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 ------------------------------------------------------*/
35 #include <sys/types.h>
42 #include <mLib/alloc.h>
43 #include <mLib/dstr.h>
45 #include "checkpath.h"
47 /*----- Data structures ---------------------------------------------------*/
49 /* --- An item in the directory list --- *
51 * Each directory becomes an element on a list which is manipulated in a
56 struct elt
*e_link
; /* Pointer to the next one along */
57 size_t e_offset
; /* Offset of name in path string */
58 unsigned e_flags
; /* Various useful flags */
59 char e_name
[1]; /* Name of the directory */
62 #define f_sticky 1u /* Directory has sticky bit set */
64 #define f_last 1u /* This is the final item to check */
66 /*----- Static variables --------------------------------------------------*/
68 static struct elt rootnode
= { 0, 0, 0 }; /* Root of the list */
69 static struct elt
*sp
; /* Stack pointer for list */
70 static dstr d
= DSTR_INIT
; /* Current path string */
72 /*----- Main code ---------------------------------------------------------*/
74 /* --- @splitpath@ --- *
76 * Arguments: @const char *path@ = path string to break apart
77 * @struct elt *tail@ = tail block to attach to end of list
79 * Returns: Pointer to the new list head.
81 * Use: Breaks a path string into directories and adds each one
82 * as a node on the list, in the right order. These can then
83 * be pushed onto the directory stack as required.
86 static struct elt
*splitpath(const char *path
, struct elt
*tail
)
88 struct elt
*head
, **ee
= &head
, *e
;
93 /* --- Either a leading `/', or a doubled one --- *
95 * Either way, ignore it.
103 /* --- Skip to the next directory separator --- *
105 * Build a list element for it, and link it on.
108 n
= strcspn(path
, "/");
109 e
= xmalloc(sizeof(struct elt
) + n
+ 1);
110 memcpy(e
->e_name
, path
, n
);
130 * Use: Removes the top item from the directory stack.
133 static void pop(void)
136 struct elt
*e
= sp
->e_link
;
137 d
.len
= sp
->e_offset
;
143 /* --- @popall@ --- *
149 * Use: Removes all the items from the directory stack.
152 static void popall(void)
153 { while (sp
->e_link
) pop(); }
157 * Arguments: @struct elt *e@ = pointer to directory element
161 * Use: Pushes a new subdirectory onto the stack.
164 static void push(struct elt
*e
)
169 DPUTS(&d
, e
->e_name
);
173 /* --- @report@ --- *
175 * Arguments: @const struct checkpath *cp@ = pointer to context
176 * @unsigned what@ = what sort of report is this?
177 * @int verbose@ = how verbose is this?
178 * @const char *p@ = what path does it refer to?
179 * @const char *msg@ = the message to give to the user
183 * Use: Formats and presents messages to the client.
186 static void report(const struct checkpath
*cp
, unsigned what
, int verbose
,
187 const char *p
, const char *msg
, ...)
200 /* --- Decide whether to bin this message --- */
202 if (!cp
->cp_report
|| verbose
> cp
->cp_verbose
|| !(cp
->cp_what
& what
))
205 /* --- If no reporting, do the easy thing --- */
207 if (!(cp
->cp_what
& CP_REPORT
)) {
208 cp
->cp_report(what
, verbose
, p
, 0, cp
->cp_arg
);
212 /* --- Format the message nicely --- */
218 dstr_putf(&d
, "Path: %s: ", p
);
224 dstr_puts(&d
, strerror(e
));
227 u
= (uid_t
)va_arg(ap
, int);
228 if ((pw
= getpwuid(u
)) != 0)
229 dstr_putf(&d
, "`%s'", pw
->pw_name
);
231 dstr_putf(&d
, "%i", (int)u
);
234 g
= (gid_t
)va_arg(ap
, int);
235 if ((gr
= getgrgid(g
)) != 0)
236 dstr_putf(&d
, "`%s'", gr
->gr_name
);
238 dstr_putf(&d
, "%i", (int)g
);
241 s
= va_arg(ap
, const char *);
262 cp
->cp_report(what
, verbose
, p
, d
.buf
, cp
->cp_arg
);
267 /* --- @sanity@ --- *
269 * Arguments: @const char *p@ = name of directory to check
270 * @struct stat *st@ = pointer to @stat@(2) block for it
271 * @const struct checkpath *cp@ = pointer to caller parameters
272 * @unsigned f@ = various flags
274 * Returns: Zero if everything's OK, else bitmask of problems.
276 * Use: Performs the main load of sanity-checking on a directory.
279 static unsigned sanity(const char *p
, struct stat
*st
,
280 const struct checkpath
*cp
, unsigned f
)
287 if (S_ISDIR(st
->st_mode
) &&
288 (!(f
& f_last
) || (cp
->cp_what
& CP_STICKYOK
)))
291 /* --- Check for world-writability --- */
293 if ((cp
->cp_what
& CP_WRWORLD
) &&
294 (st
->st_mode
& (0002 | stickyok
)) == 0002) {
296 report(cp
, CP_WRWORLD
, 1, p
, "** world writable **");
299 /* --- Check for group-writability --- */
301 if ((cp
->cp_what
& (CP_WRGRP
| CP_WROTHGRP
)) &&
302 (st
->st_mode
& (0020 | stickyok
)) == 0020) {
305 if (cp
->cp_what
& CP_WROTHGRP
) {
307 for (i
= 0; i
< cp
->cp_gids
; i
++) {
308 if (st
->st_gid
== cp
->cp_gid
[i
])
309 b
= cp
->cp_what
& CP_WRGRP
;
314 report(cp
, b
, 1, p
, "writable by %sgroup %g",
315 (b
== CP_WROTHGRP
) ?
"other " : "", st
->st_gid
);
319 /* --- Check for user-writability --- */
321 if ((cp
->cp_what
& CP_WROTHUSR
) &&
322 st
->st_uid
!= cp
->cp_uid
&&
325 report(cp
, CP_WROTHUSR
, 1, p
, "owner is user %u", st
->st_uid
);
328 /* --- Done sanity check --- */
333 /* --- @checkpath@ --- *
335 * Arguments: @const char *p@ = directory name which needs checking
336 * @const struct checkpath *cp@ = parameters for the check
338 * Returns: Zero if all is well, otherwise bitmask of problems.
340 * Use: Scrutinises a directory path to see what evil things other
341 * users could do to it.
344 unsigned checkpath(const char *p
, const struct checkpath
*cp
)
351 /* --- Initialize stack pointer and path string --- */
356 /* --- Try to find the current directory --- */
358 if (!getcwd(cwd
, sizeof(cwd
))) {
359 report(cp
, CP_ERROR
, 0, 0, "can't find current directory: %e");
363 /* --- Check that the root directory is OK --- */
365 if (stat("/", &st
)) {
366 report(cp
, CP_ERROR
, 0, 0, "can't stat root directory: %e");
370 report(cp
, CP_REPORT
, 3, p
, "begin scan");
371 bad
|= sanity("/", &st
, cp
, 0);
373 /* --- Get the initial list of things to process --- */
375 ee
= splitpath(p
, 0);
377 ee
= splitpath(cwd
, ee
);
379 /* --- While there are list items which still need doing --- */
384 /* --- Strip off simple `.' elements --- */
386 if (strcmp(ee
->e_name
, ".") == 0) {
392 /* --- Backtrack on `..' elements --- */
394 else if (strcmp(ee
->e_name
, "..") == 0) {
401 /* --- Everything else gets pushed on the end --- */
406 /* --- Find out what sort of a thing this is --- */
408 if (lstat(d
.buf
, &st
)) {
409 report(cp
, CP_ERROR
, 0, d
.buf
, "can't stat: %e");
414 /* --- Handle symbolic links specially --- */
416 if (S_ISLNK(st
.st_mode
)) {
417 dstr buf
= DSTR_INIT
;
420 /* --- Resolve the link --- */
422 dstr_ensure(&buf
, st
.st_size
+ 1);
423 if ((i
= readlink(d
.buf
, buf
.buf
, buf
.sz
)) < 0) {
424 report(cp
, CP_ERROR
, 0, d
.buf
, "can't readlink: %e");
429 report(cp
, CP_SYMLINK
, 2, d
.buf
, "symlink -> `%s'", buf
.buf
);
431 /* --- Handle sticky parents --- *
433 * If I make a symlink in a sticky directory, I can later modify it.
434 * However, nobody else can (except the owner of the directory, and
435 * we'll already have noticed that if we care).
438 if ((cp
->cp_what
& CP_WROTHUSR
) &&
439 (sp
->e_link
->e_flags
& f_sticky
) &&
440 st
.st_uid
!= cp
->cp_uid
&& st
.st_uid
!= 0) {
442 report(cp
, CP_WROTHUSR
, 1, d
.buf
,
443 "symlink modifiable by user %u", st
.st_uid
);
446 /* --- Sort out what to do from here --- */
448 if (buf
.buf
[0] == '/')
452 ee
= splitpath(buf
.buf
, ee
);
457 /* --- Run the sanity check on this path element --- */
459 bad
|= sanity(d
.buf
, &st
, cp
, ee ?
0 : f_last
);
461 if (S_ISDIR(st
.st_mode
)) {
462 if (st
.st_mode
& 01000)
463 sp
->e_flags
|= f_sticky
;
464 report(cp
, CP_REPORT
, 4, d
.buf
, "directory");
468 /* --- Something else I don't understand --- */
473 /* --- Check for leftover junk --- */
476 if (!(bad
& CP_ERROR
))
477 report(cp
, CP_ERROR
, 0, 0, "junk left over after reaching leaf");
489 /* --- @checkpath_setids@ --- *
491 * Arguments: @struct checkpath *cp@ = pointer to block to fill in
495 * Use: Fills in the user ids and things in the structure.
498 void checkpath_setids(struct checkpath
*cp
)
503 cp
->cp_uid
= getuid();
504 n
= getgroups(sizeof(cp
->cp_gid
) / sizeof(cp
->cp_gid
[0]), cp
->cp_gid
);
506 for (i
= 0; i
< n
; i
++) {
507 if (cp
->cp_gid
[i
] == g
)
515 /*----- That's all, folks -------------------------------------------------*/