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The racoon daemon in IPsec-Tools 0.8.2 contains a remotely exploitable computational-complexity attack when parsing and storing ISAKMP fragments. The implementation permits a remote attacker to exhaust computational resources on the remote endpoint by repeatedly sending ISAKMP fragment packets in a particular order such that the worst-case computational complexity is realized in the algorithm utilized to determine if reassembly of the fragments can take place. The fix obtained from NetBSD CVS head with a command: cvs diff -D 2017-01-24 -D 2017-09-01 \ src/racoon/handler.h \ src/racoon/isakmp.c \ src/racoon/isakmp_frag.c \ src/racoon/isakmp_inf.c While here, add LICENSE. PR: 225066 Approved by: VANHULLEBUS Yvan (maintainer timeout, 3 months) Obtained from: NetBSD MFH: 2018Q1 Security: CVE-2016-10396
151 lines
4 KiB
C
151 lines
4 KiB
C
Index: src/racoon/isakmp_frag.c
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===================================================================
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RCS file: /cvsroot/src/crypto/dist/ipsec-tools/src/racoon/isakmp_frag.c,v
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retrieving revision 1.5
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retrieving revision 1.7
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diff -p -u -r1.5 -r1.7
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--- src/racoon/isakmp_frag.c 22 Apr 2009 11:24:20 -0000 1.5
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+++ src/racoon/isakmp_frag.c 23 Jul 2017 05:40:27 -0000 1.7
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@@ -1,4 +1,4 @@
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-/* $NetBSD: isakmp_frag.c,v 1.5 2009/04/22 11:24:20 tteras Exp $ */
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+/* $NetBSD: isakmp_frag.c,v 1.7 2017/07/23 05:40:27 christos Exp $ */
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/* Id: isakmp_frag.c,v 1.4 2004/11/13 17:31:36 manubsd Exp */
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@@ -173,6 +173,43 @@ vendorid_frag_cap(gen)
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return ntohl(hp[MD5_DIGEST_LENGTH / sizeof(*hp)]);
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}
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+static int
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+isakmp_frag_insert(struct ph1handle *iph1, struct isakmp_frag_item *item)
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+{
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+ struct isakmp_frag_item *pitem = NULL;
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+ struct isakmp_frag_item *citem = iph1->frag_chain;
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+
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+ /* no frag yet, just insert at beginning of list */
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+ if (iph1->frag_chain == NULL) {
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+ iph1->frag_chain = item;
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+ return 0;
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+ }
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+
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+ do {
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+ /* duplicate fragment number, abort (CVE-2016-10396) */
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+ if (citem->frag_num == item->frag_num)
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+ return -1;
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+
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+ /* need to insert before current item */
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+ if (citem->frag_num > item->frag_num) {
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+ if (pitem != NULL)
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+ pitem->frag_next = item;
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+ else
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+ /* insert at the beginning of the list */
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+ iph1->frag_chain = item;
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+ item->frag_next = citem;
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+ return 0;
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+ }
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+
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+ pitem = citem;
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+ citem = citem->frag_next;
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+ } while (citem != NULL);
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+
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+ /* we reached the end of the list, insert */
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+ pitem->frag_next = item;
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+ return 0;
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+}
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+
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int
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isakmp_frag_extract(iph1, msg)
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struct ph1handle *iph1;
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@@ -224,39 +261,43 @@ isakmp_frag_extract(iph1, msg)
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item->frag_next = NULL;
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item->frag_packet = buf;
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- /* Look for the last frag while inserting the new item in the chain */
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- if (item->frag_last)
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- last_frag = item->frag_num;
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+ /* Check for the last frag before inserting the new item in the chain */
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+ if (item->frag_last) {
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+ /* if we have the last fragment, indices must match */
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+ if (iph1->frag_last_index != 0 &&
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+ item->frag_last != iph1->frag_last_index) {
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+ plog(LLV_ERROR, LOCATION, NULL,
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+ "Repeated last fragment index mismatch\n");
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+ racoon_free(item);
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+ vfree(buf);
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+ return -1;
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+ }
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- if (iph1->frag_chain == NULL) {
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- iph1->frag_chain = item;
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- } else {
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- struct isakmp_frag_item *current;
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+ last_frag = iph1->frag_last_index = item->frag_num;
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+ }
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- current = iph1->frag_chain;
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- while (current->frag_next) {
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- if (current->frag_last)
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- last_frag = item->frag_num;
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- current = current->frag_next;
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- }
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- current->frag_next = item;
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+ /* insert fragment into chain */
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+ if (isakmp_frag_insert(iph1, item) == -1) {
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+ plog(LLV_ERROR, LOCATION, NULL,
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+ "Repeated fragment index mismatch\n");
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+ racoon_free(item);
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+ vfree(buf);
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+ return -1;
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}
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- /* If we saw the last frag, check if the chain is complete */
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+ /* If we saw the last frag, check if the chain is complete
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+ * we have a sorted list now, so just walk through */
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if (last_frag != 0) {
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+ item = iph1->frag_chain;
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for (i = 1; i <= last_frag; i++) {
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- item = iph1->frag_chain;
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- do {
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- if (item->frag_num == i)
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- break;
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- item = item->frag_next;
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- } while (item != NULL);
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-
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+ if (item->frag_num != i)
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+ break;
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+ item = item->frag_next;
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if (item == NULL) /* Not found */
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break;
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}
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- if (item != NULL) /* It is complete */
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+ if (i > last_frag) /* It is complete */
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return 1;
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}
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@@ -291,15 +332,9 @@ isakmp_frag_reassembly(iph1)
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}
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data = buf->v;
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+ item = iph1->frag_chain;
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for (i = 1; i <= frag_count; i++) {
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- item = iph1->frag_chain;
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- do {
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- if (item->frag_num == i)
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- break;
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- item = item->frag_next;
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- } while (item != NULL);
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-
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- if (item == NULL) {
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+ if (item->frag_num != i) {
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plog(LLV_ERROR, LOCATION, NULL,
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"Missing fragment #%d\n", i);
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vfree(buf);
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@@ -308,6 +343,7 @@ isakmp_frag_reassembly(iph1)
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}
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memcpy(data, item->frag_packet->v, item->frag_packet->l);
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data += item->frag_packet->l;
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+ item = item->frag_next;
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}
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out:
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