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Support TLS_FALLBACK_SCSV.
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Reviewed-by: Rich Salz <rsalz@openssl.org>
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45264 committed Oct 15, 2014
1 parent 4e05aed commit 6bfe553
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Showing 16 changed files with 140 additions and 25 deletions.
6 changes: 6 additions & 0 deletions CHANGES
Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,12 @@

Changes between 1.0.1i and 1.0.1j [xx XXX xxxx]

*) Add support for TLS_FALLBACK_SCSV.
Client applications doing fallback retries should call
SSL_set_mode(s, SSL_MODE_SEND_FALLBACK_SCSV).
(CVE-2014-3566)
[Adam Langley, Bodo Moeller]

*) Add additional DigestInfo checks.

Reencode DigestInto in DER and check against the original when
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10 changes: 10 additions & 0 deletions apps/s_client.c
Original file line number Diff line number Diff line change
Expand Up @@ -337,6 +337,7 @@ static void sc_usage(void)
BIO_printf(bio_err," -tls1_1 - just use TLSv1.1\n");
BIO_printf(bio_err," -tls1 - just use TLSv1\n");
BIO_printf(bio_err," -dtls1 - just use DTLSv1\n");
BIO_printf(bio_err," -fallback_scsv - send TLS_FALLBACK_SCSV\n");
BIO_printf(bio_err," -mtu - set the link layer MTU\n");
BIO_printf(bio_err," -no_tls1_2/-no_tls1_1/-no_tls1/-no_ssl3/-no_ssl2 - turn off that protocol\n");
BIO_printf(bio_err," -bugs - Switch on all SSL implementation bug workarounds\n");
Expand Down Expand Up @@ -617,6 +618,7 @@ int MAIN(int argc, char **argv)
char *sess_out = NULL;
struct sockaddr peer;
int peerlen = sizeof(peer);
int fallback_scsv = 0;
int enable_timeouts = 0 ;
long socket_mtu = 0;
#ifndef OPENSSL_NO_JPAKE
Expand Down Expand Up @@ -823,6 +825,10 @@ int MAIN(int argc, char **argv)
meth=DTLSv1_client_method();
socket_type=SOCK_DGRAM;
}
else if (strcmp(*argv,"-fallback_scsv") == 0)
{
fallback_scsv = 1;
}
else if (strcmp(*argv,"-timeout") == 0)
enable_timeouts=1;
else if (strcmp(*argv,"-mtu") == 0)
Expand Down Expand Up @@ -1235,6 +1241,10 @@ int MAIN(int argc, char **argv)
SSL_set_session(con, sess);
SSL_SESSION_free(sess);
}

if (fallback_scsv)
SSL_set_mode(con, SSL_MODE_SEND_FALLBACK_SCSV);

#ifndef OPENSSL_NO_TLSEXT
if (servername != NULL)
{
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1 change: 1 addition & 0 deletions crypto/err/openssl.ec
Original file line number Diff line number Diff line change
Expand Up @@ -71,6 +71,7 @@ R SSL_R_TLSV1_ALERT_EXPORT_RESTRICTION 1060
R SSL_R_TLSV1_ALERT_PROTOCOL_VERSION 1070
R SSL_R_TLSV1_ALERT_INSUFFICIENT_SECURITY 1071
R SSL_R_TLSV1_ALERT_INTERNAL_ERROR 1080
R SSL_R_SSLV3_ALERT_INAPPROPRIATE_FALLBACK 1086
R SSL_R_TLSV1_ALERT_USER_CANCELLED 1090
R SSL_R_TLSV1_ALERT_NO_RENEGOTIATION 1100
R SSL_R_TLSV1_UNSUPPORTED_EXTENSION 1110
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10 changes: 10 additions & 0 deletions ssl/d1_lib.c
Original file line number Diff line number Diff line change
Expand Up @@ -266,6 +266,16 @@ long dtls1_ctrl(SSL *s, int cmd, long larg, void *parg)
case DTLS_CTRL_LISTEN:
ret = dtls1_listen(s, parg);
break;
case SSL_CTRL_CHECK_PROTO_VERSION:
/* For library-internal use; checks that the current protocol
* is the highest enabled version (according to s->ctx->method,
* as version negotiation may have changed s->method). */
#if DTLS_MAX_VERSION != DTLS1_VERSION
# error Code needs update for DTLS_method() support beyond DTLS1_VERSION.
#endif
/* Just one protocol version is supported so far;
* fail closed if the version is not as expected. */
return s->version == DTLS_MAX_VERSION;

default:
ret = ssl3_ctrl(s, cmd, larg, parg);
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3 changes: 2 additions & 1 deletion ssl/dtls1.h
Original file line number Diff line number Diff line change
Expand Up @@ -84,6 +84,8 @@ extern "C" {
#endif

#define DTLS1_VERSION 0xFEFF
#define DTLS_MAX_VERSION DTLS1_VERSION

#define DTLS1_BAD_VER 0x0100

#if 0
Expand Down Expand Up @@ -284,4 +286,3 @@ typedef struct dtls1_record_data_st
}
#endif
#endif

3 changes: 3 additions & 0 deletions ssl/s23_clnt.c
Original file line number Diff line number Diff line change
Expand Up @@ -736,6 +736,9 @@ static int ssl23_get_server_hello(SSL *s)
goto err;
}

/* ensure that TLS_MAX_VERSION is up-to-date */
OPENSSL_assert(s->version <= TLS_MAX_VERSION);

if (p[0] == SSL3_RT_ALERT && p[5] != SSL3_AL_WARNING)
{
/* fatal alert */
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3 changes: 3 additions & 0 deletions ssl/s23_srvr.c
Original file line number Diff line number Diff line change
Expand Up @@ -421,6 +421,9 @@ int ssl23_get_client_hello(SSL *s)
}
}

/* ensure that TLS_MAX_VERSION is up-to-date */
OPENSSL_assert(s->version <= TLS_MAX_VERSION);

#ifdef OPENSSL_FIPS
if (FIPS_mode() && (s->version < TLS1_VERSION))
{
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4 changes: 3 additions & 1 deletion ssl/s2_lib.c
Original file line number Diff line number Diff line change
Expand Up @@ -391,6 +391,8 @@ long ssl2_ctrl(SSL *s, int cmd, long larg, void *parg)
case SSL_CTRL_GET_SESSION_REUSED:
ret=s->hit;
break;
case SSL_CTRL_CHECK_PROTO_VERSION:
return ssl3_ctrl(s, SSL_CTRL_CHECK_PROTO_VERSION, larg, parg);
default:
break;
}
Expand Down Expand Up @@ -437,7 +439,7 @@ int ssl2_put_cipher_by_char(const SSL_CIPHER *c, unsigned char *p)
if (p != NULL)
{
l=c->id;
if ((l & 0xff000000) != 0x02000000) return(0);
if ((l & 0xff000000) != 0x02000000 && l != SSL3_CK_FALLBACK_SCSV) return(0);
p[0]=((unsigned char)(l>>16L))&0xFF;
p[1]=((unsigned char)(l>> 8L))&0xFF;
p[2]=((unsigned char)(l ))&0xFF;
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2 changes: 1 addition & 1 deletion ssl/s3_enc.c
Original file line number Diff line number Diff line change
Expand Up @@ -900,7 +900,7 @@ int ssl3_alert_code(int code)
case SSL_AD_BAD_CERTIFICATE_STATUS_RESPONSE: return(SSL3_AD_HANDSHAKE_FAILURE);
case SSL_AD_BAD_CERTIFICATE_HASH_VALUE: return(SSL3_AD_HANDSHAKE_FAILURE);
case SSL_AD_UNKNOWN_PSK_IDENTITY:return(TLS1_AD_UNKNOWN_PSK_IDENTITY);
case SSL_AD_INAPPROPRIATE_FALLBACK:return(TLS1_AD_INAPPROPRIATE_FALLBACK);
default: return(-1);
}
}

29 changes: 28 additions & 1 deletion ssl/s3_lib.c
Original file line number Diff line number Diff line change
Expand Up @@ -3355,6 +3355,33 @@ long ssl3_ctrl(SSL *s, int cmd, long larg, void *parg)
#endif

#endif /* !OPENSSL_NO_TLSEXT */

case SSL_CTRL_CHECK_PROTO_VERSION:
/* For library-internal use; checks that the current protocol
* is the highest enabled version (according to s->ctx->method,
* as version negotiation may have changed s->method). */
if (s->version == s->ctx->method->version)
return 1;
/* Apparently we're using a version-flexible SSL_METHOD
* (not at its highest protocol version). */
if (s->ctx->method->version == SSLv23_method()->version)
{
#if TLS_MAX_VERSION != TLS1_2_VERSION
# error Code needs update for SSLv23_method() support beyond TLS1_2_VERSION.
#endif
if (!(s->options & SSL_OP_NO_TLSv1_2))
return s->version == TLS1_2_VERSION;
if (!(s->options & SSL_OP_NO_TLSv1_1))
return s->version == TLS1_1_VERSION;
if (!(s->options & SSL_OP_NO_TLSv1))
return s->version == TLS1_VERSION;
if (!(s->options & SSL_OP_NO_SSLv3))
return s->version == SSL3_VERSION;
if (!(s->options & SSL_OP_NO_SSLv2))
return s->version == SSL2_VERSION;
}
return 0; /* Unexpected state; fail closed. */

default:
break;
}
Expand Down Expand Up @@ -3714,6 +3741,7 @@ long ssl3_ctx_callback_ctrl(SSL_CTX *ctx, int cmd, void (*fp)(void))
break;
#endif
#endif

default:
return(0);
}
Expand Down Expand Up @@ -4296,4 +4324,3 @@ long ssl_get_algorithm2(SSL *s)
return SSL_HANDSHAKE_MAC_SHA256 | TLS1_PRF_SHA256;
return alg2;
}

9 changes: 9 additions & 0 deletions ssl/ssl.h
Original file line number Diff line number Diff line change
Expand Up @@ -653,6 +653,10 @@ struct ssl_session_st
*/
#define SSL_MODE_SEND_CLIENTHELLO_TIME 0x00000020L
#define SSL_MODE_SEND_SERVERHELLO_TIME 0x00000040L
/* Send TLS_FALLBACK_SCSV in the ClientHello.
* To be set by applications that reconnect with a downgraded protocol
* version; see draft-ietf-tls-downgrade-scsv-00 for details. */
#define SSL_MODE_SEND_FALLBACK_SCSV 0x00000080L

/* Note: SSL[_CTX]_set_{options,mode} use |= op on the previous value,
* they cannot be used to clear bits. */
Expand Down Expand Up @@ -1511,6 +1515,7 @@ DECLARE_PEM_rw(SSL_SESSION, SSL_SESSION)
#define SSL_AD_BAD_CERTIFICATE_STATUS_RESPONSE TLS1_AD_BAD_CERTIFICATE_STATUS_RESPONSE
#define SSL_AD_BAD_CERTIFICATE_HASH_VALUE TLS1_AD_BAD_CERTIFICATE_HASH_VALUE
#define SSL_AD_UNKNOWN_PSK_IDENTITY TLS1_AD_UNKNOWN_PSK_IDENTITY /* fatal */
#define SSL_AD_INAPPROPRIATE_FALLBACK TLS1_AD_INAPPROPRIATE_FALLBACK /* fatal */

#define SSL_ERROR_NONE 0
#define SSL_ERROR_SSL 1
Expand Down Expand Up @@ -1621,6 +1626,8 @@ DECLARE_PEM_rw(SSL_SESSION, SSL_SESSION)
#define SSL_CTRL_GET_EXTRA_CHAIN_CERTS 82
#define SSL_CTRL_CLEAR_EXTRA_CHAIN_CERTS 83

#define SSL_CTRL_CHECK_PROTO_VERSION 119

#define DTLSv1_get_timeout(ssl, arg) \
SSL_ctrl(ssl,DTLS_CTRL_GET_TIMEOUT,0, (void *)arg)
#define DTLSv1_handle_timeout(ssl) \
Expand Down Expand Up @@ -2379,6 +2386,7 @@ void ERR_load_SSL_strings(void);
#define SSL_R_HTTPS_PROXY_REQUEST 155
#define SSL_R_HTTP_REQUEST 156
#define SSL_R_ILLEGAL_PADDING 283
#define SSL_R_INAPPROPRIATE_FALLBACK 373
#define SSL_R_INCONSISTENT_COMPRESSION 340
#define SSL_R_INVALID_CHALLENGE_LENGTH 158
#define SSL_R_INVALID_COMMAND 280
Expand Down Expand Up @@ -2525,6 +2533,7 @@ void ERR_load_SSL_strings(void);
#define SSL_R_TLSV1_ALERT_DECRYPTION_FAILED 1021
#define SSL_R_TLSV1_ALERT_DECRYPT_ERROR 1051
#define SSL_R_TLSV1_ALERT_EXPORT_RESTRICTION 1060
#define SSL_R_TLSV1_ALERT_INAPPROPRIATE_FALLBACK 1086
#define SSL_R_TLSV1_ALERT_INSUFFICIENT_SECURITY 1071
#define SSL_R_TLSV1_ALERT_INTERNAL_ERROR 1080
#define SSL_R_TLSV1_ALERT_NO_RENEGOTIATION 1100
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7 changes: 6 additions & 1 deletion ssl/ssl3.h
Original file line number Diff line number Diff line change
Expand Up @@ -128,9 +128,14 @@
extern "C" {
#endif

/* Signalling cipher suite value: from draft-ietf-tls-renegotiation-03.txt */
/* Signalling cipher suite value from RFC 5746
* (TLS_EMPTY_RENEGOTIATION_INFO_SCSV) */
#define SSL3_CK_SCSV 0x030000FF

/* Signalling cipher suite value from draft-ietf-tls-downgrade-scsv-00
* (TLS_FALLBACK_SCSV) */
#define SSL3_CK_FALLBACK_SCSV 0x03005600

#define SSL3_CK_RSA_NULL_MD5 0x03000001
#define SSL3_CK_RSA_NULL_SHA 0x03000002
#define SSL3_CK_RSA_RC4_40_MD5 0x03000003
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2 changes: 2 additions & 0 deletions ssl/ssl_err.c
Original file line number Diff line number Diff line change
Expand Up @@ -383,6 +383,7 @@ static ERR_STRING_DATA SSL_str_reasons[]=
{ERR_REASON(SSL_R_HTTPS_PROXY_REQUEST) ,"https proxy request"},
{ERR_REASON(SSL_R_HTTP_REQUEST) ,"http request"},
{ERR_REASON(SSL_R_ILLEGAL_PADDING) ,"illegal padding"},
{ERR_REASON(SSL_R_INAPPROPRIATE_FALLBACK),"inappropriate fallback"},
{ERR_REASON(SSL_R_INCONSISTENT_COMPRESSION),"inconsistent compression"},
{ERR_REASON(SSL_R_INVALID_CHALLENGE_LENGTH),"invalid challenge length"},
{ERR_REASON(SSL_R_INVALID_COMMAND) ,"invalid command"},
Expand Down Expand Up @@ -529,6 +530,7 @@ static ERR_STRING_DATA SSL_str_reasons[]=
{ERR_REASON(SSL_R_TLSV1_ALERT_DECRYPTION_FAILED),"tlsv1 alert decryption failed"},
{ERR_REASON(SSL_R_TLSV1_ALERT_DECRYPT_ERROR),"tlsv1 alert decrypt error"},
{ERR_REASON(SSL_R_TLSV1_ALERT_EXPORT_RESTRICTION),"tlsv1 alert export restriction"},
{ERR_REASON(SSL_R_TLSV1_ALERT_INAPPROPRIATE_FALLBACK),"tlsv1 alert inappropriate fallback"},
{ERR_REASON(SSL_R_TLSV1_ALERT_INSUFFICIENT_SECURITY),"tlsv1 alert insufficient security"},
{ERR_REASON(SSL_R_TLSV1_ALERT_INTERNAL_ERROR),"tlsv1 alert internal error"},
{ERR_REASON(SSL_R_TLSV1_ALERT_NO_RENEGOTIATION),"tlsv1 alert no renegotiation"},
Expand Down
60 changes: 46 additions & 14 deletions ssl/ssl_lib.c
Original file line number Diff line number Diff line change
Expand Up @@ -1387,6 +1387,8 @@ int ssl_cipher_list_to_bytes(SSL *s,STACK_OF(SSL_CIPHER) *sk,unsigned char *p,

if (sk == NULL) return(0);
q=p;
if (put_cb == NULL)
put_cb = s->method->put_cipher_by_char;

for (i=0; i<sk_SSL_CIPHER_num(sk); i++)
{
Expand All @@ -1411,24 +1413,36 @@ int ssl_cipher_list_to_bytes(SSL *s,STACK_OF(SSL_CIPHER) *sk,unsigned char *p,
!(s->srp_ctx.srp_Mask & SSL_kSRP))
continue;
#endif /* OPENSSL_NO_SRP */
j = put_cb ? put_cb(c,p) : ssl_put_cipher_by_char(s,c,p);
j = put_cb(c,p);
p+=j;
}
/* If p == q, no ciphers and caller indicates an error. Otherwise
* add SCSV if not renegotiating.
*/
if (p != q && !s->renegotiate)
/* If p == q, no ciphers; caller indicates an error.
* Otherwise, add applicable SCSVs. */
if (p != q)
{
static SSL_CIPHER scsv =
if (!s->renegotiate)
{
0, NULL, SSL3_CK_SCSV, 0, 0, 0, 0, 0, 0, 0, 0, 0
};
j = put_cb ? put_cb(&scsv,p) : ssl_put_cipher_by_char(s,&scsv,p);
p+=j;
static SSL_CIPHER scsv =
{
0, NULL, SSL3_CK_SCSV, 0, 0, 0, 0, 0, 0, 0, 0, 0
};
j = put_cb(&scsv,p);
p+=j;
#ifdef OPENSSL_RI_DEBUG
fprintf(stderr, "SCSV sent by client\n");
fprintf(stderr, "TLS_EMPTY_RENEGOTIATION_INFO_SCSV sent by client\n");
#endif
}
}

if (s->mode & SSL_MODE_SEND_FALLBACK_SCSV)
{
static SSL_CIPHER scsv =
{
0, NULL, SSL3_CK_FALLBACK_SCSV, 0, 0, 0, 0, 0, 0, 0, 0, 0
};
j = put_cb(&scsv,p);
p+=j;
}
}

return(p-q);
}
Expand All @@ -1439,11 +1453,12 @@ STACK_OF(SSL_CIPHER) *ssl_bytes_to_cipher_list(SSL *s,unsigned char *p,int num,
const SSL_CIPHER *c;
STACK_OF(SSL_CIPHER) *sk;
int i,n;

if (s->s3)
s->s3->send_connection_binding = 0;

n=ssl_put_cipher_by_char(s,NULL,NULL);
if ((num%n) != 0)
if (n == 0 || (num%n) != 0)
{
SSLerr(SSL_F_SSL_BYTES_TO_CIPHER_LIST,SSL_R_ERROR_IN_RECEIVED_CIPHER_LIST);
return(NULL);
Expand All @@ -1458,7 +1473,7 @@ STACK_OF(SSL_CIPHER) *ssl_bytes_to_cipher_list(SSL *s,unsigned char *p,int num,

for (i=0; i<num; i+=n)
{
/* Check for SCSV */
/* Check for TLS_EMPTY_RENEGOTIATION_INFO_SCSV */
if (s->s3 && (n != 3 || !p[0]) &&
(p[n-2] == ((SSL3_CK_SCSV >> 8) & 0xff)) &&
(p[n-1] == (SSL3_CK_SCSV & 0xff)))
Expand All @@ -1478,6 +1493,23 @@ STACK_OF(SSL_CIPHER) *ssl_bytes_to_cipher_list(SSL *s,unsigned char *p,int num,
continue;
}

/* Check for TLS_FALLBACK_SCSV */
if ((n != 3 || !p[0]) &&
(p[n-2] == ((SSL3_CK_FALLBACK_SCSV >> 8) & 0xff)) &&
(p[n-1] == (SSL3_CK_FALLBACK_SCSV & 0xff)))
{
/* The SCSV indicates that the client previously tried a higher version.
* Fail if the current version is an unexpected downgrade. */
if (!SSL_ctrl(s, SSL_CTRL_CHECK_PROTO_VERSION, 0, NULL))
{
SSLerr(SSL_F_SSL_BYTES_TO_CIPHER_LIST,SSL_R_INAPPROPRIATE_FALLBACK);
if (s->s3)
ssl3_send_alert(s,SSL3_AL_FATAL,SSL_AD_INAPPROPRIATE_FALLBACK);
goto err;
}
continue;
}

c=ssl_get_cipher_by_char(s,p);
p+=n;
if (c != NULL)
Expand Down
1 change: 1 addition & 0 deletions ssl/t1_enc.c
Original file line number Diff line number Diff line change
Expand Up @@ -1241,6 +1241,7 @@ int tls1_alert_code(int code)
case SSL_AD_BAD_CERTIFICATE_STATUS_RESPONSE: return(TLS1_AD_BAD_CERTIFICATE_STATUS_RESPONSE);
case SSL_AD_BAD_CERTIFICATE_HASH_VALUE: return(TLS1_AD_BAD_CERTIFICATE_HASH_VALUE);
case SSL_AD_UNKNOWN_PSK_IDENTITY:return(TLS1_AD_UNKNOWN_PSK_IDENTITY);
case SSL_AD_INAPPROPRIATE_FALLBACK:return(TLS1_AD_INAPPROPRIATE_FALLBACK);
#if 0 /* not appropriate for TLS, not used for DTLS */
case DTLS1_AD_MISSING_HANDSHAKE_MESSAGE: return
(DTLS1_AD_MISSING_HANDSHAKE_MESSAGE);
Expand Down
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