extra.fld

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          FileName      Byte[32]    full Macintosh filename (pascal string)

          All fields but the first two are in native Macintosh format
          (big-endian Motorola order, not little-endian Intel).
          The extra field size is fixed to 64 bytes.
          The local-header and central-header versions are identical.


         -Acorn SparkFS Extra Field:
          =========================

          The following is the layout of David Pilling's SparkFS extra block
          for Acorn RISC OS.  The local-header and central-header versions are
          identical.  (Last Revision 19960922)

          Value         Size        Description
          -----         ----        -----------
  (Acorn) 0x4341        Short       tag for this extra block type ("AC")
          TSize         Short       total data size for this block (20)
          "ARC0"        Long        extra-field signature
          LoadAddr      Long        load address or file type
          ExecAddr      Long        exec address
          Attr          Long        file permissions
          Zero          Long        reserved; always zero

          The following bits of Attr are associated with the given file
          permissions:

                bit 0           user-writable ('W')
                bit 1           user-readable ('R')
                bit 2           reserved
                bit 3           locked ('L')
                bit 4           publicly writable ('w')
                bit 5           publicly readable ('r')
                bit 6           reserved
                bit 7           reserved


         -VM/CMS Extra Field:
          ==================

          The following is the layout of the file-attributes extra block for
          VM/CMS.  The local-header and central-header versions are
          identical.  (Last Revision 19960922)

          Value         Size        Description
          -----         ----        -----------
 (VM/CMS) 0x4704        Short       tag for this extra block type
          TSize         Short       total data size for this block
          flData        variable    file attributes data

          flData is an uncompressed fldata_t struct.


         -MVS Extra Field:
          ===============

          The following is the layout of the file-attributes extra block for
          MVS.  The local-header and central-header versions are identical.
          (Last Revision 19960922)

          Value         Size        Description
          -----         ----        -----------
  (MVS)   0x470f        Short       tag for this extra block type
          TSize         Short       total data size for this block
          flData        variable    file attributes data

          flData is an uncompressed fldata_t struct.


         -PKWARE Unix Extra Field (0x000d):
          ================================

          The following is the layout of PKWARE's Unix "extra" block.
          It was introduced with the release of PKZIP for Unix 2.50.
          Note: all fields are stored in Intel low-byte/high-byte order.
          (Last Revision 19980901)

          This field has a minimum data size of 12 bytes and is only stored
          as local extra field.

          Value         Size        Description
          -----         ----        -----------
 (Unix0)  0x000d        Short       Tag for this "extra" block type
          TSize         Short       Total Data Size for this block
          AcTime        Long        time of last access (UTC/GMT)
          ModTime       Long        time of last modification (UTC/GMT)
          UID           Short       Unix user ID
          GID           Short       Unix group ID
          (var)         variable    Variable length data field

          The variable length data field will contain file type
          specific data.  Currently the only values allowed are
          the original "linked to" file names for hard or symbolic
          links, and the major and minor device node numbers for
          character and block device nodes.  Since device nodes
          cannot be either symbolic or hard links, only one set of
          variable length data is stored.  Link files will have the
          name of the original file stored.  This name is NOT NULL
          terminated.  Its size can be determined by checking TSize -
          12.  Device entries will have eight bytes stored as two 4
          byte entries (in little-endian format).  The first entry
          will be the major device number, and the second the minor
          device number.

         [Info-ZIP note: The fixed part of this field has the same layout as
          Info-ZIP's abandoned "Unix1 timestamps & owner ID info" extra field;
          only the two tag bytes are different.]


         -PATCH Descriptor Extra Field (0x000f):
          =====================================

          The following is the layout of the Patch Descriptor "extra"
          block.

          Note: all fields stored in Intel low-byte/high-byte order.

          Value         Size        Description
          -----         ----        -----------
  (Patch) 0x000f        Short       Tag for this "extra" block type
          TSize         Short       Size of the total "extra" block
          Version       Short       Version of the descriptor
          Flags         Long        Actions and reactions (see below)
          OldSize       Long        Size of the file about to be patched
          OldCRC        Long        32-bit CRC of the file about to be patched
          NewSize       Long        Size of the resulting file
          NewCRC        Long        32-bit CRC of the resulting file


          Actions and reactions

          Bits          Description
          ----          ----------------
          0             Use for auto detection
          1             Treat as a self-patch
          2-3           RESERVED
          4-5           Action (see below)
          6-7           RESERVED
          8-9           Reaction (see below) to absent file
          10-11         Reaction (see below) to newer file
          12-13         Reaction (see below) to unknown file
          14-15         RESERVED
          16-31         RESERVED

          Actions

          Action       Value
          ------       -----
          none         0
          add          1
          delete       2
          patch        3

          Reactions

          Reaction     Value
          --------     -----
          ask          0
          skip         1
          ignore       2
          fail         3

          Patch support is provided by PKPatchMaker(tm) technology and is
          covered under U.S. Patents and Patents Pending.


         -PKCS#7 Store for X.509 Certificates (0x0014):
          ============================================

          This field contains information about each of the certificates
          files may be signed with.  When the Central Directory Encryption
          feature is enabled for a ZIP file, this record will appear in
          the Archive Extra Data Record, otherwise it will appear in the
          first central directory record and will be ignored in any
          other record.

          Note: all fields stored in Intel low-byte/high-byte order.

          Value     Size     Description
          -----     ----     -----------
  (Store) 0x0014    2 bytes  Tag for this "extra" block type
          TSize     2 bytes  Size of the store data
          SData     TSize    Data about the store

          SData
          Value     Size        Description
          -----     ----        -----------
          Version   2 bytes     Version number, 0x0001 for now
          StoreD    (variable)  Actual store data

          The StoreD member is suitable for passing as the pbData
          member of a CRYPT_DATA_BLOB to the CertOpenStore() function
          in Microsoft's CryptoAPI.  The SSize member above will be
          cbData + 6, where cbData is the cbData member of the same
          CRYPT_DATA_BLOB.  The encoding type to pass to
          CertOpenStore() should be
          PKCS_7_ANS_ENCODING | X509_ASN_ENCODING.


         -X.509 Certificate ID and Signature for individual file (0x0015):
          ===============================================================

          This field contains the information about which certificate in
          the PKCS#7 store was used to sign a particular file.  It also
          contains the signature data.  This field can appear multiple
          times, but can only appear once per certificate.

          Note: all fields stored in Intel low-byte/high-byte order.

          Value         Size        Description
          -----         ----        -----------
  (CID)   0x0015        2 bytes     Tag for this "extra" block type
          CSize         2 bytes     Size of Method
          Method        (variable)

          Method
          Value         Size        Description
          -----         ----        -----------
          Version       2 bytes     Version number, for now 0x0001
          AlgID         2 bytes     Algorithm ID used for signing
          IDSize        2 bytes     Size of Certificate ID data
          CertID        (variable)  Certificate ID data
          SigSize       2 bytes     Size of Signature data
          Sig           (variable)  Signature data

          CertID
          Value         Size        Description
          -----         ----        -----------
          Size1         4 bytes     Size of CertID, should be (IDSize - 4)
          Size1         4 bytes     A bug in version one causes this value
                                    to appear twice.
          IssSize       4 bytes     Issuer data size
          Issuer        (variable)  Issuer data
          SerSize       4 bytes     Serial Number size
          Serial        (variable)  Serial Number data

          The Issuer and IssSize members are suitable for creating a
          CRYPT_DATA_BLOB to be the Issuer member of a CERT_INFO
          struct. The Serial and SerSize members would be the
          SerialNumber member of the same CERT_INFO struct.  This
          struct would be used to find the certificate in the store
          the file was signed with.  Those structures are from the MS
          CryptoAPI.

          Sig and SigSize are the actual signature data and size
          generated by signing the file with the MS CryptoAPI using a
          hash created with the given AlgID.


         -X.509 Certificate ID and Signature for central directory (0x0016):
          =================================================================

          This field contains the information about which certificate in
          the PKCS#7 store was used to sign the central directory structure.
          When the Central Directory Encryption feature is enabled for a
          ZIP file, this record will appear in the Archive Extra Data Record,
          otherwise it will appear in the first central directory record,
          along with the store.  The data structure is the
          same as the CID, except that SigSize will be 0, and there
          will be no Sig member.

          This field is also kept after the last central directory
          record, as the signature data (ID 0x05054b50, it looks like
          a central directory record of a different type).  This
          second copy of the data is the Signature Data member of the
          record, and will have a SigSize that is non-zero, and will
          have Sig data.

          Note: all fields stored in Intel low-byte/high-byte order.

          Value     Size     Description
          -----     ----     -----------
  (CDID)  0x0016    2 bytes  Tag for this "extra" block type
          TSize     2 bytes  Size of data that follows
          TData     TSize    Data


         -Strong Encryption Header (0x0017) (EFS):
          ===============================

          Value     Size     Description
          -----     ----     -----------
          0x0017    2 bytes  Tag for this "extra" block type
          TSize     2 bytes  Size of data that follows
          Format    2 bytes  Format definition for this record
          AlgID     2 bytes  Encryption algorithm identifier
          Bitlen    2 bytes  Bit length of encryption key
          Flags     2 bytes  Processing flags