499 lines
13 KiB
C
499 lines
13 KiB
C
/* $OpenBSD: doas.c,v 1.99 2024/02/15 18:57:58 tedu Exp $ */
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/*
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* Copyright (c) 2015 Ted Unangst <tedu@openbsd.org>
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*
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* Permission to use, copy, modify, and distribute this software for any
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* purpose with or without fee is hereby granted, provided that the above
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* copyright notice and this permission notice appear in all copies.
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*
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* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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*/
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#include <sys/types.h>
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#include <sys/stat.h>
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#include <sys/ioctl.h>
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#include <limits.h>
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#include <login_cap.h>
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#include <bsd_auth.h>
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#include <readpassphrase.h>
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#include <string.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <err.h>
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#include <unistd.h>
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#include <pwd.h>
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#include <grp.h>
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#include <syslog.h>
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#include <errno.h>
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#include <fcntl.h>
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#include "doas.h"
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static void __dead
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usage(void)
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{
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fprintf(stderr, "usage: doas [-Lns] [-a style] [-C config] [-u user]"
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" command [arg ...]\n");
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exit(1);
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}
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static int
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parseuid(const char *s, uid_t *uid)
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{
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struct passwd *pw;
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const char *errstr;
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if ((pw = getpwnam(s)) != NULL) {
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*uid = pw->pw_uid;
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if (*uid == UID_MAX)
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return -1;
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return 0;
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}
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*uid = strtonum(s, 0, UID_MAX - 1, &errstr);
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if (errstr)
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return -1;
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return 0;
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}
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static int
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uidcheck(const char *s, uid_t desired)
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{
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uid_t uid;
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if (parseuid(s, &uid) != 0)
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return -1;
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if (uid != desired)
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return -1;
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return 0;
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}
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static int
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parsegid(const char *s, gid_t *gid)
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{
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struct group *gr;
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const char *errstr;
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if ((gr = getgrnam(s)) != NULL) {
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*gid = gr->gr_gid;
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if (*gid == GID_MAX)
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return -1;
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return 0;
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}
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*gid = strtonum(s, 0, GID_MAX - 1, &errstr);
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if (errstr)
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return -1;
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return 0;
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}
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static int
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match(uid_t uid, gid_t *groups, int ngroups, uid_t target, const char *cmd,
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const char **cmdargs, struct rule *r)
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{
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int i;
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if (r->ident[0] == ':') {
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gid_t rgid;
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if (parsegid(r->ident + 1, &rgid) == -1)
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return 0;
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for (i = 0; i < ngroups; i++) {
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if (rgid == groups[i])
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break;
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}
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if (i == ngroups)
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return 0;
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} else {
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if (uidcheck(r->ident, uid) != 0)
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return 0;
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}
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if (r->target && uidcheck(r->target, target) != 0)
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return 0;
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if (r->cmd) {
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if (strcmp(r->cmd, cmd))
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return 0;
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if (r->cmdargs) {
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/* if arguments were given, they should match explicitly */
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for (i = 0; r->cmdargs[i]; i++) {
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if (!cmdargs[i])
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return 0;
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if (strcmp(r->cmdargs[i], cmdargs[i]))
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return 0;
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}
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if (cmdargs[i])
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return 0;
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}
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}
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return 1;
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}
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static int
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permit(uid_t uid, gid_t *groups, int ngroups, const struct rule **lastr,
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uid_t target, const char *cmd, const char **cmdargs)
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{
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size_t i;
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*lastr = NULL;
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for (i = 0; i < nrules; i++) {
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if (match(uid, groups, ngroups, target, cmd,
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cmdargs, rules[i]))
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*lastr = rules[i];
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}
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if (!*lastr)
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return -1;
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if ((*lastr)->action == PERMIT)
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return 0;
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return -1;
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}
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static void
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parseconfig(const char *filename, int checkperms)
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{
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extern FILE *yyfp;
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extern int yyparse(void);
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struct stat sb;
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yyfp = fopen(filename, "r");
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if (!yyfp)
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err(1, checkperms ? "doas is not enabled, %s" :
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"could not open config file %s", filename);
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if (checkperms) {
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if (fstat(fileno(yyfp), &sb) != 0)
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err(1, "fstat(\"%s\")", filename);
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if ((sb.st_mode & (S_IWGRP|S_IWOTH)) != 0)
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errx(1, "%s is writable by group or other", filename);
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if (sb.st_uid != 0)
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errx(1, "%s is not owned by root", filename);
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}
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yyparse();
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fclose(yyfp);
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if (parse_error)
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exit(1);
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}
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static void __dead
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checkconfig(const char *confpath, int argc, char **argv,
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uid_t uid, gid_t *groups, int ngroups, uid_t target)
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{
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const struct rule *rule;
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int rv;
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setresuid(uid, uid, uid);
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if (pledge("stdio rpath getpw", NULL) == -1)
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err(1, "pledge");
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parseconfig(confpath, 0);
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if (!argc)
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exit(0);
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rv = permit(uid, groups, ngroups, &rule, target, argv[0],
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(const char **)argv + 1);
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if (rv == 0) {
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printf("permit%s\n", (rule->options & NOPASS) ? " nopass" : "");
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exit(0);
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} else {
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printf("deny\n");
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exit(1);
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}
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}
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static int
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authuser_checkpass(char *myname, char *login_style)
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{
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char *challenge = NULL, *response, rbuf[1024], cbuf[128];
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auth_session_t *as;
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if (!(as = auth_userchallenge(myname, login_style, "auth-doas",
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&challenge))) {
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warnx("Authentication failed");
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return AUTH_FAILED;
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}
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if (!challenge) {
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char host[HOST_NAME_MAX + 1];
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if (gethostname(host, sizeof(host)))
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snprintf(host, sizeof(host), "?");
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snprintf(cbuf, sizeof(cbuf),
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"\rdoas (%.32s@%.32s) password: ", myname, host);
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challenge = cbuf;
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}
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response = readpassphrase(challenge, rbuf, sizeof(rbuf),
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RPP_REQUIRE_TTY);
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if (response == NULL && errno == ENOTTY) {
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syslog(LOG_AUTHPRIV | LOG_NOTICE,
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"tty required for %s", myname);
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errx(1, "a tty is required");
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}
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if (!auth_userresponse(as, response, 0)) {
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explicit_bzero(rbuf, sizeof(rbuf));
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syslog(LOG_AUTHPRIV | LOG_NOTICE,
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"failed auth for %s", myname);
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warnx("Authentication failed");
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return AUTH_FAILED;
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}
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explicit_bzero(rbuf, sizeof(rbuf));
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return AUTH_OK;
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}
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static void
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authuser(char *myname, char *login_style, int persist)
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{
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int i, fd = -1;
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if (persist)
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fd = open("/dev/tty", O_RDWR);
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if (fd != -1) {
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if (ioctl(fd, TIOCCHKVERAUTH) == 0)
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goto good;
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}
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for (i = 0; i < AUTH_RETRIES; i++) {
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if (authuser_checkpass(myname, login_style) == AUTH_OK)
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goto good;
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}
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exit(1);
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good:
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if (fd != -1) {
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int secs = 5 * 60;
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ioctl(fd, TIOCSETVERAUTH, &secs);
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close(fd);
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}
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}
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int
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unveilcommands(const char *ipath, const char *cmd)
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{
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char *path = NULL, *p;
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int unveils = 0;
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if (strchr(cmd, '/') != NULL) {
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if (unveil(cmd, "x") != -1)
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unveils++;
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goto done;
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}
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if (!ipath) {
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errno = ENOENT;
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goto done;
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}
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path = strdup(ipath);
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if (!path) {
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errno = ENOENT;
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goto done;
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}
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for (p = path; p && *p; ) {
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char buf[PATH_MAX];
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char *cp = strsep(&p, ":");
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if (cp) {
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int r = snprintf(buf, sizeof buf, "%s/%s", cp, cmd);
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if (r >= 0 && r < sizeof buf) {
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if (unveil(buf, "x") != -1)
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unveils++;
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}
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}
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}
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done:
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free(path);
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return (unveils);
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}
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int
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main(int argc, char **argv)
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{
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const char *safepath = "/bin:/sbin:/usr/bin:/usr/sbin:"
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"/usr/local/bin:/usr/local/sbin";
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const char *confpath = NULL;
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char *shargv[] = { NULL, NULL };
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char *sh;
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const char *p;
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const char *cmd;
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char cmdline[LINE_MAX];
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char mypwbuf[_PW_BUF_LEN], targpwbuf[_PW_BUF_LEN];
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struct passwd mypwstore, targpwstore;
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struct passwd *mypw, *targpw;
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const struct rule *rule;
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uid_t uid;
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uid_t target = 0;
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gid_t groups[NGROUPS_MAX + 1];
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int ngroups;
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int i, ch, rv;
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int sflag = 0;
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int nflag = 0;
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char cwdpath[PATH_MAX];
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const char *cwd;
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char *login_style = NULL;
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char **envp;
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setprogname("doas");
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closefrom(STDERR_FILENO + 1);
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uid = getuid();
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while ((ch = getopt(argc, argv, "a:C:Lnsu:")) != -1) {
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switch (ch) {
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case 'a':
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login_style = optarg;
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break;
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case 'C':
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confpath = optarg;
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break;
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case 'L':
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i = open("/dev/tty", O_RDWR);
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if (i != -1)
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ioctl(i, TIOCCLRVERAUTH);
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exit(i == -1);
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case 'u':
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if (parseuid(optarg, &target) != 0)
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errx(1, "unknown user");
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break;
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case 'n':
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nflag = 1;
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break;
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case 's':
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sflag = 1;
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break;
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default:
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usage();
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break;
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}
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}
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argv += optind;
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argc -= optind;
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if (confpath) {
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if (sflag)
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usage();
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} else if ((!sflag && !argc) || (sflag && argc))
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usage();
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rv = getpwuid_r(uid, &mypwstore, mypwbuf, sizeof(mypwbuf), &mypw);
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if (rv != 0)
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err(1, "getpwuid_r failed");
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if (mypw == NULL)
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errx(1, "no passwd entry for self");
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ngroups = getgroups(NGROUPS_MAX, groups);
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if (ngroups == -1)
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err(1, "can't get groups");
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groups[ngroups++] = getgid();
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if (sflag) {
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sh = getenv("SHELL");
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if (sh == NULL || *sh == '\0') {
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shargv[0] = mypw->pw_shell;
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} else
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shargv[0] = sh;
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argv = shargv;
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argc = 1;
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}
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if (confpath) {
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if (pledge("stdio rpath getpw id", NULL) == -1)
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err(1, "pledge");
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checkconfig(confpath, argc, argv, uid, groups, ngroups,
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target);
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exit(1); /* fail safe */
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}
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if (geteuid())
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errx(1, "not installed setuid");
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parseconfig("/etc/doas.conf", 1);
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/* cmdline is used only for logging, no need to abort on truncate */
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(void)strlcpy(cmdline, argv[0], sizeof(cmdline));
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for (i = 1; i < argc; i++) {
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if (strlcat(cmdline, " ", sizeof(cmdline)) >= sizeof(cmdline))
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break;
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if (strlcat(cmdline, argv[i], sizeof(cmdline)) >= sizeof(cmdline))
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break;
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}
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cmd = argv[0];
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rv = permit(uid, groups, ngroups, &rule, target, cmd,
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(const char **)argv + 1);
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if (rv != 0) {
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syslog(LOG_AUTHPRIV | LOG_NOTICE,
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"command not permitted for %s: %s", mypw->pw_name, cmdline);
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errc(1, EPERM, NULL);
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}
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if (!(rule->options & NOPASS)) {
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if (nflag)
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errx(1, "Authentication required");
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authuser(mypw->pw_name, login_style, rule->options & PERSIST);
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}
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if ((p = getenv("PATH")) != NULL)
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formerpath = strdup(p);
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if (formerpath == NULL)
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formerpath = "";
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if (unveil(_PATH_LOGIN_CONF, "r") == -1)
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err(1, "unveil %s", _PATH_LOGIN_CONF);
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if (unveil(_PATH_LOGIN_CONF ".db", "r") == -1)
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err(1, "unveil %s.db", _PATH_LOGIN_CONF);
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if (unveil(_PATH_LOGIN_CONF_D, "r") == -1)
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err(1, "unveil %s", _PATH_LOGIN_CONF_D);
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if (rule->cmd) {
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if (setenv("PATH", safepath, 1) == -1)
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err(1, "failed to set PATH '%s'", safepath);
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}
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if (unveilcommands(getenv("PATH"), cmd) == 0)
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goto fail;
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if (pledge("stdio rpath getpw exec id", NULL) == -1)
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err(1, "pledge");
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rv = getpwuid_r(target, &targpwstore, targpwbuf, sizeof(targpwbuf), &targpw);
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if (rv != 0)
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err(1, "getpwuid_r failed");
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if (targpw == NULL)
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errx(1, "no passwd entry for target");
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if (setusercontext(NULL, targpw, target, LOGIN_SETGROUP |
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LOGIN_SETPATH |
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LOGIN_SETPRIORITY | LOGIN_SETRESOURCES | LOGIN_SETUMASK |
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LOGIN_SETUSER | LOGIN_SETENV | LOGIN_SETRTABLE) != 0)
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errx(1, "failed to set user context for target");
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if (pledge("stdio rpath exec", NULL) == -1)
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err(1, "pledge");
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if (getcwd(cwdpath, sizeof(cwdpath)) == NULL)
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cwd = "(failed)";
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else
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cwd = cwdpath;
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if (pledge("stdio exec", NULL) == -1)
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err(1, "pledge");
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if (!(rule->options & NOLOG)) {
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syslog(LOG_AUTHPRIV | LOG_INFO,
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"%s ran command %s as %s from %s",
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mypw->pw_name, cmdline, targpw->pw_name, cwd);
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}
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envp = prepenv(rule, mypw, targpw);
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/* setusercontext set path for the next process, so reset it for us */
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if (rule->cmd) {
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if (setenv("PATH", safepath, 1) == -1)
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err(1, "failed to set PATH '%s'", safepath);
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} else {
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if (setenv("PATH", formerpath, 1) == -1)
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err(1, "failed to set PATH '%s'", formerpath);
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}
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execvpe(cmd, argv, envp);
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fail:
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if (errno == ENOENT)
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errx(1, "%s: command not found", cmd);
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err(1, "%s", cmd);
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}
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