LFCS · Question #489
Why is /etc/shadow not world readable if the passwords are stored in an encrypted fashion?
The correct answer is A. The encrypted passwords are still subject to brute force attacks. The /etc/shadow file is not world-readable because even though passwords are cryptographically hashed, these hashes are still vulnerable to offline brute-force or dictionary attacks if exposed.
Question
Options
- AThe encrypted passwords are still subject to brute force attacks.
- BThis is just for historical reasons.
- CThere is other information in the file that needs to be kept secret.
- DThe passwords can be decrypted by anyone with root access.
How the community answered
(49 responses)- A88% (43)
- B4% (2)
- C2% (1)
- D6% (3)
Why each option
The `/etc/shadow` file is not world-readable because even though passwords are cryptographically hashed, these hashes are still vulnerable to offline brute-force or dictionary attacks if exposed.
Even though passwords in `/etc/shadow` are stored as one-way cryptographic hashes, making the file world-readable would expose these hashes to any user on the system. This exposure would allow attackers to perform offline brute-force or dictionary attacks using specialized tools, attempting to guess the original password from its hash without needing to interact with the system's authentication process.
The restricted permissions on `/etc/shadow` are a direct security measure against password cracking, not merely a historical remnant.
While `/etc/shadow` contains other sensitive information like password aging details, the primary and most critical reason for its restricted access is the protection of password hashes from cracking attempts.
Passwords stored in `/etc/shadow` are hashed, not encrypted, meaning they cannot be "decrypted" back to their original plaintext form by anyone, including root. Root can change passwords, but not reverse hashes.
Concept tested: /etc/shadow security principles
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