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Fix attr read overflows #36003

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merged 4 commits into from
Mar 5, 2025
Merged

Fix attr read overflows #36003

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5cac4ae
Prevent Buffer Overflows with External Attribute Reads
witowsg-amazon Oct 9, 2024
c333b8e
Fix style + minor compile issues
witowsg-amazon Oct 9, 2024
465f21f
Fix include order
witowsg-amazon Oct 9, 2024
d263b42
Address PR Comments
witowsg-amazon Oct 10, 2024
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43 changes: 39 additions & 4 deletions src/app/util/attribute-storage.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -24,6 +24,7 @@
#include <app/InteractionModelEngine.h>
#include <app/reporting/reporting.h>
#include <app/util/config.h>
#include <app/util/ember-io-storage.h>
#include <app/util/ember-strings.h>
#include <app/util/endpoint-config-api.h>
#include <app/util/generic-callbacks.h>
Expand Down Expand Up @@ -292,6 +293,30 @@ CHIP_ERROR emberAfSetDynamicEndpoint(uint16_t index, EndpointId id, const EmberA
}
}

const size_t bufferSize = Compatibility::Internal::gEmberAttributeIOBufferSpan.size();
for (uint8_t i = 0; i < ep->clusterCount; i++)
{
const EmberAfCluster * cluster = &(ep->cluster[i]);
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Could also do:

Suggested change
const EmberAfCluster * cluster = &(ep->cluster[i]);
const EmberAfCluster & cluster = ep->cluster[i];

but either way.

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I'm going to leave the pointer-style since the structure is ultimately storing pointers -- in hindsight I probably should have done ep->cluster + i to just access the pointer directly.

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For what it's worth, the structure is not in fact storing pointers. It's storing EmberAfCluster objects.

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@witowsg-amazon

if (!cluster->attributes)
{
continue;
}

for (uint16_t j = 0; j < cluster->attributeCount; j++)
{
const EmberAfAttributeMetadata * attr = &(cluster->attributes[j]);
uint16_t attrSize = emberAfAttributeSize(attr);
if (attrSize > bufferSize)
{
ChipLogError(DataManagement,
"Attribute size %u exceeds max size %lu, (attrId=" ChipLogFormatMEI ", clusterId=" ChipLogFormatMEI
")",
attrSize, static_cast<unsigned long>(bufferSize), ChipLogValueMEI(attr->attributeId),
ChipLogValueMEI(cluster->clusterId));
return CHIP_ERROR_NO_MEMORY;
}
}
}
emAfEndpoints[index].endpoint = id;
emAfEndpoints[index].deviceTypeList = deviceTypeList;
emAfEndpoints[index].endpointType = ep;
Expand Down Expand Up @@ -642,10 +667,20 @@ Status emAfReadOrWriteAttribute(const EmberAfAttributeSearchRecord * attRecord,
// Is the attribute externally stored?
if (am->mask & MATTER_ATTRIBUTE_FLAG_EXTERNAL_STORAGE)
{
return (write ? emberAfExternalAttributeWriteCallback(attRecord->endpoint, attRecord->clusterId,
am, buffer)
: emberAfExternalAttributeReadCallback(attRecord->endpoint, attRecord->clusterId,
am, buffer, emberAfAttributeSize(am)));
if (write)
{
return emberAfExternalAttributeWriteCallback(attRecord->endpoint, attRecord->clusterId, am,
buffer);
}

if (readLength < emberAfAttributeSize(am))
{
// Prevent a potential buffer overflow
return Status::ResourceExhausted;
}

return emberAfExternalAttributeReadCallback(attRecord->endpoint, attRecord->clusterId, am,
buffer, emberAfAttributeSize(am));
}

// Internal storage is only supported for fixed endpoints
Expand Down
3 changes: 2 additions & 1 deletion src/controller/tests/TestServerCommandDispatch.cpp
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Expand Up @@ -215,7 +215,8 @@ TEST_F(TestServerCommandDispatch, TestNoHandler)
EXPECT_EQ(GetExchangeManager().GetNumActiveExchanges(), 0u);
}

static const int kDescriptorAttributeArraySize = 254;
// Use 8 so that we don't exceed the size of ATTRIBUTE_LARGEST defined by ZAP
static const int kDescriptorAttributeArraySize = 8;

// Declare Descriptor cluster attributes
DECLARE_DYNAMIC_ATTRIBUTE_LIST_BEGIN(descriptorAttrs)
Expand Down
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