define SSL_R_MULTIPLE_SGC_RESTARTS 325 #define SSL_R_NON_SSLV2_INITIAL_PACKET 175 #define SSL_R_NO_CERTIFICATES_RETURNED 176 #define SSL_R_NO_CERTIFICATE_ASSIGNED 177 diff --git a/ssl/ssl3.h b/ssl/ssl3.h index 2f579c253b..b9a85effa0 100644 --- a/ssl/ssl3.h +++ b/ssl/ssl3.h @@ -333,6 +333,17 @@ typedef struct ssl3_buffer_st #define SSL3_FLAGS_DELAY_CLIENT_FINISHED 0x0002 #define SSL3_FLAGS_POP_BUFFER 0x0004 #define TLS1_FLAGS_TLS_PADDING_BUG 0x0008 + +/* SSL3_FLAGS_SGC_RESTART_DONE is set when we + * restart a handshake because of MS SGC and so prevents us + * from restarting the handshake in a loop. It's reset on a + * renegotiation, so effectively limits the client to one restart + * per negotiation. This limits the possibility of a DDoS + * attack where the client handshakes in a loop using SGC to + * restart. Servers which permit renegotiation can still be + * effected, but we can't prevent that. + */ +#define SSL3_FLAGS_SGC_RESTART_DONE 0x0040 typedef struct ssl3_state_st { diff --git a/ssl/ssl_err.c b/ssl/ssl_err.c index 7eb52026e7..bd52c98a0d 100644 --- a/ssl/ssl_err.c +++ b/ssl/ssl_err.c @@ -1,6 +1,6 @@ /* ssl/ssl_err.c */ /* ==================================================================== - * Copyright (c) 1999-2008 The OpenSSL Project. All rights reserved. + * Copyright (c) 1999-2011 The OpenSSL Project. All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions @@ -137,6 +137,7 @@ static ERR_STRING_DATA SSL_str_functs[]= {ERR_FUNC(SSL_F_SSL3_CALLBACK_CTRL), "SSL3_CALLBACK_CTRL"}, {ERR_FUNC(SSL_F_SSL3_CHANGE_CIPHER_STATE), "SSL3_CHANGE_CIPHER_STATE"}, {ERR_FUNC(SSL_F_SSL3_CHECK_CERT_AND_ALGORITHM), "SSL3_CHECK_CERT_AND_ALGORITHM"}, +{ERR_FUNC(SSL_F_SSL3_CHECK_CLIENT_HELLO), "SSL3_CHECK_CLIENT_HELLO"}, {ERR_FUNC(SSL_F_SSL3_CLIENT_HELLO), "SSL3_CLIENT_HELLO"}, {ERR_FUNC(SSL_F_SSL3_CONNECT), "SSL3_CONNECT"}, {ERR_FUNC(SSL_F_SSL3_CTRL), "SSL3_CTRL"}, @@ -375,6 +376,7 @@ static ERR_STRING_DATA SSL_str_reasons[]= {ERR_REASON(SSL_R_MISSING_TMP_RSA_KEY) ,"missing tmp rsa key"}, {ERR_REASON(SSL_R_MISSING_TMP_RSA_PKEY) ,"missing tmp rsa pkey"}, {ERR_REASON(SSL_R_MISSING_VERIFY_MESSAGE),"missing verify message"}, +{ERR_REASON(SSL_R_MULTIPLE_SGC_RESTARTS) ,"multiple sgc restarts"}, {ERR_REASON(SSL_R_NON_SSLV2_INITIAL_PACKET),"non sslv2 initial packet"}, {ERR_REASON(SSL_R_NO_CERTIFICATES_RETURNED),"no certificates returned"}, {ERR_REASON(SSL_R_NO_CERTIFICATE_ASSIGNED),"no certificate assigned"}, -- 2.34.1