Refactor asn1_ex_c2i()

The asn1_ex_c2i() function currently handles the V_ASN1_ANY case inline,
which means there multiple special cases, with  pointer fudging and
restoring. Instead, split asn1_ex_c2i() into three functions - one that
only handles storage into a primitive type (asn1_ex_c2i_primitive()), one
that handles the V_ASN1_ANY case (asn1_ex_c2i_any()) and calls
asn1_ex_c2i_primitive() with the correct pointer and an asn1_ex_c2i()
that handles the custom functions case, before dispatching to
asn1_ex_c2i_any() or asn1_ex_c2i_primitive(), as appropriate.

This results in cleaner and simpler code.

With input from and ok tb@

1 files changed, 59 insertions, 39 deletions

diff --git a/src/lib/libcrypto/asn1/tasn_dec.c b/src/lib/libcrypto/asn1/tasn_dec.c
index 103774fc19..f04ec66bc7 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 1.58 2022/05/05 19:18:56 jsing Exp $ */
+/* $OpenBSD: tasn_dec.c,v 1.59 2022/05/07 10:03:49 jsing Exp $ */
 /* Written by Dr Stephen N Henson (steve@openssl.org) for the OpenSSL
  * project 2000.
  */
@@ -771,47 +771,21 @@ asn1_d2i_ex_primitive(ASN1_VALUE **pval, const unsigned char **in, long inlen,
         return ret;
 }
 
-/* Translate ASN.1 content octets into a structure. */
 static int
-asn1_ex_c2i(ASN1_VALUE **pval, CBS *content, int utype, const ASN1_ITEM *it)
+asn1_ex_c2i_primitive(ASN1_VALUE **pval, CBS *content, int utype, const ASN1_ITEM *it)
 {
-        ASN1_VALUE **opval = NULL;
         ASN1_STRING *stmp;
-        ASN1_TYPE *typ = NULL;
         ASN1_INTEGER **tint;
         ASN1_BOOLEAN *tbool;
         uint8_t u8val;
         int ret = 0;
 
-        if (CBS_len(content) > INT_MAX)
+        if (it->funcs != NULL)
                 return 0;
 
-        if (it->funcs != NULL) {
-                const ASN1_PRIMITIVE_FUNCS *pf = it->funcs;
-                char free_content = 0;
-
-                if (pf->prim_c2i == NULL)
-                        return 0;
-
-                return pf->prim_c2i(pval, CBS_data(content), CBS_len(content),
-                    utype, &free_content, it);
-        }
+        if (CBS_len(content) > INT_MAX)
+                return 0;
 
-        /* If ANY type clear type and set pointer to internal value */
-        if (it->utype == V_ASN1_ANY) {
-                if (!*pval) {
-                        typ = ASN1_TYPE_new();
-                        if (typ == NULL)
-                                goto err;
-                        *pval = (ASN1_VALUE *)typ;
-                } else
-                        typ = (ASN1_TYPE *)*pval;
-
-                if (utype != typ->type)
-                        ASN1_TYPE_set(typ, utype, NULL);
-                opval = pval;
-                pval = &typ->value.asn1_value;
-        }
         switch (utype) {
         case V_ASN1_OBJECT:
                 if (!c2i_ASN1_OBJECT_cbs((ASN1_OBJECT **)pval, content))
@@ -895,21 +869,67 @@ asn1_ex_c2i(ASN1_VALUE **pval, CBS *content, int utype, const ASN1_ITEM *it)
                 }
                 break;
         }
-        /* If ASN1_ANY and NULL type fix up value */
-        if (typ && (utype == V_ASN1_NULL))
-                typ->value.ptr = NULL;
 
         ret = 1;
 
  err:
-        if (!ret) {
-                ASN1_TYPE_free(typ);
-                if (opval)
-                        *opval = NULL;
-        }
         return ret;
 }
 
+static int
+asn1_ex_c2i_any(ASN1_VALUE **pval, CBS *content, int utype, const ASN1_ITEM *it)
+{
+        ASN1_TYPE *atype;
+
+        if (it->utype != V_ASN1_ANY || it->funcs != NULL)
+                return 0;
+
+        if (*pval != NULL) {
+                ASN1_TYPE_free((ASN1_TYPE *)*pval);
+                *pval = NULL;
+        }
+
+        if ((atype = ASN1_TYPE_new()) == NULL)
+                return 0;
+
+        if (!asn1_ex_c2i_primitive(&atype->value.asn1_value, content, utype, it)) {
+                ASN1_TYPE_free(atype);
+                return 0;
+        }
+        atype->type = utype;
+
+        /* Fix up value for ASN.1 NULL. */
+        if (atype->type == V_ASN1_NULL)
+                atype->value.ptr = NULL;
+
+        *pval = (ASN1_VALUE *)atype;
+
+        return 1;
+}
+
+static int
+asn1_ex_c2i(ASN1_VALUE **pval, CBS *content, int utype, const ASN1_ITEM *it)
+{
+        if (CBS_len(content) > INT_MAX)
+                return 0;
+
+        if (it->funcs != NULL) {
+                const ASN1_PRIMITIVE_FUNCS *pf = it->funcs;
+                char free_content = 0;
+
+                if (pf->prim_c2i == NULL)
+                        return 0;
+
+                return pf->prim_c2i(pval, CBS_data(content), CBS_len(content),
+                    utype, &free_content, it);
+        }
+
+        if (it->utype == V_ASN1_ANY)
+                return asn1_ex_c2i_any(pval, content, utype, it);
+
+        return asn1_ex_c2i_primitive(pval, content, utype, it);
+}
+
 /* Find the end of an ASN.1 object. */
 static int
 asn1_find_end(CBS *cbs, size_t length, char indefinite)