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
|
/*
* This program is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License as published by the
* Free Software Foundation; either version 2, or (at your option) any
* later version.
*
* This program 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
* General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/
#include <sys/prctl.h>
#include <stdio.h>
#include <stdlib.h>
#include <limits.h>
#include <errno.h>
#include "c.h"
#include "caputils.h"
#include "pathnames.h"
#include "procfs.h"
#include "nls.h"
static int test_cap(unsigned int cap)
{
/* prctl returns 0 or 1 for valid caps, -1 otherwise */
return prctl(PR_CAPBSET_READ, cap, 0, 0, 0) >= 0;
}
static int cap_last_by_bsearch(int *ret)
{
/* starting with cap=INT_MAX means we always know
* that cap1 is invalid after the first iteration */
int cap = INT_MAX;
unsigned int cap0 = 0, cap1 = INT_MAX;
while ((int)cap0 < cap) {
if (test_cap(cap))
cap0 = cap;
else
cap1 = cap;
cap = (cap0 + cap1) / 2U;
}
*ret = cap;
return 0;
}
static int cap_last_by_procfs(int *ret)
{
FILE *f = fopen(_PATH_PROC_CAPLASTCAP, "r");
int rc = -EINVAL;
*ret = 0;
if (f && fd_is_procfs(fileno(f))) {
int cap;
/* we check if the cap after this one really isn't valid */
if (fscanf(f, "%d", &cap) == 1 &&
cap < INT_MAX && !test_cap(cap + 1)) {
*ret = cap;
rc = 0;
}
}
if (f)
fclose(f);
return rc;
}
int cap_last_cap(void)
{
static int cap = -1;
if (cap != -1)
return cap;
if (cap_last_by_procfs(&cap) < 0)
cap_last_by_bsearch(&cap);
return cap;
}
void cap_permitted_to_ambient(void)
{
/* We use capabilities system calls to propagate the permitted
* capabilities into the ambient set because we may have
* already forked so be in async-signal-safe context. */
struct __user_cap_header_struct header = {
.version = _LINUX_CAPABILITY_VERSION_3,
.pid = 0,
};
struct __user_cap_data_struct payload[_LINUX_CAPABILITY_U32S_3] = {{ 0 }};
uint64_t effective, cap;
if (capget(&header, payload) < 0)
err(EXIT_FAILURE, _("capget failed"));
/* In order the make capabilities ambient, we first need to ensure
* that they are all inheritable. */
payload[0].inheritable = payload[0].permitted;
payload[1].inheritable = payload[1].permitted;
if (capset(&header, payload) < 0)
err(EXIT_FAILURE, _("capset failed"));
effective = ((uint64_t)payload[1].effective << 32) | (uint64_t)payload[0].effective;
for (cap = 0; cap < (sizeof(effective) * 8); cap++) {
/* This is the same check as cap_valid(), but using
* the runtime value for the last valid cap. */
if (cap > (uint64_t) cap_last_cap())
continue;
if ((effective & (1ULL << cap))
&& prctl(PR_CAP_AMBIENT, PR_CAP_AMBIENT_RAISE, cap, 0, 0) < 0)
err(EXIT_FAILURE, _("prctl(PR_CAP_AMBIENT) failed"));
}
}
#ifdef TEST_PROGRAM_CAPUTILS
int main(int argc, char *argv[])
{
int rc = 0, cap;
if (argc < 2) {
fprintf(stderr, "usage: %1$s --last-by-procfs\n"
" %1$s --last-by-bsearch\n"
" %1$s --last\n",
program_invocation_short_name);
return EXIT_FAILURE;
}
if (strcmp(argv[1], "--last-by-procfs") == 0) {
rc = cap_last_by_procfs(&cap);
if (rc == 0)
printf("last cap: %d\n", cap);
} else if (strcmp(argv[1], "--last-by-bsearch") == 0) {
rc = cap_last_by_bsearch(&cap);
if (rc == 0)
printf("last cap: %d\n", cap);
} else if (strcmp(argv[1], "--last") == 0)
printf("last cap: %d\n", cap_last_cap());
return rc == 0 ? EXIT_SUCCESS : EXIT_FAILURE;
}
#endif
|
