Require all ASN1_PRIMITIVE_FUNCS functions to be provided.

If an ASN.1 item provides its own ASN1_PRIMITIVE_FUNCS functions, require
all functions to be provided (currently excluding prim_clear). This avoids
situations such as having a custom allocator that returns a specific struct
but then is then printed using the default primative print functions, which
interpret the memory as a different struct.

Found by oss-fuzz, fixes issue #13799.

ok beck@, tb@

1 files changed, 7 insertions, 4 deletions

diff --git a/src/lib/libcrypto/asn1/tasn_enc.c b/src/lib/libcrypto/asn1/tasn_enc.c
index f3341901fe..d103c4d096 100644
--- a/src/lib/libcrypto/asn1/tasn_enc.c
+++ b/src/lib/libcrypto/asn1/tasn_enc.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: tasn_enc.c,v 1.21 2016/12/30 16:04:34 jsing Exp $ */
+/* $OpenBSD: tasn_enc.c,v 1.22 2019/04/01 15:48:04 jsing Exp $ */
 /* Written by Dr Stephen N Henson (steve@openssl.org) for the OpenSSL
  * project 2000.
  */
@@ -541,11 +541,14 @@ asn1_ex_i2c(ASN1_VALUE **pval, unsigned char *cout, int *putype,
         const unsigned char *cont;
         unsigned char c;
         int len;
-        const ASN1_PRIMITIVE_FUNCS *pf;
 
-        pf = it->funcs;
-        if (pf && pf->prim_i2c)
+        if (it->funcs != NULL) {
+                const ASN1_PRIMITIVE_FUNCS *pf = it->funcs;
+
+                if (pf->prim_i2c == NULL)
+                        return -1;
                 return pf->prim_i2c(pval, cout, putype, it);
+        }
 
         /* Should type be omitted? */
         if ((it->itype != ASN1_ITYPE_PRIMITIVE) ||