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Bound 'B' aux array element count in ParseAuxFields (heap OOB read) #1083

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Bound 'B' aux array element count in ParseAuxFields (heap OOB read) #1083

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9 changes: 9 additions & 0 deletions third_party/nucleus/io/sam_reader.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -372,6 +372,15 @@ ::nucleus::Status ParseAuxFields(const bam1_t* b,
// We need to skip 4 bytes for n_elements int that occurs before the
// array.
s += 4;
// Reject an element count that would walk past the end of the
// record. Every scalar aux branch above already bounds-checks; the
// 'B' array branch must too. Compute in 64-bit: n_elements is read as
// a uint32 into an int, so a value >= 2^31 is itself negative.
if (n_elements < 0 ||
static_cast<int64_t>(n_elements) * element_size > (end - s)) {
return ::nucleus::DataLoss("B-array length exceeds record for tag " +
tag);
}
if (sub_type == 'c') {
std::vector<int8_t> all_values;
for (int i = 0; i < n_elements; i++) {
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