Changes for kernel and Busybox

[tomato.git] / release / src / router / 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 source tree.
 */
#include "libbb.h"

// FEATURE_NON_POSIX_CP:
//
// 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 (sym)link, we overwrite link 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...

/* Called if open of destination, link creation etc fails.
 * errno must be set to relevant value ("why we cannot create dest?")
 * to give reasonable error message */
static int ask_and_unlink(const char *dest, int flags)
{
        int e = errno;

#if !ENABLE_FEATURE_NON_POSIX_CP
        if (!(flags & (FILEUTILS_FORCE|FILEUTILS_INTERACTIVE))) {
                /* Either it exists, or the *path* doesnt exist */
                bb_perror_msg("can't create '%s'", dest);
                return -1;
        }
#endif
        // else: act as if -f is always in effect.
        // We don't want "can't create" msg, we want unlink to be done
        // (silently unless -i). Why? POSIX cp usually succeeds with
        // O_TRUNC open of existing file, and user is left ignorantly happy.
        // With above block unconditionally enabled, non-POSIX cp
        // will complain a lot more than POSIX one.

        /* 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) {
#if ENABLE_FEATURE_VERBOSE_CP_MESSAGE
                if (e == errno && e == ENOENT) {
                        /* e == ENOTDIR is similar: path has non-dir component,
                         * but in this case we don't even reach copy_file() */
                        bb_error_msg("can't create '%s': Path does not exist", dest);
                        return -1; /* error */
                }
#endif
                errno = e; /* do not use errno from unlink */
                bb_perror_msg("can't create '%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 FAST_FUNC 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;
        smallint retval = 0;
        smallint dest_exists = 0;
        smallint ovr;

/* Inverse of cp -d ("cp without -d") */
#define FLAGS_DEREF (flags & (FILEUTILS_DEREFERENCE + FILEUTILS_DEREFERENCE_L0))

        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("can't stat '%s'", source);
                return -1;
        }

        if (lstat(dest, &dest_stat) < 0) {
                if (errno != ENOENT) {
                        bb_perror_msg("can't 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("can't set setfscreatecon %s", con);
                                freecon(con);
                                return -1;
                        }
                } else if (errno == ENOTSUP || errno == ENODATA) {
                        setfscreatecon_or_die(NULL);
                } else {
                        bb_perror_msg("can't 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;
                }

                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 {
                        /* Create DEST */
                        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("can't 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("can't 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 & ~FILEUTILS_DEREFERENCE_L0) < 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("can't 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("can't create link '%s'", dest);
                                return -1;
                        }
                }
                /* _Not_ jumping to preserve_mode_ugid_time:
                 * (sym)links don't have those */
                return 0;
        }

        if (/* "cp thing1 thing2" without -R: just open and read() from thing1 */
            !(flags & FILEUTILS_RECUR)
            /* "cp [-opts] regular_file thing2" */
         || S_ISREG(source_stat.st_mode)
         /* DEREF uses stat, which never returns S_ISLNK() == true.
          * So the below is never true: */
         /* || (FLAGS_DEREF && S_ISLNK(source_stat.st_mode)) */
        ) {
                int src_fd;
                int dst_fd;
                mode_t new_mode;

                if (!FLAGS_DEREF && S_ISLNK(source_stat.st_mode)) {
                        /* "cp -d symlink dst": create a link */
                        goto dont_cat;
                }

                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("can't 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;

                /* Do not try to open with weird mode fields */
                new_mode = source_stat.st_mode;
                if (!S_ISREG(source_stat.st_mode))
                        new_mode = 0666;

                // POSIX way is a security problem versus (sym)link attacks
                if (!ENABLE_FEATURE_NON_POSIX_CP) {
                        dst_fd = open(dest, O_WRONLY|O_CREAT|O_TRUNC, new_mode);
                } else { /* safe way: */
                        dst_fd = open(dest, O_WRONLY|O_CREAT|O_EXCL, new_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, new_mode);
                        if (dst_fd < 0) {
                                close(src_fd);
                                return -1;
                        }
                }

#if ENABLE_SELINUX
                if ((flags & (FILEUTILS_PRESERVE_SECURITY_CONTEXT|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;
                /* Careful with writing... */
                if (close(dst_fd) < 0) {
                        bb_perror_msg("error writing to '%s'", dest);
                        retval = -1;
                }
                /* ...but read size is already checked by bb_copyfd_eof */
                close(src_fd);
                /* "cp /dev/something new_file" should not
                 * copy mode of /dev/something */
                if (!S_ISREG(source_stat.st_mode))
                        return retval;
                goto preserve_mode_ugid_time;
        }
 dont_cat:

        /* 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("can't 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("can't 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("can't 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 timeval times[2];

                times[1].tv_sec = times[0].tv_sec = source_stat.st_mtime;
                times[1].tv_usec = times[0].tv_usec = 0;
                /* BTW, utimes sets usec-precision time - just FYI */
                if (utimes(dest, times) < 0)
                        bb_perror_msg("can't 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("can't preserve %s of '%s'", "ownership", dest);
                }
                if (chmod(dest, source_stat.st_mode) < 0)
                        bb_perror_msg("can't preserve %s of '%s'", "permissions", dest);
        }

        return retval;
}