swiftlang/swift

[SR-3343] Investigate Array Canaries for withUnsafe operations

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#45,931 建立於 2016年12月6日

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diagnostics qualitygood first issueimprovementstandard library

描述
Previous ID SR-3343
Radar rdar://problem/16553648
Original Reporter Gankro (JIRA User)
Type Improvement
Votes 0
Component/s Standard Library
Labels Improvement, DiagnosticsQoI, StarterBug
Assignee abdullah (JIRA)
Priority Medium

md5: c68651c162da6db48a6cc867e161ffe0

Issue Description:

We provide several operations which expose the guts of an Array as an UnsafePointer in a closure. This provides an opportunity for developers to mess up and scribble past the bounds of the Array. As a QoI feature, we should look into opportunistically installing a canary at the end of the Array in debug builds.

Basic idea:

  • At the start of withUnsafeBufferPointer (before the closure is called), check if the array has some slack capacity.

  • If it does, write some specific bit pattern to the extra space (just the last byte?).

  • At the end of withUnsafeBufferPointer (after the closure has been called), check if the bit pattern is in tact. If not, assert that a buffer overflow occurred.

This obviously isn't a robust protection against buffer overflows, but maybe it will catch some programmer errors!

I'm happy to mentor anyone who wishes to work on this.

貢獻者指南

技術棧
swift
領域
developer experiencesecurity
議題類型
feature
難度面向新貢獻者的預計實作難度，1 表示很小改動，5 表示專家級工作。
3
預計時間有經驗貢獻者完成調查、實作、測試並準備 pull request 的粗略時間範圍。
half day
活動狀態議題目前的可參與程度：新鮮、活躍、陳舊、阻塞或等待維護者輸入。
stale
清晰度議題是否清楚說明預期改動、驗收標準和下一步。
clear
前置要求
Swift basicsArray internalsUnsafePointer
新手友善度1-100 的估計分數，表示該議題對首次貢獻者的友善程度。
70
研究方向
The issue suggests implementing canary values in Array.withUnsafeBufferPointer to detect buffer overflows. Start by examining the source file stdlib/public/core/Array.swift for the current implementation of withUnsafeBufferPointer. Add code to check for slack capacity and write a canary pattern (e.g., 0xDEADBEEF) before the closure, then verify after. Use #if DEBUG to limit to debug builds. Test by intentionally writing past bounds to trigger the assertion.
[SR-3343] Investigate Array Canaries for withUnsafe operations · swiftlang/swift#45931 | Good First Issue