src/tar.h

   1 /* GNU tar Archive Format description.
   2
   3    Copyright 1988-2020 Free Software Foundation, Inc.
   4
   5    This file is part of GNU tar.
   6
   7    GNU tar is free software; you can redistribute it and/or modify
   8    it under the terms of the GNU General Public License as published by
   9    the Free Software Foundation; either version 3 of the License, or
  10    (at your option) any later version.
  11
  12    GNU tar is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15    GNU General Public License for more details.
  16
  17    You should have received a copy of the GNU General Public License
  18    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  19
  20 /* tar Header Block, from POSIX 1003.1-1990.  */
  21
  22 /* POSIX header.  */
  23
  24 struct posix_header
  25 {                               /* byte offset */
  26   char name[100];               /*   0 */
  27   char mode[8];                 /* 100 */
  28   char uid[8];                  /* 108 */
  29   char gid[8];                  /* 116 */
  30   char size[12];                /* 124 */
  31   char mtime[12];               /* 136 */
  32   char chksum[8];               /* 148 */
  33   char typeflag;                /* 156 */
  34   char linkname[100];           /* 157 */
  35   char magic[6];                /* 257 */
  36   char version[2];              /* 263 */
  37   char uname[32];               /* 265 */
  38   char gname[32];               /* 297 */
  39   char devmajor[8];             /* 329 */
  40   char devminor[8];             /* 337 */
  41   char prefix[155];             /* 345 */
  42                                 /* 500 */
  43 };
  44
  45 #define TMAGIC   "ustar"        /* ustar and a null */
  46 #define TMAGLEN  6
  47 #define TVERSION "00"           /* 00 and no null */
  48 #define TVERSLEN 2
  49
  50 /* Values used in typeflag field.  */
  51 #define REGTYPE  '0'            /* regular file */
  52 #define AREGTYPE '\0'           /* regular file */
  53 #define LNKTYPE  '1'            /* link */
  54 #define SYMTYPE  '2'            /* reserved */
  55 #define CHRTYPE  '3'            /* character special */
  56 #define BLKTYPE  '4'            /* block special */
  57 #define DIRTYPE  '5'            /* directory */
  58 #define FIFOTYPE '6'            /* FIFO special */
  59 #define CONTTYPE '7'            /* reserved */
  60
  61 #define XHDTYPE  'x'            /* Extended header referring to the
  62                                    next file in the archive */
  63 #define XGLTYPE  'g'            /* Global extended header */
  64
  65 /* Bits used in the mode field, values in octal.  */
  66 #define TSUID    04000          /* set UID on execution */
  67 #define TSGID    02000          /* set GID on execution */
  68 #define TSVTX    01000          /* reserved */
  69                                 /* file permissions */
  70 #define TUREAD   00400          /* read by owner */
  71 #define TUWRITE  00200          /* write by owner */
  72 #define TUEXEC   00100          /* execute/search by owner */
  73 #define TGREAD   00040          /* read by group */
  74 #define TGWRITE  00020          /* write by group */
  75 #define TGEXEC   00010          /* execute/search by group */
  76 #define TOREAD   00004          /* read by other */
  77 #define TOWRITE  00002          /* write by other */
  78 #define TOEXEC   00001          /* execute/search by other */
  79
  80 /* tar Header Block, GNU extensions.  */
  81
  82 /* In GNU tar, SYMTYPE is for to symbolic links, and CONTTYPE is for
  83    contiguous files, so maybe disobeying the "reserved" comment in POSIX
  84    header description.  I suspect these were meant to be used this way, and
  85    should not have really been "reserved" in the published standards.  */
  86
  87 /* *BEWARE* *BEWARE* *BEWARE* that the following information is still
  88    boiling, and may change.  Even if the OLDGNU format description should be
  89    accurate, the so-called GNU format is not yet fully decided.  It is
  90    surely meant to use only extensions allowed by POSIX, but the sketch
  91    below repeats some ugliness from the OLDGNU format, which should rather
  92    go away.  Sparse files should be saved in such a way that they do *not*
  93    require two passes at archive creation time.  Huge files get some POSIX
  94    fields to overflow, alternate solutions have to be sought for this.  */
  95
  96 /* Descriptor for a single file hole.  */
  97
  98 struct sparse
  99 {                               /* byte offset */
 100   char offset[12];              /*   0 */
 101   char numbytes[12];            /*  12 */
 102                                 /*  24 */
 103 };
 104
 105 /* Sparse files are not supported in POSIX ustar format.  For sparse files
 106    with a POSIX header, a GNU extra header is provided which holds overall
 107    sparse information and a few sparse descriptors.  When an old GNU header
 108    replaces both the POSIX header and the GNU extra header, it holds some
 109    sparse descriptors too.  Whether POSIX or not, if more sparse descriptors
 110    are still needed, they are put into as many successive sparse headers as
 111    necessary.  The following constants tell how many sparse descriptors fit
 112    in each kind of header able to hold them.  */
 113
 114 #define SPARSES_IN_EXTRA_HEADER  16
 115 #define SPARSES_IN_OLDGNU_HEADER 4
 116 #define SPARSES_IN_SPARSE_HEADER 21
 117
 118 /* Extension header for sparse files, used immediately after the GNU extra
 119    header, and used only if all sparse information cannot fit into that
 120    extra header.  There might even be many such extension headers, one after
 121    the other, until all sparse information has been recorded.  */
 122
 123 struct sparse_header
 124 {                               /* byte offset */
 125   struct sparse sp[SPARSES_IN_SPARSE_HEADER];
 126                                 /*   0 */
 127   char isextended;              /* 504 */
 128                                 /* 505 */
 129 };
 130
 131 /* The old GNU format header conflicts with POSIX format in such a way that
 132    POSIX archives may fool old GNU tar's, and POSIX tar's might well be
 133    fooled by old GNU tar archives.  An old GNU format header uses the space
 134    used by the prefix field in a POSIX header, and cumulates information
 135    normally found in a GNU extra header.  With an old GNU tar header, we
 136    never see any POSIX header nor GNU extra header.  Supplementary sparse
 137    headers are allowed, however.  */
 138
 139 struct oldgnu_header
 140 {                               /* byte offset */
 141   char unused_pad1[345];        /*   0 */
 142   char atime[12];               /* 345 Incr. archive: atime of the file */
 143   char ctime[12];               /* 357 Incr. archive: ctime of the file */
 144   char offset[12];              /* 369 Multivolume archive: the offset of
 145                                    the start of this volume */
 146   char longnames[4];            /* 381 Not used */
 147   char unused_pad2;             /* 385 */
 148   struct sparse sp[SPARSES_IN_OLDGNU_HEADER];
 149                                 /* 386 */
 150   char isextended;              /* 482 Sparse file: Extension sparse header
 151                                    follows */
 152   char realsize[12];            /* 483 Sparse file: Real size*/
 153                                 /* 495 */
 154 };
 155
 156 /* OLDGNU_MAGIC uses both magic and version fields, which are contiguous.
 157    Found in an archive, it indicates an old GNU header format, which will be
 158    hopefully become obsolescent.  With OLDGNU_MAGIC, uname and gname are
 159    valid, though the header is not truly POSIX conforming.  */
 160 #define OLDGNU_MAGIC "ustar  "  /* 7 chars and a null */
 161
 162 /* The standards committee allows only capital A through capital Z for
 163    user-defined expansion.  Other letters in use include:
 164
 165    'A' Solaris Access Control List
 166    'E' Solaris Extended Attribute File
 167    'I' Inode only, as in 'star'
 168    'N' Obsolete GNU tar, for file names that do not fit into the main header.
 169    'X' POSIX 1003.1-2001 eXtended (VU version)  */
 170
 171 /* This is a dir entry that contains the names of files that were in the
 172    dir at the time the dump was made.  */
 173 #define GNUTYPE_DUMPDIR 'D'
 174
 175 /* Identifies the *next* file on the tape as having a long linkname.  */
 176 #define GNUTYPE_LONGLINK 'K'
 177
 178 /* Identifies the *next* file on the tape as having a long name.  */
 179 #define GNUTYPE_LONGNAME 'L'
 180
 181 /* This is the continuation of a file that began on another volume.  */
 182 #define GNUTYPE_MULTIVOL 'M'
 183
 184 /* This is for sparse files.  */
 185 #define GNUTYPE_SPARSE 'S'
 186
 187 /* This file is a tape/volume header.  Ignore it on extraction.  */
 188 #define GNUTYPE_VOLHDR 'V'
 189
 190 /* Solaris extended header */
 191 #define SOLARIS_XHDTYPE 'X'
 192
 193 /* J@"org Schilling star header */
 194
 195 struct star_header
 196 {                               /* byte offset */
 197   char name[100];               /*   0 */
 198   char mode[8];                 /* 100 */
 199   char uid[8];                  /* 108 */
 200   char gid[8];                  /* 116 */
 201   char size[12];                /* 124 */
 202   char mtime[12];               /* 136 */
 203   char chksum[8];               /* 148 */
 204   char typeflag;                /* 156 */
 205   char linkname[100];           /* 157 */
 206   char magic[6];                /* 257 */
 207   char version[2];              /* 263 */
 208   char uname[32];               /* 265 */
 209   char gname[32];               /* 297 */
 210   char devmajor[8];             /* 329 */
 211   char devminor[8];             /* 337 */
 212   char prefix[131];             /* 345 */
 213   char atime[12];               /* 476 */
 214   char ctime[12];               /* 488 */
 215                                 /* 500 */
 216 };
 217
 218 #define SPARSES_IN_STAR_HEADER      4
 219 #define SPARSES_IN_STAR_EXT_HEADER  21
 220
 221 struct star_in_header
 222 {
 223   char fill[345];       /*   0  Everything that is before t_prefix */
 224   char prefix[1];       /* 345  t_name prefix */
 225   char fill2;           /* 346  */
 226   char fill3[8];        /* 347  */
 227   char isextended;      /* 355  */
 228   struct sparse sp[SPARSES_IN_STAR_HEADER]; /* 356  */
 229   char realsize[12];    /* 452  Actual size of the file */
 230   char offset[12];      /* 464  Offset of multivolume contents */
 231   char atime[12];       /* 476  */
 232   char ctime[12];       /* 488  */
 233   char mfill[8];        /* 500  */
 234   char xmagic[4];       /* 508  "tar" */
 235 };
 236
 237 struct star_ext_header
 238 {
 239   struct sparse sp[SPARSES_IN_STAR_EXT_HEADER];
 240   char isextended;
 241 };
 242
 243 /* END */
 244 \f
 245
 246 /* tar Header Block, overall structure.  */
 247
 248 /* tar files are made in basic blocks of this size.  */
 249 #define BLOCKSIZE 512
 250
 251 enum archive_format
 252 {
 253   DEFAULT_FORMAT,               /* format to be decided later */
 254   V7_FORMAT,                    /* old V7 tar format */
 255   OLDGNU_FORMAT,                /* GNU format as per before tar 1.12 */
 256   USTAR_FORMAT,                 /* POSIX.1-1988 (ustar) format */
 257   POSIX_FORMAT,                 /* POSIX.1-2001 format */
 258   STAR_FORMAT,                  /* Star format defined in 1994 */
 259   GNU_FORMAT                    /* Same as OLDGNU_FORMAT with one exception:
 260                                    see FIXME note for to_chars() function
 261                                    (create.c:189) */
 262 };
 263
 264 /* Information about a sparse file.  */
 265 struct sp_array
 266 {
 267   off_t offset;
 268   off_t numbytes;
 269 };
 270
 271 struct xheader
 272 {
 273   struct obstack *stk;
 274   size_t size;
 275   char *buffer;
 276   uintmax_t string_length;
 277 };
 278
 279 /* Information about xattrs for a file.  */
 280 struct xattr_array
 281   {
 282     char *xkey;
 283     char *xval_ptr;
 284     size_t xval_len;
 285   };
 286
 287 struct tar_stat_info
 288 {
 289   char *orig_file_name;     /* name of file read from the archive header */
 290   char *file_name;          /* name of file for the current archive entry
 291                                after being normalized.  */
 292   bool had_trailing_slash;  /* true if the current archive entry had a
 293                                trailing slash before it was normalized. */
 294   char *link_name;          /* name of link for the current archive entry.  */
 295
 296   char          *uname;     /* user name of owner */
 297   char          *gname;     /* group name of owner */
 298
 299   char *cntx_name;          /* SELinux context for the current archive entry. */
 300
 301   char *acls_a_ptr;         /* Access ACLs for the current archive entry. */
 302   size_t acls_a_len;        /* Access ACLs for the current archive entry. */
 303
 304   char *acls_d_ptr;         /* Default ACLs for the current archive entry. */
 305   size_t acls_d_len;        /* Default ACLs for the current archive entry. */
 306
 307   struct stat   stat;       /* regular filesystem stat */
 308
 309   /* STAT doesn't always have access, data modification, and status
 310      change times in a convenient form, so store them separately.  */
 311   struct timespec atime;
 312   struct timespec mtime;
 313   struct timespec ctime;
 314
 315   off_t archive_file_size;  /* Size of file as stored in the archive.
 316                                Equals stat.st_size for non-sparse files */
 317
 318   bool   is_sparse;         /* Is the file sparse */
 319
 320   /* For sparse files: */
 321   unsigned sparse_major;
 322   unsigned sparse_minor;
 323   size_t sparse_map_avail;  /* Index to the first unused element in
 324                                sparse_map array. Zero if the file is
 325                                not sparse */
 326   size_t sparse_map_size;   /* Size of the sparse map */
 327   struct sp_array *sparse_map;
 328
 329   off_t real_size;          /* The real size of sparse file */
 330   bool  real_size_set;      /* True when GNU.sparse.realsize is set in
 331                                archived file */
 332
 333   bool  sparse_name_done;   /* Set to true if 'GNU.sparse.name' header was
 334                                processed pax header parsing.  Following 'path'
 335                                header (lower priority) will be ignored. */
 336
 337   size_t xattr_map_size;   /* Size of the xattr map */
 338   struct xattr_array *xattr_map;
 339
 340   /* Extended headers */
 341   struct xheader xhdr;
 342
 343   /* For dumpdirs */
 344   bool is_dumpdir;          /* Is the member a dumpdir? */
 345   bool skipped;             /* The member contents is already read
 346                                (for GNUTYPE_DUMPDIR) */
 347   char *dumpdir;            /* Contents of the dump directory */
 348
 349   /* Parent directory, if creating an archive.  This is null if the
 350      file is at the top level.  */
 351   struct tar_stat_info *parent;
 352
 353   /* Directory stream.  If this is not null, it is in control of FD,
 354      and should be closed instead of FD.  */
 355   DIR *dirstream;
 356
 357   /* File descriptor, if creating an archive, and if a directory or a
 358      regular file or a contiguous file.
 359
 360      It is zero if no file descriptor is available, either because it
 361      was never needed or because it was open and then closed to
 362      conserve on file descriptors.  (Standard input is never used
 363      here, so zero cannot be a valid file descriptor.)
 364
 365      It is negative if it could not be reopened after it was closed.
 366      Negate it to find out what errno was when the reopen failed.  */
 367   int fd;
 368
 369   /* Exclusion list */
 370   struct exclist *exclude_list;
 371 };
 372
 373 union block
 374 {
 375   char buffer[BLOCKSIZE];
 376   struct posix_header header;
 377   struct star_header star_header;
 378   struct oldgnu_header oldgnu_header;
 379   struct sparse_header sparse_header;
 380   struct star_in_header star_in_header;
 381   struct star_ext_header star_ext_header;
 382 };