1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
|
/*
* 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
*/
static const char Prog[] = "newgidmap";
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|fd:<pidfd>] <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 *target_str;
int proc_dir_fd;
int ranges;
struct map_range *mappings;
struct stat st;
struct passwd *pw;
bool allow_setgroups = false;
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 (strlen(target_str) > 3 && strncmp(target_str, "fd:", 3) == 0) {
/* the user passed in a /proc/pid fd for the process */
target_str = &target_str[3];
proc_dir_fd = get_pidfd_from_fd(target_str);
if (proc_dir_fd < 0)
usage();
} else {
proc_dir_fd = open_pidfd(target_str);
if (proc_dir_fd < 0)
usage();
}
/* 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 process\n"),
Prog);
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 process is owned by a different user: uid:%lu pw_uid:%lu st_uid:%lu, gid:%lu pw_gid:%lu st_gid:%lu\n" ),
Prog,
(unsigned long)getuid(), (unsigned long)pw->pw_uid, (unsigned long)st.st_uid,
(unsigned long)getgid(), (unsigned long)pw->pw_gid, (unsigned long)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;
}
|
