wbrawner/openssl
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity Actions
openssl/ssl/record/rec_layer_d1.c
Matt Caswell 5cb4d6466a Prevent DTLS Finished message injection 
Follow on from CVE-2016-2179

The investigation and analysis of CVE-2016-2179 highlighted a related flaw.

This commit fixes a security "near miss" in the buffered message handling
code. Ultimately this is not currently believed to be exploitable due to
the reasons outlined below, and therefore there is no CVE for this on its
own.

The issue this commit fixes is a MITM attack where the attacker can inject
a Finished message into the handshake. In the description below it is
assumed that the attacker injects the Finished message for the server to
receive it. The attack could work equally well the other way around (i.e
where the client receives the injected Finished message).

The MITM requires the following capabilities:
- The ability to manipulate the MTU that the client selects such that it
is small enough for the client to fragment Finished messages.
- The ability to selectively drop and modify records sent from the client
- The ability to inject its own records and send them to the server

The MITM forces the client to select a small MTU such that the client
will fragment the Finished message. Ideally for the attacker the first
fragment will contain all but the last byte of the Finished message,
with the second fragment containing the final byte.

During the handshake and prior to the client sending the CCS the MITM
injects a plaintext Finished message fragment to the server containing
all but the final byte of the Finished message. The message sequence
number should be the one expected to be used for the real Finished message.

OpenSSL will recognise that the received fragment is for the future and
will buffer it for later use.

After the client sends the CCS it then sends its own Finished message in
two fragments. The MITM causes the first of these fragments to be
dropped. The OpenSSL server will then receive the second of the fragments
and reassemble the complete Finished message consisting of the MITM
fragment and the final byte from the real client.

The advantage to the attacker in injecting a Finished message is that
this provides the capability to modify other handshake messages (e.g.
the ClientHello) undetected. A difficulty for the attacker is knowing in
advance what impact any of those changes might have on the final byte of
the handshake hash that is going to be sent in the "real" Finished
message. In the worst case for the attacker this means that only 1 in
256 of such injection attempts will succeed.

It may be possible in some situations for the attacker to improve this such
that all attempts succeed. For example if the handshake includes client
authentication then the final message flight sent by the client will
include a Certificate. Certificates are ASN.1 objects where the signed
portion is DER encoded. The non-signed portion could be BER encoded and so
the attacker could re-encode the certificate such that the hash for the
whole handshake comes to a different value. The certificate re-encoding
would not be detectable because only the non-signed portion is changed. As
this is the final flight of messages sent from the client the attacker
knows what the complete hanshake hash value will be that the client will
send - and therefore knows what the final byte will be. Through a process
of trial and error the attacker can re-encode the certificate until the
modified handhshake also has a hash with the same final byte. This means
that when the Finished message is verified by the server it will be
correct in all cases.

In practice the MITM would need to be able to perform the same attack
against both the client and the server. If the attack is only performed
against the server (say) then the server will not detect the modified
handshake, but the client will and will abort the connection.
Fortunately, although OpenSSL is vulnerable to Finished message
injection, it is not vulnerable if *both* client and server are OpenSSL.
The reason is that OpenSSL has a hard "floor" for a minimum MTU size
that it will never go below. This minimum means that a Finished message
will never be sent in a fragmented form and therefore the MITM does not
have one of its pre-requisites. Therefore this could only be exploited
if using OpenSSL and some other DTLS peer that had its own and separate
Finished message injection flaw.

The fix is to ensure buffered messages are cleared on epoch change.

Reviewed-by: Richard Levitte <levitte@openssl.org>
2016-08-22 10:53:55 +01:00

1206 lines
39 KiB
C
Raw Blame History

/*
* Copyright 2005-2016 The OpenSSL Project Authors. All Rights Reserved.
*
* Licensed under the OpenSSL license (the "License"). You may not use
* this file except in compliance with the License. You can obtain a copy
* in the file LICENSE in the source distribution or at
* https://www.openssl.org/source/license.html
*/
#include <stdio.h>
#include <errno.h>
#define USE_SOCKETS
#include "../ssl_locl.h"
#include <openssl/evp.h>
#include <openssl/buffer.h>
#include "record_locl.h"
int DTLS_RECORD_LAYER_new(RECORD_LAYER *rl)
{
DTLS_RECORD_LAYER *d;
if ((d = OPENSSL_malloc(sizeof(*d))) == NULL)
return (0);
rl->d = d;
d->unprocessed_rcds.q = pqueue_new();
d->processed_rcds.q = pqueue_new();
d->buffered_app_data.q = pqueue_new();
if (d->unprocessed_rcds.q == NULL || d->processed_rcds.q == NULL
|| d->buffered_app_data.q == NULL) {
pqueue_free(d->unprocessed_rcds.q);
pqueue_free(d->processed_rcds.q);
pqueue_free(d->buffered_app_data.q);
OPENSSL_free(d);
rl->d = NULL;
return (0);
}
return 1;
}
void DTLS_RECORD_LAYER_free(RECORD_LAYER *rl)
{
DTLS_RECORD_LAYER_clear(rl);
pqueue_free(rl->d->unprocessed_rcds.q);
pqueue_free(rl->d->processed_rcds.q);
pqueue_free(rl->d->buffered_app_data.q);
OPENSSL_free(rl->d);
rl->d = NULL;
}
void DTLS_RECORD_LAYER_clear(RECORD_LAYER *rl)
{
DTLS_RECORD_LAYER *d;
pitem *item = NULL;
DTLS1_RECORD_DATA *rdata;
pqueue *unprocessed_rcds;
pqueue *processed_rcds;
pqueue *buffered_app_data;
d = rl->d;
while ((item = pqueue_pop(d->unprocessed_rcds.q)) != NULL) {
rdata = (DTLS1_RECORD_DATA *)item->data;
OPENSSL_free(rdata->rbuf.buf);
OPENSSL_free(item->data);
pitem_free(item);
}
while ((item = pqueue_pop(d->processed_rcds.q)) != NULL) {
rdata = (DTLS1_RECORD_DATA *)item->data;
OPENSSL_free(rdata->rbuf.buf);
OPENSSL_free(item->data);
pitem_free(item);
}
while ((item = pqueue_pop(d->buffered_app_data.q)) != NULL) {
rdata = (DTLS1_RECORD_DATA *)item->data;
OPENSSL_free(rdata->rbuf.buf);
OPENSSL_free(item->data);
pitem_free(item);
}
unprocessed_rcds = d->unprocessed_rcds.q;
processed_rcds = d->processed_rcds.q;
buffered_app_data = d->buffered_app_data.q;
memset(d, 0, sizeof(*d));
d->unprocessed_rcds.q = unprocessed_rcds;
d->processed_rcds.q = processed_rcds;
d->buffered_app_data.q = buffered_app_data;
}
void DTLS_RECORD_LAYER_set_saved_w_epoch(RECORD_LAYER *rl, unsigned short e)
{
if (e == rl->d->w_epoch - 1) {
memcpy(rl->d->curr_write_sequence,
rl->write_sequence, sizeof(rl->write_sequence));
memcpy(rl->write_sequence,
rl->d->last_write_sequence, sizeof(rl->write_sequence));
} else if (e == rl->d->w_epoch + 1) {
memcpy(rl->d->last_write_sequence,
rl->write_sequence, sizeof(unsigned char[8]));
memcpy(rl->write_sequence,
rl->d->curr_write_sequence, sizeof(rl->write_sequence));
}
rl->d->w_epoch = e;
}
void DTLS_RECORD_LAYER_resync_write(RECORD_LAYER *rl)
{
memcpy(rl->write_sequence, rl->read_sequence, sizeof(rl->write_sequence));
}
void DTLS_RECORD_LAYER_set_write_sequence(RECORD_LAYER *rl, unsigned char *seq)
{
memcpy(rl->write_sequence, seq, SEQ_NUM_SIZE);
}
static int have_handshake_fragment(SSL *s, int type, unsigned char *buf,
int len);
/* copy buffered record into SSL structure */
static int dtls1_copy_record(SSL *s, pitem *item)
{
DTLS1_RECORD_DATA *rdata;
rdata = (DTLS1_RECORD_DATA *)item->data;
SSL3_BUFFER_release(&s->rlayer.rbuf);
s->rlayer.packet = rdata->packet;
s->rlayer.packet_length = rdata->packet_length;
memcpy(&s->rlayer.rbuf, &(rdata->rbuf), sizeof(SSL3_BUFFER));
memcpy(&s->rlayer.rrec, &(rdata->rrec), sizeof(SSL3_RECORD));
/* Set proper sequence number for mac calculation */
memcpy(&(s->rlayer.read_sequence[2]), &(rdata->packet[5]), 6);
return (1);
}
int dtls1_buffer_record(SSL *s, record_pqueue *queue, unsigned char *priority)
{
DTLS1_RECORD_DATA *rdata;
pitem *item;
/* Limit the size of the queue to prevent DOS attacks */
if (pqueue_size(queue->q) >= 100)
return 0;
rdata = OPENSSL_malloc(sizeof(*rdata));
item = pitem_new(priority, rdata);
if (rdata == NULL || item == NULL) {
OPENSSL_free(rdata);
pitem_free(item);
SSLerr(SSL_F_DTLS1_BUFFER_RECORD, ERR_R_INTERNAL_ERROR);
return -1;
}
rdata->packet = s->rlayer.packet;
rdata->packet_length = s->rlayer.packet_length;
memcpy(&(rdata->rbuf), &s->rlayer.rbuf, sizeof(SSL3_BUFFER));
memcpy(&(rdata->rrec), &s->rlayer.rrec, sizeof(SSL3_RECORD));
item->data = rdata;
#ifndef OPENSSL_NO_SCTP
/* Store bio_dgram_sctp_rcvinfo struct */
if (BIO_dgram_is_sctp(SSL_get_rbio(s)) &&
(SSL_get_state(s) == TLS_ST_SR_FINISHED
|| SSL_get_state(s) == TLS_ST_CR_FINISHED)) {
BIO_ctrl(SSL_get_rbio(s), BIO_CTRL_DGRAM_SCTP_GET_RCVINFO,
sizeof(rdata->recordinfo), &rdata->recordinfo);
}
#endif
s->rlayer.packet = NULL;
s->rlayer.packet_length = 0;
memset(&s->rlayer.rbuf, 0, sizeof(s->rlayer.rbuf));
memset(&s->rlayer.rrec, 0, sizeof(s->rlayer.rrec));
if (!ssl3_setup_buffers(s)) {
SSLerr(SSL_F_DTLS1_BUFFER_RECORD, ERR_R_INTERNAL_ERROR);
OPENSSL_free(rdata->rbuf.buf);
OPENSSL_free(rdata);
pitem_free(item);
return (-1);
}
/* insert should not fail, since duplicates are dropped */
if (pqueue_insert(queue->q, item) == NULL) {
SSLerr(SSL_F_DTLS1_BUFFER_RECORD, ERR_R_INTERNAL_ERROR);
OPENSSL_free(rdata->rbuf.buf);
OPENSSL_free(rdata);
pitem_free(item);
return (-1);
}
return (1);
}
int dtls1_retrieve_buffered_record(SSL *s, record_pqueue *queue)
{
pitem *item;
item = pqueue_pop(queue->q);
if (item) {
dtls1_copy_record(s, item);
OPENSSL_free(item->data);
pitem_free(item);
return (1);
}
return (0);
}
/*
* retrieve a buffered record that belongs to the new epoch, i.e., not
* processed yet
*/
#define dtls1_get_unprocessed_record(s) \
dtls1_retrieve_buffered_record((s), \
&((s)->rlayer.d->unprocessed_rcds))
int dtls1_process_buffered_records(SSL *s)
{
pitem *item;
SSL3_BUFFER *rb;
SSL3_RECORD *rr;
DTLS1_BITMAP *bitmap;
unsigned int is_next_epoch;
int replayok = 1;
item = pqueue_peek(s->rlayer.d->unprocessed_rcds.q);
if (item) {
/* Check if epoch is current. */
if (s->rlayer.d->unprocessed_rcds.epoch != s->rlayer.d->r_epoch)
return 1; /* Nothing to do. */
rr = RECORD_LAYER_get_rrec(&s->rlayer);
rb = RECORD_LAYER_get_rbuf(&s->rlayer);
if (SSL3_BUFFER_get_left(rb) > 0) {
/*
* We've still got data from the current packet to read. There could
* be a record from the new epoch in it - so don't overwrite it
* with the unprocessed records yet (we'll do it when we've
* finished reading the current packet).
*/
return 1;
}
/* Process all the records. */
while (pqueue_peek(s->rlayer.d->unprocessed_rcds.q)) {
dtls1_get_unprocessed_record(s);
bitmap = dtls1_get_bitmap(s, rr, &is_next_epoch);
if (bitmap == NULL) {
/*
* Should not happen. This will only ever be NULL when the
* current record is from a different epoch. But that cannot
* be the case because we already checked the epoch above
*/
SSLerr(SSL_F_DTLS1_PROCESS_BUFFERED_RECORDS,
ERR_R_INTERNAL_ERROR);
return 0;
}
#ifndef OPENSSL_NO_SCTP
/* Only do replay check if no SCTP bio */
if (!BIO_dgram_is_sctp(SSL_get_rbio(s)))
#endif
{
/*
* Check whether this is a repeat, or aged record. We did this
* check once already when we first received the record - but
* we might have updated the window since then due to
* records we subsequently processed.
*/
replayok = dtls1_record_replay_check(s, bitmap);
}
if (!replayok || !dtls1_process_record(s, bitmap)) {
/* dump this record */
rr->length = 0;
RECORD_LAYER_reset_packet_length(&s->rlayer);
continue;
}
if (dtls1_buffer_record(s, &(s->rlayer.d->processed_rcds),
SSL3_RECORD_get_seq_num(s->rlayer.rrec)) < 0)
return 0;
}
}
/*
* sync epoch numbers once all the unprocessed records have been
* processed
*/
s->rlayer.d->processed_rcds.epoch = s->rlayer.d->r_epoch;
s->rlayer.d->unprocessed_rcds.epoch = s->rlayer.d->r_epoch + 1;
return 1;
}
/*-
* Return up to 'len' payload bytes received in 'type' records.
* 'type' is one of the following:
*
* - SSL3_RT_HANDSHAKE (when ssl3_get_message calls us)
* - SSL3_RT_APPLICATION_DATA (when ssl3_read calls us)
* - 0 (during a shutdown, no data has to be returned)
*
* If we don't have stored data to work from, read a SSL/TLS record first
* (possibly multiple records if we still don't have anything to return).
*
* This function must handle any surprises the peer may have for us, such as
* Alert records (e.g. close_notify) or renegotiation requests. ChangeCipherSpec
* messages are treated as if they were handshake messages *if* the |recd_type|
* argument is non NULL.
* Also if record payloads contain fragments too small to process, we store
* them until there is enough for the respective protocol (the record protocol
* may use arbitrary fragmentation and even interleaving):
* Change cipher spec protocol
* just 1 byte needed, no need for keeping anything stored
* Alert protocol
* 2 bytes needed (AlertLevel, AlertDescription)
* Handshake protocol
* 4 bytes needed (HandshakeType, uint24 length) -- we just have
* to detect unexpected Client Hello and Hello Request messages
* here, anything else is handled by higher layers
* Application data protocol
* none of our business
*/
int dtls1_read_bytes(SSL *s, int type, int *recvd_type, unsigned char *buf,
int len, int peek)
{
int al, i, j, ret;
unsigned int n;
SSL3_RECORD *rr;
void (*cb) (const SSL *ssl, int type2, int val) = NULL;
if (!SSL3_BUFFER_is_initialised(&s->rlayer.rbuf)) {
/* Not initialized yet */
if (!ssl3_setup_buffers(s))
return (-1);
}
if ((type && (type != SSL3_RT_APPLICATION_DATA) &&
(type != SSL3_RT_HANDSHAKE)) ||
(peek && (type != SSL3_RT_APPLICATION_DATA))) {
SSLerr(SSL_F_DTLS1_READ_BYTES, ERR_R_INTERNAL_ERROR);
return -1;
}
/*
* check whether there's a handshake message (client hello?) waiting
*/
if ((ret = have_handshake_fragment(s, type, buf, len)))
return ret;
/*
* Now s->rlayer.d->handshake_fragment_len == 0 if
* type == SSL3_RT_HANDSHAKE.
*/
#ifndef OPENSSL_NO_SCTP
/*
* Continue handshake if it had to be interrupted to read app data with
* SCTP.
*/
if ((!ossl_statem_get_in_handshake(s) && SSL_in_init(s)) ||
(BIO_dgram_is_sctp(SSL_get_rbio(s))
&& ossl_statem_in_sctp_read_sock(s)
&& s->s3->in_read_app_data != 2))
#else
if (!ossl_statem_get_in_handshake(s) && SSL_in_init(s))
#endif
{
/* type == SSL3_RT_APPLICATION_DATA */
i = s->handshake_func(s);
if (i < 0)
return (i);
if (i == 0) {
SSLerr(SSL_F_DTLS1_READ_BYTES, SSL_R_SSL_HANDSHAKE_FAILURE);
return (-1);
}
}
start:
s->rwstate = SSL_NOTHING;
/*-
* s->s3->rrec.type - is the type of record
* s->s3->rrec.data, - data
* s->s3->rrec.off, - offset into 'data' for next read
* s->s3->rrec.length, - number of bytes.
*/
rr = s->rlayer.rrec;
/*
* We are not handshaking and have no data yet, so process data buffered
* during the last handshake in advance, if any.
*/
if (SSL_is_init_finished(s) && SSL3_RECORD_get_length(rr) == 0) {
pitem *item;
item = pqueue_pop(s->rlayer.d->buffered_app_data.q);
if (item) {
#ifndef OPENSSL_NO_SCTP
/* Restore bio_dgram_sctp_rcvinfo struct */
if (BIO_dgram_is_sctp(SSL_get_rbio(s))) {
DTLS1_RECORD_DATA *rdata = (DTLS1_RECORD_DATA *)item->data;
BIO_ctrl(SSL_get_rbio(s), BIO_CTRL_DGRAM_SCTP_SET_RCVINFO,
sizeof(rdata->recordinfo), &rdata->recordinfo);
}
#endif
dtls1_copy_record(s, item);
OPENSSL_free(item->data);
pitem_free(item);
}
}
/* Check for timeout */
if (dtls1_handle_timeout(s) > 0)
goto start;
/* get new packet if necessary */
if ((SSL3_RECORD_get_length(rr) == 0)
|| (s->rlayer.rstate == SSL_ST_READ_BODY)) {
ret = dtls1_get_record(s);
if (ret <= 0) {
ret = dtls1_read_failed(s, ret);
/* anything other than a timeout is an error */
if (ret <= 0)
return (ret);
else
goto start;
}
}
/* we now have a packet which can be read and processed */
if (s->s3->change_cipher_spec /* set when we receive ChangeCipherSpec,
* reset by ssl3_get_finished */
&& (SSL3_RECORD_get_type(rr) != SSL3_RT_HANDSHAKE)) {
/*
* We now have application data between CCS and Finished. Most likely
* the packets were reordered on their way, so buffer the application
* data for later processing rather than dropping the connection.
*/
if (dtls1_buffer_record(s, &(s->rlayer.d->buffered_app_data),
SSL3_RECORD_get_seq_num(rr)) < 0) {
SSLerr(SSL_F_DTLS1_READ_BYTES, ERR_R_INTERNAL_ERROR);
return -1;
}
SSL3_RECORD_set_length(rr, 0);
goto start;
}
/*
* If the other end has shut down, throw anything we read away (even in
* 'peek' mode)
*/
if (s->shutdown & SSL_RECEIVED_SHUTDOWN) {
SSL3_RECORD_set_length(rr, 0);
s->rwstate = SSL_NOTHING;
return (0);
}
if (type == SSL3_RECORD_get_type(rr)
|| (SSL3_RECORD_get_type(rr) == SSL3_RT_CHANGE_CIPHER_SPEC
&& type == SSL3_RT_HANDSHAKE && recvd_type != NULL)) {
/*
* SSL3_RT_APPLICATION_DATA or
* SSL3_RT_HANDSHAKE or
* SSL3_RT_CHANGE_CIPHER_SPEC
*/
/*
* make sure that we are not getting application data when we are
* doing a handshake for the first time
*/
if (SSL_in_init(s) && (type == SSL3_RT_APPLICATION_DATA) &&
(s->enc_read_ctx == NULL)) {
al = SSL_AD_UNEXPECTED_MESSAGE;
SSLerr(SSL_F_DTLS1_READ_BYTES, SSL_R_APP_DATA_IN_HANDSHAKE);
goto f_err;
}
if (recvd_type != NULL)
*recvd_type = SSL3_RECORD_get_type(rr);
if (len <= 0)
return (len);
if ((unsigned int)len > SSL3_RECORD_get_length(rr))
n = SSL3_RECORD_get_length(rr);
else
n = (unsigned int)len;
memcpy(buf, &(SSL3_RECORD_get_data(rr)[SSL3_RECORD_get_off(rr)]), n);
if (!peek) {
SSL3_RECORD_sub_length(rr, n);
SSL3_RECORD_add_off(rr, n);
if (SSL3_RECORD_get_length(rr) == 0) {
s->rlayer.rstate = SSL_ST_READ_HEADER;
SSL3_RECORD_set_off(rr, 0);
}
}
#ifndef OPENSSL_NO_SCTP
/*
* We were about to renegotiate but had to read belated application
* data first, so retry.
*/
if (BIO_dgram_is_sctp(SSL_get_rbio(s)) &&
SSL3_RECORD_get_type(rr) == SSL3_RT_APPLICATION_DATA &&
ossl_statem_in_sctp_read_sock(s)) {
s->rwstate = SSL_READING;
BIO_clear_retry_flags(SSL_get_rbio(s));
BIO_set_retry_read(SSL_get_rbio(s));
}
/*
* We might had to delay a close_notify alert because of reordered
* app data. If there was an alert and there is no message to read
* anymore, finally set shutdown.
*/
if (BIO_dgram_is_sctp(SSL_get_rbio(s)) &&
s->d1->shutdown_received
&& !BIO_dgram_sctp_msg_waiting(SSL_get_rbio(s))) {
s->shutdown |= SSL_RECEIVED_SHUTDOWN;
return (0);
}
#endif
return (n);
}
/*
* If we get here, then type != rr->type; if we have a handshake message,
* then it was unexpected (Hello Request or Client Hello).
*/
/*
* In case of record types for which we have 'fragment' storage, fill
* that so that we can process the data at a fixed place.
*/
{
unsigned int k, dest_maxlen = 0;
unsigned char *dest = NULL;
unsigned int *dest_len = NULL;
if (SSL3_RECORD_get_type(rr) == SSL3_RT_HANDSHAKE) {
dest_maxlen = sizeof s->rlayer.d->handshake_fragment;
dest = s->rlayer.d->handshake_fragment;
dest_len = &s->rlayer.d->handshake_fragment_len;
} else if (SSL3_RECORD_get_type(rr) == SSL3_RT_ALERT) {
dest_maxlen = sizeof(s->rlayer.d->alert_fragment);
dest = s->rlayer.d->alert_fragment;
dest_len = &s->rlayer.d->alert_fragment_len;
}
#ifndef OPENSSL_NO_HEARTBEATS
else if (SSL3_RECORD_get_type(rr) == DTLS1_RT_HEARTBEAT) {
/* We allow a 0 return */
if (dtls1_process_heartbeat(s, SSL3_RECORD_get_data(rr),
SSL3_RECORD_get_length(rr)) < 0) {
return -1;
}
/* Exit and notify application to read again */
SSL3_RECORD_set_length(rr, 0);
s->rwstate = SSL_READING;
BIO_clear_retry_flags(SSL_get_rbio(s));
BIO_set_retry_read(SSL_get_rbio(s));
return (-1);
}
#endif
/* else it's a CCS message, or application data or wrong */
else if (SSL3_RECORD_get_type(rr) != SSL3_RT_CHANGE_CIPHER_SPEC) {
/*
* Application data while renegotiating is allowed. Try again
* reading.
*/
if (SSL3_RECORD_get_type(rr) == SSL3_RT_APPLICATION_DATA) {
BIO *bio;
s->s3->in_read_app_data = 2;
bio = SSL_get_rbio(s);
s->rwstate = SSL_READING;
BIO_clear_retry_flags(bio);
BIO_set_retry_read(bio);
return (-1);
}
/* Not certain if this is the right error handling */
al = SSL_AD_UNEXPECTED_MESSAGE;
SSLerr(SSL_F_DTLS1_READ_BYTES, SSL_R_UNEXPECTED_RECORD);
goto f_err;
}
if (dest_maxlen > 0) {
/*
* XDTLS: In a pathological case, the Client Hello may be
* fragmented--don't always expect dest_maxlen bytes
*/
if (SSL3_RECORD_get_length(rr) < dest_maxlen) {
#ifdef DTLS1_AD_MISSING_HANDSHAKE_MESSAGE
/*
* for normal alerts rr->length is 2, while
* dest_maxlen is 7 if we were to handle this
* non-existing alert...
*/
FIX ME;
#endif
s->rlayer.rstate = SSL_ST_READ_HEADER;
SSL3_RECORD_set_length(rr, 0);
goto start;
}
/* now move 'n' bytes: */
for (k = 0; k < dest_maxlen; k++) {
dest[k] = SSL3_RECORD_get_data(rr)[SSL3_RECORD_get_off(rr)];
SSL3_RECORD_add_off(rr, 1);
SSL3_RECORD_add_length(rr, -1);
}
*dest_len = dest_maxlen;
}
}
/*-
* s->rlayer.d->handshake_fragment_len == 12 iff rr->type == SSL3_RT_HANDSHAKE;
* s->rlayer.d->alert_fragment_len == 7 iff rr->type == SSL3_RT_ALERT.
* (Possibly rr is 'empty' now, i.e. rr->length may be 0.)
*/
/* If we are a client, check for an incoming 'Hello Request': */
if ((!s->server) &&
(s->rlayer.d->handshake_fragment_len >= DTLS1_HM_HEADER_LENGTH) &&
(s->rlayer.d->handshake_fragment[0] == SSL3_MT_HELLO_REQUEST) &&
(s->session != NULL) && (s->session->cipher != NULL)) {
s->rlayer.d->handshake_fragment_len = 0;
if ((s->rlayer.d->handshake_fragment[1] != 0) ||
(s->rlayer.d->handshake_fragment[2] != 0) ||
(s->rlayer.d->handshake_fragment[3] != 0)) {
al = SSL_AD_DECODE_ERROR;
SSLerr(SSL_F_DTLS1_READ_BYTES, SSL_R_BAD_HELLO_REQUEST);
goto f_err;
}
/*
* no need to check sequence number on HELLO REQUEST messages
*/
if (s->msg_callback)
s->msg_callback(0, s->version, SSL3_RT_HANDSHAKE,
s->rlayer.d->handshake_fragment, 4, s,
s->msg_callback_arg);
if (SSL_is_init_finished(s) &&
!(s->s3->flags & SSL3_FLAGS_NO_RENEGOTIATE_CIPHERS) &&
!s->s3->renegotiate) {
s->d1->handshake_read_seq++;
s->new_session = 1;
ssl3_renegotiate(s);
if (ssl3_renegotiate_check(s)) {
i = s->handshake_func(s);
if (i < 0)
return (i);
if (i == 0) {
SSLerr(SSL_F_DTLS1_READ_BYTES, SSL_R_SSL_HANDSHAKE_FAILURE);
return (-1);
}
if (!(s->mode & SSL_MODE_AUTO_RETRY)) {
if (SSL3_BUFFER_get_left(&s->rlayer.rbuf) == 0) {
/* no read-ahead left? */
BIO *bio;
/*
* In the case where we try to read application data,
* but we trigger an SSL handshake, we return -1 with
* the retry option set. Otherwise renegotiation may
* cause nasty problems in the blocking world
*/
s->rwstate = SSL_READING;
bio = SSL_get_rbio(s);
BIO_clear_retry_flags(bio);
BIO_set_retry_read(bio);
return (-1);
}
}
}
}
/*
* we either finished a handshake or ignored the request, now try
* again to obtain the (application) data we were asked for
*/
goto start;
}
if (s->rlayer.d->alert_fragment_len >= DTLS1_AL_HEADER_LENGTH) {
int alert_level = s->rlayer.d->alert_fragment[0];
int alert_descr = s->rlayer.d->alert_fragment[1];
s->rlayer.d->alert_fragment_len = 0;
if (s->msg_callback)
s->msg_callback(0, s->version, SSL3_RT_ALERT,
s->rlayer.d->alert_fragment, 2, s,
s->msg_callback_arg);
if (s->info_callback != NULL)
cb = s->info_callback;
else if (s->ctx->info_callback != NULL)
cb = s->ctx->info_callback;
if (cb != NULL) {
j = (alert_level << 8) | alert_descr;
cb(s, SSL_CB_READ_ALERT, j);
}
if (alert_level == SSL3_AL_WARNING) {
s->s3->warn_alert = alert_descr;
if (alert_descr == SSL_AD_CLOSE_NOTIFY) {
#ifndef OPENSSL_NO_SCTP
/*
* With SCTP and streams the socket may deliver app data
* after a close_notify alert. We have to check this first so
* that nothing gets discarded.
*/
if (BIO_dgram_is_sctp(SSL_get_rbio(s)) &&
BIO_dgram_sctp_msg_waiting(SSL_get_rbio(s))) {
s->d1->shutdown_received = 1;
s->rwstate = SSL_READING;
BIO_clear_retry_flags(SSL_get_rbio(s));
BIO_set_retry_read(SSL_get_rbio(s));
return -1;
}
#endif
s->shutdown |= SSL_RECEIVED_SHUTDOWN;
return (0);
}
#if 0
/* XXX: this is a possible improvement in the future */
/* now check if it's a missing record */
if (alert_descr == DTLS1_AD_MISSING_HANDSHAKE_MESSAGE) {
unsigned short seq;
unsigned int frag_off;
unsigned char *p = &(s->rlayer.d->alert_fragment[2]);
n2s(p, seq);
n2l3(p, frag_off);
dtls1_retransmit_message(s,
dtls1_get_queue_priority
(frag->msg_header.seq, 0), frag_off,
&found);
if (!found && SSL_in_init(s)) {
/*
* fprintf( stderr,"in init = %d\n", SSL_in_init(s));
*/
/*
* requested a message not yet sent, send an alert
* ourselves
*/
ssl3_send_alert(s, SSL3_AL_WARNING,
DTLS1_AD_MISSING_HANDSHAKE_MESSAGE);
}
}
#endif
} else if (alert_level == SSL3_AL_FATAL) {
char tmp[16];
s->rwstate = SSL_NOTHING;
s->s3->fatal_alert = alert_descr;
SSLerr(SSL_F_DTLS1_READ_BYTES, SSL_AD_REASON_OFFSET + alert_descr);
BIO_snprintf(tmp, sizeof tmp, "%d", alert_descr);
ERR_add_error_data(2, "SSL alert number ", tmp);
s->shutdown |= SSL_RECEIVED_SHUTDOWN;
SSL_CTX_remove_session(s->session_ctx, s->session);
return (0);
} else {
al = SSL_AD_ILLEGAL_PARAMETER;
SSLerr(SSL_F_DTLS1_READ_BYTES, SSL_R_UNKNOWN_ALERT_TYPE);
goto f_err;
}
goto start;
}
if (s->shutdown & SSL_SENT_SHUTDOWN) { /* but we have not received a
* shutdown */
s->rwstate = SSL_NOTHING;
SSL3_RECORD_set_length(rr, 0);
return (0);
}
if (SSL3_RECORD_get_type(rr) == SSL3_RT_CHANGE_CIPHER_SPEC) {
/*
* We can't process a CCS now, because previous handshake messages
* are still missing, so just drop it.
*/
SSL3_RECORD_set_length(rr, 0);
goto start;
}
/*
* Unexpected handshake message (Client Hello, or protocol violation)
*/
if ((s->rlayer.d->handshake_fragment_len >= DTLS1_HM_HEADER_LENGTH) &&
!ossl_statem_get_in_handshake(s)) {
struct hm_header_st msg_hdr;
/* this may just be a stale retransmit */
dtls1_get_message_header(rr->data, &msg_hdr);
if (SSL3_RECORD_get_epoch(rr) != s->rlayer.d->r_epoch) {
SSL3_RECORD_set_length(rr, 0);
goto start;
}
/*
* If we are server, we may have a repeated FINISHED of the client
* here, then retransmit our CCS and FINISHED.
*/
if (msg_hdr.type == SSL3_MT_FINISHED) {
if (dtls1_check_timeout_num(s) < 0)
return -1;
dtls1_retransmit_buffered_messages(s);
SSL3_RECORD_set_length(rr, 0);
goto start;
}
if (SSL_is_init_finished(s) &&
!(s->s3->flags & SSL3_FLAGS_NO_RENEGOTIATE_CIPHERS)) {
ossl_statem_set_in_init(s, 1);
s->renegotiate = 1;
s->new_session = 1;
}
i = s->handshake_func(s);
if (i < 0)
return (i);
if (i == 0) {
SSLerr(SSL_F_DTLS1_READ_BYTES, SSL_R_SSL_HANDSHAKE_FAILURE);
return (-1);
}
if (!(s->mode & SSL_MODE_AUTO_RETRY)) {
if (SSL3_BUFFER_get_left(&s->rlayer.rbuf) == 0) {
/* no read-ahead left? */
BIO *bio;
/*
* In the case where we try to read application data, but we
* trigger an SSL handshake, we return -1 with the retry
* option set. Otherwise renegotiation may cause nasty
* problems in the blocking world
*/
s->rwstate = SSL_READING;
bio = SSL_get_rbio(s);
BIO_clear_retry_flags(bio);
BIO_set_retry_read(bio);
return (-1);
}
}
goto start;
}
switch (SSL3_RECORD_get_type(rr)) {
default:
/* TLS just ignores unknown message types */
if (s->version == TLS1_VERSION) {
SSL3_RECORD_set_length(rr, 0);
goto start;
}
al = SSL_AD_UNEXPECTED_MESSAGE;
SSLerr(SSL_F_DTLS1_READ_BYTES, SSL_R_UNEXPECTED_RECORD);
goto f_err;
case SSL3_RT_CHANGE_CIPHER_SPEC:
case SSL3_RT_ALERT:
case SSL3_RT_HANDSHAKE:
/*
* we already handled all of these, with the possible exception of
* SSL3_RT_HANDSHAKE when ossl_statem_get_in_handshake(s) is true, but
* that should not happen when type != rr->type
*/
al = SSL_AD_UNEXPECTED_MESSAGE;
SSLerr(SSL_F_DTLS1_READ_BYTES, ERR_R_INTERNAL_ERROR);
goto f_err;
case SSL3_RT_APPLICATION_DATA:
/*
* At this point, we were expecting handshake data, but have
* application data. If the library was running inside ssl3_read()
* (i.e. in_read_app_data is set) and it makes sense to read
* application data at this point (session renegotiation not yet
* started), we will indulge it.
*/
if (s->s3->in_read_app_data &&
(s->s3->total_renegotiations != 0) &&
ossl_statem_app_data_allowed(s)) {
s->s3->in_read_app_data = 2;
return (-1);
} else {
al = SSL_AD_UNEXPECTED_MESSAGE;
SSLerr(SSL_F_DTLS1_READ_BYTES, SSL_R_UNEXPECTED_RECORD);
goto f_err;
}
}
/* not reached */
f_err:
ssl3_send_alert(s, SSL3_AL_FATAL, al);
return (-1);
}
/*
* this only happens when a client hello is received and a handshake
* is started.
*/
static int have_handshake_fragment(SSL *s, int type, unsigned char *buf,
int len)
{
if ((type == SSL3_RT_HANDSHAKE)
&& (s->rlayer.d->handshake_fragment_len > 0))
/* (partially) satisfy request from storage */
{
unsigned char *src = s->rlayer.d->handshake_fragment;
unsigned char *dst = buf;
unsigned int k, n;
/* peek == 0 */
n = 0;
while ((len > 0) && (s->rlayer.d->handshake_fragment_len > 0)) {
*dst++ = *src++;
len--;
s->rlayer.d->handshake_fragment_len--;
n++;
}
/* move any remaining fragment bytes: */
for (k = 0; k < s->rlayer.d->handshake_fragment_len; k++)
s->rlayer.d->handshake_fragment[k] = *src++;
return n;
}
return 0;
}
/*
* Call this to write data in records of type 'type' It will return <= 0 if
* not all data has been sent or non-blocking IO.
*/
int dtls1_write_bytes(SSL *s, int type, const void *buf, int len)
{
int i;
OPENSSL_assert(len <= SSL3_RT_MAX_PLAIN_LENGTH);
s->rwstate = SSL_NOTHING;
i = do_dtls1_write(s, type, buf, len, 0);
return i;
}
int do_dtls1_write(SSL *s, int type, const unsigned char *buf,
unsigned int len, int create_empty_fragment)
{
unsigned char *p, *pseq;
int i, mac_size, clear = 0;
int prefix_len = 0;
int eivlen;
SSL3_RECORD wr;
SSL3_BUFFER *wb;
SSL_SESSION *sess;
wb = &s->rlayer.wbuf[0];
/*
* first check if there is a SSL3_BUFFER still being written out. This
* will happen with non blocking IO
*/
if (SSL3_BUFFER_get_left(wb) != 0) {
OPENSSL_assert(0); /* XDTLS: want to see if we ever get here */
return (ssl3_write_pending(s, type, buf, len));
}
/* If we have an alert to send, lets send it */
if (s->s3->alert_dispatch) {
i = s->method->ssl_dispatch_alert(s);
if (i <= 0)
return (i);
/* if it went, fall through and send more stuff */
}
if (len == 0 && !create_empty_fragment)
return 0;
sess = s->session;
if ((sess == NULL) ||
(s->enc_write_ctx == NULL) || (EVP_MD_CTX_md(s->write_hash) == NULL))
clear = 1;
if (clear)
mac_size = 0;
else {
mac_size = EVP_MD_CTX_size(s->write_hash);
if (mac_size < 0)
goto err;
}
p = SSL3_BUFFER_get_buf(wb) + prefix_len;
/* write the header */
*(p++) = type & 0xff;
SSL3_RECORD_set_type(&wr, type);
/*
* Special case: for hello verify request, client version 1.0 and we
* haven't decided which version to use yet send back using version 1.0
* header: otherwise some clients will ignore it.
*/
if (s->method->version == DTLS_ANY_VERSION &&
s->max_proto_version != DTLS1_BAD_VER) {
*(p++) = DTLS1_VERSION >> 8;
*(p++) = DTLS1_VERSION & 0xff;
} else {
*(p++) = s->version >> 8;
*(p++) = s->version & 0xff;
}
/* field where we are to write out packet epoch, seq num and len */
pseq = p;
p += 10;
/* Explicit IV length, block ciphers appropriate version flag */
if (s->enc_write_ctx) {
int mode = EVP_CIPHER_CTX_mode(s->enc_write_ctx);
if (mode == EVP_CIPH_CBC_MODE) {
eivlen = EVP_CIPHER_CTX_iv_length(s->enc_write_ctx);
if (eivlen <= 1)
eivlen = 0;
}
/* Need explicit part of IV for GCM mode */
else if (mode == EVP_CIPH_GCM_MODE)
eivlen = EVP_GCM_TLS_EXPLICIT_IV_LEN;
else if (mode == EVP_CIPH_CCM_MODE)
eivlen = EVP_CCM_TLS_EXPLICIT_IV_LEN;
else
eivlen = 0;
} else
eivlen = 0;
/* lets setup the record stuff. */
SSL3_RECORD_set_data(&wr, p + eivlen); /* make room for IV in case of CBC */
SSL3_RECORD_set_length(&wr, (int)len);
SSL3_RECORD_set_input(&wr, (unsigned char *)buf);
/*
* we now 'read' from wr.input, wr.length bytes into wr.data
*/
/* first we compress */
if (s->compress != NULL) {
if (!ssl3_do_compress(s, &wr)) {
SSLerr(SSL_F_DO_DTLS1_WRITE, SSL_R_COMPRESSION_FAILURE);
goto err;
}
} else {
memcpy(SSL3_RECORD_get_data(&wr), SSL3_RECORD_get_input(&wr),
SSL3_RECORD_get_length(&wr));
SSL3_RECORD_reset_input(&wr);
}
/*
* we should still have the output to wr.data and the input from
* wr.input. Length should be wr.length. wr.data still points in the
* wb->buf
*/
if (mac_size != 0) {
if (s->method->ssl3_enc->mac(s, &wr,
&(p[SSL3_RECORD_get_length(&wr) + eivlen]),
1) < 0)
goto err;
SSL3_RECORD_add_length(&wr, mac_size);
}
/* this is true regardless of mac size */
SSL3_RECORD_set_data(&wr, p);
SSL3_RECORD_reset_input(&wr);
if (eivlen)
SSL3_RECORD_add_length(&wr, eivlen);
if (s->method->ssl3_enc->enc(s, &wr, 1, 1) < 1)
goto err;
/* record length after mac and block padding */
/*
* if (type == SSL3_RT_APPLICATION_DATA || (type == SSL3_RT_ALERT && !
* SSL_in_init(s)))
*/
/* there's only one epoch between handshake and app data */
s2n(s->rlayer.d->w_epoch, pseq);
/* XDTLS: ?? */
/*
* else s2n(s->d1->handshake_epoch, pseq);
*/
memcpy(pseq, &(s->rlayer.write_sequence[2]), 6);
pseq += 6;
s2n(SSL3_RECORD_get_length(&wr), pseq);
if (s->msg_callback)
s->msg_callback(1, 0, SSL3_RT_HEADER, pseq - DTLS1_RT_HEADER_LENGTH,
DTLS1_RT_HEADER_LENGTH, s, s->msg_callback_arg);
/*
* we should now have wr.data pointing to the encrypted data, which is
* wr->length long
*/
SSL3_RECORD_set_type(&wr, type); /* not needed but helps for debugging */
SSL3_RECORD_add_length(&wr, DTLS1_RT_HEADER_LENGTH);
ssl3_record_sequence_update(&(s->rlayer.write_sequence[0]));
if (create_empty_fragment) {
/*
* we are in a recursive call; just return the length, don't write
* out anything here
*/
return wr.length;
}
/* now let's set up wb */
SSL3_BUFFER_set_left(wb, prefix_len + SSL3_RECORD_get_length(&wr));
SSL3_BUFFER_set_offset(wb, 0);
/*
* memorize arguments so that ssl3_write_pending can detect bad write
* retries later
*/
s->rlayer.wpend_tot = len;
s->rlayer.wpend_buf = buf;
s->rlayer.wpend_type = type;
s->rlayer.wpend_ret = len;
/* we now just need to write the buffer */
return ssl3_write_pending(s, type, buf, len);
err:
return -1;
}
DTLS1_BITMAP *dtls1_get_bitmap(SSL *s, SSL3_RECORD *rr,
unsigned int *is_next_epoch)
{
*is_next_epoch = 0;
/* In current epoch, accept HM, CCS, DATA, & ALERT */
if (rr->epoch == s->rlayer.d->r_epoch)
return &s->rlayer.d->bitmap;
/*
* Only HM and ALERT messages can be from the next epoch and only if we
* have already processed all of the unprocessed records from the last
* epoch
*/
else if (rr->epoch == (unsigned long)(s->rlayer.d->r_epoch + 1) &&
s->rlayer.d->unprocessed_rcds.epoch != s->rlayer.d->r_epoch &&
(rr->type == SSL3_RT_HANDSHAKE || rr->type == SSL3_RT_ALERT)) {
*is_next_epoch = 1;
return &s->rlayer.d->next_bitmap;
}
return NULL;
}
void dtls1_reset_seq_numbers(SSL *s, int rw)
{
unsigned char *seq;
unsigned int seq_bytes = sizeof(s->rlayer.read_sequence);
if (rw & SSL3_CC_READ) {
seq = s->rlayer.read_sequence;
s->rlayer.d->r_epoch++;
memcpy(&s->rlayer.d->bitmap, &s->rlayer.d->next_bitmap,
sizeof(s->rlayer.d->bitmap));
memset(&s->rlayer.d->next_bitmap, 0, sizeof(s->rlayer.d->next_bitmap));
/*
* We must not use any buffered messages received from the previous
* epoch
*/
dtls1_clear_received_buffer(s);
} else {
seq = s->rlayer.write_sequence;
memcpy(s->rlayer.d->last_write_sequence, seq,
sizeof(s->rlayer.write_sequence));
s->rlayer.d->w_epoch++;
}
memset(seq, 0, seq_bytes);
}
Reference in a new issue View git blame Copy permalink