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1.1 |
=head1 NAME |
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1.4 |
Convert::BER::XS - I<very> low level BER en-/decoding |
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1.1 |
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=head1 SYNOPSIS |
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use Convert::BER::XS ':all'; |
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1.20 |
my $ber = ber_decode $buf, $Convert::BER::XS::SNMP_PROFILE |
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1.6 |
or die "unable to decode SNMP message"; |
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1.1 |
|
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1.13 |
# The above results in a data structure consisting of |
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1.29 |
# (class, tag, flags, data) |
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1.13 |
# tuples. Below is such a message, SNMPv1 trap |
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1.6 |
# with a Cisco mac change notification. |
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1.13 |
# Did you know that Cisco is in the news almost |
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1.20 |
# every week because of some backdoor password |
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1.13 |
# or other extremely stupid security bug? |
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1.3 |
|
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[ ASN_UNIVERSAL, ASN_SEQUENCE, 1, |
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[ |
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[ ASN_UNIVERSAL, ASN_INTEGER, 0, 0 ], # snmp version 1 |
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[ ASN_UNIVERSAL, 4, 0, "public" ], # community |
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1.6 |
[ ASN_CONTEXT, 4, 1, # CHOICE, constructed - trap PDU |
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1.3 |
[ |
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[ ASN_UNIVERSAL, ASN_OBJECT_IDENTIFIER, 0, "1.3.6.1.4.1.9.9.215.2" ], # enterprise oid |
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[ ASN_APPLICATION, SNMP_IPADDRESS, 0, "10.0.0.1" ], # SNMP IpAddress |
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[ ASN_UNIVERSAL, ASN_INTEGER, 0, 6 ], # generic trap |
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[ ASN_UNIVERSAL, ASN_INTEGER, 0, 1 ], # specific trap |
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[ ASN_APPLICATION, SNMP_TIMETICKS, 0, 1817903850 ], # SNMP TimeTicks |
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[ ASN_UNIVERSAL, ASN_SEQUENCE, 1, # the varbindlist |
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[ |
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[ ASN_UNIVERSAL, ASN_SEQUENCE, 1, # a single varbind, "key value" pair |
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[ |
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[ ASN_UNIVERSAL, ASN_OBJECT_IDENTIFIER, 0, "1.3.6.1.4.1.9.9.215.1.1.8.1.2.1" ], |
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[ ASN_UNIVERSAL, ASN_OCTET_STRING, 0, "...data..." # the value |
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] |
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] |
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], |
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... |
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# let's decode it a bit with some helper functions |
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my $msg = ber_is_seq $ber |
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or die "SNMP message does not start with a sequence"; |
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ber_is $msg->[0], ASN_UNIVERSAL, ASN_INTEGER, 0 |
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or die "SNMP message does not start with snmp version\n"; |
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# message is SNMP v1 or v2c? |
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if ($msg->[0][BER_DATA] == 0 || $msg->[0][BER_DATA] == 1) { |
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# message is v1 trap? |
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if (ber_is $msg->[2], ASN_CONTEXT, 4, 1) { |
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my $trap = $msg->[2][BER_DATA]; |
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# check whether trap is a cisco mac notification mac changed message |
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if ( |
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(ber_is_oid $trap->[0], "1.3.6.1.4.1.9.9.215.2") # cmnInterfaceObjects |
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and (ber_is_int $trap->[2], 6) |
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and (ber_is_int $trap->[3], 1) # mac changed msg |
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1.1 |
) { |
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... and so on |
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# finally, let's encode it again and hope it results in the same bit pattern |
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1.20 |
my $buf = ber_encode $ber, $Convert::BER::XS::SNMP_PROFILE; |
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1.1 |
=head1 DESCRIPTION |
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1.7 |
WARNING: Before release 1.0, the API is not considered stable in any way. |
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This module implements a I<very> low level BER/DER en-/decoder. |
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1.1 |
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1.20 |
It is tuned for low memory and high speed, while still maintaining some |
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1.1 |
level of user-friendlyness. |
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1.19 |
=head2 EXPORT TAGS AND CONSTANTS |
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By default this module doesn't export any symbols, but if you don't want |
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1.23 |
to break your keyboard, editor or eyesight with extremely long names, I |
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1.19 |
recommend importing the C<:all> tag. Still, you can selectively import |
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1.21 |
things. |
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1.19 |
|
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=over |
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1.21 |
=item C<:all> |
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1.19 |
|
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1.23 |
All of the below. Really. Recommended for at least first steps, or if you |
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1.19 |
don't care about a few kilobytes of wasted memory (and namespace). |
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1.21 |
=item C<:const> |
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1.19 |
|
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1.23 |
All of the strictly ASN.1-related constants defined by this module, the |
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1.19 |
same as C<:const_asn :const_index>. Notably, this does not contain |
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C<:const_ber_type> and C<:const_snmp>. |
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A good set to get everything you need to decode and match BER data would be |
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C<:decode :const>. |
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=item C<:const_index> |
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1.19 |
|
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The BER tuple array index constants: |
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1.28 |
BER_CLASS BER_TAG BER_FLAGS BER_DATA |
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1.19 |
|
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=item C<:const_asn> |
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1.23 |
ASN class values (these are C<0>, C<1>, C<2> and C<3>, respectively - |
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exactly thw two topmost bits from the identifier octet shifted 6 bits to |
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1.19 |
the right): |
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ASN_UNIVERSAL ASN_APPLICATION ASN_CONTEXT ASN_PRIVATE |
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ASN tag values (some of which are aliases, such as C<ASN_OID>). Their |
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numerical value corresponds exactly to the numbers used in BER/X.690. |
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ASN_BOOLEAN ASN_INTEGER ASN_BIT_STRING ASN_OCTET_STRING ASN_NULL ASN_OBJECT_IDENTIFIER |
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ASN_OBJECT_DESCRIPTOR ASN_OID ASN_EXTERNAL ASN_REAL ASN_SEQUENCE ASN_ENUMERATED |
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ASN_EMBEDDED_PDV ASN_UTF8_STRING ASN_RELATIVE_OID ASN_SET ASN_NUMERIC_STRING |
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ASN_PRINTABLE_STRING ASN_TELETEX_STRING ASN_T61_STRING ASN_VIDEOTEX_STRING ASN_IA5_STRING |
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ASN_ASCII_STRING ASN_UTC_TIME ASN_GENERALIZED_TIME ASN_GRAPHIC_STRING ASN_VISIBLE_STRING |
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ASN_ISO646_STRING ASN_GENERAL_STRING ASN_UNIVERSAL_STRING ASN_CHARACTER_STRING ASN_BMP_STRING |
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=item C<:const_ber_type> |
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The BER type constants, explained in the PROFILES section. |
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BER_TYPE_BYTES BER_TYPE_UTF8 BER_TYPE_UCS2 BER_TYPE_UCS4 BER_TYPE_INT |
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BER_TYPE_OID BER_TYPE_RELOID BER_TYPE_NULL BER_TYPE_BOOL BER_TYPE_REAL |
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BER_TYPE_IPADDRESS BER_TYPE_CROAK |
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=item C<:const_snmp> |
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Constants only relevant to SNMP. These are the tag values used by SNMP in |
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the C<ASN_APPLICATION> namespace and have the exact numerical value as in |
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BER/RFC 2578. |
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1.33 |
SNMP_IPADDRESS SNMP_COUNTER32 SNMP_UNSIGNED32 SNMP_GAUGE32 |
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SNMP_TIMETICKS SNMP_OPAQUE SNMP_COUNTER64 |
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1.19 |
|
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=item C<:decode> |
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C<ber_decode> and the match helper functions: |
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1.34 |
ber_decode ber-decode_prefix |
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ber_is ber_is_seq ber_is_int ber_is_oid |
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1.19 |
|
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=item C<:encode> |
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C<ber_encode> and the construction helper functions: |
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1.34 |
ber_encode |
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ber_int |
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1.19 |
|
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=back |
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1.4 |
=head2 ASN.1/BER/DER/... BASICS |
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1.15 |
ASN.1 is a strange language that can be used to describe protocols and |
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1.4 |
data structures. It supports various mappings to JSON, XML, but most |
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importantly, to a various binary encodings such as BER, that is the topic |
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1.27 |
of this module, and is used in SNMP, LDAP or X.509 for example. |
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1.4 |
|
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While ASN.1 defines a schema that is useful to interpret encoded data, |
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1.12 |
the BER encoding is actually somewhat self-describing: you might not know |
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1.4 |
whether something is a string or a number or a sequence or something else, |
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but you can nevertheless decode the overall structure, even if you end up |
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with just a binary blob for the actual value. |
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This works because BER values are tagged with a type and a namespace, |
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1.15 |
and also have a flag that says whether a value consists of subvalues (is |
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1.4 |
"constructed") or not (is "primitive"). |
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1.25 |
Tags are simple integers, and ASN.1 defines a somewhat weird assortment |
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of those - for example, you have one integers and 16(!) different |
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1.23 |
string types, but there is no Unsigned32 type for example. Different |
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1.4 |
applications work around this in different ways, for example, SNMP defines |
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application-specific Gauge32, Counter32 and Unsigned32, which are mapped |
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to two different tags: you can distinguish between Counter32 and the |
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others, but not between Gause32 and Unsigned32, without the ASN.1 schema. |
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Ugh. |
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=head2 DECODED BER REPRESENTATION |
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This module represents every BER value as a 4-element tuple (actually an |
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array-reference): |
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1.28 |
[CLASS, TAG, FLAGS, DATA] |
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1.4 |
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1.23 |
For example: |
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1.25 |
[ASN_UNIVERSAL, ASN_INTEGER, 0, 177] # the integer 177 |
195 |
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1.23 |
[ASN_UNIVERSAL, ASN_OCTET_STRING, 0, "john"] # the string "john" |
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[ASN_UNIVERSAL, ASN_OID, 0, "1.3.6.133"] # some OID |
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1.24 |
[ASN_UNIVERSAL, ASN_SEQUENCE, 1, [ [ASN_UNIVERSAL... # a sequence |
198 |
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1.23 |
|
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1.6 |
To avoid non-descriptive hardcoded array index numbers, this module |
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defines symbolic constants to access these members: C<BER_CLASS>, |
201 |
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1.28 |
C<BER_TAG>, C<BER_FLAGS> and C<BER_DATA>. |
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1.6 |
|
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Also, the first three members are integers with a little caveat: for |
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performance reasons, these are readonly and shared, so you must not modify |
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them (increment, assign to them etc.) in any way. You may modify the |
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I<DATA> member, and you may re-assign the array itself, e.g.: |
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$ber = ber_decode $binbuf; |
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# the following is NOT legal: |
211 |
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1.28 |
$ber->[BER_CLASS] = ASN_PRIVATE; # ERROR, CLASS/TAG/FLAGS are READ ONLY(!) |
212 |
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1.6 |
|
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# but all of the following are fine: |
214 |
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$ber->[BER_DATA] = "string"; |
215 |
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1.25 |
$ber->[BER_DATA] = [ASN_UNIVERSAL, ASN_INTEGER, 0, 123]; |
216 |
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1.11 |
@$ber = (ASN_APPLICATION, SNMP_TIMETICKS, 0, 1000); |
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1.6 |
|
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1.4 |
I<CLASS> is something like a namespace for I<TAG>s - there is the |
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C<ASN_UNIVERSAL> namespace which defines tags common to all ASN.1 |
220 |
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implementations, the C<ASN_APPLICATION> namespace which defines tags for |
221 |
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specific applications (for example, the SNMP C<Unsigned32> type is in this |
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namespace), a special-purpose context namespace (C<ASN_CONTEXT>, used e.g. |
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for C<CHOICE>) and a private namespace (C<ASN_PRIVATE>). |
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The meaning of the I<TAG> depends on the namespace, and defines a |
226 |
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1.24 |
(partial) interpretation of the data value. For example, SNMP defines |
227 |
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extra tags in the C<ASN_APPLICATION> namespace, and to take full advantage |
228 |
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of these, you need to tell this module how to handle those via profiles. |
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1.4 |
|
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The most common tags in the C<ASN_UNIVERSAL> namespace are |
231 |
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1.25 |
C<ASN_INTEGER>, C<ASN_BIT_STRING>, C<ASN_NULL>, C<ASN_OCTET_STRING>, |
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1.4 |
C<ASN_OBJECT_IDENTIFIER>, C<ASN_SEQUENCE>, C<ASN_SET> and |
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C<ASN_IA5_STRING>. |
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1.24 |
The most common tags in SNMP's C<ASN_APPLICATION> namespace are |
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C<SNMP_COUNTER32>, C<SNMP_UNSIGNED32>, C<SNMP_TIMETICKS> and |
237 |
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C<SNMP_COUNTER64>. |
238 |
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1.4 |
|
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1.28 |
The I<FLAGS> value is really just a boolean at this time (but might |
240 |
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get extended) - if it is C<0>, the value is "primitive" and contains |
241 |
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no subvalues, kind of like a non-reference perl scalar. If it is C<1>, |
242 |
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then the value is "constructed" which just means it contains a list of |
243 |
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subvalues which this module will en-/decode as BER tuples themselves. |
244 |
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245 |
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The I<DATA> value is either a reference to an array of further tuples |
246 |
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(if the value is I<FLAGS>), some decoded representation of the value, if |
247 |
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this module knows how to decode it (e.g. for the integer types above) or |
248 |
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a binary string with the raw octets if this module doesn't know how to |
249 |
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1.4 |
interpret the namespace/tag. |
250 |
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251 |
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Thus, you can always decode a BER data structure and at worst you get a |
252 |
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string in place of some nice decoded value. |
253 |
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254 |
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See the SYNOPSIS for an example of such an encoded tuple representation. |
255 |
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256 |
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1.7 |
=head2 DECODING AND ENCODING |
257 |
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258 |
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=over |
259 |
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260 |
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1.34 |
=item $tuple = ber_decode $bindata[, $profile] |
261 |
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1.7 |
|
262 |
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Decodes binary BER data in C<$bindata> and returns the resulting BER |
263 |
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tuple. Croaks on any decoding error, so the returned C<$tuple> is always |
264 |
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valid. |
265 |
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266 |
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1.24 |
How tags are interpreted is defined by the second argument, which must |
267 |
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be a C<Convert::BER::XS::Profile> object. If it is missing, the default |
268 |
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profile will be used (C<$Convert::BER::XS::DEFAULT_PROFILE>). |
269 |
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In addition to rolling your own, this module provides a |
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C<$Convert::BER::XS::SNMP_PROFILE> that knows about the additional SNMP |
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types. |
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1.7 |
|
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1.25 |
Example: decode a BER blob using the default profile - SNMP values will be |
275 |
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decided as raw strings. |
276 |
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$tuple = ber_decode $data; |
278 |
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Example: as above, but use the provided SNMP profile. |
280 |
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$tuple = ber_encode $data, $Convert::BER::XS::SNMP_PROFILE; |
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1.34 |
=item ($tuple, $bytes) = ber_decode_prefix $bindata[, $profile] |
284 |
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285 |
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Works like C<ber_decode>, except it doesn't croak when there is data after |
286 |
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the BER data, but instead returns the decoded value and the number of |
287 |
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bytes it decoded. |
288 |
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289 |
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This is useful when you have BER data at the start of a buffer and other |
290 |
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data after, and you need to find the length. |
291 |
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292 |
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Also, since BER is self-delimited, this can be used to decode multiple BER |
293 |
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values joined together. |
294 |
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1.24 |
=item $bindata = ber_encode $tuple[, $profile] |
296 |
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297 |
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Encodes the BER tuple into a BER/DER data structure. AS with |
298 |
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Cyber_decode>, an optional profile can be given. |
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1.7 |
|
300 |
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1.28 |
The encoded data should be both BER and DER ("shortest form") compliant |
301 |
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unless the input says otherwise (e.g. it uses constructed strings). |
302 |
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|
303 |
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1.7 |
=back |
304 |
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|
305 |
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1.6 |
=head2 HELPER FUNCTIONS |
306 |
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|
307 |
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Working with a 4-tuple for every value can be annoying. Or, rather, I<is> |
308 |
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annoying. To reduce this a bit, this module defines a number of helper |
309 |
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1.24 |
functions, both to match BER tuples and to construct BER tuples: |
310 |
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1.6 |
|
311 |
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=head3 MATCH HELPERS |
312 |
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|
313 |
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1.24 |
These functions accept a BER tuple as first argument and either partially |
314 |
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1.6 |
or fully match it. They often come in two forms, one which exactly matches |
315 |
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a value, and one which only matches the type and returns the value. |
316 |
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|
317 |
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They do check whether valid tuples are passed in and croak otherwise. As |
318 |
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a ease-of-use exception, they usually also accept C<undef> instead of a |
319 |
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1.24 |
tuple reference, in which case they silently fail to match. |
320 |
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1.6 |
|
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=over |
322 |
|
|
|
323 |
root |
1.29 |
=item $bool = ber_is $tuple, $class, $tag, $flags, $data |
324 |
root |
1.6 |
|
325 |
root |
1.24 |
This takes a BER C<$tuple> and matches its elements against the provided |
326 |
root |
1.6 |
values, all of which are optional - values that are either missing or |
327 |
|
|
C<undef> will be ignored, the others will be matched exactly (e.g. as if |
328 |
|
|
you used C<==> or C<eq> (for C<$data>)). |
329 |
|
|
|
330 |
|
|
Some examples: |
331 |
|
|
|
332 |
|
|
ber_is $tuple, ASN_UNIVERSAL, ASN_SEQUENCE, 1 |
333 |
|
|
orf die "tuple is not an ASN SEQUENCE"; |
334 |
|
|
|
335 |
|
|
ber_is $tuple, ASN_UNIVERSAL, ASN_NULL |
336 |
|
|
or die "tuple is not an ASN NULL value"; |
337 |
|
|
|
338 |
root |
1.25 |
ber_is $tuple, ASN_UNIVERSAL, ASN_INTEGER, 0, 50 |
339 |
root |
1.6 |
or die "BER integer must be 50"; |
340 |
|
|
|
341 |
|
|
=item $seq = ber_is_seq $tuple |
342 |
|
|
|
343 |
|
|
Returns the sequence members (the array of subvalues) if the C<$tuple> is |
344 |
|
|
an ASN SEQUENCE, i.e. the C<BER_DATA> member. If the C<$tuple> is not a |
345 |
|
|
sequence it returns C<undef>. For example, SNMP version 1/2c/3 packets all |
346 |
|
|
consist of an outer SEQUENCE value: |
347 |
|
|
|
348 |
|
|
my $ber = ber_decode $snmp_data; |
349 |
|
|
|
350 |
|
|
my $snmp = ber_is_seq $ber |
351 |
|
|
or die "SNMP packet invalid: does not start with SEQUENCE"; |
352 |
|
|
|
353 |
|
|
# now we know $snmp is a sequence, so decode the SNMP version |
354 |
|
|
|
355 |
root |
1.25 |
my $version = ber_is_int $snmp->[0] |
356 |
root |
1.6 |
or die "SNMP packet invalid: does not start with version number"; |
357 |
|
|
|
358 |
root |
1.25 |
=item $bool = ber_is_int $tuple, $int |
359 |
root |
1.6 |
|
360 |
root |
1.25 |
Returns a true value if the C<$tuple> represents an ASN INTEGER with |
361 |
|
|
the value C<$int>. |
362 |
root |
1.6 |
|
363 |
root |
1.25 |
=item $int = ber_is_int $tuple |
364 |
root |
1.6 |
|
365 |
root |
1.25 |
Returns true (and extracts the integer value) if the C<$tuple> is an |
366 |
|
|
C<ASN_INTEGER>. For C<0>, this function returns a special value that is 0 |
367 |
|
|
but true. |
368 |
root |
1.6 |
|
369 |
|
|
=item $bool = ber_is_oid $tuple, $oid_string |
370 |
|
|
|
371 |
|
|
Returns true if the C<$tuple> represents an ASN_OBJECT_IDENTIFIER |
372 |
root |
1.12 |
that exactly matches C<$oid_string>. Example: |
373 |
root |
1.6 |
|
374 |
|
|
ber_is_oid $tuple, "1.3.6.1.4" |
375 |
|
|
or die "oid must be 1.3.6.1.4"; |
376 |
|
|
|
377 |
|
|
=item $oid = ber_is_oid $tuple |
378 |
|
|
|
379 |
|
|
Returns true (and extracts the OID string) if the C<$tuple> is an ASN |
380 |
|
|
OBJECT IDENTIFIER. Otherwise, it returns C<undef>. |
381 |
|
|
|
382 |
|
|
=back |
383 |
|
|
|
384 |
|
|
=head3 CONSTRUCTION HELPERS |
385 |
|
|
|
386 |
|
|
=over |
387 |
|
|
|
388 |
root |
1.25 |
=item $tuple = ber_int $value |
389 |
root |
1.6 |
|
390 |
root |
1.25 |
Constructs a new C<ASN_INTEGER> tuple. |
391 |
root |
1.6 |
|
392 |
|
|
=back |
393 |
|
|
|
394 |
root |
1.2 |
=head2 RELATIONSHIP TO L<Convert::BER> and L<Convert::ASN1> |
395 |
|
|
|
396 |
|
|
This module is I<not> the XS version of L<Convert::BER>, but a different |
397 |
|
|
take at doing the same thing. I imagine this module would be a good base |
398 |
root |
1.4 |
for speeding up either of these, or write a similar module, or write your |
399 |
root |
1.2 |
own LDAP or SNMP module for example. |
400 |
|
|
|
401 |
root |
1.1 |
=cut |
402 |
|
|
|
403 |
|
|
package Convert::BER::XS; |
404 |
|
|
|
405 |
|
|
use common::sense; |
406 |
|
|
|
407 |
|
|
use XSLoader (); |
408 |
|
|
use Exporter qw(import); |
409 |
|
|
|
410 |
root |
1.13 |
our $VERSION; |
411 |
root |
1.1 |
|
412 |
root |
1.13 |
BEGIN { |
413 |
root |
1.35 |
$VERSION = '1.0'; |
414 |
root |
1.13 |
XSLoader::load __PACKAGE__, $VERSION; |
415 |
|
|
} |
416 |
root |
1.1 |
|
417 |
|
|
our %EXPORT_TAGS = ( |
418 |
root |
1.19 |
const_index => [qw( |
419 |
root |
1.28 |
BER_CLASS BER_TAG BER_FLAGS BER_DATA |
420 |
root |
1.19 |
)], |
421 |
|
|
const_asn => [qw( |
422 |
root |
1.25 |
ASN_BOOLEAN ASN_INTEGER ASN_BIT_STRING ASN_OCTET_STRING ASN_NULL ASN_OBJECT_IDENTIFIER |
423 |
root |
1.13 |
ASN_OBJECT_DESCRIPTOR ASN_OID ASN_EXTERNAL ASN_REAL ASN_SEQUENCE ASN_ENUMERATED |
424 |
|
|
ASN_EMBEDDED_PDV ASN_UTF8_STRING ASN_RELATIVE_OID ASN_SET ASN_NUMERIC_STRING |
425 |
|
|
ASN_PRINTABLE_STRING ASN_TELETEX_STRING ASN_T61_STRING ASN_VIDEOTEX_STRING ASN_IA5_STRING |
426 |
|
|
ASN_ASCII_STRING ASN_UTC_TIME ASN_GENERALIZED_TIME ASN_GRAPHIC_STRING ASN_VISIBLE_STRING |
427 |
|
|
ASN_ISO646_STRING ASN_GENERAL_STRING ASN_UNIVERSAL_STRING ASN_CHARACTER_STRING ASN_BMP_STRING |
428 |
|
|
|
429 |
|
|
ASN_UNIVERSAL ASN_APPLICATION ASN_CONTEXT ASN_PRIVATE |
430 |
root |
1.19 |
)], |
431 |
|
|
const_ber_type => [qw( |
432 |
root |
1.13 |
BER_TYPE_BYTES BER_TYPE_UTF8 BER_TYPE_UCS2 BER_TYPE_UCS4 BER_TYPE_INT |
433 |
|
|
BER_TYPE_OID BER_TYPE_RELOID BER_TYPE_NULL BER_TYPE_BOOL BER_TYPE_REAL |
434 |
|
|
BER_TYPE_IPADDRESS BER_TYPE_CROAK |
435 |
|
|
)], |
436 |
|
|
const_snmp => [qw( |
437 |
root |
1.33 |
SNMP_IPADDRESS SNMP_COUNTER32 SNMP_GAUGE32 SNMP_UNSIGNED32 |
438 |
|
|
SNMP_TIMETICKS SNMP_OPAQUE SNMP_COUNTER64 |
439 |
root |
1.4 |
)], |
440 |
root |
1.19 |
decode => [qw( |
441 |
root |
1.34 |
ber_decode ber_decode_prefix |
442 |
root |
1.25 |
ber_is ber_is_seq ber_is_int ber_is_oid |
443 |
root |
1.4 |
)], |
444 |
root |
1.19 |
encode => [qw( |
445 |
root |
1.4 |
ber_encode |
446 |
root |
1.25 |
ber_int |
447 |
root |
1.1 |
)], |
448 |
|
|
); |
449 |
|
|
|
450 |
|
|
our @EXPORT_OK = map @$_, values %EXPORT_TAGS; |
451 |
|
|
|
452 |
root |
1.4 |
$EXPORT_TAGS{all} = \@EXPORT_OK; |
453 |
root |
1.19 |
$EXPORT_TAGS{const} = [map @{ $EXPORT_TAGS{$_} }, qw(const_index const_asn)]; |
454 |
root |
1.4 |
|
455 |
root |
1.13 |
=head1 PROFILES |
456 |
|
|
|
457 |
|
|
While any BER data can be correctly encoded and decoded out of the box, it |
458 |
|
|
can be inconvenient to have to manually decode some values into a "better" |
459 |
|
|
format: for instance, SNMP TimeTicks values are decoded into the raw octet |
460 |
|
|
strings of their BER representation, which is quite hard to decode. With |
461 |
|
|
profiles, you can change which class/tag combinations map to which decoder |
462 |
|
|
function inside C<ber_decode> (and of course also which encoder functions |
463 |
|
|
are used in C<ber_encode>). |
464 |
|
|
|
465 |
|
|
This works by mapping specific class/tag combinations to an internal "ber |
466 |
|
|
type". |
467 |
|
|
|
468 |
|
|
The default profile supports the standard ASN.1 types, but no |
469 |
|
|
application-specific ones. This means that class/tag combinations not in |
470 |
|
|
the base set of ASN.1 are decoded into their raw octet strings. |
471 |
|
|
|
472 |
root |
1.15 |
C<Convert::BER::XS> defines two profile variables you can use out of the box: |
473 |
root |
1.13 |
|
474 |
|
|
=over |
475 |
|
|
|
476 |
|
|
=item C<$Convert::BER::XS::DEFAULT_PROFILE> |
477 |
|
|
|
478 |
|
|
This is the default profile, i.e. the profile that is used when no |
479 |
|
|
profile is specified for de-/encoding. |
480 |
|
|
|
481 |
root |
1.15 |
You can modify it, but remember that this modifies the defaults for all |
482 |
|
|
callers that rely on the default profile. |
483 |
root |
1.13 |
|
484 |
|
|
=item C<$Convert::BER::XS::SNMP_PROFILE> |
485 |
|
|
|
486 |
|
|
A profile with mappings for SNMP-specific application tags added. This is |
487 |
|
|
useful when de-/encoding SNMP data. |
488 |
|
|
|
489 |
|
|
Example: |
490 |
root |
1.15 |
|
491 |
root |
1.13 |
$ber = ber_decode $data, $Convert::BER::XS::SNMP_PROFILE; |
492 |
|
|
|
493 |
|
|
=back |
494 |
|
|
|
495 |
|
|
=head2 The Convert::BER::XS::Profile class |
496 |
|
|
|
497 |
|
|
=over |
498 |
|
|
|
499 |
|
|
=item $profile = new Convert::BER::XS::Profile |
500 |
|
|
|
501 |
|
|
Create a new profile. The profile will be identical to the default |
502 |
|
|
profile. |
503 |
|
|
|
504 |
|
|
=item $profile->set ($class, $tag, $type) |
505 |
|
|
|
506 |
|
|
Sets the mapping for the given C<$class>/C<$tag> combination to C<$type>, |
507 |
|
|
which must be one of the C<BER_TYPE_*> constants. |
508 |
|
|
|
509 |
|
|
Note that currently, the mapping is stored in a flat array, so large |
510 |
|
|
values of C<$tag> will consume large amounts of memory. |
511 |
|
|
|
512 |
|
|
Example: |
513 |
root |
1.15 |
|
514 |
root |
1.13 |
$profile = new Convert::BER::XS::Profile; |
515 |
|
|
$profile->set (ASN_APPLICATION, SNMP_COUNTER32, BER_TYPE_INT); |
516 |
|
|
$ber = ber_decode $data, $profile; |
517 |
|
|
|
518 |
|
|
=item $type = $profile->get ($class, $tag) |
519 |
|
|
|
520 |
|
|
Returns the BER type mapped to the given C<$class>/C<$tag> combination. |
521 |
|
|
|
522 |
|
|
=back |
523 |
|
|
|
524 |
|
|
=head2 BER TYPES |
525 |
|
|
|
526 |
|
|
This lists the predefined BER types - you can map any C<CLASS>/C<TAG> |
527 |
|
|
combination to any C<BER_TYPE_*>. |
528 |
|
|
|
529 |
|
|
=over |
530 |
|
|
|
531 |
|
|
=item C<BER_TYPE_BYTES> |
532 |
|
|
|
533 |
|
|
The raw octets of the value. This is the default type for unknown tags and |
534 |
|
|
de-/encodes the value as if it were an octet string, i.e. by copying the |
535 |
|
|
raw bytes. |
536 |
|
|
|
537 |
|
|
=item C<BER_TYPE_UTF8> |
538 |
|
|
|
539 |
|
|
Like C<BER_TYPE_BYTES>, but decodes the value as if it were a UTF-8 string |
540 |
|
|
(without validation!) and encodes a perl unicode string into a UTF-8 BER |
541 |
|
|
string. |
542 |
|
|
|
543 |
|
|
=item C<BER_TYPE_UCS2> |
544 |
|
|
|
545 |
|
|
Similar to C<BER_TYPE_UTF8>, but treats the BER value as UCS-2 encoded |
546 |
root |
1.14 |
string. |
547 |
root |
1.13 |
|
548 |
|
|
=item C<BER_TYPE_UCS4> |
549 |
|
|
|
550 |
|
|
Similar to C<BER_TYPE_UTF8>, but treats the BER value as UCS-4 encoded |
551 |
root |
1.14 |
string. |
552 |
root |
1.13 |
|
553 |
|
|
=item C<BER_TYPE_INT> |
554 |
|
|
|
555 |
|
|
Encodes and decodes a BER integer value to a perl integer scalar. This |
556 |
|
|
should correctly handle 64 bit signed and unsigned values. |
557 |
|
|
|
558 |
|
|
=item C<BER_TYPE_OID> |
559 |
|
|
|
560 |
|
|
Encodes and decodes an OBJECT IDENTIFIER into dotted form without leading |
561 |
|
|
dot, e.g. C<1.3.6.1.213>. |
562 |
|
|
|
563 |
|
|
=item C<BER_TYPE_RELOID> |
564 |
|
|
|
565 |
root |
1.15 |
Same as C<BER_TYPE_OID> but uses relative object identifier |
566 |
|
|
encoding: ASN.1 has this hack of encoding the first two OID components |
567 |
|
|
into a single integer in a weird attempt to save an insignificant amount |
568 |
|
|
of space in an otherwise wasteful encoding, and relative OIDs are |
569 |
|
|
basically OIDs without this hack. The practical difference is that the |
570 |
|
|
second component of an OID can only have the values 1..40, while relative |
571 |
|
|
OIDs do not have this restriction. |
572 |
root |
1.13 |
|
573 |
|
|
=item C<BER_TYPE_NULL> |
574 |
|
|
|
575 |
|
|
Decodes an C<ASN_NULL> value into C<undef>, and always encodes a |
576 |
|
|
C<ASN_NULL> type, regardless of the perl value. |
577 |
|
|
|
578 |
|
|
=item C<BER_TYPE_BOOL> |
579 |
|
|
|
580 |
|
|
Decodes an C<ASN_BOOLEAN> value into C<0> or C<1>, and encodes a perl |
581 |
|
|
boolean value into an C<ASN_BOOLEAN>. |
582 |
|
|
|
583 |
|
|
=item C<BER_TYPE_REAL> |
584 |
|
|
|
585 |
|
|
Decodes/encodes a BER real value. NOT IMPLEMENTED. |
586 |
|
|
|
587 |
|
|
=item C<BER_TYPE_IPADDRESS> |
588 |
|
|
|
589 |
root |
1.15 |
Decodes/encodes a four byte string into an IPv4 dotted-quad address string |
590 |
|
|
in Perl. Given the obsolete nature of this type, this is a low-effort |
591 |
root |
1.13 |
implementation that simply uses C<sprintf> and C<sscanf>-style conversion, |
592 |
root |
1.15 |
so it won't handle all string forms supported by C<inet_aton> for example. |
593 |
root |
1.13 |
|
594 |
|
|
=item C<BER_TYPE_CROAK> |
595 |
|
|
|
596 |
|
|
Always croaks when encountered during encoding or decoding - the |
597 |
|
|
default behaviour when encountering an unknown type is to treat it as |
598 |
|
|
C<BER_TYPE_BYTES>. When you don't want that but instead prefer a hard |
599 |
root |
1.16 |
error for some types, then C<BER_TYPE_CROAK> is for you. |
600 |
root |
1.13 |
|
601 |
|
|
=back |
602 |
|
|
|
603 |
root |
1.30 |
=head2 Example Profile |
604 |
|
|
|
605 |
|
|
The following creates a profile suitable for SNMP - it's exactly identical |
606 |
|
|
to the C<$Convert::BER::XS::SNMP_PROFILE> profile. |
607 |
|
|
|
608 |
|
|
our $SNMP_PROFILE = new Convert::BER::XS::Profile; |
609 |
|
|
|
610 |
|
|
$SNMP_PROFILE->set (ASN_APPLICATION, SNMP_IPADDRESS , BER_TYPE_IPADDRESS); |
611 |
|
|
$SNMP_PROFILE->set (ASN_APPLICATION, SNMP_COUNTER32 , BER_TYPE_INT); |
612 |
|
|
$SNMP_PROFILE->set (ASN_APPLICATION, SNMP_UNSIGNED32, BER_TYPE_INT); |
613 |
|
|
$SNMP_PROFILE->set (ASN_APPLICATION, SNMP_TIMETICKS , BER_TYPE_INT); |
614 |
|
|
$SNMP_PROFILE->set (ASN_APPLICATION, SNMP_OPAQUE , BER_TYPE_IPADDRESS); |
615 |
|
|
$SNMP_PROFILE->set (ASN_APPLICATION, SNMP_COUNTER64 , BER_TYPE_INT); |
616 |
|
|
|
617 |
root |
1.13 |
=cut |
618 |
|
|
|
619 |
|
|
our $DEFAULT_PROFILE = new Convert::BER::XS::Profile; |
620 |
root |
1.30 |
|
621 |
|
|
$DEFAULT_PROFILE->_set_default; |
622 |
root |
1.13 |
|
623 |
root |
1.19 |
# additional SNMP application types |
624 |
root |
1.30 |
our $SNMP_PROFILE = new Convert::BER::XS::Profile; |
625 |
root |
1.31 |
|
626 |
root |
1.13 |
$SNMP_PROFILE->set (ASN_APPLICATION, SNMP_IPADDRESS , BER_TYPE_IPADDRESS); |
627 |
|
|
$SNMP_PROFILE->set (ASN_APPLICATION, SNMP_COUNTER32 , BER_TYPE_INT); |
628 |
|
|
$SNMP_PROFILE->set (ASN_APPLICATION, SNMP_UNSIGNED32, BER_TYPE_INT); |
629 |
|
|
$SNMP_PROFILE->set (ASN_APPLICATION, SNMP_TIMETICKS , BER_TYPE_INT); |
630 |
|
|
$SNMP_PROFILE->set (ASN_APPLICATION, SNMP_OPAQUE , BER_TYPE_IPADDRESS); |
631 |
|
|
$SNMP_PROFILE->set (ASN_APPLICATION, SNMP_COUNTER64 , BER_TYPE_INT); |
632 |
|
|
|
633 |
root |
1.1 |
1; |
634 |
|
|
|
635 |
root |
1.19 |
=head2 LIMITATIONS/NOTES |
636 |
root |
1.13 |
|
637 |
|
|
This module can only en-/decode 64 bit signed and unsigned integers, and |
638 |
|
|
only when your perl supports those. |
639 |
root |
1.4 |
|
640 |
root |
1.19 |
This module does not generally care about ranges, i.e. it will happily |
641 |
root |
1.25 |
de-/encode 64 bit integers into an C<ASN_INTEGER> value, or a negative |
642 |
root |
1.19 |
number into an C<SNMP_COUNTER64>. |
643 |
|
|
|
644 |
root |
1.16 |
OBJECT IDENTIFIEERs cannot have unlimited length, although the limit is |
645 |
root |
1.19 |
much larger than e.g. the one imposed by SNMP or other protocols,a nd is |
646 |
|
|
about 4kB. |
647 |
root |
1.4 |
|
648 |
root |
1.28 |
Indefinite length encoding is not supported. |
649 |
|
|
|
650 |
|
|
Constructed strings are decoded just fine, but there should be a way to |
651 |
|
|
join them for convenience. |
652 |
|
|
|
653 |
root |
1.19 |
REAL values are not supported and will currently croak. |
654 |
root |
1.14 |
|
655 |
root |
1.32 |
The encoder and decoder tend to accept more formats than should be |
656 |
|
|
strictly supported. |
657 |
|
|
|
658 |
root |
1.14 |
This module has undergone little to no testing so far. |
659 |
|
|
|
660 |
root |
1.17 |
=head2 ITHREADS SUPPORT |
661 |
|
|
|
662 |
|
|
This module is unlikely to work when the (officially discouraged) ithreads |
663 |
|
|
are in use. |
664 |
|
|
|
665 |
root |
1.1 |
=head1 AUTHOR |
666 |
|
|
|
667 |
|
|
Marc Lehmann <schmorp@schmorp.de> |
668 |
|
|
http://software.schmorp.de/pkg/Convert-BER-XS |
669 |
|
|
|
670 |
|
|
=cut |
671 |
|
|
|