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[tls] Generate pre-master secret at point of sending ClientKeyExchange 

The pre-master secret is currently constructed at the time of
instantiating the TLS connection.  This precludes the use of key
exchange mechanisms such as Ephemeral Diffie-Hellman (DHE), which
require a ServerKeyExchange message to exchange additional key
material before the pre-master secret can be constructed.

Allow for the use of such cipher suites by deferring generation of the
master secret until the point of sending the ClientKeyExchange
message.

Signed-off-by: Michael Brown <mcb30@ipxe.org>
pull/785/head
Michael Brown 2022-10-11 13:47:06 +01:00
parent 1a7317e7d4
commit 028aac99a3
2 changed files with 27 additions and 26 deletions
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13
src/include/ipxe/tls.h
View File

@ -48,6 +48,9 @@ struct tls_header {
/** TLS version 1.2 */
#define TLS_VERSION_TLS_1_2 0x0303
/** Maximum supported TLS version */
#define TLS_VERSION_MAX TLS_VERSION_TLS_1_2
/** Change cipher content type */
#define TLS_TYPE_CHANGE_CIPHER 20
@ -209,14 +212,6 @@ struct tls_signature_hash_algorithm {
#define __tls_sig_hash_algorithm \
__table_entry ( TLS_SIG_HASH_ALGORITHMS, 01 )
/** TLS pre-master secret */
struct tls_pre_master_secret {
/** TLS version */
uint16_t version;
/** Random data */
uint8_t random[46];
} __attribute__ (( packed ));
/** TLS client random data */
struct tls_client_random {
/** GMT Unix time */
@ -309,8 +304,6 @@ struct tls_connection {
struct tls_cipherspec rx_cipherspec;
/** Next RX cipher specification */
struct tls_cipherspec rx_cipherspec_pending;
/** Premaster secret */
struct tls_pre_master_secret pre_master_secret;
/** Master secret */
uint8_t master_secret[48];
/** Server random bytes */

40
src/net/tls.c
View File

@ -616,21 +616,23 @@ static void tls_prf ( struct tls_connection *tls, const void *secret,
* Generate master secret
*
* @v tls TLS connection
* @v pre_master_secret Pre-master secret
* @v pre_master_secret_len Length of pre-master secret
*
* The pre-master secret and the client and server random values must
* already be known.
* The client and server random values must already be known.
*/
static void tls_generate_master_secret ( struct tls_connection *tls ) {
static void tls_generate_master_secret ( struct tls_connection *tls,
const void *pre_master_secret,
size_t pre_master_secret_len ) {
DBGC ( tls, "TLS %p pre-master-secret:\n", tls );
DBGC_HD ( tls, &tls->pre_master_secret,
sizeof ( tls->pre_master_secret ) );
DBGC_HD ( tls, pre_master_secret, pre_master_secret_len );
DBGC ( tls, "TLS %p client random bytes:\n", tls );
DBGC_HD ( tls, &tls->client_random, sizeof ( tls->client_random ) );
DBGC ( tls, "TLS %p server random bytes:\n", tls );
DBGC_HD ( tls, &tls->server_random, sizeof ( tls->server_random ) );
tls_prf_label ( tls, &tls->pre_master_secret,
sizeof ( tls->pre_master_secret ),
tls_prf_label ( tls, pre_master_secret, pre_master_secret_len,
&tls->master_secret, sizeof ( tls->master_secret ),
"master secret",
&tls->client_random, sizeof ( tls->client_random ),
@ -1211,6 +1213,10 @@ static int tls_send_client_key_exchange ( struct tls_connection *tls ) {
struct tls_cipherspec *cipherspec = &tls->tx_cipherspec_pending;
struct pubkey_algorithm *pubkey = cipherspec->suite->pubkey;
size_t max_len = pubkey_max_len ( pubkey, cipherspec->pubkey_ctx );
struct {
uint16_t version;
uint8_t random[46];
} __attribute__ (( packed )) pre_master_secret;
struct {
uint32_t type_length;
uint16_t encrypted_pre_master_secret_len;
@ -1220,8 +1226,16 @@ static int tls_send_client_key_exchange ( struct tls_connection *tls ) {
int len;
int rc;
/* Generate pre-master secret */
pre_master_secret.version = htons ( TLS_VERSION_MAX );
if ( ( rc = tls_generate_random ( tls, &pre_master_secret.random,
( sizeof ( pre_master_secret.random ) ) ) ) != 0 ) {
return rc;
}
/* Generate master secret */
tls_generate_master_secret ( tls );
tls_generate_master_secret ( tls, &pre_master_secret,
sizeof ( pre_master_secret ) );
/* Generate keys */
if ( ( rc = tls_generate_keys ( tls ) ) != 0 ) {
@ -1233,8 +1247,7 @@ static int tls_send_client_key_exchange ( struct tls_connection *tls ) {
/* Encrypt pre-master secret using server's public key */
memset ( &key_xchg, 0, sizeof ( key_xchg ) );
len = pubkey_encrypt ( pubkey, cipherspec->pubkey_ctx,
&tls->pre_master_secret,
sizeof ( tls->pre_master_secret ),
&pre_master_secret, sizeof ( pre_master_secret ),
key_xchg.encrypted_pre_master_secret );
if ( len < 0 ) {
rc = len;
@ -3173,7 +3186,7 @@ int add_tls ( struct interface *xfer, const char *name,
&tls->refcnt );
tls->key = privkey_get ( key ? key : &private_key );
tls->root = x509_root_get ( root ? root : &root_certificates );
tls->version = TLS_VERSION_TLS_1_2;
tls->version = TLS_VERSION_MAX;
tls_clear_cipher ( tls, &tls->tx_cipherspec );
tls_clear_cipher ( tls, &tls->tx_cipherspec_pending );
tls_clear_cipher ( tls, &tls->rx_cipherspec );
@ -3186,11 +3199,6 @@ int add_tls ( struct interface *xfer, const char *name,
( sizeof ( tls->client_random.random ) ) ) ) != 0 ) {
goto err_random;
}
tls->pre_master_secret.version = htons ( tls->version );
if ( ( rc = tls_generate_random ( tls, &tls->pre_master_secret.random,
( sizeof ( tls->pre_master_secret.random ) ) ) ) != 0 ) {
goto err_random;
}
if ( ( rc = tls_session ( tls, name ) ) != 0 )
goto err_session;
list_add_tail ( &tls->list, &tls->session->conn );