doas

https://man.openbsd.org/doas.1
git clone anongit@rnpnr.xyz:doas.git
Log | Files | Refs | Feed

Commit: 179d313d0e7a88486949edce106835e94daf2000
Parent: 7b14b4ce2394732cec6e88e9368b9c0768f1cbc9
Author: Michael Forney
Date:   Sun, 26 Feb 2017 16:50:55 -0800

doas: Port to linux/musl

Remove -a login style option and BSD authentication. Instead, compare
against shadow file.

Use timestamp files in /run/doas instead of TIOC*VERAUTH to implement
persist.

Use initgroups/setgid/setuid instead of setusercontext.

Provide UID_MAX and GID_MAX defaults.

Use LOGIN_NAME_MAX instead of _PW_NAME_LEN.

Remove call to closefrom.

Replace calls to errc with err after setting errno.

Call openlog at start to set syslog identity.

Diffstat:
Mdoas.1 | 9---------
Mdoas.c | 97+++++++++++++++++++++++++++++++++++++++++++------------------------------------
Mdoas.h | 4++++
Mparse.y | 1+
Apersist.c | 133+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
5 files changed, 191 insertions(+), 53 deletions(-)

diff --git a/doas.1 b/doas.1 @@ -22,7 +22,6 @@ .Sh SYNOPSIS .Nm doas .Op Fl Lns -.Op Fl a Ar style .Op Fl C Ar config .Op Fl u Ar user .Ar command @@ -67,14 +66,6 @@ The working directory is not changed. .Pp The options are as follows: .Bl -tag -width tenletters -.It Fl a Ar style -Use the specified authentication style when validating the user, -as allowed by -.Pa /etc/login.conf . -A list of doas-specific authentication methods may be configured by adding an -.Sq auth-doas -entry in -.Xr login.conf 5 . .It Fl C Ar config Parse and check the configuration file .Ar config , diff --git a/doas.c b/doas.c @@ -20,8 +20,6 @@ #include <sys/ioctl.h> #include <limits.h> -#include <login_cap.h> -#include <bsd_auth.h> #include <readpassphrase.h> #include <string.h> #include <stdio.h> @@ -33,13 +31,22 @@ #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] [-a style] [-C config] [-u user]" + fprintf(stderr, "usage: doas [-Lns] [-C config] [-u user]" " command [args]\n"); exit(1); } @@ -193,23 +200,36 @@ checkconfig(const char *confpath, int argc, char **argv, } } +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, char *login_style, int persist) +authuser(char *myname, int persist) { char *challenge = NULL, *response, rbuf[1024], cbuf[128]; - auth_session_t *as; - int fd = -1; + int fd = -1, valid = 0; - if (persist) - fd = open("/dev/tty", O_RDWR); - if (fd != -1) { - if (ioctl(fd, TIOCCHKVERAUTH) == 0) + if (persist) { + fd = openpersist(&valid); + if (valid) goto good; } - if (!(as = auth_userchallenge(myname, login_style, "auth-doas", - &challenge))) - errx(1, "Authorization failed"); if (!challenge) { char host[HOST_NAME_MAX + 1]; if (gethostname(host, sizeof(host))) @@ -221,21 +241,18 @@ authuser(char *myname, char *login_style, int persist) response = readpassphrase(challenge, rbuf, sizeof(rbuf), RPP_REQUIRE_TTY); if (response == NULL && errno == ENOTTY) { - syslog(LOG_AUTHPRIV | LOG_NOTICE, - "tty required for %s", myname); + syslog(LOG_NOTICE, "tty required for %s", myname); errx(1, "a tty is required"); } - if (!auth_userresponse(as, response, 0)) { + if (!verifypasswd(myname, response)) { explicit_bzero(rbuf, sizeof(rbuf)); - syslog(LOG_AUTHPRIV | LOG_NOTICE, - "failed auth for %s", myname); + syslog(LOG_NOTICE, "failed auth for %s", myname); errx(1, "Authorization failed"); } explicit_bzero(rbuf, sizeof(rbuf)); good: if (fd != -1) { - int secs = 5 * 60; - ioctl(fd, TIOCSETVERAUTH, &secs); + setpersist(fd); close(fd); } } @@ -281,15 +298,14 @@ done: int main(int argc, char **argv) { - const char *safepath = "/bin:/sbin:/usr/bin:/usr/sbin:" - "/usr/local/bin:/usr/local/sbin"; + 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[_PW_BUF_LEN], targpwbuf[_PW_BUF_LEN]; + char mypwbuf[1024], targpwbuf[1024]; struct passwd mypwstore, targpwstore; struct passwd *mypw, *targpw; const struct rule *rule; @@ -302,28 +318,20 @@ main(int argc, char **argv) int nflag = 0; char cwdpath[PATH_MAX]; const char *cwd; - char *login_style = NULL; char **envp; setprogname("doas"); - - closefrom(STDERR_FILENO + 1); + openlog("doas", 0, LOG_AUTHPRIV); uid = getuid(); - while ((ch = getopt(argc, argv, "a:C:Lnsu:")) != -1) { + while ((ch = getopt(argc, argv, "C:Lnsu:")) != -1) { switch (ch) { - case 'a': - login_style = optarg; - break; case 'C': confpath = optarg; break; case 'L': - i = open("/dev/tty", O_RDWR); - if (i != -1) - ioctl(i, TIOCCLRVERAUTH); - exit(i == -1); + exit(clearpersist() != 0); case 'u': if (parseuid(optarg, &target) != 0) errx(1, "unknown user"); @@ -391,16 +399,16 @@ main(int argc, char **argv) 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", mypw->pw_name, cmdline); - errc(1, EPERM, NULL); + 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, login_style, rule->options & PERSIST); + authuser(mypw->pw_name, rule->options & PERSIST); } if ((p = getenv("PATH")) != NULL) @@ -427,11 +435,12 @@ main(int argc, char **argv) if (targpw == NULL) errx(1, "no passwd entry for target"); - if (setusercontext(NULL, targpw, target, LOGIN_SETGROUP | - LOGIN_SETPATH | - LOGIN_SETPRIORITY | LOGIN_SETRESOURCES | LOGIN_SETUMASK | - LOGIN_SETUSER) != 0) - errx(1, "failed to set user context 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"); @@ -444,7 +453,7 @@ main(int argc, char **argv) if (pledge("stdio exec", NULL) == -1) err(1, "pledge"); - syslog(LOG_AUTHPRIV | LOG_INFO, "%s ran command %s as %s from %s", + syslog(LOG_INFO, "%s ran command %s as %s from %s", mypw->pw_name, cmdline, targpw->pw_name, cwd); envp = prepenv(rule, mypw, targpw); diff --git a/doas.h b/doas.h @@ -36,6 +36,10 @@ struct passwd; char **prepenv(const struct rule *, const struct passwd *, const struct passwd *); +int openpersist(int *valid); +int setpersist(int fd); +int clearpersist(void); + #define PERMIT 1 #define DENY 2 diff --git a/parse.y b/parse.y @@ -19,6 +19,7 @@ #include <sys/types.h> #include <ctype.h> #include <unistd.h> +#include <stdlib.h> #include <stdint.h> #include <stdarg.h> #include <stdio.h> diff --git a/persist.c b/persist.c @@ -0,0 +1,133 @@ +#include <errno.h> +#include <fcntl.h> +#include <limits.h> +#include <stdio.h> +#include <stdlib.h> +#include <string.h> +#include <sys/stat.h> +#include <sys/types.h> +#include <time.h> +#include <unistd.h> + +#include "doas.h" + +#define PERSIST_DIR "/run/doas" +#define PERSIST_TIMEOUT 5 * 60 + +static int +ttyid(dev_t *tty) +{ + int fd, i; + char buf[BUFSIZ], *p; + ssize_t n; + + fd = open("/proc/self/stat", O_RDONLY); + if (fd == -1) + return -1; + n = read(fd, buf, sizeof(buf) - 1); + if (n >= 0) + buf[n] = '\0'; + /* check that we read the whole file */ + n = read(fd, buf, 1); + close(fd); + if (n != 0) + return -1; + p = strrchr(buf, ')'); + if (!p) + return -1; + ++p; + /* ttr_nr is the 5th field after executable name, so skip the next 4 */ + for (i = 0; i < 4; ++i) { + p = strchr(++p, ' '); + if (!p) + return -1; + } + *tty = strtol(p, &p, 10); + if (*p != ' ') + return -1; + return 0; +} + +static int +persistpath(char *buf, size_t len) +{ + dev_t tty; + int n; + + if (ttyid(&tty) < 0) + return -1; + n = snprintf(buf, len, PERSIST_DIR "/%ju-%ju", (uintmax_t)getuid(), (uintmax_t)tty); + if (n < 0 || n >= (int)len) + return -1; + return 0; +} + +int +openpersist(int *valid) +{ + char path[256]; + struct stat st; + struct timespec ts; + int fd; + + if (stat(PERSIST_DIR, &st) < 0) { + if (errno != ENOENT) + return -1; + if (mkdir(PERSIST_DIR, 0700) < 0) + return -1; + } else if (st.st_uid != 0 || st.st_mode != (S_IFDIR | 0700)) { + return -1; + } + if (persistpath(path, sizeof(path)) < 0) + return -1; + fd = open(path, O_RDONLY); + if (fd == -1) { + char tmp[256]; + struct timespec ts[2] = { { .tv_nsec = UTIME_OMIT }, { 0 } }; + int n; + + n = snprintf(tmp, sizeof(tmp), PERSIST_DIR "/.tmp-%d", getpid()); + if (n < 0 || n >= (int)sizeof(tmp)) + return -1; + fd = open(tmp, O_RDONLY | O_CREAT | O_EXCL, 0); + if (fd == -1) + return -1; + if (futimens(fd, ts) < 0 || rename(tmp, path) < 0) { + close(fd); + unlink(tmp); + return -1; + } + *valid = 0; + } else { + *valid = clock_gettime(CLOCK_BOOTTIME, &ts) == 0 && + fstat(fd, &st) == 0 && + (ts.tv_sec < st.st_mtim.tv_sec || + ts.tv_sec == st.st_mtim.tv_sec && ts.tv_nsec < st.st_mtim.tv_nsec) && + st.st_mtime - ts.tv_sec <= PERSIST_TIMEOUT; + } + return fd; +} + +int +setpersist(int fd) +{ + struct timespec times[2]; + + if (clock_gettime(CLOCK_BOOTTIME, &times[1]) < 0) + return -1; + times[0].tv_nsec = UTIME_OMIT; + times[1].tv_sec += PERSIST_TIMEOUT; + return futimens(fd, times); +} + +int +clearpersist(void) +{ + char path[256]; + + if (persistpath(path, sizeof(path)) < 0) + return -1; + if (unlink(path) < 0 && errno != ENOENT) + return -1; + return 0; +}