Convert::ASN1 encodes and decodes ASN.1 data structures using BER/DER
rules.
METHODS
new
Contructor, creates a new object.
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', 'der', 'per'. Currently not used
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 overriden 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.
prepare ( ASN )
Compile the given ASN.1 descripton. The syntax used is very close to ASN.1, but has
a few differnces. 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 "find"
must be called.
find ( MACRO )
Find a macro froma 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 containg the values for the PDU. Returns
undef if there was an error.
EXPORTS
As well as providing an object interface for encoding/decoding PDUs Convert::ASN1
also provides the follow 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 reccomended 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 the perlfunc manpage
asn_write FH, BUFFER
Identical to calling "syswrite" with 2 arguments, see the perlfunc manpage
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 it's 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.
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.
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 },
]}
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 {...}.
Copyright (c) 2000 Graham Barr <gbarr@pobox.com>. All rights reserved.
This program is free software; you can redistribute it and/or
modify it under the same terms as Perl itself.