use DECR_LEN() in _asn1_extract_tag_der()

diff --git a/lib/decoding.c b/lib/decoding.c
index 3de6d6d..bfc9dac 100644 (file)
--- a/lib/decoding.c
+++ b/lib/decoding.c
@@ -401,6 +401,7 @@ _asn1_extract_tag_der (asn1_node node, const unsigned char *der, int der_len,
 {
   asn1_node p;
   int counter, len2, len3, is_tag_implicit;
+  int result;
   unsigned long tag, tag_implicit = 0;
   unsigned char class, class2, class_implicit = 0;
 
@@ -428,23 +429,21 @@ _asn1_extract_tag_der (asn1_node node, const unsigned char *der, int der_len,
              if (p->type & CONST_EXPLICIT)
                {
                  if (asn1_get_tag_der
-                     (der + counter, der_len - counter, &class, &len2,
+                     (der + counter, der_len, &class, &len2,
                       &tag) != ASN1_SUCCESS)
                    return ASN1_DER_ERROR;
 
-                 if (counter + len2 > der_len)
-                   return ASN1_DER_ERROR;
+                  DECR_LEN(der_len, len2);
                  counter += len2;
 
                  len3 =
-                   asn1_get_length_ber (der + counter, der_len - counter,
+                   asn1_get_length_ber (der + counter, der_len,
                                         &len2);
                  if (len3 < 0)
                    return ASN1_DER_ERROR;
 
+                  DECR_LEN(der_len, len2);
                  counter += len2;
-                 if (counter > der_len)
-                   return ASN1_DER_ERROR;
 
                  if (!is_tag_implicit)
                    {
@@ -481,11 +480,11 @@ _asn1_extract_tag_der (asn1_node node, const unsigned char *der, int der_len,
   if (is_tag_implicit)
     {
       if (asn1_get_tag_der
-         (der + counter, der_len - counter, &class, &len2,
+         (der + counter, der_len, &class, &len2,
           &tag) != ASN1_SUCCESS)
        return ASN1_DER_ERROR;
-      if (counter + len2 > der_len)
-       return ASN1_DER_ERROR;
+
+      DECR_LEN(der_len, len2);
 
       if ((class != class_implicit) || (tag != tag_implicit))
        {
@@ -504,18 +503,16 @@ _asn1_extract_tag_der (asn1_node node, const unsigned char *der, int der_len,
       unsigned type = type_field (node->type);
       if (type == ASN1_ETYPE_TAG)
        {
-         counter = 0;
-         *ret_len = counter;
+         *ret_len = 0;
          return ASN1_SUCCESS;
        }
 
       if (asn1_get_tag_der
-         (der + counter, der_len - counter, &class, &len2,
+         (der + counter, der_len, &class, &len2,
           &tag) != ASN1_SUCCESS)
        return ASN1_DER_ERROR;
 
-      if (counter + len2 > der_len)
-       return ASN1_DER_ERROR;
+      DECR_LEN(der_len, len2);
 
       switch (type)
        {
@@ -568,6 +565,9 @@ _asn1_extract_tag_der (asn1_node node, const unsigned char *der, int der_len,
   counter += len2;
   *ret_len = counter;
   return ASN1_SUCCESS;
+
+cleanup:
+  return result;
 }
 
 static int