| // 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/file_util.h" |
| #include "base/files/file_path.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 |