* Mon May 4 2015 Roland Mainz <rmainz@redhat.com> - 1.13.1-4
- fix for CVE-2015-2694 (#1216133) "requires_preauth bypass in PKINIT-enabled KDC". In MIT krb5 1.12 and later, when the KDC is configured with PKINIT support, an unauthenticated remote attacker can bypass the requires_preauth flag on a client principal and obtain a ciphertext encrypted in the principal's long-term key. This ciphertext could be used to conduct an off-line dictionary attack against the user's password. resolves: #1216134
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Roland Mainz
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14a63ce373
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@ -0,0 +1,100 @@
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From e3b5a5e5267818c97750b266df50b6a3d4649604 Mon Sep 17 00:00:00 2001
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From: Greg Hudson <ghudson@mit.edu>
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Date: Tue, 24 Mar 2015 12:02:37 -0400
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Subject: [PATCH] Prevent requires_preauth bypass [CVE-2015-2694]
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In the OTP kdcpreauth module, don't set the TKT_FLG_PRE_AUTH bit until
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the request is successfully verified. In the PKINIT kdcpreauth
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module, don't respond with code 0 on empty input or an unconfigured
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realm. Together these bugs could cause the KDC preauth framework to
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erroneously treat a request as pre-authenticated.
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CVE-2015-2694:
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In MIT krb5 1.12 and later, when the KDC is configured with PKINIT
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support, an unauthenticated remote attacker can bypass the
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requires_preauth flag on a client principal and obtain a ciphertext
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encrypted in the principal's long-term key. This ciphertext could be
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used to conduct an off-line dictionary attack against the user's
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password.
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CVSSv2 Vector: AV:N/AC:M/Au:N/C:P/I:P/A:N/E:POC/RL:OF/RC:C
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ticket: 8160 (new)
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target_version: 1.13.2
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tags: pullup
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subject: requires_preauth bypass in PKINIT-enabled KDC [CVE-2015-2694]
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---
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src/plugins/preauth/otp/main.c | 10 +++++++---
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src/plugins/preauth/pkinit/pkinit_srv.c | 4 ++--
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2 files changed, 9 insertions(+), 5 deletions(-)
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diff --git a/src/plugins/preauth/otp/main.c b/src/plugins/preauth/otp/main.c
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index bf9c6a8..7941b4a 100644
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--- a/src/plugins/preauth/otp/main.c
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+++ b/src/plugins/preauth/otp/main.c
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@@ -42,6 +42,7 @@ static krb5_preauthtype otp_pa_type_list[] =
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struct request_state {
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krb5_kdcpreauth_verify_respond_fn respond;
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void *arg;
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+ krb5_enc_tkt_part *enc_tkt_reply;
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};
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static krb5_error_code
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@@ -159,6 +160,9 @@ on_response(void *data, krb5_error_code retval, otp_response response)
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if (retval == 0 && response != otp_response_success)
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retval = KRB5_PREAUTH_FAILED;
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+ if (retval == 0)
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+ rs.enc_tkt_reply->flags |= TKT_FLG_PRE_AUTH;
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+
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rs.respond(rs.arg, retval, NULL, NULL, NULL);
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}
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@@ -263,8 +267,6 @@ otp_verify(krb5_context context, krb5_data *req_pkt, krb5_kdc_req *request,
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krb5_data d, plaintext;
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char *config;
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- enc_tkt_reply->flags |= TKT_FLG_PRE_AUTH;
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-
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/* Get the FAST armor key. */
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armor_key = cb->fast_armor(context, rock);
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if (armor_key == NULL) {
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@@ -298,12 +300,14 @@ otp_verify(krb5_context context, krb5_data *req_pkt, krb5_kdc_req *request,
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goto error;
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}
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- /* Create the request state. */
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+ /* Create the request state. Save the response callback, and the
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+ * enc_tkt_reply pointer so we can set the TKT_FLG_PRE_AUTH flag later. */
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rs = k5alloc(sizeof(struct request_state), &retval);
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if (rs == NULL)
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goto error;
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rs->arg = arg;
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rs->respond = respond;
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+ rs->enc_tkt_reply = enc_tkt_reply;
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/* Get the principal's OTP configuration string. */
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retval = cb->get_string(context, rock, "otp", &config);
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diff --git a/src/plugins/preauth/pkinit/pkinit_srv.c b/src/plugins/preauth/pkinit/pkinit_srv.c
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index b472741..5b1d73e 100644
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--- a/src/plugins/preauth/pkinit/pkinit_srv.c
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+++ b/src/plugins/preauth/pkinit/pkinit_srv.c
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@@ -301,7 +301,7 @@ pkinit_server_verify_padata(krb5_context context,
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pkiDebug("pkinit_verify_padata: entered!\n");
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if (data == NULL || data->length <= 0 || data->contents == NULL) {
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- (*respond)(arg, 0, NULL, NULL, NULL);
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+ (*respond)(arg, EINVAL, NULL, NULL, NULL);
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return;
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}
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@@ -313,7 +313,7 @@ pkinit_server_verify_padata(krb5_context context,
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plgctx = pkinit_find_realm_context(context, moddata, request->server);
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if (plgctx == NULL) {
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- (*respond)(arg, 0, NULL, NULL, NULL);
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+ (*respond)(arg, EINVAL, NULL, NULL, NULL);
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return;
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}
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14
krb5.spec
14
krb5.spec
@ -43,7 +43,7 @@
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Summary: The Kerberos network authentication system
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Name: krb5
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Version: 1.13.1
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Release: 3%{?dist}
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Release: 4%{?dist}
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# - Maybe we should explode from the now-available-to-everybody tarball instead?
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# http://web.mit.edu/kerberos/dist/krb5/1.13/krb5-1.13.1-signed.tar
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# - The sources below are stored in a lookaside cache. Upload with
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@ -96,6 +96,7 @@ Patch134: krb5-1.11-kpasswdtest.patch
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Patch136: krb5-socket_wrapper_eventfd_prototype_mismatch.patch
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Patch140: krb5-1.14-Support-KDC_ERR_MORE_PREAUTH_DATA_REQUIRED.patch
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Patch141: krb5-1.12.1-CVE_2014_5355_fix_krb5_read_message_handling.patch
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Patch142: krb5-1.13.2-CVE_2015_2694_requires_preauth_bypass_in_PKINIT_enabled_KDC.patch
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License: MIT
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URL: http://web.mit.edu/kerberos/www/
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@ -319,6 +320,7 @@ ln NOTICE LICENSE
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%patch140 -p1 -b .krb5-1.14-support-kdc_err_more_preauth_data_required
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%patch141 -p1 -b .krb5-1.12.1-cve_2014_5355_fix_krb5_read_message_handling
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%patch142 -p1 -b .krb5-1.13.2-cve_2015_2694_requires_preauth_bypass_in_pkinit_enabled_kdc
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# Take the execute bit off of documentation.
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chmod -x doc/krb5-protocol/*.txt doc/ccapi/*.html
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@ -1002,6 +1004,16 @@ exit 0
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%changelog
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* Mon May 4 2015 Roland Mainz <rmainz@redhat.com> - 1.13.1-4
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- fix for CVE-2015-2694 (#1216133) "requires_preauth bypass
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in PKINIT-enabled KDC".
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In MIT krb5 1.12 and later, when the KDC is configured with
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PKINIT support, an unauthenticated remote attacker can
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bypass the requires_preauth flag on a client principal and
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obtain a ciphertext encrypted in the principal's long-term
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key. This ciphertext could be used to conduct an off-line
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dictionary attack against the user's password.
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* Wed Mar 25 2015 Roland Mainz <rmainz@redhat.com> - 1.13.1-3
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- Add temporay workaround for RH bug #1204646 ("krb5-config
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returns wrong -specs path") which modifies krb5-config post
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