File: [local] / src / usr.bin / doas / doas.c (download)
Revision 1.46, Thu Dec 3 08:12:15 2015 UTC (8 years, 6 months ago) by tedu
Branch: MAIN
Changes since 1.45: +21 -4 lines
use the more direct auth interfaces so we can provide a custom password
prompt to the user (including username and host) so it's always clear what
program is asking. request from henning with a hint from millert.
ok deraadt jung zhuk
|
/* $OpenBSD: doas.c,v 1.46 2015/12/03 08:12:15 tedu 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 <readpassphrase.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 <errno.h>
#include "doas.h"
static void __dead
usage(void)
{
fprintf(stderr, "usage: doas [-ns] [-C config] [-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 int
parsegid(const char *s, gid_t *gid)
{
struct group *gr;
const char *errstr;
if ((gr = getgrnam(s)) != NULL) {
*gid = gr->gr_gid;
return 0;
}
*gid = strtonum(s, 0, GID_MAX, &errstr);
if (errstr)
return -1;
return 0;
}
static int
match(uid_t uid, gid_t *groups, int ngroups, uid_t target, const char *cmd,
const char **cmdargs, struct rule *r)
{
int i;
if (r->ident[0] == ':') {
gid_t rgid;
if (parsegid(r->ident + 1, &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) {
if (strcmp(r->cmd, cmd))
return 0;
if (r->cmdargs) {
/* if arguments were given, they should match explicitly */
for (i = 0; r->cmdargs[i]; i++) {
if (!cmdargs[i])
return 0;
if (strcmp(r->cmdargs[i], cmdargs[i]))
return 0;
}
if (cmdargs[i])
return 0;
}
}
return 1;
}
static int
permit(uid_t uid, gid_t *groups, int ngroups, struct rule **lastr,
uid_t target, const char *cmd, const char **cmdargs)
{
int i;
*lastr = NULL;
for (i = 0; i < nrules; i++) {
if (match(uid, groups, ngroups, target, cmd,
cmdargs, rules[i]))
*lastr = rules[i];
}
if (!*lastr)
return 0;
return (*lastr)->action == PERMIT;
}
static void
parseconfig(const char *filename, int checkperms)
{
extern FILE *yyfp;
extern int yyparse(void);
struct stat sb;
yyfp = fopen(filename, "r");
if (!yyfp)
err(1, checkperms ? "doas is not enabled, %s" :
"could not open config file %s", filename);
if (checkperms) {
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);
if (parse_errors)
exit(1);
}
/*
* Copy the environment variables in safeset from oldenvp to envp.
*/
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",
"PATH", "TERM", "USER", "USERNAME",
NULL
};
const char *badset[] = {
"ENV",
NULL
};
char **envp;
const char **extra;
int ei;
int nsafe, nbad;
int nextras = 0;
/* if there was no envvar whitelist, pass all except badset ones */
nbad = arraylen(badset);
if ((rule->options & KEEPENV) && !rule->envlist) {
size_t iold, inew;
size_t oldlen = arraylen(oldenvp);
envp = reallocarray(NULL, oldlen + 1, sizeof(char *));
if (!envp)
err(1, "reallocarray");
for (inew = iold = 0; iold < oldlen; iold++) {
size_t ibad;
for (ibad = 0; ibad < nbad; ibad++) {
size_t len = strlen(badset[ibad]);
if (strncmp(oldenvp[iold], badset[ibad], len) == 0 &&
oldenvp[iold][len] == '=') {
break;
}
}
if (ibad == nbad) {
if (!(envp[inew] = strdup(oldenvp[iold])))
err(1, "strdup");
inew++;
}
}
envp[inew] = NULL;
return envp;
}
nsafe = arraylen(safeset);
if ((extra = rule->envlist)) {
size_t isafe;
nextras = arraylen(extra);
for (isafe = 0; isafe < nsafe; isafe++) {
size_t iextras;
for (iextras = 0; iextras < nextras; iextras++) {
if (strcmp(extra[iextras], safeset[isafe]) == 0) {
nextras--;
extra[iextras] = extra[nextras];
extra[nextras] = NULL;
iextras--;
}
}
}
}
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
checkconfig(const char *confpath, int argc, char **argv,
uid_t uid, gid_t *groups, int ngroups, uid_t target)
{
struct rule *rule;
setresuid(uid, uid, uid);
parseconfig(confpath, 0);
if (!argc)
exit(0);
if (permit(uid, groups, ngroups, &rule, target, argv[0],
(const char **)argv + 1)) {
printf("permit%s\n", (rule->options & NOPASS) ? " nopass" : "");
exit(0);
} else {
printf("deny\n");
exit(1);
}
}
int
main(int argc, char **argv, char **envp)
{
const char *safepath = "/bin:/sbin:/usr/bin:/usr/sbin:"
"/usr/local/bin:/usr/local/sbin";
const char *confpath = NULL;
char *shargv[] = { NULL, NULL };
char *sh;
const char *cmd;
char cmdline[LINE_MAX];
char myname[_PW_NAME_LEN + 1];
struct passwd *pw;
struct rule *rule;
uid_t uid;
uid_t target = 0;
gid_t groups[NGROUPS_MAX + 1];
int ngroups;
int i, ch;
int sflag = 0;
int nflag = 0;
char cwdpath[PATH_MAX];
const char *cwd;
if (pledge("stdio rpath getpw tty proc exec id", NULL) == -1)
err(1, "pledge");
closefrom(STDERR_FILENO + 1);
uid = getuid();
while ((ch = getopt(argc, argv, "C:nsu:")) != -1) {
switch (ch) {
case 'C':
confpath = optarg;
break;
case 'u':
if (parseuid(optarg, &target) != 0)
errx(1, "unknown user");
break;
case 'n':
nflag = 1;
break;
case 's':
sflag = 1;
break;
default:
usage();
break;
}
}
argv += optind;
argc -= optind;
if (confpath) {
if (sflag)
usage();
} else if ((!sflag && !argc) || (sflag && argc))
usage();
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 (sflag) {
sh = getenv("SHELL");
if (sh == NULL || *sh == '\0')
shargv[0] = pw->pw_shell;
else
shargv[0] = sh;
argv = shargv;
argc = 1;
}
if (confpath) {
checkconfig(confpath, argc, argv, uid, groups, ngroups,
target);
exit(1); /* fail safe */
}
parseconfig("/etc/doas.conf", 1);
/* cmdline is used only for logging, no need to abort on truncate */
(void) strlcpy(cmdline, argv[0], sizeof(cmdline));
for (i = 1; i < argc; i++) {
if (strlcat(cmdline, " ", sizeof(cmdline)) >= sizeof(cmdline))
break;
if (strlcat(cmdline, argv[i], sizeof(cmdline)) >= sizeof(cmdline))
break;
}
cmd = argv[0];
if (!permit(uid, groups, ngroups, &rule, target, cmd,
(const char**)argv + 1)) {
syslog(LOG_AUTHPRIV | LOG_NOTICE,
"failed command for %s: %s", myname, cmdline);
errc(1, EPERM, NULL);
}
if (!(rule->options & NOPASS)) {
char *challenge = NULL, *response, rbuf[1024], cbuf[128];
auth_session_t *as;
if (nflag)
errx(1, "Authorization required");
if (!(as = auth_userchallenge(myname, NULL, "auth-doas",
&challenge)))
err(1, "auth challenge failed");
if (!challenge) {
char host[HOST_NAME_MAX + 1];
if (gethostname(host, sizeof(host)))
snprintf(host, sizeof(host), "?");
snprintf(cbuf, sizeof(cbuf),
"doas (%.32s@%.32s) password: ", myname, host);
challenge = cbuf;
}
response = readpassphrase(challenge, rbuf, sizeof(rbuf), 0);
if (!auth_userresponse(as, response, 0)) {
syslog(LOG_AUTHPRIV | LOG_NOTICE,
"failed auth for %s", myname);
errc(1, EPERM, NULL);
}
}
if (pledge("stdio rpath getpw exec id", NULL) == -1)
err(1, "pledge");
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");
if (pledge("stdio rpath exec", NULL) == -1)
err(1, "pledge");
if (getcwd(cwdpath, sizeof(cwdpath)) == NULL)
cwd = "(failed)";
else
cwd = cwdpath;
if (pledge("stdio exec", NULL) == -1)
err(1, "pledge");
syslog(LOG_AUTHPRIV | LOG_INFO, "%s ran command %s as %s from %s",
myname, cmdline, pw->pw_name, cwd);
envp = copyenv((const char **)envp, rule);
if (rule->cmd) {
if (setenv("PATH", safepath, 1) == -1)
err(1, "failed to set PATH '%s'", safepath);
}
execvpe(cmd, argv, envp);
if (errno == ENOENT)
errx(1, "%s: command not found", cmd);
err(1, "%s", cmd);
}