Convert::ASN1(3pm) User Contributed Perl Documentation Convert::ASN1(3pm)
NAME
Convert::ASN1 - ASN.1 Encode/Decode library
VERSION
version 0.33
SYNOPSIS
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 ASN.1 data structures using BER/DER
rules.
METHODS
new ( [OPTIONS] )
Contructor, creates a new object.
If given, OPTIONS are the same ones as for "configure ( OPTIONS )"
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 ASN.1 description 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 describes only one macro then encode/decode can
be called on this object. If ASN describes more than one ASN.1 macro
then "find" must be called. The method returns undef on error.
prepare_file ( ASNPATH )
Compile the ASN.1 description to be read from the specified pathname.
find ( MACRO )
Find a macro from a prepared ASN.1 description. Returns an object which
can be used for encode/decode.
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.
decode ( PDU )
Decode the PDU, returns a reference to a hash containing the values for
the PDU. Returns undef if there was an error.
registeroid ( OID, HANDLER )
Register a handler for all ASN.1 elements that are "DEFINED BY" the
given OID.
HANDLER must be a Convert::ASN1 object, e.g. as returned by "find (
MACRO )".
registertype ( NAME, OID, HANDLER )
Register a handler for all ASN.1 elements named "NAME", that are
"DEFINED BY" the given OID.
HANDLER must be a Convert::ASN1 object, e.g. as returned by "find (
MACRO )".
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 restriction 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 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 namespace 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.
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 {...}.
TODO
• XS implementation.
• More documentation.
• More tests.
AUTHOR
Graham Barr <gbarr@cpan.org>
SUPPORT
Report issues via github at
https://github.com/gbarr/perl-Convert-ASN1/issues
To contribute I encourage you to create a git fork of the repository at
https://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.
perl v5.32.1 2021-09-25 Convert::ASN1(3pm)
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