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.
SET and SEQUENCE
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:
-
OpenSSL::ASN1::Sequence
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 = OpenSSL::ASN1::Integer.new(1) str = OpenSSL::ASN1::PrintableString.new('abc') sequence = OpenSSL::ASN1::Sequence.new( [ int, str ] )
Example - constructing a SET
int = OpenSSL::ASN1::Integer.new(1) str = OpenSSL::ASN1::PrintableString.new('abc') set = OpenSSL::ASN1::Set.new( [ 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 = OpenSSL::ASN1::OctetString.new("\x01") partial2 = OpenSSL::ASN1::OctetString.new("\x02") inf_octets = OpenSSL::ASN1::Constructive.new( [ partial1, partial2, OpenSSL::ASN1::EndOfContent.new ], OpenSSL::ASN1::OCTET_STRING, nil, :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.
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){
if(NIL_P(tag))
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 = sym_UNIVERSAL;
else
tag_class = sym_CONTEXT_SPECIFIC;
}
if(!SYMBOL_P(tag_class))
ossl_raise(eASN1Error, "invalid tag class");
if (tagging == sym_IMPLICIT && NUM2INT(tag) > 31)
ossl_raise(eASN1Error, "tag number for Universal too large");
}
else{
tag = INT2NUM(ossl_asn1_default_tag(self));
tagging = Qnil;
tag_class = sym_UNIVERSAL;
}
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;
}
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.
Example
int = OpenSSL::ASN1::Integer.new(42) zero_tagged_int = OpenSSL::ASN1::Integer.new(42, 0, :IMPLICIT) private_explicit_zero_tagged_int = OpenSSL::ASN1::Integer.new(42, 0, :EXPLICIT, :PRIVATE)
static VALUE
ossl_asn1cons_each(VALUE self)
{
rb_block_call(ossl_asn1_get_value(self), id_each, 0, 0, 0, 0);
return self;
}
Calls block once for each element in self, passing that element as parameter asn1. If no block is given, an enumerator is returned instead.
Example
asn1_ary.each do |asn1| puts asn1 end
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 (rb_obj_class(self) == cASN1Sequence ||
rb_obj_class(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 (rb_obj_class(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 = ASN1_object_size(constructed, RSTRING_LENINT(value), tag);
length = ASN1_object_size(constructed, seq_len, tn);
str = rb_str_new(0, length);
p = (unsigned char *)RSTRING_PTR(str);
if(tc == V_ASN1_UNIVERSAL)
ASN1_put_object(&p, constructed, RSTRING_LENINT(value), tn, tc);
else{
if(explicit){
ASN1_put_object(&p, constructed, seq_len, tn, tc);
ASN1_put_object(&p, constructed, RSTRING_LENINT(value), tag, V_ASN1_UNIVERSAL);
}
else{
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) {
ASN1_put_eoc(&p);
}
ossl_str_adjust(str, p);
return str;
}
See ASN1Data#to_der for details.