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
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
|
/*
* SPDX-License-Identifier: ISC
*
* Copyright (c) 2004-2005, 2010-2018 Todd C. Miller <Todd.Miller@sudo.ws>
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
/*
* This is an open source non-commercial project. Dear PVS-Studio, please check it.
* PVS-Studio Static Code Analyzer for C, C++ and C#: http://www.viva64.com
*/
#include <config.h>
#include <sys/types.h>
#if defined(HAVE_DECL_SECCOMP_SET_MODE_FILTER) && HAVE_DECL_SECCOMP_SET_MODE_FILTER
# include <sys/prctl.h>
# include <asm/unistd.h>
# include <linux/filter.h>
# include <linux/seccomp.h>
#endif
#include <errno.h>
#include <stdarg.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#ifdef HAVE_SPAWN_H
#include <spawn.h>
#endif
#include <string.h>
#ifdef HAVE_WORDEXP_H
#include <wordexp.h>
#endif
#if defined(HAVE_SHL_LOAD)
# include <dl.h>
#elif defined(HAVE_DLOPEN)
# include <dlfcn.h>
#endif
#include "sudo_compat.h"
#include "pathnames.h"
#ifdef HAVE___INTERPOSE
/*
* Mac OS X 10.4 and above has support for library symbol interposition.
* There is a good explanation of this in the Mac OS X Internals book.
*/
typedef struct interpose_s {
void *new_func;
void *orig_func;
} interpose_t;
# define FN_NAME(fn) fake_ ## fn
# define INTERPOSE(fn) \
__attribute__((__used__)) static const interpose_t interpose_ ## fn \
__attribute__((__section__("__DATA,__interpose"))) = \
{ (void *)fake_ ## fn, (void *)fn };
#else
# define FN_NAME(fn) fn
# define INTERPOSE(fn)
#endif
/*
* Replacements for the exec(3) family of syscalls. It is not enough to
* just replace execve(2) since many C libraries do not call the public
* execve(2) interface. Note that it is still possible to access the real
* syscalls via the syscall(2) interface, but that is rarely done.
*/
#define EXEC_REPL_BODY \
{ \
errno = EACCES; \
return -1; \
}
#define EXEC_REPL1(fn, t1) \
sudo_dso_public int \
FN_NAME(fn)(t1 a1) \
EXEC_REPL_BODY \
INTERPOSE(fn)
#define EXEC_REPL2(fn, t1, t2) \
sudo_dso_public int \
FN_NAME(fn)(t1 a1, t2 a2) \
EXEC_REPL_BODY \
INTERPOSE(fn)
#define EXEC_REPL3(fn, t1, t2, t3) \
sudo_dso_public int \
FN_NAME(fn)(t1 a1, t2 a2, t3 a3) \
EXEC_REPL_BODY \
INTERPOSE(fn)
#define EXEC_REPL6(fn, t1, t2, t3, t4, t5, t6) \
sudo_dso_public int \
FN_NAME(fn)(t1 a1, t2 a2, t3 a3, t4 a4, t5 a5, t6 a6) \
EXEC_REPL_BODY \
INTERPOSE(fn)
#define EXEC_REPL_VA(fn, t1, t2) \
sudo_dso_public int \
FN_NAME(fn)(t1 a1, t2 a2, ...) \
EXEC_REPL_BODY \
INTERPOSE(fn)
/*
* Standard exec(3) family of functions.
*/
EXEC_REPL_VA(execl, const char *, const char *)
EXEC_REPL_VA(execle, const char *, const char *)
EXEC_REPL_VA(execlp, const char *, const char *)
EXEC_REPL2(execv, const char *, char * const *)
EXEC_REPL2(execvp, const char *, char * const *)
EXEC_REPL3(execve, const char *, char * const *, char * const *)
/*
* Non-standard exec(3) functions and corresponding private versions.
*/
#ifdef HAVE_EXECVP
EXEC_REPL3(execvP, const char *, const char *, char * const *)
#endif
#ifdef HAVE_EXECVPE
EXEC_REPL3(execvpe, const char *, char * const *, char * const *)
#endif
#ifdef HAVE_EXECT
EXEC_REPL3(exect, const char *, char * const *, char * const *)
#endif
/*
* Not all systems support fexecve(2), posix_spawn(2) and posix_spawnp(2).
*/
#ifdef HAVE_FEXECVE
EXEC_REPL3(fexecve, int , char * const *, char * const *)
#endif
#ifdef HAVE_POSIX_SPAWN
EXEC_REPL6(posix_spawn, pid_t *, const char *, const posix_spawn_file_actions_t *, const posix_spawnattr_t *, char * const *, char * const *)
#endif
#ifdef HAVE_POSIX_SPAWNP
EXEC_REPL6(posix_spawnp, pid_t *, const char *, const posix_spawn_file_actions_t *, const posix_spawnattr_t *, char * const *, char * const *)
#endif
/*
* system(3) and popen(3).
* We can't use a wrapper for popen since it returns FILE *, not int.
*/
EXEC_REPL1(system, const char *)
sudo_dso_public FILE *
FN_NAME(popen)(const char *c, const char *t)
{
errno = EACCES;
return NULL;
}
INTERPOSE(popen)
#if defined(HAVE_WORDEXP) && (defined(RTLD_NEXT) || defined(HAVE_SHL_LOAD) || defined(HAVE___INTERPOSE))
/*
* We can't use a wrapper for wordexp(3) since we still want to call
* the real wordexp(3) but with WRDE_NOCMD added to the flags argument.
*/
typedef int (*sudo_fn_wordexp_t)(const char *, wordexp_t *, int);
sudo_dso_public int
FN_NAME(wordexp)(const char *words, wordexp_t *we, int flags)
{
#if defined(HAVE___INTERPOSE)
return wordexp(words, we, flags | WRDE_NOCMD);
#else
# if defined(HAVE_DLOPEN)
void *fn = dlsym(RTLD_NEXT, "wordexp");
# elif defined(HAVE_SHL_LOAD)
const char *name, *myname = _PATH_SUDO_NOEXEC;
struct shl_descriptor *desc;
void *fn = NULL;
int idx = 0;
name = strrchr(myname, '/');
if (name != NULL)
myname = name + 1;
/* Search for wordexp() but skip this shared object. */
while (shl_get(idx++, &desc) == 0) {
name = strrchr(desc->filename, '/');
if (name == NULL)
name = desc->filename;
else
name++;
if (strcmp(name, myname) == 0)
continue;
if (shl_findsym(&desc->handle, "wordexp", TYPE_PROCEDURE, &fn) == 0)
break;
}
# else
void *fn = NULL;
# endif
if (fn == NULL) {
errno = EACCES;
return -1;
}
return ((sudo_fn_wordexp_t)fn)(words, we, flags | WRDE_NOCMD);
#endif /* HAVE___INTERPOSE */
}
INTERPOSE(wordexp)
#endif /* HAVE_WORDEXP && (RTLD_NEXT || HAVE_SHL_LOAD || HAVE___INTERPOSE) */
/*
* On Linux we can use a seccomp() filter to disable exec.
*/
#if defined(HAVE_DECL_SECCOMP_SET_MODE_FILTER) && HAVE_DECL_SECCOMP_SET_MODE_FILTER
/* Older systems may not support execveat(2). */
#ifndef __NR_execveat
# define __NR_execveat -1
#endif
static void noexec_ctor(void) __attribute__((constructor));
static void
noexec_ctor(void)
{
struct sock_filter exec_filter[] = {
/* Load syscall number into the accumulator */
BPF_STMT(BPF_LD | BPF_ABS, offsetof(struct seccomp_data, nr)),
/* Jump to deny for execve/execveat */
BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, __NR_execve, 2, 0),
BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, __NR_execveat, 1, 0),
/* Allow non-matching syscalls */
BPF_STMT(BPF_RET | BPF_K, SECCOMP_RET_ALLOW),
/* Deny execve/execveat syscall */
BPF_STMT(BPF_RET | BPF_K, SECCOMP_RET_ERRNO | (EACCES & SECCOMP_RET_DATA))
};
const struct sock_fprog exec_fprog = {
nitems(exec_filter),
exec_filter
};
/*
* SECCOMP_MODE_FILTER will fail unless the process has
* CAP_SYS_ADMIN or the no_new_privs bit is set.
*/
if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0) == 0)
(void)prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &exec_fprog);
}
#endif /* HAVE_DECL_SECCOMP_SET_MODE_FILTER */
|
