3 * $Id: path.c,v 1.1 1999/04/06 20:12:07 mdw Exp $
5 * Check a path for safety
7 * (c) 1999 Mark Wooding
10 /*----- Licensing notice --------------------------------------------------*
12 * This file is part of chkpath.
14 * chkpath is free software; you can redistribute it and/or modify
15 * it under the terms of the GNU General Public License as published by
16 * the Free Software Foundation; either version 2 of the License, or
17 * (at your option) any later version.
19 * chkpath is distributed in the hope that it will be useful,
20 * but WITHOUT ANY WARRANTY; without even the implied warranty of
21 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
22 * GNU General Public License for more details.
24 * You should have received a copy of the GNU General Public License
25 * along with chkpath; if not, write to the Free Software Foundation,
26 * Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
29 /*----- Revision history --------------------------------------------------*
32 * Revision 1.1 1999/04/06 20:12:07 mdw
37 /*----- Header files ------------------------------------------------------*/
45 #include <sys/types.h>
52 #include <mLib/alloc.h>
53 #include <mLib/dstr.h>
57 /*----- Data structures ---------------------------------------------------*/
59 /* --- An item in the directory list --- *
61 * Each directory becomes an element on a list which is manipulated in a
66 struct elt *e_link; /* Pointer to the next one along */
67 size_t e_offset; /* Offset of name in path string */
68 unsigned e_flags; /* Various useful flags */
69 char e_name[1]; /* Name of the directory */
73 f_sticky = 1 /* Directory has sticky bit set */
77 f_last = 1 /* This is the final item to check */
80 /*----- Static variables --------------------------------------------------*/
82 static struct elt rootnode = { 0, 0, 0 }; /* Root of the list */
83 static struct elt *sp; /* Stack pointer for list */
84 static dstr d; /* Current path string */
86 /*----- Main code ---------------------------------------------------------*/
88 /* --- @splitpath@ --- *
90 * Arguments: @const char *path@ = path string to break apart
91 * @struct elt *tail@ = tail block to attach to end of list
93 * Returns: Pointer to the new list head.
95 * Use: Breaks a path string into directories and adds each one
96 * as a node on the list, in the right order. These can then
97 * be pushed onto the directory stack as required.
100 static struct elt *splitpath(const char *path, struct elt *tail)
102 struct elt *head, **ee = &head, *e;
107 /* --- Either a leading `/', or a doubled one --- *
109 * Either way, ignore it.
117 /* --- Skip to the next directory separator --- *
119 * Build a list element for it, and link it on.
122 n = strcspn(path, "/");
123 e = xmalloc(sizeof(struct elt) + n + 1);
124 memcpy(e->e_name, path, n);
144 * Use: Removes the top item from the directory stack.
147 static void pop(void)
150 struct elt *e = sp->e_link;
151 d.len = sp->e_offset;
157 /* --- @popall@ --- *
163 * Use: Removes all the items from the directory stack.
166 static void popall(void)
174 * Arguments: @struct elt *e@ = pointer to directory element
178 * Use: Pushes a new subdirectory onto the stack.
181 static void push(struct elt *e)
186 DPUTS(&d, e->e_name);
190 /* --- @report@ --- *
192 * Arguments: @struct chkpath *cp@ = pointer to context
193 * @int what@ = what sort of report is this?
194 * @int verbose@ = how verbose is this?
195 * @const char *p@ = what path does it refer to?
196 * @const char *msg@ = the message to give to the user
200 * Use: Formats and presents messages to the client.
203 static void report(struct chkpath *cp, int what, int verbose,
204 const char *p, const char *msg, ...)
206 /* --- Decide whether to bin this message --- */
208 if (!cp->cp_report || verbose > cp->cp_verbose || !(cp->cp_what & what))
211 /* --- Format the message nicely --- */
213 if (cp->cp_what & CP_REPORT) {
225 dstr_putf(&d, "Path: %s: ", p);
231 dstr_puts(&d, strerror(e));
234 uid_t u = (uid_t)va_arg(ap, int);
235 struct passwd *pw = getpwuid(u);
237 dstr_putf(&d, "`%s'", pw->pw_name);
239 dstr_putf(&d, "%i", (int)u);
242 gid_t g = (gid_t)va_arg(ap, int);
243 struct group *gr = getgrgid(g);
245 dstr_putf(&d, "`%s'", gr->gr_name);
247 dstr_putf(&d, "%i", (int)g);
250 const char *s = va_arg(ap, const char *);
271 cp->cp_report(what, verbose, p, d.buf, cp->cp_arg);
275 cp->cp_report(what, verbose, p, 0, cp->cp_arg);
278 /* --- @sanity@ --- *
280 * Arguments: @const char *p@ = name of directory to check
281 * @struct stat *st@ = pointer to @stat@(2) block for it
282 * @struct chkpath *cp@ = pointer to caller parameters
283 * @unsigned f@ = various flags
285 * Returns: Zero if everything's OK, else bitmask of problems.
287 * Use: Performs the main load of sanity-checking on a directory.
290 static int sanity(const char *p, struct stat *st,
291 struct chkpath *cp, unsigned f)
294 int sticky = (cp->cp_what & CP_STICKYOK) || !(f & f_last) ? 01000 : 0;
296 /* --- Check for world-writability --- */
298 if ((cp->cp_what & CP_WRWORLD) &&
299 (st->st_mode & (0002 | sticky)) == 0002) {
301 report(cp, CP_WRWORLD, 1, p, "** world writable **");
304 /* --- Check for group-writability --- */
306 if ((cp->cp_what & (CP_WRGRP | CP_WROTHGRP)) &&
307 (st->st_mode & (0020 | sticky)) == 0020) {
308 if (cp->cp_what & CP_WRGRP) {
310 report(cp, CP_WRGRP, 1, p, "writable by group %g", st->st_gid);
313 for (i = 0; i < cp->cp_gids; i++) {
314 if (st->st_gid == cp->cp_gid[i])
318 report(cp, CP_WROTHGRP, 1, p, "writable by group %g", st->st_gid);
323 /* --- Check for user-writability --- */
325 if ((cp->cp_what & CP_WROTHUSR) &&
326 st->st_uid != cp->cp_uid &&
329 report(cp, CP_WROTHUSR, 1, p, "owner is user %u", st->st_uid);
332 /* --- Done sanity check --- */
337 /* --- @path_check@ --- *
339 * Arguments: @const char *p@ = directory name which needs checking
340 * @struct chkpath *cp@ = caller parameters for the check
342 * Returns: Zero if all is well, otherwise bitmask of problems.
344 * Use: Scrutinises a directory path to see what evil things other
345 * users could do to it.
348 int path_check(const char *p, struct chkpath *cp)
355 /* --- Initialise stack pointer and path string --- */
360 /* --- Try to find the current directory --- */
362 if (!getcwd(cwd, sizeof(cwd))) {
363 report(cp, CP_ERROR, 0, 0, "can't find current directory: %e");
367 /* --- Check that the root directory is OK --- */
369 if (stat("/", &st)) {
370 report(cp, CP_ERROR, 0, 0, "can't stat root directory: %e");
374 report(cp, CP_REPORT, 3, p, "begin scan");
375 bad |= sanity("/", &st, cp, 0);
377 /* --- Get the initial list of things to process --- */
379 ee = splitpath(p, 0);
381 ee = splitpath(cwd, ee);
383 /* --- While there are list items which still need doing --- */
388 /* --- Strip off simple `.' elements --- */
390 if (strcmp(ee->e_name, ".") == 0) {
396 /* --- Backtrack on `..' elements --- */
398 else if (strcmp(ee->e_name, "..") == 0) {
405 /* --- Everything else gets pushed on the end --- */
410 /* --- Find out what sort of a thing this is --- */
412 if (lstat(d.buf, &st)) {
413 report(cp, CP_ERROR, 0, d.buf, "can't stat: %e");
418 /* --- Handle symbolic links specially --- */
420 if (S_ISLNK(st.st_mode)) {
424 /* --- Resolve the link --- */
426 if ((i = readlink(d.buf, buf, sizeof(buf))) < 0) {
427 report(cp, CP_ERROR, 0, d.buf, "can't readlink: %e");
432 report(cp, CP_SYMLINK, 2, d.buf, "symlink -> `%s'", buf);
434 /* --- Handle sticky parents --- *
436 * If I make a symlink in a sticky directory, I can later modify it.
437 * However, nobody else can (except the owner of the directory, and
438 * we'll already have noticed that if we care).
441 if ((cp->cp_what & CP_WROTHUSR) &&
442 (sp->e_link->e_flags & f_sticky) &&
443 st.st_uid != cp->cp_uid && st.st_uid != 0) {
445 report(cp, CP_WROTHUSR, 1, d.buf,
446 "symlink modifiable by user %u", st.st_uid);
449 /* --- Sort out what to do from here --- */
455 ee = splitpath(buf, ee);
459 /* --- Run the sanity check on this path element --- */
461 bad |= sanity(d.buf, &st, cp, ee ? 0 : f_last);
463 if (S_ISDIR(st.st_mode)) {
464 if (st.st_mode & 01000)
465 sp->e_flags |= f_sticky;
466 report(cp, CP_REPORT, 4, d.buf, "directory");
470 /* --- Something else I don't understand --- */
475 /* --- Check for leftover junk --- */
478 if (!(bad & CP_ERROR))
479 report(cp, CP_ERROR, 0, 0, "junk left over after reaching leaf");
491 /* --- @path_setids@ --- *
493 * Arguments: @struct chkpath *cp@ = pointer to block to fill in
495 * Returns: Zero if OK, else @-1@.
497 * Use: Fills in the user ids and things in the structure.
500 void path_setids(struct chkpath *cp)
505 cp->cp_uid = getuid();
506 n = getgroups(sizeof(cp->cp_gid) / sizeof(cp->cp_gid[0]), cp->cp_gid);
508 for (i = 0; i < n; i++) {
509 if (cp->cp_gid[i] == g)
517 /*----- That's all, folks -------------------------------------------------*/