Fix bug 1202868, r=dkeeler
authorRyan Sleevi <ryan.sleevi@gmail.com>
Thu, 15 Oct 2015 19:51:51 +0200
changeset 11655 4dc247276e581ccdafc8d4c6236cb6b055348f65
parent 11654 8ac7f47eecbbde13cf873e91123e4a82b228c343
child 11656 f1a84b2a75affb8bde428ae9735f582f9644f0ae
push id808
push userkaie@kuix.de
push dateThu, 15 Oct 2015 17:52:28 +0000
reviewersdkeeler
bugs1202868
Fix bug 1202868, r=dkeeler
lib/util/secasn1d.c
--- a/lib/util/secasn1d.c
+++ b/lib/util/secasn1d.c
@@ -1787,17 +1787,112 @@ sec_asn1d_next_substring (sec_asn1d_stat
 
 	state->pending -= child_consumed;
 	if (state->pending == 0)
 	    done = PR_TRUE;
     } else {
 	PORT_Assert (state->indefinite);
 
 	item = (SECItem *)(child->dest);
-	if (item != NULL && item->data != NULL) {
+
+	/**
+	 * At this point, there's three states at play:
+	 *   child: The element that was just parsed
+	 *   state: The currently processed element
+	 *   'parent' (aka state->parent): The enclosing construct
+	 *      of state, or NULL if this is the top-most element.
+	 *
+	 * This state handles both substrings of a constructed string AND
+	 * child elements of items whose template type was that of
+	 * SEC_ASN1_ANY, SEC_ASN1_SAVE, SEC_ASN1_ANY_CONTENTS, SEC_ASN1_SKIP
+	 * template, as described in sec_asn1d_prepare_for_contents. For
+	 * brevity, these will be referred to as 'string' and 'any' types.
+	 *
+	 * This leads to the following possibilities:
+	 *   1: This element is an indefinite length string, part of a
+	 *      definite length string.
+	 *   2: This element is an indefinite length string, part of an
+	 *      indefinite length string.
+	 *   3: This element is an indefinite length any, part of a
+	 *      definite length any.
+	 *   4: This element is an indefinite length any, part of an
+	 *      indefinite length any.
+	 *   5: This element is an indefinite length any and does not
+	 *      meet any of the above criteria. Note that this would include
+	 *      an indefinite length string type matching an indefinite
+	 *      length any template.
+	 *
+	 * In Cases #1 and #3, the definite length 'parent' element will
+	 * have allocated state->dest based on the parent elements definite
+	 * size. During the processing of 'child', sec_asn1d_parse_leaf will
+	 * have copied the (string, any) data directly into the offset of
+	 * dest, as appropriate, so there's no need for this class to still
+	 * store the child - it's already been processed.
+	 *
+	 * In Cases #2 and #4, dest will be set to the parent element's dest,
+	 * but dest->data will not have been allocated yet, due to the
+	 * indefinite length encoding. In this situation, it's necessary to
+	 * hold onto child (and all other children) until the EOC, at which
+	 * point, it becomes possible to compute 'state's overall length. Once
+	 * 'state' has a computed length, this can then be fed to 'parent' (via
+	 * this state), and then 'parent' can similarly compute the length of
+	 * all of its children up to the EOC, which will ultimately transit to
+	 * sec_asn1d_concat_substrings, determine the overall size needed,
+	 * allocate, and copy the contents (of all of parent's children, which
+	 * would include 'state', just as 'state' will have copied all of its
+	 * children via sec_asn1d_concat_substrings)
+	 *
+	 * The final case, Case #5, will manifest in that item->data and
+	 * item->len will be NULL/0, respectively, since this element was
+	 * indefinite-length encoded. In that case, both the tag and length will
+	 * already exist in state's subitems, via sec_asn1d_record_any_header,
+	 * and so the contents (aka 'child') should be added to that list of
+	 * items to concatenate in sec_asn1d_concat_substrings once the EOC
+	 * is encountered.
+	 *
+	 * To distinguish #2/#4 from #1/#3, it's sufficient to walk the ancestor
+	 * tree. If the current type is a string type, then the enclosing
+	 * construct will be that same type (#1/#2). If the current type is an
+	 * any type, then the enclosing construct is either an any type (#3/#4)
+	 * or some other type (#5). Since this is BER, this nesting relationship
+	 * between 'state' and 'parent' may go through several levels of
+	 * constructed encoding, so continue walking the ancestor chain until a
+	 * clear determination can be made.
+	 *
+	 * The variable preallocatedString is used to indicate Case #1/#3,
+	 * indicating an in-place copy has already occurred, and Cases #2, #4,
+	 * and #5 all have the same behaviour of adding a new substring.
+	 */
+	PRBool preallocatedString = PR_FALSE;
+	sec_asn1d_state *temp_state = state;
+	while (temp_state && item == temp_state->dest && temp_state->indefinite) {
+	    sec_asn1d_state *parent = sec_asn1d_get_enclosing_construct(temp_state);
+	    if (!parent || parent->underlying_kind != temp_state->underlying_kind) {
+	        /* Case #5 - Either this is a top-level construct or it is part
+	         * of some other element (e.g. a SEQUENCE), in which case, a
+	         * new item should be allocated. */
+	        break;
+	    }
+	    if (!parent->indefinite) {
+	        /* Cases #1 / #3 - A definite length ancestor exists, for which
+	         * this is a substring that has already copied into dest. */
+	        preallocatedString = PR_TRUE;
+	        break;
+	    }
+	    if (!parent->substring) {
+	        /* Cases #2 / #4 - If the parent is not a substring, but is
+	         * indefinite, then there's nothing further up that may have
+	         * preallocated dest, thus child will not have already
+		 * been copied in place, therefore it's necessary to save child
+		 * as a subitem. */
+	        break;
+	    }
+	    temp_state = parent;
+	}
+	if (item != NULL && item->data != NULL && !preallocatedString) {
 	    /*
 	     * Save the string away for later concatenation.
 	     */
 	    PORT_Assert (item->data != NULL);
 	    sec_asn1d_add_to_subitems (state, item->data, item->len, PR_FALSE);
 	    /*
 	     * Clear the child item for the next round.
 	     */