file.c

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/*
 *   This library is free software; you can redistribute it and/or
 *   modify it under the terms of the GNU Lesser General Public
 *   License as published by the Free Software Foundation; either
 *   version 2.1 of the License, or (at your option) any later version.
 *
 *   This library is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 *   Lesser General Public License for more details.
 *
 *   You should have received a copy of the GNU Lesser General Public
 *   License along with this library; if not, write to the Free Software
 *   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA
 */
 
/** Various miscellaneous functions to manipulate files and paths
 *
 * @file src/lib/util/file.c
 *
 * @copyright 2019 The FreeRADIUS project
 * @copyright 2019 Arran Cudbard-Bell (a.cudbardb@freeradius.org)
 */
RCSID("$Id: 182598e2468327ab6cb849fb18fd840674685735 $")
 
#include <sys/param.h>
#include <fcntl.h>
#include <stdio.h>
#include <sys/stat.h>
 
#include <freeradius-devel/util/file.h>
#include <freeradius-devel/util/strerror.h>
#include <freeradius-devel/util/syserror.h>
#include <freeradius-devel/util/value.h>
 
/** Callback for the common case of chown() of the directory.
 *
 */
int fr_mkdir_chown(int fd, char const *path, void *uctx)
{
        fr_mkdir_chown_t const *ctx = uctx;
 
        if ((ctx->uid == (uid_t) -1) && (ctx->gid == (gid_t) -1)) return 0;
 
        if (fchown(fd, ctx->uid, ctx->gid) < 0) {
                fr_strerror_printf("Failed changing ownership on directory \"%s\": %s",
                                   path, fr_syserror(errno));
                return -1;
        }
 
        return 0;
}
 
 
static ssize_t _fr_mkdir(int *fd_out, char *start, char *path, mode_t mode, fr_mkdir_func_t func, void *uctx)
{
        int             ret, fd;
        char            *p;
 
        /*
         *      Try to make the path.  If it exists, chmod it.
         *      If a path doesn't exist, that's OK.  Otherwise
         *      return with an error.
         *
         *      Directories permissions are initially set so
         *      that only we should have access. This prevents
         *      an attacker removing them and swapping them
         *      out for a link to somewhere else.
         *      We change them to the correct permissions later.
         */
        ret = mkdir(path, 0700);
        if (ret >= 0) {
                fd = open(path, O_DIRECTORY);
                if (fd < 0) {
                        fr_strerror_printf("Failed opening directory we created: %s",
                                           fr_syserror(errno));
                mkdir_error:
                        p = strrchr(path, FR_DIR_SEP);
                        if (!p) return start - path;
 
                        return start - p;
                }
 
                if (fchmod(fd, mode) < 0) {
                        fr_strerror_printf("Failed setting permissions on directory "
                                           "we created: %s", fr_syserror(errno));
                        close(fd);
                        goto mkdir_error;
                }
                *fd_out = fd;
                return strlen(start);
        }
 
        /*
         *      EEXIST is only OK when we're calling mkdir on the
         *      whole path, and it exists which should have been
         *      caught by fr_mkdir before calling this function.
         *
         *      Unless we're running in an environment with multiple
         *      processes, in which case EEXIST means that another
         *      process created this directory in between our check
         *      and our creation.
         */
        if (errno == EEXIST) {
                fd = open(path, O_DIRECTORY);
                if (fd < 0) {
                        fr_strerror_printf("Failed opening existing directory: %s", fr_syserror(errno));
                        goto mkdir_error;
                }
                *fd_out = fd;
                return strlen(start);
        }
 
        /*
         *      ENOENT means we're trying to create too much path
         *      at once.  Recurse to discover the deepest path
         *      component that already exists.
         */
        if (errno != ENOENT) {
                fr_strerror_printf("Failed creating directory path: %s", fr_syserror(errno));
                goto mkdir_error;
        }
 
        /*
         *      A component in the path doesn't
         *      exist.  Look for the LAST path name.  Try
         *      to create that.  If there's an error, we leave
         *      the path path as the one at which the
         *      error occurred.
         */
        p = strrchr(path, FR_DIR_SEP);
        if (!p || (p == path)) return start - path;     /* last path component and we've previously failed */
 
        *p = '\0';
        if (_fr_mkdir(fd_out, start, path, mode, func, uctx) <= 0) return start - p;
 
        fr_assert_msg((*fd_out) >= 0, "Logic error - Bad FD %i", *fd_out);
 
        /*
         *      At this point *fd_out, should be an FD
         *      for the containing directory.
         *
         *      Dir may already exist if we're racing
         *      other processes as we do in CI.
         */
        if (mkdirat(*fd_out, p + 1, 0700) < 0) {
                /*
                 *      This is usually because of a race with
                 *      other processes trying to create the
                 *      same directory.
                 */
                if (errno == EEXIST) {
                        fd = openat(*fd_out, p + 1, O_DIRECTORY);
                        if (fd < 0) {
                                fr_strerror_printf_push("Failed opening existing directory path component: %s",
                                                        fr_syserror(errno));
                                goto mkdirat_error;
                        }
                        *p = FR_DIR_SEP;
                        goto done;
                }
 
                fr_strerror_printf_push("Failed creating directory path component: %s", fr_syserror(errno));
 
        mkdirat_error:
                close(*fd_out);
                *fd_out = -1;
                return start - p;
        }
 
        fd = openat(*fd_out, p + 1, O_DIRECTORY);
        if (fd < 0) {
                fr_strerror_printf_push("Failed opening directory we "
                                        "created: %s", fr_syserror(errno));
                goto mkdirat_error;
        }
 
        if (fchmod(fd, mode) < 0) {
                fr_strerror_printf_push("Failed setting permissions on "
                                        "directory we created: %s", fr_syserror(errno));
                goto mkdirat_error;
        }
 
        *p = FR_DIR_SEP;
 
        /*
         *      Call the user function
         */
        if (func && (func(fd, path, uctx) < 0)) {
                fr_strerror_printf_push("Callback failed processing directory \"%s\"", path);
                goto mkdirat_error;
        }
 
        /*
         *      Swap active *fd_out to point to the dir
         *      we just created.
         */
done:
        close(*fd_out);
        *fd_out = fd;
 
        return strlen(start);
}
 
/** Create directories that are missing in the specified path
 *
 * @param[out] fd_out   If not NULL, will contain a file descriptor
 *                      for the deepest path component created.
 * @param[in] path      to populate with directories.
 * @param[in] len       Length of the path string.
 * @param[in] mode      for new directories.
 * @param[in] func      to call each time a new directory is created.
 * @param[in] uctx      to pass to func.
 * @return
 *      - >0 on success.
 *      - <= 0 on failure. Negative offset pointing to the
 *        path separator of the path component that caused the error.
 */
ssize_t fr_mkdir(int *fd_out, char const *path, ssize_t len, mode_t mode, fr_mkdir_func_t func, void *uctx)
{
        char    *our_path;
        int     fd = -1;
        ssize_t slen;
 
        if (len < 0) len = strlen(path);
        if (len == 0) return 0;
 
        /*
         *      Fast path (har har)
         *
         *      Avoids duping the input for the
         *      common case.
         */
        fd = open(path, O_DIRECTORY);
        if (fd >= 0) goto done;
 
        /*
         *      Dup the amount of input path
         *      we need.
         */
        our_path = talloc_bstrndup(NULL, path, (size_t)len);
        if (!our_path) {
                fr_strerror_const("Out of memory");
                return -1;
        }
 
        fr_strerror_clear();    /* We make liberal use of push */
 
        /*
         *      Call the recursive function to
         *      create any missing dirs in the
         *      specified path.
         */
        slen = _fr_mkdir(&fd, our_path, our_path, mode, func, uctx);
        talloc_free(our_path);
        if (slen <= 0) return slen;
 
done:
        if (fd_out) {
                *fd_out = fd;
        } else {
                close(fd);
        }
 
        return len;
}
 
/** Convenience wrapper around realpath
 *
 * Wraps realpath, but takes a path with an explicit length, and returns
 * the result in a talloced buffer.
 *
 * On error, errno is set, and the string version of the error is
 * available with fr_strerror().
 *
 * @param[in] ctx       in which to allocate the result.
 * @param[in] path      To convert to an absolute path.
 * @param[in] len       How much of 'path' to read.  If < 0, then
 *                      the entire path will be used.
 * @return
 *      - NULL on error.
 *      - The absolute version of the input path on success.
 */
char *fr_realpath(TALLOC_CTX *ctx, char const *path, ssize_t len)
{
        char            *tmp_path = NULL, *abs_path, *talloc_abs_path;
 
        if (len > 0) path = tmp_path = talloc_bstrndup(NULL, path, (size_t)len);
 
        abs_path = realpath(path, NULL);
        if (!abs_path) {
                fr_strerror_printf("Failed resolving path \"%pV\": %s",
                                   fr_box_strvalue_buffer(path), fr_syserror(errno));
                talloc_free(tmp_path);
                return NULL;
        }
 
        talloc_free(tmp_path);
 
        talloc_abs_path = talloc_strdup(ctx, abs_path);
        free(abs_path);
        if (!talloc_abs_path) {
                fr_strerror_const("Out of Memory");
                return NULL;
        }
 
        return talloc_abs_path;
}
 
/** Create an empty file
 *
 * @param[out] fd_out   If not NULL, will contain a file descriptor
 *                      for the file we just opened.
 * @param[in] filename  path to file.
 * @param[in] mode      Specifies the file mode bits be applied.
 * @param[in] mkdir     Whether we should create directories
 *                      for any missing path components.
 * @param[in] dir_mode  Mode of any directories created.
 * @return
 *      - >0 on success.
 *      - <= 0 on failure. Error available in error stack (use fr_strerror())
 */
ssize_t fr_touch(int *fd_out, char const *filename, mode_t mode, bool mkdir, mode_t dir_mode) {
        int fd;
 
        fd = open(filename, O_WRONLY | O_CREAT, mode);
        if (fd < 0) {
                ssize_t slen = 0;
                char    *q;
 
                if (mkdir && (errno == ENOENT) && (q = strrchr(filename, FR_DIR_SEP))) {
                        int dir_fd;
 
                        slen = fr_mkdir(&dir_fd, filename, q - filename, dir_mode, NULL, NULL);
                        if (slen <= 0) return slen;
 
                        fd = openat(dir_fd, q + 1, O_WRONLY | O_CREAT, mode);
                        if (fd >= 0) {
                                close(dir_fd);
                                close(fd);
                                return strlen(filename);
                        }
                        close(dir_fd);
                        slen = -(q - filename);
                }
                fr_strerror_printf("Failed creating file: %s", fr_syserror(errno));
                return slen;
        }
 
        if (fd_out) {
                *fd_out = fd;
        } else {
                close(fd);
        }
 
        return strlen(filename);
}
 
/** Remove a regular file from the filesystem
 *
 * @param[in] filename path to file.
 * @return
 *      - -1 On error.
 *      - 0 if the file was removed.
 *      - 1 if the file didn't exist.
 */
int fr_unlink(char const *filename) {
        if (unlink(filename) == 0) return 0;
 
        if (errno == ENOENT) return 1;
 
        fr_strerror_printf("Failed removing regular file \"%s\": %s", filename, fr_syserror(errno));
 
        return -1;
}
 
/** Intended to be used in logging functions to make output more readable
 *
 * This function is not performant and should probably not be used at runtime.
 *
 * @param[in] filename  to strip working directory from.
 * @return Position in filename after our working directory.
 */
char const *fr_cwd_strip(char const *filename)
{
        static char our_wd[MAXPATHLEN];
        char *found;
 
        if (!getcwd(our_wd, sizeof(our_wd))) return filename;
 
        found = strstr(filename, our_wd);
        if (found && (found == our_wd)) {
                filename += strlen(our_wd);
                while (*filename == '/') filename++;
                return filename;
        }
 
        return filename;
}
 
/** From a pathname, return fd and filename needed for *at() functions
 *
 * @param[in] dirfd     points to place to store the dirfd
 * @param[in] filename  points to placd to store a pointer into pathname
 *                      that points to the filename
 * @param[in] pathname  the full pathname of the file
 *
 * @return
 *      - -1 on error
 *      -  0 on success
 */
int fr_dirfd(int *dirfd, char const **filename, char const *pathname)
{
        char const *last_slash = strrchr(pathname, '/');
 
        if (last_slash == NULL) {
                *filename = pathname;
                *dirfd = AT_FDCWD;
                return 0;
        }
        {
                char dirpath[(last_slash - pathname) + 1];
 
                memcpy(dirpath, pathname, last_slash - pathname);
                dirpath[last_slash - pathname] = '\0';
                *filename = last_slash + 1;
                *dirfd = open(dirpath, O_DIRECTORY);
                return (*dirfd < 0) ? -1 : 0;
        }
}