Fix CVE-2017-11368 (remote triggerable assertion failure)

Prevent-KDC-unset-status-assertion-failures.patch

@@ -0,0 +1,109 @@
+From af6570ad6c306fe8e2bf425810236dd8c6271885 Mon Sep 17 00:00:00 2001
+From: Greg Hudson <ghudson@mit.edu>
+Date: Thu, 13 Jul 2017 12:14:20 -0400
+Subject: [PATCH] Prevent KDC unset status assertion failures
+
+Assign status values if S4U2Self padata fails to decode, if an
+S4U2Proxy request uses invalid KDC options, or if an S4U2Proxy request
+uses an evidence ticket which does not match the canonicalized request
+server principal name.  Reported by Samuel Cabrero.
+
+If a status value is not assigned during KDC processing, default to
+"UNKNOWN_REASON" rather than failing an assertion.  This change will
+prevent future denial of service bugs due to similar mistakes, and
+will allow us to omit assigning status values for unlikely errors such
+as small memory allocation failures.
+
+CVE-2017-11368:
+
+In MIT krb5 1.7 and later, an authenticated attacker can cause an
+assertion failure in krb5kdc by sending an invalid S4U2Self or
+S4U2Proxy request.
+
+  CVSSv3 Vector: AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H/E:H/RL:O/RC:C
+
+ticket: 8599 (new)
+target_version: 1.15-next
+target_version: 1.14-next
+tags: pullup
+
+(cherry picked from commit a860385dd8fbd239fdb31b347e07f4e6b2fbdcc2)
+---
+ src/kdc/do_as_req.c  |  4 ++--
+ src/kdc/do_tgs_req.c |  3 ++-
+ src/kdc/kdc_util.c   | 10 ++++++++--
+ 3 files changed, 12 insertions(+), 5 deletions(-)
+
+diff --git a/src/kdc/do_as_req.c b/src/kdc/do_as_req.c
+index 712ccb794..a4bf91b1b 100644
+--- a/src/kdc/do_as_req.c
++++ b/src/kdc/do_as_req.c
+@@ -365,8 +365,8 @@ finish_process_as_req(struct as_req_state *state, krb5_error_code errcode)
+     did_log = 1;
+ 
+ egress:
+-    if (errcode != 0)
+-        assert (state->status != 0);
++    if (errcode != 0 && state->status == NULL)
++        state->status = "UNKNOWN_REASON";
+ 
+     au_state->status = state->status;
+     au_state->reply = &state->reply;
+diff --git a/src/kdc/do_tgs_req.c b/src/kdc/do_tgs_req.c
+index 547a41441..339259fd1 100644
+--- a/src/kdc/do_tgs_req.c
++++ b/src/kdc/do_tgs_req.c
+@@ -823,7 +823,8 @@ process_tgs_req(struct server_handle *handle, krb5_data *pkt,
+     free(reply.enc_part.ciphertext.data);
+ 
+ cleanup:
+-    assert(status != NULL);
++    if (status == NULL)
++        status = "UNKNOWN_REASON";
+     if (reply_key)
+         krb5_free_keyblock(kdc_context, reply_key);
+     if (errcode)
+diff --git a/src/kdc/kdc_util.c b/src/kdc/kdc_util.c
+index 29f9dbbf0..30c501c67 100644
+--- a/src/kdc/kdc_util.c
++++ b/src/kdc/kdc_util.c
+@@ -1220,8 +1220,10 @@ kdc_process_for_user(kdc_realm_t *kdc_active_realm,
+     req_data.data = (char *)pa_data->contents;
+ 
+     code = decode_krb5_pa_for_user(&req_data, &for_user);
+-    if (code)
++    if (code) {
++        *status = "DECODE_PA_FOR_USER";
+         return code;
++    }
+ 
+     code = verify_for_user_checksum(kdc_context, tgs_session, for_user);
+     if (code) {
+@@ -1320,8 +1322,10 @@ kdc_process_s4u_x509_user(krb5_context context,
+     req_data.data = (char *)pa_data->contents;
+ 
+     code = decode_krb5_pa_s4u_x509_user(&req_data, s4u_x509_user);
+-    if (code)
++    if (code) {
++        *status = "DECODE_PA_S4U_X509_USER";
+         return code;
++    }
+ 
+     code = verify_s4u_x509_user_checksum(context,
+                                          tgs_subkey ? tgs_subkey :
+@@ -1624,6 +1628,7 @@ kdc_process_s4u2proxy_req(kdc_realm_t *kdc_active_realm,
+      * that is validated previously in validate_tgs_request().
+      */
+     if (request->kdc_options & (NON_TGT_OPTION | KDC_OPT_ENC_TKT_IN_SKEY)) {
++        *status = "INVALID_S4U2PROXY_OPTIONS";
+         return KRB5KDC_ERR_BADOPTION;
+     }
+ 
+@@ -1631,6 +1636,7 @@ kdc_process_s4u2proxy_req(kdc_realm_t *kdc_active_realm,
+     if (!krb5_principal_compare(kdc_context,
+                                 server->princ, /* after canon */
+                                 server_princ)) {
++        *status = "EVIDENCE_TICKET_MISMATCH";
+         return KRB5KDC_ERR_SERVER_NOMATCH;
+     }
+ 

krb5.spec

@@ -18,7 +18,7 @@ Summary: The Kerberos network authentication system
 Name: krb5
 Version: 1.15.1
 # for prerelease, should be e.g., 0.3.beta2%{?dist}
-Release: 16%{?dist}
+Release: 17%{?dist}
 # - Maybe we should explode from the now-available-to-everybody tarball instead?
 # http://web.mit.edu/kerberos/dist/krb5/1.13/krb5-1.13.2-signed.tar
 # - The sources below are stored in a lookaside cache. Upload with
@@ -79,6 +79,7 @@ Patch50: Correct-error-handling-bug-in-prior-commit.patch
 Patch51: Add-k5test-expected_msg-expected_trace.patch
 Patch52: Fix-leaks-in-gss_inquire_cred_by_oid.patch
 Patch53: Add-support-to-query-the-SSF-of-a-GSS-context.patch
+Patch54: Prevent-KDC-unset-status-assertion-failures.patch
 
 License: MIT
 URL: http://web.mit.edu/kerberos/www/
@@ -741,6 +742,9 @@ exit 0
 %{_libdir}/libkadm5srv_mit.so.*
 
 %changelog
+* Thu Jul 20 2017 Robbie Harwood <rharwood@redhat.com> - 1.15.1-17
+- Fix CVE-2017-11368 (remote triggerable assertion failure)
+
 * Wed Jul 19 2017 Robbie Harwood <rharwood@redhat.com> - 1.15.1-16
 - Explicitly require python2 packages