asn(n)                         ASN.1 processing                         asn(n)



______________________________________________________________________________

NAME
       asn - ASN.1 BER encoder/decoder

SYNOPSIS
       package require Tcl  8.4

       package require asn  ?0.8.4?

       ::asn::asnSequence evalue...

       ::asn::asnSequenceFromList elist

       ::asn::asnSet evalue...

       ::asn::asnSetFromList elist

       ::asn::asnApplicationConstr appNumber evalue...

       ::asn::asnApplication appNumber data

       ::asn::asnChoice appNumber evalue...

       ::asn::asnChoiceConstr appNumber evalue...

       ::asn::asnInteger number

       ::asn::asnEnumeration number

       ::asn::asnBoolean bool

       ::asn::asnContext context data

       ::asn::asnContextConstr context evalue...

       ::asn::asnObjectIdentifier idlist

       ::asn::asnUTCTime utcstring

       ::asn::asnNull

       ::asn::asnBitString string

       ::asn::asnOctetString string

       ::asn::asnNumericString string

       ::asn::asnPrintableString string

       ::asn::asnIA5String string

       ::asn::asnBMPString string

       ::asn::asnUTF8String string

       ::asn::asnString string

       ::asn::defaultStringType ?type?

       ::asn::asnPeekByte data_var byte_var

       ::asn::asnGetLength data_var length_var

       ::asn::asnGetResponse chan data_var

       ::asn::asnGetInteger data_var int_var

       ::asn::asnGetEnumeration data_var enum_var

       ::asn::asnGetOctetString data_var string_var

       ::asn::asnGetString data_var string_var ?type_var?

       ::asn::asnGetNumericString data_var string_var

       ::asn::asnGetPrintableString data_var string_var

       ::asn::asnGetIA5String data_var string_var

       ::asn::asnGetBMPString data_var string_var

       ::asn::asnGetUTF8String data_var string_var

       ::asn::asnGetUTCTime data_var utc_var

       ::asn::asnGetBitString data_var bits_var

       ::asn::asnGetObjectIdentifier data_var oid_var

       ::asn::asnGetBoolean data_var bool_var

       ::asn::asnGetNull data_var

       ::asn::asnGetSequence data_var sequence_var

       ::asn::asnGetSet data_var set_var

       ::asn::asnGetApplication data_var appNumber_var ?content_var?
       ?encodingType_var?

       ::asn::asnGetContext data_var contextNumber_var ?content_var?
       ?encodingType_var?

       ::asn::asnPeekTag data_var tag_var tagtype_var constr_var

       ::asn::asnTag tagnumber ?class? ?tagstyle?

       ::asn::asnRetag data_var newTag

_________________________________________________________________

DESCRIPTION
       The asn package provides partial de- and encoder commands for BER
       encoded ASN.1 data. It can also be used for decoding DER, which is a
       restricted subset of BER.

       ASN.1 is a standard Abstract Syntax Notation, and BER are its Basic
       Encoding Rules.

       See http://asn1.elibel.tm.fr/en/standards/index.htm for more
       information about the standard.

       Also see http://luca.ntop.org/Teaching/Appunti/asn1.html for A Layman's
       Guide to a Subset of ASN.1, BER, and DER, an RSA Laboratories Technical
       Note by Burton S. Kaliski Jr. (Revised November 1, 1993). A text
       version of this note is part of the module sources and should be read
       by any implementor.

PUBLIC API
   ENCODER
       ::asn::asnSequence evalue...
              Takes zero or more encoded values, packs them into an ASN
              sequence and returns its encoded binary form.

       ::asn::asnSequenceFromList elist
              Takes a list of encoded values, packs them into an ASN sequence
              and returns its encoded binary form.

       ::asn::asnSet evalue...
              Takes zero or more encoded values, packs them into an ASN set
              and returns its encoded binary form.

       ::asn::asnSetFromList elist
              Takes a list of encoded values, packs them into an ASN set and
              returns its encoded binary form.

       ::asn::asnApplicationConstr appNumber evalue...
              Takes zero or more encoded values, packs them into an ASN
              application construct and returns its encoded binary form.

       ::asn::asnApplication appNumber data
              Takes a single encoded value data, packs it into an ASN
              application construct and returns its encoded binary form.

       ::asn::asnChoice appNumber evalue...
              Takes zero or more encoded values, packs them into an ASN choice
              construct and returns its encoded binary form.

       ::asn::asnChoiceConstr appNumber evalue...
              Takes zero or more encoded values, packs them into an ASN choice
              construct and returns its encoded binary form.

       ::asn::asnInteger number
              Returns the encoded form of the specified integer number.

       ::asn::asnEnumeration number
              Returns the encoded form of the specified enumeration id number.

       ::asn::asnBoolean bool
              Returns the encoded form of the specified boolean value bool.

       ::asn::asnContext context data
              Takes an encoded value and packs it into a constructed value
              with application tag, the context number.

       ::asn::asnContextConstr context evalue...
              Takes zero or more encoded values and packs them into a
              constructed value with application tag, the context number.

       ::asn::asnObjectIdentifier idlist
              Takes a list of at least 2 integers describing an object
              identifier (OID) value, and returns the encoded value.

       ::asn::asnUTCTime utcstring
              Returns the encoded form of the specified UTC time string.

       ::asn::asnNull
              Returns the NULL encoding.

       ::asn::asnBitString string
              Returns the encoded form of the specified string.

       ::asn::asnOctetString string
              Returns the encoded form of the specified string.

       ::asn::asnNumericString string
              Returns the string encoded as ASN.1 NumericString. Raises an
              error if the string contains characters other than decimal
              numbers and space.

       ::asn::asnPrintableString string
              Returns the string encoding as ASN.1 PrintableString. Raises an
              error if the string contains characters which are not allowed by
              the Printable String datatype. The allowed characters are A-Z,
              a-z, 0-9, space, apostrophe, colon, parentheses, plus, minus,
              comma, period, forward slash, question mark, and the equals
              sign.

       ::asn::asnIA5String string
              Returns the string encoded as ASN.1 IA5String. Raises an error
              if the string contains any characters outside of the US-ASCII
              range.

       ::asn::asnBMPString string
              Returns the string encoded as ASN.1 Basic Multilingual Plane
              string (Which is essentialy big-endian UCS2).

       ::asn::asnUTF8String string
              Returns the string encoded as UTF8 String. Note that some legacy
              applications such as Windows CryptoAPI do not like UTF8 strings.
              Use BMPStrings if you are not sure.

       ::asn::asnString string
              Returns an encoded form of string, choosing the most restricted
              ASN.1 string type possible. If the string contains non-ASCII
              characters, then there is more than one string type which can be
              used. See ::asn::defaultStringType.

       ::asn::defaultStringType ?type?
              Selects the string type to use for the encoding of non-ASCII
              strings. Returns current default when called without argument.
              If the argument type is supplied, it should be either UTF8 or
              BMP to choose UTF8String or BMPString respectively.

   DECODER
       General notes:

       [1]    Nearly all decoder commands take two arguments. These arguments
              are variable names, except for ::asn::asnGetResponse. The first
              variable contains the encoded ASN value to decode at the
              beginning, and more, and the second variable is where the value
              is stored to. The remainder of the input after the decoded value
              is stored back into the datavariable.

       [2]    After extraction the data variable is always modified first,
              before by writing the extracted value to its variable. This
              means that if both arguments refer to the same variable, it will
              always contain the extracted value after the call, and not the
              remainder of the input.

       ::asn::asnPeekByte data_var byte_var
              Retrieve the first byte of the data, without modifing data_var.
              This can be used to check for implicit tags.

       ::asn::asnGetLength data_var length_var
              Decode the length information for a block of BER data. The tag
              has already to be removed from the data.

       ::asn::asnGetResponse chan data_var
              Reads an encoded ASN sequence from the channel chan and stores
              it into the variable named by data_var.

       ::asn::asnGetInteger data_var int_var
              Assumes that an encoded integer value is at the front of the
              data stored in the variable named data_var, extracts and stores
              it into the variable named by int_var. Additionally removes all
              bytes associated with the value from the data for further
              processing by the following decoder commands.

       ::asn::asnGetEnumeration data_var enum_var
              Assumes that an enumeration id is at the front of the data
              stored in the variable named data_var, and stores it into the
              variable named by enum_var. Additionally removes all bytes
              associated with the value from the data for further processing
              by the following decoder commands.

       ::asn::asnGetOctetString data_var string_var
              Assumes that a string is at the front of the data stored in the
              variable named data_var, and stores it into the variable named
              by string_var. Additionally removes all bytes associated with
              the value from the data for further processing by the following
              decoder commands.

       ::asn::asnGetString data_var string_var ?type_var?
              Decodes a user-readable string. This is a convenience function
              which is able to automatically distinguish all supported ASN.1
              string types and convert the input value appropriately.  See
              ::asn::asnGetPrintableString, ::asnGetIA5String, etc.  below for
              the type-specific conversion commands.

              If the optional third argument type_var is supplied, then the
              type of the incoming string is stored in the variable named by
              it.

              The function throws the error "Invalid command name
              asnGetSomeUnsupportedString" if the unsupported string type
              Unsupported is encountered. You can create the appropriate
              function "asn::asnGetSomeUnsupportedString" in your application
              if neccessary.

       ::asn::asnGetNumericString data_var string_var
              Assumes that a numeric string value is at the front of the data
              stored in the variable named data_var, and stores it into the
              variable named by string_var. Additionally removes all bytes
              associated with the value from the data for further processing
              by the following decoder commands.

       ::asn::asnGetPrintableString data_var string_var
              Assumes that a printable string value is at the front of the
              data stored in the variable named data_var, and stores it into
              the variable named by string_var. Additionally removes all bytes
              associated with the value from the data for further processing
              by the following decoder commands.

       ::asn::asnGetIA5String data_var string_var
              Assumes that a IA5 (ASCII) string value is at the front of the
              data stored in the variable named data_var, and stores it into
              the variable named by string_var. Additionally removes all bytes
              associated with the value from the data for further processing
              by the following decoder commands.

       ::asn::asnGetBMPString data_var string_var
              Assumes that a BMP (two-byte unicode) string value is at the
              front of the data stored in the variable named data_var, and
              stores it into the variable named by string_var, converting it
              into a proper Tcl string. Additionally removes all bytes
              associated with the value from the data for further processing
              by the following decoder commands.

       ::asn::asnGetUTF8String data_var string_var
              Assumes that a UTF8 string value is at the front of the data
              stored in the variable named data_var, and stores it into the
              variable named by string_var, converting it into a proper Tcl
              string.  Additionally removes all bytes associated with the
              value from the data for further processing by the following
              decoder commands.

       ::asn::asnGetUTCTime data_var utc_var
              Assumes that a UTC time value is at the front of the data stored
              in the variable named data_var, and stores it into the variable
              named by utc_var. The UTC time value is stored as a string,
              which has to be decoded with the usual clock scan commands.
              Additionally removes all bytes associated with the value from
              the data for further processing by the following decoder
              commands.

       ::asn::asnGetBitString data_var bits_var
              Assumes that a bit string value is at the front of the data
              stored in the variable named data_var, and stores it into the
              variable named by bits_var as a string containing only 0 and 1.
              Additionally removes all bytes associated with the value from
              the data for further processing by the following decoder
              commands.

       ::asn::asnGetObjectIdentifier data_var oid_var
              Assumes that a object identifier (OID) value is at the front of
              the data stored in the variable named data_var, and stores it
              into the variable named by oid_var as a list of integers.
              Additionally removes all bytes associated with the value from
              the data for further processing by the following decoder
              commands.

       ::asn::asnGetBoolean data_var bool_var
              Assumes that a boolean value is at the front of the data stored
              in the variable named data_var, and stores it into the variable
              named by bool_var. Additionally removes all bytes associated
              with the value from the data for further processing by the
              following decoder commands.

       ::asn::asnGetNull data_var
              Assumes that a NULL value is at the front of the data stored in
              the variable named data_var and removes the bytes used to encode
              it from the data.

       ::asn::asnGetSequence data_var sequence_var
              Assumes that an ASN sequence is at the front of the data stored
              in the variable named data_var, and stores it into the variable
              named by sequence_var. Additionally removes all bytes associated
              with the value from the data for further processing by the
              following decoder commands.

              The data in sequence_var is encoded binary and has to be further
              decoded according to the definition of the sequence, using the
              decoder commands here.

       ::asn::asnGetSet data_var set_var
              Assumes that an ASN set is at the front of the data stored in
              the variable named data_var, and stores it into the variable
              named by set_var. Additionally removes all bytes associated with
              the value from the data for further processing by the following
              decoder commands.

              The data in set_var is encoded binary and has to be further
              decoded according to the definition of the set, using the
              decoder commands here.

       ::asn::asnGetApplication data_var appNumber_var ?content_var?
       ?encodingType_var?
              Assumes that an ASN application construct is at the front of the
              data stored in the variable named data_var, and stores its id
              into the variable named by appNumber_var. Additionally removes
              all bytes associated with the value from the data for further
              processing by the following decoder commands.  If a content_var
              is specified, then the command places all data associated with
              it into the named variable, in the binary form which can be
              processed using the decoder commands of this package.  If a
              encodingType_var is specified, then that var is set to 1 if the
              encoding is constructed and 0 if it is primitive.

              Otherwise it is the responsibility of the caller to decode the
              remainder of the application construct based on the id retrieved
              by this command, using the decoder commands of this package.

       ::asn::asnGetContext data_var contextNumber_var ?content_var?
       ?encodingType_var?
              Assumes that an ASN context tag construct is at the front of the
              data stored in the variable named data_var, and stores its id
              into the variable named by contextNumber_var. Additionally
              removes all bytes associated with the value from the data for
              further processing by the following decoder commands.  If a
              content_var is specified, then the command places all data
              associated with it into the named variable, in the binary form
              which can be processed using the decoder commands of this
              package.  If a encodingType_var is specified, then that var is
              set to 1 if the encoding is constructed and 0 if it is
              primitive.

              Otherwise it is the responsibility of the caller to decode the
              remainder of the construct based on the id retrieved by this
              command, using the decoder commands of this package.

   HANDLING TAGS
       Working with ASN.1 you often need to decode tagged values, which use a
       tag thats different from the universal tag for a type. In those cases
       you have to replace the tag with the universal tag used for the type,
       to decode the value.  To decode a tagged value use the ::asn::asnRetag
       to change the tag to the appropriate type to use one of the decoders
       for primitive values.  To help with this the module contains three
       functions:

       ::asn::asnPeekTag data_var tag_var tagtype_var constr_var
              The ::asn::asnPeekTag command can be used to take a peek at the
              data and decode the tag value, without removing it from the
              data. The tag_var gets set to the tag number, while the
              tagtype_var gets set to the class of the tag. (Either UNIVERSAL,
              CONTEXT, APPLICATION or PRIVATE). The constr_var is set to 1 if
              the tag is for a constructed value, and to 0 for not
              constructed. It returns the length of the tag.

       ::asn::asnTag tagnumber ?class? ?tagstyle?
              The ::asn::asnTag can be used to create a tag value. The
              tagnumber gives the number of the tag, while the class gives one
              of the classes (UNIVERSAL,CONTEXT,APPLICATION or PRIVATE). The
              class may be abbreviated to just the first letter (U,C,A,P),
              default is UNIVERSAL.  The tagstyle is either C for Constructed
              encoding, or P for primitve encoding. It defaults to P. You can
              also use 1 instead of C and 0 instead of P for direct use of the
              values returned by ::asn::asnPeekTag.

       ::asn::asnRetag data_var newTag
              Replaces the tag in front of the data in data_var with newTag.
              The new Tag can be created using the ::asn::asnTag command.

EXAMPLES
       Examples for the usage of this package can be found in the
       implementation of package ldap.

BUGS, IDEAS, FEEDBACK
       This document, and the package it describes, will undoubtedly contain
       bugs and other problems.  Please report such in the category asn of the
       Tcllib SF Trackers [http://sourceforge.net/tracker/?group_id=12883].
       Please also report any ideas for enhancements you may have for either
       package and/or documentation.

KEYWORDS
       asn, ber, cer, der, internet, protocol, x.208, x.209

CATEGORY
       Networking

COPYRIGHT
       Copyright (c) 2004 Andreas Kupries <andreas_kupries@users.sourceforge.net>
       Copyright (c) 2004 Jochen Loewer <loewerj@web.de>
       Copyright (c) 2004-2011 Michael Schlenker <mic42@users.sourceforge.net>




asn                                   0.8                               asn(n)
