-/* -*-c-*-
- *
- * $Id: path.c,v 1.4 2001/01/25 22:16:02 mdw Exp $
- *
- * Check a path for safety
- *
- * (c) 1999 Mark Wooding
- */
-
-/*----- Licensing notice --------------------------------------------------*
- *
- * This file is part of chkpath.
- *
- * chkpath is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation; either version 2 of the License, or
- * (at your option) any later version.
- *
- * chkpath is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
- * GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with chkpath; if not, write to the Free Software Foundation,
- * Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
- */
-
-/*----- Revision history --------------------------------------------------*
- *
- * $Log: path.c,v $
- * Revision 1.4 2001/01/25 22:16:02 mdw
- * Make flags be unsigned.
- *
- * Revision 1.3 1999/05/21 22:07:20 mdw
- * Take advantage of new dynamic string macros.
- *
- * Revision 1.2 1999/05/18 20:49:12 mdw
- * Use a dynamic string for reading symlinks.
- *
- * Revision 1.1.1.1 1999/04/06 20:12:07 mdw
- * Import new project.
- *
- */
-
-/*----- Header files ------------------------------------------------------*/
-
-#include <errno.h>
-#include <stdarg.h>
-#include <stdio.h>
-#include <stdlib.h>
-#include <string.h>
-
-#include <sys/types.h>
-#include <sys/stat.h>
-#include <unistd.h>
-
-#include <pwd.h>
-#include <grp.h>
-
-#include <mLib/alloc.h>
-#include <mLib/dstr.h>
-
-#include "path.h"
-
-/*----- Data structures ---------------------------------------------------*/
-
-/* --- An item in the directory list --- *
- *
- * Each directory becomes an element on a list which is manipulated in a
- * stack-like way.
- */
-
-struct elt {
- struct elt *e_link; /* Pointer to the next one along */
- size_t e_offset; /* Offset of name in path string */
- unsigned e_flags; /* Various useful flags */
- char e_name[1]; /* Name of the directory */
-};
-
-#define f_sticky 1u /* Directory has sticky bit set */
-
-#define f_last 1u /* This is the final item to check */
-
-/*----- Static variables --------------------------------------------------*/
-
-static struct elt rootnode = { 0, 0, 0 }; /* Root of the list */
-static struct elt *sp; /* Stack pointer for list */
-static dstr d = DSTR_INIT; /* Current path string */
-
-/*----- Main code ---------------------------------------------------------*/
-
-/* --- @splitpath@ --- *
- *
- * Arguments: @const char *path@ = path string to break apart
- * @struct elt *tail@ = tail block to attach to end of list
- *
- * Returns: Pointer to the new list head.
- *
- * Use: Breaks a path string into directories and adds each one
- * as a node on the list, in the right order. These can then
- * be pushed onto the directory stack as required.
- */
-
-static struct elt *splitpath(const char *path, struct elt *tail)
-{
- struct elt *head, **ee = &head, *e;
-
- while (*path) {
- size_t n;
-
- /* --- Either a leading `/', or a doubled one --- *
- *
- * Either way, ignore it.
- */
-
- if (*path == '/') {
- path++;
- continue;
- }
-
- /* --- Skip to the next directory separator --- *
- *
- * Build a list element for it, and link it on.
- */
-
- n = strcspn(path, "/");
- e = xmalloc(sizeof(struct elt) + n + 1);
- memcpy(e->e_name, path, n);
- e->e_name[n] = 0;
- e->e_flags = 0;
- *ee = e;
- ee = &e->e_link;
- path += n;
- }
-
- /* --- Done --- */
-
- *ee = tail;
- return (head);
-}
-
-/* --- @pop@ --- *
- *
- * Arguments: ---
- *
- * Returns: ---
- *
- * Use: Removes the top item from the directory stack.
- */
-
-static void pop(void)
-{
- if (sp->e_link) {
- struct elt *e = sp->e_link;
- d.len = sp->e_offset;
- DPUTZ(&d);
- sp = e;
- }
-}
-
-/* --- @popall@ --- *
- *
- * Arguments: ---
- *
- * Returns: ---
- *
- * Use: Removes all the items from the directory stack.
- */
-
-static void popall(void)
-{
- while (sp->e_link)
- pop();
-}
-
-/* --- @push@ --- *
- *
- * Arguments: @struct elt *e@ = pointer to directory element
- *
- * Returns: ---
- *
- * Use: Pushes a new subdirectory onto the stack.
- */
-
-static void push(struct elt *e)
-{
- e->e_link = sp;
- e->e_offset = d.len;
- DPUTC(&d, '/');
- DPUTS(&d, e->e_name);
- sp = e;
-}
-
-/* --- @report@ --- *
- *
- * Arguments: @struct chkpath *cp@ = pointer to context
- * @int what@ = what sort of report is this?
- * @int verbose@ = how verbose is this?
- * @const char *p@ = what path does it refer to?
- * @const char *msg@ = the message to give to the user
- *
- * Returns: ---
- *
- * Use: Formats and presents messages to the client.
- */
-
-static void report(struct chkpath *cp, int what, int verbose,
- const char *p, const char *msg, ...)
-{
- /* --- Decide whether to bin this message --- */
-
- if (!cp->cp_report || verbose > cp->cp_verbose || !(cp->cp_what & what))
- return;
-
- /* --- Format the message nicely --- */
-
- if (cp->cp_what & CP_REPORT) {
- dstr d = DSTR_INIT;
- va_list ap;
- const char *q = msg;
- size_t n;
- int e = errno;
-
- va_start(ap, msg);
- if (verbose > 1)
- dstr_puts(&d, "[ ");
- if (p)
- dstr_putf(&d, "Path: %s: ", p);
- while (*q) {
- if (*q == '%') {
- q++;
- switch (*q) {
- case 'e':
- dstr_puts(&d, strerror(e));
- break;
- case 'u': {
- uid_t u = (uid_t)va_arg(ap, int);
- struct passwd *pw = getpwuid(u);
- if (pw)
- dstr_putf(&d, "`%s'", pw->pw_name);
- else
- dstr_putf(&d, "%i", (int)u);
- } break;
- case 'g': {
- gid_t g = (gid_t)va_arg(ap, int);
- struct group *gr = getgrgid(g);
- if (gr)
- dstr_putf(&d, "`%s'", gr->gr_name);
- else
- dstr_putf(&d, "%i", (int)g);
- } break;
- case 's': {
- const char *s = va_arg(ap, const char *);
- dstr_puts(&d, s);
- } break;
- case '%':
- dstr_putc(&d, '%');
- break;
- default:
- dstr_putc(&d, '%');
- dstr_putc(&d, *q);
- break;
- }
- q++;
- } else {
- n = strcspn(q, "%");
- DPUTM(&d, q, n);
- q += n;
- }
- }
- if (verbose > 1)
- dstr_puts(&d, " ]");
- DPUTZ(&d);
- cp->cp_report(what, verbose, p, d.buf, cp->cp_arg);
- dstr_destroy(&d);
- va_end(ap);
- } else
- cp->cp_report(what, verbose, p, 0, cp->cp_arg);
-}
-
-/* --- @sanity@ --- *
- *
- * Arguments: @const char *p@ = name of directory to check
- * @struct stat *st@ = pointer to @stat@(2) block for it
- * @struct chkpath *cp@ = pointer to caller parameters
- * @unsigned f@ = various flags
- *
- * Returns: Zero if everything's OK, else bitmask of problems.
- *
- * Use: Performs the main load of sanity-checking on a directory.
- */
-
-static int sanity(const char *p, struct stat *st,
- struct chkpath *cp, unsigned f)
-{
- int bad = 0;
- int sticky = (cp->cp_what & CP_STICKYOK) || !(f & f_last) ? 01000 : 0;
-
- /* --- Check for world-writability --- */
-
- if ((cp->cp_what & CP_WRWORLD) &&
- (st->st_mode & (0002 | sticky)) == 0002) {
- bad |= CP_WRWORLD;
- report(cp, CP_WRWORLD, 1, p, "** world writable **");
- }
-
- /* --- Check for group-writability --- */
-
- if ((cp->cp_what & (CP_WRGRP | CP_WROTHGRP)) &&
- (st->st_mode & (0020 | sticky)) == 0020) {
- if (cp->cp_what & CP_WRGRP) {
- bad |= CP_WRGRP;
- report(cp, CP_WRGRP, 1, p, "writable by group %g", st->st_gid);
- } else {
- int i;
- for (i = 0; i < cp->cp_gids; i++) {
- if (st->st_gid == cp->cp_gid[i])
- goto good_gid;
- }
- bad |= CP_WROTHGRP;
- report(cp, CP_WROTHGRP, 1, p, "writable by group %g", st->st_gid);
- good_gid:;
- }
- }
-
- /* --- Check for user-writability --- */
-
- if ((cp->cp_what & CP_WROTHUSR) &&
- st->st_uid != cp->cp_uid &&
- st->st_uid != 0) {
- bad |= CP_WROTHUSR;
- report(cp, CP_WROTHUSR, 1, p, "owner is user %u", st->st_uid);
- }
-
- /* --- Done sanity check --- */
-
- return (bad);
-}
-
-/* --- @path_check@ --- *
- *
- * Arguments: @const char *p@ = directory name which needs checking
- * @struct chkpath *cp@ = caller parameters for the check
- *
- * Returns: Zero if all is well, otherwise bitmask of problems.
- *
- * Use: Scrutinises a directory path to see what evil things other
- * users could do to it.
- */
-
-int path_check(const char *p, struct chkpath *cp)
-{
- char cwd[PATH_MAX];
- struct elt *e, *ee;
- struct stat st;
- int bad = 0;
-
- /* --- Initialize stack pointer and path string --- */
-
- sp = &rootnode;
- dstr_destroy(&d);
-
- /* --- Try to find the current directory --- */
-
- if (!getcwd(cwd, sizeof(cwd))) {
- report(cp, CP_ERROR, 0, 0, "can't find current directory: %e");
- return (CP_ERROR);
- }
-
- /* --- Check that the root directory is OK --- */
-
- if (stat("/", &st)) {
- report(cp, CP_ERROR, 0, 0, "can't stat root directory: %e");
- return (CP_ERROR);
- }
-
- report(cp, CP_REPORT, 3, p, "begin scan");
- bad |= sanity("/", &st, cp, 0);
-
- /* --- Get the initial list of things to process --- */
-
- ee = splitpath(p, 0);
- if (*p != '/')
- ee = splitpath(cwd, ee);
-
- /* --- While there are list items which still need doing --- */
-
- while (ee) {
- e = ee->e_link;
-
- /* --- Strip off simple `.' elements --- */
-
- if (strcmp(ee->e_name, ".") == 0) {
- free(ee);
- ee = e;
- continue;
- }
-
- /* --- Backtrack on `..' elements --- */
-
- else if (strcmp(ee->e_name, "..") == 0) {
- pop();
- free(ee);
- ee = e;
- continue;
- }
-
- /* --- Everything else gets pushed on the end --- */
-
- push(ee);
- ee = e;
-
- /* --- Find out what sort of a thing this is --- */
-
- if (lstat(d.buf, &st)) {
- report(cp, CP_ERROR, 0, d.buf, "can't stat: %e");
- bad |= CP_ERROR;
- break;
- }
-
- /* --- Handle symbolic links specially --- */
-
- if (S_ISLNK(st.st_mode)) {
- dstr buf = DSTR_INIT;
- int i;
-
- /* --- Resolve the link --- */
-
- dstr_ensure(&buf, st.st_size + 1);
- if ((i = readlink(d.buf, buf.buf, buf.sz)) < 0) {
- report(cp, CP_ERROR, 0, d.buf, "can't readlink: %e");
- bad |= CP_ERROR;
- break;
- }
- buf.buf[i] = 0;
- report(cp, CP_SYMLINK, 2, d.buf, "symlink -> `%s'", buf.buf);
-
- /* --- Handle sticky parents --- *
- *
- * If I make a symlink in a sticky directory, I can later modify it.
- * However, nobody else can (except the owner of the directory, and
- * we'll already have noticed that if we care).
- */
-
- if ((cp->cp_what & CP_WROTHUSR) &&
- (sp->e_link->e_flags & f_sticky) &&
- st.st_uid != cp->cp_uid && st.st_uid != 0) {
- bad |= CP_WROTHUSR;
- report(cp, CP_WROTHUSR, 1, d.buf,
- "symlink modifiable by user %u", st.st_uid);
- }
-
- /* --- Sort out what to do from here --- */
-
- if (buf.buf[0] == '/')
- popall();
- else
- pop();
- ee = splitpath(buf.buf, ee);
- dstr_destroy(&buf);
- continue;
- }
-
- /* --- Run the sanity check on this path element --- */
-
- bad |= sanity(d.buf, &st, cp, ee ? 0 : f_last);
-
- if (S_ISDIR(st.st_mode)) {
- if (st.st_mode & 01000)
- sp->e_flags |= f_sticky;
- report(cp, CP_REPORT, 4, d.buf, "directory");
- continue;
- }
-
- /* --- Something else I don't understand --- */
-
- break;
- }
-
- /* --- Check for leftover junk --- */
-
- if (ee) {
- if (!(bad & CP_ERROR))
- report(cp, CP_ERROR, 0, 0, "junk left over after reaching leaf");
- while (ee) {
- e = ee->e_link;
- free(ee);
- ee = e;
- }
- }
-
- popall();
- return (bad);
-}
-
-/* --- @path_setids@ --- *
- *
- * Arguments: @struct chkpath *cp@ = pointer to block to fill in
- *
- * Returns: Zero if OK, else @-1@.
- *
- * Use: Fills in the user ids and things in the structure.
- */
-
-void path_setids(struct chkpath *cp)
-{
- int n, i;
- gid_t g = getgid();
-
- cp->cp_uid = getuid();
- n = getgroups(sizeof(cp->cp_gid) / sizeof(cp->cp_gid[0]), cp->cp_gid);
-
- for (i = 0; i < n; i++) {
- if (cp->cp_gid[i] == g)
- goto gid_ok;
- }
- cp->cp_gid[n++] = g;
-gid_ok:
- cp->cp_gids = n;
-}
-
-/*----- That's all, folks -------------------------------------------------*/
~mdw / checkpath / commitdiff