+/*
+ * Serialize trusted certificate to *pp, or just return the required buffer
+ * length if pp == NULL.
+ *
+ * When pp is not NULL, but *pp == NULL, we allocate the buffer, but since
+ * we're writing two ASN.1 objects back to back, we can't have i2d_X509() do
+ * the allocation, nor can we allow i2d_X509_CERT_AUX() to increment the
+ * allocated buffer.
+ */
+int i2d_X509_AUX(X509 *a, unsigned char **pp)
+{
+ int length;
+ unsigned char *tmp;
+
+ /* Buffer provided by caller */
+ if (pp == NULL || *pp != NULL)
+ return i2d_x509_aux_internal(a, pp);
+
+ /* Obtain the combined length */
+ if ((length = i2d_x509_aux_internal(a, NULL)) <= 0)
+ return length;
+
+ /* Allocate requisite combined storage */
+ *pp = tmp = OPENSSL_malloc(length);
+ if (tmp == NULL)
+ return -1; /* Push error onto error stack? */
+
+ /* Encode, but keep *pp at the originally malloced pointer */
+ length = i2d_x509_aux_internal(a, &tmp);
+ if (length <= 0) {
+ OPENSSL_free(*pp);
+ *pp = NULL;
+ }
+ return length;
+}
+