File: [local] / src / usr.bin / doas / doas.c (download)
Revision 1.7, Sat Jul 18 00:19:38 2015 UTC (8 years, 10 months ago) by doug
Branch: MAIN
Changes since 1.6: +13 -8 lines
Add more error checking and use named constants when useful.
ok sthen@ tedu@
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/* $OpenBSD: doas.c,v 1.7 2015/07/18 00:19:38 doug Exp $ */
/*
* Copyright (c) 2015 Ted Unangst <tedu@openbsd.org>
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
#include <sys/types.h>
#include <sys/stat.h>
#include <limits.h>
#include <login_cap.h>
#include <bsd_auth.h>
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <err.h>
#include <unistd.h>
#include <pwd.h>
#include <grp.h>
#include <syslog.h>
#include "doas.h"
static void __dead
usage(void)
{
fprintf(stderr, "usage: doas [-u user] command [args]\n");
exit(1);
}
size_t
arraylen(const char **arr)
{
size_t cnt = 0;
while (*arr) {
cnt++;
arr++;
}
return cnt;
}
static int
parseuid(const char *s, uid_t *uid)
{
struct passwd *pw;
const char *errstr;
if ((pw = getpwnam(s)) != NULL) {
*uid = pw->pw_uid;
return 0;
}
*uid = strtonum(s, 0, UID_MAX, &errstr);
if (errstr)
return -1;
return 0;
}
static int
uidcheck(const char *s, uid_t desired)
{
uid_t uid;
if (parseuid(s, &uid) != 0)
return -1;
if (uid != desired)
return -1;
return 0;
}
static gid_t
strtogid(const char *s)
{
struct group *gr;
const char *errstr;
gid_t gid;
if ((gr = getgrnam(s)) != NULL)
return gr->gr_gid;
gid = strtonum(s, 0, GID_MAX, &errstr);
if (errstr)
return -1;
return gid;
}
static int
match(uid_t uid, gid_t *groups, int ngroups, uid_t target, const char *cmd,
struct rule *r)
{
int i;
if (r->ident[0] == ':') {
gid_t rgid = strtogid(r->ident + 1);
if (rgid == -1)
return 0;
for (i = 0; i < ngroups; i++) {
if (rgid == groups[i])
break;
}
if (i == ngroups)
return 0;
} else {
if (uidcheck(r->ident, uid) != 0)
return 0;
}
if (r->target && uidcheck(r->target, target) != 0)
return 0;
if (r->cmd && strcmp(r->cmd, cmd) != 0)
return 0;
return 1;
}
static int
permit(uid_t uid, gid_t *groups, int ngroups, struct rule **lastr,
uid_t target, const char *cmd)
{
int i;
*lastr = NULL;
for (i = 0; i < nrules; i++) {
if (match(uid, groups, ngroups, target, cmd, rules[i]))
*lastr = rules[i];
}
if (!*lastr)
return 0;
return (*lastr)->action == PERMIT;
}
static void
parseconfig(const char *filename)
{
extern FILE *yyfp;
extern int yyparse(void);
struct stat sb;
yyfp = fopen(filename, "r");
if (!yyfp) {
fprintf(stderr, "doas is not enabled.\n");
exit(1);
}
if (fstat(fileno(yyfp), &sb) != 0)
err(1, "fstat(\"%s\")", filename);
if ((sb.st_mode & (S_IWGRP|S_IWOTH)) != 0)
errx(1, "%s is writable by group or other", filename);
if (sb.st_uid != 0)
errx(1, "%s is not owned by root", filename);
yyparse();
fclose(yyfp);
}
static int
copyenvhelper(const char **oldenvp, const char **safeset, int nsafe,
char **envp, int ei)
{
int i;
for (i = 0; i < nsafe; i++) {
const char **oe = oldenvp;
while (*oe) {
size_t len = strlen(safeset[i]);
if (strncmp(*oe, safeset[i], len) == 0 &&
(*oe)[len] == '=') {
if (!(envp[ei++] = strdup(*oe)))
err(1, "strdup");
break;
}
oe++;
}
}
return ei;
}
static char **
copyenv(const char **oldenvp, struct rule *rule)
{
const char *safeset[] = {
"DISPLAY", "HOME", "LOGNAME", "MAIL", "SHELL",
"PATH", "TERM", "USER", "USERNAME",
NULL,
};
int nsafe;
int nextras = 0;
char **envp;
const char **extra;
int ei;
int i, j;
if ((rule->options & KEEPENV) && !rule->envlist) {
j = arraylen(oldenvp);
envp = reallocarray(NULL, j + 1, sizeof(char *));
if (!envp)
err(1, "reallocarray");
for (i = 0; i < j; i++) {
if (!(envp[i] = strdup(oldenvp[i])))
err(1, "strdup");
}
envp[i] = NULL;
return envp;
}
nsafe = arraylen(safeset);
if ((extra = rule->envlist)) {
nextras = arraylen(extra);
for (i = 0; i < nsafe; i++) {
for (j = 0; j < nextras; j++) {
if (strcmp(extra[j], safeset[i]) == 0) {
extra[j--] = extra[nextras--];
extra[nextras] = NULL;
}
}
}
}
envp = reallocarray(NULL, nsafe + nextras + 1, sizeof(char *));
if (!envp)
err(1, "can't allocate new environment");
ei = 0;
ei = copyenvhelper(oldenvp, safeset, nsafe, envp, ei);
ei = copyenvhelper(oldenvp, rule->envlist, nextras, envp, ei);
envp[ei] = NULL;
return envp;
}
static void __dead
fail(void)
{
fprintf(stderr, "Permission denied\n");
exit(1);
}
int
main(int argc, char **argv, char **envp)
{
char cmdline[LINE_MAX];
char myname[_PW_NAME_LEN + 1];
uid_t uid, target = 0;
gid_t groups[NGROUPS_MAX + 1];
int ngroups;
struct passwd *pw;
struct rule *rule;
const char *cmd;
int i, ch;
const char *safepath = "/bin:/sbin:/usr/bin:/usr/sbin:"
"/usr/local/bin:/usr/local/sbin";
parseconfig("/etc/doas.conf");
while ((ch = getopt(argc, argv, "u:")) != -1) {
switch (ch) {
case 'u':
if (parseuid(optarg, &target) != 0)
errx(1, "unknown user");
break;
default:
usage();
break;
}
}
argv += optind;
argc -= optind;
if (!argc)
usage();
cmd = argv[0];
if (strlcpy(cmdline, argv[0], sizeof(cmdline)) >= sizeof(cmdline))
errx(1, "command line too long");
for (i = 1; i < argc; i++) {
if (strlcat(cmdline, " ", sizeof(cmdline)) >= sizeof(cmdline))
errx(1, "command line too long");
if (strlcat(cmdline, argv[i], sizeof(cmdline)) >= sizeof(cmdline))
errx(1, "command line too long");
}
uid = getuid();
pw = getpwuid(uid);
if (!pw)
err(1, "getpwuid failed");
if (strlcpy(myname, pw->pw_name, sizeof(myname)) >= sizeof(myname))
errx(1, "pw_name too long");
ngroups = getgroups(NGROUPS_MAX, groups);
if (ngroups == -1)
err(1, "can't get groups");
groups[ngroups++] = getgid();
if (!permit(uid, groups, ngroups, &rule, target, cmd)) {
syslog(LOG_AUTHPRIV | LOG_NOTICE,
"failed command for %s: %s", myname, cmdline);
fail();
}
if (!(rule->options & NOPASS)) {
if (!auth_userokay(myname, NULL, NULL, NULL)) {
syslog(LOG_AUTHPRIV | LOG_NOTICE,
"failed password for %s", myname);
fail();
}
}
envp = copyenv((const char **)envp, rule);
pw = getpwuid(target);
if (!pw)
errx(1, "no passwd entry for target");
if (setusercontext(NULL, pw, target, LOGIN_SETGROUP |
LOGIN_SETPRIORITY | LOGIN_SETRESOURCES | LOGIN_SETUMASK |
LOGIN_SETUSER) != 0)
errx(1, "failed to set user context for target");
syslog(LOG_AUTHPRIV | LOG_INFO, "%s ran command as %s: %s",
myname, pw->pw_name, cmdline);
if (setenv("PATH", safepath, 1) == -1)
err(1, "failed to set PATH '%s'", safepath);
execvpe(cmd, argv, envp);
err(1, "%s", cmd);
}