asn -
ASN.1 BER encoder/decoder
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
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.
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::asn::asnSequence evalue...
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Takes zero or more encoded values, packs them into an ASN sequence and
returns its encoded binary form.
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::asn::asnSequenceFromList elist
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Takes a list of encoded values, packs them into an ASN sequence and
returns its encoded binary form.
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::asn::asnSet evalue...
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Takes zero or more encoded values, packs them into an ASN set and
returns its encoded binary form.
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::asn::asnSetFromList elist
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Takes a list of encoded values, packs them into an ASN set and
returns its encoded binary form.
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::asn::asnApplicationConstr appNumber evalue...
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Takes zero or more encoded values, packs them into an ASN application
construct and returns its encoded binary form.
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::asn::asnApplication appNumber data
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Takes a single encoded value data, packs it into an ASN
application construct and returns its encoded binary form.
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::asn::asnChoice appNumber evalue...
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Takes zero or more encoded values, packs them into an ASN choice
construct and returns its encoded binary form.
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::asn::asnChoiceConstr appNumber evalue...
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Takes zero or more encoded values, packs them into an ASN choice
construct and returns its encoded binary form.
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::asn::asnInteger number
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Returns the encoded form of the specified integer
number.
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::asn::asnEnumeration number
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Returns the encoded form of the specified enumeration id
number.
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::asn::asnBoolean bool
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Returns the encoded form of the specified boolean value
bool.
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::asn::asnContext context data
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Takes an encoded value and packs it into a constructed value with
application tag, the context number.
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::asn::asnContextConstr context evalue...
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Takes zero or more encoded values and packs them into a constructed
value with application tag, the context number.
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::asn::asnObjectIdentifier idlist
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Takes a list of at least 2 integers describing an object identifier
(OID) value, and returns the encoded value.
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::asn::asnUTCTime utcstring
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Returns the encoded form of the specified UTC time string.
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::asn::asnNull
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Returns the NULL encoding.
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::asn::asnBitString string
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Returns the encoded form of the specified string.
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::asn::asnOctetString string
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Returns the encoded form of the specified string.
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::asn::asnNumericString string
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Returns the string encoded as ASN.1 NumericString. Raises an
error if the string contains characters other than decimal
numbers and space.
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::asn::asnPrintableString string
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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.
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::asn::asnIA5String string
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Returns the string encoded as ASN.1 IA5String. Raises an error
if the string contains any characters outside of the US-ASCII
range.
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::asn::asnBMPString string
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Returns the string encoded as ASN.1 Basic Multilingual Plane
string (Which is essentialy big-endian UCS2).
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::asn::asnUTF8String string
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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.
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::asn::asnString string
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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.
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::asn::defaultStringType ? type ?
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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.
General notes:
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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.
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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.
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::asn::asnPeekByte data_var byte_var
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Retrieve the first byte of the data, without modifing data_var.
This can be used to check for implicit tags.
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::asn::asnGetLength data_var length_var
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Decode the length information for a block of BER data. The tag has already
to be removed from the data.
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::asn::asnGetResponse chan data_var
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Reads an encoded ASN sequence from the channel chan and
stores it into the variable named by data_var.
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::asn::asnGetInteger data_var int_var
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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.
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::asn::asnGetEnumeration data_var enum_var
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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.
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::asn::asnGetOctetString data_var string_var
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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.
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::asn::asnGetString data_var string_var ? type_var ?
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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.
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::asn::asnGetNumericString data_var string_var
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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.
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::asn::asnGetPrintableString data_var string_var
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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.
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::asn::asnGetIA5String data_var string_var
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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.
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::asn::asnGetBMPString data_var string_var
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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.
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::asn::asnGetUTF8String data_var string_var
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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.
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::asn::asnGetUTCTime data_var utc_var
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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.
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::asn::asnGetBitString data_var bits_var
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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.
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::asn::asnGetObjectIdentifier data_var oid_var
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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.
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::asn::asnGetBoolean data_var bool_var
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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.
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::asn::asnGetNull data_var
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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.
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::asn::asnGetSequence data_var sequence_var
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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.
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::asn::asnGetSet data_var set_var
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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.
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::asn::asnGetApplication data_var appNumber_var ? content_var ? ? encodingType_var ?
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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.
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::asn::asnGetContext data_var contextNumber_var ? content_var ? ? encodingType_var ?
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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.
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:
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::asn::asnPeekTag data_var tag_var tagtype_var constr_var
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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.
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::asn::asnTag tagnumber ? class ? ? tagstyle ?
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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.
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::asn::asnRetag data_var newTag
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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 for the usage of this package can be found in the
implementation of package
ldap.
This document, and the package it describes, will undoubtedly contain
bugs and other problems.
Please report such in the category
asn of the
http://sourceforge.net/tracker/?group_id=12883.
Please also report any ideas for enhancements you may have for either
package and/or documentation.
asn, x.208, ber, x.209, der, cer, internet, protocol