Standards Track J. Strombergson Internet-Draft InformAsic AB Expires: December 28, 2004 L. Walleij Ledasa Rangers P. Faltstrom Cisco Systems Inc June 29, 2004 The Standard Hex Format draft-strombergson-shf-01.txt Status of this Memo By submitting this Internet-Draft, I certify that any applicable patent or other IPR claims of which I am aware have been disclosed, and any of which I become aware will be disclosed, in accordance with RFC 3668. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http:// www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on December 28, 2004. Copyright Notice Copyright (C) The Internet Society (2004). All Rights Reserved. Abstract This document specifies the Standard Hex Format (SHF), a new, XML-based open format for describing hexadecimal data. SHF provides the ability to describe both small and large, simple and complex hexadecimal data dumps in an open, modern, transport and vendor neutral format. Strombergson, et al. Expires December 28, 2004 [Page 1] Internet-Draft The Standard Hex Format June 2004 1. Introduction In the computing, network and embedded systems communities several different types of data formats for hexadecimal data are being used. Typical uses include executable object code for embedded systems (i.e. "firmware"), on-chip flash memories and filesystems, FPGA configuration bitstreams, graphics and other application resources, routing tables, etc. Unfortunately, none of the formats used are truly open, vendor neutral and/or well defined. Even more problematic is the fact that none of these formats are able to represent data sizes that are getting more and more common. Data dumps comprising of multiple sub-blocks with different word sizes, data sizes spanning anywhere from a few bytes of data to data sizes much larger than 2^32 bits are not handled. Also, the checksum included in these formats are too simplistic and for larger data sizes provides insufficient ability to accurately detect errors. Alternatively, the overhead needed for proper error detection is very large. The Standard Hex format therefore is an effort to provide a modern, XML based format that is not too complex for simple tools and computing environments to implement, generate, parse and use. Yet the format is able to handle large data sizes, complex data structures and provide high quality error detection by leveraging standardized cryptographic hash functions. At present, the usage of the SHF format may be mainly for Internet transport and file storage on development machinery. A parser for the XML format is presently not easily deployed in hardware devices, but the parsing and checksumming of the SHF data may be done by a workstation computer which in turn convert the SHF tokens to an ordinary bitstream before the last step of e.g. a firmware upgrade commence. Strombergson, et al. Expires December 28, 2004 [Page 2] Internet-Draft The Standard Hex Format June 2004 2. Terminology The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 [1]. The key word Byte is to be interpreted as a group of 8 bits. The key word Octet is another name for Byte. The key word Word is to be interpreted as a group containing an integral number of Bytes. The expressiom 2^n is to be interpreted as the value two (2) raised to the n:th power. For example 2^8 equals the value 256. Strombergson, et al. Expires December 28, 2004 [Page 3] Internet-Draft The Standard Hex Format June 2004 3. Features and functionality The SHF-format has the following features: o Support for arbitrarily wide data words o Support for very large data blocks o Support for an arbitrary number of independent data blocks o Data integrity detection against errors provided by the RFC3174 specified (see [2]) SHA-1 cryptographic signature o An XML-based format In the embedded systems domain, 8- and 16-bit system are still used in large numbers and will continue to do so for any forseeable future. Simultaneously, more and more systems are using 64-bit and even larger word sizes. SHF supports all of these systems by allowing the word size to be specified. The word size MUST be an integer number of Bytes and at least one (1) Byte. SHF is able to represent both large and small data blocks. The data block MUST contain at least one (1) Word. Additionally, the data block MUST NOT be larger than (2^64)-1 bits. The SHF dump MUST contain at least one (1) data block. The maximum number of blocks supported is 2^64. Each data block in the dump MAY have different word sizes and start at different addresses. The checksum (or message digest) used to verify the correctness or data integrity of each block is 20 Bytes (160 bits) long. The digest MUST be calculated on the data actually represented by the SHF data block, NOT the representation, i.e. NOT the ASCII-code. SHA-1 is only able to calculate a digest for a data block no larger than (2^64)-1 bits and this limits the size of each data block to in SHF to (2^64)-1 bits. Strombergson, et al. Expires December 28, 2004 [Page 4] Internet-Draft The Standard Hex Format June 2004 4. SHF XML specification The SHF format consists of an XML data structure representing a dump. The dump consists of a dump header section and one (1) or more block sections containing data. Each block of data is independent of any other block. A short, symbolic example of a SHF dump is illustrated by the following structure: (Data) 4.1 Header section The header section comprises of the the dump tag which includes the following attributes: o name: A string of arbitrary length used by any interested party to identify the specific SHF dump. o blocks: A 64 bit hexadecimal value representing the number of blocks in the specific SHF dump. After the preceding dump tag one or more subsections of blocks must follow. Finally, the complete SHF dump end with a closing dump tag. 4.2 Block subsection The block subsection contains a block tag and a data subsection. The block tag includes the following attributes: o name: A string of arbitrary length used by any interested party to identify the specific block. o start_address: A 64 bit hexadecimal value representing the start address in Bytes for the data in the block. o word_size: A 64 bit hexadecimal value representing the number of Bytes (the width) of one Word of the data. o length: A hexadecimal representation of an unsigned 64-bit integer indicating the number of words in the "data" element. Strombergson, et al. Expires December 28, 2004 [Page 5] Internet-Draft The Standard Hex Format June 2004 o checksum: A hexadecimal representation of the 20 Byte SHA-1 digest of the data in the block. The total size of the data in the block (in bits) is given by the expression (8 * word_size * length). The expression MUST NOT be larger than (2^64)-1. After the preceding block tag one subsection of data MUST follow. Finally, the block section ends with a closing block tag. 4.3 data subsection The data subsection of the block section compises of the opening and closing data tags and the hexadecimal representation of the actual data in the block. Strombergson, et al. Expires December 28, 2004 [Page 6] Internet-Draft The Standard Hex Format June 2004 5. SHF rules and limits There are several rules and permissions in SHF: o The data and attribute values representing an actual value MUST be in Big Endian-format. It is the responsibility of the SHF-generator to ensure that these attributes are Big Endian. Similarly, if needed, it is the responsibility of any SHF consumer to swap the attribute values to the appropriate Endianness as needed by the SHF consumer. o All attribute values representing an actual value and the data MUST be in hexadecimal notation. The attributes excluded from this rule is the name attribute in the dump and block tags. o All attribute values with the exception for the checksum MAY be leading zero truncated. Conversely, the checksum MUST NOT be leading zero truncated. o The data represented in a block MUST NOT be larger than (2^64)-1 bits. o The size of a word MUST NOT be larger than (2^64)-1 bits. This implies that a block with a word defined to the maximum width can not contain more than one Word. Strombergson, et al. Expires December 28, 2004 [Page 7] Internet-Draft The Standard Hex Format June 2004 6. SHF DTD The elements named "data" and the attributes "blocks", "address", "word_size" and "checksum" should only contain the characters which are valid hexbyte sequences. These are: whitespace ::= (#x20 | #x9 | #xD | #xA)+ hexdigit ::= [0-9A-Fa-f] hexbytes ::= whitespace* hexdigit (hexdigit|whitespace)* A parser reading in an SHF file should silently ignore any other characters that would by mistake appear in any of these elements or attributes. These alien characters should be treated as if they did not exist. Also note that "whitespace" has no semantic meaning, it is only valid for the reason of improving human readability of the dump. Whitepace may be altogether removed and the hexbyte sequences concatenated if desired. Strombergson, et al. Expires December 28, 2004 [Page 8] Internet-Draft The Standard Hex Format June 2004 7. SHF examples This section contains three different SHF examples, illustrating the usage of SHF and the attributes in SHF. The first example is a simple SHF dump with a single block of data: 41 6c 6c 20 79 6f 75 72 20 62 61 73 65 20 61 72 65 20 62 65 6c 6f 6e 67 20 74 6f 20 75 73 0a The second example is a program in 6502 machine code residing at memory address 0x1000, which calculates the 13 first fibonacci numbers and stores them at 0x1101-0x110d: a9 01 85 20 85 21 20 1e 10 20 1e 10 18 a5 21 aa 65 20 86 20 85 21 20 1e 10 c9 c8 90 ef 60 ae 00 11 a5 21 9d 00 11 ee 00 11 60 01 00 00 00 00 00 00 00 00 00 00 00 00 00 The final example contains a block of 40-bit wide data: 00100 00200 00000 00090 00000 00036 00300 00400 00852 00250 00230 00858 00500 00600 014DC 00058 002A8 000B8 00700 00800 000B0 00192 00100 00000 Strombergson, et al. Expires December 28, 2004 [Page 9] Internet-Draft The Standard Hex Format June 2004 00900 00A00 00000 0000A 40000 00000 00B00 00C00 00000 00000 00000 00001 00D00 00E00 00000 00100 0CCCC CCCCD 00F00 01000 00000 00010 80000 00000 00100 00790 00000 00234 Strombergson, et al. Expires December 28, 2004 [Page 10] Internet-Draft The Standard Hex Format June 2004 8. SHF security considerations The SHF format is a format for representing hexadecimal data that one wants to transfer, manage or transform. The format itself does not guarantee that the represented data is falsely represented, malicious or otherwise dangerous. The data integrity of the SHF file as a whole is to be provided, if needed, by external mean (as to the SHF file) such as the generic signing mechanism described by RFC 3275 [3]. Strombergson, et al. Expires December 28, 2004 [Page 11] Internet-Draft The Standard Hex Format June 2004 9. MIME Registration Information This section contains the registration information for the MIME type to SHF. o Registration: application/shf+xml o MIME media type name: application o MIME subtype name: shf+xml o Required parameters: charset 9.1 Required parameters This parameter must exist and must be set to "UTF-8". No other character sets are allowed for transporting SHF data. The character set designator MUST NOT be quoted and MUST be uppercase, yielding this exact appearance: charset=UTF-8 9.2 Encoding considerations This media type may contain binary content; accordingly, when used over a transport that does not permit binary transfer, an appropriate encoding must be applied. 9.3 Security considerations A hex dump in itself has no other security considerations than what applies for any other XML file. However the included binary data may in decoded form contain any executable code for a target platform. If additional security is desired, additional transport security solutions may be applied. For target code contained in a hex dump, developers may want to include certificates, checksums and the like in hexdump form for the target platform. Such uses is outside the scope of this document and a matter of implementation. 9.4 Interoperability considerations n/a 9.5 Published specification This media type is a proper subset of the the XML 1.0 specification [WWWXML]. Two restrictions are made. First, no entity references other than the five predefined general entities references ("&", "<", ">", "'", and """) and numeric entity references may be present. Second, neither the "XML" declaration (e.g., ) nor the "DOCTYPE" declaration (e.g., ) may be present. All other XML 1.0 instructions (e.g., CDATA blocks, processing instructions, and so on) are allowed. Strombergson, et al. Expires December 28, 2004 [Page 12] Internet-Draft The Standard Hex Format June 2004 Applications which use this media type: any program or individual wishing to make use of this XML 1.0 subset for hexdump exchange. Additional Information: o Magic number: There is no single initial byte sequence that is always present for SHF files o File extension: shf o Macintosh File Type code: none Strombergson, et al. Expires December 28, 2004 [Page 13] Internet-Draft The Standard Hex Format June 2004 10. Extensions The namespace of the SHF XML format may be extended when need arise. For example, certain applications will want to represent executable code as a SHF dump and may then need a start address to be associated with certain dump blocks, so that the address can be configured as a starting point for the code in the block. This can be done by exending the namespace for a block tag with a "start_address" attribute. As long as such new attributes are added, with no attributes being removed or redefined, the resulting dump shall be considered a valid SHF dump, transported using the application/xml+shf transport type, and parsers unaware of the modified namespace shall silently ignore any such extended attributes, or simply duplicate them from input to output when processing an SHF file as a filter. The management of such extended attributes is a matter of convention between different classes of users and not a matter of the IETF. Strombergson, et al. Expires December 28, 2004 [Page 14] Internet-Draft The Standard Hex Format June 2004 11. Additional information Contact for further information: c.f., the "Author's Address" section of this memo. Intended usage: COMMON. Author/Change controller: the authors of this document. Acknowledgment: The SMIL memory dump was kindly provided by Sten Henriksson at Lund University. Proofreading and good feedback on the SHF draft was generously provided by Peter Lindgren. 12 References [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [2] Eastlake, 3rd, D. and P. Jones, "US Secure Hash Algorithm 1 (SHA1)", BCP 14, RFC 3174, September 2001. [3] Eastlake, 3rd, D., Joseph, J. and D. David, "(Extensible Markup Language) XML-Signature Syntax and Processing", BCP 14, RFC 3275, March 2002. [4] Makoto, M., Simon, S. and D. Dan, "(Extensible Markup Language) XML Media Types", BCP 14, RFC 3023, January 2001. Authors' Addresses Joachim Strombergson InformAsic AB Hugo Grauers gata 5a Gothenburg 411 33 SE Phone: +46 31 68 54 90 EMail: Joachim.Strombergson@InformAsic.com URI: http://www.InformAsic.com/ Strombergson, et al. Expires December 28, 2004 [Page 15] Internet-Draft The Standard Hex Format June 2004 Linus Walleij Ledasa Rangers Master Olofs Vag 24 Lund 224 66 SE Phone: +46 703 193678 EMail: triad@df.lth.se Patrik Faltstrom Cisco Systems Inc Ledasa 273 71 Lovestad Sweden EMail: paf@cisco.com URI: http://www.cisco.com Strombergson, et al. Expires December 28, 2004 [Page 16] Internet-Draft The Standard Hex Format June 2004 Intellectual Property Statement The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. Information on the IETF's procedures with respect to rights in IETF Documents can be found in BCP 78 and BCP 79. 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