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6.6. Pemeriksaan Otentikasi Paket

Keamanan merupakan hal yang sangat penting untuk administrator Falcot Corp. Maka, mereka perlu memastikan baha mereka hanya menginstall paket yang dijamin datang dari Debian dengan tanpa pemadatan. Seorang cracker komputer dapat mencoba untuk menambahkan kode jahat pada selain paket sah. Semacam paket, jika terinstall, dapat melakukan apapun yang didesain cracker untuk melakukannya, termasuk misalnya membongkar password atau informasi rahasia. Untuk menghindari resiko ini, Debian menyediakan sebuah bukti-padat segel untuk menjamin - pada saat instalasi - bahwa sebuah paket datang dari maintainer resminya dan belum dimodifikasi oleh pihak ketiga.
The seal works with a chain of cryptographical hashes and a signature and is explained in detail in apt-secure(8). Starting with Debian 10 Buster the signed file is the InRelease file, provided by the Debian mirrors. There is also a legacy file called Release. Both contain a list of the Packages files (including their compressed forms, Packages.gz and Packages.xz, and the incremental versions), along with their SHA256 hashes, which ensures that the files haven't been tampered with. These Packages files contain a list of the Debian packages available on the mirror, along with their hashes, which ensures in turn that the contents of the packages themselves haven't been altered either. The difference between InRelease and Release is that the former is cryptographically signed in-line, whereas the latter provides a detached signature in the form of the file Release.gpg.
APT needs a set of trusted GnuPG public keys to verify signatures in the InRelease and Release.gpg files available on the mirrors. It gets them from files in /etc/apt/trusted.gpg.d/ and from the /etc/apt/trusted.gpg keyring (managed by the apt-key command). The official Debian keys are provided and kept up-to-date by the debian-archive-keyring package which puts them in /etc/apt/trusted.gpg.d/:
# ls /etc/apt/trusted.gpg.d/
debian-archive-bullseye-automatic.gpg
debian-archive-bullseye-security-automatic.gpg
debian-archive-bullseye-stable.gpg
debian-archive-buster-automatic.gpg
debian-archive-buster-security-automatic.gpg
debian-archive-buster-stable.gpg
debian-archive-stretch-automatic.gpg
debian-archive-stretch-security-automatic.gpg
debian-archive-stretch-stable.gpg
Once the appropriate keys are in the keyring, APT will check the signatures before any risky operation, so that frontends will display a warning if asked to install a package whose authenticity can't be ascertained.
Note, that binary packages are usually not signed. The integrity of a package can only be confirmed by checking its hashsums against a trusted (and possibly signed) hashsum source.