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Do not allow non-dhe kex_modes by default

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Allow that mode to be configured if desired.

Reviewed-by: Rich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/3833)
This commit is contained in:
Matt Caswell 2017-06-30 09:41:03 +01:00
parent 5159821540
commit e3c0d76bc7
6 changed files with 28 additions and 16 deletions
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12
apps/apps.h
View file

@ -214,10 +214,11 @@ int set_cert_times(X509 *x, const char *startdate, const char *enddate,
OPT_S_NOSSL3, OPT_S_NOTLS1, OPT_S_NOTLS1_1, OPT_S_NOTLS1_2, \
OPT_S_NOTLS1_3, OPT_S_BUGS, OPT_S_NO_COMP, OPT_S_NOTICKET, \
OPT_S_SERVERPREF, OPT_S_LEGACYRENEG, OPT_S_LEGACYCONN, \
OPT_S_ONRESUMP, OPT_S_NOLEGACYCONN, OPT_S_STRICT, OPT_S_SIGALGS, \
OPT_S_CLIENTSIGALGS, OPT_S_GROUPS, OPT_S_CURVES, OPT_S_NAMEDCURVE, \
OPT_S_CIPHER, OPT_S_DHPARAM, OPT_S_RECORD_PADDING, OPT_S_DEBUGBROKE, \
OPT_S_COMP, OPT_S_NO_RENEGOTIATION, OPT_S__LAST
OPT_S_ONRESUMP, OPT_S_NOLEGACYCONN, OPT_S_ALLOW_NO_DHE_KEX, \
OPT_S_STRICT, OPT_S_SIGALGS, OPT_S_CLIENTSIGALGS, OPT_S_GROUPS, \
OPT_S_CURVES, OPT_S_NAMEDCURVE, OPT_S_CIPHER, OPT_S_DHPARAM, \
OPT_S_RECORD_PADDING, OPT_S_DEBUGBROKE, OPT_S_COMP, \
OPT_S_NO_RENEGOTIATION, OPT_S__LAST
# define OPT_S_OPTIONS \
{"no_ssl3", OPT_S_NOSSL3, '-',"Just disable SSLv3" }, \
@ -241,6 +242,8 @@ int set_cert_times(X509 *x, const char *startdate, const char *enddate,
"Disallow session resumption on renegotiation"}, \
{"no_legacy_server_connect", OPT_S_NOLEGACYCONN, '-', \
"Disallow initial connection to servers that don't support RI"}, \
{"allow_no_dhe_kex", OPT_S_ALLOW_NO_DHE_KEX, '-', \
"In TLSv1.3 allow non-(ec)dhe based key exchange on resumption"}, \
{"strict", OPT_S_STRICT, '-', \
"Enforce strict certificate checks as per TLS standard"}, \
{"sigalgs", OPT_S_SIGALGS, 's', \
@ -279,6 +282,7 @@ int set_cert_times(X509 *x, const char *startdate, const char *enddate,
case OPT_S_LEGACYCONN: \
case OPT_S_ONRESUMP: \
case OPT_S_NOLEGACYCONN: \
case OPT_S_ALLOW_NO_DHE_KEX: \
case OPT_S_STRICT: \
case OPT_S_SIGALGS: \
case OPT_S_CLIENTSIGALGS: \

3
include/openssl/ssl.h
View file

@ -282,6 +282,9 @@ typedef int (*SSL_custom_ext_parse_cb_ex) (SSL *s, unsigned int ext_type,
/* Typedef for verification callback */
typedef int (*SSL_verify_cb)(int preverify_ok, X509_STORE_CTX *x509_ctx);
/* In TLSv1.3 allow a non-(ec)dhe based kex_mode */
# define SSL_OP_ALLOW_NO_DHE_KEX 0x00000001U
/* Allow initial connection to servers that don't support RI */
# define SSL_OP_LEGACY_SERVER_CONNECT 0x00000004U
# define SSL_OP_TLSEXT_PADDING 0x00000010U

4
ssl/ssl_conf.c
View file

@ -367,6 +367,7 @@ static int cmd_Options(SSL_CONF_CTX *cctx, const char *value)
SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION),
SSL_FLAG_TBL_INV("EncryptThenMac", SSL_OP_NO_ENCRYPT_THEN_MAC),
SSL_FLAG_TBL("NoRenegotiation", SSL_OP_NO_RENEGOTIATION),
SSL_FLAG_TBL("AllowNoDHEKEX", SSL_OP_ALLOW_NO_DHE_KEX)
};
if (value == NULL)
return -3;
@ -585,6 +586,7 @@ static const ssl_conf_cmd_tbl ssl_conf_cmds[] = {
SSL_CONF_CMD_SWITCH("no_renegotiation", 0),
SSL_CONF_CMD_SWITCH("no_resumption_on_reneg", SSL_CONF_FLAG_SERVER),
SSL_CONF_CMD_SWITCH("no_legacy_server_connect", SSL_CONF_FLAG_SERVER),
SSL_CONF_CMD_SWITCH("allow_no_dhe_kex", 0),
SSL_CONF_CMD_SWITCH("strict", 0),
SSL_CONF_CMD_STRING(SignatureAlgorithms, "sigalgs", 0),
SSL_CONF_CMD_STRING(ClientSignatureAlgorithms, "client_sigalgs", 0),
@ -655,6 +657,8 @@ static const ssl_switch_tbl ssl_cmd_switches[] = {
{SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION, 0},
/* no_legacy_server_connect */
{SSL_OP_LEGACY_SERVER_CONNECT, SSL_TFLAG_INV},
/* allow_no_dhe_kex */
{SSL_OP_ALLOW_NO_DHE_KEX, 0},
{SSL_CERT_FLAG_TLS_STRICT, SSL_TFLAG_CERT}, /* strict */
};

15
ssl/statem/extensions_clnt.c
View file

@ -503,30 +503,29 @@ EXT_RETURN tls_construct_ctos_supported_versions(SSL *s, WPACKET *pkt,
}
/*
* Construct a psk_kex_modes extension. We only have two modes we know about
* at this stage, so we send both.
* Construct a psk_kex_modes extension.
*/
EXT_RETURN tls_construct_ctos_psk_kex_modes(SSL *s, WPACKET *pkt,
unsigned int context, X509 *x,
size_t chainidx, int *al)
{
#ifndef OPENSSL_NO_TLS1_3
/*
* TODO(TLS1.3): Do we want this list to be configurable? For now we always
* just send both supported modes
*/
int nodhe = s->options & SSL_OP_ALLOW_NO_DHE_KEX;
if (!WPACKET_put_bytes_u16(pkt, TLSEXT_TYPE_psk_kex_modes)
|| !WPACKET_start_sub_packet_u16(pkt)
|| !WPACKET_start_sub_packet_u8(pkt)
|| !WPACKET_put_bytes_u8(pkt, TLSEXT_KEX_MODE_KE_DHE)
|| !WPACKET_put_bytes_u8(pkt, TLSEXT_KEX_MODE_KE)
|| (nodhe && !WPACKET_put_bytes_u8(pkt, TLSEXT_KEX_MODE_KE))
|| !WPACKET_close(pkt)
|| !WPACKET_close(pkt)) {
SSLerr(SSL_F_TLS_CONSTRUCT_CTOS_PSK_KEX_MODES, ERR_R_INTERNAL_ERROR);
return EXT_RETURN_FAIL;
}
s->ext.psk_kex_mode = TLSEXT_KEX_MODE_FLAG_KE | TLSEXT_KEX_MODE_FLAG_KE_DHE;
s->ext.psk_kex_mode = TLSEXT_KEX_MODE_FLAG_KE_DHE;
if (nodhe)
s->ext.psk_kex_mode |= TLSEXT_KEX_MODE_FLAG_KE;
#endif
return EXT_RETURN_SENT;

3
ssl/statem/extensions_srvr.c
View file

@ -477,7 +477,8 @@ int tls_parse_ctos_psk_kex_modes(SSL *s, PACKET *pkt, unsigned int context,
while (PACKET_get_1(&psk_kex_modes, &mode)) {
if (mode == TLSEXT_KEX_MODE_KE_DHE)
s->ext.psk_kex_mode |= TLSEXT_KEX_MODE_FLAG_KE_DHE;
else if (mode == TLSEXT_KEX_MODE_KE)
else if (mode == TLSEXT_KEX_MODE_KE
&& (s->options & SSL_OP_ALLOW_NO_DHE_KEX) != 0)
s->ext.psk_kex_mode |= TLSEXT_KEX_MODE_FLAG_KE;
}
#endif

7
test/recipes/70-test_tls13kexmodes.t
View file

@ -171,7 +171,8 @@ ok(TLSProxy::Message->fail(), "Resume with empty kex modes");
#Test 4: Attempt a resume with non-dhe kex mode only. Should resume without a
# key_share
$proxy->clear();
$proxy->clientflags("-sess_in ".$session);
$proxy->clientflags("-allow_no_dhe_kex -sess_in ".$session);
$proxy->serverflags("-allow_no_dhe_kex");
$testtype = NON_DHE_KEX_MODE_ONLY;
$proxy->start();
checkhandshake($proxy, checkhandshake::RESUME_HANDSHAKE,
@ -256,8 +257,8 @@ checkhandshake($proxy, checkhandshake::HRR_RESUME_HANDSHAKE,
# initial key_share and no overlapping groups. Should resume without a
# key_share
$proxy->clear();
$proxy->clientflags("-curves P-384 -sess_in ".$session);
$proxy->serverflags("-curves P-256");
$proxy->clientflags("-allow_no_dhe_kex -curves P-384 -sess_in ".$session);
$proxy->serverflags("-allow_no_dhe_kex -curves P-256");
$testtype = BOTH_KEX_MODES;
$proxy->start();
checkhandshake($proxy, checkhandshake::RESUME_HANDSHAKE,