upstream commit
move subprocess() so scp/sftp do not need uidswap.o; ok djm@ OpenBSD-Commit-ID: 6601b8360388542c2e5fef0f4085f8e54750bea8
This commit is contained in:
markus@openbsd.org
Damien Miller
parent
b0d34132b3
commit
25cf9105b8
155
auth.c
155
auth.c
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@ -1,4 +1,4 @@
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/* $OpenBSD: auth.c,v 1.124 2017/09/12 06:32:07 djm Exp $ */
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/* $OpenBSD: auth.c,v 1.125 2018/01/08 15:21:49 markus Exp $ */
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/*
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* Copyright (c) 2000 Markus Friedl. All rights reserved.
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*
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@ -28,6 +28,7 @@
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#include <sys/types.h>
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#include <sys/stat.h>
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#include <sys/socket.h>
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#include <sys/wait.h>
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#include <netinet/in.h>
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@ -840,3 +841,155 @@ auth_get_canonical_hostname(struct ssh *ssh, int use_dns)
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return dnsname;
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}
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}
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/*
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* Runs command in a subprocess wuth a minimal environment.
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* Returns pid on success, 0 on failure.
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* The child stdout and stderr maybe captured, left attached or sent to
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* /dev/null depending on the contents of flags.
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* "tag" is prepended to log messages.
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* NB. "command" is only used for logging; the actual command executed is
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* av[0].
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*/
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pid_t
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subprocess(const char *tag, struct passwd *pw, const char *command,
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int ac, char **av, FILE **child, u_int flags)
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{
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FILE *f = NULL;
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struct stat st;
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int fd, devnull, p[2], i;
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pid_t pid;
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char *cp, errmsg[512];
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u_int envsize;
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char **child_env;
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if (child != NULL)
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*child = NULL;
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debug3("%s: %s command \"%s\" running as %s (flags 0x%x)", __func__,
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tag, command, pw->pw_name, flags);
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/* Check consistency */
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if ((flags & SSH_SUBPROCESS_STDOUT_DISCARD) != 0 &&
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(flags & SSH_SUBPROCESS_STDOUT_CAPTURE) != 0) {
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error("%s: inconsistent flags", __func__);
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return 0;
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}
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if (((flags & SSH_SUBPROCESS_STDOUT_CAPTURE) == 0) != (child == NULL)) {
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error("%s: inconsistent flags/output", __func__);
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return 0;
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}
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/*
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* If executing an explicit binary, then verify the it exists
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* and appears safe-ish to execute
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*/
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if (*av[0] != '/') {
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error("%s path is not absolute", tag);
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return 0;
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}
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temporarily_use_uid(pw);
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if (stat(av[0], &st) < 0) {
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error("Could not stat %s \"%s\": %s", tag,
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av[0], strerror(errno));
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restore_uid();
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return 0;
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}
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if (safe_path(av[0], &st, NULL, 0, errmsg, sizeof(errmsg)) != 0) {
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error("Unsafe %s \"%s\": %s", tag, av[0], errmsg);
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restore_uid();
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return 0;
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}
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/* Prepare to keep the child's stdout if requested */
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if (pipe(p) != 0) {
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error("%s: pipe: %s", tag, strerror(errno));
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restore_uid();
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return 0;
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}
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restore_uid();
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switch ((pid = fork())) {
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case -1: /* error */
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error("%s: fork: %s", tag, strerror(errno));
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close(p[0]);
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close(p[1]);
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return 0;
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case 0: /* child */
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/* Prepare a minimal environment for the child. */
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envsize = 5;
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child_env = xcalloc(sizeof(*child_env), envsize);
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child_set_env(&child_env, &envsize, "PATH", _PATH_STDPATH);
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child_set_env(&child_env, &envsize, "USER", pw->pw_name);
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child_set_env(&child_env, &envsize, "LOGNAME", pw->pw_name);
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child_set_env(&child_env, &envsize, "HOME", pw->pw_dir);
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if ((cp = getenv("LANG")) != NULL)
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child_set_env(&child_env, &envsize, "LANG", cp);
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for (i = 0; i < NSIG; i++)
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signal(i, SIG_DFL);
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if ((devnull = open(_PATH_DEVNULL, O_RDWR)) == -1) {
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error("%s: open %s: %s", tag, _PATH_DEVNULL,
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strerror(errno));
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_exit(1);
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}
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if (dup2(devnull, STDIN_FILENO) == -1) {
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error("%s: dup2: %s", tag, strerror(errno));
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_exit(1);
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}
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/* Set up stdout as requested; leave stderr in place for now. */
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fd = -1;
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if ((flags & SSH_SUBPROCESS_STDOUT_CAPTURE) != 0)
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fd = p[1];
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else if ((flags & SSH_SUBPROCESS_STDOUT_DISCARD) != 0)
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fd = devnull;
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if (fd != -1 && dup2(fd, STDOUT_FILENO) == -1) {
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error("%s: dup2: %s", tag, strerror(errno));
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_exit(1);
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}
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closefrom(STDERR_FILENO + 1);
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/* Don't use permanently_set_uid() here to avoid fatal() */
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if (setresgid(pw->pw_gid, pw->pw_gid, pw->pw_gid) != 0) {
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error("%s: setresgid %u: %s", tag, (u_int)pw->pw_gid,
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strerror(errno));
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_exit(1);
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}
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if (setresuid(pw->pw_uid, pw->pw_uid, pw->pw_uid) != 0) {
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error("%s: setresuid %u: %s", tag, (u_int)pw->pw_uid,
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strerror(errno));
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_exit(1);
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}
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/* stdin is pointed to /dev/null at this point */
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if ((flags & SSH_SUBPROCESS_STDOUT_DISCARD) != 0 &&
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dup2(STDIN_FILENO, STDERR_FILENO) == -1) {
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error("%s: dup2: %s", tag, strerror(errno));
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_exit(1);
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}
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execve(av[0], av, child_env);
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error("%s exec \"%s\": %s", tag, command, strerror(errno));
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_exit(127);
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default: /* parent */
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break;
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}
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close(p[1]);
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if ((flags & SSH_SUBPROCESS_STDOUT_CAPTURE) == 0)
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close(p[0]);
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else if ((f = fdopen(p[0], "r")) == NULL) {
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error("%s: fdopen: %s", tag, strerror(errno));
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close(p[0]);
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/* Don't leave zombie child */
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kill(pid, SIGTERM);
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while (waitpid(pid, NULL, 0) == -1 && errno == EINTR)
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;
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return 0;
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}
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/* Success */
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debug3("%s: %s pid %ld", __func__, tag, (long)pid);
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if (child != NULL)
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*child = f;
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return pid;
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}
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8
auth.h
8
auth.h
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@ -1,4 +1,4 @@
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/* $OpenBSD: auth.h,v 1.93 2017/08/18 05:36:45 djm Exp $ */
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/* $OpenBSD: auth.h,v 1.94 2018/01/08 15:21:49 markus Exp $ */
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/*
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* Copyright (c) 2000 Markus Friedl. All rights reserved.
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@ -221,6 +221,12 @@ void auth_debug_reset(void);
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struct passwd *fakepw(void);
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#define SSH_SUBPROCESS_STDOUT_DISCARD (1) /* Discard stdout */
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#define SSH_SUBPROCESS_STDOUT_CAPTURE (1<<1) /* Redirect stdout */
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#define SSH_SUBPROCESS_STDERR_DISCARD (1<<2) /* Discard stderr */
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pid_t subprocess(const char *, struct passwd *,
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const char *, int, char **, FILE **, u_int flags);
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int sys_auth_passwd(Authctxt *, const char *);
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#define SKEY_PROMPT "\nS/Key Password: "
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154
misc.c
154
misc.c
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@ -1,4 +1,4 @@
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/* $OpenBSD: misc.c,v 1.122 2017/12/08 02:14:33 djm Exp $ */
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/* $OpenBSD: misc.c,v 1.123 2018/01/08 15:21:49 markus Exp $ */
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/*
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* Copyright (c) 2000 Markus Friedl. All rights reserved.
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* Copyright (c) 2005,2006 Damien Miller. All rights reserved.
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@ -1740,158 +1740,6 @@ argv_assemble(int argc, char **argv)
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return ret;
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}
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/*
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* Runs command in a subprocess wuth a minimal environment.
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* Returns pid on success, 0 on failure.
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* The child stdout and stderr maybe captured, left attached or sent to
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* /dev/null depending on the contents of flags.
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* "tag" is prepended to log messages.
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* NB. "command" is only used for logging; the actual command executed is
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* av[0].
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*/
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pid_t
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subprocess(const char *tag, struct passwd *pw, const char *command,
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int ac, char **av, FILE **child, u_int flags)
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{
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FILE *f = NULL;
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struct stat st;
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int fd, devnull, p[2], i;
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pid_t pid;
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char *cp, errmsg[512];
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u_int envsize;
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char **child_env;
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if (child != NULL)
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*child = NULL;
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debug3("%s: %s command \"%s\" running as %s (flags 0x%x)", __func__,
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tag, command, pw->pw_name, flags);
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/* Check consistency */
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if ((flags & SSH_SUBPROCESS_STDOUT_DISCARD) != 0 &&
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(flags & SSH_SUBPROCESS_STDOUT_CAPTURE) != 0) {
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error("%s: inconsistent flags", __func__);
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return 0;
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}
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if (((flags & SSH_SUBPROCESS_STDOUT_CAPTURE) == 0) != (child == NULL)) {
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error("%s: inconsistent flags/output", __func__);
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return 0;
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}
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/*
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* If executing an explicit binary, then verify the it exists
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* and appears safe-ish to execute
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*/
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if (*av[0] != '/') {
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error("%s path is not absolute", tag);
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return 0;
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}
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temporarily_use_uid(pw);
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if (stat(av[0], &st) < 0) {
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error("Could not stat %s \"%s\": %s", tag,
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av[0], strerror(errno));
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restore_uid();
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return 0;
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}
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if (safe_path(av[0], &st, NULL, 0, errmsg, sizeof(errmsg)) != 0) {
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error("Unsafe %s \"%s\": %s", tag, av[0], errmsg);
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restore_uid();
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return 0;
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}
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/* Prepare to keep the child's stdout if requested */
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if (pipe(p) != 0) {
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error("%s: pipe: %s", tag, strerror(errno));
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restore_uid();
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return 0;
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}
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restore_uid();
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switch ((pid = fork())) {
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case -1: /* error */
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error("%s: fork: %s", tag, strerror(errno));
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close(p[0]);
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close(p[1]);
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return 0;
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case 0: /* child */
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/* Prepare a minimal environment for the child. */
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envsize = 5;
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child_env = xcalloc(sizeof(*child_env), envsize);
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child_set_env(&child_env, &envsize, "PATH", _PATH_STDPATH);
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child_set_env(&child_env, &envsize, "USER", pw->pw_name);
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child_set_env(&child_env, &envsize, "LOGNAME", pw->pw_name);
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child_set_env(&child_env, &envsize, "HOME", pw->pw_dir);
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if ((cp = getenv("LANG")) != NULL)
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child_set_env(&child_env, &envsize, "LANG", cp);
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for (i = 0; i < NSIG; i++)
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signal(i, SIG_DFL);
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if ((devnull = open(_PATH_DEVNULL, O_RDWR)) == -1) {
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error("%s: open %s: %s", tag, _PATH_DEVNULL,
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strerror(errno));
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_exit(1);
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}
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if (dup2(devnull, STDIN_FILENO) == -1) {
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error("%s: dup2: %s", tag, strerror(errno));
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_exit(1);
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}
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/* Set up stdout as requested; leave stderr in place for now. */
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fd = -1;
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if ((flags & SSH_SUBPROCESS_STDOUT_CAPTURE) != 0)
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fd = p[1];
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else if ((flags & SSH_SUBPROCESS_STDOUT_DISCARD) != 0)
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fd = devnull;
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if (fd != -1 && dup2(fd, STDOUT_FILENO) == -1) {
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error("%s: dup2: %s", tag, strerror(errno));
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_exit(1);
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}
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closefrom(STDERR_FILENO + 1);
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/* Don't use permanently_set_uid() here to avoid fatal() */
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if (setresgid(pw->pw_gid, pw->pw_gid, pw->pw_gid) != 0) {
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error("%s: setresgid %u: %s", tag, (u_int)pw->pw_gid,
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strerror(errno));
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_exit(1);
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}
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if (setresuid(pw->pw_uid, pw->pw_uid, pw->pw_uid) != 0) {
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error("%s: setresuid %u: %s", tag, (u_int)pw->pw_uid,
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strerror(errno));
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_exit(1);
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}
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/* stdin is pointed to /dev/null at this point */
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if ((flags & SSH_SUBPROCESS_STDOUT_DISCARD) != 0 &&
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dup2(STDIN_FILENO, STDERR_FILENO) == -1) {
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error("%s: dup2: %s", tag, strerror(errno));
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_exit(1);
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}
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execve(av[0], av, child_env);
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error("%s exec \"%s\": %s", tag, command, strerror(errno));
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_exit(127);
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default: /* parent */
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break;
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}
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close(p[1]);
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if ((flags & SSH_SUBPROCESS_STDOUT_CAPTURE) == 0)
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close(p[0]);
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else if ((f = fdopen(p[0], "r")) == NULL) {
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error("%s: fdopen: %s", tag, strerror(errno));
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close(p[0]);
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/* Don't leave zombie child */
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kill(pid, SIGTERM);
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while (waitpid(pid, NULL, 0) == -1 && errno == EINTR)
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;
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return 0;
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}
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/* Success */
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debug3("%s: %s pid %ld", __func__, tag, (long)pid);
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if (child != NULL)
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*child = f;
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return pid;
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}
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/* Returns 0 if pid exited cleanly, non-zero otherwise */
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int
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exited_cleanly(pid_t pid, const char *tag, const char *cmd, int quiet)
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8
misc.h
8
misc.h
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@ -1,4 +1,4 @@
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/* $OpenBSD: misc.h,v 1.69 2017/12/05 23:59:47 dtucker Exp $ */
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/* $OpenBSD: misc.h,v 1.70 2018/01/08 15:21:49 markus Exp $ */
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/*
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* Author: Tatu Ylonen <ylo@cs.hut.fi>
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@ -149,12 +149,6 @@ int argv_split(const char *, int *, char ***);
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char *argv_assemble(int, char **argv);
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int exited_cleanly(pid_t, const char *, const char *, int);
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#define SSH_SUBPROCESS_STDOUT_DISCARD (1) /* Discard stdout */
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#define SSH_SUBPROCESS_STDOUT_CAPTURE (1<<1) /* Redirect stdout */
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#define SSH_SUBPROCESS_STDERR_DISCARD (1<<2) /* Discard stderr */
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pid_t subprocess(const char *, struct passwd *,
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const char *, int, char **, FILE **, u_int flags);
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struct stat;
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int safe_path(const char *, struct stat *, const char *, uid_t,
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char *, size_t);
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