### -*- mode: Perl -*-
######################################################################
### BER (Basic Encoding Rules) encoding and decoding.
######################################################################
### Copyright (c) 1995-2008, Simon Leinen.
###
### This program is free software; you can redistribute it under the
### "Artistic License 2.0" included in this distribution
### (file "Artistic").
######################################################################
### This module implements encoding and decoding of ASN.1-based data
### structures using the Basic Encoding Rules (BER). Only the subset
### necessary for SNMP is implemented.
######################################################################
### Created by: Simon Leinen <simon@switch.ch>
###
### Contributions and fixes by:
###
### Andrzej Tobola <san@iem.pw.edu.pl>: Added long String decode
### Tobias Oetiker <tobi@oetiker.ch>: Added 5 Byte Integer decode ...
### Dave Rand <dlr@Bungi.com>: Added SysUpTime decode
### Philippe Simonet <sip00@vg.swissptt.ch>: Support larger subids
### Yufang HU <yhu@casc.com>: Support even larger subids
### Mike Mitchell <Mike.Mitchell@sas.com>: New generalized encode_int()
### Mike Diehn <mdiehn@mindspring.net>: encode_ip_address()
### Rik Hoorelbeke <rik.hoorelbeke@pandora.be>: encode_oid() fix
### Brett T Warden <wardenb@eluminant.com>: pretty UInteger32
### Bert Driehuis <driehuis@playbeing.org>: Handle SNMPv2 exception codes
### Jakob Ilves (/IlvJa) <jakob.ilves@oracle.com>: PDU decoding
### Jan Kasprzak <kas@informatics.muni.cz>: Fix for PDU syntax check
### Milen Pavlov <milen@batmbg.com>: Recognize variant length for ints
######################################################################
package BER;
require 5.002;
use strict;
use vars qw(@ISA @EXPORT $VERSION $pretty_print_timeticks
%pretty_printer %default_printer $errmsg);
use Exporter;
$VERSION = '1.05';
@ISA = qw(Exporter);
@EXPORT = qw(context_flag constructor_flag
encode_int encode_int_0 encode_null encode_oid
encode_sequence encode_tagged_sequence
encode_string encode_ip_address encode_timeticks
encode_uinteger32 encode_counter32 encode_counter64
encode_gauge32
decode_sequence decode_by_template
pretty_print pretty_print_timeticks
hex_string hex_string_of_type
encoded_oid_prefix_p errmsg
register_pretty_printer unregister_pretty_printer);
### Variables
## Bind this to zero if you want to avoid that TimeTicks are converted
## into "human readable" strings containing days, hours, minutes and
## seconds.
##
## If the variable is zero, pretty_print will simply return an
## unsigned integer representing hundredths of seconds.
##
$pretty_print_timeticks = 1;
### Prototypes
sub encode_header ($$);
sub encode_int_0 ();
sub encode_int ($);
sub encode_oid (@);
sub encode_null ();
sub encode_sequence (@);
sub encode_tagged_sequence ($@);
sub encode_string ($);
sub encode_ip_address ($);
sub encode_timeticks ($);
sub pretty_print ($);
sub pretty_using_decoder ($$);
sub pretty_string ($);
sub pretty_intlike ($);
sub pretty_unsignedlike ($);
sub pretty_oid ($);
sub pretty_uptime ($);
sub pretty_uptime_value ($);
sub pretty_ip_address ($);
sub pretty_generic_sequence ($);
sub register_pretty_printer ($);
sub unregister_pretty_printer ($);
sub hex_string ($);
sub hex_string_of_type ($$);
sub decode_oid ($);
sub decode_by_template;
sub decode_by_template_2;
sub decode_sequence ($);
sub decode_int ($);
sub decode_intlike ($);
sub decode_unsignedlike ($);
sub decode_intlike_s ($$);
sub decode_string ($);
sub decode_length ($@);
sub encoded_oid_prefix_p ($$);
sub decode_subid ($$$);
sub decode_generic_tlv ($);
sub error (@);
sub template_error ($$$);
sub version () { $VERSION; }
### Flags for different types of tags
sub universal_flag { 0x00 }
sub application_flag { 0x40 }
sub context_flag { 0x80 }
sub private_flag { 0xc0 }
sub primitive_flag { 0x00 }
sub constructor_flag { 0x20 }
### Universal tags
sub boolean_tag { 0x01 }
sub int_tag { 0x02 }
sub bit_string_tag { 0x03 }
sub octet_string_tag { 0x04 }
sub null_tag { 0x05 }
sub object_id_tag { 0x06 }
sub sequence_tag { 0x10 }
sub set_tag { 0x11 }
sub uptime_tag { 0x43 }
### Flag for length octet announcing multi-byte length field
sub long_length { 0x80 }
### SNMP specific tags
sub snmp_ip_address_tag { 0x00 | application_flag () }
sub snmp_counter32_tag { 0x01 | application_flag () }
sub snmp_gauge32_tag { 0x02 | application_flag () }
sub snmp_timeticks_tag { 0x03 | application_flag () }
sub snmp_opaque_tag { 0x04 | application_flag () }
sub snmp_nsap_address_tag { 0x05 | application_flag () }
sub snmp_counter64_tag { 0x06 | application_flag () }
sub snmp_uinteger32_tag { 0x07 | application_flag () }
## Error codes (SNMPv2 and later)
##
sub snmp_nosuchobject { context_flag () | 0x00 }
sub snmp_nosuchinstance { context_flag () | 0x01 }
sub snmp_endofmibview { context_flag () | 0x02 }
### pretty-printer initialization code. Create a hash with
### the most common types of pretty-printer routines.
BEGIN {
$default_printer{int_tag()} = \&pretty_intlike;
$default_printer{snmp_counter32_tag()} = \&pretty_unsignedlike;
$default_printer{snmp_gauge32_tag()} = \&pretty_unsignedlike;
$default_printer{snmp_counter64_tag()} = \&pretty_unsignedlike;
$default_printer{snmp_uinteger32_tag()} = \&pretty_unsignedlike;
$default_printer{octet_string_tag()} = \&pretty_string;
$default_printer{object_id_tag()} = \&pretty_oid;
$default_printer{snmp_ip_address_tag()} = \&pretty_ip_address;
%pretty_printer = %default_printer;
}
#### Encoding
sub encode_header ($$) {
my ($type,$length) = @_;
return pack ("C C", $type, $length) if $length < 128;
return pack ("C C C", $type, long_length | 1, $length) if $length < 256;
return pack ("C C n", $type, long_length | 2, $length) if $length < 65536;
return error ("Cannot encode length $length yet");
}
sub encode_int_0 () {
return pack ("C C C", 2, 1, 0);
}
sub encode_int ($) {
return encode_intlike ($_[0], int_tag);
}
sub encode_uinteger32 ($) {
return encode_intlike ($_[0], snmp_uinteger32_tag);
}
sub encode_counter32 ($) {
return encode_intlike ($_[0], snmp_counter32_tag);
}
sub encode_counter64 ($) {
return encode_intlike ($_[0], snmp_counter64_tag);
}
sub encode_gauge32 ($) {
return encode_intlike ($_[0], snmp_gauge32_tag);
}
sub encode_intlike ($$) {
my ($int, $tag)=@_;
my ($sign, $val, @vals);
$sign = ($int >= 0) ? 0 : 0xff;
if (ref $int && $int->isa ("Math::BigInt")) {
for(;;) {
$val = $int->copy()->bmod (256);
unshift(@vals, $val);
return encode_header ($tag, $#vals + 1).pack ("C*", @vals)
if ($int >= -128 && $int < 128);
$int->bsub ($sign)->bdiv (256);
}
} else {
for(;;) {
$val = $int & 0xff;
unshift(@vals, $val);
return encode_header ($tag, $#vals + 1).pack ("C*", @vals)
if ($int >= -128 && $int < 128);
$int -= $sign, $int = int($int / 256);
}
}
}
sub encode_oid (@) {
my @oid = @_;
my ($result,$subid);
$result = '';
## Ignore leading empty sub-ID. The favourite reason for
## those to occur is that people cut&paste numeric OIDs from
## CMU/UCD SNMP including the leading dot.
shift @oid if $oid[0] eq '';
return error ("Object ID too short: ", join('.',@oid))
if $#oid < 1;
## The first two subids in an Object ID are encoded as a single
## byte in BER, according to a funny convention. This poses
## restrictions on the ranges of those subids. In the past, I
## didn't check for those. But since so many people try to use
## OIDs in CMU/UCD SNMP's format and leave out the mib-2 or
## enterprises prefix, I introduced this check to catch those
## errors.
##
return error ("first subid too big in Object ID ", join('.',@oid))
if $oid[0] > 2;
$result = shift (@oid) * 40;
$result += shift @oid;
return error ("second subid too big in Object ID ", join('.',@oid))
if $result > 255;
$result = pack ("C", $result);
foreach $subid (@oid) {
if ( ($subid>=0) && ($subid<128) ){ #7 bits long subid
$result .= pack ("C", $subid);
} elsif ( ($subid>=128) && ($subid<16384) ){ #14 bits long subid
$result .= pack ("CC", 0x80 | $subid >> 7, $subid & 0x7f);
}
elsif ( ($subid>=16384) && ($subid<2097152) ) {#21 bits long subid
$result .= pack ("CCC",
0x80 | (($subid>>14) & 0x7f),
0x80 | (($subid>>7) & 0x7f),
$subid & 0x7f);
} elsif ( ($subid>=2097152) && ($subid<268435456) ){ #28 bits long subid
$result .= pack ("CCCC",
0x80 | (($subid>>21) & 0x7f),
0x80 | (($subid>>14) & 0x7f),
0x80 | (($subid>>7) & 0x7f),
$subid & 0x7f);
} elsif ( ($subid>=268435456) && ($subid<4294967296) ){ #32 bits long subid
$result .= pack ("CCCCC",
0x80 | (($subid>>28) & 0x0f), #mask the bits beyond 32
0x80 | (($subid>>21) & 0x7f),
0x80 | (($subid>>14) & 0x7f),
0x80 | (($subid>>7) & 0x7f),
$subid & 0x7f);
} else {
return error ("Cannot encode subid $subid");
}
}
encode_header (object_id_tag, length $result).$result;
}
sub encode_null () { encode_header (null_tag, 0); }
sub encode_sequence (@) { encode_tagged_sequence (sequence_tag, @_); }
sub encode_tagged_sequence ($@) {
my ($tag,$result);
$tag = shift @_;
$result = join '',@_;
return encode_header ($tag | constructor_flag, length $result).$result;
}
sub encode_string ($) {
my ($string)=@_;
return encode_header (octet_string_tag, length $string).$string;
}
sub encode_ip_address ($) {
my ($addr)=@_;
my @octets;
if (length $addr == 4) {
## Four bytes... let's suppose that this is a binary IP address
## in network byte order.
return encode_header (snmp_ip_address_tag, length $addr).$addr;
} elsif (@octets = ($addr =~ /^([0-9]+)\.([0-9]+)\.([0-9]+)\.([0-9]+)$/)) {
return encode_ip_address (pack ("CCCC", @octets));
} else {
return error ("IP address must be four bytes long or a dotted-quad");
}
}
sub encode_timeticks ($) {
my ($tt) = @_;
return encode_intlike ($tt, snmp_timeticks_tag);
}
#### Decoding
sub pretty_print ($) {
my ($packet) = @_;
return undef unless defined $packet;
my $result = ord (substr ($packet, 0, 1));
if (exists ($pretty_printer{$result})) {
my $c_ref = $pretty_printer{$result};
return &$c_ref ($packet);
}
return ($pretty_print_timeticks
? pretty_uptime ($packet)
: pretty_unsignedlike ($packet))
if $result == uptime_tag;
return "(null)" if $result == null_tag;
return error ("Exception code: noSuchObject") if $result == snmp_nosuchobject;
return error ("Exception code: noSuchInstance") if $result == snmp_nosuchinstance;
return error ("Exception code: endOfMibView") if $result == snmp_endofmibview;
# IlvJa
# pretty print sequences and their contents.
my $ctx_cons_flags = context_flag | constructor_flag;
if($result == (&constructor_flag | &sequence_tag) # sequence
|| $result == (0 | $ctx_cons_flags) #get_request
|| $result == (1 | $ctx_cons_flags) #getnext_request
|| $result == (2 | $ctx_cons_flags) #response
|| $result == (3 | $ctx_cons_flags) #set_request
|| $result == (4 | $ctx_cons_flags) #trap_request
|| $result == (5 | $ctx_cons_flags) #getbulk_request
|| $result == (6 | $ctx_cons_flags) #inform_request
|| $result == (7 | $ctx_cons_flags) #trap2_request
)
{
my $pretty_result = pretty_generic_sequence($packet);
$pretty_result =~ s/^/ /gm; #Indent.
my $seq_type_desc =
{
(constructor_flag | sequence_tag) => "Sequence",
(0 | $ctx_cons_flags) => "GetRequest",
(1 | $ctx_cons_flags) => "GetNextRequest",
(2 | $ctx_cons_flags) => "Response",
(3 | $ctx_cons_flags) => "SetRequest",
(4 | $ctx_cons_flags) => "Trap",
(5 | $ctx_cons_flags) => "GetBulkRequest",
(6 | $ctx_cons_flags) => "InformRequest",
(7 | $ctx_cons_flags) => "SNMPv2-Trap",
(8 | $ctx_cons_flags) => "Report",
}->{($result)};
return $seq_type_desc . "{\n" . $pretty_result . "\n}";
}
return sprintf ("#<unprintable BER type 0x%x>", $result);
}
sub pretty_using_decoder ($$) {
my ($decoder, $packet) = @_;
my ($decoded,$rest);
($decoded,$rest) = &$decoder ($packet);
return error ("Junk after object") unless $rest eq '';
return $decoded;
}
sub pretty_string ($) {
pretty_using_decoder (\&decode_string, $_[0]);
}
sub pretty_intlike ($) {
my $decoded = pretty_using_decoder (\&decode_intlike, $_[0]);
$decoded;
}
sub pretty_unsignedlike ($) {
return pretty_using_decoder (\&decode_unsignedlike, $_[0]);
}
sub pretty_oid ($) {
my ($oid) = shift;
my ($result,$subid,$next);
my (@oid);
$result = ord (substr ($oid, 0, 1));
return error ("Object ID expected") unless $result == object_id_tag;
($result, $oid) = decode_length ($oid, 1);
return error ("inconsistent length in OID") unless $result == length $oid;
@oid = ();
$subid = ord (substr ($oid, 0, 1));
push @oid, int ($subid / 40);
push @oid, $subid % 40;
$oid = substr ($oid, 1);
while ($oid ne '') {
$subid = ord (substr ($oid, 0, 1));
if ($subid < 128) {
$oid = substr ($oid, 1);
push @oid, $subid;
} else {
$next = $subid;
$subid = 0;
while ($next >= 128) {
$subid = ($subid << 7) + ($next & 0x7f);
$oid = substr ($oid, 1);
$next = ord (substr ($oid, 0, 1));
}
$subid = ($subid << 7) + $next;
$oid = substr ($oid, 1);
push @oid, $subid;
}
}
join ('.', @oid);
}
sub pretty_uptime ($) {
my ($packet,$uptime);
($uptime,$packet) = &decode_unsignedlike (@_);
pretty_uptime_value ($uptime);
}
sub pretty_uptime_value ($) {
my ($uptime) = @_;
my ($seconds,$minutes,$hours,$days,$result);
## We divide the uptime by hundred since we're not interested in
## sub-second precision.
$uptime = int ($uptime / 100);
$days = int ($uptime / (60 * 60 * 24));
$uptime %= (60 * 60 * 24);
$hours = int ($uptime / (60 * 60));
$uptime %= (60 * 60);
$minutes = int ($uptime / 60);
$seconds = $uptime % 60;
if ($days == 0){
$result = sprintf ("%d:%02d:%02d", $hours, $minutes, $seconds);
} elsif ($days == 1) {
$result = sprintf ("%d day, %d:%02d:%02d",
$days, $hours, $minutes, $seconds);
} else {
$result = sprintf ("%d days, %d:%02d:%02d",
$days, $hours, $minutes, $seconds);
}
return $result;
}
sub pretty_ip_address ($) {
my $pdu = shift;
my ($length, $rest);
return error ("IP Address tag (".snmp_ip_address_tag.") expected")
unless ord (substr ($pdu, 0, 1)) == snmp_ip_address_tag;
($length,$pdu) = decode_length ($pdu, 1);
return error ("Length of IP address should be four")
unless $length == 4;
sprintf "%d.%d.%d.%d", unpack ("CCCC", $pdu);
}
# IlvJa
# Returns a string with the pretty prints of all
# the elements in the sequence.
sub pretty_generic_sequence ($) {
my ($pdu) = shift;
my $rest;
my $type = ord substr ($pdu, 0 ,1);
my $flags = context_flag | constructor_flag;
return error (sprintf ("Tag 0x%x is not a valid sequence tag",$type))
unless ($type == (&constructor_flag | &sequence_tag) # sequence
|| $type == (0 | $flags) #get_request
|| $type == (1 | $flags) #getnext_request
|| $type == (2 | $flags) #response
|| $type == (3 | $flags) #set_request
|| $type == (4 | $flags) #trap_request
|| $type == (5 | $flags) #getbulk_request
|| $type == (6 | $flags) #inform_request
|| $type == (7 | $flags) #trap2_request
);
my $curelem;
my $pretty_result; # Holds the pretty printed sequence.
my $pretty_elem; # Holds the pretty printed current elem.
my $first_elem = 'true';
# Cut away the first Tag and Length from $packet and then
# init $rest with that.
(undef, $rest) = decode_length ($pdu, 1);
while($rest)
{
($curelem,$rest) = decode_generic_tlv($rest);
$pretty_elem = pretty_print($curelem);
$pretty_result .= "\n" if not $first_elem;
$pretty_result .= $pretty_elem;
# The rest of the iterations are not related to the
# first element of the sequence so..
$first_elem = '' if $first_elem;
}
return $pretty_result;
}
sub hex_string ($) {
&hex_string_of_type ($_[0], octet_string_tag);
}
sub hex_string_of_type ($$) {
my ($pdu, $wanted_type) = @_;
my ($length);
return error ("BER tag ".$wanted_type." expected")
unless ord (substr ($pdu, 0, 1)) == $wanted_type;
($length,$pdu) = decode_length ($pdu, 1);
hex_string_aux ($pdu);
}
sub hex_string_aux ($) {
my ($binary_string) = @_;
my ($c, $result);
$result = '';
for $c (unpack "C*", $binary_string) {
$result .= sprintf "%02x", $c;
}
$result;
}
sub decode_oid ($) {
my ($pdu) = @_;
my ($result,$pdu_rest);
my (@result);
$result = ord (substr ($pdu, 0, 1));
return error ("Object ID expected") unless $result == object_id_tag;
($result, $pdu_rest) = decode_length ($pdu, 1);
return error ("Short PDU")
if $result > length $pdu_rest;
@result = (substr ($pdu, 0, $result + (length ($pdu) - length ($pdu_rest))),
substr ($pdu_rest, $result));
@result;
}
# IlvJa
# This takes a PDU and returns a two element list consisting of
# the first element found in the PDU (whatever it is) and the
# rest of the PDU
sub decode_generic_tlv ($) {
my ($pdu) = @_;
my (@result);
my ($elemlength,$pdu_rest) = decode_length ($pdu, 1);
@result = (# Extract the first element.
substr ($pdu, 0, $elemlength + (length ($pdu)
- length ($pdu_rest)
)
),
#Extract the rest of the PDU.
substr ($pdu_rest, $elemlength)
);
@result;
}
sub decode_by_template {
my ($pdu) = shift;
local ($_) = shift;
return decode_by_template_2 ($pdu, $_, 0, 0, @_);
}
my $template_debug = 0;
sub decode_by_template_2 {
my ($pdu, $template, $pdu_index, $template_index);
local ($_);
$pdu = shift;
$template = $_ = shift;
$pdu_index = shift;
$template_index = shift;
my (@results);
my ($length,$expected,$read,$rest);
return undef unless defined $pdu;
while (0 < length ($_)) {
if (substr ($_, 0, 1) eq '%') {
print STDERR "template $_ ", length $pdu," bytes remaining\n"
if $template_debug;
$_ = substr ($_,1);
++$template_index;
if (($expected) = /^(\d*|\*)\{(.*)/) {
## %{
$template_index += length ($expected) + 1;
print STDERR "%{\n" if $template_debug;
$_ = $2;
$expected = shift | constructor_flag if ($expected eq '*');
$expected = sequence_tag | constructor_flag
if $expected eq '';
return template_error ("Unexpected end of PDU",
$template, $template_index)
if !defined $pdu or $pdu eq '';
return template_error ("Expected sequence tag $expected, got ".
ord (substr ($pdu, 0, 1)),
$template,
$template_index)
unless (ord (substr ($pdu, 0, 1)) == $expected);
(($length,$pdu) = decode_length ($pdu, 1))
|| return template_error ("cannot read length",
$template, $template_index);
return template_error ("Expected length $length, got ".length $pdu ,
$template, $template_index)
unless length $pdu == $length;
} elsif (($expected,$rest) = /^(\*|)s(.*)/) {
## %s
$template_index += length ($expected) + 1;
($expected = shift) if $expected eq '*';
(($read,$pdu) = decode_string ($pdu))
|| return template_error ("cannot read string",
$template, $template_index);
print STDERR "%s => $read\n" if $template_debug;
if ($expected eq '') {
push @results, $read;
} else {
return template_error ("Expected $expected, read $read",
$template, $template_index)
unless $expected eq $read;
}
$_ = $rest;
} elsif (($rest) = /^A(.*)/) {
## %A
$template_index += 1;
{
my ($tag, $length, $value);
$tag = ord (substr ($pdu, 0, 1));
return error ("Expected IP address, got tag ".$tag)
unless $tag == snmp_ip_address_tag;
($length, $pdu) = decode_length ($pdu, 1);
return error ("Inconsistent length of InetAddress encoding")
if $length > length $pdu;
return template_error ("IP address must be four bytes long",
$template, $template_index)
unless $length == 4;
$read = substr ($pdu, 0, $length);
$pdu = substr ($pdu, $length);
}
print STDERR "%A => $read\n" if $template_debug;
push @results, $read;
$_ = $rest;
} elsif (/^O(.*)/) {
## %O
$template_index += 1;
$_ = $1;
(($read,$pdu) = decode_oid ($pdu))
|| return template_error ("cannot read OID",
$template, $template_index);
print STDERR "%O => ".pretty_oid ($read)."\n"
if $template_debug;
push @results, $read;
} elsif (($expected,$rest) = /^(\d*|\*|)i(.*)/) {
## %i
$template_index += length ($expected) + 1;
print STDERR "%i\n" if $template_debug;
$_ = $rest;
(($read,$pdu) = decode_int ($pdu))
|| return template_error ("cannot read int",
$template, $template_index);
if ($expected eq '') {
push @results, $read;
} else {
$expected = int (shift) if $expected eq '*';
return template_error (sprintf ("Expected %d (0x%x), got %d (0x%x)",
$expected, $expected, $read, $read),
$template, $template_index)
unless ($expected == $read)
}
} elsif (($rest) = /^u(.*)/) {
## %u
$template_index += 1;
print STDERR "%u\n" if $template_debug;
$_ = $rest;
(($read,$pdu) = decode_unsignedlike ($pdu))
|| return template_error ("cannot read uptime",
$template, $template_index);
push @results, $read;
} elsif (/^\@(.*)/) {
## %@
$template_index += 1;
print STDERR "%@\n" if $template_debug;
$_ = $1;
push @results, $pdu;
$pdu = '';
} else {
return template_error ("Unknown decoding directive in template: $_",
$template, $template_index);
}
} else {
if (substr ($_, 0, 1) ne substr ($pdu, 0, 1)) {
return template_error ("Expected ".substr ($_, 0, 1).", got ".substr ($pdu, 0, 1),
$template, $template_index);
}
$_ = substr ($_,1);
$pdu = substr ($pdu,1);
}
}
return template_error ("PDU too long", $template, $template_index)
if length ($pdu) > 0;
return template_error ("PDU too short", $template, $template_index)
if length ($_) > 0;
@results;
}
sub decode_sequence ($) {
my ($pdu) = @_;
my ($result);
my (@result);
$result = ord (substr ($pdu, 0, 1));
return error ("Sequence expected")
unless $result == (sequence_tag | constructor_flag);
($result, $pdu) = decode_length ($pdu, 1);
return error ("Short PDU")
if $result > length $pdu;
@result = (substr ($pdu, 0, $result), substr ($pdu, $result));
@result;
}
sub decode_int ($) {
my ($pdu) = @_;
my $tag = ord (substr ($pdu, 0, 1));
return error ("Integer expected, found tag ".$tag)
unless $tag == int_tag;
decode_intlike ($pdu);
}
sub decode_intlike ($) {
decode_intlike_s ($_[0], 1);
}
sub decode_unsignedlike ($) {
decode_intlike_s ($_[0], 0);
}
my $have_math_bigint_p = 0;
sub decode_intlike_s ($$) {
my ($pdu, $signedp) = @_;
my ($length,$result);
($length,$pdu) = decode_length ($pdu, 1);
my $ptr = 0;
$result = unpack ($signedp ? "c" : "C", substr ($pdu, $ptr++, 1));
if ($length > 5 || ($length == 5 && $result > 0)) {
require 'Math/BigInt.pm' unless $have_math_bigint_p++;
$result = new Math::BigInt ($result);
}
while (--$length > 0) {
$result *= 256;
$result += unpack ("C", substr ($pdu, $ptr++, 1));
}
($result, substr ($pdu, $ptr));
}
sub decode_string ($) {
my ($pdu) = shift;
my ($result);
$result = ord (substr ($pdu, 0, 1));
return error ("Expected octet string, got tag ".$result)
unless $result == octet_string_tag;
($result, $pdu) = decode_length ($pdu, 1);
return error ("Short PDU")
if $result > length $pdu;
return (substr ($pdu, 0, $result), substr ($pdu, $result));
}
sub decode_length ($@) {
my ($pdu) = shift;
my $index = shift || 0;
my ($result);
my (@result);
$result = ord (substr ($pdu, $index, 1));
if ($result & long_length) {
if ($result == (long_length | 1)) {
@result = (ord (substr ($pdu, $index+1, 1)), substr ($pdu, $index+2));
} elsif ($result == (long_length | 2)) {
@result = ((ord (substr ($pdu, $index+1, 1)) << 8)
+ ord (substr ($pdu, $index+2, 1)), substr ($pdu, $index+3));
} else {
return error ("Unsupported length");
}
} else {
@result = ($result, substr ($pdu, $index+1));
}
@result;
}
# This takes a hashref that specifies functions to call when
# the specified value type is being printed. It returns the
# number of functions that were registered.
sub register_pretty_printer($)
{
my ($h_ref) = shift;
my ($type, $val, $cnt);
$cnt = 0;
while(($type, $val) = each %$h_ref) {
if (ref $val eq "CODE") {
$pretty_printer{$type} = $val;
$cnt++;
}
}
return($cnt);
}
# This takes a hashref that specifies functions to call when
# the specified value type is being printed. It removes the
# functions from the list for the types specified.
# It returns the number of functions that were unregistered.
sub unregister_pretty_printer($)
{
my ($h_ref) = shift;
my ($type, $val, $cnt);
$cnt = 0;
while(($type, $val) = each %$h_ref) {
if ((exists ($pretty_printer{$type}))
&& ($pretty_printer{$type} == $val)) {
if (exists($default_printer{$type})) {
$pretty_printer{$type} = $default_printer{$type};
} else {
delete $pretty_printer{$type};
}
$cnt++;
}
}
return($cnt);
}
#### OID prefix check
### encoded_oid_prefix_p OID1 OID2
###
### OID1 and OID2 should be BER-encoded OIDs.
### The function returns non-zero iff OID1 is a prefix of OID2.
### This can be used in the termination condition of a loop that walks
### a table using GetNext or GetBulk.
###
sub encoded_oid_prefix_p ($$) {
my ($oid1, $oid2) = @_;
my ($i1, $i2);
my ($l1, $l2);
my ($subid1, $subid2);
return error ("OID tag expected") unless ord (substr ($oid1, 0, 1)) == object_id_tag;
return error ("OID tag expected") unless ord (substr ($oid2, 0, 1)) == object_id_tag;
($l1,$oid1) = decode_length ($oid1, 1);
($l2,$oid2) = decode_length ($oid2, 1);
for ($i1 = 0, $i2 = 0;
$i1 < $l1 && $i2 < $l2;
++$i1, ++$i2) {
($subid1,$i1) = &decode_subid ($oid1, $i1, $l1);
($subid2,$i2) = &decode_subid ($oid2, $i2, $l2);
return 0 unless $subid1 == $subid2;
}
return $i2 if $i1 == $l1;
return 0;
}
### decode_subid OID INDEX
###
### Decodes a subid field from a BER-encoded object ID.
### Returns two values: the field, and the index of the last byte that
### was actually decoded.
###
sub decode_subid ($$$) {
my ($oid, $i, $l) = @_;
my $subid = 0;
my $next;
while (($next = ord (substr ($oid, $i, 1))) >= 128) {
$subid = ($subid << 7) + ($next & 0x7f);
++$i;
return error ("decoding object ID: short field")
unless $i < $l;
}
return (($subid << 7) + $next, $i);
}
sub error (@) {
$errmsg = join ("",@_);
return undef;
}
sub template_error ($$$) {
my ($errmsg, $template, $index) = @_;
return error ($errmsg."\n ".$template."\n ".(' ' x $index)."^");
}
1;