From 13a2dca744e9b37549b68fcd3f1d44e2fe1e8425 Mon Sep 17 00:00:00 2001
From: Nicolas Williams <nico@twosigma.com>
Date: Wed, 10 Mar 2021 16:49:04 -0600
Subject: [PATCH 2/2] CVE-2022-44640 HEIMDAL: asn1: invalid free in ASN.1 codec

Heimdal's ASN.1 compiler generates code that allows specially
crafted DER encodings of CHOICEs to invoke the wrong free function
on the decoded structure upon decode error.  This is known to impact
the Heimdal KDC, leading to an invalid free() of an address partly
or wholly under the control of the attacker, in turn leading to a
potential remote code execution (RCE) vulnerability.

This error affects the DER codec for all CHOICE types used in
Heimdal, though not all cases will be exploitable.  We have not
completed a thorough analysis of all the Heimdal components
affected, thus the Kerberos client, the X.509 library, and other
parts, may be affected as well.

This bug has been in Heimdal since 2005.  It was first reported by
Douglas Bagnall, though it had been found independently by the
Heimdal maintainers via fuzzing a few weeks earlier.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=14929

(cherry-picked from Heimdal commit 9c9dac2b169255bad9071eea99fa90b980dde767)

Signed-off-by: Andrew Bartlett <abartlet@samba.org>
Reviewed-by: Stefan Metzmacher <metze@samba.org>

Autobuild-User(master): Stefan Metzmacher <metze@samba.org>
Autobuild-Date(master): Tue Dec  6 13:41:05 UTC 2022 on sn-devel-184

(cherry picked from commit 68fc909a7f4d69c254d34bec85cf8431bcb6e72f)

Conflict： remove third_party/heimdal/lib/asn1/krb5.asn1 and .../heimdal/lib/asn1/fuzz-inputs/KrbFastArmoredReq
Reference: https://attachments.samba.org/attachment.cgi?id=17675
---
 third_party/heimdal/lib/asn1/gen_decode.c          |  12 ++++++------
 third_party/heimdal/lib/asn1/gen_free.c            |   7 +++++++
 third_party/heimdal/lib/asn1/gen_template.c        |   1 +
 5 files changed, 15 insertions(+), 6 deletions(-)

diff --git a/third_party/heimdal/lib/asn1/gen_decode.c b/third_party/heimdal/lib/asn1/gen_decode.c
index 93d412f63356..fa9d79a8ae5b 100644
--- a/third_party/heimdal/lib/asn1/gen_decode.c
+++ b/third_party/heimdal/lib/asn1/gen_decode.c
@@ -694,14 +694,14 @@ decode_type(const char *name, const Type *t, int optional, struct value *defval,
 		    classname(cl),
 		    ty ? "CONS" : "PRIM",
 		    valuename(cl, tag));
+	    fprintf(codefile,
+		    "(%s)->element = %s;\n",
+		    name, m->label);
 	    if (asprintf (&s, "%s(%s)->u.%s", m->optional ? "" : "&",
 			  name, m->gen_name) < 0 || s == NULL)
 		errx(1, "malloc");
             decode_type(s, m->type, m->optional, NULL, forwstr, m->gen_name,
                         NULL, depth + 1);
-	    fprintf(codefile,
-		    "(%s)->element = %s;\n",
-		    name, m->label);
 	    free(s);
 	    fprintf(codefile,
 		    "}\n");
@@ -710,23 +710,23 @@ decode_type(const char *name, const Type *t, int optional, struct value *defval,
 	if (have_ellipsis) {
 	    fprintf(codefile,
 		    "else {\n"
+		    "(%s)->element = %s;\n"
 		    "(%s)->u.%s.data = calloc(1, len);\n"
 		    "if ((%s)->u.%s.data == NULL) {\n"
 		    "e = ENOMEM; %s;\n"
 		    "}\n"
 		    "(%s)->u.%s.length = len;\n"
 		    "memcpy((%s)->u.%s.data, p, len);\n"
-		    "(%s)->element = %s;\n"
 		    "p += len;\n"
 		    "ret += len;\n"
 		    "len = 0;\n"
 		    "}\n",
+		    name, have_ellipsis->label,
 		    name, have_ellipsis->gen_name,
 		    name, have_ellipsis->gen_name,
 		    forwstr,
 		    name, have_ellipsis->gen_name,
-		    name, have_ellipsis->gen_name,
-		    name, have_ellipsis->label);
+		    name, have_ellipsis->gen_name);
 	} else {
 	    fprintf(codefile,
 		    "else {\n"
diff --git a/third_party/heimdal/lib/asn1/gen_free.c b/third_party/heimdal/lib/asn1/gen_free.c
index 0507d5421803..b6da8ae14dd2 100644
--- a/third_party/heimdal/lib/asn1/gen_free.c
+++ b/third_party/heimdal/lib/asn1/gen_free.c
@@ -62,6 +62,13 @@ free_type (const char *name, const Type *t, int preserve)
     case TNull:
     case TGeneralizedTime:
     case TUTCTime:
+        /*
+         * This doesn't do much, but it leaves zeros where garbage might
+         * otherwise have been found.  Gets us closer to having the equivalent
+         * of a memset()-to-zero data structure after calling the free
+         * functions.
+         */
+        fprintf(codefile, "*%s = 0;\n", name);
 	break;
     case TBitString:
 	if (HEIM_TAILQ_EMPTY(t->members))
diff --git a/third_party/heimdal/lib/asn1/gen_template.c b/third_party/heimdal/lib/asn1/gen_template.c
index e053a8bdd8bc..ad25fcfb29d3 100644
--- a/third_party/heimdal/lib/asn1/gen_template.c
+++ b/third_party/heimdal/lib/asn1/gen_template.c
@@ -1600,6 +1600,7 @@ generate_template(const Symbol *s)
 	    "int ASN1CALL\n"
 	    "decode_%s(const unsigned char *p, size_t len, %s *data, size_t *size)\n"
 	    "{\n"
+            "    memset(data, 0, sizeof(*data));\n"
 	    "    return _asn1_decode_top(asn1_%s, 0|%s, p, len, data, size);\n"
 	    "}\n"
 	    "\n",
-- 
2.34.1
