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Only allow one SGC handshake restart for SSL/TLS. (CVE-2011-4619)

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This commit is contained in:
Dr. Stephen Henson 2012-01-04 18:52:18 +00:00
parent 41cf2c3aef
commit 21c4b25959
5 changed files with 29 additions and 1 deletions
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3
CHANGES
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@ -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

10
ssl/s3_srvr.c
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@ -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;

2
ssl/ssl.h
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@ -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

11
ssl/ssl3.h
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@ -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
{

4
ssl/ssl_err.c
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@ -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"},