Library asn1

ASN.1 functions.

Large chunks of this code have been ripped right out from snmp.lua.

Author:

• Patrik Karlsson

Copyright © Same as Nmap--See https://nmap.org/book/man-legal.html

Source: https://svn.nmap.org/nmap/nselib/asn1 .lua

Functions

asn1.decoder (self, encStr, elen, pos)

Template for an ASN1 decoder function.

asn1.encoder (self, val)

Template for an ASN1 encoder function.

ASN1Decoder.decode (self, encStr, pos)

Decodes the ASN.1's built-in simple types

ASN1Decoder.decodeInt (encStr, len, pos)

Decodes an Integer according to ASN.1 basic encoding rules.

ASN1Decoder.decodeLength (encStr, pos)

Decodes length part of encoded value according to ASN.1 basic encoding rules.

ASN1Decoder.decodeOID (self, encStr, len, pos)

Decodes an OID from a sequence of bytes.

ASN1Decoder.decodeSeq (self, encStr, len, pos)

Decodes a sequence according to ASN.1 basic encoding rules.

ASN1Decoder.registerBaseDecoders (self)

Registers the base simple type decoders

ASN1Decoder.registerTagDecoders (self, tagDecoders)

Allows for registration of additional tag decoders

ASN1Decoder.registerTagEncoders (self, tagEncoders)

Allows for registration of additional tag encoders

ASN1Decoder.setStopOnError (self, val)

Tells the decoder to stop if it detects an error while decoding.

ASN1Encoder.encode (self, val)

Encodes a given value according to ASN.1 basic encoding rules for SNMP packet creation.

ASN1Encoder.encodeInt (val)

Encodes an Integer according to ASN.1 basic encoding rules.

ASN1Encoder.encodeLength (len)

Encodes the length part of a ASN.1 encoding triplet using the "primitive, definite-length" method.

ASN1Encoder.encodeSeq (self, seqData)

Encodes an ASN1 sequence

ASN1Encoder.registerBaseEncoders (self)

Registers the base ASN.1 Simple types encoders

BERtoInt (class, constructed, number)

Converts a BER encoded type to a numeric value

intToBER (i)

Converts an integer to a BER encoded type table

Tables

tagDecoders

Table for registering additional tag decoders.

tagEncoders

Table for registering additional tag encoders.

Functions

asn1.decoder (self, encStr, elen, pos)

Template for an ASN1 decoder function.

Parameters

self

The ASN1Decoder object

encStr

Encoded string

elen

Length of the object in bytes

pos

Current position in the string

Return values:

1. The decoded object
2. The position after decoding

asn1.encoder (self, val)

Template for an ASN1 encoder function.

Parameters

self

The ASN1Encoder object

val

The value to encode

Return value:

The encoded object

ASN1Decoder.decode (self, encStr, pos)

Decodes the ASN.1's built-in simple types

Parameters

self

 

encStr

Encoded string.

pos

Current position in the string.

Return values:

1. The decoded value(s).
2. The position after decoding

ASN1Decoder.decodeInt (encStr, len, pos)

Decodes an Integer according to ASN.1 basic encoding rules.

Parameters

encStr

Encoded string.

len

Length of integer in bytes.

pos

Current position in the string.

Return values:

1. The decoded integer.
2. The position after decoding.

ASN1Decoder.decodeLength (encStr, pos)

Decodes length part of encoded value according to ASN.1 basic encoding rules.

Parameters

encStr

Encoded string.

pos

Current position in the string.

Return values:

1. The length of the following value.
2. The position after decoding.

ASN1Decoder.decodeOID (self, encStr, len, pos)

Decodes an OID from a sequence of bytes.

Parameters

self

 

encStr

Encoded string.

len

Length of sequence in bytes.

pos

Current position in the string.

Return values:

1. The OID as an array.
2. The position after decoding.

ASN1Decoder.decodeSeq (self, encStr, len, pos)

Decodes a sequence according to ASN.1 basic encoding rules.

Parameters

self

 

encStr

Encoded string.

len

Length of sequence in bytes.

pos

Current position in the string.

Return values:

1. The decoded sequence as a table.
2. The position after decoding.

ASN1Decoder.registerBaseDecoders (self)

Registers the base simple type decoders

Parameters

self

 

ASN1Decoder.registerTagDecoders (self, tagDecoders)

Allows for registration of additional tag decoders

Parameters

self

 

tagDecoders

table containing decoding functions

See also:

• tagDecoders

ASN1Decoder.registerTagEncoders (self, tagEncoders)

Allows for registration of additional tag encoders

Parameters

self

 

tagEncoders

table containing encoding functions

See also:

• tagEncoders

ASN1Decoder.setStopOnError (self, val)

Tells the decoder to stop if it detects an error while decoding.

This should probably be the default, but some scripts depend on being able to decode stuff while lacking proper ASN1 decoding functions.

Parameters

self

 

val

boolean, true if decoding should stop on error, otherwise false (default)

ASN1Encoder.encode (self, val)

Encodes a given value according to ASN.1 basic encoding rules for SNMP packet creation.

Parameters

self

 

val

Value to be encoded.

Return value:

Encoded value.

ASN1Encoder.encodeInt (val)

Encodes an Integer according to ASN.1 basic encoding rules.

Parameters

val

Value to be encoded.

Return value:

Encoded integer.

ASN1Encoder.encodeLength (len)

Encodes the length part of a ASN.1 encoding triplet using the "primitive, definite-length" method.

Parameters

len

Length to be encoded.

Return value:

Encoded length value.

ASN1Encoder.encodeSeq (self, seqData)

Encodes an ASN1 sequence

Parameters

self

 

seqData

A string of sequence data

Return value:

ASN.1 BER-encoded sequence

ASN1Encoder.registerBaseEncoders (self)

Registers the base ASN.1 Simple types encoders

• boolean
• integer (Lua number)
• string
• null (Lua nil)

Parameters

self

 

BERtoInt (class, constructed, number)

Converts a BER encoded type to a numeric value

This allows it to be used in the encoding function

Parameters

class

number - see <code>BERCLASS<code>

constructed

boolean (true if constructed, false if primitive)

number

numeric

Return value:

number to be used with encode

intToBER (i)

Converts an integer to a BER encoded type table

Parameters

i

number containing the value to decode

Return value:

table with the following entries:

• class
• constructed
• primitive
• number

Tables

tagDecoders

Table for registering additional tag decoders.

Each index is a tag number as a hex string. Values are ASN1 decoder functions.

tagEncoders

Table for registering additional tag encoders.

Each index is a lua type as a string. Values are ASN1 encoder functions.