| // Copyright (c) 2012 The Chromium Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| #include "sandbox/linux/services/libc_urandom_override.h" |
| |
| #include <dlfcn.h> |
| #include <pthread.h> |
| #include <stdio.h> |
| #include <sys/stat.h> |
| #include <unistd.h> |
| |
| #include "base/logging.h" |
| #include "base/posix/eintr_wrapper.h" |
| #include "base/rand_util.h" |
| |
| // Note: this file is used by the zygote and nacl_helper. |
| |
| #if !defined(HAVE_XSTAT) && defined(LIBC_GLIBC) |
| #define HAVE_XSTAT 1 |
| #endif |
| |
| namespace sandbox { |
| |
| static bool g_override_urandom = false; |
| |
| // TODO(sergeyu): Currently InitLibcUrandomOverrides() doesn't work properly |
| // under ASan or MSan - it crashes content_unittests. Make sure it works |
| // properly and enable it here. http://crbug.com/123263 |
| #if !(defined(ADDRESS_SANITIZER) || defined(MEMORY_SANITIZER)) |
| static void InitLibcFileIOFunctions(); |
| static pthread_once_t g_libc_file_io_funcs_guard = PTHREAD_ONCE_INIT; |
| #endif |
| |
| void InitLibcUrandomOverrides() { |
| // Make sure /dev/urandom is open. |
| base::GetUrandomFD(); |
| g_override_urandom = true; |
| |
| #if !(defined(ADDRESS_SANITIZER) || defined(MEMORY_SANITIZER)) |
| CHECK_EQ(0, pthread_once(&g_libc_file_io_funcs_guard, |
| InitLibcFileIOFunctions)); |
| #endif |
| } |
| |
| #if !(defined(ADDRESS_SANITIZER) || defined(MEMORY_SANITIZER)) |
| |
| static const char kUrandomDevPath[] = "/dev/urandom"; |
| |
| typedef FILE* (*FopenFunction)(const char* path, const char* mode); |
| |
| static FopenFunction g_libc_fopen = NULL; |
| static FopenFunction g_libc_fopen64 = NULL; |
| |
| #if HAVE_XSTAT |
| typedef int (*XstatFunction)(int version, const char *path, struct stat *buf); |
| typedef int (*Xstat64Function)(int version, const char *path, |
| struct stat64 *buf); |
| |
| static XstatFunction g_libc_xstat = NULL; |
| static Xstat64Function g_libc_xstat64 = NULL; |
| #else |
| typedef int (*StatFunction)(const char *path, struct stat *buf); |
| typedef int (*Stat64Function)(const char *path, struct stat64 *buf); |
| |
| static StatFunction g_libc_stat = NULL; |
| static Stat64Function g_libc_stat64 = NULL; |
| #endif // HAVE_XSTAT |
| |
| // Find the libc's real fopen* and *stat* functions. This should only be |
| // called once, and should be guarded by g_libc_file_io_funcs_guard. |
| static void InitLibcFileIOFunctions() { |
| g_libc_fopen = reinterpret_cast<FopenFunction>( |
| dlsym(RTLD_NEXT, "fopen")); |
| g_libc_fopen64 = reinterpret_cast<FopenFunction>( |
| dlsym(RTLD_NEXT, "fopen64")); |
| |
| if (!g_libc_fopen) { |
| LOG(FATAL) << "Failed to get fopen() from libc."; |
| } else if (!g_libc_fopen64) { |
| #if !defined(OS_OPENBSD) && !defined(OS_FREEBSD) |
| LOG(WARNING) << "Failed to get fopen64() from libc. Using fopen() instead."; |
| #endif // !defined(OS_OPENBSD) && !defined(OS_FREEBSD) |
| g_libc_fopen64 = g_libc_fopen; |
| } |
| |
| #if HAVE_XSTAT |
| g_libc_xstat = reinterpret_cast<XstatFunction>( |
| dlsym(RTLD_NEXT, "__xstat")); |
| g_libc_xstat64 = reinterpret_cast<Xstat64Function>( |
| dlsym(RTLD_NEXT, "__xstat64")); |
| |
| if (!g_libc_xstat) { |
| LOG(FATAL) << "Failed to get __xstat() from libc."; |
| } |
| if (!g_libc_xstat64) { |
| LOG(FATAL) << "Failed to get __xstat64() from libc."; |
| } |
| #else |
| g_libc_stat = reinterpret_cast<StatFunction>( |
| dlsym(RTLD_NEXT, "stat")); |
| g_libc_stat64 = reinterpret_cast<Stat64Function>( |
| dlsym(RTLD_NEXT, "stat64")); |
| |
| if (!g_libc_stat) { |
| LOG(FATAL) << "Failed to get stat() from libc."; |
| } |
| if (!g_libc_stat64) { |
| LOG(FATAL) << "Failed to get stat64() from libc."; |
| } |
| #endif // HAVE_XSTAT |
| } |
| |
| // fopen() and fopen64() are intercepted here so that NSS can open |
| // /dev/urandom to seed its random number generator. NSS is used by |
| // remoting in the sendbox. |
| |
| // fopen() call may be redirected to fopen64() in stdio.h using |
| // __REDIRECT(), which sets asm name for fopen() to "fopen64". This |
| // means that we cannot override fopen() directly here. Instead the |
| // the code below defines fopen_override() function with asm name |
| // "fopen", so that all references to fopen() will resolve to this |
| // function. |
| __attribute__ ((__visibility__("default"))) |
| FILE* fopen_override(const char* path, const char* mode) __asm__ ("fopen"); |
| |
| __attribute__ ((__visibility__("default"))) |
| FILE* fopen_override(const char* path, const char* mode) { |
| if (g_override_urandom && strcmp(path, kUrandomDevPath) == 0) { |
| int fd = HANDLE_EINTR(dup(base::GetUrandomFD())); |
| if (fd < 0) { |
| PLOG(ERROR) << "dup() failed."; |
| return NULL; |
| } |
| return fdopen(fd, mode); |
| } else { |
| CHECK_EQ(0, pthread_once(&g_libc_file_io_funcs_guard, |
| InitLibcFileIOFunctions)); |
| return g_libc_fopen(path, mode); |
| } |
| } |
| |
| __attribute__ ((__visibility__("default"))) |
| FILE* fopen64(const char* path, const char* mode) { |
| if (g_override_urandom && strcmp(path, kUrandomDevPath) == 0) { |
| int fd = HANDLE_EINTR(dup(base::GetUrandomFD())); |
| if (fd < 0) { |
| PLOG(ERROR) << "dup() failed."; |
| return NULL; |
| } |
| return fdopen(fd, mode); |
| } else { |
| CHECK_EQ(0, pthread_once(&g_libc_file_io_funcs_guard, |
| InitLibcFileIOFunctions)); |
| return g_libc_fopen64(path, mode); |
| } |
| } |
| |
| // The stat() family of functions are subject to the same problem as |
| // fopen(), so we have to use the same trick to override them. |
| |
| #if HAVE_XSTAT |
| |
| __attribute__ ((__visibility__("default"))) |
| int xstat_override(int version, |
| const char *path, |
| struct stat *buf) __asm__ ("__xstat"); |
| |
| __attribute__ ((__visibility__("default"))) |
| int xstat_override(int version, const char *path, struct stat *buf) { |
| if (g_override_urandom && strcmp(path, kUrandomDevPath) == 0) { |
| int result = __fxstat(version, base::GetUrandomFD(), buf); |
| return result; |
| } else { |
| CHECK_EQ(0, pthread_once(&g_libc_file_io_funcs_guard, |
| InitLibcFileIOFunctions)); |
| return g_libc_xstat(version, path, buf); |
| } |
| } |
| |
| __attribute__ ((__visibility__("default"))) |
| int xstat64_override(int version, |
| const char *path, |
| struct stat64 *buf) __asm__ ("__xstat64"); |
| |
| __attribute__ ((__visibility__("default"))) |
| int xstat64_override(int version, const char *path, struct stat64 *buf) { |
| if (g_override_urandom && strcmp(path, kUrandomDevPath) == 0) { |
| int result = __fxstat64(version, base::GetUrandomFD(), buf); |
| return result; |
| } else { |
| CHECK_EQ(0, pthread_once(&g_libc_file_io_funcs_guard, |
| InitLibcFileIOFunctions)); |
| return g_libc_xstat64(version, path, buf); |
| } |
| } |
| |
| #else |
| |
| __attribute__ ((__visibility__("default"))) |
| int stat_override(const char *path, |
| struct stat *buf) __asm__ ("stat"); |
| |
| __attribute__ ((__visibility__("default"))) |
| int stat_override(const char *path, struct stat *buf) { |
| if (g_override_urandom && strcmp(path, kUrandomDevPath) == 0) { |
| int result = fstat(base::GetUrandomFD(), buf); |
| return result; |
| } else { |
| CHECK_EQ(0, pthread_once(&g_libc_file_io_funcs_guard, |
| InitLibcFileIOFunctions)); |
| return g_libc_stat(path, buf); |
| } |
| } |
| |
| __attribute__ ((__visibility__("default"))) |
| int stat64_override(const char *path, |
| struct stat64 *buf) __asm__ ("stat64"); |
| |
| __attribute__ ((__visibility__("default"))) |
| int stat64_override(const char *path, struct stat64 *buf) { |
| if (g_override_urandom && strcmp(path, kUrandomDevPath) == 0) { |
| int result = fstat64(base::GetUrandomFD(), buf); |
| return result; |
| } else { |
| CHECK_EQ(0, pthread_once(&g_libc_file_io_funcs_guard, |
| InitLibcFileIOFunctions)); |
| return g_libc_stat64(path, buf); |
| } |
| } |
| |
| #endif // HAVE_XSTAT |
| |
| #endif // !(defined(ADDRESS_SANITIZER) || defined(MEMORY_SANITIZER)) |
| |
| } // namespace content |