Extend `der_flexi_sequence_cmp()`

To be able to do a bit more, add an optional handler callback function.
Additional to that, also make it possible to mark elements as optional.

Signed-off-by: Steffen Jaeckel <[email protected]>

src/headers/tomcrypt_private.h

@@ -651,17 +651,29 @@ int der_printable_value_decode(int v);
 
 unsigned long der_utf8_charsize(const wchar_t c);
 
-typedef struct {
+typedef int (*der_flexi_handler)(const ltc_asn1_list*, void*);
+
+typedef struct der_flexi_check {
    ltc_asn1_type t;
+   int optional;
    ltc_asn1_list **pp;
+   der_flexi_handler handler;
+   void *userdata;
 } der_flexi_check;
 
-#define LTC_SET_DER_FLEXI_CHECK(list, index, Type, P)    \
-   do {                                         \
-      int LTC_SDFC_temp##__LINE__ = (index);   \
-      list[LTC_SDFC_temp##__LINE__].t = Type;  \
-      list[LTC_SDFC_temp##__LINE__].pp = P;    \
+#define LTC_PRIV_SET_DER_FLEXI_CHECK(list, index, Type, P, Opt, Hndl, Udata)    \
+   do {                                                                 \
+      int LTC_SDFC_temp##__LINE__ = (index);                            \
+      list[LTC_SDFC_temp##__LINE__].t = Type;                           \
+      list[LTC_SDFC_temp##__LINE__].pp = P;                             \
+      list[LTC_SDFC_temp##__LINE__].optional = Opt;                     \
+      list[LTC_SDFC_temp##__LINE__].handler = (der_flexi_handler)Hndl;  \
+      list[LTC_SDFC_temp##__LINE__].userdata = Udata;                   \
    } while (0)
+#define LTC_SET_DER_FLEXI_CHECK(list, index, Type, P) LTC_PRIV_SET_DER_FLEXI_CHECK(list, index, Type, P, 0, NULL, NULL)
+#define LTC_SET_DER_FLEXI_CHECK_OPT(list, index, Type, P) LTC_PRIV_SET_DER_FLEXI_CHECK(list, index, Type, P, 1, NULL, NULL)
+#define LTC_SET_DER_FLEXI_HANDLER(list, index, Type, Hndl, Udata) LTC_PRIV_SET_DER_FLEXI_CHECK(list, index, Type, NULL, 0, Hndl, Udata)
+#define LTC_SET_DER_FLEXI_HANDLER_OPT(list, index, Type, Hndl, Udata) LTC_PRIV_SET_DER_FLEXI_CHECK(list, index, Type, NULL, 1, Hndl, Udata)
 
 
 extern const ltc_asn1_type  der_asn1_tag_to_type_map[];

src/pk/asn1/der/sequence/der_flexi_sequence_cmp.c

@@ -24,11 +24,20 @@ int der_flexi_sequence_cmp(const ltc_asn1_list *flexi, der_flexi_check *check)
       return CRYPT_INVALID_PACKET;
    }
    cur = flexi->child;
-   while(check->t != LTC_ASN1_EOL) {
+   while(check->t != LTC_ASN1_EOL && cur) {
       if (!LTC_ASN1_IS_TYPE(cur, check->t)) {
+         if (check->optional) {
+            check++;
+            continue;
+         }
          return CRYPT_INVALID_PACKET;
       }
       if (check->pp != NULL) *check->pp = cur;
+      else if (check->handler) {
+         int err = check->handler(cur, check->userdata);
+         if (err != CRYPT_OK)
+            return err;
+      }
       cur = cur->next;
       check++;
    }