📄 extra.fld
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CertData TSize-8 Certificate decryption extra field data (refer to the explanation for CertData in the section describing the Certificate Processing Method under the Strong Encryption Specification) -Record Management Controls (0x0018): =================================== Value Size Description ----- ---- -----------(Rec-CTL) 0x0018 2 bytes Tag for this "extra" block type CSize 2 bytes Size of total extra block data Tag1 2 bytes Record control attribute 1 Size1 2 bytes Size of attribute 1, in bytes Data1 Size1 Attribute 1 data . . . TagN 2 bytes Record control attribute N SizeN 2 bytes Size of attribute N, in bytes DataN SizeN Attribute N data -PKCS#7 Encryption Recipient Certificate List (0x0019): (EFS) ===================================================== This field contains the information about each of the certificates that files may be encrypted with. This field should only appear in the archive extra data record. This field is not required and serves only to aide archive modifications by preserving public encryption data. Individual security requirements may dictate that this data be omitted to deter information exposure. Note: all fields stored in Intel low-byte/high-byte order. Value Size Description ----- ---- ----------- (CStore) 0x0019 2 bytes Tag for this "extra" block type TSize 2 bytes Size of the store data TData TSize Data about the store TData: Value Size Description ----- ---- ----------- Version 2 bytes Format version number - must 0x0001 at this time CStore (var) PKCS#7 data blob -MVS Extra Field (PKWARE, 0x0065): ================================ The following is the layout of the MVS "extra" block. Note: Some fields are stored in Big Endian format. All text is in EBCDIC format unless otherwise specified. Value Size Description ----- ---- ----------- (MVS) 0x0065 2 bytes Tag for this "extra" block type TSize 2 bytes Size for the following data block ID 4 bytes EBCDIC "Z390" 0xE9F3F9F0 or "T4MV" for TargetFour (var) TSize-4 Attribute data -OS/400 Extra Field (0x0065): =========================== The following is the layout of the OS/400 "extra" block. Note: Some fields are stored in Big Endian format. All text is in EBCDIC format unless otherwise specified. Value Size Description ----- ---- ----------- (OS400) 0x0065 2 bytes Tag for this "extra" block type TSize 2 bytes Size for the following data block ID 4 bytes EBCDIC "I400" 0xC9F4F0F0 or "T4MV" for TargetFour (var) TSize-4 Attribute data -Extended Timestamp Extra Field: ============================== The following is the layout of the extended-timestamp extra block. (Last Revision 19970118) Local-header version: Value Size Description ----- ---- ----------- (time) 0x5455 Short tag for this extra block type ("UT") TSize Short total data size for this block Flags Byte info bits (ModTime) Long time of last modification (UTC/GMT) (AcTime) Long time of last access (UTC/GMT) (CrTime) Long time of original creation (UTC/GMT) Central-header version: Value Size Description ----- ---- ----------- (time) 0x5455 Short tag for this extra block type ("UT") TSize Short total data size for this block Flags Byte info bits (refers to local header!) (ModTime) Long time of last modification (UTC/GMT) The central-header extra field contains the modification time only, or no timestamp at all. TSize is used to flag its presence or absence. But note: If "Flags" indicates that Modtime is present in the local header field, it MUST be present in the central header field, too! This correspondence is required because the modification time value may be used to support trans-timezone freshening and updating operations with zip archives. The time values are in standard Unix signed-long format, indicating the number of seconds since 1 January 1970 00:00:00. The times are relative to Coordinated Universal Time (UTC), also sometimes referred to as Greenwich Mean Time (GMT). To convert to local time, the software must know the local timezone offset from UTC/GMT. The lower three bits of Flags in both headers indicate which time- stamps are present in the LOCAL extra field: bit 0 if set, modification time is present bit 1 if set, access time is present bit 2 if set, creation time is present bits 3-7 reserved for additional timestamps; not set Those times that are present will appear in the order indicated, but any combination of times may be omitted. (Creation time may be present without access time, for example.) TSize should equal (1 + 4*(number of set bits in Flags)), as the block is currently defined. Other timestamps may be added in the future. -Info-ZIP Unix Extra Field (type 1): ================================== The following is the layout of the old Info-ZIP extra block for Unix. It has been replaced by the extended-timestamp extra block (0x5455) and the Unix type 2 extra block (0x7855). (Last Revision 19970118) Local-header version: Value Size Description ----- ---- ----------- (Unix1) 0x5855 Short tag for this extra block type ("UX") 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 (optional) GID Short Unix group ID (optional) Central-header version: Value Size Description ----- ---- ----------- (Unix1) 0x5855 Short tag for this extra block type ("UX") TSize Short total data size for this block AcTime Long time of last access (GMT/UTC) ModTime Long time of last modification (GMT/UTC) The file access and modification times are in standard Unix signed- long format, indicating the number of seconds since 1 January 1970 00:00:00. The times are relative to Coordinated Universal Time (UTC), also sometimes referred to as Greenwich Mean Time (GMT). To convert to local time, the software must know the local timezone offset from UTC/GMT. The modification time may be used by non-Unix systems to support inter-timezone freshening and updating of zip archives. The local-header extra block may optionally contain UID and GID info for the file. The local-header TSize value is the only indication of this. Note that Unix UIDs and GIDs are usually specific to a particular machine, and they generally require root access to restore. This extra field type is obsolete, but it has been in use since mid-1994. Therefore future archiving software should continue to support it. Some guidelines: An archive member should either contain the old "Unix1" extra field block or the new extra field types "time" and/or "Unix2". If both the old "Unix1" block type and one or both of the new block types "time" and "Unix2" are found, the "Unix1" block should be considered invalid and ignored. Unarchiving software should recognize both old and new extra field block types, but the info from new types overrides the old "Unix1" field. Archiving software should recognize "Unix1" extra fields for timestamp comparison but never create it for updated, freshened or new archive members. When copying existing members to a new archive, any "Unix1" extra field blocks should be converted to the new "time" and/or "Unix2" types. -Info-ZIP Unix Extra Field (type 2): ================================== The following is the layout of the new Info-ZIP extra block for Unix. (Last Revision 19960922) Local-header version: Value Size Description ----- ---- ----------- (Unix2) 0x7855 Short tag for this extra block type ("Ux") TSize Short total data size for this block (4) UID Short Unix user ID GID Short Unix group ID Central-header version: Value Size Description ----- ---- ----------- (Unix2) 0x7855 Short tag for this extra block type ("Ux") TSize Short total data size for this block (0) The data size of the central-header version is zero; it is used solely as a flag that UID/GID info is present in the local-header extra field. If additional fields are ever added to the local version, the central version may be extended to indicate this. Note that Unix UIDs and GIDs are usually specific to a particular machine, and they generally require root access to restore. -ASi Unix Extra Field: ==================== The following is the layout of the ASi extra block for Unix. The local-header and central-header versions are identical. (Last Revision 19960916) Value Size Description ----- ---- ----------- (Unix3) 0x756e Short tag for this extra block type ("nu") TSize Short total data size for this block CRC Long CRC-32 of the remaining data Mode Short file permissions SizDev Long symlink'd size OR major/minor dev num UID Short user ID GID Short group ID (var.) variable symbolic link filename Mode is the standard Unix st_mode field from struct stat, containing user/group/other permissions, setuid/setgid and symlink info, etc. If Mode indicates that this file is a symbolic link, SizDev is the size of the file to which the link points. Otherwise, if the file is a device, SizDev contains the standard Unix st_rdev field from struct stat (includes the major and minor numbers of the device). SizDev is undefined in other cases. If Mode indicates that the file is a symbolic link, the final field will be the name of the file to which the link points. The file- name length can be inferred from TSize. [Note that TSize may incorrectly refer to the data size not counting the CRC; i.e., it may be four bytes too small.] -BeOS Extra Field: ================ The following is the layout of the file-attributes extra block for BeOS. (Last Revision 19970531) Local-header version: Value Size Description ----- ---- ----------- (BeOS) 0x6542 Short tag for this extra block type ("Be") TSize Short total data size for this block BSize Long uncompressed file attribute data size Flags Byte info bits (CType) Short compression type (CRC) Long CRC value for uncompressed file attribs Attribs variable file attribute data⌨️ 快捷键说明
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