"ELF Number of sections >= SHN_LORESERVE (0xff00)" is not implemented in library

[mocakturk]

Hello,

Thx for this library.
I noticed an exception when reading an ELF file:
System.ArgumentOutOfRangeException: Specified argument was out of the range of valid values.
Parameter name: index
at ELFSharp.ELF.ELF1.ReadSectionHeader(Int32 index) at ELFSharp.ELF.ELF1.ReadStringTable()
at ELFSharp.ELF.ELF`1..ctor(String fileName)
at ELFSharp.ELF.ELFReader.TryLoad(String fileName, IELF& elf)
at ELFSharp.ELF.ELFReader.Load(String fileName)

e_shnum (number of entries in the section header table) is 0. Then, library tries to read section index = 1... That causes exception.

After some googling, I found below:
If the number of sections is greater than or equal to SHN_LORESERVE (0xff00), this member has the value zero and the actual number of section header table entries is contained in the sh_size field of the section header at index 0. (Otherwise, the sh_size member of the initial entry contains 0.)

I believe, if the above description is implemented, the problem will be solved.

Thx,
Murat

[mocakturk]

I changed the code myself. Issue solved.
Here my modifications:

• I changed type of "sectionHeaderEntryCount" to "uint".
• Then I added below check after reading "sectionHeaderEntryCount".

sectionHeaderEntryCount = reader.ReadUInt16();
            // If the number of sections is greater than or equal to SHN_LORESERVE (0xff00), this member has the
            // value zero and the actual number of section header table entries is contained in the sh_size field
            // of the section header at index 0. (Otherwise, the sh_size member of the initial entry contains 0.)
            if (sectionHeaderEntryCount == 0)
            {
                var tempPosition = reader.BaseStream.Position;
                reader.BaseStream.Seek(
                    sectionHeaderOffset + 0 * sectionHeaderEntrySize + (Class==Class.Bit32?0x14:0x20),
                    SeekOrigin.Begin
                );
                var sh_size = Class == Class.Bit32 ? reader.ReadUInt32() : reader.ReadUInt64();
                sectionHeaderEntryCount = (uint) sh_size;
                reader.BaseStream.Seek(tempPosition, SeekOrigin.Begin);
            }```

[konrad-kruczynski]

Thanks for the input, I'll try to implement your solution. Would it be possible for you to provide a test binary?

[mocakturk]

Hi Konrad,

Thanks for the update. However, this solution does not work. Because you inserted (sectionHeaderEntryCount == 0) case into ReadSections method. However, exception occurs inside "ReadStringTable" method. (Reading string table also reads a section)

When I put "(sectionHeaderEntryCount == 0)" case to the end of "ReadFields" method, it works.
Just move lines 231-238 into the end of "ReadFields" method.

Sorry, but I cannot provide you the binary. First, it is very big (0.5GB). Second, it is a software of my company.
Just let me know for testing...

Thanks for the effort...

[konrad-kruczynski]

Right. Please check version 2.15.2.

[mocakturk]

Konrad, v2.15.2 works good. Thank you.