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✏️ Editing: ASN1.pod

=head1 NAME

Convert::ASN1 - ASN.1 Encode/Decode library

=head1 VERSION

version 0.27

=head1 SYNOPSYS

use Convert::ASN1;

$asn = Convert::ASN1->new;
  $asn->prepare(q<

[APPLICATION 7] SEQUENCE {
      int INTEGER,
      str OCTET STRING
    }

>);

$pdu = $asn->encode( int => 7, str => "string");

$out = $asn->decode($pdu);
  print $out->{int}," ",$out->{str},"\n";

use Convert::ASN1 qw(:io);

$peer   = asn_recv($sock,$buffer,0);
  $nbytes = asn_read($fh, $buffer);
  $nbytes = asn_send($sock, $buffer, $peer);
  $nbytes = asn_send($sock, $buffer);
  $nbytes = asn_write($fh, $buffer);
  $buffer = asn_get($fh);
  $yes    = asn_ready($fh)

=head1 DESCRIPTION

Convert::ASN1 encodes and decodes ASN.1 data structures using BER/DER
rules.

=head1 METHODS

=head2 new ( [OPTIONS] )

Contructor, creates a new object.

If given, B<OPTIONS> are the same ones as for L</"configure ( OPTIONS )"> below.

=head2 error ()

Returns the last error.

=head2 configure ( OPTIONS )

Configure options to control how Convert::ASN1 will perform various tasks.
Options are passed as name-value pairs.

=over 4

=item encode

Reference to a hash which contains various encode options.

=item decode

Reference to a hash which contains various decode options.

=item encoding

One of 'BER' or 'DER'. The default is 'BER'

=item tagdefault

One of 'EXPLICIT' or 'IMPLICIT'.
Default tagging conventions are normally given in the ASN.1 module definition (not supported by the parser). The ASN.1 spec states EXPLICIT tagging is the default, but this option has IMPLICIT tagging default for backward compatibility reasons.

=back

Encode options

=over 4

=item real

Which encoding to use for real's. One of 'binary', 'nr1', 'nr2', 'nr3'

=item time

This controls how UTCTime and GeneralizedTime elements are encoded. The default
is C<withzone>.

=over 4

=item utctime

The value passed will be encoded without a zone, ie a UTC value.

=item withzone

The value will be encoded with a zone. By default it will be encoded
using the local time offset. The offset may be set using the C<timezone>
configure option.

=item raw

The value passed should already be in the correct format and will be copied
into the PDU as-is.

=back

=item timezone

By default UTCTime and GeneralizedTime will be encoded using the local
time offset from UTC. This will over-ride that. It is an offset from UTC
in seconds.  This option can be overridden by passing a reference to a
list of two values as the time value. The list should contain the time
value and the offset from UTC in seconds.

=item bigint

If during encoding an value greater than 32 bits is discovered and
is not already a big integer object, then the value will first be
converted into a big integer object. This option controls the big
integer class into which the objects will be blessed. The default
is to use Math::BigInt

=back

Decode options

=over 4

=item time

This controls how a UTCTime or a GeneralizedTime element will be decoded. The default
is C<utctime>.

=over 4

=item utctime

The value returned will be a time value as returned by the C<time> function.

=item withzone

The value returned will be a reference to an array of two values. The first is the
same as with C<utctime>, the second is the timezone offset, in seconds, that was
used in the encoding.

=item raw

The value returned will be the raw encoding as extracted from the PDU.

=back

=item bigint

If during decoding any big integers are discovered (integers greater
than 32 bits), they will be decoded into big integer objects. This option
controls the big integer class into which the objects will be blessed.
The default is to use Math::BigInt.

=item null

The value to decode ASN.1 NULL types into.
If not set, it defaults to C<1>.

=back

=head2 prepare ( ASN )

Compile the given ASN.1 descripton which can be passed as a string
or as a filehandle. The syntax used is very close to ASN.1, but has
a few differences. If the ASN decribes only one macro then encode/decode can be
called on this object. If ASN describes more than one ASN.1 macro then C<find>
must be called. The method returns undef on error.

=head2 prepare_file ( ASNPATH )

Compile the ASN.1 description to be read from the specified pathname.

=head2 find ( MACRO )

Find a macro from a prepared ASN.1 description. Returns an object which can
be used for encode/decode.

=head2 encode ( VARIABLES )

Encode a PDU. Top-level variable are passed as name-value pairs, or as a reference
to a hash containing them. Returns the encoded PDU, or undef on error.

=head2 decode ( PDU )

Decode the PDU, returns a reference to a hash containg the values for the PDU. Returns
undef if there was an error.

=head2 registeroid ( OID, HANDLER )

B<HANDLER> must be a Convert::ASN1 object, e.g. as returned by L</"find ( MACRO )">.

=head2 registertype ( NAME, OID, HANDLER )

B<HANDLER> must be a Convert::ASN1 object, e.g. as returned by L</"find ( MACRO )">.

=head1 EXPORTS

As well as providing an object interface for encoding/decoding PDUs Convert::ASN1
also provides the following functions.

=head2 IO Functions

=over 4

=item asn_recv ( SOCK, BUFFER, FLAGS )

Will read a single element from the socket SOCK into BUFFER.  FLAGS may
be MSG_PEEK as exported by C<Socket>. Returns the address of the sender,
or undef if there was an error. Some systems do not support the return
of the peer address when the socket is a connected socket, in these
cases the empty string will be returned. This is the same behaviour
as the C<recv> function in perl itself.

It is recommended that if the socket is of type SOCK_DGRAM then C<recv>
be called directly instead of calling C<asn_recv>.

=item asn_read ( FH, BUFFER, OFFSET )

=item asn_read ( FH, BUFFER )

Will read a single element from the filehandle FH into BUFFER. Returns the
number of bytes read if a complete element was read, -1 if an incomplete
element was read or undef if there was an error. If OFFSET is specified
then it is assumed that BUFFER already contains an incomplete element
and new data will be appended starting at OFFSET.

If FH is a socket the asn_recv is used to read the element, so the same
restiction applies if FH is a socket of type SOCK_DGRAM.

=item asn_send ( SOCK, BUFFER, FLAGS, TO )

=item asn_send ( SOCK, BUFFER, FLAGS )

Identical to calling C<send>, see L<perlfunc>

=item asn_write ( FH, BUFFER )

Identical to calling C<syswrite> with 2 arguments, see L<perlfunc>

=item asn_get ( FH )

C<asn_get> provides buffered IO. Because it needs a buffer FH must be a GLOB
or a reference to a GLOB. C<asn_get> will use two entries in the hash element
of the GLOB to use as its buffer:

asn_buffer - input buffer
  asn_need   - number of bytes needed for the next element, if known

Returns an element or undef if there was an error.

=item asn_ready ( FH )

C<asn_ready> works with C<asn_get>. It will return true if C<asn_get> has already
read enough data into the buffer to return a complete element.

=back

=head2 Encode/Decode Functions

=over 4

=item asn_tag ( CLASS, VALUE )

Given B<CLASS> and a B<VALUE>, calculate an integer which when encoded
will become the tag.

=item asn_decode_tag ( TAG )

Decode the given ASN.1 encoded C<TAG>.

=item asn_encode_tag ( TAG )

Encode B<TAG> value for encoding.
We assume that the tag has been correctly generated with L</"asn_tag ( CLASS, VALUE )">.

=item asn_decode_length ( LEN )

Decode the given ASN.1 decoded C<LEN>.

=item asn_encode_length ( LEN )

Encode the given C<LEN> to its ASN.1 encoding.

=back

=head2 Constants

=over 4

=item ASN_BIT_STR

=item ASN_BOOLEAN

=item ASN_ENUMERATED

=item ASN_GENERAL_TIME

=item ASN_IA5_STR

=item ASN_INTEGER

=item ASN_NULL

=item ASN_OBJECT_ID

=item ASN_OCTET_STR

=item ASN_PRINT_STR

=item ASN_REAL

=item ASN_SEQUENCE

=item ASN_SET

=item ASN_UTC_TIME

=item ASN_APPLICATION

=item ASN_CONTEXT

=item ASN_PRIVATE

=item ASN_UNIVERSAL

=item ASN_PRIMITIVE

=item ASN_CONSTRUCTOR

=item ASN_LONG_LEN

=item ASN_EXTENSION_ID

=item ASN_BIT

=back

=head2 Debug Functions

=over 4

=item asn_dump ( [FH,] BUFFER )

Try to decode the given buffer as ASN.1 structure and dump it to the
given file handle, or C<STDERR> if the handle is not given.

=item asn_hexdump ( FH, BUFFER )

=back

=head1 EXPORT TAGS

=over 4

=item :all

All exported functions

=item :const

ASN_BOOLEAN,     ASN_INTEGER,      ASN_BIT_STR,      ASN_OCTET_STR,
ASN_NULL,        ASN_OBJECT_ID,    ASN_REAL,         ASN_ENUMERATED,
ASN_SEQUENCE,    ASN_SET,          ASN_PRINT_STR,    ASN_IA5_STR,
ASN_UTC_TIME,    ASN_GENERAL_TIME,
ASN_UNIVERSAL,   ASN_APPLICATION,  ASN_CONTEXT,      ASN_PRIVATE,
ASN_PRIMITIVE,   ASN_CONSTRUCTOR,  ASN_LONG_LEN,     ASN_EXTENSION_ID, ASN_BIT

=item :debug

asn_dump, asn_hexdump

=item :io

asn_recv, asn_send, asn_read, asn_write, asn_get, asn_ready

=item :tag

asn_tag, asn_decode_tag, asn_encode_tag, asn_decode_length, asn_encode_length

=back

=head1 MAPPING ASN.1 TO PERL

Every element in the ASN.1 definition has a name, in perl a hash is used
with these names as an index and the element value as the hash value.

# ASN.1
  int INTEGER,
  str OCTET STRING

# Perl
  { int => 5, str => "text" }

In the case of a SEQUENCE, SET or CHOICE then the value in the namespace will
be a hash reference which will be the namespce for the elements with
that element.

# ASN.1
  int INTEGER,
  seq SEQUENCE {
    str OCTET STRING,
    bool BOOLEAN
  }

# Perl
  { int => 5, seq => { str => "text", bool => 1}}

If the element is a SEQUENCE OF, or SET OF, then the value in the namespace
will be an array reference. The elements in the array will be of
the type expected by the type following the OF. For example
with "SEQUENCE OF STRING" the array would contain strings. With
"SEQUENCE OF SEQUENCE { ... }" the array will contain hash references
which will be used as namespaces

# ASN.1
  int INTEGER,
  str SEQUENCE OF OCTET STRING

# Perl
  { int => 5, str => [ "text1", "text2"]}

# ASN.1
  int INTEGER,
  str SEQUENCE OF SEQUENCE {
    type OCTET STRING,
    value INTEGER
  }

# Perl
  { int => 5, str => [
    { type => "abc", value => 4 },
    { type => "def", value => -1 },
  ]}

Finally, if you wish to pre-parse ASN.1 and hold it to include
inline in your PDU, you can coerce it into the ASN.1 spec by
defining the value as ANY in the schema, and then pass the pre
encoded value inline.

# ASN.1
  int INTEGER,
  str OCTET STRING,
  pre ANY

# Perl
  { int => 5, str => "text", pre=>"\x03\x03\x00\x0a\x05" }

passes a pre-encoded BIT STRING instance as hex text. -But
it could be a previous run of $obj->encode() from another run
held in some variable.

=head2 Exceptions

There are some exceptions where Convert::ASN1 does not require an element to be named.
These are SEQUENCE {...}, SET {...} and CHOICE. In each case if the element is not
given a name then the elements inside the {...} will share the same namespace as
the elements outside of the {...}.

=head1 TODO

=over 4

=item *

XS implementation.

=item *

MR SKB