Fix integer overflows in PAC parsing (CVE-2022-42898)

Resolves: rhbz#2143011
Signed-off-by: Julien Rische <jrische@redhat.com>

Fix-integer-overflows-in-PAC-parsing.patch

@@ -0,0 +1,106 @@
+From 06d30f43a41029d83248bbac1a9b65fc09987597 Mon Sep 17 00:00:00 2001
+From: Greg Hudson <ghudson@mit.edu>
+Date: Mon, 17 Oct 2022 20:25:11 -0400
+Subject: [PATCH] Fix integer overflows in PAC parsing
+
+In krb5_parse_pac(), check for buffer counts large enough to threaten
+integer overflow in the header length and memory length calculations.
+Avoid potential integer overflows when checking the length of each
+buffer.
+
+CVE-2022-42898:
+
+In MIT krb5 releases 1.8 and later, an authenticated attacker may be
+able to cause a KDC or kadmind process to crash by reading beyond the
+bounds of allocated memory, creating a denial of service.  A
+privileged attacker may similarly be able to cause a Kerberos or GSS
+application service to crash.  On 32-bit platforms, an attacker can
+also cause insufficient memory to be allocated for the result,
+potentially leading to remote code execution in a KDC, kadmind, or GSS
+or Kerberos application server process.  An attacker with the
+privileges of a cross-realm KDC may be able to extract secrets from
+the KDC process's memory by having them copied into the PAC of a new
+ticket.
+
+ticket: 9074 (new)
+tags: pullup
+target_version: 1.20-next
+target_version: 1.19-next
+---
+ src/lib/krb5/krb/pac.c   |  9 +++++++--
+ src/lib/krb5/krb/t_pac.c | 18 ++++++++++++++++++
+ 2 files changed, 25 insertions(+), 2 deletions(-)
+
+diff --git a/src/lib/krb5/krb/pac.c b/src/lib/krb5/krb/pac.c
+index 950beda657..1b9ef12276 100644
+--- a/src/lib/krb5/krb/pac.c
++++ b/src/lib/krb5/krb/pac.c
+@@ -27,6 +27,8 @@
+ #include "k5-int.h"
+ #include "authdata.h"
+ 
++#define MAX_BUFFERS 4096
++
+ /* draft-brezak-win2k-krb-authz-00 */
+ 
+ /*
+@@ -316,6 +318,9 @@ krb5_pac_parse(krb5_context context,
+     if (version != 0)
+         return EINVAL;
+ 
++    if (cbuffers < 1 || cbuffers > MAX_BUFFERS)
++        return ERANGE;
++
+     header_len = PACTYPE_LENGTH + (cbuffers * PAC_INFO_BUFFER_LENGTH);
+     if (len < header_len)
+         return ERANGE;
+@@ -348,8 +353,8 @@ krb5_pac_parse(krb5_context context,
+             krb5_pac_free(context, pac);
+             return EINVAL;
+         }
+-        if (buffer->Offset < header_len ||
+-            buffer->Offset + buffer->cbBufferSize > len) {
++        if (buffer->Offset < header_len || buffer->Offset > len ||
++            buffer->cbBufferSize > len - buffer->Offset) {
+             krb5_pac_free(context, pac);
+             return ERANGE;
+         }
+diff --git a/src/lib/krb5/krb/t_pac.c b/src/lib/krb5/krb/t_pac.c
+index ee47152ee4..ccd165380d 100644
+--- a/src/lib/krb5/krb/t_pac.c
++++ b/src/lib/krb5/krb/t_pac.c
+@@ -431,6 +431,16 @@ static const unsigned char s4u_pac_ent_xrealm[] = {
+     0x8a, 0x81, 0x9c, 0x9c, 0x00, 0x00, 0x00, 0x00
+ };
+ 
++static const unsigned char fuzz1[] = {
++    0x00, 0x00, 0x00, 0x10, 0x00, 0x00, 0x00, 0x00,
++    0x06, 0xff, 0xff, 0xff, 0x00, 0x00, 0xf5
++};
++
++static const unsigned char fuzz2[] = {
++    0x00, 0x00, 0x00, 0x20, 0x00, 0x00, 0x00, 0x00,
++    0x20, 0x20
++};
++
+ static const char *s4u_principal = "w2k8u@ACME.COM";
+ static const char *s4u_enterprise = "w2k8u@abc@ACME.COM";
+ 
+@@ -646,6 +656,14 @@ main(int argc, char **argv)
+         krb5_free_principal(context, sep);
+     }
+ 
++    /* Check problematic PACs found by fuzzing. */
++    ret = krb5_pac_parse(context, fuzz1, sizeof(fuzz1), &pac);
++    if (!ret)
++        err(context, ret, "krb5_pac_parse should have failed");
++    ret = krb5_pac_parse(context, fuzz2, sizeof(fuzz2), &pac);
++    if (!ret)
++        err(context, ret, "krb5_pac_parse should have failed");
++
+     /*
+      * Test empty free
+      */
+-- 
+2.37.3
+

krb5.spec

@@ -34,7 +34,7 @@
 #
 # baserelease is what we have standardized across Fedora and what
 # rpmdev-bumpspec knows how to handle.
-%global baserelease 12
+%global baserelease 13
 
 # This should be e.g. beta1 or %%nil
 %global pre_release %nil
@@ -120,6 +120,7 @@ Patch40: Try-harder-to-avoid-password-change-replay-errors.patch
 Patch41: Add-configure-variable-for-default-PKCS-11-module.patch
 Patch42: downstream-Allow-krad-UDP-TCP-localhost-connection-with-FIPS.patch
 Patch43: Read-GSS-configuration-files-with-mtime-0.patch
+Patch44: Fix-integer-overflows-in-PAC-parsing.patch
 
 License: MIT
 URL: https://web.mit.edu/kerberos/www/
@@ -675,6 +676,10 @@ exit 0
 %{_libdir}/libkadm5srv_mit.so.*
 
 %changelog
+* Wed Nov 09 2022 Julien Rische <jrische@redhat.com> - 1.19.2-13
+- Fix integer overflows in PAC parsing (CVE-2022-42898)
+- Resolves: rhbz#2143011
+
 * Tue Aug 02 2022 Andreas Schneider <asn@redhat.com> - 1.19.2-12
 - Use baserelease to set the release number
 - Do not define netlib, but use autoconf detection for res_* functions