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[SharedCache] Avoid reading header fields outside of the header for iOS 10 and older #6777

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[SharedCache] Avoid reading header fields outside of the header for iOS 10 and older #6777

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16 changes: 13 additions & 3 deletions view/sharedcache/core/SharedCacheView.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -175,9 +175,6 @@ bool SharedCacheView::Init()

m_logger = new Logger("SharedCache.View", GetFile()->GetSessionId());

uint32_t platform;
// NOTE: This entry only exists on ios 11 and later, older versions will just assume iOS.
GetParentView()->Read(&platform, 0xd8, 4);
char magic[17];
GetParentView()->Read(&magic, 0, 16);
magic[16] = 0;
Expand All @@ -197,6 +194,19 @@ bool SharedCacheView::Init()
return false;
}

// Use the value of mappingOffset as an upper bound for the size of the
// header to avoid misinterpreting bytes outside of the header.
uint32_t mappingOffset;
GetParentView()->Read(&mappingOffset, 0x10, 4);

uint32_t platform;
if (mappingOffset >= 0xd8 + 4) {
GetParentView()->Read(&platform, 0xd8, 4);
} else {
m_logger->LogWarn("Old header without platform field: Defaulting to iOS");
platform = DSCPlatformiOS;
}

// TODO: Do we want to add any warnings about platform support here?
// TODO: Do we still consider macos experimental?
switch (platform)
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