From ca196a9d6b85240361be460c4bcd731286919a54 Mon Sep 17 00:00:00 2001 From: Robbie Harwood Date: Thu, 19 Aug 2021 12:29:56 -0400 Subject: [PATCH] Fix KDC null deref on TGS inner body null server (CVE-2021-37750) --- ...-deref-on-TGS-inner-body-null-server.patch | 45 +++++++++++++++++++ krb5.spec | 6 ++- 2 files changed, 50 insertions(+), 1 deletion(-) create mode 100644 Fix-KDC-null-deref-on-TGS-inner-body-null-server.patch diff --git a/Fix-KDC-null-deref-on-TGS-inner-body-null-server.patch b/Fix-KDC-null-deref-on-TGS-inner-body-null-server.patch new file mode 100644 index 0000000..24b9d95 --- /dev/null +++ b/Fix-KDC-null-deref-on-TGS-inner-body-null-server.patch @@ -0,0 +1,45 @@ +From bb8fa495d00ccd931eec87a01b8920636cf7903e Mon Sep 17 00:00:00 2001 +From: Greg Hudson +Date: Tue, 3 Aug 2021 01:15:27 -0400 +Subject: [PATCH] Fix KDC null deref on TGS inner body null server + +After the KDC decodes a FAST inner body, it does not check for a null +server. Prior to commit 39548a5b17bbda9eeb63625a201cfd19b9de1c5b this +would typically result in an error from krb5_unparse_name(), but with +the addition of get_local_tgt() it results in a null dereference. Add +a null check. + +Reported by Joseph Sutton of Catalyst. + +CVE-2021-37750: + +In MIT krb5 releases 1.14 and later, an authenticated attacker can +cause a null dereference in the KDC by sending a FAST TGS request with +no server field. + +ticket: 9008 (new) +tags: pullup +target_version: 1.19-next +target_version: 1.18-next + +(cherry picked from commit d775c95af7606a51bf79547a94fa52ddd1cb7f49) +--- + src/kdc/do_tgs_req.c | 5 +++++ + 1 file changed, 5 insertions(+) + +diff --git a/src/kdc/do_tgs_req.c b/src/kdc/do_tgs_req.c +index 6d244ffd4..39a504ca1 100644 +--- a/src/kdc/do_tgs_req.c ++++ b/src/kdc/do_tgs_req.c +@@ -207,6 +207,11 @@ process_tgs_req(krb5_kdc_req *request, krb5_data *pkt, + status = "FIND_FAST"; + goto cleanup; + } ++ if (sprinc == NULL) { ++ status = "NULL_SERVER"; ++ errcode = KRB5KDC_ERR_S_PRINCIPAL_UNKNOWN; ++ goto cleanup; ++ } + + errcode = get_local_tgt(kdc_context, &sprinc->realm, header_server, + &local_tgt, &local_tgt_storage, &local_tgt_key); diff --git a/krb5.spec b/krb5.spec index 930a581..37c3b90 100644 --- a/krb5.spec +++ b/krb5.spec @@ -42,7 +42,7 @@ Summary: The Kerberos network authentication system Name: krb5 Version: 1.19.2 -Release: %{?zdpd}1%{?dist} +Release: %{?zdpd}2%{?dist} # rharwood has trust path to signing key and verifies on check-in Source0: https://web.mit.edu/kerberos/dist/krb5/%{version}/krb5-%{version}%{?dashpre}.tar.gz @@ -89,6 +89,7 @@ Patch24: Fix-leaks-on-error-in-kadm5-init-functions.patch Patch25: Clean-up-context-after-failed-open-in-libkdb5.patch Patch26: Use-asan-in-one-of-the-CI-builds.patch Patch29: Clean-up-gssapi_krb5-ccache-name-functions.patch +Patch30: Fix-KDC-null-deref-on-TGS-inner-body-null-server.patch License: MIT URL: https://web.mit.edu/kerberos/www/ @@ -651,6 +652,9 @@ exit 0 %{_libdir}/libkadm5srv_mit.so.* %changelog +* Thu Aug 19 2021 Robbie Harwood - 1.19.2-2 +- Fix KDC null deref on TGS inner body null server (CVE-2021-37750) + * Mon Jul 26 2021 Robbie Harwood - 1.19.2-1 - New upstream version (1.19.2)