Convert::ASN1 (3)

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========================================================================

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NAME

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

VERSION

version 0.27

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)

DESCRIPTION

Convert::ASN1 encodes and decodes data structures using rules.

METHODS

new ( [

OPTIONS

] )

Contructor, creates a new object.

If given,

are the same ones as for ``configure ( )'' below.

error ()

Returns the last error.

configure (

OPTIONS

)

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

encode

Reference to a hash which contains various encode options.

decode

Reference to a hash which contains various decode options.

encoding

One of '

BER

' or '

DER

'. The default is '

BER

'

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.

Encode options

real

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

time

This controls how UTCTime and GeneralizedTime elements are encoded. The default is "withzone".

utctime

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

UTC

value.

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 "timezone" configure option.

raw

The value passed should already be in the correct format and will be copied into the

PDU

as-is.

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.

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

Decode options

time

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

utctime

The value returned will be a time value as returned by the "time" function.

withzone

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

raw

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

PDU.

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.

null

The value to decode

ASN.1 NULL

types into. If not set, it defaults to 1.

prepare (

ASN

)

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

prepare_file (

ASNPATH

)

Compile the description to be read from the specified pathname.

find (

MACRO

)

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

encode (

VARIABLES

)

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

decode (

PDU

)

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

registeroid (

OID, HANDLER

)

Register a handler for all elements that are "DEFINED BY" the given

must be a Convert::ASN1 object, e.g. as returned by ``find ( )''.

registertype (

NAME, OID, HANDLER

)

Register a handler for all elements named "NAME", that are "DEFINED BY" the given

must be a Convert::ASN1 object, e.g. as returned by ``find ( )''.

EXPORTS

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

IO

Functions

asn_recv (

SOCK, BUFFER, FLAGS

)

Will read a single element from the socket

SOCK

into

BUFFER. FLAGS

may be

MSG_PEEK

as exported by "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 "recv" function in perl itself.

It is recommended that if the socket is of type

SOCK_DGRAM

then "recv" be called directly instead of calling "asn_recv".

asn_read (

FH, BUFFER, OFFSET

)

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.

asn_send (

SOCK, BUFFER, FLAGS, TO

)

asn_send (

SOCK, BUFFER, FLAGS

)

Identical to calling "send", see perlfunc

asn_write (

FH, BUFFER

)

Identical to calling "syswrite" with 2 arguments, see perlfunc

asn_get (

FH

)

"asn_get" provides buffered

IO.

Because it needs a buffer

FH

must be a

GLOB

or a reference to a

GLOB.

"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.

asn_ready (

FH

)

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

Encode/Decode Functions

asn_tag (

CLASS, VALUE

)

Given

CLASS

and a

VALUE

, calculate an integer which when encoded will become the tag.

asn_decode_tag (

TAG

)

Decode the given

ASN.1

encoded "TAG".

asn_encode_tag (

TAG

)

Encode

TAG

value for encoding. We assume that the tag has been correctly generated with ``asn_tag (

CLASS, VALUE

)''.

asn_decode_length (

LEN

)

Decode the given

ASN.1

decoded "LEN".

asn_encode_length (

LEN

)

Encode the given "LEN" to its

ASN.1

encoding.

Constants

ASN_BIT_STR

ASN_BOOLEAN

ASN_ENUMERATED

ASN_GENERAL_TIME

ASN_IA5_STR

ASN_INTEGER

ASN_NULL

ASN_OBJECT_ID

ASN_OCTET_STR

ASN_PRINT_STR

ASN_REAL

ASN_SEQUENCE

ASN_SET

ASN_UTC_TIME

ASN_APPLICATION

ASN_CONTEXT

ASN_PRIVATE

ASN_UNIVERSAL

ASN_PRIMITIVE

ASN_CONSTRUCTOR

ASN_LONG_LEN

ASN_EXTENSION_ID

ASN_BIT

Debug Functions

asn_dump ( [

FH,

]

BUFFER

)

Try to decode the given buffer as

ASN.1

structure and dump it to the given file handle, or "STDERR" if the handle is not given.

asn_hexdump (

FH, BUFFER

)

EXPORT TAGS

:all

All exported functions

: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

:debug

asn_dump, asn_hexdump

:io

asn_recv, asn_send, asn_read, asn_write, asn_get, asn_ready

:tag

asn_tag, asn_decode_tag, asn_encode_tag, asn_decode_length, asn_encode_length

MAPPING ASN.1 TO PERL

Every element in the 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

or 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

or 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 For example with `` the array would contain strings. With `` { ... }'' 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

and hold it to include inline in your you can coerce it into the spec by defining the value as 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

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

Exceptions

There are some exceptions where Convert::ASN1 does not require an element to be named. These are {...}, {...} and 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 {...}.

TODO

*

XS

implementation.

*

More documentation.

*

More tests.

AUTHOR

Graham Barr <gbarr@cpan.org>

SUPPORT

Report issues via github at github.com/gbarr/perl-Convert-ASN1/issues

To contribute I encourage you to create a git fork of the repository at github.com/gbarr/perl-Convert-ASN1 do you work on a fresh branch created from master and submit a pull request

COPYRIGHT

Copyright (c) 2000-2012 Graham Barr <gbarr@cpan.org>. All rights reserved. This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.