Fix a crash in the asn1parse command

Thanks to Sem Voigtländer for reporting this issue.

Reviewed-by: Rich Salz <rsalz@openssl.org>
Reviewed-by: Matthias St. Pierre <Matthias.St.Pierre@ncp-e.com>
(Merged from https://github.com/openssl/openssl/pull/5826)

apps/asn1pars.c

@@ -226,7 +226,7 @@ int asn1parse_main(int argc, char **argv)
             ASN1_TYPE *atmp;
             int typ;
             j = atoi(sk_OPENSSL_STRING_value(osk, i));
-            if (j == 0) {
+            if (j <= 0 || j >= tmplen) {
                 BIO_printf(bio_err, "'%s' is an invalid number\n",
                            sk_OPENSSL_STRING_value(osk, i));
                 continue;