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Side by Side Diff: sandbox/linux/services/libc_urandom_override.cc

Issue 17066002: attempt to make the libc urandom override work for non-glibc too (Closed) Base URL: https://chromium.googlesource.com/chromium/src.git@master
Patch Set: remove ifdefs Created 7 years, 6 months ago
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1 // Copyright (c) 2012 The Chromium Authors. All rights reserved. 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 2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file. 3 // found in the LICENSE file.
4 4
5 #include "sandbox/linux/services/libc_urandom_override.h" 5 #include "sandbox/linux/services/libc_urandom_override.h"
6 6
7 #include <dlfcn.h> 7 #include <dlfcn.h>
8 #include <pthread.h> 8 #include <pthread.h>
9 #include <stdio.h> 9 #include <stdio.h>
10 #include <sys/stat.h> 10 #include <sys/stat.h>
11 #include <unistd.h> 11 #include <unistd.h>
12 12
13 #include "base/logging.h" 13 #include "base/logging.h"
14 #include "base/posix/eintr_wrapper.h" 14 #include "base/posix/eintr_wrapper.h"
15 #include "base/rand_util.h" 15 #include "base/rand_util.h"
16 16
17 // Note: this file is used by the zygote and nacl_helper. 17 // Note: this file is used by the zygote and nacl_helper.
18 18
19 // This is used when mapping stat* calls to __xstat* calls.
20 #define XSTAT_VERSION 3
21
19 namespace sandbox { 22 namespace sandbox {
20 23
21 static bool g_override_urandom = false; 24 static bool g_override_urandom = false;
22 25
23 void InitLibcUrandomOverrides() {
24 // Make sure /dev/urandom is open.
25 base::GetUrandomFD();
26 g_override_urandom = true;
27 }
28
29 // TODO(sergeyu): Currently this code doesn't work properly under ASAN 26 // TODO(sergeyu): Currently this code doesn't work properly under ASAN
30 // - it crashes content_unittests. Make sure it works properly and 27 // - it crashes content_unittests. Make sure it works properly and
31 // enable it here. http://crbug.com/123263 28 // enable it here. http://crbug.com/123263
32 #if !defined(ADDRESS_SANITIZER) 29 #if !defined(ADDRESS_SANITIZER)
33 30
34 static const char kUrandomDevPath[] = "/dev/urandom"; 31 static const char kUrandomDevPath[] = "/dev/urandom";
35 32
36 typedef FILE* (*FopenFunction)(const char* path, const char* mode); 33 typedef FILE* (*FopenFunction)(const char* path, const char* mode);
37 typedef int (*XstatFunction)(int version, const char *path, struct stat *buf); 34 typedef int (*XstatFunction)(int version, const char *path, struct stat *buf);
38 typedef int (*Xstat64Function)(int version, const char *path, 35 typedef int (*Xstat64Function)(int version, const char *path,
39 struct stat64 *buf); 36 struct stat64 *buf);
37 typedef int (*StatFunction)(const char *path, struct stat *buf);
38 typedef int (*Stat64Function)(const char *path, struct stat64 *buf);
39 typedef int (*FxstatFunction)(int version, int fd, struct stat *buf);
40 typedef int (*Fxstat64Function)(int version, int fd, struct stat64 *buf);
40 41
41 static pthread_once_t g_libc_file_io_funcs_guard = PTHREAD_ONCE_INIT; 42 static pthread_once_t g_libc_file_io_funcs_guard = PTHREAD_ONCE_INIT;
42 static FopenFunction g_libc_fopen; 43 static FopenFunction g_libc_fopen = NULL;
43 static FopenFunction g_libc_fopen64; 44 static FopenFunction g_libc_fopen64 = NULL;
44 static XstatFunction g_libc_xstat; 45 static XstatFunction g_libc_xstat = NULL;
45 static Xstat64Function g_libc_xstat64; 46 static Xstat64Function g_libc_xstat64 = NULL;
47 static StatFunction g_libc_stat = NULL;
48 static Stat64Function g_libc_stat64 = NULL;
49 static FxstatFunction g_libc_fxstat = NULL;
50 static Fxstat64Function g_libc_fxstat64 = NULL;
51
52 void InitLibcUrandomOverrides() {
53 // Make sure /dev/urandom is open.
jln (very slow on Chromium) 2013/06/25 23:00:03 Calling InitLibcFileIOFunctions() here would guara
Mostyn Bramley-Moore 2013/06/26 10:30:18 Done.
54 base::GetUrandomFD();
55 g_override_urandom = true;
56 }
46 57
47 static void InitLibcFileIOFunctions() { 58 static void InitLibcFileIOFunctions() {
59 // find the libc's real fopen* and *stat* functions
jln (very slow on Chromium) 2013/06/25 23:00:03 Nit: comment above the function, start with a capi
Mostyn Bramley-Moore 2013/06/26 00:09:57 Done.
60
61 // TODO(mostynb): call this once near the start of the init sequence, don't
62 // call it repeatedly with pthread_once() - ZygoteMain is not early enough.
jln (very slow on Chromium) 2013/06/25 23:00:03 In practice it'll only be called once, right? If
Mostyn Bramley-Moore 2013/06/25 23:40:41 This function is only called once, what I was tryi
jln (very slow on Chromium) 2013/06/26 01:57:21 Yeah, I'm not worried about mutiple calls to pthre
Mostyn Bramley-Moore 2013/06/26 10:30:18 Done in patchset 11.
63
48 g_libc_fopen = reinterpret_cast<FopenFunction>( 64 g_libc_fopen = reinterpret_cast<FopenFunction>(
49 dlsym(RTLD_NEXT, "fopen")); 65 dlsym(RTLD_NEXT, "fopen"));
50 g_libc_fopen64 = reinterpret_cast<FopenFunction>( 66 g_libc_fopen64 = reinterpret_cast<FopenFunction>(
51 dlsym(RTLD_NEXT, "fopen64")); 67 dlsym(RTLD_NEXT, "fopen64"));
52 68
53 if (!g_libc_fopen) { 69 if (!g_libc_fopen) {
54 LOG(FATAL) << "Failed to get fopen() from libc."; 70 LOG(FATAL) << "Failed to get fopen() from libc.";
55 } else if (!g_libc_fopen64) { 71 } else if (!g_libc_fopen64) {
56 #if !defined(OS_OPENBSD) && !defined(OS_FREEBSD) 72 #if !defined(OS_OPENBSD) && !defined(OS_FREEBSD)
57 LOG(WARNING) << "Failed to get fopen64() from libc. Using fopen() instead."; 73 LOG(WARNING) << "Failed to get fopen64() from libc. Using fopen() instead.";
58 #endif // !defined(OS_OPENBSD) && !defined(OS_FREEBSD) 74 #endif // !defined(OS_OPENBSD) && !defined(OS_FREEBSD)
59 g_libc_fopen64 = g_libc_fopen; 75 g_libc_fopen64 = g_libc_fopen;
60 } 76 }
61 77
62 #if defined(LIBC_GLIBC) 78 // Note: we attempt to dlsym both stat and __xstat but only expect one
63 // TODO(sergeyu): This works only on systems with glibc. Fix it to 79 // of the calls to succeed (and similarly for the *64 versions). This
64 // work properly on other systems if necessary. 80 // should work with both glibc and uClibc, and hopefully other libc's.
81 // Background: glibc headers inline stat into __xstat which it exports,
82 // while uClibc exports stat and does not implement __xstat.
83
65 g_libc_xstat = reinterpret_cast<XstatFunction>( 84 g_libc_xstat = reinterpret_cast<XstatFunction>(
66 dlsym(RTLD_NEXT, "__xstat")); 85 dlsym(RTLD_NEXT, "__xstat"));
67 g_libc_xstat64 = reinterpret_cast<Xstat64Function>( 86 g_libc_xstat64 = reinterpret_cast<Xstat64Function>(
68 dlsym(RTLD_NEXT, "__xstat64")); 87 dlsym(RTLD_NEXT, "__xstat64"));
88 g_libc_stat = reinterpret_cast<StatFunction>(
89 dlsym(RTLD_NEXT, "stat"));
90 g_libc_stat64 = reinterpret_cast<Stat64Function>(
91 dlsym(RTLD_NEXT, "stat64"));
92 g_libc_fxstat = reinterpret_cast<FxstatFunction>(
93 dlsym(RTLD_NEXT, "__fxstat"));
94 g_libc_fxstat64 = reinterpret_cast<Fxstat64Function>(
95 dlsym(RTLD_NEXT, "__fxstat64"));
69 96
70 if (!g_libc_xstat) { 97 if (!g_libc_xstat && !g_libc_stat) {
71 LOG(FATAL) << "Failed to get __xstat() from libc."; 98 LOG(FATAL) << "Neither __xstat nor stat found.";
72 } 99 }
73 if (!g_libc_xstat64) { 100 if (!g_libc_xstat64 && !g_libc_stat64) {
74 LOG(WARNING) << "Failed to get __xstat64() from libc."; 101 LOG(FATAL) << "Neither __xstat64 nor stat64 found.";
75 } 102 }
103
104 // Note: it's OK if __fxstat and __fxstat64 aren't found,
105 // we can map them to fstat and fstat64.
jln (very slow on Chromium) 2013/06/25 23:00:03 This makes everything way too complicated. In wha
Mostyn Bramley-Moore 2013/06/25 23:40:41 In practice, probably none. As mentioned in my co
Mostyn Bramley-Moore 2013/06/26 10:30:18 Done (removed the fstat* dlsym's now).
76 } 106 }
77 107
78 // fopen() and fopen64() are intercepted here so that NSS can open 108 // fopen() and fopen64() are intercepted here so that NSS can open
79 // /dev/urandom to seed its random number generator. NSS is used by 109 // /dev/urandom to seed its random number generator. NSS is used by
80 // remoting in the sendbox. 110 // remoting in the sendbox.
81 111
82 // fopen() call may be redirected to fopen64() in stdio.h using 112 // fopen() call may be redirected to fopen64() in stdio.h using
83 // __REDIRECT(), which sets asm name for fopen() to "fopen64". This 113 // __REDIRECT(), which sets asm name for fopen() to "fopen64". This
84 // means that we cannot override fopen() directly here. Instead the 114 // means that we cannot override fopen() directly here. Instead the
85 // the code below defines fopen_override() function with asm name 115 // the code below defines fopen_override() function with asm name
(...skipping 27 matching lines...) Expand all
113 return NULL; 143 return NULL;
114 } 144 }
115 return fdopen(fd, mode); 145 return fdopen(fd, mode);
116 } else { 146 } else {
117 CHECK_EQ(0, pthread_once(&g_libc_file_io_funcs_guard, 147 CHECK_EQ(0, pthread_once(&g_libc_file_io_funcs_guard,
118 InitLibcFileIOFunctions)); 148 InitLibcFileIOFunctions));
119 return g_libc_fopen64(path, mode); 149 return g_libc_fopen64(path, mode);
120 } 150 }
121 } 151 }
122 152
123 // stat() is subject to the same problem as fopen(), so we have to use 153 // The stat() family of functions are subject to the same problem as
124 // the same trick to override it. 154 // fopen(), so we have to use the same trick to override them.
155
125 __attribute__ ((__visibility__("default"))) 156 __attribute__ ((__visibility__("default")))
126 int xstat_override(int version, 157 int xstat_override(int version,
127 const char *path, 158 const char *path,
128 struct stat *buf) __asm__ ("__xstat"); 159 struct stat *buf) __asm__ ("__xstat");
129 160
130 __attribute__ ((__visibility__("default"))) 161 __attribute__ ((__visibility__("default")))
131 int xstat_override(int version, const char *path, struct stat *buf) { 162 int xstat_override(int version, const char *path, struct stat *buf) {
163 CHECK_EQ(0, pthread_once(&g_libc_file_io_funcs_guard,
164 InitLibcFileIOFunctions));
165
132 if (g_override_urandom && strcmp(path, kUrandomDevPath) == 0) { 166 if (g_override_urandom && strcmp(path, kUrandomDevPath) == 0) {
133 int result = __fxstat(version, base::GetUrandomFD(), buf); 167 if (g_libc_fxstat) {
134 return result; 168 int result = g_libc_fxstat(version, base::GetUrandomFD(), buf);
169 return result;
170 } else {
171 int result = fstat(base::GetUrandomFD(), buf);
172 return result;
jln (very slow on Chromium) 2013/06/25 23:00:03 See my above comment, the logic becomes way too co
Mostyn Bramley-Moore 2013/06/25 23:40:41 It should be safe to simply use fstat directly her
Mostyn Bramley-Moore 2013/06/26 10:30:18 Done (reverted).
173 }
174 }
175 else if (!g_libc_xstat) {
176 return g_libc_stat(path, buf);
135 } else { 177 } else {
136 CHECK_EQ(0, pthread_once(&g_libc_file_io_funcs_guard,
137 InitLibcFileIOFunctions));
138 return g_libc_xstat(version, path, buf); 178 return g_libc_xstat(version, path, buf);
139 } 179 }
140 } 180 }
141 181
142 __attribute__ ((__visibility__("default"))) 182 __attribute__ ((__visibility__("default")))
143 int xstat64_override(int version, 183 int xstat64_override(int version,
144 const char *path, 184 const char *path,
145 struct stat64 *buf) __asm__ ("__xstat64"); 185 struct stat64 *buf) __asm__ ("__xstat64");
146 186
147 __attribute__ ((__visibility__("default"))) 187 __attribute__ ((__visibility__("default")))
148 int xstat64_override(int version, const char *path, struct stat64 *buf) { 188 int xstat64_override(int version, const char *path, struct stat64 *buf) {
189 CHECK_EQ(0, pthread_once(&g_libc_file_io_funcs_guard,
190 InitLibcFileIOFunctions));
191
149 if (g_override_urandom && strcmp(path, kUrandomDevPath) == 0) { 192 if (g_override_urandom && strcmp(path, kUrandomDevPath) == 0) {
150 int result = __fxstat64(version, base::GetUrandomFD(), buf); 193 if (g_libc_fxstat64) {
151 return result; 194 int result = g_libc_fxstat64(version, base::GetUrandomFD(), buf);
195 return result;
196 } else {
197 int result = fstat64(base::GetUrandomFD(), buf);
198 return result;
199 }
200 }
201 else if (!g_libc_xstat64) {
202 return g_libc_stat64(path, buf);
152 } else { 203 } else {
153 CHECK_EQ(0, pthread_once(&g_libc_file_io_funcs_guard,
154 InitLibcFileIOFunctions));
155 CHECK(g_libc_xstat64);
156 return g_libc_xstat64(version, path, buf); 204 return g_libc_xstat64(version, path, buf);
157 } 205 }
158 } 206 }
159 #endif // defined(LIBC_GLIBC) 207
208 __attribute__ ((__visibility__("default")))
209 int stat_override(const char *path,
210 struct stat *buf) __asm__ ("stat");
211
212 __attribute__ ((__visibility__("default")))
213 int stat_override(const char *path, struct stat *buf) {
214 if (g_override_urandom && strcmp(path, kUrandomDevPath) == 0) {
215 int result = fstat(base::GetUrandomFD(), buf);
216 return result;
217 }
218
219 CHECK_EQ(0, pthread_once(&g_libc_file_io_funcs_guard,
220 InitLibcFileIOFunctions));
221
222 if (!g_libc_stat) {
223 return g_libc_xstat(XSTAT_VERSION, path, buf);
224 } else {
225 return g_libc_stat(path, buf);
226 }
227 }
228
229 __attribute__ ((__visibility__("default")))
230 int stat64_override(const char *path,
231 struct stat64 *buf) __asm__ ("stat64");
232
233 __attribute__ ((__visibility__("default")))
234 int stat64_override(const char *path, struct stat64 *buf) {
235 if (g_override_urandom && strcmp(path, kUrandomDevPath) == 0) {
236 int result = fstat64(base::GetUrandomFD(), buf);
237 return result;
238 }
239
240 CHECK_EQ(0, pthread_once(&g_libc_file_io_funcs_guard,
241 InitLibcFileIOFunctions));
242
243 if (!g_libc_stat64) {
244 return g_libc_xstat64(XSTAT_VERSION, path, buf);
245 } else {
246 return g_libc_stat64(path, buf);
247 }
248 }
160 249
161 #endif // !defined(ADDRESS_SANITIZER) 250 #endif // !defined(ADDRESS_SANITIZER)
162 251
163 } // namespace content 252 } // namespace content
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