README.md

Backward ldd

All ELF files contain data about libraries used by the program, therefore such as ldd, readelf etc. bash commands exist, which parse an ELF dynamic table to find used shared libraries.
The bldd works with directories and collects the readelf command output to make a list of all lib names and files used a lib and the machine architecture from an ELF file header.

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Usage example:

Input: Non-recursive option

./bldd .

Output:

---------- x86_64 ----------
  libgcc_s.so.1 (1 executables) ->
    ./bldd

  libc.so.6 (1 executables) ->
    ./bldd

  ld-linux-x86-64.so.2 (1 executables) ->
    ./bldd

Input: Recursive option:

./bldd -r .

Output:

---------- x86_64 ----------
  libgcc_s.so.1 (34 executables) ->
    ./bldd
    ./build/num-traits-cfc12ef6a2206e39/buildk-script-build
    ./build/num-traits-cfc12ef6a2206e39/build_script_build-cfc12ef6a2206e39
    ./build/libc-61aecf2398dbde23/build_script_build-61aecf2398dbde23
    ./build/libc-61aecf2398dbde23/build-script-build
    ./build/proc-macro-error-attr-8dda783b6edd3f20/build-script-build
    .......
  libc.so.6 (34 executables) ->
    ./bldd
    ./build/num-traits-cfc12ef6a2206e39/build-script-build
    ./build/num-traits-cfc12ef6a2206e39/build_script_build-cfc12ef6a2206e39
    ./build/libc-61aecf2398dbde23/build_script_build-61aecf2398dbde23
    ./build/libc-61aecf2398dbde23/build-script-build
    ./build/proc-macro-error-attr-8dda783b6edd3f20/build-script-build
    .......

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The code explanation:

Used libraries:

elf_rs - used to get the version of machine architecture from ELF files (I'm lazy to describe mapping from hex to string for all of them, but I added in here around 5 of not so popular architectures) std::process - used to run realdelf command for each of files in a directory

So, my solution includes both ways of lazy ELF files parsing - via command and via libraries. Structures:

• Cli The structure used for command line argument parsing made via clap library

#[derive(Parser)]
#[clap(author="Anastasiia Stepanova <[email protected]>", version, about="Search for libraries in a directory ELF files and display all found dependencies on libraries in a directory.")]
struct Cli {
    /// The path to the directory to read
    path: String,

    /// Recursive traversal of directory
    #[arg(
        short, long)]
    recursive: bool,
}

• CollectorEntry Used by the collect_lib function as a datatype for entries of result vector.

#[derive(Debug, Clone)]
struct CollectorEntry {
    file_path: String,
    lib_name: String,
    machine_arc: ElfMachine,
}

Functions:

• get_architecture: Obviously just asks to elf_rs lib to parse the file via Elf::from_bytes

fn get_architecture(file_name: &String, directory: &String) -> ElfMachine

• scan_dir: Collects names of files in a directory and returns vec of the names.

fn scan_dir(directory: &String) -> Vec<String> 

• collect_lib for each filename from the directory calls readelf -d command with the current file path to get the dynamic sym table. Parse the table, finds all occurrences of "Shared library:" and extract all names from libraries used in the file. Calls get_architecture function and collect all data into the vector of struct CollectorEntry

fn collect_lib<'a>(
    names: &Vec<String>,
    directory: &String,
    collector: &'a mut Vec<CollectorEntry>,
    recursive: &bool
)

More screenshots (for different architectures):

Results from hello_world! program on C for x86_64 and Aarch64:

Results for binary samples from https://github.com/JonathanSalwan/binary-samples