Learning Linux Binary Analysis

Checking the dynamic segment for DLL injection traces

Recall from Chapter 2, The ELF Binary Format, that the dynamic segment can be found in the program header table and is of type PT_DYNAMIC. There is also a .dynamic section that also points to the dynamic segment.

The dynamic segment is an array of ElfN_Dyn structs that contains d_tag and a corresponding value that exists in a union:

     typedef struct {
               ElfN_Sxword    d_tag;
               union {
                   ElfN_Xword d_val;
                   ElfN_Addr  d_ptr;
               } d_un;
           } ElfN_Dyn;

Using readelf we can easily view the dynamic segment of a file.

Following is an example of a legitimate dynamic segment:

$ readelf -d ./test

Dynamic section at offset 0xe28 contains 24 entries:
  Tag        Type                         Name/Value
 0x0000000000000001 (NEEDED) Shared library: [libc.so.6] ...