1 /* GNU tar Archive Format description. 2 3 Copyright 1988-2021 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 */ 244 245 246 /* 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 }; 383