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authorDaniel Borkmann <dborkman@redhat.com>2014-10-09 22:55:31 +0200
committerDavid S. Miller <davem@davemloft.net>2014-10-14 12:46:22 -0400
commit9de7922bc709eee2f609cd01d98aaedc4cf5ea74 (patch)
treeeb9da32f75f21c530beabda5a1014998e6ad41c3 /net/sctp
parentb838b4aced99e0d31a272396d43d9ca21cb078cb (diff)
net: sctp: fix skb_over_panic when receiving malformed ASCONF chunks
Commit 6f4c618ddb0 ("SCTP : Add paramters validity check for ASCONF chunk") added basic verification of ASCONF chunks, however, it is still possible to remotely crash a server by sending a special crafted ASCONF chunk, even up to pre 2.6.12 kernels: skb_over_panic: text:ffffffffa01ea1c3 len:31056 put:30768 head:ffff88011bd81800 data:ffff88011bd81800 tail:0x7950 end:0x440 dev:<NULL> ------------[ cut here ]------------ kernel BUG at net/core/skbuff.c:129! [...] Call Trace: <IRQ> [<ffffffff8144fb1c>] skb_put+0x5c/0x70 [<ffffffffa01ea1c3>] sctp_addto_chunk+0x63/0xd0 [sctp] [<ffffffffa01eadaf>] sctp_process_asconf+0x1af/0x540 [sctp] [<ffffffff8152d025>] ? _read_unlock_bh+0x15/0x20 [<ffffffffa01e0038>] sctp_sf_do_asconf+0x168/0x240 [sctp] [<ffffffffa01e3751>] sctp_do_sm+0x71/0x1210 [sctp] [<ffffffff8147645d>] ? fib_rules_lookup+0xad/0xf0 [<ffffffffa01e6b22>] ? sctp_cmp_addr_exact+0x32/0x40 [sctp] [<ffffffffa01e8393>] sctp_assoc_bh_rcv+0xd3/0x180 [sctp] [<ffffffffa01ee986>] sctp_inq_push+0x56/0x80 [sctp] [<ffffffffa01fcc42>] sctp_rcv+0x982/0xa10 [sctp] [<ffffffffa01d5123>] ? ipt_local_in_hook+0x23/0x28 [iptable_filter] [<ffffffff8148bdc9>] ? nf_iterate+0x69/0xb0 [<ffffffff81496d10>] ? ip_local_deliver_finish+0x0/0x2d0 [<ffffffff8148bf86>] ? nf_hook_slow+0x76/0x120 [<ffffffff81496d10>] ? ip_local_deliver_finish+0x0/0x2d0 [<ffffffff81496ded>] ip_local_deliver_finish+0xdd/0x2d0 [<ffffffff81497078>] ip_local_deliver+0x98/0xa0 [<ffffffff8149653d>] ip_rcv_finish+0x12d/0x440 [<ffffffff81496ac5>] ip_rcv+0x275/0x350 [<ffffffff8145c88b>] __netif_receive_skb+0x4ab/0x750 [<ffffffff81460588>] netif_receive_skb+0x58/0x60 This can be triggered e.g., through a simple scripted nmap connection scan injecting the chunk after the handshake, for example, ... -------------- INIT[ASCONF; ASCONF_ACK] -------------> <----------- INIT-ACK[ASCONF; ASCONF_ACK] ------------ -------------------- COOKIE-ECHO --------------------> <-------------------- COOKIE-ACK --------------------- ------------------ ASCONF; UNKNOWN ------------------> ... where ASCONF chunk of length 280 contains 2 parameters ... 1) Add IP address parameter (param length: 16) 2) Add/del IP address parameter (param length: 255) ... followed by an UNKNOWN chunk of e.g. 4 bytes. Here, the Address Parameter in the ASCONF chunk is even missing, too. This is just an example and similarly-crafted ASCONF chunks could be used just as well. The ASCONF chunk passes through sctp_verify_asconf() as all parameters passed sanity checks, and after walking, we ended up successfully at the chunk end boundary, and thus may invoke sctp_process_asconf(). Parameter walking is done with WORD_ROUND() to take padding into account. In sctp_process_asconf()'s TLV processing, we may fail in sctp_process_asconf_param() e.g., due to removal of the IP address that is also the source address of the packet containing the ASCONF chunk, and thus we need to add all TLVs after the failure to our ASCONF response to remote via helper function sctp_add_asconf_response(), which basically invokes a sctp_addto_chunk() adding the error parameters to the given skb. When walking to the next parameter this time, we proceed with ... length = ntohs(asconf_param->param_hdr.length); asconf_param = (void *)asconf_param + length; ... instead of the WORD_ROUND()'ed length, thus resulting here in an off-by-one that leads to reading the follow-up garbage parameter length of 12336, and thus throwing an skb_over_panic for the reply when trying to sctp_addto_chunk() next time, which implicitly calls the skb_put() with that length. Fix it by using sctp_walk_params() [ which is also used in INIT parameter processing ] macro in the verification *and* in ASCONF processing: it will make sure we don't spill over, that we walk parameters WORD_ROUND()'ed. Moreover, we're being more defensive and guard against unknown parameter types and missized addresses. Joint work with Vlad Yasevich. Fixes: b896b82be4ae ("[SCTP] ADDIP: Support for processing incoming ASCONF_ACK chunks.") Signed-off-by: Daniel Borkmann <dborkman@redhat.com> Signed-off-by: Vlad Yasevich <vyasevich@gmail.com> Acked-by: Neil Horman <nhorman@tuxdriver.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/sctp')
-rw-r--r--net/sctp/sm_make_chunk.c99
-rw-r--r--net/sctp/sm_statefuns.c18
2 files changed, 57 insertions, 60 deletions
diff --git a/net/sctp/sm_make_chunk.c b/net/sctp/sm_make_chunk.c
index ae0e616a7ca5..ab734be8cb20 100644
--- a/net/sctp/sm_make_chunk.c
+++ b/net/sctp/sm_make_chunk.c
@@ -3110,50 +3110,63 @@ static __be16 sctp_process_asconf_param(struct sctp_association *asoc,
return SCTP_ERROR_NO_ERROR;
}
-/* Verify the ASCONF packet before we process it. */
-int sctp_verify_asconf(const struct sctp_association *asoc,
- struct sctp_paramhdr *param_hdr, void *chunk_end,
- struct sctp_paramhdr **errp) {
- sctp_addip_param_t *asconf_param;
+/* Verify the ASCONF packet before we process it. */
+bool sctp_verify_asconf(const struct sctp_association *asoc,
+ struct sctp_chunk *chunk, bool addr_param_needed,
+ struct sctp_paramhdr **errp)
+{
+ sctp_addip_chunk_t *addip = (sctp_addip_chunk_t *) chunk->chunk_hdr;
union sctp_params param;
- int length, plen;
-
- param.v = (sctp_paramhdr_t *) param_hdr;
- while (param.v <= chunk_end - sizeof(sctp_paramhdr_t)) {
- length = ntohs(param.p->length);
- *errp = param.p;
+ bool addr_param_seen = false;
- if (param.v > chunk_end - length ||
- length < sizeof(sctp_paramhdr_t))
- return 0;
+ sctp_walk_params(param, addip, addip_hdr.params) {
+ size_t length = ntohs(param.p->length);
+ *errp = param.p;
switch (param.p->type) {
+ case SCTP_PARAM_ERR_CAUSE:
+ break;
+ case SCTP_PARAM_IPV4_ADDRESS:
+ if (length != sizeof(sctp_ipv4addr_param_t))
+ return false;
+ addr_param_seen = true;
+ break;
+ case SCTP_PARAM_IPV6_ADDRESS:
+ if (length != sizeof(sctp_ipv6addr_param_t))
+ return false;
+ addr_param_seen = true;
+ break;
case SCTP_PARAM_ADD_IP:
case SCTP_PARAM_DEL_IP:
case SCTP_PARAM_SET_PRIMARY:
- asconf_param = (sctp_addip_param_t *)param.v;
- plen = ntohs(asconf_param->param_hdr.length);
- if (plen < sizeof(sctp_addip_param_t) +
- sizeof(sctp_paramhdr_t))
- return 0;
+ /* In ASCONF chunks, these need to be first. */
+ if (addr_param_needed && !addr_param_seen)
+ return false;
+ length = ntohs(param.addip->param_hdr.length);
+ if (length < sizeof(sctp_addip_param_t) +
+ sizeof(sctp_paramhdr_t))
+ return false;
break;
case SCTP_PARAM_SUCCESS_REPORT:
case SCTP_PARAM_ADAPTATION_LAYER_IND:
if (length != sizeof(sctp_addip_param_t))
- return 0;
-
+ return false;
break;
default:
- break;
+ /* This is unkown to us, reject! */
+ return false;
}
-
- param.v += WORD_ROUND(length);
}
- if (param.v != chunk_end)
- return 0;
+ /* Remaining sanity checks. */
+ if (addr_param_needed && !addr_param_seen)
+ return false;
+ if (!addr_param_needed && addr_param_seen)
+ return false;
+ if (param.v != chunk->chunk_end)
+ return false;
- return 1;
+ return true;
}
/* Process an incoming ASCONF chunk with the next expected serial no. and
@@ -3162,16 +3175,17 @@ int sctp_verify_asconf(const struct sctp_association *asoc,
struct sctp_chunk *sctp_process_asconf(struct sctp_association *asoc,
struct sctp_chunk *asconf)
{
+ sctp_addip_chunk_t *addip = (sctp_addip_chunk_t *) asconf->chunk_hdr;
+ bool all_param_pass = true;
+ union sctp_params param;
sctp_addiphdr_t *hdr;
union sctp_addr_param *addr_param;
sctp_addip_param_t *asconf_param;
struct sctp_chunk *asconf_ack;
-
__be16 err_code;
int length = 0;
int chunk_len;
__u32 serial;
- int all_param_pass = 1;
chunk_len = ntohs(asconf->chunk_hdr->length) - sizeof(sctp_chunkhdr_t);
hdr = (sctp_addiphdr_t *)asconf->skb->data;
@@ -3199,9 +3213,14 @@ struct sctp_chunk *sctp_process_asconf(struct sctp_association *asoc,
goto done;
/* Process the TLVs contained within the ASCONF chunk. */
- while (chunk_len > 0) {
+ sctp_walk_params(param, addip, addip_hdr.params) {
+ /* Skip preceeding address parameters. */
+ if (param.p->type == SCTP_PARAM_IPV4_ADDRESS ||
+ param.p->type == SCTP_PARAM_IPV6_ADDRESS)
+ continue;
+
err_code = sctp_process_asconf_param(asoc, asconf,
- asconf_param);
+ param.addip);
/* ADDIP 4.1 A7)
* If an error response is received for a TLV parameter,
* all TLVs with no response before the failed TLV are
@@ -3209,28 +3228,20 @@ struct sctp_chunk *sctp_process_asconf(struct sctp_association *asoc,
* the failed response are considered unsuccessful unless
* a specific success indication is present for the parameter.
*/
- if (SCTP_ERROR_NO_ERROR != err_code)
- all_param_pass = 0;
-
+ if (err_code != SCTP_ERROR_NO_ERROR)
+ all_param_pass = false;
if (!all_param_pass)
- sctp_add_asconf_response(asconf_ack,
- asconf_param->crr_id, err_code,
- asconf_param);
+ sctp_add_asconf_response(asconf_ack, param.addip->crr_id,
+ err_code, param.addip);
/* ADDIP 4.3 D11) When an endpoint receiving an ASCONF to add
* an IP address sends an 'Out of Resource' in its response, it
* MUST also fail any subsequent add or delete requests bundled
* in the ASCONF.
*/
- if (SCTP_ERROR_RSRC_LOW == err_code)
+ if (err_code == SCTP_ERROR_RSRC_LOW)
goto done;
-
- /* Move to the next ASCONF param. */
- length = ntohs(asconf_param->param_hdr.length);
- asconf_param = (void *)asconf_param + length;
- chunk_len -= length;
}
-
done:
asoc->peer.addip_serial++;
diff --git a/net/sctp/sm_statefuns.c b/net/sctp/sm_statefuns.c
index c8f606324134..bdea3dfbad31 100644
--- a/net/sctp/sm_statefuns.c
+++ b/net/sctp/sm_statefuns.c
@@ -3591,9 +3591,7 @@ sctp_disposition_t sctp_sf_do_asconf(struct net *net,
struct sctp_chunk *asconf_ack = NULL;
struct sctp_paramhdr *err_param = NULL;
sctp_addiphdr_t *hdr;
- union sctp_addr_param *addr_param;
__u32 serial;
- int length;
if (!sctp_vtag_verify(chunk, asoc)) {
sctp_add_cmd_sf(commands, SCTP_CMD_REPORT_BAD_TAG,
@@ -3618,17 +3616,8 @@ sctp_disposition_t sctp_sf_do_asconf(struct net *net,
hdr = (sctp_addiphdr_t *)chunk->skb->data;
serial = ntohl(hdr->serial);
- addr_param = (union sctp_addr_param *)hdr->params;
- length = ntohs(addr_param->p.length);
- if (length < sizeof(sctp_paramhdr_t))
- return sctp_sf_violation_paramlen(net, ep, asoc, type, arg,
- (void *)addr_param, commands);
-
/* Verify the ASCONF chunk before processing it. */
- if (!sctp_verify_asconf(asoc,
- (sctp_paramhdr_t *)((void *)addr_param + length),
- (void *)chunk->chunk_end,
- &err_param))
+ if (!sctp_verify_asconf(asoc, chunk, true, &err_param))
return sctp_sf_violation_paramlen(net, ep, asoc, type, arg,
(void *)err_param, commands);
@@ -3745,10 +3734,7 @@ sctp_disposition_t sctp_sf_do_asconf_ack(struct net *net,
rcvd_serial = ntohl(addip_hdr->serial);
/* Verify the ASCONF-ACK chunk before processing it. */
- if (!sctp_verify_asconf(asoc,
- (sctp_paramhdr_t *)addip_hdr->params,
- (void *)asconf_ack->chunk_end,
- &err_param))
+ if (!sctp_verify_asconf(asoc, asconf_ack, false, &err_param))
return sctp_sf_violation_paramlen(net, ep, asoc, type, arg,
(void *)err_param, commands);

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