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/* Capture output from a subprocess.
Copyright (C) 2017-2021 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#include <support/subprocess.h>
#include <support/capture_subprocess.h>
#include <errno.h>
#include <fcntl.h>
#include <stdlib.h>
#include <support/check.h>
#include <support/xunistd.h>
#include <support/xsocket.h>
#include <support/xspawn.h>
#include <support/support.h>
#include <support/test-driver.h>
static void
transfer (const char *what, struct pollfd *pfd, struct xmemstream *stream)
{
if (pfd->revents != 0)
{
char buf[1024];
ssize_t ret = TEMP_FAILURE_RETRY (read (pfd->fd, buf, sizeof (buf)));
if (ret < 0)
{
support_record_failure ();
printf ("error: reading from subprocess %s: %m\n", what);
pfd->events = 0;
pfd->revents = 0;
}
else if (ret == 0)
{
/* EOF reached. Stop listening. */
pfd->events = 0;
pfd->revents = 0;
}
else
/* Store the data just read. */
TEST_VERIFY (fwrite (buf, ret, 1, stream->out) == 1);
}
}
static void
support_capture_poll (struct support_capture_subprocess *result,
struct support_subprocess *proc)
{
struct pollfd fds[2] =
{
{ .fd = proc->stdout_pipe[0], .events = POLLIN },
{ .fd = proc->stderr_pipe[0], .events = POLLIN },
};
do
{
xpoll (fds, 2, -1);
transfer ("stdout", &fds[0], &result->out);
transfer ("stderr", &fds[1], &result->err);
}
while (fds[0].events != 0 || fds[1].events != 0);
xfclose_memstream (&result->out);
xfclose_memstream (&result->err);
result->status = support_process_wait (proc);
}
struct support_capture_subprocess
support_capture_subprocess (void (*callback) (void *), void *closure)
{
struct support_capture_subprocess result;
xopen_memstream (&result.out);
xopen_memstream (&result.err);
struct support_subprocess proc = support_subprocess (callback, closure);
support_capture_poll (&result, &proc);
return result;
}
struct support_capture_subprocess
support_capture_subprogram (const char *file, char *const argv[])
{
struct support_capture_subprocess result;
xopen_memstream (&result.out);
xopen_memstream (&result.err);
struct support_subprocess proc = support_subprogram (file, argv);
support_capture_poll (&result, &proc);
return result;
}
/* Copies the executable into a restricted directory, so that we can
safely make it SGID with the TARGET group ID. Then runs the
executable. */
static int
copy_and_spawn_sgid (char *child_id, gid_t gid)
{
char *dirname = xasprintf ("%s/tst-tunables-setuid.%jd",
test_dir, (intmax_t) getpid ());
char *execname = xasprintf ("%s/bin", dirname);
int infd = -1;
int outfd = -1;
int ret = 1, status = 1;
TEST_VERIFY (mkdir (dirname, 0700) == 0);
if (support_record_failure_is_failed ())
goto err;
infd = open ("/proc/self/exe", O_RDONLY);
if (infd < 0)
FAIL_UNSUPPORTED ("unsupported: Cannot read binary from procfs\n");
outfd = open (execname, O_WRONLY | O_CREAT | O_EXCL, 0700);
TEST_VERIFY (outfd >= 0);
if (support_record_failure_is_failed ())
goto err;
char buf[4096];
for (;;)
{
ssize_t rdcount = read (infd, buf, sizeof (buf));
TEST_VERIFY (rdcount >= 0);
if (support_record_failure_is_failed ())
goto err;
if (rdcount == 0)
break;
char *p = buf;
char *end = buf + rdcount;
while (p != end)
{
ssize_t wrcount = write (outfd, buf, end - p);
if (wrcount == 0)
errno = ENOSPC;
TEST_VERIFY (wrcount > 0);
if (support_record_failure_is_failed ())
goto err;
p += wrcount;
}
}
TEST_VERIFY (fchown (outfd, getuid (), gid) == 0);
if (support_record_failure_is_failed ())
goto err;
TEST_VERIFY (fchmod (outfd, 02750) == 0);
if (support_record_failure_is_failed ())
goto err;
TEST_VERIFY (close (outfd) == 0);
if (support_record_failure_is_failed ())
goto err;
TEST_VERIFY (close (infd) == 0);
if (support_record_failure_is_failed ())
goto err;
/* We have the binary, now spawn the subprocess. Avoid using
support_subprogram because we only want the program exit status, not the
contents. */
ret = 0;
char * const args[] = {execname, child_id, NULL};
status = support_subprogram_wait (args[0], args);
err:
if (outfd >= 0)
close (outfd);
if (infd >= 0)
close (infd);
if (execname != NULL)
{
unlink (execname);
free (execname);
}
if (dirname != NULL)
{
rmdir (dirname);
free (dirname);
}
if (ret != 0)
FAIL_EXIT1("Failed to make sgid executable for test\n");
return status;
}
int
support_capture_subprogram_self_sgid (char *child_id)
{
gid_t target = 0;
const int count = 64;
gid_t groups[count];
/* Get a GID which is not our current GID, but is present in the
supplementary group list. */
int ret = getgroups (count, groups);
if (ret < 0)
FAIL_UNSUPPORTED("Could not get group list for user %jd\n",
(intmax_t) getuid ());
gid_t current = getgid ();
for (int i = 0; i < ret; ++i)
{
if (groups[i] != current)
{
target = groups[i];
break;
}
}
if (target == 0)
FAIL_UNSUPPORTED("Could not find a suitable GID for user %jd\n",
(intmax_t) getuid ());
return copy_and_spawn_sgid (child_id, target);
}
void
support_capture_subprocess_free (struct support_capture_subprocess *p)
{
free (p->out.buffer);
free (p->err.buffer);
}
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