From ef16b1734f0a176277b7bb9c71a6d977a6ef3998 Mon Sep 17 00:00:00 2001 From: Xin Long Date: Wed, 20 Oct 2021 07:42:46 -0400 Subject: [PATCH] sctp: add vtag check in sctp_sf_do_8_5_1_E_sa sctp_sf_do_8_5_1_E_sa() is called when processing SHUTDOWN_ACK chunk in cookie_wait and cookie_echoed state. The vtag in the chunk's sctphdr should be verified, otherwise, as later in chunk length check, it may send abort with the existent asoc's vtag, which can be exploited by one to cook a malicious chunk to terminate a SCTP asoc. Note that when fails to verify the vtag from SHUTDOWN-ACK chunk, SHUTDOWN COMPLETE message will still be sent back to peer, but with the vtag from SHUTDOWN-ACK chunk, as said in 5) of rfc4960#section-8.4. While at it, also remove the unnecessary chunk length check from sctp_sf_shut_8_4_5(), as it's already done in both places where it calls sctp_sf_shut_8_4_5(). Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: Xin Long Acked-by: Marcelo Ricardo Leitner Signed-off-by: Jakub Kicinski --- net/sctp/sm_statefuns.c | 9 +++------ 1 file changed, 3 insertions(+), 6 deletions(-) diff --git a/net/sctp/sm_statefuns.c b/net/sctp/sm_statefuns.c index 36328ab..a354549 100644 --- a/net/sctp/sm_statefuns.c +++ b/net/sctp/sm_statefuns.c @@ -3803,12 +3803,6 @@ static enum sctp_disposition sctp_sf_shut_8_4_5( SCTP_INC_STATS(net, SCTP_MIB_OUTCTRLCHUNKS); - /* If the chunk length is invalid, we don't want to process - * the reset of the packet. - */ - if (!sctp_chunk_length_valid(chunk, sizeof(struct sctp_chunkhdr))) - return sctp_sf_pdiscard(net, ep, asoc, type, arg, commands); - /* We need to discard the rest of the packet to prevent * potential boomming attacks from additional bundled chunks. * This is documented in SCTP Threats ID. @@ -3836,6 +3830,9 @@ enum sctp_disposition sctp_sf_do_8_5_1_E_sa(struct net *net, { struct sctp_chunk *chunk = arg; + if (!sctp_vtag_verify(chunk, asoc)) + asoc = NULL; + /* Make sure that the SHUTDOWN_ACK chunk has a valid length. */ if (!sctp_chunk_length_valid(chunk, sizeof(struct sctp_chunkhdr))) return sctp_sf_violation_chunklen(net, ep, asoc, type, arg, -- 2.7.4