Update from chromium 62675d9fb31fb8cedc40f68e78e8445a74f362e7

sandbox/linux/suid/client/setuid_sandbox_client.cc

+// 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/suid/client/setuid_sandbox_client.h"
+
+#include <fcntl.h>
+#include <stdlib.h>
+#include <sys/socket.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+#include "base/command_line.h"
+#include "base/environment.h"
+#include "base/files/file_path.h"
+#include "base/files/file_util.h"
+#include "base/files/scoped_file.h"
+#include "base/logging.h"
+#include "base/macros.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/path_service.h"
+#include "base/posix/eintr_wrapper.h"
+#include "base/process/launch.h"
+#include "base/process/process_metrics.h"
+#include "base/strings/string_number_conversions.h"
+#include "sandbox/linux/services/init_process_reaper.h"
+#include "sandbox/linux/suid/common/sandbox.h"
+#include "sandbox/linux/suid/common/suid_unsafe_environment_variables.h"
+
+namespace {
+
+bool IsFileSystemAccessDenied() {
+  base::ScopedFD self_exe(HANDLE_EINTR(open(base::kProcSelfExe, O_RDONLY)));
+  return !self_exe.is_valid();
+}
+
+// Set an environment variable that reflects the API version we expect from the
+// setuid sandbox. Old versions of the sandbox will ignore this.
+void SetSandboxAPIEnvironmentVariable(base::Environment* env) {
+  env->SetVar(sandbox::kSandboxEnvironmentApiRequest,
+              base::IntToString(sandbox::kSUIDSandboxApiNumber));
+}
+
+// Unset environment variables that are expected to be set by the setuid
+// sandbox. This is to allow nesting of one instance of the SUID sandbox
+// inside another.
+void UnsetExpectedEnvironmentVariables(base::EnvironmentMap* env_map) {
+  DCHECK(env_map);
+  const base::NativeEnvironmentString environment_vars[] = {
+      sandbox::kSandboxDescriptorEnvironmentVarName,
+      sandbox::kSandboxHelperPidEnvironmentVarName,
+      sandbox::kSandboxEnvironmentApiProvides,
+      sandbox::kSandboxPIDNSEnvironmentVarName,
+      sandbox::kSandboxNETNSEnvironmentVarName,
+  };
+
+  for (size_t i = 0; i < arraysize(environment_vars); ++i) {
+    // Setting values in EnvironmentMap to an empty-string will make
+    // sure that they get unset from the environment via AlterEnvironment().
+    (*env_map)[environment_vars[i]] = base::NativeEnvironmentString();
+  }
+}
+
+// Wrapper around a shared C function.
+// Returns the "saved" environment variable name corresponding to |envvar|
+// in a new string or NULL.
+std::string* CreateSavedVariableName(const char* env_var) {
+  char* const saved_env_var = SandboxSavedEnvironmentVariable(env_var);
+  if (!saved_env_var)
+    return NULL;
+  std::string* saved_env_var_copy = new std::string(saved_env_var);
+  // SandboxSavedEnvironmentVariable is the C function that we wrap and uses
+  // malloc() to allocate memory.
+  free(saved_env_var);
+  return saved_env_var_copy;
+}
+
+// The ELF loader will clear many environment variables so we save them to
+// different names here so that the SUID sandbox can resolve them for the
+// renderer.
+void SaveSUIDUnsafeEnvironmentVariables(base::Environment* env) {
+  for (unsigned i = 0; kSUIDUnsafeEnvironmentVariables[i]; ++i) {
+    const char* env_var = kSUIDUnsafeEnvironmentVariables[i];
+    // Get the saved environment variable corresponding to envvar.
+    scoped_ptr<std::string> saved_env_var(CreateSavedVariableName(env_var));
+    if (saved_env_var == NULL)
+      continue;
+
+    std::string value;
+    if (env->GetVar(env_var, &value))
+      env->SetVar(saved_env_var->c_str(), value);
+    else
+      env->UnSetVar(saved_env_var->c_str());
+  }
+}
+
+int GetHelperApi(base::Environment* env) {
+  std::string api_string;
+  int api_number = 0;  // Assume API version 0 if no environment was found.
+  if (env->GetVar(sandbox::kSandboxEnvironmentApiProvides, &api_string) &&
+      !base::StringToInt(api_string, &api_number)) {
+    // It's an error if we could not convert the API number.
+    api_number = -1;
+  }
+  return api_number;
+}
+
+// Convert |var_name| from the environment |env| to an int.
+// Return -1 if the variable does not exist or the value cannot be converted.
+int EnvToInt(base::Environment* env, const char* var_name) {
+  std::string var_string;
+  int var_value = -1;
+  if (env->GetVar(var_name, &var_string) &&
+      !base::StringToInt(var_string, &var_value)) {
+    var_value = -1;
+  }
+  return var_value;
+}
+
+pid_t GetHelperPID(base::Environment* env) {
+  return EnvToInt(env, sandbox::kSandboxHelperPidEnvironmentVarName);
+}
+
+// Get the IPC file descriptor used to communicate with the setuid helper.
+int GetIPCDescriptor(base::Environment* env) {
+  return EnvToInt(env, sandbox::kSandboxDescriptorEnvironmentVarName);
+}
+
+const char* GetDevelSandboxPath() {
+  return getenv("CHROME_DEVEL_SANDBOX");
+}
+
+}  // namespace
+
+namespace sandbox {
+
+SetuidSandboxClient* SetuidSandboxClient::Create() {
+  base::Environment* environment(base::Environment::Create());
+  SetuidSandboxClient* sandbox_client(new SetuidSandboxClient);
+
+  CHECK(environment);
+  sandbox_client->env_ = environment;
+  return sandbox_client;
+}
+
+SetuidSandboxClient::SetuidSandboxClient()
+    : env_(NULL),
+      sandboxed_(false) {
+}
+
+SetuidSandboxClient::~SetuidSandboxClient() {
+  delete env_;
+}
+
+void SetuidSandboxClient::CloseDummyFile() {
+  // When we're launched through the setuid sandbox, SetupLaunchOptions
+  // arranges for kZygoteIdFd to be a dummy file descriptor to satisfy an
+  // ancient setuid sandbox ABI requirement. However, the descriptor is no
+  // longer needed, so we can simply close it right away now.
+  CHECK(IsSuidSandboxChild());
+
+  // Sanity check that kZygoteIdFd refers to a pipe.
+  struct stat st;
+  PCHECK(0 == fstat(kZygoteIdFd, &st));
+  CHECK(S_ISFIFO(st.st_mode));
+
+  PCHECK(0 == IGNORE_EINTR(close(kZygoteIdFd)));
+}
+
+bool SetuidSandboxClient::ChrootMe() {
+  int ipc_fd = GetIPCDescriptor(env_);
+
+  if (ipc_fd < 0) {
+    LOG(ERROR) << "Failed to obtain the sandbox IPC descriptor";
+    return false;
+  }
+
+  if (HANDLE_EINTR(write(ipc_fd, &kMsgChrootMe, 1)) != 1) {
+    PLOG(ERROR) << "Failed to write to chroot pipe";
+    return false;
+  }
+
+  // We need to reap the chroot helper process in any event.
+  pid_t helper_pid = GetHelperPID(env_);
+  // If helper_pid is -1 we wait for any child.
+  if (HANDLE_EINTR(waitpid(helper_pid, NULL, 0)) < 0) {
+    PLOG(ERROR) << "Failed to wait for setuid helper to die";
+    return false;
+  }
+
+  char reply;
+  if (HANDLE_EINTR(read(ipc_fd, &reply, 1)) != 1) {
+    PLOG(ERROR) << "Failed to read from chroot pipe";
+    return false;
+  }
+
+  if (reply != kMsgChrootSuccessful) {
+    LOG(ERROR) << "Error code reply from chroot helper";
+    return false;
+  }
+
+  // We now consider ourselves "fully sandboxed" as far as the
+  // setuid sandbox is concerned.
+  CHECK(IsFileSystemAccessDenied());
+  sandboxed_ = true;
+  return true;
+}
+
+bool SetuidSandboxClient::CreateInitProcessReaper(
+    base::Closure* post_fork_parent_callback) {
+  return sandbox::CreateInitProcessReaper(post_fork_parent_callback);
+}
+
+bool SetuidSandboxClient::IsSuidSandboxUpToDate() const {
+  return GetHelperApi(env_) == kSUIDSandboxApiNumber;
+}
+
+bool SetuidSandboxClient::IsSuidSandboxChild() const {
+  return GetIPCDescriptor(env_) >= 0;
+}
+
+bool SetuidSandboxClient::IsInNewPIDNamespace() const {
+  return env_->HasVar(kSandboxPIDNSEnvironmentVarName);
+}
+
+bool SetuidSandboxClient::IsInNewNETNamespace() const {
+  return env_->HasVar(kSandboxNETNSEnvironmentVarName);
+}
+
+bool SetuidSandboxClient::IsSandboxed() const {
+  return sandboxed_;
+}
+
+// Check if CHROME_DEVEL_SANDBOX is set but empty. This currently disables
+// the setuid sandbox. TODO(jln): fix this (crbug.com/245376).
+bool SetuidSandboxClient::IsDisabledViaEnvironment() {
+  const char* devel_sandbox_path = GetDevelSandboxPath();
+  if (devel_sandbox_path && '\0' == *devel_sandbox_path) {
+    return true;
+  }
+  return false;
+}
+
+base::FilePath SetuidSandboxClient::GetSandboxBinaryPath() {
+  base::FilePath sandbox_binary;
+  base::FilePath exe_dir;
+  if (PathService::Get(base::DIR_EXE, &exe_dir)) {
+    base::FilePath sandbox_candidate = exe_dir.AppendASCII("chrome-sandbox");
+    if (base::PathExists(sandbox_candidate))
+      sandbox_binary = sandbox_candidate;
+  }
+
+  // In user-managed builds, including development builds, an environment
+  // variable is required to enable the sandbox. See
+  // http://code.google.com/p/chromium/wiki/LinuxSUIDSandboxDevelopment
+  struct stat st;
+  if (sandbox_binary.empty() && stat(base::kProcSelfExe, &st) == 0 &&
+      st.st_uid == getuid()) {
+    const char* devel_sandbox_path = GetDevelSandboxPath();
+    if (devel_sandbox_path) {
+      sandbox_binary = base::FilePath(devel_sandbox_path);
+    }
+  }
+
+  return sandbox_binary;
+}
+
+void SetuidSandboxClient::PrependWrapper(base::CommandLine* cmd_line) {
+  std::string sandbox_binary(GetSandboxBinaryPath().value());
+  struct stat st;
+  if (sandbox_binary.empty() || stat(sandbox_binary.c_str(), &st) != 0) {
+    LOG(FATAL) << "The SUID sandbox helper binary is missing: "
+               << sandbox_binary << " Aborting now. See "
+                                    "https://code.google.com/p/chromium/wiki/"
+                                    "LinuxSUIDSandboxDevelopment.";
+  }
+
+  if (access(sandbox_binary.c_str(), X_OK) != 0 || (st.st_uid != 0) ||
+      ((st.st_mode & S_ISUID) == 0) || ((st.st_mode & S_IXOTH)) == 0) {
+    LOG(FATAL) << "The SUID sandbox helper binary was found, but is not "
+                  "configured correctly. Rather than run without sandboxing "
+                  "I'm aborting now. You need to make sure that "
+               << sandbox_binary << " is owned by root and has mode 4755.";
+  }
+
+  cmd_line->PrependWrapper(sandbox_binary);
+}
+
+void SetuidSandboxClient::SetupLaunchOptions(
+    base::LaunchOptions* options,
+    base::FileHandleMappingVector* fds_to_remap,
+    base::ScopedFD* dummy_fd) {
+  DCHECK(options);
+  DCHECK(fds_to_remap);
+
+  // Launching a setuid binary requires PR_SET_NO_NEW_PRIVS to not be used.
+  options->allow_new_privs = true;
+  UnsetExpectedEnvironmentVariables(&options->environ);
+
+  // Set dummy_fd to the reading end of a closed pipe.
+  int pipe_fds[2];
+  PCHECK(0 == pipe(pipe_fds));
+  PCHECK(0 == IGNORE_EINTR(close(pipe_fds[1])));
+  dummy_fd->reset(pipe_fds[0]);
+
+  // We no longer need a dummy socket for discovering the child's PID,
+  // but the sandbox is still hard-coded to expect a file descriptor at
+  // kZygoteIdFd. Fixing this requires a sandbox API change. :(
+  fds_to_remap->push_back(std::make_pair(dummy_fd->get(), kZygoteIdFd));
+}
+
+void SetuidSandboxClient::SetupLaunchEnvironment() {
+  SaveSUIDUnsafeEnvironmentVariables(env_);
+  SetSandboxAPIEnvironmentVariable(env_);
+}
+
+}  // namespace sandbox