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[tls] Support stateless session resumption
Add support for RFC5077 session ticket extensions to allow for
stateless TLS session resumption.

Signed-off-by: Michael Brown <mcb30@ipxe.org>
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mcb30 committed Mar 6, 2019
1 parent 799781f commit eaba1a2
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Showing 2 changed files with 122 additions and 19 deletions.
12 changes: 12 additions & 0 deletions src/include/ipxe/tls.h
Expand Up @@ -63,6 +63,7 @@ struct tls_header {
#define TLS_HELLO_REQUEST 0
#define TLS_CLIENT_HELLO 1
#define TLS_SERVER_HELLO 2
#define TLS_NEW_SESSION_TICKET 4
#define TLS_CERTIFICATE 11
#define TLS_SERVER_KEY_EXCHANGE 12
#define TLS_CERTIFICATE_REQUEST 13
Expand Down Expand Up @@ -108,6 +109,9 @@ struct tls_header {
/* TLS signature algorithms extension */
#define TLS_SIGNATURE_ALGORITHMS 13

/* TLS session ticket extension */
#define TLS_SESSION_TICKET 35

/* TLS renegotiation information extension */
#define TLS_RENEGOTIATION_INFO 0xff01

Expand Down Expand Up @@ -255,6 +259,10 @@ struct tls_session {
uint8_t id[32];
/** Length of session ID */
size_t id_len;
/** Session ticket */
void *ticket;
/** Length of session ticket */
size_t ticket_len;
/** Master secret */
uint8_t master_secret[48];

Expand All @@ -275,6 +283,10 @@ struct tls_connection {
uint8_t session_id[32];
/** Length of session ID */
size_t session_id_len;
/** New session ticket */
void *new_session_ticket;
/** Length of new session ticket */
size_t new_session_ticket_len;

/** Plaintext stream */
struct interface plainstream;
Expand Down
129 changes: 110 additions & 19 deletions src/net/tls.c
Expand Up @@ -102,6 +102,10 @@ FILE_LICENCE ( GPL2_OR_LATER );
#define EINFO_EINVAL_MAC \
__einfo_uniqify ( EINFO_EINVAL, 0x0d, \
"Invalid MAC" )
#define EINVAL_TICKET __einfo_error ( EINFO_EINVAL_TICKET )
#define EINFO_EINVAL_TICKET \
__einfo_uniqify ( EINFO_EINVAL, 0x0e, \
"Invalid New Session Ticket record")
#define EIO_ALERT __einfo_error ( EINFO_EIO_ALERT )
#define EINFO_EIO_ALERT \
__einfo_uniqify ( EINFO_EIO, 0x01, \
Expand Down Expand Up @@ -326,6 +330,9 @@ static void free_tls_session ( struct refcnt *refcnt ) {
/* Remove from list of sessions */
list_del ( &session->list );

/* Free session ticket */
free ( session->ticket );

/* Free session */
free ( session );
}
Expand All @@ -343,6 +350,7 @@ static void free_tls ( struct refcnt *refcnt ) {
struct io_buffer *tmp;

/* Free dynamically-allocated resources */
free ( tls->new_session_ticket );
tls_clear_cipher ( tls, &tls->tx_cipherspec );
tls_clear_cipher ( tls, &tls->tx_cipherspec_pending );
tls_clear_cipher ( tls, &tls->rx_cipherspec );
Expand Down Expand Up @@ -1007,7 +1015,7 @@ static int tls_send_client_hello ( struct tls_connection *tls ) {
uint16_t version;
uint8_t random[32];
uint8_t session_id_len;
uint8_t session_id[session->id_len];
uint8_t session_id[tls->session_id_len];
uint16_t cipher_suite_len;
uint16_t cipher_suites[TLS_NUM_CIPHER_SUITES];
uint8_t compression_methods_len;
Expand Down Expand Up @@ -1043,18 +1051,17 @@ static int tls_send_client_hello ( struct tls_connection *tls ) {
uint8_t data[ tls->secure_renegotiation ?
sizeof ( tls->verify.client ) :0];
} __attribute__ (( packed )) renegotiation_info;
uint16_t session_ticket_type;
uint16_t session_ticket_len;
struct {
uint8_t data[session->ticket_len];
} __attribute__ (( packed )) session_ticket;
} __attribute__ (( packed )) extensions;
} __attribute__ (( packed )) hello;
struct tls_cipher_suite *suite;
struct tls_signature_hash_algorithm *sighash;
unsigned int i;

/* Record requested session ID and associated master secret */
memcpy ( tls->session_id, session->id, sizeof ( tls->session_id ) );
tls->session_id_len = session->id_len;
memcpy ( tls->master_secret, session->master_secret,
sizeof ( tls->master_secret ) );

/* Construct record */
memset ( &hello, 0, sizeof ( hello ) );
hello.type_length = ( cpu_to_le32 ( TLS_CLIENT_HELLO ) |
Expand Down Expand Up @@ -1102,6 +1109,11 @@ static int tls_send_client_hello ( struct tls_connection *tls ) {
= sizeof ( hello.extensions.renegotiation_info.data );
memcpy ( hello.extensions.renegotiation_info.data, tls->verify.client,
sizeof ( hello.extensions.renegotiation_info.data ) );
hello.extensions.session_ticket_type = htons ( TLS_SESSION_TICKET );
hello.extensions.session_ticket_len
= htons ( sizeof ( hello.extensions.session_ticket ) );
memcpy ( hello.extensions.session_ticket.data, session->ticket,
sizeof ( hello.extensions.session_ticket.data ) );

return tls_send_handshake ( tls, &hello, sizeof ( hello ) );
}
Expand Down Expand Up @@ -1631,6 +1643,57 @@ static int tls_new_server_hello ( struct tls_connection *tls,
return 0;
}

/**
* Receive New Session Ticket handshake record
*
* @v tls TLS connection
* @v data Plaintext handshake record
* @v len Length of plaintext handshake record
* @ret rc Return status code
*/
static int tls_new_session_ticket ( struct tls_connection *tls,
const void *data, size_t len ) {
const struct {
uint32_t lifetime;
uint16_t len;
uint8_t ticket[0];
} __attribute__ (( packed )) *new_session_ticket = data;
size_t ticket_len;

/* Parse header */
if ( sizeof ( *new_session_ticket ) > len ) {
DBGC ( tls, "TLS %p received underlength New Session Ticket\n",
tls );
DBGC_HD ( tls, data, len );
return -EINVAL_TICKET;
}
ticket_len = ntohs ( new_session_ticket->len );
if ( ticket_len > ( len - sizeof ( *new_session_ticket ) ) ) {
DBGC ( tls, "TLS %p received overlength New Session Ticket\n",
tls );
DBGC_HD ( tls, data, len );
return -EINVAL_TICKET;
}

/* Free any unapplied new session ticket */
free ( tls->new_session_ticket );
tls->new_session_ticket = NULL;
tls->new_session_ticket_len = 0;

/* Record ticket */
tls->new_session_ticket = malloc ( ticket_len );
if ( ! tls->new_session_ticket )
return -ENOMEM;
memcpy ( tls->new_session_ticket, new_session_ticket->ticket,
ticket_len );
tls->new_session_ticket_len = ticket_len;
DBGC ( tls, "TLS %p new session ticket:\n", tls );
DBGC_HDA ( tls, 0, tls->new_session_ticket,
tls->new_session_ticket_len );

return 0;
}

/**
* Parse certificate chain
*
Expand Down Expand Up @@ -1863,12 +1926,21 @@ static int tls_new_finished ( struct tls_connection *tls,
tls_tx_resume ( tls );
}

/* Record session ID and master secret, if applicable */
/* Record session ID, ticket, and master secret, if applicable */
if ( tls->session_id_len || tls->new_session_ticket_len ) {
memcpy ( session->master_secret, tls->master_secret,
sizeof ( session->master_secret ) );
}
if ( tls->session_id_len ) {
session->id_len = tls->session_id_len;
memcpy ( session->id, tls->session_id, sizeof ( session->id ) );
memcpy ( session->master_secret, tls->master_secret,
sizeof ( session->master_secret ) );
}
if ( tls->new_session_ticket_len ) {
free ( session->ticket );
session->ticket = tls->new_session_ticket;
session->ticket_len = tls->new_session_ticket_len;
tls->new_session_ticket = NULL;
tls->new_session_ticket_len = 0;
}

/* Move to end of session's connection list and allow other
Expand Down Expand Up @@ -1933,6 +2005,10 @@ static int tls_new_handshake ( struct tls_connection *tls,
case TLS_SERVER_HELLO:
rc = tls_new_server_hello ( tls, payload, payload_len );
break;
case TLS_NEW_SESSION_TICKET:
rc = tls_new_session_ticket ( tls, payload,
payload_len );
break;
case TLS_CERTIFICATE:
rc = tls_new_certificate ( tls, payload, payload_len );
break;
Expand Down Expand Up @@ -2804,16 +2880,31 @@ static void tls_tx_step ( struct tls_connection *tls ) {

/* Send first pending transmission */
if ( tls->tx_pending & TLS_TX_CLIENT_HELLO ) {
/* Wait for session ID to become available unless we
* are the lead connection within the session.
/* Serialise server negotiations within a session, to
* provide a consistent view of session IDs and
* session tickets.
*/
if ( session->id_len == 0 ) {
list_for_each_entry ( conn, &session->conn, list ) {
if ( conn == tls )
break;
if ( is_pending ( &conn->server_negotiation ) )
return;
}
list_for_each_entry ( conn, &session->conn, list ) {
if ( conn == tls )
break;
if ( is_pending ( &conn->server_negotiation ) )
return;
}
/* Record or generate session ID and associated master secret */
if ( session->id_len ) {
/* Attempt to resume an existing session */
memcpy ( tls->session_id, session->id,
sizeof ( tls->session_id ) );
tls->session_id_len = session->id_len;
memcpy ( tls->master_secret, session->master_secret,
sizeof ( tls->master_secret ) );
} else {
/* No existing session: use a random session ID */
assert ( sizeof ( tls->session_id ) ==
sizeof ( tls->client_random ) );
memcpy ( tls->session_id, &tls->client_random,
sizeof ( tls->session_id ) );
tls->session_id_len = sizeof ( tls->session_id );
}
/* Send Client Hello */
if ( ( rc = tls_send_client_hello ( tls ) ) != 0 ) {
Expand Down

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