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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 2018-01-08 15:21:49 +00:00 committed by Damien Miller
parent b0d34132b3
commit 25cf9105b8
4 changed files with 163 additions and 162 deletions
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155
auth.c
View File

@ -1,4 +1,4 @@
/* $OpenBSD: auth.c,v 1.124 2017/09/12 06:32:07 djm Exp $ */ /* $OpenBSD: auth.c,v 1.125 2018/01/08 15:21:49 markus Exp $ */
/* /*
* Copyright (c) 2000 Markus Friedl. All rights reserved. * Copyright (c) 2000 Markus Friedl. All rights reserved.
* *
@ -28,6 +28,7 @@
#include <sys/types.h> #include <sys/types.h>
#include <sys/stat.h> #include <sys/stat.h>
#include <sys/socket.h> #include <sys/socket.h>
#include <sys/wait.h>
#include <netinet/in.h> #include <netinet/in.h>
@ -840,3 +841,155 @@ auth_get_canonical_hostname(struct ssh *ssh, int use_dns)
return dnsname; return dnsname;
} }
} }
/*
* Runs command in a subprocess wuth a minimal environment.
* Returns pid on success, 0 on failure.
* The child stdout and stderr maybe captured, left attached or sent to
* /dev/null depending on the contents of flags.
* "tag" is prepended to log messages.
* NB. "command" is only used for logging; the actual command executed is
* av[0].
*/
pid_t
subprocess(const char *tag, struct passwd *pw, const char *command,
int ac, char **av, FILE **child, u_int flags)
{
FILE *f = NULL;
struct stat st;
int fd, devnull, p[2], i;
pid_t pid;
char *cp, errmsg[512];
u_int envsize;
char **child_env;
if (child != NULL)
*child = NULL;
debug3("%s: %s command \"%s\" running as %s (flags 0x%x)", __func__,
tag, command, pw->pw_name, flags);
/* Check consistency */
if ((flags & SSH_SUBPROCESS_STDOUT_DISCARD) != 0 &&
(flags & SSH_SUBPROCESS_STDOUT_CAPTURE) != 0) {
error("%s: inconsistent flags", __func__);
return 0;
}
if (((flags & SSH_SUBPROCESS_STDOUT_CAPTURE) == 0) != (child == NULL)) {
error("%s: inconsistent flags/output", __func__);
return 0;
}
/*
* If executing an explicit binary, then verify the it exists
* and appears safe-ish to execute
*/
if (*av[0] != '/') {
error("%s path is not absolute", tag);
return 0;
}
temporarily_use_uid(pw);
if (stat(av[0], &st) < 0) {
error("Could not stat %s \"%s\": %s", tag,
av[0], strerror(errno));
restore_uid();
return 0;
}
if (safe_path(av[0], &st, NULL, 0, errmsg, sizeof(errmsg)) != 0) {
error("Unsafe %s \"%s\": %s", tag, av[0], errmsg);
restore_uid();
return 0;
}
/* Prepare to keep the child's stdout if requested */
if (pipe(p) != 0) {
error("%s: pipe: %s", tag, strerror(errno));
restore_uid();
return 0;
}
restore_uid();
switch ((pid = fork())) {
case -1: /* error */
error("%s: fork: %s", tag, strerror(errno));
close(p[0]);
close(p[1]);
return 0;
case 0: /* child */
/* Prepare a minimal environment for the child. */
envsize = 5;
child_env = xcalloc(sizeof(*child_env), envsize);
child_set_env(&child_env, &envsize, "PATH", _PATH_STDPATH);
child_set_env(&child_env, &envsize, "USER", pw->pw_name);
child_set_env(&child_env, &envsize, "LOGNAME", pw->pw_name);
child_set_env(&child_env, &envsize, "HOME", pw->pw_dir);
if ((cp = getenv("LANG")) != NULL)
child_set_env(&child_env, &envsize, "LANG", cp);
for (i = 0; i < NSIG; i++)
signal(i, SIG_DFL);
if ((devnull = open(_PATH_DEVNULL, O_RDWR)) == -1) {
error("%s: open %s: %s", tag, _PATH_DEVNULL,
strerror(errno));
_exit(1);
}
if (dup2(devnull, STDIN_FILENO) == -1) {
error("%s: dup2: %s", tag, strerror(errno));
_exit(1);
}
/* Set up stdout as requested; leave stderr in place for now. */
fd = -1;
if ((flags & SSH_SUBPROCESS_STDOUT_CAPTURE) != 0)
fd = p[1];
else if ((flags & SSH_SUBPROCESS_STDOUT_DISCARD) != 0)
fd = devnull;
if (fd != -1 && dup2(fd, STDOUT_FILENO) == -1) {
error("%s: dup2: %s", tag, strerror(errno));
_exit(1);
}
closefrom(STDERR_FILENO + 1);
/* Don't use permanently_set_uid() here to avoid fatal() */
if (setresgid(pw->pw_gid, pw->pw_gid, pw->pw_gid) != 0) {
error("%s: setresgid %u: %s", tag, (u_int)pw->pw_gid,
strerror(errno));
_exit(1);
}
if (setresuid(pw->pw_uid, pw->pw_uid, pw->pw_uid) != 0) {
error("%s: setresuid %u: %s", tag, (u_int)pw->pw_uid,
strerror(errno));
_exit(1);
}
/* stdin is pointed to /dev/null at this point */
if ((flags & SSH_SUBPROCESS_STDOUT_DISCARD) != 0 &&
dup2(STDIN_FILENO, STDERR_FILENO) == -1) {
error("%s: dup2: %s", tag, strerror(errno));
_exit(1);
}
execve(av[0], av, child_env);
error("%s exec \"%s\": %s", tag, command, strerror(errno));
_exit(127);
default: /* parent */
break;
}
close(p[1]);
if ((flags & SSH_SUBPROCESS_STDOUT_CAPTURE) == 0)
close(p[0]);
else if ((f = fdopen(p[0], "r")) == NULL) {
error("%s: fdopen: %s", tag, strerror(errno));
close(p[0]);
/* Don't leave zombie child */
kill(pid, SIGTERM);
while (waitpid(pid, NULL, 0) == -1 && errno == EINTR)
;
return 0;
}
/* Success */
debug3("%s: %s pid %ld", __func__, tag, (long)pid);
if (child != NULL)
*child = f;
return pid;
}

8
auth.h
View File

@ -1,4 +1,4 @@
/* $OpenBSD: auth.h,v 1.93 2017/08/18 05:36:45 djm Exp $ */ /* $OpenBSD: auth.h,v 1.94 2018/01/08 15:21:49 markus Exp $ */
/* /*
* Copyright (c) 2000 Markus Friedl. All rights reserved. * Copyright (c) 2000 Markus Friedl. All rights reserved.
@ -221,6 +221,12 @@ void auth_debug_reset(void);
struct passwd *fakepw(void); struct passwd *fakepw(void);
#define SSH_SUBPROCESS_STDOUT_DISCARD (1) /* Discard stdout */
#define SSH_SUBPROCESS_STDOUT_CAPTURE (1<<1) /* Redirect stdout */
#define SSH_SUBPROCESS_STDERR_DISCARD (1<<2) /* Discard stderr */
pid_t subprocess(const char *, struct passwd *,
const char *, int, char **, FILE **, u_int flags);
int sys_auth_passwd(Authctxt *, const char *); int sys_auth_passwd(Authctxt *, const char *);
#define SKEY_PROMPT "\nS/Key Password: " #define SKEY_PROMPT "\nS/Key Password: "

154
misc.c
View File

@ -1,4 +1,4 @@
/* $OpenBSD: misc.c,v 1.122 2017/12/08 02:14:33 djm Exp $ */ /* $OpenBSD: misc.c,v 1.123 2018/01/08 15:21:49 markus Exp $ */
/* /*
* Copyright (c) 2000 Markus Friedl. All rights reserved. * Copyright (c) 2000 Markus Friedl. All rights reserved.
* Copyright (c) 2005,2006 Damien Miller. All rights reserved. * Copyright (c) 2005,2006 Damien Miller. All rights reserved.
@ -1740,158 +1740,6 @@ argv_assemble(int argc, char **argv)
return ret; return ret;
} }
/*
* Runs command in a subprocess wuth a minimal environment.
* Returns pid on success, 0 on failure.
* The child stdout and stderr maybe captured, left attached or sent to
* /dev/null depending on the contents of flags.
* "tag" is prepended to log messages.
* NB. "command" is only used for logging; the actual command executed is
* av[0].
*/
pid_t
subprocess(const char *tag, struct passwd *pw, const char *command,
int ac, char **av, FILE **child, u_int flags)
{
FILE *f = NULL;
struct stat st;
int fd, devnull, p[2], i;
pid_t pid;
char *cp, errmsg[512];
u_int envsize;
char **child_env;
if (child != NULL)
*child = NULL;
debug3("%s: %s command \"%s\" running as %s (flags 0x%x)", __func__,
tag, command, pw->pw_name, flags);
/* Check consistency */
if ((flags & SSH_SUBPROCESS_STDOUT_DISCARD) != 0 &&
(flags & SSH_SUBPROCESS_STDOUT_CAPTURE) != 0) {
error("%s: inconsistent flags", __func__);
return 0;
}
if (((flags & SSH_SUBPROCESS_STDOUT_CAPTURE) == 0) != (child == NULL)) {
error("%s: inconsistent flags/output", __func__);
return 0;
}
/*
* If executing an explicit binary, then verify the it exists
* and appears safe-ish to execute
*/
if (*av[0] != '/') {
error("%s path is not absolute", tag);
return 0;
}
temporarily_use_uid(pw);
if (stat(av[0], &st) < 0) {
error("Could not stat %s \"%s\": %s", tag,
av[0], strerror(errno));
restore_uid();
return 0;
}
if (safe_path(av[0], &st, NULL, 0, errmsg, sizeof(errmsg)) != 0) {
error("Unsafe %s \"%s\": %s", tag, av[0], errmsg);
restore_uid();
return 0;
}
/* Prepare to keep the child's stdout if requested */
if (pipe(p) != 0) {
error("%s: pipe: %s", tag, strerror(errno));
restore_uid();
return 0;
}
restore_uid();
switch ((pid = fork())) {
case -1: /* error */
error("%s: fork: %s", tag, strerror(errno));
close(p[0]);
close(p[1]);
return 0;
case 0: /* child */
/* Prepare a minimal environment for the child. */
envsize = 5;
child_env = xcalloc(sizeof(*child_env), envsize);
child_set_env(&child_env, &envsize, "PATH", _PATH_STDPATH);
child_set_env(&child_env, &envsize, "USER", pw->pw_name);
child_set_env(&child_env, &envsize, "LOGNAME", pw->pw_name);
child_set_env(&child_env, &envsize, "HOME", pw->pw_dir);
if ((cp = getenv("LANG")) != NULL)
child_set_env(&child_env, &envsize, "LANG", cp);
for (i = 0; i < NSIG; i++)
signal(i, SIG_DFL);
if ((devnull = open(_PATH_DEVNULL, O_RDWR)) == -1) {
error("%s: open %s: %s", tag, _PATH_DEVNULL,
strerror(errno));
_exit(1);
}
if (dup2(devnull, STDIN_FILENO) == -1) {
error("%s: dup2: %s", tag, strerror(errno));
_exit(1);
}
/* Set up stdout as requested; leave stderr in place for now. */
fd = -1;
if ((flags & SSH_SUBPROCESS_STDOUT_CAPTURE) != 0)
fd = p[1];
else if ((flags & SSH_SUBPROCESS_STDOUT_DISCARD) != 0)
fd = devnull;
if (fd != -1 && dup2(fd, STDOUT_FILENO) == -1) {
error("%s: dup2: %s", tag, strerror(errno));
_exit(1);
}
closefrom(STDERR_FILENO + 1);
/* Don't use permanently_set_uid() here to avoid fatal() */
if (setresgid(pw->pw_gid, pw->pw_gid, pw->pw_gid) != 0) {
error("%s: setresgid %u: %s", tag, (u_int)pw->pw_gid,
strerror(errno));
_exit(1);
}
if (setresuid(pw->pw_uid, pw->pw_uid, pw->pw_uid) != 0) {
error("%s: setresuid %u: %s", tag, (u_int)pw->pw_uid,
strerror(errno));
_exit(1);
}
/* stdin is pointed to /dev/null at this point */
if ((flags & SSH_SUBPROCESS_STDOUT_DISCARD) != 0 &&
dup2(STDIN_FILENO, STDERR_FILENO) == -1) {
error("%s: dup2: %s", tag, strerror(errno));
_exit(1);
}
execve(av[0], av, child_env);
error("%s exec \"%s\": %s", tag, command, strerror(errno));
_exit(127);
default: /* parent */
break;
}
close(p[1]);
if ((flags & SSH_SUBPROCESS_STDOUT_CAPTURE) == 0)
close(p[0]);
else if ((f = fdopen(p[0], "r")) == NULL) {
error("%s: fdopen: %s", tag, strerror(errno));
close(p[0]);
/* Don't leave zombie child */
kill(pid, SIGTERM);
while (waitpid(pid, NULL, 0) == -1 && errno == EINTR)
;
return 0;
}
/* Success */
debug3("%s: %s pid %ld", __func__, tag, (long)pid);
if (child != NULL)
*child = f;
return pid;
}
/* Returns 0 if pid exited cleanly, non-zero otherwise */ /* Returns 0 if pid exited cleanly, non-zero otherwise */
int int
exited_cleanly(pid_t pid, const char *tag, const char *cmd, int quiet) exited_cleanly(pid_t pid, const char *tag, const char *cmd, int quiet)

8
misc.h
View File

@ -1,4 +1,4 @@
/* $OpenBSD: misc.h,v 1.69 2017/12/05 23:59:47 dtucker Exp $ */ /* $OpenBSD: misc.h,v 1.70 2018/01/08 15:21:49 markus Exp $ */
/* /*
* Author: Tatu Ylonen <ylo@cs.hut.fi> * Author: Tatu Ylonen <ylo@cs.hut.fi>
@ -149,12 +149,6 @@ int argv_split(const char *, int *, char ***);
char *argv_assemble(int, char **argv); char *argv_assemble(int, char **argv);
int exited_cleanly(pid_t, const char *, const char *, int); int exited_cleanly(pid_t, const char *, const char *, int);
#define SSH_SUBPROCESS_STDOUT_DISCARD (1) /* Discard stdout */
#define SSH_SUBPROCESS_STDOUT_CAPTURE (1<<1) /* Redirect stdout */
#define SSH_SUBPROCESS_STDERR_DISCARD (1<<2) /* Discard stderr */
pid_t subprocess(const char *, struct passwd *,
const char *, int, char **, FILE **, u_int flags);
struct stat; struct stat;
int safe_path(const char *, struct stat *, const char *, uid_t, int safe_path(const char *, struct stat *, const char *, uid_t,
char *, size_t); char *, size_t);