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Reformat and documentation update of Net::BER and Net::BER::BERParser.

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This commit is contained in:
Austin Ziegler 2010-03-27 01:57:44 -04:00
parent 28d58cd581
commit 1d3817e007
3 changed files with 472 additions and 175 deletions
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252
lib/net/ber/ber_parser.rb
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@ -1,112 +1,168 @@
require 'stringio'
module Net
module BER
module BERParser
VERSION = '0.1.0'
##
# Implements Basic Encoding Rules parsing to be mixed into types as needed.
module Net::BER::BERParser
primitive = {
1 => :boolean,
2 => :integer,
4 => :string,
5 => :null,
6 => :oid,
10 => :integer,
13 => :string # (relative OID)
}
constructed = {
16 => :array,
17 => :array
}
universal = { :primitive => primitive, :constructed => constructed }
# The order of these follows the class-codes in BER.
# Maybe this should have been a hash.
TagClasses = [:universal, :application, :context_specific, :private]
primitive = { 10 => :integer }
context = { :primitive => primitive }
BuiltinSyntax = Net::BER.compile_syntax( {
:universal => {
:primitive => {
1 => :boolean,
2 => :integer,
4 => :string,
5 => :null,
6 => :oid,
10 => :integer,
13 => :string # (relative OID)
},
:constructed => {
16 => :array,
17 => :array
}
},
:context_specific => {
:primitive => {
10 => :integer
}
}
})
# The universal, built-in ASN.1 BER syntax.
BuiltinSyntax = Net::BER.compile_syntax(:universal => universal,
:context_specific => context)
def read_ber syntax=nil
# TODO: clean this up so it works properly with partial
# packets coming from streams that don't block when
# we ask for more data (like StringIOs). At it is,
# this can throw TypeErrors and other nasties.
id = getbyte or return nil # don't trash this value, we'll use it later
##
# This is an extract of our BER object parsing to simplify our
# understanding of how we parse basic BER object types.
def parse_ber_object(syntax, id, data)
# Find the object type from either the provided syntax lookup table or
# the built-in syntax lookup table.
#
# This exceptionally clever bit of code is verrrry slow.
object_type = (syntax && syntax[id]) || BuiltinSyntax[id]
n = getbyte
lengthlength,contentlength = if n <= 127
[1,n]
else
# Replaced the inject because it profiles hot.
# j = (0...(n & 127)).inject(0) {|mem,x| mem = (mem << 8) + getc}
j = 0
read( n & 127 ).each_byte {|n1| j = (j << 8) + n1}
[1 + (n & 127), j]
end
newobj = read contentlength
# This exceptionally clever and clear bit of code is verrrry slow.
objtype = (syntax && syntax[id]) || BuiltinSyntax[id]
# == is expensive so sort this if/else so the common cases are at the top.
obj = if objtype == :string
#(newobj || "").dup
s = BerIdentifiedString.new( newobj || "" )
s.ber_identifier = id
s
elsif objtype == :integer
j = 0
newobj.each_byte {|b| j = (j << 8) + b}
j
elsif objtype == :oid
# cf X.690 pgh 8.19 for an explanation of this algorithm.
# Potentially not good enough. We may need a BerIdentifiedOid
# as a subclass of BerIdentifiedArray, to get the ber identifier
# and also a to_s method that produces the familiar dotted notation.
oid = newobj.unpack("w*")
f = oid.shift
g = if f < 40
# == is expensive so sort this so the common cases are at the top.
if object_type == :string
s = Net::BER::BerIdentifiedString.new(data || "")
s.ber_identifier = id
s
elsif object_type == :integer
j = 0
data.each_byte { |b| j = (j << 8) + b }
j
elsif object_type == :oid
# See X.690 pgh 8.19 for an explanation of this algorithm.
# This is potentially not good enough. We may need a
# BerIdentifiedOid as a subclass of BerIdentifiedArray, to
# get the ber identifier and also a to_s method that produces
# the familiar dotted notation.
oid = data.unpack("w*")
f = oid.shift
g = if f < 40
[0, f]
elsif f < 80
[1, f-40]
[1, f - 40]
else
[2, f-80] # f-80 can easily be > 80. What a weird optimization.
# f - 80 can easily be > 80. What a weird optimization.
[2, f - 80]
end
oid.unshift g.last
oid.unshift g.first
oid
elsif objtype == :array
#seq = []
seq = BerIdentifiedArray.new
seq.ber_identifier = id
sio = StringIO.new( newobj || "" )
# Interpret the subobject, but note how the loop
# is built: nil ends the loop, but false (a valid
# BER value) does not!
while (e = sio.read_ber(syntax)) != nil
seq << e
end
seq
elsif objtype == :boolean
newobj != "\000"
elsif objtype == :null
n = BerIdentifiedNull.new
n.ber_identifier = id
n
else
raise BerError, "unsupported object type: id=0x#{id.to_s(16)}"
end
obj
oid.unshift g.last
oid.unshift g.first
# Net::BER::BerIdentifiedOid.new(oid)
oid
elsif object_type == :array
seq = Net::BER::BerIdentifiedArray.new
seq.ber_identifier = id
sio = StringIO.new(data || "")
# Interpret the subobject, but note how the loop is built:
# nil ends the loop, but false (a valid BER value) does not!
while (e = sio.read_ber(syntax)) != nil
seq << e
end
seq
elsif object_type == :boolean
data != "\000"
elsif object_type == :null
n = Net::BER::BerIdentifiedNull.new
n.ber_identifier = id
n
else
raise Net::BER::BerError, "Unsupported object type: id=#{id}"
end
end
private :parse_ber_object
##
# This is an extract of how our BER object length parsing is done to
# simplify the primary call. This is defined in X.690 section 8.1.3.
#
# The BER length will either be a single byte or up to 126 bytes in
# length. There is a special case of a BER length indicating that the
# content-length is undefined and will be identified by the presence of
# two null values (0x00 0x00).
#
# <table>
# <tr>
# <th>Range</th>
# <th>Length</th>
# </tr>
# <tr>
# <th>0x00 -- 0x7f<br />0b00000000 -- 0b01111111</th>
# <td>0 - 127 bytes</td>
# </tr>
# <tr>
# <th>0x80<br />0b10000000</th>
# <td>Indeterminate (end-of-content marker required)</td>
# </tr>
# <tr>
# <th>0x81 -- 0xfe<br />0b10000001 -- 0b11111110</th>
# <td>1 - 126 bytes of length as an integer value</td>
# </tr>
# <tr>
# <th>0xff<br />0b11111111</th>
# <td>Illegal (reserved for future expansion)</td>
# </tr>
# </table>
#
#--
# This has been modified from the version that was previously inside
# #read_ber to handle both the indeterminate terminator case and the
# invalid BER length case. Because the "lengthlength" value was not used
# inside of #read_ber, we no longer return it.
def read_ber_length
n = getbyte
if n <= 0x7f
n
elsif n == 0x80
-1
elsif n == 0xff
raise Net::BER::BerError, "Invalid BER length 0xFF detected."
else
v = 0
read(n & 0x7f).each_byte do |b|
v = (v << 8) + b
end
v
end
end
private :read_ber_length
##
# Reads a BER object from the including object. Requires that #getbyte is
# implemented on the including object and that it returns a Fixnum value.
# Also requires #read(bytes) to work.
#
# This does not work with non-blocking I/O.
def read_ber(syntax = nil)
# TODO: clean this up so it works properly with partial packets coming
# from streams that don't block when we ask for more data (like
# StringIOs). At it is, this can throw TypeErrors and other nasties.
id = getbyte or return nil # don't trash this value, we'll use it later
content_length = read_ber_length
if -1 == content_length
raise Net::BER::BerError, "Indeterminite BER content length not implemented."
else
data = read(content_length)
end
parse_ber_object(syntax, id, data)
end
end