SCTP: Clean up OOTB handling and fix infinite loop processing
While processing OOTB chunks as well as chunks with an invalid
length of 0, it was possible to SCTP to get wedged inside an
infinite loop because we didn't catch the condition correctly,
or didn't mark the packet for discard correctly.
This work is based on original findings and work by
Wei Yongjun <yjwei@cn.fujitsu.com>
Signed-off-by: Vlad Yasevich <vladislav.yasevich@hp.com>
diff --git a/net/sctp/sm_statefuns.c b/net/sctp/sm_statefuns.c
index 5e7fb0f..caed19d 100644
--- a/net/sctp/sm_statefuns.c
+++ b/net/sctp/sm_statefuns.c
@@ -90,6 +90,11 @@
const sctp_subtype_t type,
void *arg,
sctp_cmd_seq_t *commands);
+static sctp_disposition_t sctp_sf_tabort_8_4_8(const struct sctp_endpoint *ep,
+ const struct sctp_association *asoc,
+ const sctp_subtype_t type,
+ void *arg,
+ sctp_cmd_seq_t *commands);
static struct sctp_sackhdr *sctp_sm_pull_sack(struct sctp_chunk *chunk);
static sctp_disposition_t sctp_stop_t1_and_abort(sctp_cmd_seq_t *commands,
@@ -98,6 +103,7 @@
struct sctp_transport *transport);
static sctp_disposition_t sctp_sf_abort_violation(
+ const struct sctp_endpoint *ep,
const struct sctp_association *asoc,
void *arg,
sctp_cmd_seq_t *commands,
@@ -118,6 +124,13 @@
void *arg,
sctp_cmd_seq_t *commands);
+static sctp_disposition_t sctp_sf_violation_chunk(
+ const struct sctp_endpoint *ep,
+ const struct sctp_association *asoc,
+ const sctp_subtype_t type,
+ void *arg,
+ sctp_cmd_seq_t *commands);
+
/* Small helper function that checks if the chunk length
* is of the appropriate length. The 'required_length' argument
* is set to be the size of a specific chunk we are testing.
@@ -181,16 +194,21 @@
struct sctp_chunk *chunk = arg;
struct sctp_ulpevent *ev;
+ if (!sctp_vtag_verify_either(chunk, asoc))
+ return sctp_sf_pdiscard(ep, asoc, type, arg, commands);
+
/* RFC 2960 6.10 Bundling
*
* An endpoint MUST NOT bundle INIT, INIT ACK or
* SHUTDOWN COMPLETE with any other chunks.
*/
if (!chunk->singleton)
- return SCTP_DISPOSITION_VIOLATION;
+ return sctp_sf_violation_chunk(ep, asoc, type, arg, commands);
- if (!sctp_vtag_verify_either(chunk, asoc))
- return sctp_sf_pdiscard(ep, asoc, type, arg, commands);
+ /* Make sure that the SHUTDOWN_COMPLETE chunk has a valid length. */
+ if (!sctp_chunk_length_valid(chunk, sizeof(sctp_chunkhdr_t)))
+ return sctp_sf_violation_chunklen(ep, asoc, type, arg,
+ commands);
/* RFC 2960 10.2 SCTP-to-ULP
*
@@ -450,17 +468,17 @@
if (!sctp_vtag_verify(chunk, asoc))
return sctp_sf_pdiscard(ep, asoc, type, arg, commands);
- /* Make sure that the INIT-ACK chunk has a valid length */
- if (!sctp_chunk_length_valid(chunk, sizeof(sctp_initack_chunk_t)))
- return sctp_sf_violation_chunklen(ep, asoc, type, arg,
- commands);
/* 6.10 Bundling
* An endpoint MUST NOT bundle INIT, INIT ACK or
* SHUTDOWN COMPLETE with any other chunks.
*/
if (!chunk->singleton)
- return SCTP_DISPOSITION_VIOLATION;
+ return sctp_sf_violation_chunk(ep, asoc, type, arg, commands);
+ /* Make sure that the INIT-ACK chunk has a valid length */
+ if (!sctp_chunk_length_valid(chunk, sizeof(sctp_initack_chunk_t)))
+ return sctp_sf_violation_chunklen(ep, asoc, type, arg,
+ commands);
/* Grab the INIT header. */
chunk->subh.init_hdr = (sctp_inithdr_t *) chunk->skb->data;
@@ -585,7 +603,7 @@
* control endpoint, respond with an ABORT.
*/
if (ep == sctp_sk((sctp_get_ctl_sock()))->ep)
- return sctp_sf_ootb(ep, asoc, type, arg, commands);
+ return sctp_sf_tabort_8_4_8(ep, asoc, type, arg, commands);
/* Make sure that the COOKIE_ECHO chunk has a valid length.
* In this case, we check that we have enough for at least a
@@ -2496,6 +2514,11 @@
struct sctp_chunk *chunk = (struct sctp_chunk *) arg;
struct sctp_chunk *reply;
+ /* Make sure that the chunk has a valid length */
+ if (!sctp_chunk_length_valid(chunk, sizeof(sctp_chunkhdr_t)))
+ return sctp_sf_violation_chunklen(ep, asoc, type, arg,
+ commands);
+
/* Since we are not going to really process this INIT, there
* is no point in verifying chunk boundries. Just generate
* the SHUTDOWN ACK.
@@ -2929,7 +2952,7 @@
*
* The return value is the disposition of the chunk.
*/
-sctp_disposition_t sctp_sf_tabort_8_4_8(const struct sctp_endpoint *ep,
+static sctp_disposition_t sctp_sf_tabort_8_4_8(const struct sctp_endpoint *ep,
const struct sctp_association *asoc,
const sctp_subtype_t type,
void *arg,
@@ -3126,14 +3149,14 @@
ch = (sctp_chunkhdr_t *) chunk->chunk_hdr;
do {
- /* Break out if chunk length is less then minimal. */
+ /* Report violation if the chunk is less then minimal */
if (ntohs(ch->length) < sizeof(sctp_chunkhdr_t))
- break;
+ return sctp_sf_violation_chunklen(ep, asoc, type, arg,
+ commands);
- ch_end = ((__u8 *)ch) + WORD_ROUND(ntohs(ch->length));
- if (ch_end > skb_tail_pointer(skb))
- break;
-
+ /* Now that we know we at least have a chunk header,
+ * do things that are type appropriate.
+ */
if (SCTP_CID_SHUTDOWN_ACK == ch->type)
ootb_shut_ack = 1;
@@ -3145,6 +3168,12 @@
if (SCTP_CID_ABORT == ch->type)
return sctp_sf_pdiscard(ep, asoc, type, arg, commands);
+ /* Report violation if chunk len overflows */
+ ch_end = ((__u8 *)ch) + WORD_ROUND(ntohs(ch->length));
+ if (ch_end > skb_tail_pointer(skb))
+ return sctp_sf_violation_chunklen(ep, asoc, type, arg,
+ commands);
+
ch = (sctp_chunkhdr_t *) ch_end;
} while (ch_end < skb_tail_pointer(skb));
@@ -3244,6 +3273,13 @@
void *arg,
sctp_cmd_seq_t *commands)
{
+ struct sctp_chunk *chunk = arg;
+
+ /* Make sure that the SHUTDOWN_ACK chunk has a valid length. */
+ if (!sctp_chunk_length_valid(chunk, sizeof(sctp_chunkhdr_t)))
+ return sctp_sf_violation_chunklen(ep, asoc, type, arg,
+ commands);
+
/* Although we do have an association in this case, it corresponds
* to a restarted association. So the packet is treated as an OOTB
* packet and the state function that handles OOTB SHUTDOWN_ACK is
@@ -3658,6 +3694,16 @@
void *arg,
sctp_cmd_seq_t *commands)
{
+ struct sctp_chunk *chunk = arg;
+
+ /* Make sure that the chunk has a valid length.
+ * Since we don't know the chunk type, we use a general
+ * chunkhdr structure to make a comparison.
+ */
+ if (!sctp_chunk_length_valid(chunk, sizeof(sctp_chunkhdr_t)))
+ return sctp_sf_violation_chunklen(ep, asoc, type, arg,
+ commands);
+
SCTP_DEBUG_PRINTK("Chunk %d is discarded\n", type.chunk);
return SCTP_DISPOSITION_DISCARD;
}
@@ -3713,6 +3759,13 @@
void *arg,
sctp_cmd_seq_t *commands)
{
+ struct sctp_chunk *chunk = arg;
+
+ /* Make sure that the chunk has a valid length. */
+ if (!sctp_chunk_length_valid(chunk, sizeof(sctp_chunkhdr_t)))
+ return sctp_sf_violation_chunklen(ep, asoc, type, arg,
+ commands);
+
return SCTP_DISPOSITION_VIOLATION;
}
@@ -3720,12 +3773,14 @@
* Common function to handle a protocol violation.
*/
static sctp_disposition_t sctp_sf_abort_violation(
+ const struct sctp_endpoint *ep,
const struct sctp_association *asoc,
void *arg,
sctp_cmd_seq_t *commands,
const __u8 *payload,
const size_t paylen)
{
+ struct sctp_packet *packet = NULL;
struct sctp_chunk *chunk = arg;
struct sctp_chunk *abort = NULL;
@@ -3734,30 +3789,51 @@
if (!abort)
goto nomem;
- sctp_add_cmd_sf(commands, SCTP_CMD_REPLY, SCTP_CHUNK(abort));
- SCTP_INC_STATS(SCTP_MIB_OUTCTRLCHUNKS);
+ if (asoc) {
+ sctp_add_cmd_sf(commands, SCTP_CMD_REPLY, SCTP_CHUNK(abort));
+ SCTP_INC_STATS(SCTP_MIB_OUTCTRLCHUNKS);
- if (asoc->state <= SCTP_STATE_COOKIE_ECHOED) {
- sctp_add_cmd_sf(commands, SCTP_CMD_TIMER_STOP,
- SCTP_TO(SCTP_EVENT_TIMEOUT_T1_INIT));
- sctp_add_cmd_sf(commands, SCTP_CMD_SET_SK_ERR,
- SCTP_ERROR(ECONNREFUSED));
- sctp_add_cmd_sf(commands, SCTP_CMD_INIT_FAILED,
- SCTP_PERR(SCTP_ERROR_PROTO_VIOLATION));
+ if (asoc->state <= SCTP_STATE_COOKIE_ECHOED) {
+ sctp_add_cmd_sf(commands, SCTP_CMD_TIMER_STOP,
+ SCTP_TO(SCTP_EVENT_TIMEOUT_T1_INIT));
+ sctp_add_cmd_sf(commands, SCTP_CMD_SET_SK_ERR,
+ SCTP_ERROR(ECONNREFUSED));
+ sctp_add_cmd_sf(commands, SCTP_CMD_INIT_FAILED,
+ SCTP_PERR(SCTP_ERROR_PROTO_VIOLATION));
+ } else {
+ sctp_add_cmd_sf(commands, SCTP_CMD_SET_SK_ERR,
+ SCTP_ERROR(ECONNABORTED));
+ sctp_add_cmd_sf(commands, SCTP_CMD_ASSOC_FAILED,
+ SCTP_PERR(SCTP_ERROR_PROTO_VIOLATION));
+ SCTP_DEC_STATS(SCTP_MIB_CURRESTAB);
+ }
} else {
- sctp_add_cmd_sf(commands, SCTP_CMD_SET_SK_ERR,
- SCTP_ERROR(ECONNABORTED));
- sctp_add_cmd_sf(commands, SCTP_CMD_ASSOC_FAILED,
- SCTP_PERR(SCTP_ERROR_PROTO_VIOLATION));
- SCTP_DEC_STATS(SCTP_MIB_CURRESTAB);
+ packet = sctp_ootb_pkt_new(asoc, chunk);
+
+ if (!packet)
+ goto nomem_pkt;
+
+ if (sctp_test_T_bit(abort))
+ packet->vtag = ntohl(chunk->sctp_hdr->vtag);
+
+ abort->skb->sk = ep->base.sk;
+
+ sctp_packet_append_chunk(packet, abort);
+
+ sctp_add_cmd_sf(commands, SCTP_CMD_SEND_PKT,
+ SCTP_PACKET(packet));
+
+ SCTP_INC_STATS(SCTP_MIB_OUTCTRLCHUNKS);
}
- sctp_add_cmd_sf(commands, SCTP_CMD_DISCARD_PACKET, SCTP_NULL());
+ sctp_sf_pdiscard(ep, asoc, SCTP_ST_CHUNK(0), arg, commands);
SCTP_INC_STATS(SCTP_MIB_ABORTEDS);
return SCTP_DISPOSITION_ABORT;
+nomem_pkt:
+ sctp_chunk_free(abort);
nomem:
return SCTP_DISPOSITION_NOMEM;
}
@@ -3790,7 +3866,7 @@
{
char err_str[]="The following chunk had invalid length:";
- return sctp_sf_abort_violation(asoc, arg, commands, err_str,
+ return sctp_sf_abort_violation(ep, asoc, arg, commands, err_str,
sizeof(err_str));
}
@@ -3809,10 +3885,31 @@
{
char err_str[]="The cumulative tsn ack beyond the max tsn currently sent:";
- return sctp_sf_abort_violation(asoc, arg, commands, err_str,
+ return sctp_sf_abort_violation(ep, asoc, arg, commands, err_str,
sizeof(err_str));
}
+/* Handle protocol violation of an invalid chunk bundling. For example,
+ * when we have an association and we recieve bundled INIT-ACK, or
+ * SHUDOWN-COMPLETE, our peer is clearly violationg the "MUST NOT bundle"
+ * statement from the specs. Additinally, there might be an attacker
+ * on the path and we may not want to continue this communication.
+ */
+static sctp_disposition_t sctp_sf_violation_chunk(
+ const struct sctp_endpoint *ep,
+ const struct sctp_association *asoc,
+ const sctp_subtype_t type,
+ void *arg,
+ sctp_cmd_seq_t *commands)
+{
+ char err_str[]="The following chunk violates protocol:";
+
+ if (!asoc)
+ return sctp_sf_violation(ep, asoc, type, arg, commands);
+
+ return sctp_sf_abort_violation(ep, asoc, arg, commands, err_str,
+ sizeof(err_str));
+}
/***************************************************************************
* These are the state functions for handling primitive (Section 10) events.
***************************************************************************/