3 * $Id: path.c,v 1.3 1999/05/21 22:07:20 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 1.3 1999/05/21 22:07:20 mdw
33 * Take advantage of new dynamic string macros.
35 * Revision 1.2 1999/05/18 20:49:12 mdw
36 * Use a dynamic string for reading symlinks.
38 * Revision 1.1.1.1 1999/04/06 20:12:07 mdw
43 /*----- Header files ------------------------------------------------------*/
51 #include <sys/types.h>
58 #include <mLib/alloc.h>
59 #include <mLib/dstr.h>
63 /*----- Data structures ---------------------------------------------------*/
65 /* --- An item in the directory list --- *
67 * Each directory becomes an element on a list which is manipulated in a
72 struct elt *e_link; /* Pointer to the next one along */
73 size_t e_offset; /* Offset of name in path string */
74 unsigned e_flags; /* Various useful flags */
75 char e_name[1]; /* Name of the directory */
79 f_sticky = 1 /* Directory has sticky bit set */
83 f_last = 1 /* This is the final item to check */
86 /*----- Static variables --------------------------------------------------*/
88 static struct elt rootnode = { 0, 0, 0 }; /* Root of the list */
89 static struct elt *sp; /* Stack pointer for list */
90 static dstr d = DSTR_INIT; /* Current path string */
92 /*----- Main code ---------------------------------------------------------*/
94 /* --- @splitpath@ --- *
96 * Arguments: @const char *path@ = path string to break apart
97 * @struct elt *tail@ = tail block to attach to end of list
99 * Returns: Pointer to the new list head.
101 * Use: Breaks a path string into directories and adds each one
102 * as a node on the list, in the right order. These can then
103 * be pushed onto the directory stack as required.
106 static struct elt *splitpath(const char *path, struct elt *tail)
108 struct elt *head, **ee = &head, *e;
113 /* --- Either a leading `/', or a doubled one --- *
115 * Either way, ignore it.
123 /* --- Skip to the next directory separator --- *
125 * Build a list element for it, and link it on.
128 n = strcspn(path, "/");
129 e = xmalloc(sizeof(struct elt) + n + 1);
130 memcpy(e->e_name, path, n);
150 * Use: Removes the top item from the directory stack.
153 static void pop(void)
156 struct elt *e = sp->e_link;
157 d.len = sp->e_offset;
163 /* --- @popall@ --- *
169 * Use: Removes all the items from the directory stack.
172 static void popall(void)
180 * Arguments: @struct elt *e@ = pointer to directory element
184 * Use: Pushes a new subdirectory onto the stack.
187 static void push(struct elt *e)
192 DPUTS(&d, e->e_name);
196 /* --- @report@ --- *
198 * Arguments: @struct chkpath *cp@ = pointer to context
199 * @int what@ = what sort of report is this?
200 * @int verbose@ = how verbose is this?
201 * @const char *p@ = what path does it refer to?
202 * @const char *msg@ = the message to give to the user
206 * Use: Formats and presents messages to the client.
209 static void report(struct chkpath *cp, int what, int verbose,
210 const char *p, const char *msg, ...)
212 /* --- Decide whether to bin this message --- */
214 if (!cp->cp_report || verbose > cp->cp_verbose || !(cp->cp_what & what))
217 /* --- Format the message nicely --- */
219 if (cp->cp_what & CP_REPORT) {
230 dstr_putf(&d, "Path: %s: ", p);
236 dstr_puts(&d, strerror(e));
239 uid_t u = (uid_t)va_arg(ap, int);
240 struct passwd *pw = getpwuid(u);
242 dstr_putf(&d, "`%s'", pw->pw_name);
244 dstr_putf(&d, "%i", (int)u);
247 gid_t g = (gid_t)va_arg(ap, int);
248 struct group *gr = getgrgid(g);
250 dstr_putf(&d, "`%s'", gr->gr_name);
252 dstr_putf(&d, "%i", (int)g);
255 const char *s = va_arg(ap, const char *);
276 cp->cp_report(what, verbose, p, d.buf, cp->cp_arg);
280 cp->cp_report(what, verbose, p, 0, cp->cp_arg);
283 /* --- @sanity@ --- *
285 * Arguments: @const char *p@ = name of directory to check
286 * @struct stat *st@ = pointer to @stat@(2) block for it
287 * @struct chkpath *cp@ = pointer to caller parameters
288 * @unsigned f@ = various flags
290 * Returns: Zero if everything's OK, else bitmask of problems.
292 * Use: Performs the main load of sanity-checking on a directory.
295 static int sanity(const char *p, struct stat *st,
296 struct chkpath *cp, unsigned f)
299 int sticky = (cp->cp_what & CP_STICKYOK) || !(f & f_last) ? 01000 : 0;
301 /* --- Check for world-writability --- */
303 if ((cp->cp_what & CP_WRWORLD) &&
304 (st->st_mode & (0002 | sticky)) == 0002) {
306 report(cp, CP_WRWORLD, 1, p, "** world writable **");
309 /* --- Check for group-writability --- */
311 if ((cp->cp_what & (CP_WRGRP | CP_WROTHGRP)) &&
312 (st->st_mode & (0020 | sticky)) == 0020) {
313 if (cp->cp_what & CP_WRGRP) {
315 report(cp, CP_WRGRP, 1, p, "writable by group %g", st->st_gid);
318 for (i = 0; i < cp->cp_gids; i++) {
319 if (st->st_gid == cp->cp_gid[i])
323 report(cp, CP_WROTHGRP, 1, p, "writable by group %g", st->st_gid);
328 /* --- Check for user-writability --- */
330 if ((cp->cp_what & CP_WROTHUSR) &&
331 st->st_uid != cp->cp_uid &&
334 report(cp, CP_WROTHUSR, 1, p, "owner is user %u", st->st_uid);
337 /* --- Done sanity check --- */
342 /* --- @path_check@ --- *
344 * Arguments: @const char *p@ = directory name which needs checking
345 * @struct chkpath *cp@ = caller parameters for the check
347 * Returns: Zero if all is well, otherwise bitmask of problems.
349 * Use: Scrutinises a directory path to see what evil things other
350 * users could do to it.
353 int path_check(const char *p, struct chkpath *cp)
360 /* --- Initialize stack pointer and path string --- */
365 /* --- Try to find the current directory --- */
367 if (!getcwd(cwd, sizeof(cwd))) {
368 report(cp, CP_ERROR, 0, 0, "can't find current directory: %e");
372 /* --- Check that the root directory is OK --- */
374 if (stat("/", &st)) {
375 report(cp, CP_ERROR, 0, 0, "can't stat root directory: %e");
379 report(cp, CP_REPORT, 3, p, "begin scan");
380 bad |= sanity("/", &st, cp, 0);
382 /* --- Get the initial list of things to process --- */
384 ee = splitpath(p, 0);
386 ee = splitpath(cwd, ee);
388 /* --- While there are list items which still need doing --- */
393 /* --- Strip off simple `.' elements --- */
395 if (strcmp(ee->e_name, ".") == 0) {
401 /* --- Backtrack on `..' elements --- */
403 else if (strcmp(ee->e_name, "..") == 0) {
410 /* --- Everything else gets pushed on the end --- */
415 /* --- Find out what sort of a thing this is --- */
417 if (lstat(d.buf, &st)) {
418 report(cp, CP_ERROR, 0, d.buf, "can't stat: %e");
423 /* --- Handle symbolic links specially --- */
425 if (S_ISLNK(st.st_mode)) {
426 dstr buf = DSTR_INIT;
429 /* --- Resolve the link --- */
431 dstr_ensure(&buf, st.st_size + 1);
432 if ((i = readlink(d.buf, buf.buf, buf.sz)) < 0) {
433 report(cp, CP_ERROR, 0, d.buf, "can't readlink: %e");
438 report(cp, CP_SYMLINK, 2, d.buf, "symlink -> `%s'", buf.buf);
440 /* --- Handle sticky parents --- *
442 * If I make a symlink in a sticky directory, I can later modify it.
443 * However, nobody else can (except the owner of the directory, and
444 * we'll already have noticed that if we care).
447 if ((cp->cp_what & CP_WROTHUSR) &&
448 (sp->e_link->e_flags & f_sticky) &&
449 st.st_uid != cp->cp_uid && st.st_uid != 0) {
451 report(cp, CP_WROTHUSR, 1, d.buf,
452 "symlink modifiable by user %u", st.st_uid);
455 /* --- Sort out what to do from here --- */
457 if (buf.buf[0] == '/')
461 ee = splitpath(buf.buf, ee);
466 /* --- Run the sanity check on this path element --- */
468 bad |= sanity(d.buf, &st, cp, ee ? 0 : f_last);
470 if (S_ISDIR(st.st_mode)) {
471 if (st.st_mode & 01000)
472 sp->e_flags |= f_sticky;
473 report(cp, CP_REPORT, 4, d.buf, "directory");
477 /* --- Something else I don't understand --- */
482 /* --- Check for leftover junk --- */
485 if (!(bad & CP_ERROR))
486 report(cp, CP_ERROR, 0, 0, "junk left over after reaching leaf");
498 /* --- @path_setids@ --- *
500 * Arguments: @struct chkpath *cp@ = pointer to block to fill in
502 * Returns: Zero if OK, else @-1@.
504 * Use: Fills in the user ids and things in the structure.
507 void path_setids(struct chkpath *cp)
512 cp->cp_uid = getuid();
513 n = getgroups(sizeof(cp->cp_gid) / sizeof(cp->cp_gid[0]), cp->cp_gid);
515 for (i = 0; i < n; i++) {
516 if (cp->cp_gid[i] == g)
524 /*----- That's all, folks -------------------------------------------------*/