Fix a NULL dereference in GENERAL_NAME_cmp()libressl-v3.2.3

Comparing two GENERAL_NAME structures containing an EDIPARTYNAME can lead
to a crash. This enables a denial of service attack for an attacker who can
control both sides of the comparison.

Issue reported to OpenSSL on Nov 9 by David Benjamin.
OpenSSL shared the information with us on Dec 1st.
Fix from Matt Caswell (OpenSSL) with a few small tweaks.

ok jsing

this is errata/6.8/008_asn1.patch.sig

1 files changed, 21 insertions, 1 deletions

diff --git a/src/lib/libcrypto/asn1/tasn_dec.c b/src/lib/libcrypto/asn1/tasn_dec.c
index 70dc355ca1..ff1ed43ca9 100644
--- a/src/lib/libcrypto/asn1/tasn_dec.c
+++ b/src/lib/libcrypto/asn1/tasn_dec.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: tasn_dec.c,v 1.37 2019/04/01 15:48:04 jsing Exp $ */
+/* $OpenBSD: tasn_dec.c,v 1.37.10.1 2020/12/08 15:08:47 tb Exp $ */
 /* Written by Dr Stephen N Henson (steve@openssl.org) for the OpenSSL
  * project 2000.
  */
@@ -210,6 +210,16 @@ asn1_item_ex_d2i(ASN1_VALUE **pval, const unsigned char **in, long len,
                 break;
 
         case ASN1_ITYPE_MSTRING:
+                /*
+                 * It never makes sense for multi-strings to have implicit
+                 * tagging, so if tag != -1, then this looks like an error in
+                 * the template.
+                 */
+                if (tag != -1) {
+                        ASN1error(ASN1_R_BAD_TEMPLATE);
+                        goto err;
+                }
+
                 p = *in;
                 /* Just read in tag and class */
                 ret = asn1_check_tlen(NULL, &otag, &oclass, NULL, NULL,
@@ -245,6 +255,16 @@ asn1_item_ex_d2i(ASN1_VALUE **pval, const unsigned char **in, long len,
                     it, tag, aclass, opt, ctx);
 
         case ASN1_ITYPE_CHOICE:
+                /*
+                 * It never makes sense for CHOICE types to have implicit
+                 * tagging, so if tag != -1, then this looks like an error in
+                 * the template.
+                 */
+                if (tag != -1) {
+                        ASN1error(ASN1_R_BAD_TEMPLATE);
+                        goto err;
+                }
+
                 if (asn1_cb && !asn1_cb(ASN1_OP_D2I_PRE, pval, it, NULL))
                         goto auxerr;