More robust parsing for ATSC PSIP tables (proposal) #624
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When parsing any of the variable length portions of any of the ATSC PSIP tables, ensure that the parsing never reads past the end of the packet. Knowing the number of entries in the table up front also allows for preallocating all the space needed for the m_ptr array up front, instead of std::vector making multiple allocation requests as the vector size grows. Add error counters that are printed when a recording is stopped.
1) SpliceInformationTable::Parse handing for a splice_insert (that isn't a cancel) needs to set m_epilog. 2) Return proper length from SpliceTimeView::size. 3) SpliceInsertView::IsSpliceImmediate needs to check the proper bit. 4) Add accessor functions to SpliceInsertView to retrieve component information. 5) SpliceInformationTable::SpliceDescriptorsLength doesn't need an argument. 6) SpliceInformationTable::SpliceDescriptors should return nullptr if m_epilog is set but the descriptor count is zero. 7) Add test cases.
1) Correct the values pushed into slice (m_ptrs1) array. 2) Update the working pointer after each entry in the splice table is processed, so the next slice is processed. (Old code processed the first slice n times.) 3) Add test cases.
When parsing any of the variable length portions of any of the SCTE Splice, ensure that the parsing never reads past the end of the packet. Knowing the number of entries in the table up front also allows for preallocating all the space needed up front, instead of std::vector making multiple allocation requests as the vector size grows.
When parsing any of the variable length portions of any of the PMT, ensure that the parsing never reads past the end of the packet. Knowing the number of entries in the table up front also allows for preallocating all the space needed up front, instead of std::vector making multiple allocation requests as the vector size grows. The PMT parse checks have to be conditional because MythTV generates blank PMT packets and then fills them in with data.
When parsing any of the variable length portions of any of these tables, ensure that the parsing never reads past the end of the packet. Knowing the number of entries in the table up front also allows for preallocating all the space needed up front, instead of std::vector making multiple allocation requests as the vector size grows.
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This is my current set of proposed changes to validate all ATSC PSIP tables instead of blindly trusting their data. The table parsing functions have been enhanced to do the following:
I have also added a number of compile time parsing tests for the ATSC parsers.
The following pieces of code will be removed before commit: