diff options
Diffstat (limited to 'usr.bin/doas/doas.c')
| -rw-r--r-- | usr.bin/doas/doas.c | 482 |
1 files changed, 482 insertions, 0 deletions
diff --git a/usr.bin/doas/doas.c b/usr.bin/doas/doas.c new file mode 100644 index 0000000..15220e4 --- /dev/null +++ b/usr.bin/doas/doas.c @@ -0,0 +1,482 @@ +/* $OpenBSD: doas.c,v 1.82 2019/10/18 17:15:45 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. + */ + +#ifndef _GNU_SOURCE +#define _GNU_SOURCE +#endif + +#include <sys/types.h> +#include <sys/stat.h> +#include <sys/ioctl.h> + +#include <limits.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 <fcntl.h> +#include <shadow.h> + +#include "doas.h" + +#ifndef UID_MAX +#define UID_MAX 65535 +#endif + +#ifndef GID_MAX +#define GID_MAX 65535 +#endif + +static void __dead +usage(void) +{ + fprintf(stderr, "usage: doas [-Lns] [-C config] [-u user]" + " command [args]\n"); + exit(1); +} + +static int +parseuid(const char *s, uid_t *uid) +{ + struct passwd *pw; + const char *errstr; + + if ((pw = getpwnam(s)) != NULL) { + *uid = pw->pw_uid; + if (*uid == UID_MAX) + return -1; + return 0; + } + *uid = strtonum(s, 0, UID_MAX - 1, &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; + if (*gid == GID_MAX) + return -1; + return 0; + } + *gid = strtonum(s, 0, GID_MAX - 1, &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, const 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); +} + +static void __dead +checkconfig(const char *confpath, int argc, char **argv, + uid_t uid, gid_t *groups, int ngroups, uid_t target) +{ + const 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); + } +} + +static int +verifypasswd(const char *user, const char *pass) +{ + struct spwd *sp; + char *p1, *p2; + + sp = getspnam(user); + if (!sp) + return 0; + p1 = sp->sp_pwdp; + if (p1[0] == '!' || p1[0] == '*') + return 0; + p2 = crypt(pass, p1); + if (!p2) + return 0; + return strcmp(p1, p2) == 0; +} + +static void +authuser(char *myname, int persist) +{ + char *challenge = NULL, *response, rbuf[1024], cbuf[128]; + int fd = -1, valid = 0; + + if (persist) { + fd = openpersist(&valid); + if (valid) + goto good; + } + + if (!challenge) { + char host[HOST_NAME_MAX + 1]; + if (gethostname(host, sizeof(host))) + snprintf(host, sizeof(host), "?"); + snprintf(cbuf, sizeof(cbuf), + "\rdoas (%.32s@%.32s) password: ", myname, host); + challenge = cbuf; + } + response = readpassphrase(challenge, rbuf, sizeof(rbuf), + RPP_REQUIRE_TTY); + if (response == NULL && errno == ENOTTY) { + syslog(LOG_NOTICE, "tty required for %s", myname); + errx(1, "a tty is required"); + } + if (!verifypasswd(myname, response)) { + explicit_bzero(rbuf, sizeof(rbuf)); + syslog(LOG_NOTICE, "failed auth for %s", myname); + errx(1, "Authorization failed"); + } + explicit_bzero(rbuf, sizeof(rbuf)); +good: + if (fd != -1) { + setpersist(fd); + close(fd); + } +} + +int +unveilcommands(const char *ipath, const char *cmd) +{ + char *path = NULL, *p; + int unveils = 0; + + if (strchr(cmd, '/') != NULL) { + if (unveil(cmd, "x") != -1) + unveils++; + goto done; + } + + if (!ipath) { + errno = ENOENT; + goto done; + } + path = strdup(ipath); + if (!path) { + errno = ENOENT; + goto done; + } + for (p = path; p && *p; ) { + char buf[PATH_MAX]; + char *cp = strsep(&p, ":"); + + if (cp) { + int r = snprintf(buf, sizeof buf, "%s/%s", cp, cmd); + if (r >= 0 && r < sizeof buf) { + if (unveil(buf, "x") != -1) + unveils++; + } + } + } +done: + free(path); + return (unveils); +} + +int +main(int argc, char **argv) +{ + const char *safepath = "/bin"; + const char *confpath = NULL; + char *shargv[] = { NULL, NULL }; + char *sh; + const char *p; + const char *cmd; + char cmdline[LINE_MAX]; + char mypwbuf[1024], targpwbuf[1024]; + struct passwd mypwstore, targpwstore; + struct passwd *mypw, *targpw; + const struct rule *rule; + uid_t uid; + uid_t target = 0; + gid_t groups[NGROUPS_MAX + 1]; + int ngroups; + int i, ch, rv; + int sflag = 0; + int nflag = 0; + char cwdpath[PATH_MAX]; + const char *cwd; + char **envp; + + setprogname("doas"); + openlog("doas", 0, LOG_AUTHPRIV); + + uid = getuid(); + + while ((ch = getopt(argc, argv, "C:Lnsu:")) != -1) { + switch (ch) { + case 'C': + confpath = optarg; + break; + case 'L': + exit(clearpersist() != 0); + 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(); + + rv = getpwuid_r(uid, &mypwstore, mypwbuf, sizeof(mypwbuf), &mypw); + if (rv != 0) + err(1, "getpwuid_r failed"); + if (mypw == NULL) + errx(1, "no passwd entry for self"); + 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] = mypw->pw_shell; + } else + shargv[0] = sh; + argv = shargv; + argc = 1; + } + + if (confpath) { + checkconfig(confpath, argc, argv, uid, groups, ngroups, + target); + exit(1); /* fail safe */ + } + + if (geteuid()) + errx(1, "not installed setuid"); + + 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_NOTICE, "failed command for %s: %s", mypw->pw_name, cmdline); + errno = EPERM; + err(1, NULL); + } + + if (!(rule->options & NOPASS)) { + if (nflag) + errx(1, "Authorization required"); + + authuser(mypw->pw_name, rule->options & PERSIST); + } + + if ((p = getenv("PATH")) != NULL) + formerpath = strdup(p); + if (formerpath == NULL) + formerpath = ""; + + if (unveil(_PATH_LOGIN_CONF, "r") == -1 || + unveil(_PATH_LOGIN_CONF ".db", "r") == -1) + err(1, "unveil"); + if (rule->cmd) { + if (setenv("PATH", safepath, 1) == -1) + err(1, "failed to set PATH '%s'", safepath); + } + if (unveilcommands(getenv("PATH"), cmd) == 0) + goto fail; + + if (pledge("stdio rpath getpw exec id", NULL) == -1) + err(1, "pledge"); + + rv = getpwuid_r(target, &targpwstore, targpwbuf, sizeof(targpwbuf), &targpw); + if (rv != 0) + err(1, "getpwuid_r failed"); + if (targpw == NULL) + errx(1, "no passwd entry for target"); + + if (initgroups(targpw->pw_name, targpw->pw_gid) < 0) + err(1, "initgroups"); + if (setgid(targpw->pw_gid) < 0) + err(1, "setgid"); + if (setuid(targpw->pw_uid) < 0) + err(1, "setuid"); + + 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_INFO, "%s ran command %s as %s from %s", + mypw->pw_name, cmdline, targpw->pw_name, cwd); + + envp = prepenv(rule, mypw, targpw); + + /* setusercontext set path for the next process, so reset it for us */ + if (rule->cmd) { + if (setenv("PATH", safepath, 1) == -1) + err(1, "failed to set PATH '%s'", safepath); + } else { + if (setenv("PATH", formerpath, 1) == -1) + err(1, "failed to set PATH '%s'", formerpath); + } + execvpe(cmd, argv, envp); +fail: + if (errno == ENOENT) + errx(1, "%s: command not found", cmd); + err(1, "%s", cmd); +} |