1 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
4
5 #include "sandbox/linux/seccomp-bpf-helpers/baseline_policy.h"
6
7 #include <errno.h>
8 #include <sys/mman.h>
9 #include <sys/socket.h>
10 #include <sys/syscall.h>
11 #include <sys/types.h>
12 #include <unistd.h>
13
14 #include "base/logging.h"
15 #include "build/build_config.h"
16 #include "sandbox/linux/bpf_dsl/bpf_dsl.h"
17 #include "sandbox/linux/seccomp-bpf-helpers/sigsys_handlers.h"
18 #include "sandbox/linux/seccomp-bpf-helpers/syscall_parameters_restrictions.h"
19 #include "sandbox/linux/seccomp-bpf-helpers/syscall_sets.h"
20 #include "sandbox/linux/seccomp-bpf/sandbox_bpf.h"
21 #include "sandbox/linux/services/syscall_wrappers.h"
22 #include "sandbox/linux/system_headers/linux_syscalls.h"
23
24 #if !defined(SO_PEEK_OFF)
25 #define SO_PEEK_OFF 42
26 #endif
27
28 // Changing this implementation will have an effect on *all* policies.
29 // Currently this means: Renderer/Worker, GPU, Flash and NaCl.
30
31 using sandbox::bpf_dsl::Allow;
32 using sandbox::bpf_dsl::Arg;
33 using sandbox::bpf_dsl::Error;
34 using sandbox::bpf_dsl::If;
35 using sandbox::bpf_dsl::ResultExpr;
36
37 namespace sandbox {
38
39 namespace {
40
IsBaselinePolicyAllowed(int sysno)41 bool IsBaselinePolicyAllowed(int sysno) {
42 return SyscallSets::IsAllowedAddressSpaceAccess(sysno) ||
43 SyscallSets::IsAllowedBasicScheduler(sysno) ||
44 SyscallSets::IsAllowedEpoll(sysno) ||
45 SyscallSets::IsAllowedFileSystemAccessViaFd(sysno) ||
46 SyscallSets::IsAllowedFutex(sysno) ||
47 SyscallSets::IsAllowedGeneralIo(sysno) ||
48 SyscallSets::IsAllowedGetOrModifySocket(sysno) ||
49 SyscallSets::IsAllowedGettime(sysno) ||
50 SyscallSets::IsAllowedProcessStartOrDeath(sysno) ||
51 SyscallSets::IsAllowedSignalHandling(sysno) ||
52 SyscallSets::IsGetSimpleId(sysno) ||
53 SyscallSets::IsKernelInternalApi(sysno) ||
54 #if defined(__arm__)
55 SyscallSets::IsArmPrivate(sysno) ||
56 #endif
57 #if defined(__mips__)
58 SyscallSets::IsMipsPrivate(sysno) ||
59 #endif
60 SyscallSets::IsAllowedOperationOnFd(sysno);
61 }
62
63 // System calls that will trigger the crashing SIGSYS handler.
IsBaselinePolicyWatched(int sysno)64 bool IsBaselinePolicyWatched(int sysno) {
65 return SyscallSets::IsAdminOperation(sysno) ||
66 SyscallSets::IsAdvancedScheduler(sysno) ||
67 SyscallSets::IsAdvancedTimer(sysno) ||
68 SyscallSets::IsAsyncIo(sysno) ||
69 SyscallSets::IsDebug(sysno) ||
70 SyscallSets::IsEventFd(sysno) ||
71 SyscallSets::IsExtendedAttributes(sysno) ||
72 SyscallSets::IsFaNotify(sysno) ||
73 SyscallSets::IsFsControl(sysno) ||
74 SyscallSets::IsGlobalFSViewChange(sysno) ||
75 SyscallSets::IsGlobalProcessEnvironment(sysno) ||
76 SyscallSets::IsGlobalSystemStatus(sysno) ||
77 SyscallSets::IsInotify(sysno) ||
78 SyscallSets::IsKernelModule(sysno) ||
79 SyscallSets::IsKeyManagement(sysno) ||
80 SyscallSets::IsKill(sysno) ||
81 SyscallSets::IsMessageQueue(sysno) ||
82 SyscallSets::IsMisc(sysno) ||
83 #if defined(__x86_64__)
84 SyscallSets::IsNetworkSocketInformation(sysno) ||
85 #endif
86 SyscallSets::IsNuma(sysno) ||
87 SyscallSets::IsPrctl(sysno) ||
88 SyscallSets::IsProcessGroupOrSession(sysno) ||
89 #if defined(__i386__) || defined(__mips__)
90 SyscallSets::IsSocketCall(sysno) ||
91 #endif
92 #if defined(__arm__)
93 SyscallSets::IsArmPciConfig(sysno) ||
94 #endif
95 #if defined(__mips__)
96 SyscallSets::IsMipsMisc(sysno) ||
97 #endif
98 SyscallSets::IsTimer(sysno);
99 }
100
101 // |fs_denied_errno| is the errno return for denied filesystem access.
EvaluateSyscallImpl(int fs_denied_errno,pid_t current_pid,int sysno)102 ResultExpr EvaluateSyscallImpl(int fs_denied_errno,
103 pid_t current_pid,
104 int sysno) {
105 #if defined(ADDRESS_SANITIZER) || defined(THREAD_SANITIZER) || \
106 defined(MEMORY_SANITIZER)
107 // TCGETS is required by the sanitizers on failure.
108 if (sysno == __NR_ioctl) {
109 return RestrictIoctl();
110 }
111
112 if (sysno == __NR_sched_getaffinity) {
113 return Allow();
114 }
115
116 // Used when RSS limiting is enabled in sanitizers.
117 if (sysno == __NR_getrusage) {
118 return RestrictGetrusage();
119 }
120
121 if (sysno == __NR_sigaltstack) {
122 // Required for better stack overflow detection in ASan. Disallowed in
123 // non-ASan builds.
124 return Allow();
125 }
126 #endif // defined(ADDRESS_SANITIZER) || defined(THREAD_SANITIZER) ||
127 // defined(MEMORY_SANITIZER)
128
129 if (IsBaselinePolicyAllowed(sysno)) {
130 return Allow();
131 }
132
133 #if defined(OS_ANDROID)
134 // Needed for thread creation.
135 if (sysno == __NR_sigaltstack)
136 return Allow();
137 #endif
138
139 if (sysno == __NR_clock_gettime) {
140 return RestrictClockID();
141 }
142
143 if (sysno == __NR_clone) {
144 return RestrictCloneToThreadsAndEPERMFork();
145 }
146
147 if (sysno == __NR_fcntl)
148 return RestrictFcntlCommands();
149
150 #if defined(__i386__) || defined(__arm__) || defined(__mips__)
151 if (sysno == __NR_fcntl64)
152 return RestrictFcntlCommands();
153 #endif
154
155 #if !defined(__aarch64__)
156 // fork() is never used as a system call (clone() is used instead), but we
157 // have seen it in fallback code on Android.
158 if (sysno == __NR_fork) {
159 return Error(EPERM);
160 }
161 #endif
162
163 if (sysno == __NR_futex)
164 return RestrictFutex();
165
166 if (sysno == __NR_set_robust_list)
167 return Error(EPERM);
168
169 if (sysno == __NR_getpriority || sysno ==__NR_setpriority)
170 return RestrictGetSetpriority(current_pid);
171
172 if (sysno == __NR_madvise) {
173 // Only allow MADV_DONTNEED (aka MADV_FREE).
174 const Arg<int> advice(2);
175 return If(advice == MADV_DONTNEED, Allow()).Else(Error(EPERM));
176 }
177
178 #if defined(__i386__) || defined(__x86_64__) || defined(__mips__) || \
179 defined(__aarch64__)
180 if (sysno == __NR_mmap)
181 return RestrictMmapFlags();
182 #endif
183
184 #if defined(__i386__) || defined(__arm__) || defined(__mips__)
185 if (sysno == __NR_mmap2)
186 return RestrictMmapFlags();
187 #endif
188
189 if (sysno == __NR_mprotect)
190 return RestrictMprotectFlags();
191
192 if (sysno == __NR_prctl)
193 return RestrictPrctl();
194
195 #if defined(__x86_64__) || defined(__arm__) || defined(__mips__) || \
196 defined(__aarch64__)
197 if (sysno == __NR_socketpair) {
198 // Only allow AF_UNIX, PF_UNIX. Crash if anything else is seen.
199 static_assert(AF_UNIX == PF_UNIX,
200 "af_unix and pf_unix should not be different");
201 const Arg<int> domain(0);
202 return If(domain == AF_UNIX, Allow()).Else(CrashSIGSYS());
203 }
204 #endif
205
206 if (SyscallSets::IsKill(sysno)) {
207 return RestrictKillTarget(current_pid, sysno);
208 }
209
210 if (SyscallSets::IsFileSystem(sysno) ||
211 SyscallSets::IsCurrentDirectory(sysno)) {
212 return Error(fs_denied_errno);
213 }
214
215 if (SyscallSets::IsSeccomp(sysno))
216 return Error(EPERM);
217
218 if (SyscallSets::IsAnySystemV(sysno)) {
219 return Error(EPERM);
220 }
221
222 if (SyscallSets::IsUmask(sysno) ||
223 SyscallSets::IsDeniedFileSystemAccessViaFd(sysno) ||
224 SyscallSets::IsDeniedGetOrModifySocket(sysno) ||
225 SyscallSets::IsProcessPrivilegeChange(sysno)) {
226 return Error(EPERM);
227 }
228
229 #if defined(__i386__) || defined(__mips__)
230 if (SyscallSets::IsSocketCall(sysno))
231 return RestrictSocketcallCommand();
232 #endif
233
234 #if !defined(__i386__)
235 if (sysno == __NR_getsockopt || sysno ==__NR_setsockopt) {
236 // Used by Mojo EDK to catch a message pipe being sent over itself.
237 const Arg<int> level(1);
238 const Arg<int> optname(2);
239 return If(AllOf(level == SOL_SOCKET, optname == SO_PEEK_OFF), Allow())
240 .Else(CrashSIGSYS());
241 }
242 #endif
243
244 if (IsBaselinePolicyWatched(sysno)) {
245 // Previously unseen syscalls. TODO(jln): some of these should
246 // be denied gracefully right away.
247 return CrashSIGSYS();
248 }
249
250 // In any other case crash the program with our SIGSYS handler.
251 return CrashSIGSYS();
252 }
253
254 } // namespace.
255
256 // Unfortunately C++03 doesn't allow delegated constructors.
257 // Call other constructor when C++11 lands.
BaselinePolicy()258 BaselinePolicy::BaselinePolicy() : BaselinePolicy(EPERM) {}
259
BaselinePolicy(int fs_denied_errno)260 BaselinePolicy::BaselinePolicy(int fs_denied_errno)
261 : fs_denied_errno_(fs_denied_errno), policy_pid_(sys_getpid()) {
262 }
263
~BaselinePolicy()264 BaselinePolicy::~BaselinePolicy() {
265 // Make sure that this policy is created, used and destroyed by a single
266 // process.
267 DCHECK_EQ(sys_getpid(), policy_pid_);
268 }
269
EvaluateSyscall(int sysno) const270 ResultExpr BaselinePolicy::EvaluateSyscall(int sysno) const {
271 // Sanity check that we're only called with valid syscall numbers.
272 DCHECK(SandboxBPF::IsValidSyscallNumber(sysno));
273 // Make sure that this policy is used in the creating process.
274 if (1 == sysno) {
275 DCHECK_EQ(sys_getpid(), policy_pid_);
276 }
277 return EvaluateSyscallImpl(fs_denied_errno_, policy_pid_, sysno);
278 }
279
InvalidSyscall() const280 ResultExpr BaselinePolicy::InvalidSyscall() const {
281 return CrashSIGSYS();
282 }
283
284 } // namespace sandbox.
285