source: MondoRescue/branches/stable/mindi-busybox/libbb/copy_file.c

/* vi: set sw=4 ts=4: */
/*
 * Mini copy_file implementation for busybox
 *
 * Copyright (C) 2001 by Matt Kraai <kraai@alumni.carnegiemellon.edu>
 * SELinux support by Yuichi Nakamura <ynakam@hitachisoft.jp>
 *
 * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
 *
 */

#include "libbb.h"

// POSIX: if exists and -i, ask (w/o -i assume yes).
// Then open w/o EXCL (yes, not unlink!).
// If open still fails and -f, try unlink, then try open again.
// Result: a mess:
// If dest is a softlink, we overwrite softlink's destination!
// (or fail, if it points to dir/nonexistent location/etc).
// This is strange, but POSIX-correct.
// coreutils cp has --remove-destination to override this...
//
// NB: we have special code which still allows for "cp file /dev/node"
// to work POSIX-ly (the only realistic case where it makes sense)

#define DO_POSIX_CP 0  /* 1 - POSIX behavior, 0 - safe behavior */

// errno must be set to relevant value ("why we cannot create dest?")
// for POSIX mode to give reasonable error message
static int ask_and_unlink(const char *dest, int flags)
{
#if DO_POSIX_CP
    if (!(flags & (FILEUTILS_FORCE|FILEUTILS_INTERACTIVE))) {
        // Either it exists, or the *path* doesnt exist
        bb_perror_msg("cannot create '%s'", dest);
        return -1;
    }
#endif
    // If !DO_POSIX_CP, act as if -f is always in effect - we don't want
    // "cannot create" msg, we want unlink to be done (silently unless -i).

    // TODO: maybe we should do it only if ctty is present?
    if (flags & FILEUTILS_INTERACTIVE) {
        // We would not do POSIX insanity. -i asks,
        // then _unlinks_ the offender. Presto.
        // (No "opening without O_EXCL", no "unlink only if -f")
        // Or else we will end up having 3 open()s!
        fprintf(stderr, "%s: overwrite '%s'? ", applet_name, dest);
        if (!bb_ask_confirmation())
            return 0; // not allowed to overwrite
    }
    if (unlink(dest) < 0) {
        bb_perror_msg("cannot remove '%s'", dest);
        return -1; // error
    }
    return 1; // ok (to try again)
}

/* Return:
 * -1 error, copy not made
 *  0 copy is made or user answered "no" in interactive mode
 *    (failures to preserve mode/owner/times are not reported in exit code)
 */
int copy_file(const char *source, const char *dest, int flags)
{
    /* This is a recursive function, try to minimize stack usage */
    /* NB: each struct stat is ~100 bytes */
    struct stat source_stat;
    struct stat dest_stat;
    signed char retval = 0;
    signed char dest_exists = 0;
    signed char ovr;

#define FLAGS_DEREF (flags & FILEUTILS_DEREFERENCE)

    if ((FLAGS_DEREF ? stat : lstat)(source, &source_stat) < 0) {
        // This may be a dangling symlink.
        // Making [sym]links to dangling symlinks works, so...
        if (flags & (FILEUTILS_MAKE_SOFTLINK|FILEUTILS_MAKE_HARDLINK))
            goto make_links;
        bb_perror_msg("cannot stat '%s'", source);
        return -1;
    }

    if (lstat(dest, &dest_stat) < 0) {
        if (errno != ENOENT) {
            bb_perror_msg("cannot stat '%s'", dest);
            return -1;
        }
    } else {
        if (source_stat.st_dev == dest_stat.st_dev
         && source_stat.st_ino == dest_stat.st_ino
        ) {
            bb_error_msg("'%s' and '%s' are the same file", source, dest);
            return -1;
        }
        dest_exists = 1;
    }

#if ENABLE_SELINUX
    if ((flags & FILEUTILS_PRESERVE_SECURITY_CONTEXT) && is_selinux_enabled() > 0) {
        security_context_t con;
        if (lgetfilecon(source, &con) >= 0) {
            if (setfscreatecon(con) < 0) {
                bb_perror_msg("cannot set setfscreatecon %s", con);
                freecon(con);
                return -1;
            }
        } else if (errno == ENOTSUP || errno == ENODATA) {
            setfscreatecon_or_die(NULL);
        } else {
            bb_perror_msg("cannot lgetfilecon %s", source);
            return -1;
        }
    }
#endif

    if (S_ISDIR(source_stat.st_mode)) {
        DIR *dp;
        const char *tp;
        struct dirent *d;
        mode_t saved_umask = 0;

        if (!(flags & FILEUTILS_RECUR)) {
            bb_error_msg("omitting directory '%s'", source);
            return -1;
        }

        /* Did we ever create source ourself before? */
        tp = is_in_ino_dev_hashtable(&source_stat);
        if (tp) {
            /* We did! it's a recursion! man the lifeboats... */
            bb_error_msg("recursion detected, omitting directory '%s'",
                    source);
            return -1;
        }

        /* Create DEST */
        if (dest_exists) {
            if (!S_ISDIR(dest_stat.st_mode)) {
                bb_error_msg("target '%s' is not a directory", dest);
                return -1;
            }
            /* race here: user can substitute a symlink between
             * this check and actual creation of files inside dest */
        } else {
            mode_t mode;
            saved_umask = umask(0);

            mode = source_stat.st_mode;
            if (!(flags & FILEUTILS_PRESERVE_STATUS))
                mode = source_stat.st_mode & ~saved_umask;
            /* Allow owner to access new dir (at least for now) */
            mode |= S_IRWXU;
            if (mkdir(dest, mode) < 0) {
                umask(saved_umask);
                bb_perror_msg("cannot create directory '%s'", dest);
                return -1;
            }
            umask(saved_umask);
            /* need stat info for add_to_ino_dev_hashtable */
            if (lstat(dest, &dest_stat) < 0) {
                bb_perror_msg("cannot stat '%s'", dest);
                return -1;
            }
        }
        /* remember (dev,inode) of each created dir.
         * NULL: name is not remembered */
        add_to_ino_dev_hashtable(&dest_stat, NULL);

        /* Recursively copy files in SOURCE */
        dp = opendir(source);
        if (dp == NULL) {
            retval = -1;
            goto preserve_mode_ugid_time;
        }

        while ((d = readdir(dp)) != NULL) {
            char *new_source, *new_dest;

            new_source = concat_subpath_file(source, d->d_name);
            if (new_source == NULL)
                continue;
            new_dest = concat_path_file(dest, d->d_name);
            if (copy_file(new_source, new_dest, flags) < 0)
                retval = -1;
            free(new_source);
            free(new_dest);
        }
        closedir(dp);

        if (!dest_exists
         && chmod(dest, source_stat.st_mode & ~saved_umask) < 0
        ) {
            bb_perror_msg("cannot preserve %s of '%s'", "permissions", dest);
            /* retval = -1; - WRONG! copy *WAS* made */
        }
        goto preserve_mode_ugid_time;
    }

    if (flags & (FILEUTILS_MAKE_SOFTLINK|FILEUTILS_MAKE_HARDLINK)) {
        int (*lf)(const char *oldpath, const char *newpath);
 make_links:
        // Hmm... maybe
        // if (DEREF && MAKE_SOFTLINK) source = realpath(source) ?
        // (but realpath returns NULL on dangling symlinks...)
        lf = (flags & FILEUTILS_MAKE_SOFTLINK) ? symlink : link;
        if (lf(source, dest) < 0) {
            ovr = ask_and_unlink(dest, flags);
            if (ovr <= 0)
                return ovr;
            if (lf(source, dest) < 0) {
                bb_perror_msg("cannot create link '%s'", dest);
                return -1;
            }
        }
        /* _Not_ jumping to preserve_mode_ugid_time:
         * hard/softlinks don't have those */
        return 0;
    }

    if (S_ISREG(source_stat.st_mode)
     /* DEREF uses stat, which never returns S_ISLNK() == true. */
     /* || (FLAGS_DEREF && S_ISLNK(source_stat.st_mode)) */
    ) {
        int src_fd;
        int dst_fd;

        if (ENABLE_FEATURE_PRESERVE_HARDLINKS && !FLAGS_DEREF) {
            const char *link_target;
            link_target = is_in_ino_dev_hashtable(&source_stat);
            if (link_target) {
                if (link(link_target, dest) < 0) {
                    ovr = ask_and_unlink(dest, flags);
                    if (ovr <= 0)
                        return ovr;
                    if (link(link_target, dest) < 0) {
                        bb_perror_msg("cannot create link '%s'", dest);
                        return -1;
                    }
                }
                return 0;
            }
            add_to_ino_dev_hashtable(&source_stat, dest);
        }

        src_fd = open_or_warn(source, O_RDONLY);
        if (src_fd < 0)
            return -1;

        /* POSIX way is a security problem versus symlink attacks,
         * we do it only for non-symlinks, and only for non-recursive,
         * non-interactive cp. NB: it is still racy
         * for "cp file /home/bad_user/file" case
         * (user can rm file and create a link to /etc/passwd) */
        if (DO_POSIX_CP
         || (dest_exists && !(flags & (FILEUTILS_RECUR|FILEUTILS_INTERACTIVE))
             && !S_ISLNK(dest_stat.st_mode))
        ) {
            dst_fd = open(dest, O_WRONLY|O_CREAT|O_TRUNC, source_stat.st_mode);
        } else  /* safe way: */
            dst_fd = open(dest, O_WRONLY|O_CREAT|O_EXCL, source_stat.st_mode);
        if (dst_fd == -1) {
            ovr = ask_and_unlink(dest, flags);
            if (ovr <= 0) {
                close(src_fd);
                return ovr;
            }
            /* It shouldn't exist. If it exists, do not open (symlink attack?) */
            dst_fd = open3_or_warn(dest, O_WRONLY|O_CREAT|O_EXCL, source_stat.st_mode);
            if (dst_fd < 0) {
                close(src_fd);
                return -1;
            }
        }

#if ENABLE_SELINUX
        if (((flags & FILEUTILS_PRESERVE_SECURITY_CONTEXT)
            || (flags & FILEUTILS_SET_SECURITY_CONTEXT))
         && is_selinux_enabled() > 0
        ) {
            security_context_t con;
            if (getfscreatecon(&con) == -1) {
                bb_perror_msg("getfscreatecon");
                return -1;
            }
            if (con) {
                if (setfilecon(dest, con) == -1) {
                    bb_perror_msg("setfilecon:%s,%s", dest, con);
                    freecon(con);
                    return -1;
                }
                freecon(con);
            }
        }
#endif
        if (bb_copyfd_eof(src_fd, dst_fd) == -1)
            retval = -1;
        /* Ok, writing side I can understand... */
        if (close(dst_fd) < 0) {
            bb_perror_msg("cannot close '%s'", dest);
            retval = -1;
        }
        /* ...but read size is already checked by bb_copyfd_eof */
        close(src_fd);
        goto preserve_mode_ugid_time;
    }

    /* Source is a symlink or a special file */
    /* We are lazy here, a bit lax with races... */
    if (dest_exists) {
        errno = EEXIST;
        ovr = ask_and_unlink(dest, flags);
        if (ovr <= 0)
            return ovr;
    }
    if (S_ISLNK(source_stat.st_mode)) {
        char *lpath = xmalloc_readlink_or_warn(source);
        if (lpath) {
            int r = symlink(lpath, dest);
            free(lpath);
            if (r < 0) {
                bb_perror_msg("cannot create symlink '%s'", dest);
                return -1;
            }
            if (flags & FILEUTILS_PRESERVE_STATUS)
                if (lchown(dest, source_stat.st_uid, source_stat.st_gid) < 0)
                    bb_perror_msg("cannot preserve %s of '%s'", "ownership", dest);
        }
        /* _Not_ jumping to preserve_mode_ugid_time:
         * symlinks don't have those */
        return 0;
    }
    if (S_ISBLK(source_stat.st_mode) || S_ISCHR(source_stat.st_mode)
     || S_ISSOCK(source_stat.st_mode) || S_ISFIFO(source_stat.st_mode)
    ) {
        if (mknod(dest, source_stat.st_mode, source_stat.st_rdev) < 0) {
            bb_perror_msg("cannot create '%s'", dest);
            return -1;
        }
    } else {
        bb_error_msg("unrecognized file '%s' with mode %x", source, source_stat.st_mode);
        return -1;
    }

 preserve_mode_ugid_time:

    if (flags & FILEUTILS_PRESERVE_STATUS
    /* Cannot happen: */
    /* && !(flags & (FILEUTILS_MAKE_SOFTLINK|FILEUTILS_MAKE_HARDLINK)) */
    ) {
        struct utimbuf times;

        times.actime = source_stat.st_atime;
        times.modtime = source_stat.st_mtime;
        /* BTW, utimes sets usec-precision time - just FYI */
        if (utime(dest, &times) < 0)
            bb_perror_msg("cannot preserve %s of '%s'", "times", dest);
        if (chown(dest, source_stat.st_uid, source_stat.st_gid) < 0) {
            source_stat.st_mode &= ~(S_ISUID | S_ISGID);
            bb_perror_msg("cannot preserve %s of '%s'", "ownership", dest);
        }
        if (chmod(dest, source_stat.st_mode) < 0)
            bb_perror_msg("cannot preserve %s of '%s'", "permissions", dest);
    }

    return retval;
}