LXR busybox/libbb/copy

   1/* vi: set sw=4 ts=4: */
   2/*
   3 * Mini copy_file implementation for busybox
   4 *
   5 * Copyright (C) 2001 by Matt Kraai <kraai@alumni.carnegiemellon.edu>
   6 * SELinux support by Yuichi Nakamura <ynakam@hitachisoft.jp>
   7 *
   8 * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
   9 */
  10#include "libbb.h"
  11
  12// FEATURE_NON_POSIX_CP:
  13//
  14// POSIX: if exists and -i, ask (w/o -i assume yes).
  15// Then open w/o EXCL (yes, not unlink!).
  16// If open still fails and -f, try unlink, then try open again.
  17// Result: a mess:
  18// If dest is a (sym)link, we overwrite link destination!
  19// (or fail, if it points to dir/nonexistent location/etc).
  20// This is strange, but POSIX-correct.
  21// coreutils cp has --remove-destination to override this...
  22
  23/* Called if open of destination, link creation etc fails.
  24 * errno must be set to relevant value ("why we cannot create dest?")
  25 * to give reasonable error message */
  26static int ask_and_unlink(const char *dest, int flags)
  27{
  28        int e = errno;
  29
  30#if !ENABLE_FEATURE_NON_POSIX_CP
  31        if (!(flags & (FILEUTILS_FORCE|FILEUTILS_INTERACTIVE))) {
  32                /* Either it exists, or the *path* doesnt exist */
  33                bb_perror_msg("can't create '%s'", dest);
  34                return -1;
  35        }
  36#endif
  37        // else: act as if -f is always in effect.
  38        // We don't want "can't create" msg, we want unlink to be done
  39        // (silently unless -i). Why? POSIX cp usually succeeds with
  40        // O_TRUNC open of existing file, and user is left ignorantly happy.
  41        // With above block unconditionally enabled, non-POSIX cp
  42        // will complain a lot more than POSIX one.
  43
  44        /* TODO: maybe we should do it only if ctty is present? */
  45        if (flags & FILEUTILS_INTERACTIVE) {
  46                // We would not do POSIX insanity. -i asks,
  47                // then _unlinks_ the offender. Presto.
  48                // (No "opening without O_EXCL", no "unlink only if -f")
  49                // Or else we will end up having 3 open()s!
  50                fprintf(stderr, "%s: overwrite '%s'? ", applet_name, dest);
  51                if (!bb_ask_confirmation())
  52                        return 0; /* not allowed to overwrite */
  53        }
  54        if (unlink(dest) < 0) {
  55#if ENABLE_FEATURE_VERBOSE_CP_MESSAGE
  56                if (e == errno && e == ENOENT) {
  57                        /* e == ENOTDIR is similar: path has non-dir component,
  58                         * but in this case we don't even reach copy_file() */
  59                        bb_error_msg("can't create '%s': Path does not exist", dest);
  60                        return -1; /* error */
  61                }
  62#endif
  63                errno = e; /* do not use errno from unlink */
  64                bb_perror_msg("can't create '%s'", dest);
  65                return -1; /* error */
  66        }
  67        return 1; /* ok (to try again) */
  68}
  69
  70/* Return:
  71 * -1 error, copy not made
  72 *  0 copy is made or user answered "no" in interactive mode
  73 *    (failures to preserve mode/owner/times are not reported in exit code)
  74 */
  75int FAST_FUNC copy_file(const char *source, const char *dest, int flags)
  76{
  77        /* This is a recursive function, try to minimize stack usage */
  78        /* NB: each struct stat is ~100 bytes */
  79        struct stat source_stat;
  80        struct stat dest_stat;
  81        signed char retval = 0;
  82        signed char dest_exists = 0;
  83        signed char ovr;
  84
  85/* Inverse of cp -d ("cp without -d") */
  86#define FLAGS_DEREF (flags & (FILEUTILS_DEREFERENCE + FILEUTILS_DEREFERENCE_L0))
  87
  88        if ((FLAGS_DEREF ? stat : lstat)(source, &source_stat) < 0) {
  89                /* This may be a dangling symlink.
  90                 * Making [sym]links to dangling symlinks works, so... */
  91                if (flags & (FILEUTILS_MAKE_SOFTLINK|FILEUTILS_MAKE_HARDLINK))
  92                        goto make_links;
  93                bb_perror_msg("can't stat '%s'", source);
  94                return -1;
  95        }
  96
  97        if (lstat(dest, &dest_stat) < 0) {
  98                if (errno != ENOENT) {
  99                        bb_perror_msg("can't stat '%s'", dest);
 100                        return -1;
 101                }
 102        } else {
 103                if (source_stat.st_dev == dest_stat.st_dev
 104                 && source_stat.st_ino == dest_stat.st_ino
 105                ) {
 106                        bb_error_msg("'%s' and '%s' are the same file", source, dest);
 107                        return -1;
 108                }
 109                dest_exists = 1;
 110        }
 111
 112#if ENABLE_SELINUX
 113        if ((flags & FILEUTILS_PRESERVE_SECURITY_CONTEXT) && is_selinux_enabled() > 0) {
 114                security_context_t con;
 115                if (lgetfilecon(source, &con) >= 0) {
 116                        if (setfscreatecon(con) < 0) {
 117                                bb_perror_msg("can't set setfscreatecon %s", con);
 118                                freecon(con);
 119                                return -1;
 120                        }
 121                } else if (errno == ENOTSUP || errno == ENODATA) {
 122                        setfscreatecon_or_die(NULL);
 123                } else {
 124                        bb_perror_msg("can't lgetfilecon %s", source);
 125                        return -1;
 126                }
 127        }
 128#endif
 129
 130        if (S_ISDIR(source_stat.st_mode)) {
 131                DIR *dp;
 132                const char *tp;
 133                struct dirent *d;
 134                mode_t saved_umask = 0;
 135
 136                if (!(flags & FILEUTILS_RECUR)) {
 137                        bb_error_msg("omitting directory '%s'", source);
 138                        return -1;
 139                }
 140
 141                /* Did we ever create source ourself before? */
 142                tp = is_in_ino_dev_hashtable(&source_stat);
 143                if (tp) {
 144                        /* We did! it's a recursion! man the lifeboats... */
 145                        bb_error_msg("recursion detected, omitting directory '%s'",
 146                                        source);
 147                        return -1;
 148                }
 149
 150                /* Create DEST */
 151                if (dest_exists) {
 152                        if (!S_ISDIR(dest_stat.st_mode)) {
 153                                bb_error_msg("target '%s' is not a directory", dest);
 154                                return -1;
 155                        }
 156                        /* race here: user can substitute a symlink between
 157                         * this check and actual creation of files inside dest */
 158                } else {
 159                        mode_t mode;
 160                        saved_umask = umask(0);
 161
 162                        mode = source_stat.st_mode;
 163                        if (!(flags & FILEUTILS_PRESERVE_STATUS))
 164                                mode = source_stat.st_mode & ~saved_umask;
 165                        /* Allow owner to access new dir (at least for now) */
 166                        mode |= S_IRWXU;
 167                        if (mkdir(dest, mode) < 0) {
 168                                umask(saved_umask);
 169                                bb_perror_msg("can't create directory '%s'", dest);
 170                                return -1;
 171                        }
 172                        umask(saved_umask);
 173                        /* need stat info for add_to_ino_dev_hashtable */
 174                        if (lstat(dest, &dest_stat) < 0) {
 175                                bb_perror_msg("can't stat '%s'", dest);
 176                                return -1;
 177                        }
 178                }
 179                /* remember (dev,inode) of each created dir.
 180                 * NULL: name is not remembered */
 181                add_to_ino_dev_hashtable(&dest_stat, NULL);
 182
 183                /* Recursively copy files in SOURCE */
 184                dp = opendir(source);
 185                if (dp == NULL) {
 186                        retval = -1;
 187                        goto preserve_mode_ugid_time;
 188                }
 189
 190                while ((d = readdir(dp)) != NULL) {
 191                        char *new_source, *new_dest;
 192
 193                        new_source = concat_subpath_file(source, d->d_name);
 194                        if (new_source == NULL)
 195                                continue;
 196                        new_dest = concat_path_file(dest, d->d_name);
 197                        if (copy_file(new_source, new_dest, flags & ~FILEUTILS_DEREFERENCE_L0) < 0)
 198                                retval = -1;
 199                        free(new_source);
 200                        free(new_dest);
 201                }
 202                closedir(dp);
 203
 204                if (!dest_exists
 205                 && chmod(dest, source_stat.st_mode & ~saved_umask) < 0
 206                ) {
 207                        bb_perror_msg("can't preserve %s of '%s'", "permissions", dest);
 208                        /* retval = -1; - WRONG! copy *WAS* made */
 209                }
 210                goto preserve_mode_ugid_time;
 211        }
 212
 213        if (flags & (FILEUTILS_MAKE_SOFTLINK|FILEUTILS_MAKE_HARDLINK)) {
 214                int (*lf)(const char *oldpath, const char *newpath);
 215 make_links:
 216                /* Hmm... maybe
 217                 * if (DEREF && MAKE_SOFTLINK) source = realpath(source) ?
 218                 * (but realpath returns NULL on dangling symlinks...) */
 219                lf = (flags & FILEUTILS_MAKE_SOFTLINK) ? symlink : link;
 220                if (lf(source, dest) < 0) {
 221                        ovr = ask_and_unlink(dest, flags);
 222                        if (ovr <= 0)
 223                                return ovr;
 224                        if (lf(source, dest) < 0) {
 225                                bb_perror_msg("can't create link '%s'", dest);
 226                                return -1;
 227                        }
 228                }
 229                /* _Not_ jumping to preserve_mode_ugid_time:
 230                 * (sym)links don't have those */
 231                return 0;
 232        }
 233
 234        if (/* "cp thing1 thing2" without -R: just open and read() from thing1 */
 235            !(flags & FILEUTILS_RECUR)
 236            /* "cp [-opts] regular_file thing2" */
 237         || S_ISREG(source_stat.st_mode)
 238         /* DEREF uses stat, which never returns S_ISLNK() == true.
 239          * So the below is never true: */
 240         /* || (FLAGS_DEREF && S_ISLNK(source_stat.st_mode)) */
 241        ) {
 242                int src_fd;
 243                int dst_fd;
 244                mode_t new_mode;
 245
 246                if (!FLAGS_DEREF && S_ISLNK(source_stat.st_mode)) {
 247                        /* "cp -d symlink dst": create a link */
 248                        goto dont_cat;
 249                }
 250
 251                if (ENABLE_FEATURE_PRESERVE_HARDLINKS && !FLAGS_DEREF) {
 252                        const char *link_target;
 253                        link_target = is_in_ino_dev_hashtable(&source_stat);
 254                        if (link_target) {
 255                                if (link(link_target, dest) < 0) {
 256                                        ovr = ask_and_unlink(dest, flags);
 257                                        if (ovr <= 0)
 258                                                return ovr;
 259                                        if (link(link_target, dest) < 0) {
 260                                                bb_perror_msg("can't create link '%s'", dest);
 261                                                return -1;
 262                                        }
 263                                }
 264                                return 0;
 265                        }
 266                        add_to_ino_dev_hashtable(&source_stat, dest);
 267                }
 268
 269                src_fd = open_or_warn(source, O_RDONLY);
 270                if (src_fd < 0)
 271                        return -1;
 272
 273                /* Do not try to open with weird mode fields */
 274                new_mode = source_stat.st_mode;
 275                if (!S_ISREG(source_stat.st_mode))
 276                        new_mode = 0666;
 277
 278                // POSIX way is a security problem versus (sym)link attacks
 279                if (!ENABLE_FEATURE_NON_POSIX_CP) {
 280                        dst_fd = open(dest, O_WRONLY|O_CREAT|O_TRUNC, new_mode);
 281                } else { /* safe way: */
 282                        dst_fd = open(dest, O_WRONLY|O_CREAT|O_EXCL, new_mode);
 283                }
 284                if (dst_fd == -1) {
 285                        ovr = ask_and_unlink(dest, flags);
 286                        if (ovr <= 0) {
 287                                close(src_fd);
 288                                return ovr;
 289                        }
 290                        /* It shouldn't exist. If it exists, do not open (symlink attack?) */
 291                        dst_fd = open3_or_warn(dest, O_WRONLY|O_CREAT|O_EXCL, new_mode);
 292                        if (dst_fd < 0) {
 293                                close(src_fd);
 294                                return -1;
 295                        }
 296                }
 297
 298#if ENABLE_SELINUX
 299                if ((flags & (FILEUTILS_PRESERVE_SECURITY_CONTEXT|FILEUTILS_SET_SECURITY_CONTEXT))
 300                 && is_selinux_enabled() > 0
 301                ) {
 302                        security_context_t con;
 303                        if (getfscreatecon(&con) == -1) {
 304                                bb_perror_msg("getfscreatecon");
 305                                return -1;
 306                        }
 307                        if (con) {
 308                                if (setfilecon(dest, con) == -1) {
 309                                        bb_perror_msg("setfilecon:%s,%s", dest, con);
 310                                        freecon(con);
 311                                        return -1;
 312                                }
 313                                freecon(con);
 314                        }
 315                }
 316#endif
 317                if (bb_copyfd_eof(src_fd, dst_fd) == -1)
 318                        retval = -1;
 319                /* Careful with writing... */
 320                if (close(dst_fd) < 0) {
 321                        bb_perror_msg("error writing to '%s'", dest);
 322                        retval = -1;
 323                }
 324                /* ...but read size is already checked by bb_copyfd_eof */
 325                close(src_fd);
 326                /* "cp /dev/something new_file" should not
 327                 * copy mode of /dev/something */
 328                if (!S_ISREG(source_stat.st_mode))
 329                        return retval;
 330                goto preserve_mode_ugid_time;
 331        }
 332 dont_cat:
 333
 334        /* Source is a symlink or a special file */
 335        /* We are lazy here, a bit lax with races... */
 336        if (dest_exists) {
 337                errno = EEXIST;
 338                ovr = ask_and_unlink(dest, flags);
 339                if (ovr <= 0)
 340                        return ovr;
 341        }
 342        if (S_ISLNK(source_stat.st_mode)) {
 343                char *lpath = xmalloc_readlink_or_warn(source);
 344                if (lpath) {
 345                        int r = symlink(lpath, dest);
 346                        free(lpath);
 347                        if (r < 0) {
 348                                bb_perror_msg("can't create symlink '%s'", dest);
 349                                return -1;
 350                        }
 351                        if (flags & FILEUTILS_PRESERVE_STATUS)
 352                                if (lchown(dest, source_stat.st_uid, source_stat.st_gid) < 0)
 353                                        bb_perror_msg("can't preserve %s of '%s'", "ownership", dest);
 354                }
 355                /* _Not_ jumping to preserve_mode_ugid_time:
 356                 * symlinks don't have those */
 357                return 0;
 358        }
 359        if (S_ISBLK(source_stat.st_mode) || S_ISCHR(source_stat.st_mode)
 360         || S_ISSOCK(source_stat.st_mode) || S_ISFIFO(source_stat.st_mode)
 361        ) {
 362                if (mknod(dest, source_stat.st_mode, source_stat.st_rdev) < 0) {
 363                        bb_perror_msg("can't create '%s'", dest);
 364                        return -1;
 365                }
 366        } else {
 367                bb_error_msg("unrecognized file '%s' with mode %x", source, source_stat.st_mode);
 368                return -1;
 369        }
 370
 371 preserve_mode_ugid_time:
 372
 373        if (flags & FILEUTILS_PRESERVE_STATUS
 374        /* Cannot happen: */
 375        /* && !(flags & (FILEUTILS_MAKE_SOFTLINK|FILEUTILS_MAKE_HARDLINK)) */
 376        ) {
 377                struct timeval times[2];
 378
 379                times[1].tv_sec = times[0].tv_sec = source_stat.st_mtime;
 380                times[1].tv_usec = times[0].tv_usec = 0;
 381                /* BTW, utimes sets usec-precision time - just FYI */
 382                if (utimes(dest, times) < 0)
 383                        bb_perror_msg("can't preserve %s of '%s'", "times", dest);
 384                if (chown(dest, source_stat.st_uid, source_stat.st_gid) < 0) {
 385                        source_stat.st_mode &= ~(S_ISUID | S_ISGID);
 386                        bb_perror_msg("can't preserve %s of '%s'", "ownership", dest);
 387                }
 388                if (chmod(dest, source_stat.st_mode) < 0)
 389                        bb_perror_msg("can't preserve %s of '%s'", "permissions", dest);
 390        }
 391
 392        return retval;
 393}
 394