[SR-3343] Investigate Array Canaries for withUnsafe operations
#45,931 opened on Dec 6, 2016
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Description
| 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:
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At the start of withUnsafeBufferPointer (before the closure is called), check if the array has some slack capacity.
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If it does, write some specific bit pattern to the extra space (just the last byte?).
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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.