/*

 * SPDX-License-Identifier: ISC

 *

 * Copyright (c) 2026 Todd C. Miller <Todd.Miller@sudo.ws>

 *

 * Permission to use, copy, modify, and distribute this software for any

 * purpose with or without fee is hereby granted, provided that the above

 * copyright notice and this permission notice appear in all copies.

 *

 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES

 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF

 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR

 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES

 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN

 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF

 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

 */

#include <config.h>

#include <assert.h>

#include <string.h>

#include <sudoers.h>

/*

 * Rationalize a path by removing consecutive '/' and "/./" path elements.

 * Also removes "/../" elements if dotdot is true.

 */

char *

rationalize_path(char *path, bool dotdot)

{

    char *cp, *ep, *path_end;

    debug_decl(rationalize_path, SUDOERS_DEBUG_UTIL);

    path_end = path + strlen(path);

    for (cp = path; *cp != '\0';) {

  if (cp[0] == '/') {

      /* Collapse consecutive '/' characters. */

      if (cp[1] == '/') {

    for (ep = cp + 1; ep[1] == '/'; ep++)

        continue;

    /* The size argument includes the terminating NUL byte. */

    assert(ep <= path_end);

    memmove(cp, ep, (size_t)(path_end - ep) + 1);

    path_end -= ep - cp;

    assert(*path_end == '\0');

    continue;

      }

      /* Remove "/./" in path or "/." at path_end. */

      if (cp[1] == '.' && (cp[2] == '/' || cp[2] == '\0')) {

    /* /./foo -> /foo OR /foo/. -> /foo */

    ep = cp + 2;

    /* The size argument includes the terminating NUL byte. */

    assert(ep <= path_end);

    memmove(cp, ep, (size_t)(path_end - ep) + 1);

    path_end -= ep - cp;

    /* An absolute path must not collapse to the empty string. */

    if (cp == path && *cp == '\0') {

        /* /. -> / */

        path[0] = '/';

        path[1] = '\0';

        path_end = path + 1;

    }

    assert(*path_end == '\0');

    continue;

      }

      /* Remove "/../" in path or "/.." at path_end. */

      if (dotdot && cp[1] == '.' && cp[2] == '.' &&

        (cp[3] == '/' || cp[3] == '\0')) {

    /* Skip ep past "/../" or "/.." */

    ep = cp + 3 + (cp[3] == '/');

    /* Set cp to the previous '/' if there is one. */

    if (cp != path) {

        char *saved_cp = cp;

        ep = cp + 3 + (cp[3] == '/');

        do {

      cp--;

        } while (cp > path && *cp != '/');

        if (*cp != '/') {

      /* No previous '/', path doesn't start with '/'? */

      cp = saved_cp;

        }

    }

    /* The size argument includes the terminating NUL byte. */

    assert(ep <= path_end);

    memmove(cp + 1, ep, (size_t)(path_end - ep) + 1);

    path_end -= ep - (cp + 1);

    assert(*path_end == '\0');

    continue;

      }

  }

  cp++;

    }

    debug_return_str(path);

}