8a1b40c608
Variable-length arrays are not part of the C++ standard, and are dangerous to use because they allocate a potentially-unbounded amount of data on the stack. In addition, they trigger a clang warning (-Wvla-extension) which is currently suppressed in Chromium builds. This patch prevents the use of VLAs in launch_posix.cc and credentials.cc by hardcoding a compile-time constant value for use when PTHREAD_STACK_MIN when is not constant already. This allows the sandbox code to remain async-signal-safe by allocating on the stack without using VLAs. To ensure the hardcoded value is large enough, we run a CHECK during initialization. We use the initializer of an otherwise-unused global variable to do so. Bug: 349656479 Change-Id: I5f5661464e77bac36456d0b72530a0fba60a55bc Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5783847 Reviewed-by: Matthew Denton <mpdenton@chromium.org> Reviewed-by: Mark Mentovai <mark@chromium.org> Commit-Queue: Devon Loehr <dloehr@google.com> Reviewed-by: Ken Rockot <rockot@google.com> Cr-Commit-Position: refs/heads/main@{#1352736}
Sandbox Library
This directory contains platform-specific sandboxing libraries. Sandboxing is a technique that can improve the security of an application by separating untrustworthy code (or code that handles untrustworthy data) and restricting its privileges and capabilities.
Each platform relies on the operating system's process primitive to isolate code into distinct security principals, and platform-specific technologies are used to implement the privilege reduction. At a high-level:
mac/uses the Seatbelt sandbox. See the detailed design for more.linux/uses namespaces and Seccomp-BPF. See the detailed design for more.win/uses a combination of restricted tokens, distinct job objects, alternate desktops, and integrity levels. See the detailed design for more.
Built on top of the low-level sandboxing library is the
//sandbox/policy component, which provides concrete
policies and helper utilities for sandboxing specific Chromium processes and
services. The core sandbox library cannot depend on the policy component.