class OpenSSL::ASN1::Constructive

The parent class for all constructed encodings. The value attribute of a Constructive is always an Array. Attributes are the same as for ASN1Data, with the addition of tagging.


Most constructed encodings come in the form of a SET or a SEQUENCE. These encodings are represented by one of the two sub-classes of Constructive:

Please note that tagged sequences and sets are still parsed as instances of ASN1Data. Find further details on tagged values there.

Example - constructing a SEQUENCE

int =
str ='abc')
sequence = [ int, str ] )

Example - constructing a SET

int =
str ='abc')
set = [ int, str ] )

Infinite length primitive values

The only case where Constructive is used directly is for infinite length encodings of primitive values. These encodings are always constructed, with the contents of the value Array being either UNIVERSAL non-infinite length partial encodings of the actual value or again constructive encodings with infinite length (i.e. infinite length primitive encodings may be constructed recursively with another infinite length value within an already infinite length value). Each partial encoding must be of the same UNIVERSAL type as the overall encoding. The value of the overall encoding consists of the concatenation of each partial encoding taken in sequence. The value array of the outer infinite length value must end with a OpenSSL::ASN1::EndOfContent instance.

Please note that it is not possible to encode Constructive without the infinite_length attribute being set to true, use OpenSSL::ASN1::Sequence or OpenSSL::ASN1::Set in these cases instead.

Example - Infinite length OCTET STRING

partial1 ="\x01")
partial2 ="\x02")
inf_octets = [ partial1,
                                              :UNIVERSAL )
# The real value of inf_octets is "\x01\x02", i.e. the concatenation
# of partial1 and partial2
inf_octets.infinite_length = true
der = inf_octets.to_der
asn1 = OpenSSL::ASN1.decode(der)
puts asn1.infinite_length # => true



May be used as a hint for encoding a value either implicitly or explicitly by setting it either to :IMPLICIT or to :EXPLICIT. tagging is not set when a ASN.1 structure is parsed using OpenSSL::ASN1.decode.

Public Class Methods value [, tag, tagging, tag_class ]) → Primitive click to toggle source

value: is mandatory.

tag: optional, may be specified for tagged values. If no tag is specified, the UNIVERSAL tag corresponding to the Primitive sub-class is used by default.

tagging: may be used as an encoding hint to encode a value either explicitly or implicitly, see ASN1 for possible values.

tag_class: if tag and tagging are nil then this is set to :UNIVERSAL by default. If either tag or tagging are set then :CONTEXT_SPECIFIC is used as the default. For possible values please cf. ASN1.


int =
zero_tagged_int =, 0, :IMPLICIT)
private_explicit_zero_tagged_int =, 0, :EXPLICIT, :PRIVATE)
static VALUE
ossl_asn1_initialize(int argc, VALUE *argv, VALUE self)
    VALUE value, tag, tagging, tag_class;

    rb_scan_args(argc, argv, "13", &value, &tag, &tagging, &tag_class);
    if(argc > 1){
            ossl_raise(eASN1Error, "must specify tag number");
        if(!NIL_P(tagging) && !SYMBOL_P(tagging))
            ossl_raise(eASN1Error, "invalid tagging method");
        if(NIL_P(tag_class)) {
            if (NIL_P(tagging))
                tag_class = ID2SYM(sUNIVERSAL);
                tag_class = ID2SYM(sCONTEXT_SPECIFIC);
            ossl_raise(eASN1Error, "invalid tag class");
        if(!NIL_P(tagging) && SYM2ID(tagging) == sIMPLICIT && NUM2INT(tag) > 31)
            ossl_raise(eASN1Error, "tag number for Universal too large");
        tag = INT2NUM(ossl_asn1_default_tag(self));
        tagging = Qnil;
        tag_class = ID2SYM(sUNIVERSAL);
    ossl_asn1_set_tag(self, tag);
    ossl_asn1_set_value(self, value);
    ossl_asn1_set_tagging(self, tagging);
    ossl_asn1_set_tag_class(self, tag_class);
    ossl_asn1_set_infinite_length(self, Qfalse);

    return self;

Public Instance Methods

each { |asn1| block } → asn1_ary click to toggle source

Calls block once for each element in self, passing that element as parameter asn1. If no block is given, an enumerator is returned instead.


asn1_ary.each do |asn1|
  puts asn1
static VALUE
ossl_asn1cons_each(VALUE self)
    return self;
to_der → DER-encoded String click to toggle source

See OpenSSL::ASN1::ASN1Data#to_der for details.

static VALUE
ossl_asn1cons_to_der(VALUE self)
    int tag, tn, tc, explicit, constructed = 1;
    int found_prim = 0, seq_len;
    long length;
    unsigned char *p;
    VALUE value, str, inf_length;

    tn = NUM2INT(ossl_asn1_get_tag(self));
    tc = ossl_asn1_tag_class(self);
    inf_length = ossl_asn1_get_infinite_length(self);
    if (inf_length == Qtrue) {
        VALUE ary, example;
        constructed = 2;
        if (CLASS_OF(self) == cASN1Sequence ||
            CLASS_OF(self) == cASN1Set) {
            tag = ossl_asn1_default_tag(self);
        else { /* must be a constructive encoding of a primitive value */
            ary = ossl_asn1_get_value(self);
            if (!rb_obj_is_kind_of(ary, rb_cArray))
                ossl_raise(eASN1Error, "Constructive value must be an Array");
            /* Recursively descend until a primitive value is found.
            The overall value of the entire constructed encoding
            is of the type of the first primitive encoding to be
            found. */
            while (!found_prim){
                example = rb_ary_entry(ary, 0);
                if (rb_obj_is_kind_of(example, cASN1Primitive)){
                    found_prim = 1;
                else {
                    /* example is another ASN1Constructive */
                    if (!rb_obj_is_kind_of(example, cASN1Constructive)){
                        ossl_raise(eASN1Error, "invalid constructed encoding");
                        return Qnil; /* dummy */
                    ary = ossl_asn1_get_value(example);
            tag = ossl_asn1_default_tag(example);
    else {
        if (CLASS_OF(self) == cASN1Constructive)
            ossl_raise(eASN1Error, "Constructive shall only be used with infinite length");
        tag = ossl_asn1_default_tag(self);
    explicit = ossl_asn1_is_explicit(self);
    value = join_der(ossl_asn1_get_value(self));

    seq_len = ossl_asn1_object_size(constructed, RSTRING_LENINT(value), tag);
    length = ossl_asn1_object_size(constructed, seq_len, tn);
    str = rb_str_new(0, length);
    p = (unsigned char *)RSTRING_PTR(str);
    if(tc == V_ASN1_UNIVERSAL)
        ossl_asn1_put_object(&p, constructed, RSTRING_LENINT(value), tn, tc);
            ossl_asn1_put_object(&p, constructed, seq_len, tn, tc);
            ossl_asn1_put_object(&p, constructed, RSTRING_LENINT(value), tag, V_ASN1_UNIVERSAL);
            ossl_asn1_put_object(&p, constructed, RSTRING_LENINT(value), tn, tc);
    memcpy(p, RSTRING_PTR(value), RSTRING_LEN(value));
    p += RSTRING_LEN(value);

    /* In this case we need an additional EOC (one for the explicit part and
     * one for the Constructive itself. The EOC for the Constructive is
     * supplied by the user, but that for the "explicit wrapper" must be
     * added here.
    if (explicit && inf_length == Qtrue) {
    ossl_str_adjust(str, p);

    return str;