3 * Check a path for safety
5 * (c) 1999 Mark Wooding
8 /*----- Licensing notice --------------------------------------------------*
10 * This file is part of chkpath.
12 * chkpath is free software; you can redistribute it and/or modify
13 * it under the terms of the GNU General Public License as published by
14 * the Free Software Foundation; either version 2 of the License, or
15 * (at your option) any later version.
17 * chkpath is distributed in the hope that it will be useful,
18 * but WITHOUT ANY WARRANTY; without even the implied warranty of
19 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
20 * GNU General Public License for more details.
22 * You should have received a copy of the GNU General Public License
23 * along with chkpath; if not, write to the Free Software Foundation,
24 * Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
27 /*----- Header files ------------------------------------------------------*/
37 #include <sys/types.h>
44 #include <mLib/alloc.h>
45 #include <mLib/dstr.h>
47 #include "checkpath.h"
49 /*----- Data structures ---------------------------------------------------*/
51 /* --- An item in the directory list --- *
53 * Each directory becomes an element on a list which is manipulated in a
58 struct elt *e_link; /* Pointer to the next one along */
59 size_t e_offset; /* Offset of name in path string */
60 unsigned e_flags; /* Various useful flags */
61 char e_name[1]; /* Name of the directory */
64 #define f_sticky 1u /* Directory has sticky bit set */
66 #define f_last 1u /* This is the final item to check */
68 /*----- Static variables --------------------------------------------------*/
70 static struct elt rootnode = { 0, 0, 0 }; /* Root of the list */
71 static struct elt *sp; /* Stack pointer for list */
72 static dstr d = DSTR_INIT; /* Current path string */
74 /*----- Main code ---------------------------------------------------------*/
76 /* --- @splitpath@ --- *
78 * Arguments: @const char *path@ = path string to break apart
79 * @struct elt *tail@ = tail block to attach to end of list
81 * Returns: Pointer to the new list head.
83 * Use: Breaks a path string into directories and adds each one
84 * as a node on the list, in the right order. These can then
85 * be pushed onto the directory stack as required.
88 static struct elt *splitpath(const char *path, struct elt *tail)
90 struct elt *head, **ee = &head, *e;
95 /* --- Either a leading `/', or a doubled one --- *
97 * Either way, ignore it.
105 /* --- Skip to the next directory separator --- *
107 * Build a list element for it, and link it on.
110 n = strcspn(path, "/");
111 e = xmalloc(sizeof(struct elt) + n + 1);
112 memcpy(e->e_name, path, n);
132 * Use: Removes the top item from the directory stack.
135 static void pop(void)
138 struct elt *e = sp->e_link;
139 d.len = sp->e_offset;
145 /* --- @popall@ --- *
151 * Use: Removes all the items from the directory stack.
154 static void popall(void)
155 { while (sp->e_link) pop(); }
159 * Arguments: @struct elt *e@ = pointer to directory element
163 * Use: Pushes a new subdirectory onto the stack.
166 static void push(struct elt *e)
171 DPUTS(&d, e->e_name);
175 /* --- @report@ --- *
177 * Arguments: @const struct checkpath *cp@ = pointer to context
178 * @unsigned what@ = what sort of report is this?
179 * @int verbose@ = how verbose is this?
180 * @const char *p@ = what path does it refer to?
181 * @const char *msg@ = the message to give to the user
185 * Use: Formats and presents messages to the client.
188 static void report(const struct checkpath *cp, unsigned what, int verbose,
189 const char *p, const char *msg, ...)
202 /* --- Decide whether to bin this message --- */
204 if (!cp->cp_report || verbose > cp->cp_verbose || !(cp->cp_what & what))
207 /* --- If no reporting, do the easy thing --- */
209 if (!(cp->cp_what & CP_REPORT)) {
210 cp->cp_report(what, verbose, p, 0, cp->cp_arg);
214 /* --- Format the message nicely --- */
220 dstr_putf(&d, "Path: %s: ", p);
226 dstr_puts(&d, strerror(e));
229 u = (uid_t)va_arg(ap, int);
230 if ((pw = getpwuid(u)) != 0)
231 dstr_putf(&d, "`%s'", pw->pw_name);
233 dstr_putf(&d, "%i", (int)u);
236 g = (gid_t)va_arg(ap, int);
237 if ((gr = getgrgid(g)) != 0)
238 dstr_putf(&d, "`%s'", gr->gr_name);
240 dstr_putf(&d, "%i", (int)g);
243 s = va_arg(ap, const char *);
264 cp->cp_report(what, verbose, p, d.buf, cp->cp_arg);
269 /* --- @sanity@ --- *
271 * Arguments: @const char *p@ = name of directory to check
272 * @struct stat *st@ = pointer to @stat@(2) block for it
273 * @const struct checkpath *cp@ = pointer to caller parameters
274 * @unsigned f@ = various flags
276 * Returns: Zero if everything's OK, else bitmask of problems.
278 * Use: Performs the main load of sanity-checking on a directory.
281 static unsigned sanity(const char *p, struct stat *st,
282 const struct checkpath *cp, unsigned f)
289 if (S_ISDIR(st->st_mode) &&
290 (!(f & f_last) || (cp->cp_what & CP_STICKYOK)))
293 /* --- Check for world-writability --- */
295 if ((cp->cp_what & CP_WRWORLD) &&
296 (st->st_mode & (0002 | stickyok)) == 0002) {
298 report(cp, CP_WRWORLD, 1, p, "** world writable **");
301 /* --- Check for group-writability --- */
303 if ((cp->cp_what & (CP_WRGRP | CP_WROTHGRP)) &&
304 (st->st_mode & (0020 | stickyok)) == 0020) {
307 if (cp->cp_what & CP_WROTHGRP) {
309 for (i = 0; i < cp->cp_gids; i++) {
310 if (st->st_gid == cp->cp_gid[i])
311 b = cp->cp_what & CP_WRGRP;
316 report(cp, b, 1, p, "writable by %sgroup %g",
317 (b == CP_WROTHGRP) ? "other " : "", st->st_gid);
321 /* --- Check for user-writability --- */
323 if ((cp->cp_what & CP_WROTHUSR) &&
324 st->st_uid != cp->cp_uid &&
327 report(cp, CP_WROTHUSR, 1, p, "owner is user %u", st->st_uid);
330 /* --- Done sanity check --- */
335 /* --- @checkpath@ --- *
337 * Arguments: @const char *p@ = directory name which needs checking
338 * @const struct checkpath *cp@ = parameters for the check
340 * Returns: Zero if all is well, otherwise bitmask of problems.
342 * Use: Scrutinises a directory path to see what evil things other
343 * users could do to it.
346 unsigned checkpath(const char *p, const struct checkpath *cp)
353 /* --- Initialize stack pointer and path string --- */
358 /* --- Try to find the current directory --- */
360 if (!getcwd(cwd, sizeof(cwd))) {
361 report(cp, CP_ERROR, 0, 0, "can't find current directory: %e");
365 /* --- Check that the root directory is OK --- */
367 if (stat("/", &st)) {
368 report(cp, CP_ERROR, 0, 0, "can't stat root directory: %e");
372 report(cp, CP_REPORT, 3, p, "begin scan");
373 bad |= sanity("/", &st, cp, 0);
375 /* --- Get the initial list of things to process --- */
377 ee = splitpath(p, 0);
379 ee = splitpath(cwd, ee);
381 /* --- While there are list items which still need doing --- */
386 /* --- Strip off simple `.' elements --- */
388 if (strcmp(ee->e_name, ".") == 0) {
394 /* --- Backtrack on `..' elements --- */
396 else if (strcmp(ee->e_name, "..") == 0) {
403 /* --- Everything else gets pushed on the end --- */
408 /* --- Find out what sort of a thing this is --- */
410 if (lstat(d.buf, &st)) {
411 report(cp, CP_ERROR, 0, d.buf, "can't stat: %e");
416 /* --- Handle symbolic links specially --- */
418 if (S_ISLNK(st.st_mode)) {
419 dstr buf = DSTR_INIT;
422 /* --- Resolve the link --- */
424 dstr_ensure(&buf, st.st_size + 1);
425 if ((i = readlink(d.buf, buf.buf, buf.sz)) < 0) {
426 report(cp, CP_ERROR, 0, d.buf, "can't readlink: %e");
431 report(cp, CP_SYMLINK, 2, d.buf, "symlink -> `%s'", buf.buf);
433 /* --- Handle sticky parents --- *
435 * If I make a symlink in a sticky directory, I can later modify it.
436 * However, nobody else can (except the owner of the directory, and
437 * we'll already have noticed that if we care).
440 if ((cp->cp_what & CP_WROTHUSR) &&
441 (sp->e_link->e_flags & f_sticky) &&
442 st.st_uid != cp->cp_uid && st.st_uid != 0) {
444 report(cp, CP_WROTHUSR, 1, d.buf,
445 "symlink modifiable by user %u", st.st_uid);
448 /* --- Sort out what to do from here --- */
450 if (buf.buf[0] == '/')
454 ee = splitpath(buf.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 /* --- @checkpath_setids@ --- *
493 * Arguments: @struct checkpath *cp@ = pointer to block to fill in
497 * Use: Fills in the user ids and things in the structure.
500 void checkpath_setids(struct checkpath *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 -------------------------------------------------*/