/*
* The S flag is set only within the EAP-TLS start message sent
* from the EAP server to the peer.
*
* Similarly, when the EAP server receives an EAP-Response with
* the M bit set, it MUST respond with an EAP-Request with
* EAP-Type=EAP-TLS and no data. This serves as a fragment
* ACK. The EAP peer MUST wait.
*/
static fr_tls_status_t eaptls_verify(eap_handler_t *handler)
{
EAP_DS *eap_ds = handler->eap_ds;
tls_session_t *tls_session = handler->opaque;
EAP_DS *prev_eap_ds = handler->prev_eap_ds;
eaptls_packet_t *eaptls_packet;
REQUEST *request = handler->request;
size_t frag_len;
/*
* We don't check ANY of the input parameters. It's all
* code which works together, so if something is wrong,
* we SHOULD core dump.
*
* e.g. if eap_ds is NULL, of if eap_ds->response is
* NULL, of if it's NOT an EAP-Response, or if the packet
* is too short. See eap_validation()., in ../../eap.c
*/
eaptls_packet = (eaptls_packet_t *)eap_ds->response->type.data;
/*
* First output the flags (for debugging)
*/
RDEBUG3("Peer sent flags %c%c%c",
TLS_START(eaptls_packet->flags) ? 'S' : '-',
TLS_MORE_FRAGMENTS(eaptls_packet->flags) ? 'M' : '-',
TLS_LENGTH_INCLUDED(eaptls_packet->flags) ? 'L' : '-');
/*
* check for ACK
*
* If there's no TLS data, or there's 1 byte of TLS data,
* with the flags set to zero, then it's an ACK.
*
* Find if this is a reply to the previous request sent
*/
if ((!eaptls_packet) ||
((eap_ds->response->length == EAP_HEADER_LEN + 2) &&
((eaptls_packet->flags & 0xc0) == 0x00))) {
if (prev_eap_ds && (prev_eap_ds->request->id == eap_ds->response->id)) {
return tls_ack_handler(handler->opaque, request);
} else {
REDEBUG("Received Invalid TLS ACK");
return FR_TLS_INVALID;
}
}
/*
* We send TLS_START, but do not receive it.
*/
if (TLS_START(eaptls_packet->flags)) {
REDEBUG("Peer sent EAP-TLS Start message (only the server is allowed to do this)");
return FR_TLS_INVALID;
}
/*
* Calculate this fragment's length
*/
frag_len = eap_ds->response->length -
(EAP_HEADER_LEN + (TLS_LENGTH_INCLUDED(eaptls_packet->flags) ? 6 : 2));
/*
* The L bit (length included) is set to indicate the
* presence of the four octet TLS Message Length field,
* and MUST be set for the first fragment of a fragmented
* TLS message or set of messages.
*
* The M bit (more fragments) is set on all but the last
* fragment.
*
* The S bit (EAP-TLS start) is set in an EAP-TLS Start
* message. This differentiates the EAP-TLS Start message
* from a fragment acknowledgement.
*/
if (TLS_LENGTH_INCLUDED(eaptls_packet->flags)) {
size_t total_len = eaptls_packet->data[2] * 256 | eaptls_packet->data[3];
if (frag_len > total_len) {
REDEBUG("TLS fragment length (%zu bytes) greater than TLS record length (%zu bytes)", frag_len,
total_len);
return FR_TLS_INVALID;
}
if (tls_session->tls_record_transfer_started) {
REDEBUG("TLS Length Included (L) flag set, which indicates a new fragment transfer, "
"but previous transfer was not complete");
return FR_TLS_INVALID;
}
/*
* This is the first fragment of a fragmented TLS record transfer.
*/
RDEBUG2("Peer indicated complete TLS record size will be %zu bytes", total_len);
if (TLS_MORE_FRAGMENTS(eaptls_packet->flags)) {
/*
* The supplicant is free to send fragments of wildly varying
* lengths, but the vast majority won't.
*
* In this calculation we take into account the fact that the future
* fragments are likely to be 4 bytes larger than the initial one
* as they won't contain the length field.
*/
if (frag_len + 4) { /* check for wrap, else clang scan gets excited */
RDEBUG2("Expecting %i TLS record fragments",
(int)((((total_len - frag_len) + ((frag_len + 4) - 1)) / (frag_len + 4)) + 1));
}
/*
* First fragment. tls_record_transfer_started bool was false,
* and we received a length included + more fragments packet.
*/
RDEBUG2("Got first TLS record fragment (%zu bytes). Peer indicated more fragments "
"to follow", frag_len);
tls_session->tls_record_in_total_len = total_len;
tls_session->tls_record_in_recvd_len = frag_len;
tls_session->tls_record_transfer_started = true;
return FR_TLS_FIRST_FRAGMENT;
}
/*
* Else this is the complete TLS record.
*/
if (total_len != frag_len) {
REDEBUG("Peer indicated no more fragments, but TLS record length (%zu bytes) "
"does not match EAP-TLS data length (%zu bytes)", total_len, frag_len);
return FR_TLS_INVALID;
}
/*
* RFC5216 doesn't specify explicitly whether a non-fragmented
* packet should include the length or not.
*
* We support both options for maximum compatibility.
*/
RDEBUG2("Got complete TLS record, with length (%zu bytes)", frag_len);
return FR_TLS_LENGTH_INCLUDED;
}
if (TLS_MORE_FRAGMENTS(eaptls_packet->flags)) {
/*
* If this is not an ongoing transfer, and we have the M flag
* then this record transfer is invalid.
*/
if (!tls_session->tls_record_transfer_started) {
REDEBUG("TLS More (M) flag set, but no fragmented record transfer was in progress");
return FR_TLS_INVALID;
}
/*
* If this is an ongoing transfer, and we have the M flag,
* then this is just an additional fragment.
*/
RDEBUG2("Got additional TLS record fragment (%zu bytes). Peer indicated more fragments to follow",
frag_len);
tls_session->tls_record_in_recvd_len += frag_len;
if (tls_session->tls_record_in_recvd_len > tls_session->tls_record_in_total_len) {
REDEBUG("Total received TLS record fragments (%zu bytes), exceeds "
"indicated TLS record length (%zu bytes)",
tls_session->tls_record_in_recvd_len, tls_session->tls_record_in_total_len);
return FR_TLS_INVALID;
}
return FR_TLS_MORE_FRAGMENTS;
}
/*
* No L flag and no M flag. This is either the final fragment,
* or a new transfer that was not started with a L flag, which
* RFC5216 hints, may be acceptable.
*
* If it's an in-progress record transfer, check we now have
* the complete record.
*/
if (tls_session->tls_record_transfer_started) {
tls_session->tls_record_transfer_started = false;
RDEBUG2("Got final TLS record fragment (%zu bytes)", frag_len);
tls_session->tls_record_in_recvd_len += frag_len;
if (tls_session->tls_record_in_recvd_len != tls_session->tls_record_in_total_len) {
REDEBUG("Total received TLS record fragments (%zu bytes), does not equal indicated "
"TLS record length (%zu bytes)",
tls_session->tls_record_in_recvd_len, tls_session->tls_record_in_total_len);
return FR_TLS_INVALID;
}
return FR_TLS_OK;
}
/*
* None of the flags are set, it wasn't an in progress transfer,
* but it's still a valid EAP-TLS packet.
*/
RDEBUG2("Got complete TLS record (%zu bytes)", frag_len);
return FR_TLS_OK;
}
/*
* The S flag is set only within the EAP-TLS start message sent
* from the EAP server to the peer.
*
* Similarly, when the EAP server receives an EAP-Response with
* the M bit set, it MUST respond with an EAP-Request with
* EAP-Type=EAP-TLS and no data. This serves as a fragment
* ACK. The EAP peer MUST wait.
*/
static fr_tls_status_t eaptls_verify(eap_handler_t *handler)
{
EAP_DS *eap_ds = handler->eap_ds;
EAP_DS *prev_eap_ds = handler->prev_eapds;
eaptls_packet_t *eaptls_packet, *eaptls_prev = NULL;
REQUEST *request = handler->request;
/*
* We don't check ANY of the input parameters. It's all
* code which works together, so if something is wrong,
* we SHOULD core dump.
*
* e.g. if eap_ds is NULL, of if eap_ds->response is
* NULL, of if it's NOT an EAP-Response, or if the packet
* is too short. See eap_validation()., in ../../eap.c
*
* Also, eap_method_select() takes care of selecting the
* appropriate type, so we don't need to check
* eap_ds->response->type.num == PW_EAP_TLS, or anything
* else.
*/
eaptls_packet = (eaptls_packet_t *)eap_ds->response->type.data;
if (prev_eap_ds && prev_eap_ds->response)
eaptls_prev = (eaptls_packet_t *)prev_eap_ds->response->type.data;
/*
* check for ACK
*
* If there's no TLS data, or there's 1 byte of TLS data,
* with the flags set to zero, then it's an ACK.
*
* Find if this is a reply to the previous request sent
*/
if ((!eaptls_packet) ||
((eap_ds->response->length == EAP_HEADER_LEN + 2) &&
((eaptls_packet->flags & 0xc0) == 0x00))) {
if (prev_eap_ds &&
(prev_eap_ds->request->id == eap_ds->response->id)) {
/*
* Run the ACK handler directly from here.
*/
RDEBUG2("Received TLS ACK");
return tls_ack_handler(handler->opaque, request);
} else {
RERROR("Received Invalid TLS ACK");
return FR_TLS_INVALID;
}
}
/*
* We send TLS_START, but do not receive it.
*/
if (TLS_START(eaptls_packet->flags)) {
RDEBUG("Received unexpected EAP-TLS Start message");
return FR_TLS_INVALID;
}
/*
* The L bit (length included) is set to indicate the
* presence of the four octet TLS Message Length field,
* and MUST be set for the first fragment of a fragmented
* TLS message or set of messages.
*
* The M bit (more fragments) is set on all but the last
* fragment.
*
* The S bit (EAP-TLS start) is set in an EAP-TLS Start
* message. This differentiates the EAP-TLS Start message
* from a fragment acknowledgement.
*/
if (TLS_LENGTH_INCLUDED(eaptls_packet->flags)) {
DEBUG2(" TLS Length %d",
eaptls_packet->data[2] * 256 | eaptls_packet->data[3]);
if (TLS_MORE_FRAGMENTS(eaptls_packet->flags)) {
/*
* FIRST_FRAGMENT is identified
* 1. If there is no previous EAP-response received.
* 2. If EAP-response received, then its M bit not set.
* (It is because Last fragment will not have M bit set)
*/
if (!prev_eap_ds ||
(!prev_eap_ds->response) ||
(!eaptls_prev) ||
!TLS_MORE_FRAGMENTS(eaptls_prev->flags)) {
RDEBUG2("Received EAP-TLS First Fragment of the message");
return FR_TLS_FIRST_FRAGMENT;
} else {
RDEBUG2("More Fragments with length included");
return FR_TLS_MORE_FRAGMENTS_WITH_LENGTH;
}
} else {
RDEBUG2("Length Included");
return FR_TLS_LENGTH_INCLUDED;
}
}
if (TLS_MORE_FRAGMENTS(eaptls_packet->flags)) {
RDEBUG2("More fragments to follow");
return FR_TLS_MORE_FRAGMENTS;
}
/*
* None of the flags are set, but it's still a valid
* EAPTLS packet.
*/
return FR_TLS_OK;
}