3 * $Id: path.c,v 1.4 2001/01/25 22:16:02 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 1.4 2001/01/25 22:16:02 mdw
33 * Make flags be unsigned.
35 * Revision 1.3 1999/05/21 22:07:20 mdw
36 * Take advantage of new dynamic string macros.
38 * Revision 1.2 1999/05/18 20:49:12 mdw
39 * Use a dynamic string for reading symlinks.
41 * Revision 1.1.1.1 1999/04/06 20:12:07 mdw
46 /*----- Header files ------------------------------------------------------*/
54 #include <sys/types.h>
61 #include <mLib/alloc.h>
62 #include <mLib/dstr.h>
66 /*----- Data structures ---------------------------------------------------*/
68 /* --- An item in the directory list --- *
70 * Each directory becomes an element on a list which is manipulated in a
75 struct elt *e_link; /* Pointer to the next one along */
76 size_t e_offset; /* Offset of name in path string */
77 unsigned e_flags; /* Various useful flags */
78 char e_name[1]; /* Name of the directory */
81 #define f_sticky 1u /* Directory has sticky bit set */
83 #define f_last 1u /* This is the final item to check */
85 /*----- Static variables --------------------------------------------------*/
87 static struct elt rootnode = { 0, 0, 0 }; /* Root of the list */
88 static struct elt *sp; /* Stack pointer for list */
89 static dstr d = DSTR_INIT; /* Current path string */
91 /*----- Main code ---------------------------------------------------------*/
93 /* --- @splitpath@ --- *
95 * Arguments: @const char *path@ = path string to break apart
96 * @struct elt *tail@ = tail block to attach to end of list
98 * Returns: Pointer to the new list head.
100 * Use: Breaks a path string into directories and adds each one
101 * as a node on the list, in the right order. These can then
102 * be pushed onto the directory stack as required.
105 static struct elt *splitpath(const char *path, struct elt *tail)
107 struct elt *head, **ee = &head, *e;
112 /* --- Either a leading `/', or a doubled one --- *
114 * Either way, ignore it.
122 /* --- Skip to the next directory separator --- *
124 * Build a list element for it, and link it on.
127 n = strcspn(path, "/");
128 e = xmalloc(sizeof(struct elt) + n + 1);
129 memcpy(e->e_name, path, n);
149 * Use: Removes the top item from the directory stack.
152 static void pop(void)
155 struct elt *e = sp->e_link;
156 d.len = sp->e_offset;
162 /* --- @popall@ --- *
168 * Use: Removes all the items from the directory stack.
171 static void popall(void)
179 * Arguments: @struct elt *e@ = pointer to directory element
183 * Use: Pushes a new subdirectory onto the stack.
186 static void push(struct elt *e)
191 DPUTS(&d, e->e_name);
195 /* --- @report@ --- *
197 * Arguments: @struct chkpath *cp@ = pointer to context
198 * @int what@ = what sort of report is this?
199 * @int verbose@ = how verbose is this?
200 * @const char *p@ = what path does it refer to?
201 * @const char *msg@ = the message to give to the user
205 * Use: Formats and presents messages to the client.
208 static void report(struct chkpath *cp, int what, int verbose,
209 const char *p, const char *msg, ...)
211 /* --- Decide whether to bin this message --- */
213 if (!cp->cp_report || verbose > cp->cp_verbose || !(cp->cp_what & what))
216 /* --- Format the message nicely --- */
218 if (cp->cp_what & CP_REPORT) {
229 dstr_putf(&d, "Path: %s: ", p);
235 dstr_puts(&d, strerror(e));
238 uid_t u = (uid_t)va_arg(ap, int);
239 struct passwd *pw = getpwuid(u);
241 dstr_putf(&d, "`%s'", pw->pw_name);
243 dstr_putf(&d, "%i", (int)u);
246 gid_t g = (gid_t)va_arg(ap, int);
247 struct group *gr = getgrgid(g);
249 dstr_putf(&d, "`%s'", gr->gr_name);
251 dstr_putf(&d, "%i", (int)g);
254 const char *s = va_arg(ap, const char *);
275 cp->cp_report(what, verbose, p, d.buf, cp->cp_arg);
279 cp->cp_report(what, verbose, p, 0, cp->cp_arg);
282 /* --- @sanity@ --- *
284 * Arguments: @const char *p@ = name of directory to check
285 * @struct stat *st@ = pointer to @stat@(2) block for it
286 * @struct chkpath *cp@ = pointer to caller parameters
287 * @unsigned f@ = various flags
289 * Returns: Zero if everything's OK, else bitmask of problems.
291 * Use: Performs the main load of sanity-checking on a directory.
294 static int sanity(const char *p, struct stat *st,
295 struct chkpath *cp, unsigned f)
298 int sticky = (cp->cp_what & CP_STICKYOK) || !(f & f_last) ? 01000 : 0;
300 /* --- Check for world-writability --- */
302 if ((cp->cp_what & CP_WRWORLD) &&
303 (st->st_mode & (0002 | sticky)) == 0002) {
305 report(cp, CP_WRWORLD, 1, p, "** world writable **");
308 /* --- Check for group-writability --- */
310 if ((cp->cp_what & (CP_WRGRP | CP_WROTHGRP)) &&
311 (st->st_mode & (0020 | sticky)) == 0020) {
312 if (cp->cp_what & CP_WRGRP) {
314 report(cp, CP_WRGRP, 1, p, "writable by group %g", st->st_gid);
317 for (i = 0; i < cp->cp_gids; i++) {
318 if (st->st_gid == cp->cp_gid[i])
322 report(cp, CP_WROTHGRP, 1, p, "writable by group %g", st->st_gid);
327 /* --- Check for user-writability --- */
329 if ((cp->cp_what & CP_WROTHUSR) &&
330 st->st_uid != cp->cp_uid &&
333 report(cp, CP_WROTHUSR, 1, p, "owner is user %u", st->st_uid);
336 /* --- Done sanity check --- */
341 /* --- @path_check@ --- *
343 * Arguments: @const char *p@ = directory name which needs checking
344 * @struct chkpath *cp@ = caller parameters for the check
346 * Returns: Zero if all is well, otherwise bitmask of problems.
348 * Use: Scrutinises a directory path to see what evil things other
349 * users could do to it.
352 int path_check(const char *p, struct chkpath *cp)
359 /* --- Initialize stack pointer and path string --- */
364 /* --- Try to find the current directory --- */
366 if (!getcwd(cwd, sizeof(cwd))) {
367 report(cp, CP_ERROR, 0, 0, "can't find current directory: %e");
371 /* --- Check that the root directory is OK --- */
373 if (stat("/", &st)) {
374 report(cp, CP_ERROR, 0, 0, "can't stat root directory: %e");
378 report(cp, CP_REPORT, 3, p, "begin scan");
379 bad |= sanity("/", &st, cp, 0);
381 /* --- Get the initial list of things to process --- */
383 ee = splitpath(p, 0);
385 ee = splitpath(cwd, ee);
387 /* --- While there are list items which still need doing --- */
392 /* --- Strip off simple `.' elements --- */
394 if (strcmp(ee->e_name, ".") == 0) {
400 /* --- Backtrack on `..' elements --- */
402 else if (strcmp(ee->e_name, "..") == 0) {
409 /* --- Everything else gets pushed on the end --- */
414 /* --- Find out what sort of a thing this is --- */
416 if (lstat(d.buf, &st)) {
417 report(cp, CP_ERROR, 0, d.buf, "can't stat: %e");
422 /* --- Handle symbolic links specially --- */
424 if (S_ISLNK(st.st_mode)) {
425 dstr buf = DSTR_INIT;
428 /* --- Resolve the link --- */
430 dstr_ensure(&buf, st.st_size + 1);
431 if ((i = readlink(d.buf, buf.buf, buf.sz)) < 0) {
432 report(cp, CP_ERROR, 0, d.buf, "can't readlink: %e");
437 report(cp, CP_SYMLINK, 2, d.buf, "symlink -> `%s'", buf.buf);
439 /* --- Handle sticky parents --- *
441 * If I make a symlink in a sticky directory, I can later modify it.
442 * However, nobody else can (except the owner of the directory, and
443 * we'll already have noticed that if we care).
446 if ((cp->cp_what & CP_WROTHUSR) &&
447 (sp->e_link->e_flags & f_sticky) &&
448 st.st_uid != cp->cp_uid && st.st_uid != 0) {
450 report(cp, CP_WROTHUSR, 1, d.buf,
451 "symlink modifiable by user %u", st.st_uid);
454 /* --- Sort out what to do from here --- */
456 if (buf.buf[0] == '/')
460 ee = splitpath(buf.buf, ee);
465 /* --- Run the sanity check on this path element --- */
467 bad |= sanity(d.buf, &st, cp, ee ? 0 : f_last);
469 if (S_ISDIR(st.st_mode)) {
470 if (st.st_mode & 01000)
471 sp->e_flags |= f_sticky;
472 report(cp, CP_REPORT, 4, d.buf, "directory");
476 /* --- Something else I don't understand --- */
481 /* --- Check for leftover junk --- */
484 if (!(bad & CP_ERROR))
485 report(cp, CP_ERROR, 0, 0, "junk left over after reaching leaf");
497 /* --- @path_setids@ --- *
499 * Arguments: @struct chkpath *cp@ = pointer to block to fill in
501 * Returns: Zero if OK, else @-1@.
503 * Use: Fills in the user ids and things in the structure.
506 void path_setids(struct chkpath *cp)
511 cp->cp_uid = getuid();
512 n = getgroups(sizeof(cp->cp_gid) / sizeof(cp->cp_gid[0]), cp->cp_gid);
514 for (i = 0; i < n; i++) {
515 if (cp->cp_gid[i] == g)
523 /*----- That's all, folks -------------------------------------------------*/