From: Xin Long lucien.xin@gmail.com
commit eae5783908042a762c24e1bd11876edb91d314b1 upstream.
This patch fixes the problems below:
1. In non-shutdown_ack_sent states: in sctp_sf_do_5_1B_init() and sctp_sf_do_5_2_2_dupinit():
chunk length check should be done before any checks that may cause to send abort, as making packet for abort will access the init_tag from init_hdr in sctp_ootb_pkt_new().
2. In shutdown_ack_sent state: in sctp_sf_do_9_2_reshutack():
The same checks as does in sctp_sf_do_5_2_2_dupinit() is needed for sctp_sf_do_9_2_reshutack().
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: Xin Long lucien.xin@gmail.com Acked-by: Marcelo Ricardo Leitner marcelo.leitner@gmail.com Signed-off-by: Jakub Kicinski kuba@kernel.org [OP: adjusted context for 4.19] Signed-off-by: Ovidiu Panait ovidiu.panait@windriver.com --- CVE-2021-3772 patchset consists of 7 fixes: [1] 4f7019c7eb33 ("sctp: use init_tag from inithdr for ABORT chunk") [2] eae578390804 ("sctp: fix the processing for INIT chunk") [3] 438b95a7c98f ("sctp: fix the processing for INIT_ACK chunk") [4] a64b341b8695 ("sctp: fix the processing for COOKIE_ECHO chunk") [5] aa0f697e4528 ("sctp: add vtag check in sctp_sf_violation") [6] ef16b1734f0a ("sctp: add vtag check in sctp_sf_do_8_5_1_E_sa") [7] 9d02831e517a ("sctp: add vtag check in sctp_sf_ootb")
This series contains backports for [2] and [3], which are the only fixes missing from 4.19-stable. Only small contextual adjustments were made.
net/sctp/sm_statefuns.c | 71 ++++++++++++++++++++++++++--------------- 1 file changed, 46 insertions(+), 25 deletions(-)
diff --git a/net/sctp/sm_statefuns.c b/net/sctp/sm_statefuns.c index ebca069064df..5e17df88df5d 100644 --- a/net/sctp/sm_statefuns.c +++ b/net/sctp/sm_statefuns.c @@ -164,6 +164,12 @@ static enum sctp_disposition __sctp_sf_do_9_1_abort( void *arg, struct sctp_cmd_seq *commands);
+static enum sctp_disposition +__sctp_sf_do_9_2_reshutack(struct net *net, const struct sctp_endpoint *ep, + const struct sctp_association *asoc, + const union sctp_subtype type, void *arg, + struct sctp_cmd_seq *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. @@ -345,6 +351,14 @@ enum sctp_disposition sctp_sf_do_5_1B_init(struct net *net, if (!chunk->singleton) return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);
+ /* Make sure that the INIT chunk has a valid length. + * Normally, this would cause an ABORT with a Protocol Violation + * error, but since we don't have an association, we'll + * just discard the packet. + */ + if (!sctp_chunk_length_valid(chunk, sizeof(struct sctp_init_chunk))) + return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands); + /* If the packet is an OOTB packet which is temporarily on the * control endpoint, respond with an ABORT. */ @@ -359,14 +373,6 @@ enum sctp_disposition sctp_sf_do_5_1B_init(struct net *net, if (chunk->sctp_hdr->vtag != 0) return sctp_sf_tabort_8_4_8(net, ep, asoc, type, arg, commands);
- /* Make sure that the INIT chunk has a valid length. - * Normally, this would cause an ABORT with a Protocol Violation - * error, but since we don't have an association, we'll - * just discard the packet. - */ - if (!sctp_chunk_length_valid(chunk, sizeof(struct sctp_init_chunk))) - return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands); - /* If the INIT is coming toward a closing socket, we'll send back * and ABORT. Essentially, this catches the race of INIT being * backloged to the socket at the same time as the user isses close(). @@ -1499,19 +1505,16 @@ static enum sctp_disposition sctp_sf_do_unexpected_init( if (!chunk->singleton) return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);
+ /* Make sure that the INIT chunk has a valid length. */ + if (!sctp_chunk_length_valid(chunk, sizeof(struct sctp_init_chunk))) + return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands); + /* 3.1 A packet containing an INIT chunk MUST have a zero Verification * Tag. */ if (chunk->sctp_hdr->vtag != 0) return sctp_sf_tabort_8_4_8(net, ep, asoc, type, arg, commands);
- /* Make sure that the INIT chunk has a valid length. - * In this case, we generate a protocol violation since we have - * an association established. - */ - if (!sctp_chunk_length_valid(chunk, sizeof(struct sctp_init_chunk))) - return sctp_sf_violation_chunklen(net, ep, asoc, type, arg, - commands); /* Grab the INIT header. */ chunk->subh.init_hdr = (struct sctp_inithdr *)chunk->skb->data;
@@ -1829,9 +1832,9 @@ static enum sctp_disposition sctp_sf_do_dupcook_a( * its peer. */ if (sctp_state(asoc, SHUTDOWN_ACK_SENT)) { - disposition = sctp_sf_do_9_2_reshutack(net, ep, asoc, - SCTP_ST_CHUNK(chunk->chunk_hdr->type), - chunk, commands); + disposition = __sctp_sf_do_9_2_reshutack(net, ep, asoc, + SCTP_ST_CHUNK(chunk->chunk_hdr->type), + chunk, commands); if (SCTP_DISPOSITION_NOMEM == disposition) goto nomem;
@@ -2930,13 +2933,11 @@ enum sctp_disposition sctp_sf_do_9_2_shut_ctsn( * that belong to this association, it should discard the INIT chunk and * retransmit the SHUTDOWN ACK chunk. */ -enum sctp_disposition sctp_sf_do_9_2_reshutack( - struct net *net, - const struct sctp_endpoint *ep, - const struct sctp_association *asoc, - const union sctp_subtype type, - void *arg, - struct sctp_cmd_seq *commands) +static enum sctp_disposition +__sctp_sf_do_9_2_reshutack(struct net *net, const struct sctp_endpoint *ep, + const struct sctp_association *asoc, + const union sctp_subtype type, void *arg, + struct sctp_cmd_seq *commands) { struct sctp_chunk *chunk = arg; struct sctp_chunk *reply; @@ -2970,6 +2971,26 @@ enum sctp_disposition sctp_sf_do_9_2_reshutack( return SCTP_DISPOSITION_NOMEM; }
+enum sctp_disposition +sctp_sf_do_9_2_reshutack(struct net *net, const struct sctp_endpoint *ep, + const struct sctp_association *asoc, + const union sctp_subtype type, void *arg, + struct sctp_cmd_seq *commands) +{ + struct sctp_chunk *chunk = arg; + + if (!chunk->singleton) + return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands); + + if (!sctp_chunk_length_valid(chunk, sizeof(struct sctp_init_chunk))) + return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands); + + if (chunk->sctp_hdr->vtag != 0) + return sctp_sf_tabort_8_4_8(net, ep, asoc, type, arg, commands); + + return __sctp_sf_do_9_2_reshutack(net, ep, asoc, type, arg, commands); +} + /* * sctp_sf_do_ecn_cwr *
From: Xin Long lucien.xin@gmail.com
commit 438b95a7c98f77d51cbf4db021f41b602d750a3f upstream.
Currently INIT_ACK chunk in non-cookie_echoed state is processed in sctp_sf_discard_chunk() to send an abort with the existent asoc's vtag if the chunk length is not valid. But the vtag in the chunk's sctphdr is not verified, which may be exploited by one to cook a malicious chunk to terminal a SCTP asoc.
sctp_sf_discard_chunk() also is called in many other places to send an abort, and most of those have this problem. This patch is to fix it by sending abort with the existent asoc's vtag only if the vtag from the chunk's sctphdr is verified in sctp_sf_discard_chunk().
Note on sctp_sf_do_9_1_abort() and sctp_sf_shutdown_pending_abort(), the chunk length has been verified before sctp_sf_discard_chunk(), so replace it with sctp_sf_discard(). On sctp_sf_do_asconf_ack() and sctp_sf_do_asconf(), move the sctp_chunk_length_valid check ahead of sctp_sf_discard_chunk(), then replace it with sctp_sf_discard().
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: Xin Long lucien.xin@gmail.com Acked-by: Marcelo Ricardo Leitner marcelo.leitner@gmail.com Signed-off-by: Jakub Kicinski kuba@kernel.org [OP: adjusted context for 4.19] Signed-off-by: Ovidiu Panait ovidiu.panait@windriver.com --- net/sctp/sm_statefuns.c | 37 +++++++++++++++++++------------------ 1 file changed, 19 insertions(+), 18 deletions(-)
diff --git a/net/sctp/sm_statefuns.c b/net/sctp/sm_statefuns.c index 5e17df88df5d..3d52431dea9b 100644 --- a/net/sctp/sm_statefuns.c +++ b/net/sctp/sm_statefuns.c @@ -2304,7 +2304,7 @@ enum sctp_disposition sctp_sf_shutdown_pending_abort( */ if (SCTP_ADDR_DEL == sctp_bind_addr_state(&asoc->base.bind_addr, &chunk->dest)) - return sctp_sf_discard_chunk(net, ep, asoc, type, arg, commands); + return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);
if (!sctp_err_chunk_valid(chunk)) return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands); @@ -2350,7 +2350,7 @@ enum sctp_disposition sctp_sf_shutdown_sent_abort( */ if (SCTP_ADDR_DEL == sctp_bind_addr_state(&asoc->base.bind_addr, &chunk->dest)) - return sctp_sf_discard_chunk(net, ep, asoc, type, arg, commands); + return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);
if (!sctp_err_chunk_valid(chunk)) return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands); @@ -2620,7 +2620,7 @@ enum sctp_disposition sctp_sf_do_9_1_abort( */ if (SCTP_ADDR_DEL == sctp_bind_addr_state(&asoc->base.bind_addr, &chunk->dest)) - return sctp_sf_discard_chunk(net, ep, asoc, type, arg, commands); + return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);
if (!sctp_err_chunk_valid(chunk)) return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands); @@ -3787,6 +3787,11 @@ enum sctp_disposition sctp_sf_do_asconf(struct net *net, return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands); }
+ /* Make sure that the ASCONF ADDIP chunk has a valid length. */ + if (!sctp_chunk_length_valid(chunk, sizeof(struct sctp_addip_chunk))) + return sctp_sf_violation_chunklen(net, ep, asoc, type, arg, + commands); + /* ADD-IP: Section 4.1.1 * This chunk MUST be sent in an authenticated way by using * the mechanism defined in [I-D.ietf-tsvwg-sctp-auth]. If this chunk @@ -3794,13 +3799,7 @@ enum sctp_disposition sctp_sf_do_asconf(struct net *net, * described in [I-D.ietf-tsvwg-sctp-auth]. */ if (!net->sctp.addip_noauth && !chunk->auth) - return sctp_sf_discard_chunk(net, ep, asoc, type, arg, - commands); - - /* Make sure that the ASCONF ADDIP chunk has a valid length. */ - if (!sctp_chunk_length_valid(chunk, sizeof(struct sctp_addip_chunk))) - return sctp_sf_violation_chunklen(net, ep, asoc, type, arg, - commands); + return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);
hdr = (struct sctp_addiphdr *)chunk->skb->data; serial = ntohl(hdr->serial); @@ -3929,6 +3928,12 @@ enum sctp_disposition sctp_sf_do_asconf_ack(struct net *net, return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands); }
+ /* Make sure that the ADDIP chunk has a valid length. */ + if (!sctp_chunk_length_valid(asconf_ack, + sizeof(struct sctp_addip_chunk))) + return sctp_sf_violation_chunklen(net, ep, asoc, type, arg, + commands); + /* ADD-IP, Section 4.1.2: * This chunk MUST be sent in an authenticated way by using * the mechanism defined in [I-D.ietf-tsvwg-sctp-auth]. If this chunk @@ -3936,14 +3941,7 @@ enum sctp_disposition sctp_sf_do_asconf_ack(struct net *net, * described in [I-D.ietf-tsvwg-sctp-auth]. */ if (!net->sctp.addip_noauth && !asconf_ack->auth) - return sctp_sf_discard_chunk(net, ep, asoc, type, arg, - commands); - - /* Make sure that the ADDIP chunk has a valid length. */ - if (!sctp_chunk_length_valid(asconf_ack, - sizeof(struct sctp_addip_chunk))) - return sctp_sf_violation_chunklen(net, ep, asoc, type, arg, - commands); + return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands);
addip_hdr = (struct sctp_addiphdr *)asconf_ack->skb->data; rcvd_serial = ntohl(addip_hdr->serial); @@ -4515,6 +4513,9 @@ enum sctp_disposition sctp_sf_discard_chunk(struct net *net, { struct sctp_chunk *chunk = arg;
+ if (asoc && !sctp_vtag_verify(chunk, asoc)) + return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands); + /* 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.
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