49 lines
1.7 KiB
Diff
49 lines
1.7 KiB
Diff
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From 137e424f7ae7c054e1dcb41c929a961bb021ed8b Mon Sep 17 00:00:00 2001
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From: Andreas Schneider <asn@samba.org>
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Date: Fri, 4 Aug 2023 09:54:06 +0200
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Subject: [PATCH] Fix double-free in KDC TGS processing
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When issuing a ticket for a TGS renew or validate request, copy only
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the server field from the outer part of the header ticket to the new
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ticket. Copying the whole structure causes the enc_part pointer to be
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aliased to the header ticket until krb5_encrypt_tkt_part() is called,
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resulting in a double-free if handle_authdata() fails.
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[ghudson@mit.edu: changed the fix to avoid aliasing enc_part rather
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than check for aliasing before freeing; rewrote commit message]
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CVE-2023-39975:
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In MIT krb5 release 1.21, an authenticated attacker can cause a KDC to
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free the same pointer twice if it can induce a failure in
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authorization data handling.
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ticket: 9101 (new)
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tags: pullup
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target_version: 1.21-next
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(cherry picked from commit 88a1701b423c13991a8064feeb26952d3641d840)
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---
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src/kdc/do_tgs_req.c | 5 +++--
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1 file changed, 3 insertions(+), 2 deletions(-)
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diff --git a/src/kdc/do_tgs_req.c b/src/kdc/do_tgs_req.c
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index 6e4c8fa9f3..0acc45850f 100644
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--- a/src/kdc/do_tgs_req.c
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+++ b/src/kdc/do_tgs_req.c
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@@ -1010,8 +1010,9 @@ tgs_issue_ticket(kdc_realm_t *realm, struct tgs_req_info *t,
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}
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if (t->req->kdc_options & (KDC_OPT_VALIDATE | KDC_OPT_RENEW)) {
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- /* Copy the whole header ticket except for authorization data. */
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- ticket_reply = *t->header_tkt;
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+ /* Copy the header ticket server and all enc-part fields except for
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+ * authorization data. */
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+ ticket_reply.server = t->header_tkt->server;
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enc_tkt_reply = *t->header_tkt->enc_part2;
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enc_tkt_reply.authorization_data = NULL;
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} else {
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--
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2.41.0
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