318 lines
12 KiB
Ruby
318 lines
12 KiB
Ruby
# -*- ruby encoding: utf-8 -*-
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module Net # :nodoc:
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##
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# == Basic Encoding Rules (BER) Support Module
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#
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# Much of the text below is cribbed from Wikipedia:
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# http://en.wikipedia.org/wiki/Basic_Encoding_Rules
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#
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# The ITU Specification is also worthwhile reading:
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# http://www.itu.int/ITU-T/studygroups/com17/languages/X.690-0207.pdf
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#
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# The Basic Encoding Rules were the original rules laid out by the ASN.1
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# standard for encoding abstract information into a concrete data stream.
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# The rules, collectively referred to as a transfer syntax in ASN.1
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# parlance, specify the exact octet sequences which are used to encode a
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# given data item. The syntax defines such elements as: the
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# representations for basic data types, the structure of length
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# information, and the means for defining complex or compound types based
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# on more primitive types. The BER syntax, along with two subsets of BER
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# (the Canonical Encoding Rules and the Distinguished Encoding Rules), are
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# defined by the ITU-T's X.690 standards document, which is part of the
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# ASN.1 document series.
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#
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# == Encoding
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# The BER format specifies a self-describing and self-delimiting format
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# for encoding ASN.1 data structures. Each data element is encoded as a
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# type identifier, a length description, the actual data elements, and
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# where necessary, an end-of-content marker. This format allows a receiver
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# to decode the ASN.1 information from an incomplete stream, without
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# requiring any pre-knowledge of the size, content, or semantic meaning of
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# the data.
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#
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# <Type | Length | Value [| End-of-Content]>
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#
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# == Protocol Data Units (PDU)
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# Protocols are defined with schema represented in BER, such that a PDU
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# consists of cascaded type-length-value encodings.
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#
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# === Type Tags
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# BER type tags are represented as single octets (bytes). The lower five
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# bits of the octet are tag identifier numbers and the upper three bits of
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# the octet are used to distinguish the type as native to ASN.1,
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# application-specific, context-specific, or private. See
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# Net::BER::TAG_CLASS and Net::BER::ENCODING_TYPE for more information.
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#
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# If Class is set to Universal (0b00______), the value is of a type native
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# to ASN.1 (e.g. INTEGER). The Application class (0b01______) is only
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# valid for one specific application. Context_specific (0b10______)
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# depends on the context and private (0b11_______) can be defined in
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# private specifications
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#
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# If the primitive/constructed bit is zero (0b__0_____), it specifies that
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# the value is primitive like an INTEGER. If it is one (0b__1_____), the
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# value is a constructed value that contains type-length-value encoded
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# types like a SET or a SEQUENCE.
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#
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# === Defined Universal (ASN.1 Native) Types
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# There are a number of pre-defined universal (native) types.
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#
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# <table>
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# <tr><th>Name</th><th>Primitive<br />Constructed</th><th>Number</th></tr>
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# <tr><th>EOC (End-of-Content)</th><th>P</th><td>0: 0 (0x0, 0b00000000)</td></tr>
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# <tr><th>BOOLEAN</th><th>P</th><td>1: 1 (0x01, 0b00000001)</td></tr>
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# <tr><th>INTEGER</th><th>P</th><td>2: 2 (0x02, 0b00000010)</td></tr>
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# <tr><th>BIT STRING</th><th>P</th><td>3: 3 (0x03, 0b00000011)</td></tr>
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# <tr><th>BIT STRING</th><th>C</th><td>3: 35 (0x23, 0b00100011)</td></tr>
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# <tr><th>OCTET STRING</th><th>P</th><td>4: 4 (0x04, 0b00000100)</td></tr>
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# <tr><th>OCTET STRING</th><th>C</th><td>4: 36 (0x24, 0b00100100)</td></tr>
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# <tr><th>NULL</th><th>P</th><td>5: 5 (0x05, 0b00000101)</td></tr>
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# <tr><th>OBJECT IDENTIFIER</th><th>P</th><td>6: 6 (0x06, 0b00000110)</td></tr>
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# <tr><th>Object Descriptor</th><th>P</th><td>7: 7 (0x07, 0b00000111)</td></tr>
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# <tr><th>EXTERNAL</th><th>C</th><td>8: 40 (0x28, 0b00101000)</td></tr>
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# <tr><th>REAL (float)</th><th>P</th><td>9: 9 (0x09, 0b00001001)</td></tr>
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# <tr><th>ENUMERATED</th><th>P</th><td>10: 10 (0x0a, 0b00001010)</td></tr>
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# <tr><th>EMBEDDED PDV</th><th>C</th><td>11: 43 (0x2b, 0b00101011)</td></tr>
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# <tr><th>UTF8String</th><th>P</th><td>12: 12 (0x0c, 0b00001100)</td></tr>
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# <tr><th>UTF8String</th><th>C</th><td>12: 44 (0x2c, 0b00101100)</td></tr>
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# <tr><th>RELATIVE-OID</th><th>P</th><td>13: 13 (0x0d, 0b00001101)</td></tr>
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# <tr><th>SEQUENCE and SEQUENCE OF</th><th>C</th><td>16: 48 (0x30, 0b00110000)</td></tr>
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# <tr><th>SET and SET OF</th><th>C</th><td>17: 49 (0x31, 0b00110001)</td></tr>
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# <tr><th>NumericString</th><th>P</th><td>18: 18 (0x12, 0b00010010)</td></tr>
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# <tr><th>NumericString</th><th>C</th><td>18: 50 (0x32, 0b00110010)</td></tr>
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# <tr><th>PrintableString</th><th>P</th><td>19: 19 (0x13, 0b00010011)</td></tr>
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# <tr><th>PrintableString</th><th>C</th><td>19: 51 (0x33, 0b00110011)</td></tr>
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# <tr><th>T61String</th><th>P</th><td>20: 20 (0x14, 0b00010100)</td></tr>
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# <tr><th>T61String</th><th>C</th><td>20: 52 (0x34, 0b00110100)</td></tr>
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# <tr><th>VideotexString</th><th>P</th><td>21: 21 (0x15, 0b00010101)</td></tr>
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# <tr><th>VideotexString</th><th>C</th><td>21: 53 (0x35, 0b00110101)</td></tr>
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# <tr><th>IA5String</th><th>P</th><td>22: 22 (0x16, 0b00010110)</td></tr>
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# <tr><th>IA5String</th><th>C</th><td>22: 54 (0x36, 0b00110110)</td></tr>
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# <tr><th>UTCTime</th><th>P</th><td>23: 23 (0x17, 0b00010111)</td></tr>
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# <tr><th>UTCTime</th><th>C</th><td>23: 55 (0x37, 0b00110111)</td></tr>
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# <tr><th>GeneralizedTime</th><th>P</th><td>24: 24 (0x18, 0b00011000)</td></tr>
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# <tr><th>GeneralizedTime</th><th>C</th><td>24: 56 (0x38, 0b00111000)</td></tr>
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# <tr><th>GraphicString</th><th>P</th><td>25: 25 (0x19, 0b00011001)</td></tr>
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# <tr><th>GraphicString</th><th>C</th><td>25: 57 (0x39, 0b00111001)</td></tr>
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# <tr><th>VisibleString</th><th>P</th><td>26: 26 (0x1a, 0b00011010)</td></tr>
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# <tr><th>VisibleString</th><th>C</th><td>26: 58 (0x3a, 0b00111010)</td></tr>
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# <tr><th>GeneralString</th><th>P</th><td>27: 27 (0x1b, 0b00011011)</td></tr>
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# <tr><th>GeneralString</th><th>C</th><td>27: 59 (0x3b, 0b00111011)</td></tr>
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# <tr><th>UniversalString</th><th>P</th><td>28: 28 (0x1c, 0b00011100)</td></tr>
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# <tr><th>UniversalString</th><th>C</th><td>28: 60 (0x3c, 0b00111100)</td></tr>
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# <tr><th>CHARACTER STRING</th><th>P</th><td>29: 29 (0x1d, 0b00011101)</td></tr>
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# <tr><th>CHARACTER STRING</th><th>C</th><td>29: 61 (0x3d, 0b00111101)</td></tr>
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# <tr><th>BMPString</th><th>P</th><td>30: 30 (0x1e, 0b00011110)</td></tr>
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# <tr><th>BMPString</th><th>C</th><td>30: 62 (0x3e, 0b00111110)</td></tr>
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# </table>
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module BER
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VERSION = '0.2.2'
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##
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# Used for BER-encoding the length and content bytes of a Fixnum integer
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# values.
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MAX_FIXNUM_SIZE = 0.size
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##
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# BER tag classes are kept in bits seven and eight of the tag type
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# octet.
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#
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# <table>
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# <tr><th>Bitmask</th><th>Definition</th></tr>
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# <tr><th><tt>0b00______</tt></th><td>Universal (ASN.1 Native) Types</td></tr>
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# <tr><th><tt>0b01______</tt></th><td>Application Types</td></tr>
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# <tr><th><tt>0b10______</tt></th><td>Context-Specific Types</td></tr>
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# <tr><th><tt>0b11______</tt></th><td>Private Types</td></tr>
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# </table>
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TAG_CLASS = {
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:universal => 0b00000000, # 0
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:application => 0b01000000, # 64
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:context_specific => 0b10000000, # 128
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:private => 0b11000000, # 192
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}
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##
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# BER encoding type is kept in bit 6 of the tag type octet.
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#
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# <table>
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# <tr><th>Bitmask</th><th>Definition</th></tr>
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# <tr><th><tt>0b__0_____</tt></th><td>Primitive</td></tr>
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# <tr><th><tt>0b__1_____</tt></th><td>Constructed</td></tr>
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# </table>
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ENCODING_TYPE = {
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:primitive => 0b00000000, # 0
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:constructed => 0b00100000, # 32
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}
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##
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# Accepts a hash of hashes describing a BER syntax and converts it into
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# a byte-keyed object for fast BER conversion lookup. The resulting
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# "compiled" syntax is used by Net::BER::BERParser.
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#
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# This method should be called only by client classes of Net::BER (e.g.,
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# Net::LDAP and Net::SNMP) and not by clients of those classes.
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#
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# The hash-based syntax uses TAG_CLASS keys that contain hashes of
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# ENCODING_TYPE keys that contain tag numbers with object type markers.
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#
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# :<TAG_CLASS> => {
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# :<ENCODING_TYPE> => {
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# <number> => <object-type>
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# },
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# },
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#
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# === Permitted Object Types
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# <tt>:string</tt>:: A string value, represented as BerIdentifiedString.
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# <tt>:integer</tt>:: An integer value, represented with Fixnum.
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# <tt>:oid</tt>:: An Object Identifier value; see X.690 section
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# 8.19. Currently represented with a standard array,
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# but may be better represented as a
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# BerIdentifiedOID object.
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# <tt>:array</tt>:: A sequence, represented as BerIdentifiedArray.
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# <tt>:boolean</tt>:: A boolean value, represented as +true+ or +false+.
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# <tt>:null</tt>:: A null value, represented as BerIdentifiedNull.
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#
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# === Example
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# Net::LDAP defines its ASN.1 BER syntax something like this:
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#
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# class Net::LDAP
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# AsnSyntax = Net::BER.compile_syntax({
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# :application => {
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# :primitive => {
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# 2 => :null,
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# },
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# :constructed => {
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# 0 => :array,
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# # ...
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# },
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# },
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# :context_specific => {
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# :primitive => {
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# 0 => :string,
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# # ...
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# },
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# :constructed => {
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# 0 => :array,
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# # ...
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# },
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# }
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# })
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# end
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#
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# NOTE:: For readability and formatting purposes, Net::LDAP and its
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# siblings actually construct their syntaxes more deliberately,
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# as shown below. Since a hash is passed in the end in any case,
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# the format does not matter.
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#
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# primitive = { 2 => :null }
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# constructed = {
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# 0 => :array,
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# # ...
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# }
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# application = {
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# :primitive => primitive,
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# :constructed => constructed
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# }
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#
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# primitive = {
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# 0 => :string,
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# # ...
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# }
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# constructed = {
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# 0 => :array,
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# # ...
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# }
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# context_specific = {
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# :primitive => primitive,
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# :constructed => constructed
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# }
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# AsnSyntax = Net::BER.compile_syntax(:application => application,
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# :context_specific => context_specific)
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def self.compile_syntax(syntax)
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# TODO 20100327 AZ: Should we be allocating an array of 256 values
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# that will either be +nil+ or an object type symbol, or should we
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# allocate an empty Hash since unknown values return +nil+ anyway?
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out = [ nil ] * 256
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syntax.each do |tag_class_id, encodings|
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tag_class = TAG_CLASS[tag_class_id]
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encodings.each do |encoding_id, classes|
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encoding = ENCODING_TYPE[encoding_id]
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object_class = tag_class + encoding
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classes.each do |number, object_type|
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out[object_class + number] = object_type
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end
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end
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end
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out
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end
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end
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end
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class Net::BER::BerError < RuntimeError; end
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##
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# An Array object with a BER identifier attached.
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class Net::BER::BerIdentifiedArray < Array
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attr_accessor :ber_identifier
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def initialize(*args)
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super
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end
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end
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##
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# A BER object identifier.
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class Net::BER::BerIdentifiedOid
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attr_accessor :ber_identifier
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def initialize(oid)
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if oid.is_a?(String)
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oid = oid.split(/\./).map {|s| s.to_i }
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end
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@value = oid
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end
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def to_ber
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to_ber_oid
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end
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def to_ber_oid
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@value.to_ber_oid
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end
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def to_s
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@value.join(".")
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end
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def to_arr
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@value.dup
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end
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end
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##
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# A String object with a BER identifier attached.
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class Net::BER::BerIdentifiedString < String
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attr_accessor :ber_identifier
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def initialize args
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super args
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# LDAP uses UTF-8 encoded strings
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force_encoding('UTF-8') if respond_to?(:encoding)
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end
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end
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module Net::BER
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##
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# A BER null object.
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class BerIdentifiedNull
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attr_accessor :ber_identifier
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def to_ber
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"\005\000"
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end
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end
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##
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# The default BerIdentifiedNull object.
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Null = Net::BER::BerIdentifiedNull.new
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end
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require 'net/ber/core_ext'
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