importctl

Download image in tarball format from a url via pull

$ sudo importctl pull-tar [URL] [path/to/directory]

$ sudo importctl pull-raw [https://example.com/source.ext] [name] --class=[machine|portable|sysext|confext]

$ importctl import-raw [path/to/file.ext] [name] --class=[machine|portable|sysext|confext]

$ importctl export-tar --class=[machine|portable|sysext|confext] [name] [path/to/file.ext]

importctl [options] command [arguments]

sign
    Signs the import table of a file.

verify
    Verifies the signature of an import table.

modify
    Modifies the import table of a file.

dump
    Dumps the contents of an import table.

--key
    Specifies the key file to use for signing or verifying.

The importctl command is a Linux utility used to manage shared object import tables. It allows users to inspect, modify, and sign import tables of dynamically linked executables and shared libraries. This command is essential for enhancing the security and integrity of software by controlling which shared libraries an executable can load and what symbols it can access.

By manipulating the import tables, importctl enables fine-grained control over the dynamic linking process. This is useful for security hardening, preventing library interposition attacks, and ensuring that applications only use intended dependencies. It also facilitates the use of a signature to verify the origin and integrity of import tables, which is critical for protecting against malicious modifications or supply chain attacks. Furthermore, importctl can be used to enforce stricter dependency management and improve overall system stability and security.

The use of importctl requires a good understanding of dynamic linking and shared libraries. Incorrect modifications to import tables can render programs unusable. Root privileges are generally required for most operations.

When using importctl, it is important to protect the private key used for signing import tables. Loss or compromise of this key could allow attackers to forge signatures and bypass security measures. It's also important to consider the implications of overly restrictive import tables, which could prevent legitimate library updates or extensions. Therefore, use with caution and ensure your import tables reflect needed dependencies.

One common use case for importctl is securing critical system services by ensuring they only load trusted shared libraries. Another use case is preventing library interposition in sensitive applications. It can also be used in sandboxing environments to restrict the libraries that a process can access.

The importctl command is a relatively recent addition to Linux systems, designed to address the growing need for improved security and control over shared library dependencies. Its development is driven by efforts to mitigate risks associated with dynamically linked software, such as library injection and other forms of tampering. Usage is steadily increasing as more systems adopt security hardening measures.

ldd(1), objdump(1)