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Diffstat (limited to '')
-rw-r--r-- | security/sandbox/chromium/sandbox/linux/seccomp-bpf/sandbox_bpf.h | 113 |
1 files changed, 113 insertions, 0 deletions
diff --git a/security/sandbox/chromium/sandbox/linux/seccomp-bpf/sandbox_bpf.h b/security/sandbox/chromium/sandbox/linux/seccomp-bpf/sandbox_bpf.h new file mode 100644 index 0000000000..282852992b --- /dev/null +++ b/security/sandbox/chromium/sandbox/linux/seccomp-bpf/sandbox_bpf.h @@ -0,0 +1,113 @@ +// 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. + +#ifndef SANDBOX_LINUX_SECCOMP_BPF_SANDBOX_BPF_H_ +#define SANDBOX_LINUX_SECCOMP_BPF_SANDBOX_BPF_H_ + +#include <stdint.h> + +#include <memory> + +#include "base/files/scoped_file.h" +#include "base/macros.h" +#include "sandbox/linux/bpf_dsl/codegen.h" +#include "sandbox/linux/bpf_dsl/policy.h" +#include "sandbox/sandbox_export.h" + +namespace sandbox { +struct arch_seccomp_data; + +// This class can be used to apply a syscall sandboxing policy expressed in a +// bpf_dsl::Policy object to the current process. +// Syscall sandboxing policies get inherited by subprocesses and, once applied, +// can never be removed for the lifetime of the process. +class SANDBOX_EXPORT SandboxBPF { + public: + enum class SeccompLevel { + SINGLE_THREADED, + MULTI_THREADED, + }; + + // Ownership of |policy| is transfered here to the sandbox object. + // nullptr is allowed for unit tests. + explicit SandboxBPF(std::unique_ptr<bpf_dsl::Policy> policy); + // NOTE: Setting a policy and starting the sandbox is a one-way operation. + // The kernel does not provide any option for unloading a loaded sandbox. The + // sandbox remains engaged even when the object is destructed. + ~SandboxBPF(); + + // Detect if the kernel supports the specified seccomp level. + // See StartSandbox() for a description of these. + static bool SupportsSeccompSandbox(SeccompLevel level); + + // This is the main public entry point. It sets up the resources needed by + // the sandbox, and enters Seccomp mode. + // The calling process must provide a |level| to tell the sandbox which type + // of kernel support it should engage. + // SINGLE_THREADED will only sandbox the calling thread. Since it would be a + // security risk, the sandbox will also check that the current process is + // single threaded and crash if it isn't the case. + // MULTI_THREADED requires more recent kernel support and allows to sandbox + // all the threads of the current process. Be mindful of potential races, + // with other threads using disallowed system calls either before or after + // the sandbox is engaged. + // + // It is possible to stack multiple sandboxes by creating separate "Sandbox" + // objects and calling "StartSandbox()" on each of them. Please note, that + // this requires special care, though, as newly stacked sandboxes can never + // relax restrictions imposed by earlier sandboxes. Furthermore, installing + // a new policy requires making system calls, that might already be + // disallowed. + // Finally, stacking does add more kernel overhead than having a single + // combined policy. So, it should only be used if there are no alternatives. + bool StartSandbox(SeccompLevel level) WARN_UNUSED_RESULT; + + // The sandbox needs to be able to access files in "/proc/self/". If + // this directory is not accessible when "StartSandbox()" gets called, the + // caller must provide an already opened file descriptor by calling + // "SetProcFd()". + // The sandbox becomes the new owner of this file descriptor and will + // close it when "StartSandbox()" executes or when the sandbox object + // disappears. + void SetProcFd(base::ScopedFD proc_fd); + + // Checks whether a particular system call number is valid on the current + // architecture. + static bool IsValidSyscallNumber(int sysnum); + + // UnsafeTraps require some syscalls to always be allowed. + // This helper function returns true for these calls. + static bool IsRequiredForUnsafeTrap(int sysno); + + // From within an UnsafeTrap() it is often useful to be able to execute + // the system call that triggered the trap. The ForwardSyscall() method + // makes this easy. It is more efficient than calling glibc's syscall() + // function, as it avoid the extra round-trip to the signal handler. And + // it automatically does the correct thing to report kernel-style error + // conditions, rather than setting errno. See the comments for TrapFnc for + // details. In other words, the return value from ForwardSyscall() is + // directly suitable as a return value for a trap handler. + static intptr_t ForwardSyscall(const struct arch_seccomp_data& args); + + private: + friend class SandboxBPFTestRunner; + + // Assembles a BPF filter program from the current policy. After calling this + // function, you must not call any other sandboxing function. + CodeGen::Program AssembleFilter(); + + // Assembles and installs a filter based on the policy that has previously + // been configured with SetSandboxPolicy(). + void InstallFilter(bool must_sync_threads); + + base::ScopedFD proc_fd_; + bool sandbox_has_started_; + std::unique_ptr<bpf_dsl::Policy> policy_; + + DISALLOW_COPY_AND_ASSIGN(SandboxBPF); +}; + +} // namespace sandbox + +#endif // SANDBOX_LINUX_SECCOMP_BPF_SANDBOX_BPF_H_ |