Refactor the setuid sandbox client code to its own class.

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 <sys/types.h>
+#include <sys/wait.h>
+
+#include "base/eintr_wrapper.h"
+#include "base/environment.h"
+#include "base/logging.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/string_number_conversions.h"
+
+#include "sandbox/linux/suid/common/sandbox.h"
+#include "sandbox/linux/suid/common/suid_unsafe_environment_variables.h"
+#include "setuid_sandbox_client.h"
+
+namespace {
+
+// 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));
+}
+
+// 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* envvar) {
+  char* const saved_env_var = SandboxSavedEnvironmentVariable(envvar);
+  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* const 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);
+}
+
+}  // 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;
+}
+
+SetuidSandboxClient::~SetuidSandboxClient() {
+  delete env_;
+}
+
+bool SetuidSandboxClient::ChrootMe() {
+  int fd = GetIPCDescriptor(env_);
+
+  if (fd < 0) {
+    LOG(ERROR) << "Failed to obtain the sandbox IPC descriptor";
+    return false;
+  }
+
+  if (HANDLE_EINTR(write(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 (waitpid(helper_pid, NULL, 0) < 0) {
+    PLOG(ERROR) << "Failed to wait for setuid helper to die";
+    return false;
+  }
+
+  char reply;
+  if (HANDLE_EINTR(read(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;
+  }
+  return true;
+}
+
+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);
+}
+
+void SetuidSandboxClient::SetupLaunchEnvironment() {
+  SaveSUIDUnsafeEnvironmentVariables(env_);
+  SetSandboxAPIEnvironmentVariable(env_);
+}
+
+}  // namespace sandbox