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/*
* SPDX-FileCopyrightText: 2013 Eric Biederman
*
* SPDX-License-Identifier: BSD-3-Clause
*/
#include <config.h>
#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <stdbool.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include "defines.h"
#include "prototypes.h"
#include "subordinateio.h"
#include "getdef.h"
#include "idmapping.h"
#include "shadowlog.h"
/*
* Global variables
*/
const char *Prog;
static bool verify_range(struct passwd *pw, struct map_range *range, bool *allow_setgroups)
{
/* An empty range is invalid */
if (range->count == 0)
return false;
/* Test /etc/subgid. If the mapping is valid then we allow setgroups. */
if (have_sub_gids(pw->pw_name, range->lower, range->count)) {
*allow_setgroups = true;
return true;
}
/* Allow a process to map its own gid. */
if ((range->count == 1) && (getgid() == range->lower)) {
/* noop -- if setgroups is enabled already we won't disable it. */
return true;
}
return false;
}
static void verify_ranges(struct passwd *pw, int ranges,
struct map_range *mappings, bool *allow_setgroups)
{
struct map_range *mapping;
int idx;
mapping = mappings;
for (idx = 0; idx < ranges; idx++, mapping++) {
if (!verify_range(pw, mapping, allow_setgroups)) {
fprintf(stderr, _( "%s: gid range [%lu-%lu) -> [%lu-%lu) not allowed\n"),
Prog,
mapping->upper,
mapping->upper + mapping->count,
mapping->lower,
mapping->lower + mapping->count);
exit(EXIT_FAILURE);
}
}
}
static void usage(void)
{
fprintf(stderr, _("usage: %s <pid> <gid> <lowergid> <count> [ <gid> <lowergid> <count> ] ... \n"), Prog);
exit(EXIT_FAILURE);
}
static void write_setgroups(int proc_dir_fd, bool allow_setgroups)
{
int setgroups_fd;
const char *policy;
char policy_buffer[4096];
/*
* Default is "deny", and any "allow" will out-rank a "deny". We don't
* forcefully write an "allow" here because the process we are writing
* mappings for may have already set themselves to "deny" (and "allow"
* is the default anyway). So allow_setgroups == true is a noop.
*/
policy = "deny\n";
if (allow_setgroups)
return;
setgroups_fd = openat(proc_dir_fd, "setgroups", O_RDWR|O_CLOEXEC);
if (setgroups_fd < 0) {
/*
* If it's an ENOENT then we are on too old a kernel for the setgroups
* code to exist. Emit a warning and bail on this.
*/
if (ENOENT == errno) {
fprintf(stderr, _("%s: kernel doesn't support setgroups restrictions\n"), Prog);
goto out;
}
fprintf(stderr, _("%s: couldn't open process setgroups: %s\n"),
Prog,
strerror(errno));
exit(EXIT_FAILURE);
}
/*
* Check whether the policy is already what we want. /proc/self/setgroups
* is write-once, so attempting to write after it's already written to will
* fail.
*/
if (read(setgroups_fd, policy_buffer, sizeof(policy_buffer)) < 0) {
fprintf(stderr, _("%s: failed to read setgroups: %s\n"),
Prog,
strerror(errno));
exit(EXIT_FAILURE);
}
if (!strncmp(policy_buffer, policy, strlen(policy)))
goto out;
/* Write the policy. */
if (lseek(setgroups_fd, 0, SEEK_SET) < 0) {
fprintf(stderr, _("%s: failed to seek setgroups: %s\n"),
Prog,
strerror(errno));
exit(EXIT_FAILURE);
}
if (dprintf(setgroups_fd, "%s", policy) < 0) {
fprintf(stderr, _("%s: failed to setgroups %s policy: %s\n"),
Prog,
policy,
strerror(errno));
exit(EXIT_FAILURE);
}
out:
close(setgroups_fd);
}
/*
* newgidmap - Set the gid_map for the specified process
*/
int main(int argc, char **argv)
{
char proc_dir_name[32];
char *target_str;
pid_t target;
int proc_dir_fd;
int ranges;
struct map_range *mappings;
struct stat st;
struct passwd *pw;
int written;
bool allow_setgroups = false;
Prog = Basename (argv[0]);
log_set_progname(Prog);
log_set_logfd(stderr);
/*
* The valid syntax are
* newgidmap target_pid
*/
if (argc < 2)
usage();
/* Find the process that needs its user namespace
* gid mapping set.
*/
target_str = argv[1];
if (!get_pid(target_str, &target))
usage();
/* max string length is 6 + 10 + 1 + 1 = 18, allocate 32 bytes */
written = snprintf(proc_dir_name, sizeof(proc_dir_name), "/proc/%u/",
target);
if ((written <= 0) || (written >= sizeof(proc_dir_name))) {
fprintf(stderr, "%s: snprintf of proc path failed: %s\n",
Prog, strerror(errno));
}
proc_dir_fd = open(proc_dir_name, O_DIRECTORY);
if (proc_dir_fd < 0) {
fprintf(stderr, _("%s: Could not open proc directory for target %u\n"),
Prog, target);
return EXIT_FAILURE;
}
/* Who am i? */
pw = get_my_pwent ();
if (NULL == pw) {
fprintf (stderr,
_("%s: Cannot determine your user name.\n"),
Prog);
SYSLOG ((LOG_WARN, "Cannot determine the user name of the caller (UID %lu)",
(unsigned long) getuid ()));
return EXIT_FAILURE;
}
/* Get the effective uid and effective gid of the target process */
if (fstat(proc_dir_fd, &st) < 0) {
fprintf(stderr, _("%s: Could not stat directory for target %u\n"),
Prog, target);
return EXIT_FAILURE;
}
/* Verify real user and real group matches the password entry
* and the effective user and group of the program whose
* mappings we have been asked to set.
*/
if ((getuid() != pw->pw_uid) ||
(!getdef_bool("GRANT_AUX_GROUP_SUBIDS") && (getgid() != pw->pw_gid)) ||
(pw->pw_uid != st.st_uid) ||
(getgid() != st.st_gid)) {
fprintf(stderr, _( "%s: Target %u is owned by a different user: uid:%lu pw_uid:%lu st_uid:%lu, gid:%lu pw_gid:%lu st_gid:%lu\n" ),
Prog, target,
(unsigned long int)getuid(), (unsigned long int)pw->pw_uid, (unsigned long int)st.st_uid,
(unsigned long int)getgid(), (unsigned long int)pw->pw_gid, (unsigned long int)st.st_gid);
return EXIT_FAILURE;
}
if (!sub_gid_open(O_RDONLY)) {
return EXIT_FAILURE;
}
ranges = ((argc - 2) + 2) / 3;
mappings = get_map_ranges(ranges, argc - 2, argv + 2);
if (!mappings)
usage();
verify_ranges(pw, ranges, mappings, &allow_setgroups);
write_setgroups(proc_dir_fd, allow_setgroups);
write_mapping(proc_dir_fd, ranges, mappings, "gid_map", pw->pw_uid);
sub_gid_close();
return EXIT_SUCCESS;
}
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